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2800.3 P438 -158-R 2/05-1/08 FINAL PERFORMANCE REPORT State: Oklahoma Grant Number: W-158-R Grant Program: Wildlife Restoration Grant Title: Status and population characteristics of the northern river otter (Lontra canadensis) in central and eastern Oklahoma Grant Period: February 1, 2005 - January 31, 2008 Report Period: February 1. 2007 - January 31, 2008 Project Leader: David M. Leslie Objective: To evaluate current distribution and population status of the northern river otter where they have been reportedly observed in the past 20 years, mamly in central and eastern Oklahoma. Summary of Progress: Attached Master's Thesis serves as our final report. Prepared by: Dominic Barrett Date: March 31, 2008 Approved by: Wildlife Division Admini ation Oklahoma Department of Wildlife Conservation J D. Staford ed ral Aid Coordinator ahoma Department of Wildlife Conservation STATUS AND POPULATION CHARACTERISTICS OF THE NORTHERN RIVER OTTER (LONTRA CANADENSIS) IN CENTRAL AND EASTERN OKLAHOMA Thesis Approved: David M. Leslie, Jr. Thesis Advisor Craig A. Davis William L. Fisher A. Gordon Emslie Dean ofthe Graduate College ii ACKNOWLEDGMENTS Funding for this research was provided by the Federal Aid, Pittman-Robertson Wildlife Restoration Act under Project W-158-R of the Oklahoma Department of Wildlife Conservation and Oklahoma State University. The project was administered through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma Department of Wildlife Conservation, United States Geological Survey, Oklahoma State University, Wildlife Management Institute, and United States Fish and Wildlife Service cooperating). This research was partially supported by the National Science Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under grant number HRD-0444082. In addition to financial contributors, I would like to thank my family and friends for always supporting me. Without them, I am not sure I would have continued my path and conquered the obstacles placed before me. I thank my Dad for introducing me to the outdoors and showing me a great appreciation for everything natural. I thank my Mom for her friendship and willingness to listen no matter what the circumstance. Thank you to Stacey K. Davis and Ashley A. Foster for their assistance in the field and many hours of humorous conversation. I thank Dave Hamilton from the Missouri Department of Conservation and Mike Fischer from the Arkansas Trappers Association, for introducing me to the "fine art" of tracking and trapping river otters. I also thank numerous private land owners across eastern Oklahoma for allowing me access. I especially thank Mildred (Mig) Hamilton and Roger Canada for their iii hospitality and generosity. I thank several employees from the Oklahoma Department of Wildlife Conservation and United States Fish and Wildlife Service for their aid in pursuing such an intimidating task. I want to thank Sheryl Lyon, Joyce Hufford, and Judy Gray for their assistance. Last but not least, I would like to thank my committee members, Craig A. Davis and William L. Fisher, for their support and guidance. In particular, I appreciate my advisor, David (Chip) M. Leslie, Jr., for providing me this opportunity, constant encouragement, inspiration, and an open door. I thank you all for your time and efforts. IV TABLE OF CONTENTS Chapter Page 1. CURRENT DISTRIBUTION OF AN EXPANDING RIVER OTTER (LONTRA CANADENSIS) POPULATION Abstract. 1 Introduction 2 Materials and Methods 5 Results 11 Discussion 14 Acknowledgments 18 Literature Cited 19 Tables 33 Figures 34 2. SPA TIOTEMPORAL AGE STRUCTURES AND POPULATION CHARACTERISTICS OF A PARTIALLY REESTABLISHED RIVER OTTER (LONTRA CANADENSIS) POPULATION Abstract. 37 Introduction 38 Materials and Methods 42 Results 48 Discussion 51 Acknowledgments 60 v Literature Cited 61 Tables 75 Figures 78 APPENDIX 85 vi LIST OF TABLES Table Page Chapter I 1. River otter mail survey statistics based upon return rates of individual groups of survey participants (2006). . 33 Chapter II 1. Comparison of the percentage of juveniles and adults in river otter populations by state or province (adapted from Gallagher 1999 and Polechla 1987) 75 2. Isotopic signatures of river otter liver (n = 24), muscle (n = 25), toenail (n = 49), and teeth (n = 52; 2005-2007); samples categorized by trap site (pre- and post-1996 counties) 76 3. Isotopic signatures of river otter toenail (n = 49) and teeth (n = 48; 2005- 2007); samples categorized by watershed (Illinois River Watershed [ILRW], n = 13,8; Arkansas River Watershed [ARRW], n = 12, 18; Canadian River Watershed [CRW], n = 4,6; and Red River Watershed [RRW], n = 20, 16) 77 VII LIST OF FIGURES Figure Page Chapter I 1. Watersheds and their percentages of positive sites for river otters during sign surveys, winter and spring, 2006-2007 .34 2. Changing occurrence of river otters in Oklahoma counties, through 2007..... .35 3. Oklahoma counties where river otters have been captured by USDA Animal and Plant Health Inspection Service employees; year within each county (1991-2007) represents first year of capture. . 36 Chapter II 1. Oklahoma counties where river otters have been captured by USDA Animal and Plant Health Inspection Service employees; year within each county (1991-2007) represents first year of capture. . 78 2. River otter capture sites (n = 58) within pre- (empty circles) and post-1996 (shaded circles) counties (2005-2007) 79 3. River otter capture sites from the Arkansas River and its tributaries and within, A) 70, 140, and 210 km, and B) 100 and 200 km of Arkansas state border (2005-2007). . 80 4. River otter capture sites within 4 watersheds in eastern Oklahoma (2005-2007). . 81 5. Age distribution of river otters captured by USDA APHIS and OKCFWRU in Oklahoma and collected by ODWC employees (2005- 2007) 82 6. Age distribution of river otters captured in pre- and post-1996 counties in eastern Oklahoma (2005-2007) 83 7. Relationship between mean and age years since initial capture of river otters in Oklahoma, 1991-2007 84 viii APPENDICES Appendix Page A. Mail survey and distributional questionnaire (2005). . 85 B. Institutional Review Board letter and approval form. . 88 C. Locations of sign survey sites visited in winter and spring 2006 and 2007; river otters and/or sign was recorded as present (P) or absent (A) and sites that did not contain water were not searched (NW). . 89 D. Watersheds of eastern Oklahoma 104 E. River otter death report (2005). . 105 F. Stable istotope signatures (813C, 815N) of river otter liver, muscle, toenail, and teeth from pre- and post-1996 counties (2005-2007). . 107 G. Stable isotope signatures (813C, 81~) of river otter toenails and teeth from 4 watersheds (Illinois River Watershed [ILRW], Arkansas River Watershed [ARRW], Canadian River Watershed [CRW], Red River Watershed [RRW]) in eastern Oklahoma (2005-2007) 111 H. River otter capture data from eastern Oklahoma (2006, 2007). . .1-13 I. Comparison of capture data (catch per unit effort) by state 114 IX CHAPTER I DISTRIBUTION OF AN EXPANDING RIVER OTTER (LONTRA CANADENSIS) POPULATION ABSTRACT In 1984 and 1985, the Oklahoma Department of Wildlife Conservation reintroduced northern river otters (Lontra canadensis) in eastern Oklahoma. As a result of reintroduction efforts and immigration from Arkansas, river otters have become reestablished throughout eastern Oklahoma. In the past, distributional data have been limited to incidental harvest by state and federal trappers and roadkills collected opportunistically. Our goal was to determine the precise distribution of river otters in Oklahoma via sign surveys and mail surveys. During winter and spring of 2006 and 2007, we visited 340 bridge sites within 28 different watersheds and identified river otter signs in 11 counties where river otters were not previously documented. Approximately 300 (27%) mail surveys were returned by state and federal natural resource employees, private organizations, and professional and recreational trappers. Mail surveys revealed the possibility of river otters occurring in 8 additional counties where they were not documented previously by published literature, USDA Animal and Plant Health Inspection Service records, or by sign survey efforts. Key words: distribution, Lontra canadensis, mail survey, northern river otter, sign survey, sightings, track survey INTRODUCTION Prior to European settlement and westward expansion, northern river otters (Lontra canadensis; hereafter "river otter") inhabited much ofthe U.S. and were found in all major rivers of North America (Anderson 1977; Hall 1981). River otters were documented throughout Oklahoma except in the Panhandle (Duck and Fletcher 1944). However, because of habitat destruction, human settlement, unregulated harvest, and water pollution, river otter populations became severely depleted or extirpated in much of their historic range by the early 1900s (Toweil and Tabor 1982; Jenkins 1983; Lariviere and Walton 1998). River otters were extirpated in 7 states and severely depleted in 9 other states including Oklahoma (Raesly 2001; Melquist et al. 2003). As a result, river otters have been protected by Oklahoma state law since 1917. Between 1917 and 1971, there were only 4 documented accounts of river otters in Oklahoma (Hatcher 1984). Due to habitat improvement, construction of reservoirs, wetland restoration, recent reintroduction efforts, and management, river otters have returned to 90% of their historical range in the U.S. (Melquist et al. 2003). Moreover, increases in populations of 2 beaver (Castor canadensis) and associated creation of wetland habitats across the u.s. provide river otters additional habitat in areas with limited resources (Jenkins 1983; Swimley et al. 1999). Habitat use by river otters is partially contingent upon shelter availability (Reid et al. 1994); river otters do not excavate their own dens (Melquist et al. 2003) and often occupy beaver lodges and bank dens (Melquist and Hornocker 1983). Within Oklahoma, about 250,000 ponds and 145 major reservoirs have been constructed since the 1930s (Schackelford and Whitaker 1997). In addition, >130 wetlands in Oklahoma have been restored by the Wetland Reserve Program ofthe U.S. Department of Agriculture (USDA) Natural Resource Conservation Service and in cooperation with other agencies (S. Tully, pers. comm. 2005). Ponds (Reid et al. 1988), reservoirs (Sheldon and Toll 1964), and restored wetlands (Polechla 1987; Newman and Griffin 1994) provide additional habitat for river otters. In 1984 and 1985, the Oklahoma Department of Wildlife Conservation (ODWC) released 10 river otters at Wister Wildlife Management Area (WMA) in Leflore County and 7 river otters at McGee Creek WMA in Atoka County (Base 1986); all translocated river otters were purchased in coastal Louisiana (Bayou Otter Farm, Theriot, Louisiana, USA). During a 2-year period throughout the mid-to-Iate 1990s, 22 river otters were released at the Wichita Mountains Wildlife Refuge (WMWR) in Comanche County. Six river otters reintroduced to WMNWR were obtained from Louisiana (Bayou Otter Farm); the remaining 16 were captured by USDA Animal and Plant Health Inspection Service (APHIS) employees near Tahlequah, Oklahoma (R. Smith, ODWC, pers. comm. 2005). Since the mid-1970s, river otter numbers in Oklahoma have increased probably due to immigration from increasing populations in Arkansas (Hatcher 1984) and relocation 3 efforts within Oklahoma. Dispersing river otters can move up to 42 km in 1 day (Melquist and Hornocker 1983). Base (1986) reported that accidental trappings and observations of river otters commonly occurred along the Fouche Maline, lower Arkansas River tributaries, Mountain Fork, Poteau River, and Sans Bois Creek in southeastern Oklahoma. In general, the annual number of river otters accidentally captured in Oklahoma by APHIS employees pursuing beavers (Castor canadensis) has increased (J. Steuber, pers. comm. 2005). Oklahoma has 126,459 km of streams and rivers, 18,686 km of shoreline, and 290,078 ha of surface water (http://www.owrb.ok..gov/util/waterfact.php, accessed 5 January 2008). Because river otters are capable of occupying many different aquatic environments (Mech 2002; Melquist et al. 2003), it is likely that many of Oklahoma's water bodies are suitable otter habitat and capable of sustaining river otter populations (Caire et al. 1989). However, no formal study has been conducted to assess contemporary distribution of river otters in Oklahoma. Shackelford and Whitaker (1997) examined habitat and relative abundance of river otters in the Little River, Poteau River, and Sans Bois Creek drainages in southeastern Oklahoma. Determining distribution is a fundamental part of conservation planning, and Macdonald (1990) noted that field surveys are an essential tool in designing conservation programs for otters. We used mail surveys and sign surveys to examine river otter distribution in Oklahoma. During winter and spring 2006 and 2007, we conducted river otter sign surveys throughout 28 watersheds in eastern and central Oklahoma. Mail surveys were sent to state and federal natural resource employees, private organizations, and private and professional trappers in 2006. 4 MATERlALS AND METHODS River otters are difficult to observe because they are generally nocturnal (Melquist and Hornocker 1983) and occur at low densities (Melquist and Hornocker 1983; Foy 1984; Shirley et al. 1988). Most researchers recommend using> 1 method to monitor river otters (Melquist and Dronkert 1987; Chilelli et al. 1998; Gallagher 1999). Methods used by researchers to examine otter (Lutrinae) distribution and other parameters (e.g., density) have included carcass collection (Polechla 1987; Gallagher 1999), fecal DNA analysis (Dallas et al. 2003; Hansen 2004; Hung et al. 2004), infrared technology (Garcia de Leaniz et al. 2006), population models (Hamilton 1998; Gallagher 1999; Woolf and Nielson 2001), radiotelemetry studies (Reid et al. 1994; Sjoasen 1997; Durbin 1998; Perrin and Carranza 2000), and radiotracer implants (Shirley et al. 1988; Testa et al. 1994). Indirect methods used to examine river otters include sign surveys (Robson 1982; Zackheim 1982; Foy 1984; Karnes and Tumlison 1984; Clark et al. 1987; Eccles 1989; Mack et al. 1994; Shackelford and Whitaker 1997; Gallagher 1999; Bischof2003; Bluett et al. 2004), aerial snow-track surveys (Reid et al. 1987; St-Georges 1995), scent-station indices (Humphrey and Zinn 1982; Robson and Humphrey 1985; Clark et al. 1987), latrine-site surveys (Karnes and Tumlison 1984; Newman and Griffin 1994), otter harvest surveys (Chilelli et al. 1996; Gallagher 1999; Scognamillo 2005), and mail surveys inquiring about distributional and status information (Zackheim 1982; Blumberg 1993; Kiesow 2003). Sign surveys are more cost-effective and likely to detect otter presence than scent-station surveys (Robson and Humphrey 1985; Clark et al. 1987; Eccles 1989). 5 North American river otters have been described as an "ecological equivalent" to Eurasian otters (Lutra lutra; Chanin 1985), and researchers outside of North America and Europe have used sign surveys to examine other species of otter (Lutrinae; Chehebar 1985; Lee 1996). Studies involving documentation of otter signs (e.g., scat, tracks, latrines) are commonly used on other continents including Africa (Macdonald and Mason 1983a, 1984; Rowe-Rowe 1992; Carugati and Perrin 2006), Asia (Lee 1996; Anoop and Hussain 2004; Shenoy et al. 2006), Europe (Romanowski 2006; MacDonald et al. 2007; Prigioni et al. 2007; Sulkava and Luikko 2007), and South America (Chehebar 1985; Medina-Vogel et al. 2003). Within North America, documentation of river otter sign has been used to determine distribution (Chromanski and Fritzell 1982), habitat preferences (Dubuc et al. 1990; Newman and Griffin 1994), population size (Reid et al. 1987), and relative abundance (Shackelford and Whitaker 1997; Gallagher 1999). Sign surveys.-Sign surveys were conducted in the vicinity of bridges (Shackelford and Whitaker 1997), low-water crossings, and locations where flowing water was adjacent to roadways or access points (Lode 1993; Romanowski et al. 1996). Examining bridges does not affect chances of detecting river otter presence (Gallant 2007). Sign surveys were conducted in 28 watersheds in eastern and central Oklahoma on private, state, and federal lands. Riparian vegetation varied from native grasses along prairie streams to oak (Quercus)-hickory (Carya) dominated forest further east. Stream substrates ranged from clay to bedrock with more rocky substrates occurring in eastern areas. Using ArcMap 9.1 (Environmental Systems Research Institute, Inc., Redlands, California, USA), we selected sites along ~ 3rd order streams (Swimley et al. 1999; 6 Kiesow and Dieter 200S); sites were j, 8-16 km stream km apart (Shackelford and Whitaker 1997). Originally, sign surveys were conducted at::: 8 km intervals; however, to conserve time and increase efficiency, survey distance was increased to::: 16 km. Larger streams (i.e., streams with greater length and higher order) were given priority over smaller streams (Dubuc et al. 1990). Extremely large rivers (e.g., ::: s" order) that were canalized and lacked suitable latrine sites were not sampled (Romanowski et al. 1996). Bridge sites with steep banks >4So (Gallagher 1999) and:::: 16 stream km were not sampled (Shackelford and Whitaker 1997). Mean linear home ranges of reintroduced river otters in southeastern Oklahoma were> 16 km (Base 1986). Therefore, it is likely that a home range would overlap with 1-2 sample points (Chanin 2003). Sites within residential areas were not sampled. No sites were sampled within 3 days of measurable precipitation (> 0.2 em) or a high water event (Clark et al. 1987; Shackelford and Whitaker 1997), and each site was visited once. Because of time constraints and limited manpower, we were not able to visit sample sites twice. Sign surveys were conducted from January to May 2006 and January to June 2007 (Shirley et al. 1988; Gallagher 1999; Shackelford 1994) because river otter activity levels (corresponding with mating season) are greatest during winter (Foy 1984) and spring (Melquist and Hornocker 1983). Sign surveys were continued until June 2007 because record high precipitation and unusually high water levels prevented field work after that. Using USGS Real-Time Water Data (http://waterdata.usgs.gov/ok/nwis/rt), efforts were made to sample streams and rivers when discharge was between 2Sth and 7Sth percentile of that sampling date. We did not search sites where nonhydrophytic vegetation within or near the streambed was inundated or where no water was present. 7 We intensively searched both sides of streams for otter sign throughout 4 belt transects (Elmeros and Bussenius 2002) of 200 x 5 m upstream and downstream of each bridge, low-water crossing, or access point (Mason and Macdonald 1987; Shackelford 1994; Romanowski et al. 1996). Sites containing beaver bank dens and lodges (Swim ley et al. 1999; Karnes and Tumlison 1984), beaver scent mounds (Karnes and Tumlison 1984), points ofland (Dubuc et al. 1990; Newman and Griffin 1994; Swimley et al. 1998), isthmuses, mouths of perennial streams (Newman and Griffin 1994), logjams (Melquist and Hornocker 1983), elevated debris-covered banks (Karnes and Tumlison 1984), and islands (Mowbray et al. 1976; Swimley 1996) were examined closely because river otters prefer such areas for latrines. River otters deposit feces, anal sac secretions, and urine on latrine sites (Swimley 1996). Personnel conducting sign surveys were trained by experienced employees from the Missouri Department of Wildlife Conservation (Evans 2006). Presence or absence of river otters and first type of sign observed were recorded. Positive sites were identified as those where river otters were observed and/or sign was identified. Positive sites confirmed the presence of river otters in the searched area. We used Pearson's Chi-square analysis to examine differences in proportion of positive sites among watersheds (Fusillo et al. 2007). Analysis included completed watersheds and those that contained> 5 examined sites (n = 21). Latrines were defined by the presence of~ 1 scat. Regression analyses were used to evaluate the relationship between years since initial capture and the proportion of positive sites from each county. Channel habitat variables were recorded at each identified latrine site. Sample sites were given a detectability rating based on the proportion oftrackable substrate, such as exposed banks 8 and sandbars, and searchability (Gallagher 1999). Trackability was determined by visual estimation of the percentage oftrackable substrate and was compared between negative and positive sites using a 2-tailed t-test (n = 294). Number of suitable latrine sites at each sample location were recorded and compared between negative and positive sites using a 2-tailed t-test (n = 126). Search efforts at each sample site ended ifriver otters were observed or sign was detected; no efforts were made to quantify river otter sign because previous research did not find a correlation between numbers of scats and river otters (Jenkins and Burrows 1980; Kruuk et al. 1986). Investigating and quantifying only scat can be problematic (Gallant et al. 2007), but regions with mild climates and limited snow fall do not permit use of other methods (e.g., snow track surveys). All statistical tests were conducted using SYSTAT 10 for Windows (SPSS Inc., Chicago, Illinois) and were considered significant at P < 0.05. Mail surveys.-Although collection localities of museum specimens can be used to determine distribution, such methods can be inaccurate. For example, some species are underrepresented and are collected rarely (Hazard 1982; Blumberg 1993). Sighting information also can be used to provide further information. Human-based surveys seeking information on distribution and status of a species are often used and provide useful information when managing species at large spatial scales (Hubbard and Serfass 2004; Lindsey et al. 2004; Stubblefield and Shrestha 2007). Researchers have used mail surveys and questionnaires to examine distribution of river otters (Chromanski and Fritzell 1982; Zackheim 1982; Blumberg 1993; Mack et al. 1994; Kiesow 2003, Bluett et al. 2004) and other carnivores (Quinn 1995; Clark et al. 2002). Mail surveys are 9 inexpensive and efficient when obtaining distributional data throughout a large area (Sommer and Sommer 1991). We developed a mail survey questionnaire (Appendix A) to obtain information on distribution of river otters in Oklahoma (Oklahoma State University Institutional Review Board Application No. AS06l; Appendix B). Some questions were modified from Pike's (1997) survey on mountain lions (Puma concotor+ Pike et al. 1999). Survey recipients were asked to report river otter sightings and river otter sign that they observed during the last 5 years (2001-2005). Recipients also were asked to identify locations of sightings by placing a symbol on an enclosed map. Mail surveys (n = 1,153) were sent to state and federal biologists and technicians (ODWC, US Fish and Wildlife Service, USDA Forest Service), ODWC game wardens, USDA APHIS employees, US Army Corps of Engineers lake managers and park rangers, Nature Conservancy land stewards, and professional and recreational trappers. Mail surveys were also sent to professional and recreational trappers who purchased a trapping license in 2004-2005 and lived east ofInterstate 35. Survey groups were selected based on knowledge and interest in the subject. To increase participation, survey participants remained anonymous and were not asked to identify themselves. Pre-paid postage and pre-addressed return envelopes also were included with the survey (Blumberg 1993). Returned surveys were organized by employer or affiliation (Pike et al. 1999). Because we could not identify nonrespondants, a follow-up reminder was sent to all survey recipients approximately 2 months after initial mailing (Filion 1978). River otter "death reports" were mailed to ODWC regional biologists and game wardens that opportunistically collected carcasses. Death reports were designed to 10 acquire additional data on river otter distribution and facilitate specimen collection. Recipients were asked to report location (water body, town, county) and general habitat charactersistcs. APHIS employees conducting damage control associated with beaver activity also received "death reports." River otters are often harvested incidentally by trappers pursuing beavers (Gallagher 1999; Bischof2003) using non-selective Conibear 330 traps (Hill 1976). RESULTS Sign surveys.-We visited 340 riparian reaches throughout eastern and central Oklahoma (Appendix C, D), but 43 sites were not examined because water was not present. We observed river otters or identified river otter sign at 159 of297 (53.5%) of all examined sites. Of 159 positive sites, we observed river otters at 2 sites, identified tracks at 20 sites, and latrines at 137 sites. Proportion of positive sites within each watershed was 0-100% (Fig. 1). There was a significant difference (X2 = 123.81; df= 20; P < 0.001) in proportion of positive sites among completed watersheds. During the sign surveys, we identified river otter sign in 11 counties (Carter, Cleveland, Kay, Lincoln, Okfuskee, Osage, Ottawa, Pontotoc, Pottawatomie, Rogers, Tulsa; Fig. 2) where river otters have not been documented in published literature (Caire et al. 1989) or by APHIS records. Sign surveys documented river otter sign in all counties where they were captured by APHIS. Proportion of positive sites within each county were correlated positively (r2= 0.57; P < 0.05) with number of years of since initial capture. River otter sign was located along the Little River in Pottawatomie County off of US Route 177. Because the latrine occurred beyond the standard 200 m, the sample site 11 was considered negative. One latrine was identified opportunistically along the Arkansas River below Kaw Lake on the border between Kay and Osage counties. River otter signs also were identified opportunistically along the North Canadian River in Mcintosh and Okfuskee counties near Indian Nation Turnpike bridge. Two sites were searched opportunistically within the Lower Cimarron Watershed, but no river otter sign was documented. Middle Washita River and Muddy Boggy Creek watersheds were not completed because time constraints and high water levels. River otter sign was documented on Caddo Creek within the Middle Washita River Watershed (Carter County). River otter sign also was documented at 3 examined sites in the Muddy Boggy Creek Watershed. Elk River and Bois D'arc Creek-Island Bayou watersheds were not sampled. Because the majority ofthe Elk River Watershed occurs in western Arkansas, only one sample site was selected along the Elk River in Delaware County, Oklahoma, but it was not examined because water was not present. Bois D'arc Creek and Island Bayou Watershed, primarily in Bryan County, was not sampled because no suitable sample sites were located near bridges or access points. All streams within that watershed were small (i.e., < 1 m) or highly entrenched (i.e., >450 banks). Because streams and rivers tended to be more entrenched further west, we located fewer suitable sample sites and, therefore, examined fewer sites in western watersheds. Over 150 sites were removed from the sample because steep banks dominated the shoreline. Trackability of negative sites (X = 4.10) and positive sites (X = 3.23) differed (t = 3.81; P < 0.001). There was no difference (t = 1.79; P> 0.05) between number of suitable latrine sites located at negative and positive sites. Within positive sites, 56.5% of 12 river otter sign occurred within the first 100 m (X = 93.3 m). Less than 21% oflatrines occurred after 150 m. Most latrines (59.2%) were located within 50 m ofa transition between channel habitat variables. Of latrines occurring within 50 m of a stream habitat transition, approximately 75.6% occurred at a transition between pools (main channel, comer, lateral scour, and confluence) and other stream habitat types. Most commonly (74.6%), the transition occurred between pool and riffle (low and high gradient) habitats. Most latrines were located at the bankfull step (64.3%; Rosgen 1996) along straight shorelines (53.9%) with vertical (53.8%) or sloped (31.9%) banks. Latrines commonly occurred near slack water where detritus accumulated within the streambed (33.3%), areas inhabited by beavers (76.9%), and within 50 m of tributaries (21.2%). The mean stream width adjacent to latrines was 22.8 m. Mail surveys.- Twenty-seven percent of 1,153 mail surveys were returned. Return rates among surveyed groups were 0--46% (Table 1). Thirty-nine percent of all returned surveys reported observing river otters within the last 5 years (2001-2005). Twenty-eight percent of all returned surveys reported observing river otter sign within the last 5 years. Overall, the number of reported river otter sightings and observations of sign among all groups increased from 22 to 89 and 11 to 62, respectively, during the past 5 years. Survey participants reported river otters in 19 new counties (Fig. 2). State and federal wildlife employees reported river otters in 6 new counties (Cotton, Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). River otter death reports documented otters in 2 new counties (Okfuskee and Tulsa). Mail survey participants identified all counties where river otters were captured by APHIS employees except Creek and Seminole counties. Six new counties were reported by> 1 survey group (Carter, 13 Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). Locations of river otter sightings or observance of sign was similar among survey groups. Most sightings and/or signs occurred in localized areas (e.g., reservoirs) with high accessibility. Mail survey participants reported river otters throughout all counties identified by sign survey efforts. Combined, sign surveys and mail survey participants found river otters in 19 new individual counties (Fig. 2; Caire et al. 1989), and eight ofthose counties were not identified by sign surveys. DISCUSSION Mason and Macdonald (1987) noted a positive correlation (r2 = 0.84; P < 0.01) between the mean number of scats and the proportion of positive sites from each study area. Unlike others (Jenkins and Borrows 1980; Kruuk et al. 1986), Mason and Macdonald (1987) noted that scats can be used to make a broad comparison among populations. Nevertheless, the validity of using scats to determine otter (Lontra spp, Lutra spp.) occurrence is still debated (Gallantet al. 2007), but researchers throughout Europe continue to examine scats and proportions of positive sites to compare otter densities (Fusillo et al. 2007; MacDonald et al. 2007). Indirect signs are often effective tools to study wildlife species (Plumptre 2000; Sadlier et al. 2004; Stephens et al. 2006). However, caution should be used when interpreting river otter sign data (Rostain 2000; Gallagher 1999) because several factors can affect detection (Evans 2006, Fusillo et al. 2007); for instance, occupants could be outside of the sampled area but within its home range. Presence can often be determined, but absence can be impossible to determine (MacKenzie 2005). Others have reported 14 that there is not always a relationship between number of scats and number of river otters (Jenkins and Burrows 1980; Melquist and Hornocker 1983; Kruuk and Conroy 1987; Gallagher 1999; Gallant et al. 2007). Furthermore, sites with less scat could be an indication of fewer suitable latrine habitats (Romanowski et al. 1996). In contrast, we determined that no difference occurred between the number of suitable latrine sites at positive and negative sites. Because oftime constraints and high water levels, we did not sample Lower Canadian River and Walnut Creek and Lower North Canadian River watersheds. However, mail surveys, "death reports," and APHIS records documented river otters within both ofthese drainages. Sign surveys were conducted within the Little River Watershed, a tributary to the Canadian River in central Oklahoma. River otter sign was documented along the Little River in Pottawatomie County and below Lake Thunderbird in Cleveland County. To reach these locations, river otters must have used the Canadian River above Eufaula Lake. Within the Lower North Canadian River Watershed, we collected 1 river otter carcass and identified river otter signs above Eufaula Lake along the North Canadian River in McIntosh and Okfuskee counties. We examined 3 sites within the Muddy Boggy Creek Watershed that contained river otter sign. Most likely river otters have become well established throughout this watershed because reintroduction efforts (McGee Creek WMA), suitable habitats, and neighboring watersheds (Clear Boggy Creek Watershed, Kiamichi River Watershed) contained relatively high proportions of positive sites (Fig. 1). Mail surveys allowed us to obtain specific locations of river otters throughout Oklahoma and were relatively inexpensive and required less time and effort than sign 15 surveys; however, data should be interpreted cautiously. Previous researchers surveyed only natural resource employees because responses from outdoorsman were considered unreliable (Van Dyke and Brocke 1987; McBride et al. 1993; Pike et al. 1999). However, even natural resource professionals can be inaccurate when identifying animal sign unless properly trained (Evans 2006). Within our study, Chi-square analysis revealed that positive responses among surveyed groups (trappers, ODWC, federal employees) did not differ ("l = 1.17; df= 2; P> 0.10). Regardless of who is surveyed, researchers must account for issues regarding access; locations commonly visited by outdoorsman and areas not accessible could influence distributional data (Stubblefield and Shrestha 2007). Van Dyke and Brocke (1987) noted that human-based surveys should not be used alone to describe distribution of mountain lions; instead; such surveys should be used with other methods to determine spatial distribution. Mail survey information should only be used as estimates of mammal distribution (Blumberg 1993). Since the 1970s, river otters have become more prevalent throughout eastern Oklahoma and continued to spread westward, recolonizing parts of their historic range (Hatcher 1984; Base 1986). By 1992, APHIS employees reported catching river otters in 6 counties (Atoka, Haskell, Latimer, Leflore, McCurtain, Pushmataha) in southeastern Oklahoma. Illustrating westward movement, river otters were unintentionally captured in > 1 new county, on average, each year from 1991 to 2007 (Fig. 3), but the majority of annual incidental captures by APHIS employees came from southeastern Oklahoma. Currently, river otters have become well established and commonly occur throughout most of eastern Oklahoma. Although we documented river otters in central Oklahoma, it is unlikely that they occur at high densities throughout watersheds west of Blue River, 16 Clear Boggy Creek, and Lower Washita River watersheds and east ofWMNWR. Mail surveys and APHIS harvest records showed few accounts of river otters in central Oklahoma. Furthermore, sign surveys within Little River Watershed (central Oklahoma) showed relatively low proportions of sites containing river otter sign (29%). Similarly, 29% of examined sites along upper portions of the Deep Fork Watershed were positive. We suggest that no more than broad comparisons among large watersheds should be made from the proportion of positive sites within a watershed (Macdonald 1987) and management decisions should not be based solely on sign indices (Gallagher 1999). Most importantly, sign surveys should be used to monitor sample sites throughout time to document range expansion and/or reduction (Swimley and Hardisky 2000). Large reductions in population size may be more evident when baseline data have been recorded previously. Changes in scat frequency may be detectable only when otter populations have been impacted greatly (Jenkins and Burrows 1980; Mason and Macdonald 1987); for example, Lode (1993) used sign-surveys to document otter decline in France. Sign surveys were used to document range expansion and recolonization in Poland (Romanowski 2006). Other state wildlife agencies already use sign surveys to monitor river otter distributions (Boyd 2006, Evans 2006). Conducting systematic surveys is essential to species management and conservation throughout time (Elmeros and Bussenius 2002; Gallant 2007) and should be continued in Oklahoma. Within Oklahoma, relatively large watersheds such as Arkansas River, Canadian River, Red River, Cimarron River, and Washita River, follow a west-to-east pattern and facilitate westward dispersal and expansion of river otters. Studies using indirect sign to examine river otter populations should consider detectability and repeated 17 visits to determine river otter presence or absence (Royle and Nichols 2003; MacKenzie 2005). Observer skill should also be evaluated using standardized methods (Evans 2006). To achieve greater statistical power, the number of sites throughout each watershed should be increased. In locations where suitable latrine sites do not exist, European researchers have created artificial latrine sites to increase effectiveness of monitoring efforts (Chanin 2003). Chanin (2003) recommended that sign surveys should be conducted annually for 10 years, and then sampling should occur at intervals of2-3 years. Because sign surveys cannot detect annual fluctuations in river otter populations (Clark et al. 1987; Gallagher 1999), we recommend visiting sites biennially until variations (e.g., increase, decrease) cease. As baseline data and populations become established, sampling intervals can be repeated less frequently. ACKNOWLEDGMENTS Funding for this research was provided by the Federal Aid, Pittman-Robertson Wildlife Restoration Act under Project W-158-R ofthe Oklahoma Department of Wildlife Conservation and Oklahoma State University. The project was administered through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma Department of Wildlife Conservation, United States Geological Survey, Oklahoma State University, Wildlife Management Institute, and United States Fish and Wildlife Service cooperating). This publication was partially supported by the National Science Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under grant number HRD-0444082. We would like to thank S. K. Davis and A. A. Foster for their assistance in the field. A special thanks to D. Hamilton from the 18 Missouri Department of Wildlife Conservation and M. Fischer from the Arkansas Trappers Association for their guidance and training. We also thank R. Thornburg and S. Sheffert of the Oklahoma Fur Bearers Alliance for their insight and assistance. Numerous employees of the ODWC provided much needed assistance; we especially thank A. Crews for helping develop the river otter survey. We thank hundreds of state and federal employees and private and professional trappers who participated in the mail survey. We thank hundreds of landowners across eastern Oklahoma who allowed temporary access to their property. This project was completed as partial fulfillment for the requirements of the degree of Master of Science. LITERATURE CITED Anderson, S. 1977. Geographic ranges of North American terrestrial mammals. American Museum Novitates 2629:1-15. Anoop, K. R., and S. A. Hussain. 2004. Factors affecting habitat selection by smooth-coated otters (Lutra perspicillata) in Kerala, India. Journal of Zoology 263 :417- 423. Base, D. L. 1986. 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Title | Status and population characteristics of the northern river otter pt1 |
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Full text | 2800.3 P438 -158-R 2/05-1/08 FINAL PERFORMANCE REPORT State: Oklahoma Grant Number: W-158-R Grant Program: Wildlife Restoration Grant Title: Status and population characteristics of the northern river otter (Lontra canadensis) in central and eastern Oklahoma Grant Period: February 1, 2005 - January 31, 2008 Report Period: February 1. 2007 - January 31, 2008 Project Leader: David M. Leslie Objective: To evaluate current distribution and population status of the northern river otter where they have been reportedly observed in the past 20 years, mamly in central and eastern Oklahoma. Summary of Progress: Attached Master's Thesis serves as our final report. Prepared by: Dominic Barrett Date: March 31, 2008 Approved by: Wildlife Division Admini ation Oklahoma Department of Wildlife Conservation J D. Staford ed ral Aid Coordinator ahoma Department of Wildlife Conservation STATUS AND POPULATION CHARACTERISTICS OF THE NORTHERN RIVER OTTER (LONTRA CANADENSIS) IN CENTRAL AND EASTERN OKLAHOMA Thesis Approved: David M. Leslie, Jr. Thesis Advisor Craig A. Davis William L. Fisher A. Gordon Emslie Dean ofthe Graduate College ii ACKNOWLEDGMENTS Funding for this research was provided by the Federal Aid, Pittman-Robertson Wildlife Restoration Act under Project W-158-R of the Oklahoma Department of Wildlife Conservation and Oklahoma State University. The project was administered through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma Department of Wildlife Conservation, United States Geological Survey, Oklahoma State University, Wildlife Management Institute, and United States Fish and Wildlife Service cooperating). This research was partially supported by the National Science Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under grant number HRD-0444082. In addition to financial contributors, I would like to thank my family and friends for always supporting me. Without them, I am not sure I would have continued my path and conquered the obstacles placed before me. I thank my Dad for introducing me to the outdoors and showing me a great appreciation for everything natural. I thank my Mom for her friendship and willingness to listen no matter what the circumstance. Thank you to Stacey K. Davis and Ashley A. Foster for their assistance in the field and many hours of humorous conversation. I thank Dave Hamilton from the Missouri Department of Conservation and Mike Fischer from the Arkansas Trappers Association, for introducing me to the "fine art" of tracking and trapping river otters. I also thank numerous private land owners across eastern Oklahoma for allowing me access. I especially thank Mildred (Mig) Hamilton and Roger Canada for their iii hospitality and generosity. I thank several employees from the Oklahoma Department of Wildlife Conservation and United States Fish and Wildlife Service for their aid in pursuing such an intimidating task. I want to thank Sheryl Lyon, Joyce Hufford, and Judy Gray for their assistance. Last but not least, I would like to thank my committee members, Craig A. Davis and William L. Fisher, for their support and guidance. In particular, I appreciate my advisor, David (Chip) M. Leslie, Jr., for providing me this opportunity, constant encouragement, inspiration, and an open door. I thank you all for your time and efforts. IV TABLE OF CONTENTS Chapter Page 1. CURRENT DISTRIBUTION OF AN EXPANDING RIVER OTTER (LONTRA CANADENSIS) POPULATION Abstract. 1 Introduction 2 Materials and Methods 5 Results 11 Discussion 14 Acknowledgments 18 Literature Cited 19 Tables 33 Figures 34 2. SPA TIOTEMPORAL AGE STRUCTURES AND POPULATION CHARACTERISTICS OF A PARTIALLY REESTABLISHED RIVER OTTER (LONTRA CANADENSIS) POPULATION Abstract. 37 Introduction 38 Materials and Methods 42 Results 48 Discussion 51 Acknowledgments 60 v Literature Cited 61 Tables 75 Figures 78 APPENDIX 85 vi LIST OF TABLES Table Page Chapter I 1. River otter mail survey statistics based upon return rates of individual groups of survey participants (2006). . 33 Chapter II 1. Comparison of the percentage of juveniles and adults in river otter populations by state or province (adapted from Gallagher 1999 and Polechla 1987) 75 2. Isotopic signatures of river otter liver (n = 24), muscle (n = 25), toenail (n = 49), and teeth (n = 52; 2005-2007); samples categorized by trap site (pre- and post-1996 counties) 76 3. Isotopic signatures of river otter toenail (n = 49) and teeth (n = 48; 2005- 2007); samples categorized by watershed (Illinois River Watershed [ILRW], n = 13,8; Arkansas River Watershed [ARRW], n = 12, 18; Canadian River Watershed [CRW], n = 4,6; and Red River Watershed [RRW], n = 20, 16) 77 VII LIST OF FIGURES Figure Page Chapter I 1. Watersheds and their percentages of positive sites for river otters during sign surveys, winter and spring, 2006-2007 .34 2. Changing occurrence of river otters in Oklahoma counties, through 2007..... .35 3. Oklahoma counties where river otters have been captured by USDA Animal and Plant Health Inspection Service employees; year within each county (1991-2007) represents first year of capture. . 36 Chapter II 1. Oklahoma counties where river otters have been captured by USDA Animal and Plant Health Inspection Service employees; year within each county (1991-2007) represents first year of capture. . 78 2. River otter capture sites (n = 58) within pre- (empty circles) and post-1996 (shaded circles) counties (2005-2007) 79 3. River otter capture sites from the Arkansas River and its tributaries and within, A) 70, 140, and 210 km, and B) 100 and 200 km of Arkansas state border (2005-2007). . 80 4. River otter capture sites within 4 watersheds in eastern Oklahoma (2005-2007). . 81 5. Age distribution of river otters captured by USDA APHIS and OKCFWRU in Oklahoma and collected by ODWC employees (2005- 2007) 82 6. Age distribution of river otters captured in pre- and post-1996 counties in eastern Oklahoma (2005-2007) 83 7. Relationship between mean and age years since initial capture of river otters in Oklahoma, 1991-2007 84 viii APPENDICES Appendix Page A. Mail survey and distributional questionnaire (2005). . 85 B. Institutional Review Board letter and approval form. . 88 C. Locations of sign survey sites visited in winter and spring 2006 and 2007; river otters and/or sign was recorded as present (P) or absent (A) and sites that did not contain water were not searched (NW). . 89 D. Watersheds of eastern Oklahoma 104 E. River otter death report (2005). . 105 F. Stable istotope signatures (813C, 815N) of river otter liver, muscle, toenail, and teeth from pre- and post-1996 counties (2005-2007). . 107 G. Stable isotope signatures (813C, 81~) of river otter toenails and teeth from 4 watersheds (Illinois River Watershed [ILRW], Arkansas River Watershed [ARRW], Canadian River Watershed [CRW], Red River Watershed [RRW]) in eastern Oklahoma (2005-2007) 111 H. River otter capture data from eastern Oklahoma (2006, 2007). . .1-13 I. Comparison of capture data (catch per unit effort) by state 114 IX CHAPTER I DISTRIBUTION OF AN EXPANDING RIVER OTTER (LONTRA CANADENSIS) POPULATION ABSTRACT In 1984 and 1985, the Oklahoma Department of Wildlife Conservation reintroduced northern river otters (Lontra canadensis) in eastern Oklahoma. As a result of reintroduction efforts and immigration from Arkansas, river otters have become reestablished throughout eastern Oklahoma. In the past, distributional data have been limited to incidental harvest by state and federal trappers and roadkills collected opportunistically. Our goal was to determine the precise distribution of river otters in Oklahoma via sign surveys and mail surveys. During winter and spring of 2006 and 2007, we visited 340 bridge sites within 28 different watersheds and identified river otter signs in 11 counties where river otters were not previously documented. Approximately 300 (27%) mail surveys were returned by state and federal natural resource employees, private organizations, and professional and recreational trappers. Mail surveys revealed the possibility of river otters occurring in 8 additional counties where they were not documented previously by published literature, USDA Animal and Plant Health Inspection Service records, or by sign survey efforts. Key words: distribution, Lontra canadensis, mail survey, northern river otter, sign survey, sightings, track survey INTRODUCTION Prior to European settlement and westward expansion, northern river otters (Lontra canadensis; hereafter "river otter") inhabited much ofthe U.S. and were found in all major rivers of North America (Anderson 1977; Hall 1981). River otters were documented throughout Oklahoma except in the Panhandle (Duck and Fletcher 1944). However, because of habitat destruction, human settlement, unregulated harvest, and water pollution, river otter populations became severely depleted or extirpated in much of their historic range by the early 1900s (Toweil and Tabor 1982; Jenkins 1983; Lariviere and Walton 1998). River otters were extirpated in 7 states and severely depleted in 9 other states including Oklahoma (Raesly 2001; Melquist et al. 2003). As a result, river otters have been protected by Oklahoma state law since 1917. Between 1917 and 1971, there were only 4 documented accounts of river otters in Oklahoma (Hatcher 1984). Due to habitat improvement, construction of reservoirs, wetland restoration, recent reintroduction efforts, and management, river otters have returned to 90% of their historical range in the U.S. (Melquist et al. 2003). Moreover, increases in populations of 2 beaver (Castor canadensis) and associated creation of wetland habitats across the u.s. provide river otters additional habitat in areas with limited resources (Jenkins 1983; Swimley et al. 1999). Habitat use by river otters is partially contingent upon shelter availability (Reid et al. 1994); river otters do not excavate their own dens (Melquist et al. 2003) and often occupy beaver lodges and bank dens (Melquist and Hornocker 1983). Within Oklahoma, about 250,000 ponds and 145 major reservoirs have been constructed since the 1930s (Schackelford and Whitaker 1997). In addition, >130 wetlands in Oklahoma have been restored by the Wetland Reserve Program ofthe U.S. Department of Agriculture (USDA) Natural Resource Conservation Service and in cooperation with other agencies (S. Tully, pers. comm. 2005). Ponds (Reid et al. 1988), reservoirs (Sheldon and Toll 1964), and restored wetlands (Polechla 1987; Newman and Griffin 1994) provide additional habitat for river otters. In 1984 and 1985, the Oklahoma Department of Wildlife Conservation (ODWC) released 10 river otters at Wister Wildlife Management Area (WMA) in Leflore County and 7 river otters at McGee Creek WMA in Atoka County (Base 1986); all translocated river otters were purchased in coastal Louisiana (Bayou Otter Farm, Theriot, Louisiana, USA). During a 2-year period throughout the mid-to-Iate 1990s, 22 river otters were released at the Wichita Mountains Wildlife Refuge (WMWR) in Comanche County. Six river otters reintroduced to WMNWR were obtained from Louisiana (Bayou Otter Farm); the remaining 16 were captured by USDA Animal and Plant Health Inspection Service (APHIS) employees near Tahlequah, Oklahoma (R. Smith, ODWC, pers. comm. 2005). Since the mid-1970s, river otter numbers in Oklahoma have increased probably due to immigration from increasing populations in Arkansas (Hatcher 1984) and relocation 3 efforts within Oklahoma. Dispersing river otters can move up to 42 km in 1 day (Melquist and Hornocker 1983). Base (1986) reported that accidental trappings and observations of river otters commonly occurred along the Fouche Maline, lower Arkansas River tributaries, Mountain Fork, Poteau River, and Sans Bois Creek in southeastern Oklahoma. In general, the annual number of river otters accidentally captured in Oklahoma by APHIS employees pursuing beavers (Castor canadensis) has increased (J. Steuber, pers. comm. 2005). Oklahoma has 126,459 km of streams and rivers, 18,686 km of shoreline, and 290,078 ha of surface water (http://www.owrb.ok..gov/util/waterfact.php, accessed 5 January 2008). Because river otters are capable of occupying many different aquatic environments (Mech 2002; Melquist et al. 2003), it is likely that many of Oklahoma's water bodies are suitable otter habitat and capable of sustaining river otter populations (Caire et al. 1989). However, no formal study has been conducted to assess contemporary distribution of river otters in Oklahoma. Shackelford and Whitaker (1997) examined habitat and relative abundance of river otters in the Little River, Poteau River, and Sans Bois Creek drainages in southeastern Oklahoma. Determining distribution is a fundamental part of conservation planning, and Macdonald (1990) noted that field surveys are an essential tool in designing conservation programs for otters. We used mail surveys and sign surveys to examine river otter distribution in Oklahoma. During winter and spring 2006 and 2007, we conducted river otter sign surveys throughout 28 watersheds in eastern and central Oklahoma. Mail surveys were sent to state and federal natural resource employees, private organizations, and private and professional trappers in 2006. 4 MATERlALS AND METHODS River otters are difficult to observe because they are generally nocturnal (Melquist and Hornocker 1983) and occur at low densities (Melquist and Hornocker 1983; Foy 1984; Shirley et al. 1988). Most researchers recommend using> 1 method to monitor river otters (Melquist and Dronkert 1987; Chilelli et al. 1998; Gallagher 1999). Methods used by researchers to examine otter (Lutrinae) distribution and other parameters (e.g., density) have included carcass collection (Polechla 1987; Gallagher 1999), fecal DNA analysis (Dallas et al. 2003; Hansen 2004; Hung et al. 2004), infrared technology (Garcia de Leaniz et al. 2006), population models (Hamilton 1998; Gallagher 1999; Woolf and Nielson 2001), radiotelemetry studies (Reid et al. 1994; Sjoasen 1997; Durbin 1998; Perrin and Carranza 2000), and radiotracer implants (Shirley et al. 1988; Testa et al. 1994). Indirect methods used to examine river otters include sign surveys (Robson 1982; Zackheim 1982; Foy 1984; Karnes and Tumlison 1984; Clark et al. 1987; Eccles 1989; Mack et al. 1994; Shackelford and Whitaker 1997; Gallagher 1999; Bischof2003; Bluett et al. 2004), aerial snow-track surveys (Reid et al. 1987; St-Georges 1995), scent-station indices (Humphrey and Zinn 1982; Robson and Humphrey 1985; Clark et al. 1987), latrine-site surveys (Karnes and Tumlison 1984; Newman and Griffin 1994), otter harvest surveys (Chilelli et al. 1996; Gallagher 1999; Scognamillo 2005), and mail surveys inquiring about distributional and status information (Zackheim 1982; Blumberg 1993; Kiesow 2003). Sign surveys are more cost-effective and likely to detect otter presence than scent-station surveys (Robson and Humphrey 1985; Clark et al. 1987; Eccles 1989). 5 North American river otters have been described as an "ecological equivalent" to Eurasian otters (Lutra lutra; Chanin 1985), and researchers outside of North America and Europe have used sign surveys to examine other species of otter (Lutrinae; Chehebar 1985; Lee 1996). Studies involving documentation of otter signs (e.g., scat, tracks, latrines) are commonly used on other continents including Africa (Macdonald and Mason 1983a, 1984; Rowe-Rowe 1992; Carugati and Perrin 2006), Asia (Lee 1996; Anoop and Hussain 2004; Shenoy et al. 2006), Europe (Romanowski 2006; MacDonald et al. 2007; Prigioni et al. 2007; Sulkava and Luikko 2007), and South America (Chehebar 1985; Medina-Vogel et al. 2003). Within North America, documentation of river otter sign has been used to determine distribution (Chromanski and Fritzell 1982), habitat preferences (Dubuc et al. 1990; Newman and Griffin 1994), population size (Reid et al. 1987), and relative abundance (Shackelford and Whitaker 1997; Gallagher 1999). Sign surveys.-Sign surveys were conducted in the vicinity of bridges (Shackelford and Whitaker 1997), low-water crossings, and locations where flowing water was adjacent to roadways or access points (Lode 1993; Romanowski et al. 1996). Examining bridges does not affect chances of detecting river otter presence (Gallant 2007). Sign surveys were conducted in 28 watersheds in eastern and central Oklahoma on private, state, and federal lands. Riparian vegetation varied from native grasses along prairie streams to oak (Quercus)-hickory (Carya) dominated forest further east. Stream substrates ranged from clay to bedrock with more rocky substrates occurring in eastern areas. Using ArcMap 9.1 (Environmental Systems Research Institute, Inc., Redlands, California, USA), we selected sites along ~ 3rd order streams (Swimley et al. 1999; 6 Kiesow and Dieter 200S); sites were j, 8-16 km stream km apart (Shackelford and Whitaker 1997). Originally, sign surveys were conducted at::: 8 km intervals; however, to conserve time and increase efficiency, survey distance was increased to::: 16 km. Larger streams (i.e., streams with greater length and higher order) were given priority over smaller streams (Dubuc et al. 1990). Extremely large rivers (e.g., ::: s" order) that were canalized and lacked suitable latrine sites were not sampled (Romanowski et al. 1996). Bridge sites with steep banks >4So (Gallagher 1999) and:::: 16 stream km were not sampled (Shackelford and Whitaker 1997). Mean linear home ranges of reintroduced river otters in southeastern Oklahoma were> 16 km (Base 1986). Therefore, it is likely that a home range would overlap with 1-2 sample points (Chanin 2003). Sites within residential areas were not sampled. No sites were sampled within 3 days of measurable precipitation (> 0.2 em) or a high water event (Clark et al. 1987; Shackelford and Whitaker 1997), and each site was visited once. Because of time constraints and limited manpower, we were not able to visit sample sites twice. Sign surveys were conducted from January to May 2006 and January to June 2007 (Shirley et al. 1988; Gallagher 1999; Shackelford 1994) because river otter activity levels (corresponding with mating season) are greatest during winter (Foy 1984) and spring (Melquist and Hornocker 1983). Sign surveys were continued until June 2007 because record high precipitation and unusually high water levels prevented field work after that. Using USGS Real-Time Water Data (http://waterdata.usgs.gov/ok/nwis/rt), efforts were made to sample streams and rivers when discharge was between 2Sth and 7Sth percentile of that sampling date. We did not search sites where nonhydrophytic vegetation within or near the streambed was inundated or where no water was present. 7 We intensively searched both sides of streams for otter sign throughout 4 belt transects (Elmeros and Bussenius 2002) of 200 x 5 m upstream and downstream of each bridge, low-water crossing, or access point (Mason and Macdonald 1987; Shackelford 1994; Romanowski et al. 1996). Sites containing beaver bank dens and lodges (Swim ley et al. 1999; Karnes and Tumlison 1984), beaver scent mounds (Karnes and Tumlison 1984), points ofland (Dubuc et al. 1990; Newman and Griffin 1994; Swimley et al. 1998), isthmuses, mouths of perennial streams (Newman and Griffin 1994), logjams (Melquist and Hornocker 1983), elevated debris-covered banks (Karnes and Tumlison 1984), and islands (Mowbray et al. 1976; Swimley 1996) were examined closely because river otters prefer such areas for latrines. River otters deposit feces, anal sac secretions, and urine on latrine sites (Swimley 1996). Personnel conducting sign surveys were trained by experienced employees from the Missouri Department of Wildlife Conservation (Evans 2006). Presence or absence of river otters and first type of sign observed were recorded. Positive sites were identified as those where river otters were observed and/or sign was identified. Positive sites confirmed the presence of river otters in the searched area. We used Pearson's Chi-square analysis to examine differences in proportion of positive sites among watersheds (Fusillo et al. 2007). Analysis included completed watersheds and those that contained> 5 examined sites (n = 21). Latrines were defined by the presence of~ 1 scat. Regression analyses were used to evaluate the relationship between years since initial capture and the proportion of positive sites from each county. Channel habitat variables were recorded at each identified latrine site. Sample sites were given a detectability rating based on the proportion oftrackable substrate, such as exposed banks 8 and sandbars, and searchability (Gallagher 1999). Trackability was determined by visual estimation of the percentage oftrackable substrate and was compared between negative and positive sites using a 2-tailed t-test (n = 294). Number of suitable latrine sites at each sample location were recorded and compared between negative and positive sites using a 2-tailed t-test (n = 126). Search efforts at each sample site ended ifriver otters were observed or sign was detected; no efforts were made to quantify river otter sign because previous research did not find a correlation between numbers of scats and river otters (Jenkins and Burrows 1980; Kruuk et al. 1986). Investigating and quantifying only scat can be problematic (Gallant et al. 2007), but regions with mild climates and limited snow fall do not permit use of other methods (e.g., snow track surveys). All statistical tests were conducted using SYSTAT 10 for Windows (SPSS Inc., Chicago, Illinois) and were considered significant at P < 0.05. Mail surveys.-Although collection localities of museum specimens can be used to determine distribution, such methods can be inaccurate. For example, some species are underrepresented and are collected rarely (Hazard 1982; Blumberg 1993). Sighting information also can be used to provide further information. Human-based surveys seeking information on distribution and status of a species are often used and provide useful information when managing species at large spatial scales (Hubbard and Serfass 2004; Lindsey et al. 2004; Stubblefield and Shrestha 2007). Researchers have used mail surveys and questionnaires to examine distribution of river otters (Chromanski and Fritzell 1982; Zackheim 1982; Blumberg 1993; Mack et al. 1994; Kiesow 2003, Bluett et al. 2004) and other carnivores (Quinn 1995; Clark et al. 2002). Mail surveys are 9 inexpensive and efficient when obtaining distributional data throughout a large area (Sommer and Sommer 1991). We developed a mail survey questionnaire (Appendix A) to obtain information on distribution of river otters in Oklahoma (Oklahoma State University Institutional Review Board Application No. AS06l; Appendix B). Some questions were modified from Pike's (1997) survey on mountain lions (Puma concotor+ Pike et al. 1999). Survey recipients were asked to report river otter sightings and river otter sign that they observed during the last 5 years (2001-2005). Recipients also were asked to identify locations of sightings by placing a symbol on an enclosed map. Mail surveys (n = 1,153) were sent to state and federal biologists and technicians (ODWC, US Fish and Wildlife Service, USDA Forest Service), ODWC game wardens, USDA APHIS employees, US Army Corps of Engineers lake managers and park rangers, Nature Conservancy land stewards, and professional and recreational trappers. Mail surveys were also sent to professional and recreational trappers who purchased a trapping license in 2004-2005 and lived east ofInterstate 35. Survey groups were selected based on knowledge and interest in the subject. To increase participation, survey participants remained anonymous and were not asked to identify themselves. Pre-paid postage and pre-addressed return envelopes also were included with the survey (Blumberg 1993). Returned surveys were organized by employer or affiliation (Pike et al. 1999). Because we could not identify nonrespondants, a follow-up reminder was sent to all survey recipients approximately 2 months after initial mailing (Filion 1978). River otter "death reports" were mailed to ODWC regional biologists and game wardens that opportunistically collected carcasses. Death reports were designed to 10 acquire additional data on river otter distribution and facilitate specimen collection. Recipients were asked to report location (water body, town, county) and general habitat charactersistcs. APHIS employees conducting damage control associated with beaver activity also received "death reports." River otters are often harvested incidentally by trappers pursuing beavers (Gallagher 1999; Bischof2003) using non-selective Conibear 330 traps (Hill 1976). RESULTS Sign surveys.-We visited 340 riparian reaches throughout eastern and central Oklahoma (Appendix C, D), but 43 sites were not examined because water was not present. We observed river otters or identified river otter sign at 159 of297 (53.5%) of all examined sites. Of 159 positive sites, we observed river otters at 2 sites, identified tracks at 20 sites, and latrines at 137 sites. Proportion of positive sites within each watershed was 0-100% (Fig. 1). There was a significant difference (X2 = 123.81; df= 20; P < 0.001) in proportion of positive sites among completed watersheds. During the sign surveys, we identified river otter sign in 11 counties (Carter, Cleveland, Kay, Lincoln, Okfuskee, Osage, Ottawa, Pontotoc, Pottawatomie, Rogers, Tulsa; Fig. 2) where river otters have not been documented in published literature (Caire et al. 1989) or by APHIS records. Sign surveys documented river otter sign in all counties where they were captured by APHIS. Proportion of positive sites within each county were correlated positively (r2= 0.57; P < 0.05) with number of years of since initial capture. River otter sign was located along the Little River in Pottawatomie County off of US Route 177. Because the latrine occurred beyond the standard 200 m, the sample site 11 was considered negative. One latrine was identified opportunistically along the Arkansas River below Kaw Lake on the border between Kay and Osage counties. River otter signs also were identified opportunistically along the North Canadian River in Mcintosh and Okfuskee counties near Indian Nation Turnpike bridge. Two sites were searched opportunistically within the Lower Cimarron Watershed, but no river otter sign was documented. Middle Washita River and Muddy Boggy Creek watersheds were not completed because time constraints and high water levels. River otter sign was documented on Caddo Creek within the Middle Washita River Watershed (Carter County). River otter sign also was documented at 3 examined sites in the Muddy Boggy Creek Watershed. Elk River and Bois D'arc Creek-Island Bayou watersheds were not sampled. Because the majority ofthe Elk River Watershed occurs in western Arkansas, only one sample site was selected along the Elk River in Delaware County, Oklahoma, but it was not examined because water was not present. Bois D'arc Creek and Island Bayou Watershed, primarily in Bryan County, was not sampled because no suitable sample sites were located near bridges or access points. All streams within that watershed were small (i.e., < 1 m) or highly entrenched (i.e., >450 banks). Because streams and rivers tended to be more entrenched further west, we located fewer suitable sample sites and, therefore, examined fewer sites in western watersheds. Over 150 sites were removed from the sample because steep banks dominated the shoreline. Trackability of negative sites (X = 4.10) and positive sites (X = 3.23) differed (t = 3.81; P < 0.001). There was no difference (t = 1.79; P> 0.05) between number of suitable latrine sites located at negative and positive sites. Within positive sites, 56.5% of 12 river otter sign occurred within the first 100 m (X = 93.3 m). Less than 21% oflatrines occurred after 150 m. Most latrines (59.2%) were located within 50 m ofa transition between channel habitat variables. Of latrines occurring within 50 m of a stream habitat transition, approximately 75.6% occurred at a transition between pools (main channel, comer, lateral scour, and confluence) and other stream habitat types. Most commonly (74.6%), the transition occurred between pool and riffle (low and high gradient) habitats. Most latrines were located at the bankfull step (64.3%; Rosgen 1996) along straight shorelines (53.9%) with vertical (53.8%) or sloped (31.9%) banks. Latrines commonly occurred near slack water where detritus accumulated within the streambed (33.3%), areas inhabited by beavers (76.9%), and within 50 m of tributaries (21.2%). The mean stream width adjacent to latrines was 22.8 m. Mail surveys.- Twenty-seven percent of 1,153 mail surveys were returned. Return rates among surveyed groups were 0--46% (Table 1). Thirty-nine percent of all returned surveys reported observing river otters within the last 5 years (2001-2005). Twenty-eight percent of all returned surveys reported observing river otter sign within the last 5 years. Overall, the number of reported river otter sightings and observations of sign among all groups increased from 22 to 89 and 11 to 62, respectively, during the past 5 years. Survey participants reported river otters in 19 new counties (Fig. 2). State and federal wildlife employees reported river otters in 6 new counties (Cotton, Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). River otter death reports documented otters in 2 new counties (Okfuskee and Tulsa). Mail survey participants identified all counties where river otters were captured by APHIS employees except Creek and Seminole counties. Six new counties were reported by> 1 survey group (Carter, 13 Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). Locations of river otter sightings or observance of sign was similar among survey groups. Most sightings and/or signs occurred in localized areas (e.g., reservoirs) with high accessibility. Mail survey participants reported river otters throughout all counties identified by sign survey efforts. Combined, sign surveys and mail survey participants found river otters in 19 new individual counties (Fig. 2; Caire et al. 1989), and eight ofthose counties were not identified by sign surveys. DISCUSSION Mason and Macdonald (1987) noted a positive correlation (r2 = 0.84; P < 0.01) between the mean number of scats and the proportion of positive sites from each study area. Unlike others (Jenkins and Borrows 1980; Kruuk et al. 1986), Mason and Macdonald (1987) noted that scats can be used to make a broad comparison among populations. Nevertheless, the validity of using scats to determine otter (Lontra spp, Lutra spp.) occurrence is still debated (Gallantet al. 2007), but researchers throughout Europe continue to examine scats and proportions of positive sites to compare otter densities (Fusillo et al. 2007; MacDonald et al. 2007). Indirect signs are often effective tools to study wildlife species (Plumptre 2000; Sadlier et al. 2004; Stephens et al. 2006). However, caution should be used when interpreting river otter sign data (Rostain 2000; Gallagher 1999) because several factors can affect detection (Evans 2006, Fusillo et al. 2007); for instance, occupants could be outside of the sampled area but within its home range. Presence can often be determined, but absence can be impossible to determine (MacKenzie 2005). Others have reported 14 that there is not always a relationship between number of scats and number of river otters (Jenkins and Burrows 1980; Melquist and Hornocker 1983; Kruuk and Conroy 1987; Gallagher 1999; Gallant et al. 2007). Furthermore, sites with less scat could be an indication of fewer suitable latrine habitats (Romanowski et al. 1996). In contrast, we determined that no difference occurred between the number of suitable latrine sites at positive and negative sites. Because oftime constraints and high water levels, we did not sample Lower Canadian River and Walnut Creek and Lower North Canadian River watersheds. However, mail surveys, "death reports," and APHIS records documented river otters within both ofthese drainages. Sign surveys were conducted within the Little River Watershed, a tributary to the Canadian River in central Oklahoma. River otter sign was documented along the Little River in Pottawatomie County and below Lake Thunderbird in Cleveland County. To reach these locations, river otters must have used the Canadian River above Eufaula Lake. Within the Lower North Canadian River Watershed, we collected 1 river otter carcass and identified river otter signs above Eufaula Lake along the North Canadian River in McIntosh and Okfuskee counties. We examined 3 sites within the Muddy Boggy Creek Watershed that contained river otter sign. Most likely river otters have become well established throughout this watershed because reintroduction efforts (McGee Creek WMA), suitable habitats, and neighboring watersheds (Clear Boggy Creek Watershed, Kiamichi River Watershed) contained relatively high proportions of positive sites (Fig. 1). Mail surveys allowed us to obtain specific locations of river otters throughout Oklahoma and were relatively inexpensive and required less time and effort than sign 15 surveys; however, data should be interpreted cautiously. Previous researchers surveyed only natural resource employees because responses from outdoorsman were considered unreliable (Van Dyke and Brocke 1987; McBride et al. 1993; Pike et al. 1999). However, even natural resource professionals can be inaccurate when identifying animal sign unless properly trained (Evans 2006). Within our study, Chi-square analysis revealed that positive responses among surveyed groups (trappers, ODWC, federal employees) did not differ ("l = 1.17; df= 2; P> 0.10). Regardless of who is surveyed, researchers must account for issues regarding access; locations commonly visited by outdoorsman and areas not accessible could influence distributional data (Stubblefield and Shrestha 2007). Van Dyke and Brocke (1987) noted that human-based surveys should not be used alone to describe distribution of mountain lions; instead; such surveys should be used with other methods to determine spatial distribution. Mail survey information should only be used as estimates of mammal distribution (Blumberg 1993). Since the 1970s, river otters have become more prevalent throughout eastern Oklahoma and continued to spread westward, recolonizing parts of their historic range (Hatcher 1984; Base 1986). By 1992, APHIS employees reported catching river otters in 6 counties (Atoka, Haskell, Latimer, Leflore, McCurtain, Pushmataha) in southeastern Oklahoma. Illustrating westward movement, river otters were unintentionally captured in > 1 new county, on average, each year from 1991 to 2007 (Fig. 3), but the majority of annual incidental captures by APHIS employees came from southeastern Oklahoma. Currently, river otters have become well established and commonly occur throughout most of eastern Oklahoma. Although we documented river otters in central Oklahoma, it is unlikely that they occur at high densities throughout watersheds west of Blue River, 16 Clear Boggy Creek, and Lower Washita River watersheds and east ofWMNWR. Mail surveys and APHIS harvest records showed few accounts of river otters in central Oklahoma. Furthermore, sign surveys within Little River Watershed (central Oklahoma) showed relatively low proportions of sites containing river otter sign (29%). Similarly, 29% of examined sites along upper portions of the Deep Fork Watershed were positive. We suggest that no more than broad comparisons among large watersheds should be made from the proportion of positive sites within a watershed (Macdonald 1987) and management decisions should not be based solely on sign indices (Gallagher 1999). Most importantly, sign surveys should be used to monitor sample sites throughout time to document range expansion and/or reduction (Swimley and Hardisky 2000). Large reductions in population size may be more evident when baseline data have been recorded previously. Changes in scat frequency may be detectable only when otter populations have been impacted greatly (Jenkins and Burrows 1980; Mason and Macdonald 1987); for example, Lode (1993) used sign-surveys to document otter decline in France. Sign surveys were used to document range expansion and recolonization in Poland (Romanowski 2006). Other state wildlife agencies already use sign surveys to monitor river otter distributions (Boyd 2006, Evans 2006). Conducting systematic surveys is essential to species management and conservation throughout time (Elmeros and Bussenius 2002; Gallant 2007) and should be continued in Oklahoma. Within Oklahoma, relatively large watersheds such as Arkansas River, Canadian River, Red River, Cimarron River, and Washita River, follow a west-to-east pattern and facilitate westward dispersal and expansion of river otters. Studies using indirect sign to examine river otter populations should consider detectability and repeated 17 visits to determine river otter presence or absence (Royle and Nichols 2003; MacKenzie 2005). Observer skill should also be evaluated using standardized methods (Evans 2006). To achieve greater statistical power, the number of sites throughout each watershed should be increased. In locations where suitable latrine sites do not exist, European researchers have created artificial latrine sites to increase effectiveness of monitoring efforts (Chanin 2003). Chanin (2003) recommended that sign surveys should be conducted annually for 10 years, and then sampling should occur at intervals of2-3 years. Because sign surveys cannot detect annual fluctuations in river otter populations (Clark et al. 1987; Gallagher 1999), we recommend visiting sites biennially until variations (e.g., increase, decrease) cease. As baseline data and populations become established, sampling intervals can be repeated less frequently. ACKNOWLEDGMENTS Funding for this research was provided by the Federal Aid, Pittman-Robertson Wildlife Restoration Act under Project W-158-R ofthe Oklahoma Department of Wildlife Conservation and Oklahoma State University. The project was administered through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma Department of Wildlife Conservation, United States Geological Survey, Oklahoma State University, Wildlife Management Institute, and United States Fish and Wildlife Service cooperating). This publication was partially supported by the National Science Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under grant number HRD-0444082. We would like to thank S. K. Davis and A. A. Foster for their assistance in the field. A special thanks to D. Hamilton from the 18 Missouri Department of Wildlife Conservation and M. Fischer from the Arkansas Trappers Association for their guidance and training. We also thank R. Thornburg and S. Sheffert of the Oklahoma Fur Bearers Alliance for their insight and assistance. Numerous employees of the ODWC provided much needed assistance; we especially thank A. Crews for helping develop the river otter survey. We thank hundreds of state and federal employees and private and professional trappers who participated in the mail survey. We thank hundreds of landowners across eastern Oklahoma who allowed temporary access to their property. This project was completed as partial fulfillment for the requirements of the degree of Master of Science. LITERATURE CITED Anderson, S. 1977. Geographic ranges of North American terrestrial mammals. American Museum Novitates 2629:1-15. Anoop, K. R., and S. A. Hussain. 2004. Factors affecting habitat selection by smooth-coated otters (Lutra perspicillata) in Kerala, India. Journal of Zoology 263 :417- 423. Base, D. L. 1986. 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