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We investigated the effects of predation risk on birth-site selection by Rocky Mountain elk (Cervus elaphus nelsoni) during summer in 2002–2004 in northeastern Oregon at macrohabitat (3rd-order selection) and microhabitat (4th-order selection) scales. This study describes vegetative characteristics of birth sites selected by female elk when young ,4–5 days old used the hiding strategy and predation sites when most predation events occurred on young .5 days old that used the fleeing strategy. At the macrohabitat scale we observed no evidence that female elk were influenced by predation risk when selecting a birth site on the basis of variables measured in this study. Females chose birth sites with less overhead cover than random sites, suggesting that they might have been influenced more by forage availability than predation risk. At the microhabitat scale females selected birth sites that had more overhead canopy cover and greater visibility at ground level than paired random sites, which suggested that birth-site selection at this scale was influenced by predation risk. Together, these results suggested that female elk selected areas for parturition at the macrohabitat scale that likely had forage to meet high nutritional demands of lactation and at the microhabitat scale selected areas that provided visibility to detect predators and reduce the risk of predation. Predators, mainly cougars (Puma concolor), killed young in areas closer to vegetative edges at the macrohabitat scale and with more visibility at the microhabitat scale. These areas were likely conducive to cougar hunting where sight and cover from forest edges can be important for stalking calves that are traveling with their mothers and family groups.

Factors influencing the survival of pygmy rabbits (Brachylagus idahoensis) are poorly understood and have received minimal attention in previous studies. We investigated survival and causes of mortality of pygmy rabbits in southeastern Oregon and northwestern Nevada. We trapped 298 rabbits on 4 sites and fitted each with radiotransmitters. We used known-fate models in program MARK to estimate survival rates of radiomarked pygmy rabbits from September 2005 to August 2006. The best model, based on Akaike's information criterion, indicated that survival rates varied among study sites, sexes, and with monthly interval in a parallel pattern [model S (area * sex + t)]. The estimated annual survival rate on the 4 study sites was notably low and varied from 0.003 (SE = 0.003) to 0.173 (SE = 0.066). Predation on radiomarked rabbits was high for both adult (88.6%) and juvenile (89.4%) rabbits. When the predator species could be determined, the most common predators of pygmy rabbits were coyotes (Canis ...

We used program CAPTURE to analyze 1,535 capture–recapture data sets from 33 species of small mammals for sources of variation in capture probabilities and to characterize species-specific responses to mark–recapture trapping. Program CAPTURE contains 8 models to account for all possible combinations of heterogeneity (h), behavioral response (b), and time (t) effects on capture probabilities. Model Mo (equal capture probabilities) was selected most often by CAPTURE as the most appropriate model for small sample sizes, reflecting the difficulty of detecting unequal probabilities of capture in small data sets. Heterogeneity in capture probabilities among individuals was evident in larger data sets for all species of small mammals examined. Strong behavioral responses were detected in several species. Sylvilagus, Tamias amoenus, Glaucomys sabrinus, Perognathus longimembris, and Microtus ochrogaster were trap shy, whereas Tamias striatus, Tamias townsendii, Spermophilus richardsonii, Perognathus parvus, Reithrodontomys megalotis, Peromyscus maniculatus, Peromyscus truei, Sigmodon hispidus, Microtus californicus, and Microtus pennsylvanicus were trap prone. Time effects were not apparent for most species except where they were accompanied with heterogeneity. Murid species had the highest estimated probabilities of capture, followed by heteromyids, sciurids, and leporids in decreasing order. Estimates of abundance from model Mh were significantly greater than those from models Mb, Mo, and Mt, which likely reflects the negative bias of these latter estimators.

La methode presentee est la plus precise et la mieux adaptee pour l'etude des classes d'âge au sein des populations

The difference between the mean standard metabolic rates of Microtus longicaudus acclimated to 15°C (2.62 cubic centimeters 02 per gram-hour) and those acclimatized at natural temperatures averaging 11°C (2.67 cc 02/g-hr) is not statistically significant. These values are 60 to 70 per cent higher than predictions based on body weight. The relationship of oxygen consumption to ambient temperature (0 to 40°C) was determined for voles in and out of their nests. The zone of thermoneutrality while in the nest (20 to 30°C) was 5° wider than when not in the nest (25 to 30°C). The relationship of oxygen consumption to ambient temperature below thermoneutrality was linear, described by the equation Y = 5.54 − .146 X (in the nest) and Y = 7.26 − .181 X (out of the nest). Above thermoneutrality, the relationship becomes curvilinear and is described by the equation log Y =.455 − .017 X . Visual observations at temperatures above thermoneutrality revealed no special behavioral patterns for thermoregulation. Body temperature of M . longicaudus was independent of ambient temperature between 5° and 25°C, averaging 37.4°C.