The intensity of male-male competition may affect chemical scent constituents in the dark ventral patch of male Iberian red deer

Peña, Eva de la; Martı́n, José; Carranza, Juan

doi:10.1371/journal.pone.0221980

Cited by 14 publications

(27 citation statements)

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“…Previous studies, using genetic and behavioural tools, have shown clear differences in the degree of male-male competition 30 and the consequences in the transmission of genetic variability to the next generation 29 between these two social environments. Our results are also in agreement with the effects of male competition in these same Iberian red deer populations on the dark ventral patch, that may be modulated in the short term by urination, changing its size (Carranza et al, under review) and its chemical constituents 31 . Predicted means of antler length (cm, ± se) of 2 and 3 year-old males in estates with high (HC) and low (LC) male-male competition for mating opportunities.…”

Section: Discussionsupporting

confidence: 90%

Social environment modulates investment in sex trait versus lifespan: red deer produce bigger antlers when facing more rivalry

Carranza

Pérez‐Barbería

Martín

et al. 2020

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theory predicts that the plastic expression of sex-traits should be modulated not only by their production costs but also by the benefits derived from the presence of rivals and mates, yet there is a paucity of evidence for an adaptive response of sex-trait expression to social environment. We studied antler size, a costly and plastic sex trait, and tooth wear, a trait related to food intake and longevity, in over 4,000 male Iberian red deer (Cervus elaphus hispanicus) from 56 wild populations characterized by two contrasting management practices that affect male age structure and adult sex-ratio. As a consequence, these populations exhibit high and low levels of male-male competition for mating opportunities. We hypothesized that males under conditions of low intra-sexual competition would develop smaller antlers, after controlling for body size and age, than males under conditions of high intra-sexual competition, thus reducing energy demands (i.e. reducing intake and food comminution), and as a consequence, leading to less tooth wear and a concomitant longer potential lifespan. our results supported these predictions. to reject possible uncontrolled factors that may have occurred in the wild populations, we carried out an experimental design on red deer in captivity, placing males in separate plots with females or with rival males during the period of antler growth. Males living with rivals grew larger antlers than males living in a female environment, which corroborates the results found in the wild populations. As far as we know, these results show, for the first time, the modulation of a sexual trait and its costs on longevity conditional upon the level of intra-sexual competition. The expression of many sex-traits is plastic and responds to individual-and population-specific reaction norms 1-6. There is evidence for many species that environmental factors (e.g. resource availability) affect body condition and the expression of sex-traits, such as signals and weapons 1,7-11. Condition-dependence theory relies on the relative value of energy costs, because costs of producing traits are expected to be lower for individuals in good condition as compared to those in poor condition 12-15. But also, in a sexual selection context, rivals and potential mates in the social environment strongly influence the benefits associated with trait expression, so that trait investment should respond in a trade-off fashion depending on the costs but also on the benefits of trait development. One example of this in the inter-sexual selection context is that male zebra finches invest more in coloring their beaks when there are females to receive the signal 16. For intra-sexual competition, the challenge hypothesis 2 applied this idea to testosterone production relative to the probability of winning contests, which may be related

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Section: Discussionsupporting

confidence: 90%

Social environment modulates investment in sex trait versus lifespan: red deer produce bigger antlers when facing more rivalry

Carranza

Pérez‐Barbería

Martín

et al. 2020

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“…Antler size is positively correlated with winning fights and mating success (Clutton-Brock et al 1982;Malo et al 2009). In addition to the widely studied antlers, there is another nonpermanent sexual trait in male Iberian red deer: the dark ventral patch (Martín et al 2014;de la Peña et al, 2019;Carranza et al in preparation). The size of this trait reveals the dominance rank and reproductive effort that a male has made in the most recent rutting season (Martín et al 2014;de la Peña et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Immune challenge of mating effort: steroid hormone profile, dark ventral patch and parasite burden in relation to intrasexual competition in male Iberian red deer

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Testosterone secretion may regulate the reproductive effort and the development of sexual traits, but it may also involve costs at the immunological and metabolic levels. However, the evidence for this trade-off in wild populations is scarce. Similarly, cortisol also plays an important role in mediating the reproductive and immune functions. In this study, we analyzed whether the endoparasite burden relates to hormonal levels (fecal testosterone and cortisol metabolites) and/or morphological sexual traits (size of the dark ventral patch, a trait that indicates reproductive effort in males) in male Iberian red deer (Cervus elaphus hispanicus). For this purpose, we sampled male red deer harvested during hunting actions in two types of populations in southwestern Spain that differed in structure affecting the level of male-male competition for mates. We used coprological analyzes to estimate the parasite burden mainly of gastrointestinal and bronchopulmonary nematodes and of protozoa, and assessed testosterone and cortisol metabolite levels from fecal pellets. We found a positive relationship of host parasitation with both testosterone levels and the size of the dark ventral patch, but these relationships depended on the intensity of male-male competition in the population, being only found under the high-competition level. These results are discussed under the hypothesis of the testosterone immunocompetence handicap, suggesting a cost at the immunological level, and, therefore, higher susceptibility to parasite infection in males that make a greater reproductive effort. However, this effect seems to be modulated by the social environment (male-male competition) that might lead to different optima in testosterone production and sexual trait development.

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“…Previous research has shown that, due to the pigmentation mechanism mediated by a urine excretion metabolite of norepinephrine [ 28 ], the dark ventral patch size may contribute to rival assessment during male-male competition as well as reveal the reproductive effort of a male during the current rutting season. In addition, previous studies on the lipid compounds impregnating the hairs of this area show that this character may act as a chemical sexual signal [ 29 ] modulated by the competitive context [ 30 ].…”

Section: Discussionmentioning

confidence: 99%

“…the intrasexual competition level of the population. Previous studies showed that the chemical scent constituents in this trait are mediated by the social environment [ 30 ]. In this work we did not find evidence of the role of male-male competition per se on the dark ventral patch expression.…”

Section: Discussionmentioning

confidence: 99%

“…This dark area is produced by urine [ 28 ] and it is impregnated by great amount of lipidic compounds [ 29 ]. These chemical profiles change with male age [ 28 ] and intrasexual competition situation [ 30 ]. Our own preliminary analyses show that males with larger patches are more involved in the rut and achieve higher mating success than males with small patches [ 31 ].…”

Section: Introductionmentioning

confidence: 99%

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

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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.

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The intensity of male-male competition may affect chemical scent constituents in the dark ventral patch of male Iberian red deer

Cited by 14 publications

References 60 publications

Social environment modulates investment in sex trait versus lifespan: red deer produce bigger antlers when facing more rivalry

Social environment modulates investment in sex trait versus lifespan: red deer produce bigger antlers when facing more rivalry

Immune challenge of mating effort: steroid hormone profile, dark ventral patch and parasite burden in relation to intrasexual competition in male Iberian red deer

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

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