Age-specific changes in body mass and delayed physical development of a known-aged sample of wild, white-tailed deer

Ontogeny is important to life history processes and evolution because it can influence fitness through survival and reproduction. However, most studies related to ontogeny of white-tailed deer (Odocoileus virginianus) have been carried out under controlled settings (in captive herds) where deer do not experience the same levels of environmental variability as wild deer. We use a 23-year data set of wild, known-aged deer to study changes in sex- and age-specific body mass. We found that body mass increased with age in both females and males and was best described by a 3rd order polynomial function. During the first year of life, from fawns to yearlings, females gained on average 76.6% greater mass while males gained 89.6% greater mass. Body mass gain slowed significantly after 2 years of age for females (annual gain was <7%), and by 2 years of age, females had reached 92% of their maximum lifetime body mass. For males, body mass continued to increase through 5 years of age. Body mass of males was largely influenced by their year of birth; however, this was not the case for females. Males born during suboptimal years showed signs of delayed physical development; males had less body mass as fawns and yearlings than males born during good years, but at 2 years of age, deer born during suboptimal years exhibited compensatory growth and had body mass similar to deer born during good years. These data make a significant contribution to ontogeny of white-tailed deer because these longitudinal data were collected on a known-aged, wild population under variable environmental conditions; a scenario for which a paucity of ontogenetic data exists.