Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on Dec. 4, 2008). Includes bibliographical references.

Title from title page of PDF (University of Missouri--St. Louis, viewed February 10, 2010). Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 59-69). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 59-69). Also available on the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 2006. / Typescript. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 125 p. : ill. (some col.), maps. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--Rochester Institute of Technology, 2006. / Includes bibliographical references.

River otter (Lontra canadensis) populations in Illinois have rebounded considerably after >80 years of harvest protection and a successful reintroduction program. However, few studies of river otter ecology exist in the Midwestern U.S. where river otter numbers have increased in recent decades. Capturing study animals safely and efficiently is a critical part of wildlife research, and difficulties associated with live capture of river otters have contributed to the dearth of research on the species. Furthermore, estimating survival rates and identifying causes of mortality are important in effectively managing river otters. To address these knowledge gaps, my objectives were determine survival rates and mortality causes for river otters in southern Illinois, and to measure injury rates of river otters captured using Comstock traps. During 2014-16, I captured 42 river otters 49 times at Crab Orchard National Wildlife Refuge (CONWR) in southern Illinois. Eight river otters (3 M, 5 F) were captured in foot-hold traps during 788 trap nights (1 capture/88 trap nights), and the remaining 34 (19 M, 15 F) were captured in Comstock traps during 2,540 trap nights (1 capture/64 trap nights). I detected no significant differences in efficiency or escape rate between the 2 trap types, but Comstock traps did have higher rates for both unavailability and non-target captures. Eleven of the 20 river otters inspected for injuries received some type of injury as a result of capture in a Comstock trap (55%). The most common injury was claw loss (45%), followed by tooth fracture (25%), and lacerations (10%). The ease of setting the Comstock traps and of releasing non-target captures made them a more appealing option than foot-hold traps; however, river otters have a propensity for doing permanent damage to their teeth when live captured in Comstock traps. My study provides information on the functionality and safety of a novel live capture method for river otters. Thirty-four (16 F, 18 M) river otters were successfully radio-marked and monitored for survival for a total of 8,235 radio-days (¯x days/river otter = 242.2 ± 20.6 [SE throughout]). Two river otters (2 M) died during the period of radio-telemetry monitoring: 1 was trapped during nuisance wildlife control activities at an adjacent fish hatchery, and the other died of unknown causes. Annual survival rates were 1.0 ± 0.00 (lower confidence bound = 0.83) and 0.85 ± 0.09 for females and males, respectively, and similar between sexes (χ_1^2 = 1.7, P = 0.19). Pooled-sex breeding season survival was 0.96 ± 0.04. Trapping was the primary source of mortality over the course of my study. After radio-telemetry ended, 2 river otters were harvested by recreational trappers, at 114 (1 M) and 120 (1 F) weeks post-capture, and 1 male was killed by a vehicle collision at 52 weeks post-capture. Primary mortality sources for river otters in southern Illinois are similar to those reported elsewhere (i.e., trapping and vehicle collisions). Although I found no significant difference in survival rates between sexes, the majority of otters that died during my study were male (4 M, 1 F). As river otters occupying CONWR are protected from harvest, males may be more likely to leave the confines of CONWR, thereby putting themselves at greater risk to recreational trapping mortality. My study provides useful demographic information for Illinois’ recently-recovered river otter population.

Knowledge of reproduction in the river otter, Lutra canadensis, and of the factors which control the reproductive cycle, is limited. The reproductive biology of river otters in the marine environment of British Columbia, and some of the factors which may influence their reproductive cycle, in particular, the effect of photoperiod, were examined. The changes that occurred in the anatomy, histology and endocrinology of the annual reproductive cycle were determined in wild (226 male, 146 female) and captive (9 male, 5 female) otters. Reproductive cycles were similar in both groups. As in the fresh-water environment, coastal otters are seasonal breeders with a prolonged, obligatory period of embryonic diapause prior to implantation. Changes were similar to those reported in other mustelids. In males, development of the seminiferous tubules was divided into a series of nine distinct phases used to quantify the degree of reproductive activity present. Testosterone concentrations were highly correlated to changes in testicular activity, and fell into the low end of the range of concentrations seen in mustelids. Vaginal smear types were found to identify correctly the reproductive state of female otters. Estradiol concentrations of captive otters were highly variable, but the values obtained and the pattern of secretion were similar to those of other carnivores. Although estradiol levels of captive otters were reduced in the final two years of the study, normal ovarian development occurred. During pregnancy, progesterone concentrations corresponded to changes observed in luteal cell cytology. I present evidence suggesting that female otters are monestrous, induced ovulators. The timing of reproductive events of otters in the marine environment was similar to those of otters inhabiting fresh water at comparable latitudes. Reproductive activity of males began in the late autumn and adults were capable of breeding from late January through mid-May. Females exhibited estrus from late February through mid-May, with the majority of matings probably occurring during March and April. After a nine to eleven month period of embryonic diapause, implantation occurred the subsequent February. Births occurred after an estimated two month gestation and parturient 1 otters mated during lactation. Male otters were sexually mature at the end of their second year. Only 55% of females bred at age class 2 and sexual maturity was delayed until the following year in the remainder of the females. Pregnancy rates were high among females over 3 years of age and ovulation rates were similar to those of other studies. To determine the influence of photoperiod on the timing of reproductive events, captive otters were exposed to increased photoperiods. With one exception, spermatogenesis and estrus occurred earlier under experimental conditions. My results suggest that the termination of embryonic diapause is also under photoperiodic control. Variations in temperature or food were not associated with changes in reproductive condition. This study suggests that photoperiod probably controls the timing of the reproductive cycle of otters in British Columbia. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Dec. 7, 2009). Includes bibliographical references.