Birth synchrony and survival of pronghorn fawns

Predation is often the primary mortality factor of neonatal pronghorn (Anti locapra americana). Birth synchrony can affect predation rates of young for some ungulates, but has not been examined in prong horn. We investigated c auses of mortality and the effect of birth synchrony on survival of neonata l pronghorn (n = 104) at Hart Mountain National Antelope Refuge in southcen tral Oregon from mid-May to mid-July in 1996 and 1997. Most (84%) of the ma rked fawns died during the monitoring period. Average age at death was 8.4 days and 83 (95%) of the fawns that died were <18 days old. Predation, prim arily coyote (Canis latrans), accounted for 86% (75/87) of the fawn deaths. Birth date affected survival where neonates born during the peak period of fawn drop lived longer than those born during the non-peak period (P <less than or equal to> 0.002). Of 17 surviving fawns, 14 had birth dates during the peak fawning period compared to 3 born during the non-peak period (P = 0.024). Survival rates for all fauns born during the peak fawning period ( (S) over cap (60) = 0.23) were greater (P < 0.001) than fawns born during t he non-peak period (<(S)over cap>(60) = 0.07). Our results indicated that b irth synchrony in pronghorn may be an important adaptation through which lo sses of young to predation can be reduced.