Data from: The effect of terrain and female density on survival of neonatal white-tailed deer and mule deer fawns

Juvenile survival is a highly variable life-history trait that is critical to population growth. Antipredator tactics, including an animal's use of its physical and social environment, are critical to juvenile survival. Here, we tested the hypothesis that habitat and social characteristics influence coyote (Canis latrans) predation on white-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) fawns in similar ways during the neonatal period. This would contrast to winter when the habitat and social characteristics that provide the most safety for each species differ. We monitored seven cohorts of white-tailed deer and mule deer fawns at a grassland study site in Alberta, Canada. We used logistic regression and a model selection procedure to determine how habitat characteristics, climatic conditions, and female density influenced fawn survival during the first 8 weeks of life. Fawn survival improved after springs with productive vegetation (high integrated Normalized Difference Vegetation Index values). Fawns that used steeper terrain were more likely to survive. Fawns of both species had improved survival in years with higher densities of mule deer females, but not with higher densities of white-tailed deer females, as predicted if they benefit from protection by mule deer. Our results suggest that topographical variation is a critical resource for neonates of many ungulate species, even species like white-tailed deer that use more gentle terrain when older. Further, our results raise the possibility that neonatal white-tailed fawns may benefit from associating with mule deer females, which may contribute to the expansion of white-tailed deer into areas occupied by mule deer.

幼体存活率是一类高度可变的生活史特征，对种群增长至关重要。动物借助物理与社会环境实施的反捕食策略，亦是幼体存活的关键保障。本研究验证了如下假说：在新生期，生境与社会特征对郊狼（Canis latrans）捕食白尾鹿（Odocoileus virginianus）与骡鹿（O. hemionus）幼崽的影响模式相似，这与冬季的情况形成鲜明对比——冬季为两个物种提供最优庇护的生境与社会特征存在差异。我们于加拿大阿尔伯塔省的一处草原研究样地，对7个同龄群的白尾鹿与骡鹿幼崽开展了监测，采用逻辑回归与模型选择流程，探究生境特征、气候条件以及雌鹿种群密度对幼崽出生后前8周存活率的影响。结果显示，春季植被生产力较高（归一化差分植被指数（Normalized Difference Vegetation Index, NDVI）积分值较高）的年份，幼崽存活率会有所提升；栖息于坡度更陡地形的幼崽存活率更高。正如预期那般，当骡鹿雌鹿种群密度较高时，两个物种的幼崽存活率均会提升；而白尾鹿雌鹿种群密度升高则无此效应。本研究结果表明，地形异质性是诸多有蹄类动物新生个体的关键生存资源，即便对于成年后偏好平缓地形的白尾鹿亦是如此。此外，本研究结果还提出一种可能性：新生白尾鹿幼崽或可通过与骡鹿雌鹿集群获得生存收益，这或许会推动白尾鹿向骡鹿的现有分布区域扩张。