Search

Understanding how top–down and bottom–up effects influence population dynamics of ungulates is essential for effective management and conservation, and there is an emerging consensus that forage productivity and quality interact with predation to influence survival. From 2009 to 2013, we captured and monitored 135 neonatal black-tailed deer Odocoileus hemionus columbianus in coastal California to study possible interactions between forage and predation on survival. We estimated seasonal and annual survival rates, assessed the cause of all mortalities (n = 93), measured available forage and diet quality, estimated relative abundances of predators on summer range each year, and used remote sensing to quantify habitat types on winter range. We evaluated the relationship between fawn survival and environmental covariates with cumulative incidence and proportional hazards functions. Summer survival rates averaged 0.40 (SE = 0.05) across all years and the mean annual survival rate was 0.26 (SE = 0.04). We found that most juvenile mortality resulted from predation during summer, and spatial differences in summer survival persisted until recruitment. Variation in mortality risk from all causes was related to the birth weight of juveniles and available oak forage but not predator abundance. The risk of black bear predation, the single largest cause of mortality, was unrelated to birth weight and showed an interaction between bear abundance and the amount of oak forage. Additionally, the good body condition of adult females in spring and a lack of relationship between mortality risk and variation in deer density did not provide evidence for purely bottom–up limitation. Rather our results provide evidence that both bottom–up and top–down effects were influencing fawn survival in this declining population, and that predator identity and the timing of mortality affected the impact of predation.

Density estimates are critical to proper population management and conservation, yet difficult to obtain for many wide-ranging or cryptic species. One proven method used to quantify carnivore density, especially species difficult to individually identify from photos taken by camera traps, utilizes overlapping home ranges of individual animals in the study area. This method, however, may be particularly prone to residency and extrapolation biases. Residency bias occurs when the reference area for the density estimate is incorrect, and extrapolation bias occurs when scaling a density to a different spatial extent than that of the study area upon which the estimate was based. We used a simulation approach based on GPS locations to diagnose potential biases in published densities of pumas Puma concolor from Patagonia, where Franklin et al. 1999 (Biol. Conserv. 90: 33–40) reported ‘minimum’ densities of 6 and 30 pumas per 100 km2, and Elbroch and Wittmer 2012a (Mammal. Biol. 77: 377–384) reported densities of ...

We compared injuries resulting from two different capture methods, i.e. trailing hounds and foot snares, for pumas Puma concolor in a mixed landscape with open grasslands and limited ‘retreat’ habitat in southern Chilean Patagonia. Injury scores were not significantly different for the two methods, although the small sample size for captures made with snares likely influenced our findings. Based on a potential range of 0-400, the mean injury score for pumas caught using hounds was 56.3 ± 132.9 (SD). The mean puma injury score for five animals caught in snares was 3.8 ± 1.1. Pumas were injured and/or killed in 86% of captures using trailing hounds. The number of hounds used in a capture attempt did not predict the likelihood of successfully catching a puma (P = 0.35), whereas there was a strong relationship between the number of dogs and the likelihood of a fight with the puma (P < 0.0001). The odds ratio calculation predicted a 14.7% increase in the likelihood of a fight between puma and hounds with the a...