The dark-ventral-patch of male red deer, a sexual signal that conveys the degree of involvement in rutting behavior

In polygynous mammals, signaling may play a decisive role in mating behavior, mediating the intensity of male fights and female mate choice. During the rutting season, male red deer may show a visible dark patch in their ventral fur. Recently, this patch has been suggested to act as a flexible sexual signal, due to its relationships with other variables such as age, body size, antler development, volatile compounds or the competitive environment. The analysis of fur pigmentation at the ventral patch suggests that this might also visually indicate the intrinsic predisposition to fight. To assess the possible role of this trait as a communicative signal, we hypothesized that the dark ventral patch in male Iberian red deer (<i>Cervus elaphus hispanicus</i>) is related to rutting behavior and mating success. Consistent with our predictions, we found in a field study that males with large dark patches showed a higher frequency of rutting behaviors (mainly roaring and flehmen), and more interactions with females and also attained larger harem sizes. Moreover, the dark ventral patch was a better predictor of male behavior than antler tines or territory holding, thus standing as a short-term indicator of male' willingness to invest in breeding competition.<br>