Antler and Body Size in Black-Tailed Deer: An Analysis of Cohort Effects

Johanna C Thalmann,Floyd W Weckerly,Dale R Mccullough,Ken A Aho,R Terry Bowyer

doi:10.1155/2015/156041

Johanna C Thalmann, Floyd W Weckerly + Show 3 more

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https://doi.org/10.1155/2015/156041

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Abstract

For long-lived species, environmental factors experienced early in life can have lasting effects persisting into adulthood. Large herbivores can be susceptible to cohort-wide declines in fitness as a result of decreases in forage availability, because of extrinsic factors, including extreme climate or high population densities. To examine effects of cohort-specific extrinsic factors on size of adults, we performed a retrospective analysis on harvest data of 450 male black-tailed deer (Odocoileus hemionus columbianus) over 19 years in central California, USA. We determined that population density of females had a more dominant effect than did precipitation on body size of males. Harvest of female deer resulted in increases in the overall size of males, even though a 6-year drought occurred during that treatment period. Body size was most influenced by female population density early in life, while antler size was highly affected by both weather early in life and the year directly before harvest. This study provides insights that improve our understanding of the role of cohort effects in body and antler size by cervids; and, in particular, that reduction in female population density can have a profound effect on the body and antler size of male deer.

Highlights

Climate and population density influence organisms throughout their lives and often lead to phenotypic variation among cohorts
Dressed weight and antler size (PC1) were positively related (Figure 4), but to better understand changes in size of male deer, we examined those variables separately
Even though the 85% CI overlapped zero, female population density while the male was in utero had a significant positive trend in determining antler size, but only after female harvest began in 1985

Summary

Introduction

Climate and population density influence organisms throughout their lives and often lead to phenotypic variation among cohorts. Understanding how the interaction between climate and population density influences body mass throughout the lifetime of a large herbivore enables biologists to better predict growth, survival, and reproduction within cohorts [13,14,15,16,17]. Extrinsic and intrinsic factors affect body condition, and when resources are limited, important tradeoffs may be made early in life by an individual, or by a mother before parturition, which affects offspring while in utero [18]. Those tradeoffs result in delayed life-history characteristics that can persist into adulthood and even through future generations [4]

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