Growth and mortality of sympatric white-tailed and mule deer fawns

摘要: Population growth rates of cervids are sensitive to changes in adult female survival, but fawn recruitment tends be the population vital rate most susceptible density-dependent population-level influences. We conducted a study survival and related biology northwest Crockett County, Texas, USA, during 2004–2007 an area where white-tailed deer (Odocoileus virginianus) mule (O. hemionus eremicus) existed sympatrically. Our was justified by need explain annual variation female-to-fawn ratios apparent field surveys. Using vaginal implant transmitters radio-marked females locate birth sites, we captured, weighed, radio-collared fawns on 4 privately owned ranches. monitored collared daily investigated mortalities within 24 hours receiving mortality signal determine cause death. When possible, collected thymus glands assess body condition. captured 170 (64 deer; 106 deer), which 145 were known-age from females, found that relatively heavy birthed fawns. also noted mass gain fawns’ very low compared other studies documented mortalities: 47 predation, sickness-starvation, 1 conspecific trauma, 3 undeterminable. Bobcats (Lynx rufus) responsible for nearly all predation; gland data indicated bobcats did not select weaker used proportional hazards regression factors influencing competing risks made comparisons between species when possible. censored 6 our analyses half occurred 15 days postpartum, 12 139 (9%) died 25 m site. Fawn 78% at old, median estimated age-at-capture unknown adults. Annual ranged 50% born 2004 17% 2006, with no overall effect species. greatest rain May–August late-gestation lactation period greatest. Mule succumbed more sickness-starvation than Rates predation increased deviance mean dates reduced period. Early relative mass, sex became important about 30 after males greater risk sickness-starvation. Lunn-McNeil competing-risks models suggested some interaction predation. mortality, gain, weaning populations both chronically stressed near carrying capacity fluctuated annually invested little energy rearing captive females. © 2017 The Wildlife Society.