Time filter

Source Type

Forest Lake, MN, United States

Mech L.D.,U.S. Geological Survey | Christensen B.W.,University of California at Davis | Asa C.S.,Saint Louis Zoo | Callahan M.,Wildlife Science Center | Young J.K.,Utah State University
PLoS ONE | Year: 2014

Using artificial insemination we attempted to produce hybrids between captive, male, western, gray wolves (Canis lupus) and female, western coyotes (Canis latrans) to determine whether their gametes would be compatible and the coyotes could produce and nurture offspring. The results contribute new information to an ongoing controversy over whether the eastern wolf (Canis lycaon) is a valid unique species that could be subject to the U. S. Endangered Species Act. Attempts with transcervically deposited wolf semen into nine coyotes over two breeding seasons yielded three coyote pregnancies. One coyote ate her pups, another produced a resorbed fetus and a dead fetus by C-section, and the third produced seven hybrids, six of which survived. These results show that, although it might be unlikely for male western wolves to successfully produce offspring with female western coyotes under natural conditions, western-gray-wolf sperm are compatible with western-coyote ova and that at least one coyote could produce and nurture hybrid offspring. This finding in turn demonstrates that gamete incompatibility would not have prevented western, gray wolves from inseminating western coyotes and thus producing hybrids with coyote mtDNA, a claim that counters the view that the eastern wolf is a separate species. However, some of the difficulties experienced by the other inseminated coyotes tend to temper that finding and suggest that more experimentation is needed, including determining the behavioral and physical compatibility of western gray wolves copulating with western coyotes. Thus although our study adds new information to the controversy, it does not settle it. Further study is needed to determine whether the putative Canis lycaon is indeed a unique species.

Christensen B.W.,Iowa State University | Asa C.S.,Saint Louis Zoo | Wang C.,Iowa State University | Bauman K.,Saint Louis Zoo | And 3 more authors.
Theriogenology | Year: 2013

We evaluated two approaches to improving in vitro wolf sperm survival. Both approaches aimed to reduce the exposure of sperm to prostatic fluid resulting from electroejaculation: (1) use of extender formulations recently developed for the domestic dog (the most closely related domestic species); and (2) dilution of ejaculate shortly after semen collection. Three commercial extenders were compared with the TRIS-based extender we had previously used. We also compared the effects on motility of adding extender immediately after collection to our previous protocol in which extender was added after centrifugation. Both subjective and objective (computer-assisted semen analysis program) kinematic measurements were made. Relatively minor differences were noted (and not in total or progressive motility) between the centrifugation protocols. Two of the commercial extenders resulted in significant improvement in motility over the TRIS-based extender and one of the other commercial extenders at 8 hours after collection (mean ± SEM; total motility was 68.3 ± 4.0% and 70.0 ± 4.0% compared with 53.3 ± 4.0% and 55.0 ± 4.0%, respectively; progressive motility 58.6 ± 5.4% and 57.1 ± 5.4% compared with 32.8 ± 5.4% and 39.3 ± 5.4%; P < 0.05). We inferred that components in two of the commercial dog extenders might provide more protection for wolf sperm, prolonging their motility. © 2013 Elsevier Inc.

Lance N.J.,U.S. Department of Agriculture | Lance N.J.,Utah State University | Breck S.W.,U.S. Department of Agriculture | Sime C.,Montana Fish | And 3 more authors.
Wildlife Research | Year: 2010

Context. Wolf predation on livestock can cause economic hardship for livestock producers as well as reduce tolerance for wolves. Lethal control of wolves is often controversial; thus, development of effective non-lethal methods for reducing wolflivestock conflict is important. Electrified fladry is a new tool that is similar to fladry (i.e. a barrier system that scares wolves), but electrified fladry also incorporates an electric shock designed to decrease the potential for wolves to habituate to the barriers. Aim. Evaluation of electrified fladry requires understanding of its effectiveness relative to fladry and the costs and benefits of applying it in the field. Methods. By using captive wolves, we compared the effectiveness of electrified fladry v. fladry for protecting a food resource during 2-week trials. We then performed a field trial with electrified fladry for managing wolves in Montana, USA. We measured livestock depredation and wolf activity on six treatment and six control pastures, calculated the cost of installation and maintenance, and surveyed all study participants about application of electrified fladry. Key results. We found electrified fladry 2-10 times more effective than fladry at protecting food in captivity and that hunger increased the likelihood of wolves testing fladry barriers. In field trials, we installed 14.0km of EF systems in treatment pastures and detected wolves twice in control pastures but never in the treatment pastures. No livestock were killed by wolves in treatment or control pastures. A completed electrified fladry system cost $2303 for the first km and $2032 for each additional km, and required 31.8 person-hours per kilometre to install. We observed 18 failures (i.e. electrified system stopped working) during a total of 394 days of use. In total, 83% of ranchers who used fladry would continue to use it under certain conditions, indicating some psychological benefit to users. Conclusions and implications. The present study has demonstrated that electrified fladry offers superior protection compared with non-electrified fladry; however, further field tests are warranted to help determine whether benefits outweigh costs. © CSIRO 2010.

Derbridge J.J.,University of Arizona | Merkle J.A.,Laval University | Merkle J.A.,University of Wyoming | Bucci M.E.,University of Montana | And 4 more authors.
PLoS ONE | Year: 2015

Stable isotope analysis of diet has become a common tool in conservation research. However, the multiple sources of uncertainty inherent in this analysis framework involve consequences that have not been thoroughly addressed. Uncertainty arises from the choice of trophic discrimination factors, and for Bayesian stable isotope mixing models (SIMMs), the specification of prior information; the combined effect of these aspects has not been explicitly tested. We used a captive feeding study of gray wolves (Canis lupus) to determine the first experimentally-derived trophic discrimination factors of C and N for this large carnivore of broad conservation interest. Using the estimated diet in our controlled system and data from a published study on wild wolves and their prey in Montana, USA, we then investigated the simultaneous effect of discrimination factors and prior information on diet reconstruction with Bayesian SIMMs. Discrimination factors for gray wolves and their prey were 1.97‰ for δ13C and 3.04‰ for δ15N. Specifying wolf discrimination factors, as opposed to the commonly used red fox (Vulpes vulpes) factors, made little practical difference to estimates of wolf diet, but prior information had a strong effect on bias, precision, and accuracy of posterior estimates. Without specifying prior information in our Bayesian SIMM, it was not possible to produce SIMM posteriors statistically similar to the estimated diet in our controlled study or the diet of wild wolves. Our study demonstrates the critical effect of prior information on estimates of animal diets using Bayesian SIMMs, and suggests species-specific trophic discrimination factors are of secondary importance. When using stable isotope analysis to inform conservation decisions researchers should understand the limits of their data. It may be difficult to obtain useful information from SIMMs if informative priors are omitted and species-specific discrimination factors are unavailable. © 2015 Derbridge et al.

Christensen B.W.,Iowa State University | Asa C.S.,i-drive | Wang C.,Iowa State University | Vansandt L.,i-drive | And 4 more authors.
Theriogenology | Year: 2011

Genetic management of Mexican gray wolves includes semen banking, but due to the small number of animals in the population and handling restrictions, improvements in semen collection and cryopreservation rely on results from studies of domestic dogs. Semen collection from wolves requires anesthesia and electroejaculation, which introduce potentially important variables into species comparisons, as dog semen is typically collected manually from conscious animals. To investigate possible effects of collection method on semen quality, we compared semen collection by the traditional manual method and by electroejaculation (EE) in a group of dogs (n = 5) to collection by EE only in wolves (n = 7). Samples were divided into two aliquots: neat or diluted in Tris/egg yolk extender, with motility evaluated at intervals up to 24 h. There were no differences (P > 0.10) in sperm motility in either neat or extended samples at 24 h from EE dogs and wolves, although motility of the wolf neat samples declined more rapidly (P < 0.05). However, there were differences (P < 0.01) between EE and manually collected dog semen in motility at 24 h, in both the neat and extended samples. Therefore, general motility patterns of dog and wolf semen collected by EE were similar, especially when diluted with a Tris/egg yolk extender, but sperm collected from dogs by EE did not maintain motility as long as manually collected samples, perhaps related to the longer exposure of EE samples to more prostate fluid. © 2011 Elsevier Inc.

Discover hidden collaborations