Survival and Cause-Specific Mortality of Neonatal Mule Deer Fawns, North-Central New Mexico



    1. Department of Fishery and Wildlife Sciences, P.O. Box 30003, MSC 4901, New Mexico State University, Las Cruces, NM 88003, USA
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    • Trinity River National Wildlife Refuge, P.O. Box 10015, Trinity, TX 77575, USA


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    1. United States Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, P.O. Box 30003, MSC 4901, Las Cruces, NM 88003, USA
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Abstract: Because of significant declines in mule deer (Odocoileus hemionus) populations across New Mexico, USA, we investigated survival of fawns in north-central New Mexico, USA. We captured 19 fawns, 34 fawns, and 47 fawns in 2002, 2003, and 2004, respectively, and used fawn morphological measurements, habitat characteristics, and adult female (hereafter “female”) condition to model preweaning fawn survival. Survival was 0.0, 0.12, 0.52 for 2002, 2003, and 2004, respectively, and was related to birth mass (χ12 = 9.5, P = 0.002), birth date (χ12= 8.4, P = 0.004), litter size (χ22 = 9.4, P = 0.009), female body fat (χ12 = 40.9, P < 0.001), annual precipitation (χ12 = 35.0, P < 0.001), summer precipitation (χ12= 37.5, P < 0.001), and winter precipitation (χ12 = 32.0, P < 0.001). Total ingesta-free body fat of females (β = 3.01, SE = 0.75; odds ratio = 20.19, 95% CI = 4.64-87.91) and birth mass of fawns (β = 1.188, SE = 0.428; odds ratio = 3.38, 95% CI = 1.42-7.59) were the best predictors of survival of individual fawns, although few of the logistic models differed in model selection criteria. Fawn survival in north-central New Mexico was driven by an interaction of total and seasonal precipitation and its effect on plant production, consequential effects on female nutrition, and ultimately, fawn birth attributes. Habitat conditions were so poor throughout north-central New Mexico during 2002 and 2003 (and likely during other drought yr) that, based upon birth attributes, few fawns could have survived regardless of proximate causes of mortality. In 2004, precipitation enhanced security cover, maternal body condition, birth attributes and, thus, survival of fawns. However, more habitat enhancements are needed to improve the nutritional quality of mule deer habitats in north-central New Mexico and further enhance maternal and fawn condition to recover mule deer populations in this region.