Bovid horns play a prominent role in social and sexual interactions. In cold climates, however, heat loss through the horn surface may represent a major energy cost. We measured surface temperatures of horns (Th) for two Barbary sheep (Ammotragus lervia; one male and one female) at the Granby Zoo, Québec, using temperature-sensitive radiotrans-mitters. Over ambient temperatures (Ta) of 5 to — 19°C, Th never dropped below 3°C. At Ta ≈ −10°C, the difference between Th and Ta was 17°C for the male and 21°C for the female. Using empirical models to predict heat loss through horns and resting metabolic rates, we estimate that, at Ta of ≈−10°C, heat loss through the horn surface is 20% of resting metabolic rate for females and 29% for males which have larger horns than females. We argue that the metabolic costs of possessing large horns in cold climates may impose constraints on morphology and sexual selection.

You do not currently have access to this article.