Search for: All records

Accurate estimates of mule deer survival are needed to model population dynamics and develop optimal management plans. Survival rates are often estimated using data from radio-collared animals but capture techniques to deploy these collars can risk mortality and injury to the animal. Our objective was to estimate age- and sex-specific survival rates of mule deer in the state of Utah, USA, while also investigating how these rates were affected by capture and handling. We captured 2,977 mule deer throughout the state and fitted them with radio-collars. Using Cox proportional hazard regression, we then estimated survival rates from the collected GPS data. We also examined the effects of age and sex on survival, while accounting for the influence of a variety of other covariates. Finally, we used a model selection framework to evaluate how long survival rates of captured animals were different from those of animals that were not captured. Fawn survival rates were 0.52 (0.45 – 0.60) for females and 0.66 (0.55– 0.79) for males, and overall adult survival rates were 0.76 (0.75 – 0.78) for females and 0.73 (0.70 – 0.77) for males. Survival rates for both sexes varied by age, latitude, and body condition. The negative effect of capture was small and initially disappeared after 3 weeks, but seemed to reappear later, perhaps during periods of high mortality. 

Nest predation influences population dynamics and is thought to exert strong selection on the evolution of avian life history. Because parental behaviors can attract the attention of nest predators, incubating birds are predicted to decrease conspicuous behaviors at the nest-site and increase incubation constancy when risks of nest predation are high. We examined whether snowy plovers Charadrius nivosus responded to predator-specific risks of nest predation, using the number of off bouts and daily nest attendance (proportion of time spent incubating) as responses. We quantified risks using predator-specific hazard rates of nest mortality, which varied daily and were based on habitat characteristics at each nest. We assessed the influence of predator-specific risks of nest mortality on incubation behaviors using an individual-centering approach, allowing us to explain variation in incubation behaviors within- and among-breeding pairs. We found increased number of off bouts and nest attendance within-breeding pairs in response to increasing risks of nest predation by foxes (Vulpes spp.) and gulls (Larus spp.), but not coyotes (Canis latrans) and common ravens (Corvus corax). Among breeding pairs across habitats, we found increased nest attendance in response to higher risks of nest predation by foxes, but not coyotes, gulls, or ravens. Breeding pairs differed in the amount of behavioral plasticity they exhibited in response to risks of nest predation. Our results suggest that risks of nest predation differentially influence behavioral responses of snowy plovers depending on the predator species, and the amount of behavioral plasticity may depend on the characteristics of breeding adults.