The allometry between secondary sexual traits and body size is nonlinear among cervids

Abstract

Allometric relationships between sexually selected traits and body size have been extensively studied in recent decades. While sexually selected traits generally display positive allometry, a few recent reports have suggested that allometric relationships are not always linear. In male cervids, having both long antlers and large size provides benefits in terms of increased mating success. However, such attributes are costly to grow and maintain, and these costs might constrain antler length from increasing at the same rate as body mass in larger species if the quantity of energy that males can extract from their environment is limiting. We tested for possible nonlinearity in the relationship between antler size and body mass (on a log–log scale) among 31 cervids and found clear deviation from linearity in the allometry of antler length. Antler length increased linearly until a male body mass threshold at approximately 110 kg. Beyond this threshold, antler length did not change with increasing mass. We discuss this evidence of nonlinear allometry in the light of life-history theory and stress the importance of testing for nonlinearity when studying allometric relationships.

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

“…However, contrary to our results, when comparing three tropical deer species, Pathak et al (2001) found that it was the smallest species that had the lowest ash content (60.3% in Axis porcinus vs. 62.5% in A. axis and 62.9% in Rucervus duvaucelii). Other explanations may be related to evolutionary (but not adaptive) constraints, as proposed by Blob and LaBarbera (2001); or to the existence of adaptive constraints based on the quadratic body mass-antler allometry found in cervids (Lemaître et al 2014; larger antlers would have similar mechanical properties with smaller expenditure in minerals). Few studies attempted to investigate inter-specific differences in antler traits (Kitchener 1991, Blob & LaBarbera 2001, Pathak et al 2001, Blob & Snelgrove 2006.…”

Early life expenditure in sexual competition is associated with increased reproductive senescence in male red deer

“…Males also grow antlers anew each year, which are involved in fights during intra-sexual competition and their size is positively associated with lifetime reproductive success [25,26]. Antlers are expected to be energetically costly both to grow and maintain [27], because they constitute the only mammalian structure that is regenerated repeatedly over life and shows the fastest growth observed for an animal tissue [28]. Overall, the quantity of energy a male expends each mating season has been estimated to be around 25% of the annual energy budget [24].…”

Males do not senesce faster in large herbivores with highly seasonal rut

“…In mammals, the allocation of resources to sexual competition by males can occur through different pathways. For example, the growth of secondary sexual traits such as weapons, that generally involves increased body mass (Lemaître et al, 2014) and associated behaviors increase success in intrasexual competition, and are thereby subject to strong sexual selection pressures (Weckerly, 1998;Bro-Jørgensen, 2007;Lindenfors, 2007;Plard et al, 2011). Males sexually selected to allocate heavily to intra-sexual competition should increase their chances of reproducing, but in return are expected to experience an earlier or faster senescence (Bonduriansky et al, 2008).…”