Sexual dimorphism and intercorhort variation in reindeer calf antler length is associated with density and weather

Abstract

We analysed intercohort variability of live weight and antler length of 5,123 reindeer calves. We further assessed the influence of climate and density on the interannual variation in antler length, and discussed sex-specific resource allocation and response to climate variability. Antler length varied significantly among years and between sexes, with interaction between year and sex. Body weight and antler length were highly positively correlated, showed similar intercohort variability, and had a strong allometrical link, suggesting that antler length could be an equally reliable measure of calf condition as live weight. We found a relative measure of antler length (i.e. antler length corrected for the allometric effect of body mass) to be positively influenced by increasing density and May-June precipitation, and also decreasing May-June temperature. We attributed the effect of early summer weather to its influence on forage availability and quality as well as the level of parasitic insect harassment. Gender difference in both the allometric exponents and the interannual variability suggest that young males and females may have different tactics for relative resource allocation towards growth of antlers as compared to body mass. Because antlers are costly to produce, they may be an honest signal of individual quality for both sexes. However, we found gender-specific allometry, as female calves more than males appear to prioritize their antler growth over body mass, especially when resources are limited. Thus, our results suggest that environmental variation may influence the extent of sexual dimorphism in antler length.

Dynamic effects of oviposition site on offspring sexually-selected traits and scaling relationships

“…Animals as diverse as ungulates and flies vary in sexual dimorphism according to environmental conditions (David et al 1994;Post et al 1999;Karan et al 2000;Weladji et al 2005;Bonduriansky 2007). However, intra-population variation in the degree of sexual dimorphism has often been assumed to be non-existent and has been ignored in many studies (discussed in Teder and Tammaru 2005).…”

Inter-Specific Differences in the Structure and Mechanics but not the Chemical Composition of Antlers in Three Deer Species

“…According to prevailing theories on costly secondary sexual characteristics, such as antlers, these structures are believed to indicate quality of the male, and thus are likely to reflect body condition and food intake (Harvey & Bradbury 1991; in deer antlers: Ditchkoff et al 2001, Weladji et al 2005. The rate of mineralization of antlers is faster than in any other animal tissue (Wolfe 1982, Gómez et al 2013.…”

Population management and bone structural effects in composition and radio-opacity of Iberian red deer (Cervus elaphus hispanicus) antlers

“…As a costly secondary sexual character, antlers are likely to reflect male quality, and as a result, they are influenced by body weight and diet (Harvey and Bradbury 1991;Ditchkoff et al 2001a;Schmidt et al 2001;Weladji et al 2005). Regarding the first factor, the positive relationship between antler weight and body weight is well established (Huxley 1931;Moore et al 1988;Gómez 2004).…”