Effects of population density on static allometry between horn length and body mass in mountain ungulates

Little is known about the effects of environmental variation on allometric
relationships of condition-dependent traits, especially in wild
populations. We estimated sex-specific static allometry between horn
length and body mass in four populations of mountain ungulates that
experienced periods of contrasting density over the course of the study.
These species displayed contrasting sexual dimorphism in horn size; high
dimorphism in Capra ibex and Ovis canadensis and low dimorphism in
Rupicapra rupicapra and Oreamnos americanus. The effects of density on
static allometric slopes were weak and inconsistent while allometric
intercepts were generally lower at high density, especially in males from
species with high sexual dimorphism in horn length. These results confirm
that static allometric slopes are more canalized than allometric
intercepts against environmental variation induced by changes in
population density, particularly when traits appear more costly to produce
and maintain.