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Information on how animals partition their activities and travel among complementary resources, such as breeding or overwintering habitats, is needed for species conservation. In a mountain basin at 2500 m elevation in central Idaho, we studied the habitat use and movement patterns of 736 marked and 87 radio-tagged Columbia spotted frogs (Rana luteiventris) from 1995 to 1998. The goals of this study were to (i) identify and characterize R. luteiventris breeding, summer foraging, and overwintering habitats, (ii) describe the movement patterns of juvenile, male, and female R. luteiventris among these resources, and (iii) determine migration routes. Juvenile and adult R. luteiventris occupied a variety of widely distributed...
We assessed the effects of flow regulation on the demography of beavers (Castor canadensis) by comparing the density, home-range size, and body size of bank-dwelling beavers on two sixth-order alluvial river systems, the flow-regulated Green River and the free-flowing Yampa River, from 1997 to 2000. Flow regulation on the Green River has altered fluvial geomorphic processes, influencing the availability of willow and cottonwood, which, in turn, has influenced the demography of beavers. Beaver density was higher on the Green River (0.5?0.6 colonies per kilometre of river) than on the Yampa River (0.35 colonies per kilometre of river). Adult and subadult beavers on the Green River were in better condition, as indicated...
Eggs of a desert lizard (Callisaurus draconoides) were incubated under hydric conditions simulating those of natural nests. Eggs increased in mass during the first half of incubation owing to a net uptake of water, and declined in mass during the second half of incubation owing to a net loss of water. Patterns of net water exchange were related to water potential of substrates on which eggs were incubated, and could be modified by increasing the proportion of each eggshell contacting the substrate. Hatching success was high among eggs associated with wetter substrates but very low for eggs incubated on drier substrates. Eggs associated with wetter substrates also had longer periods of incubation and gave rise to...
Black-tailed prairie dogs (Cynomys ludovicianus) enter torpor intermittently during winter in the field but do not hibernate continuously from fall to spring. Previous studies have established that hibernators rely primarily on stored lipids during winter and that the storage of n?6 PUFAs in white adipose tissue (WAT) is required to maintain low body temperatures during this continuous torpor. Adult (>1 year) black-tailed prairie dogs were livetrapped in the fall, winter, spring, and summer (n = 10?12). To determine whether free-ranging black-tailed prairie dogs rely heavily on stored proteins during winter, we investigated seasonal changes in body composition of the prairie dogs with dual-energy X-ray absorptiometry...
Widespread reports of malformed amphibians in North America have prompted investigations into the cause(s) and implications of the phenomenon. Recently, a trematode parasite (Ribeiroia ondatrae) was identified as the probable cause of hind-limb malformations in Pacific treefrogs (Hyla regilla) from California. We exposed a second anuran species, the western toad (Bufo boreas), to specific levels of R. ondatrae infection. In a dose-dependent manner, R. ondatrae infection induced high frequencies (40–85%) of severe limb malformations in surviving toads. Survivorship declined significantly with increasing parasite exposure, falling to 42% in the heaviest treatment. Larvae in control treatments exhibited normal development...
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