Neonate morphometrics and lambing season characteristics of desert bighorn sheep

Desert bighorn sheep (Ovis canadensis) populations often occur in remote areas at low densities, leading to gaps in knowledge of life history. In November 2011, we translocated 11 female desert bighorn sheep from the Fra Cristobal Mountains and 9 from Red Rock Wildlife Management Area (RRWMA) to the Peloncillo Mountains in southwestern New Mexico. In December 2012, we captured 21 adult females in the Peloncillo Mountains, 14 of which were recaptured from 2011. We fitted each animal with a very high frequency (VHF) collar and vaginal implant transmitter (VIT) to monitor for parturition. We captured 26 lambs (5 females, 7 males in 2012; 7 males, 7 females in 2013), recorded morphometric measurements and fitted lambs with VHF collars to monitor survival. Over the study, 14 lambs died, with 12 mortalities from predation, one from abandonment, and one from unknown causes. Lambing season was protracted over 3–4 months and survival was unrelated to birth timing. Body mass differences between sex varied by year, suggesting a connection to annual climate. Because most studies focus on captive animals with access to supplemental food, captive lambs may not be representative of free-ranging populations. Thus, we investigated morphological trends in a free-ranging population.