The dark ventral patch: A bimodal flexible trait related to male competition in red deer

Abstract

Sexual signals play a central role in male-male competition in polygynous species. In red deer (Cervus elaphus), male’s ventral area become dark during the rutting season due to urine spraying behaviour and retains many chemical compounds potentially revealing individual features. Here we investigate the variation in size of this trait, exploring its relationship with age and male competitive features such as antlers or body size, as well as populational level of intrasexual competition for mates. We found that the size of the dark ventral patch followed a clearly bimodal distribution, i.e. males mostly expressed the full-size trait or just developed a very small one. For these two groups of males according to trait expression, the relationships of trait size with age and antler size differed. Populational level of intrasexual competition appeared to affect the relationship between antler size and the probability of a fully developed ventral patch. These results indicate that the trait encodes information on body size, antler size, age and populational level of mate competition, thus suggesting a role in signalling male’s competitive features and willingness to allocate reproductive effort within a particular season.

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

“…Attempts to copulate, where the male rests his body on the back of the female. ventral patch expression provides more proximate information about individual attributes [38], thus allowing rival assessment to be most accurate at the moment when it takes place. Therefore, we suggest that the expression of the ventral patch might be the most important signal to evaluate, at least, the aggressive or competitive willingness of opponents.…”

“…2B). Despite these two categories might appear arbitrary, they were supported by the clearly bimodal distribution of the dark ventral patch size in red deer, above and below 50 cm length [36][37][38] and this bimodality is maintained over time (see Additional file 1: Appendix S4).…”

“…Adult males were classified into two categories attending to the size of the dark ventral patch (trait expression): individuals with small or large dark ventral patches (low trait expression, LTE, vs. high trait expression, HTE; see [38]). We considered LTE males to those individuals in which the dark area was not observed or males with patches that only reached halfway down the ventral area (Fig.…”

“…Recently, the dark ventral patch has been described as a complementary sexual trait in red deer [33][34][35][36][37]. This dark patch has a discrete, bimodal distribution in size [38] that might play a relevant role in communication during the rut. The hairs of this ventral area are impregnated by strongly odoriferous compounds that are related to some male characteristics such as age, and intrasexual competition level in the population [33,35].…”

“…The expression of the dark ventral patch in male red deer would be a communicative signal if it is related to changes in the behavior and fitness of both the sender and the receiver. Here, we assessed the possible role of this trait as a communicative signal [34,38] from the sender's perspective. Accordingly, we hypothesized that the dark ventral patch in male Iberian red deer (Cervus elaphus hispanicus) is related to rutting behaviour and mating success.…”