Sharon A. Poessel

Environmental enrichment affects adrenocortical stress responses in the endangered black-footed ferret

Potential stressors of wildlife living in captivity, such as artificial living conditions and frequent human contact, may lead to a higher occurrence of disease and reduced reproductive function. One successful method used by wildlife managers to improve general well-being is the provision of environmental enrichment, which is the practice of providing animals under managed care with environmental stimuli. The black-footed ferret (Mustela nigripes) is a highly-endangered carnivore species that was rescued from extinction by removal of the last remaining individuals from the wild to begin an ex situ breeding program. Our goal was to examine the effect of environmental enrichment on adrenocortical activity in ferrets by monitoring fecal glucocorticoid metabolites (FGM). Results demonstrated that enrichment lowered FGM in juvenile male ferrets, while increasing it in adult females; enrichment had no effect on FGM in juvenile females and adult males. These results correspond with our findings that juvenile males interacted more with the enrichment items than did adult females. However, we did not detect an impact of FGM on the incidence of disease or on the ability of ferrets to become reproductive during the following breeding season. We conclude that an environmental enrichment program could benefit captive juvenile male ferrets by reducing adrenocortical activity.

Anticoagulant Rodenticide Exposure and Toxicosis in Coyotes (Canis latrans) in the Denver Metropolitan Area

Abstract Anticoagulant rodenticides are widely used in urban areas to control rodent pests and are responsible for secondary poisoning in many nontarget wildlife species. We tested the livers of five coyotes (Canis latrans) in the Denver Metropolitan Area, Colorado, US, for anticoagulant rodenticides. All five livers were positive for brodifacoum, with values ranging from 95 ppb to 320 ppb, and one liver was positive for bromadiolone, with a value of 885 ppb. Both of these rodenticides are second-generation anticoagulants, which are more potent and more likely to cause secondary poisoning than first-generation anticoagulants due to their accumulation and persistence in the liver. We concluded that exposure to these rodenticides may have caused the death of at least two of the five coyotes, and urban coyotes in our study area are commonly exposed to rodenticides.

Establishment of introduced reptiles increases with the presence and richness of native congeners

Darwin proposed two contradictory hypotheses to explain the influence of congeners on the outcomes of invasion: the naturalization hypothesis, which predicts a negative relationship between the presence of congeners and invasion success, and the pre-adaptation hypothesis, which predicts a positive relationship between the presence of congeners and invasion success. Studies testing these hypotheses have shown mixed support. We tested these hypotheses using the establishment success of non-native reptiles and congener presence/absence and richness across the globe. Our results demonstrated support for the pre-adaptation hypothesis. We found that globally, both on islands and continents, establishment success was higher in the presence than in the absence of congeners and that establishment success increased with increasing congener richness. At the life form level, establishment success was higher for lizards, marginally higher for snakes, and not different for turtles in the presence of congeners; data were insufficient to test the hypotheses for crocodiles. There was no relationship between establishment success and congener richness for any life form. We suggest that we found support for the pre-adaptation hypothesis because, at the scale of our analysis, native congeners represent environmental conditions appropriate for the species rather than competition for niche space. Our results imply that areas to target for early detection of non-native reptiles are those that host closely related species.

Landscape features influence postrelease predation on endangered black-footed ferrets

Predation can be a critical factor influencing recovery of endangered species. In most recovery efforts lethal and nonlethal influences of predators are not sufficiently understood to allow prediction of predation risk, despite its importance. We investigated whether landscape features could be used to model predation risk from coyotes (Canis latrans) and great horned owls (Bubo virginianus) on the endangered black-footed ferret (Mustela nigripes). We used location data of reintroduced ferrets from 3 sites in South Dakota to determine whether exposure to landscape features typically associated with predators affected survival of ferrets, and whether ferrets considered predation risk when choosing habitat near perches potentially used by owls or near linear features predicted to be used by coyotes. Exposure to areas near likely owl perches reduced ferret survival, but landscape features potentially associated with coyote movements had no appreciable effect on survival. Ferrets were located within 90 m of perches more than expected in 2 study sites that also had higher ferret mortality due to owl predation. Densities of potential coyote travel routes near ferret locations were no different than expected in all 3 sites. Repatriated ferrets might have selected resources based on factors other than predator avoidance. Considering an easily quantified landscape feature (i.e., owl perches) can enhance success of reintroduction efforts for ferrets. Nonetheless, development of predictive models of predation risk and management strategies to mitigate that risk is not necessarily straightforward for more generalist predators such as coyotes.

Spatial ecology of coyotes in the Denver metropolitan area: influence of the urban matrix

Urbanization alters landscapes and ecosystem processes that result in negative impacts for many species. However, urbanization also creates novel environments that certain species, including carnivores, are able to exploit. Coyotes (Canis latrans) are 1 example of a species capable of exploiting urban environments throughout North America and, in some cases, becoming involved in human–coyote conflict. As part of a comprehensive study of human–coyote coexistence in the Denver metropolitan area of Colorado, we investigated the spatial ecology of coyotes to determine movement and activity patterns relative to the urban matrix. We examined home-range size, habitat use, and resource selection for 22 coyotes monitored with GPS collars during 2012–2014. Mean (± SD) home-range size of resident coyotes (11.6 ± 11.0 km2) was smaller than ranges of transient coyotes (200.7 ± 232.4 km2). Home-range size did not vary by season or sex, but resident coyotes during the day (7.2 ± 10.5 km2) had smaller home ranges than during the night (11.3 ± 10.8 km2). Coyotes had high percentages of developed lands (44.5 ± 18.9%) within their home ranges, contrary to previous studies of urban coyotes. However, the percentage of coyote locations in natural lands (48.9 ± 22.4%) was higher than in developed lands (20.6 ± 11.7%). Homerange size of residents was not related to either the percentage of developed lands or altered lands within home ranges. Coyotes selected natural lands over developed lands, and they increased activity at night. Although coyotes were able to thrive in home ranges containing large amounts of development, they continued to avoid areas with high human activity by primarily residing in areas with natural land cover. Similar to urban areas throughout the Northern Hemisphere, coyotes in the Denver metropolitan area have become efficiently adapted to a highly developed landscape, reflecting the flexible nature of this opportunistic carnivore.

Den attendance patterns in swift foxes during pup rearing: varying degrees of parental investment within the breeding pair

Parental investment varies in mammalian species, with male care of young being more common in social and monogamous species. Monogamy is commonly observed in canid species, with both males and females, and often “helper” individuals, providing some degree of care for the young. Social units of the swift fox (Vulpes velox), a small North American canid species, usually consist of a male–female pair and occasionally helpers. The role of parental investment and behavior in swift fox society is currently poorly understood. We observed swift fox dens during the pup-rearing season in each of 2xa0years to evaluate attendance and frequency of visits to natal dens by adult males and females. Female foxes remained at dens longer and visited them more frequently than did male foxes. Female attendance and visitation decreased throughout the pup-rearing season as pups became older and more independent. Environmental factors, including climate and its effect on prey, appeared to contribute to differences in fox behavior between the 2xa0years. We observed only one fox outside of the breeding pair attending a den in each of the 2xa0years, both of which were males. We concluded that each of these two foxes were living within the social unit of the male–female pair as a trio, but not serving as a helper and contributing to the care of the pups. Our results increased knowledge of the ecology and behavior of the swift fox, a species of conservation concern in the Great Plains of North America.

Global assessment of establishment success for amphibian and reptile invaders

Abstract Context. According to the tens rule, 10% of introduced species establish themselves. Aims. We tested this component of the tens rule for amphibians and reptiles globally, in Europe and North America, where data are presumably of good quality, and on islands versus continents. We also tested whether there was a taxonomic difference in establishment success between amphibians and reptiles. Methods. We examined data comprising 206 successful and 165 failed introduction records for 161 species of amphibians to 55 locations, and 560 successful and 641 failed introduction records for 469 species of reptiles to 116 locations around the world. Key results. Globally, establishment success was not different between amphibians (67%) and reptiles (62%). Both means were well above the 10% value predicted by the tens rule. In Europe and North America, establishment success was lower, although still higher than 10%. For reptiles, establishment success was higher on islands than on continents. Our results question the tens rule and do not show taxonomic differences in establishment success. Implications. Similar to studies on other taxa (birds and mammals), we found that establishment success was generally above 40%. This suggests that we should focus management on reducing the number of herptile species introduced because both reptiles and amphibians have a high likelihood of establishing. As data collection on invasions continue, testing establishment success in light of other factors, including propagule pressure, climate matching and taxonomic classifications, may provide additional insight into which species are most likely to establish in particular areas.