Survival and causes of mortality for pygmy rabbits (Brachylagus idahoensis) in Oregon and Nevada

Abstract 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 ...