Coastal and Nongame Resources Division

Baton Rouge, LA, United States

Coastal and Nongame Resources Division

Baton Rouge, LA, United States
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Steen D.A.,Virginia Polytechnic Institute and State University | McClure C.J.W.,Boise State University | Sutton W.B.,Clemson University | Rudolph D.C.,U.S. Department of Agriculture | And 6 more authors.
Herpetologica | Year: 2014

Common Kingsnakes (formerly known collectively as Lampropeltis getula) are experiencing localized declines throughout the southeastern United States. Because there have been limited studies to determine how snakes regulate prey populations, and because Kingsnake declines may result in ecosystem impacts, we evaluated the hypothesis that Kingsnakes regulate the abundance of one of their prey, the venomous Copperhead (Agkistrodon contortrix). We generated a database of captures of the two species across the southeastern United States and, while controlling for large-scale habitat preferences, identified a negative relationship between the relative abundance of Kingsnakes and the relative abundance of Copperheads. Our results are correlative but consistent with the hypothesis that Copperhead populations experience a release from predation pressure where Kingsnake abundances are low. We suggest that Kingsnake declines, which are occurring for unknown reasons, are having ecological effects in affected ecosystems. We further highlight the potential role that snakes play in influencing the population dynamics of their prey.

Steen D.A.,Joseph W. Jones Ecological Research Center | Steen D.A.,Auburn University | Steen D.A.,Virginia Polytechnic Institute and State University | Mcclure C.J.W.,Auburn University | And 10 more authors.
Journal of Animal Ecology | Year: 2014

Summary: Snakes often occur in species-rich assemblages, and sympatry is thought to be facilitated primarily by low diet overlap, not interspecific interactions. We selected, a priori, three species pairs consisting of species that are morphologically and taxonomically similar and may therefore be likely to engage in interspecific, consumptive competition. We then examined a large-scale database of snake detection/nondetection data and used occupancy modelling to determine whether these species occur together more or less frequently than expected by chance while accounting for variation in detection probability among species and incorporating important habitat categories in the models. For some snakes, we obtained evidence that the probabilities that habitat patches are used are influenced by the presence of potentially competing congeneric species. Specifically, timber rattlesnakes (Crotalus horridus) were less likely than expected by chance to use areas that also contained eastern diamond-backed rattlesnakes (Crotalus adamanteus) when the proportion of evergreen forest was relatively high. Otherwise, they occurred together more often than expected by chance. Complex relationships were revealed between habitat use, detection probabilities and occupancy probabilities of North American racers (Coluber constrictor) and coachwhips (Coluber flagellum) that indicated the probability of competitive exclusion increased with increasing area of grassland habitat, although there was some model uncertainty. Cornsnakes (Pantherophis guttatus or Pantherophis slowinskii) and ratsnakes (Pantherophis alleghaniensis, Pantherophis spiloides, or Pantherophis obsoletus) exhibited differences in habitat selection, but we obtained no evidence that patterns of use for this species pair were influenced by current interspecific interactions. Overall, our results are consistent with the hypothesis that competitive interactions influence snake assemblage composition; the strength of these effects was affected by landscape-scale habitat features. Furthermore, we suggest that current interspecific interactions may influence snake occupancy, challenging the paradigm that contemporary patterns of snake co-occurrence are largely a function of diet partitioning that arose over evolutionary time. © 2013 British Ecological Society.

Steen D.A.,Joseph W. Jones Ecological Research Center | Steen D.A.,Auburn University | McClure C.J.W.,Auburn University | Brock J.C.,Joseph W. Jones Ecological Research Center | And 9 more authors.
Ecological Applications | Year: 2012

Habitat loss and degradation are thought to be the primary drivers of species extirpations, but for many species we have little information regarding specific habitats that influence occupancy. Snakes are of conservation concern throughout North America, but effective management and conservation are hindered by a lack of basic natural history information and the small number of large-scale studies designed to assess general population trends. To address this information gap, we compiled detection/nondetection data for 13 large terrestrial species from 449 traps located across the southeastern United States, and we characterized the land cover surrounding each trap at multiple spatial scales (250-, 500-, and 1000-m buffers). We used occupancy modeling, while accounting for heterogeneity in detection probability, to identify habitat variables that were influential in determining the presence of a particular species. We evaluated 12 competing models for each species, representing various hypotheses pertaining to important habitat features for terrestrial snakes. Overall, considerable interspecific variation existed in important habitat variables and relevant spatial scales. For example, kingsnakes (Lampropeltis getula) were negatively associated with evergreen forests, whereas Louisiana pinesnake (Pituophis ruthveni) occupancy increased with increasing coverage of this forest type. Some species were positively associated with grassland and scrub/shrub (e.g., Slowinski's cornsnake, Elaphe slowinskii) whereas others, (e.g., copperhead, Agkistrodon contortrix, and eastern diamond-backed rattlesnake, Crotalus adamanteus) were positively associated with forested habitats. Although the species that we studied may persist in varied landscapes other than those we identified as important, our data were collected in relatively undeveloped areas. Thus, our findings may be relevant when generating conservation plans or restoration goals. Maintaining or restoring landscapes that are most consistent with the ancestral habitat preferences of terrestrial snake assemblages will require a diverse habitat matrix over large spatial scales. © 2012 by the Ecological Society of America.

Gregory B.B.,Coastal and Nongame Resources Division | Whitaker J.O.,Indiana State University | Hartman G.D.,Gordon College
Southeastern Naturalist | Year: 2014

We investigated the diet of Corynorhinus rafinesquii (Rafinesque's Big-eared Bat) in west-central Louisiana by examining fecal pellets collected from beneath 3 bridges used by these bats as day roosts. Fresh fecal material was found under the bridges during every month of the year. We detected 5 insect orders, including 5 families, in fecal pellets collected from 25 August 2005 to 5 January 2007. Lepidoptera represented 93.7% of the total volume and was the only order observed in 100% of our samples. Coleopterans, mostly Scarabaeidae, were the second most abundant food item and represented 5.8% of the total volume. Hemiptera, Diptera, and Hymenoptera together represented 0.4 % of the total volume. We observed Diptera, Hemiptera, Hymenoptera, and Coleoptera in fecal pellets collected under some, but not all bridges. No insect orders were observed that had not previously been reported as prey of Rafinesque's Big-eared Bats. Our results were similar to those reported in studies conducted in Kentucky, North Carolina, and Florida, and we concluded that Rafinesque's Big-eared Bats primarily prey upon lepidopterans in Louisiana.

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