Antlers honestly advertise sperm production and quality (original) (raw)
Related papers
Revisiting the allometry of antlers among deer species: male–male sexual competition as a driver
Oikos, 2010
The positive allometry between antlers and shoulder height reported for cervids has previously been interpreted as resulting from a high male‐male competition in large species that form large breeding groups. We aim at revisiting relative antler size variation among deer species by including more species (n = 31) and by testing both direct and indirect influences of different sexual selection proxies on the relative antler length using path analysis. The absence of direct effect of mating tactic on relative antler allometry indicates that the strength of fights does not differ among mating tactics. On the other hand, the main effect of breeding group size is revealed by polygyny. Highly polygynous species have relatively longer antlers than less polygynous ones but the difference in the relative effect of breeding group size on relative antler length is weak. Strong direct effect of breeding group size and indirect effect of mating tactic shaped the observed variation in the relativ...
The Journal of animal ecology, 2018
To secure mating opportunities, males often develop and maintain conspicuous traits that are involved in intrasexual and/or intersexual competition. While current models of sexual selection rely on the assumption that producing such traits is costly, quantifying the cost of allocating to secondary sexual traits remains challenging. According to the principle of allocation, high energy allocation to growth or sexual traits in males should lead to reduced energy allocation to the maintenance of cellular and physiological functions, potentially causing them to age faster, with impaired survival. We evaluated the short-term and delayed consequences of energy allocation to antlers early in life in two contrasted populations of roe deer, Capreolus capreolus. Although most males mate successfully for the first time in their fourth year, antlers are grown annually from the first year of life onwards. We tested the prediction that a high level of allocation to antler growth during the first ...
The aim of this study was to use for the first time molecular techniques (microsatellite genotyping and paternity analyses), in combination with field ecology studies, to provide data on male breeding success and identify the main determinants of variation in male breeding success in two long-term monitored populations of European roe deer Capreolus capreolus (Bogesund in Sweden and Trois Fontaines in France). The results show that males can sire up to 6 fawns per year and 14 fawns during their entire lifetime. As expected from the low level of sexual size dimorphism and the territorial mating system of roe deer, variance in male lifetime breeding success, and so opportunity for sexual selection, are lower than in highly dimorphic species such as red deer Cervus elaphus, suggesting a low polygyny level in roe deer. Males can successfully breed as young as 2 years of age, but breeding success of sub- adults is lower than that of older males. Successful breeding among sub-adults may be restricted to those high quality males that are able to defend a territory. Breeding success also tends to decline after 8 years of age (senescence), probably in relation to the loss of dominance. Male body mass and antler size positively affect male breeding success. It is known that antlers are used by males as a weapon in combats to defend their territory. However, my results also show that antler size is a honest signal of male phenotypic quality and may be used as a cue for rival males and females to assess male fighting ability, sexual vigor and/or phenotypic quality. In addition, male access to females and male breeding success are positively related to territory size, but not to habitat quality within a male’s territory. Hence, the territorial mating system of roe deer differs from the conventional resource defense polygyny system and seems rather to conform to a “low risk – low gain” strategy. Finally, using paternity analyses, I also provide evidence that multiple paternity is likely, but infrequent, in roe deer, suggesting that multiple mating among females may have evolved as a means to enhance fertilisation success. This study provides new insights into the evolution of mating systems and sexual selection in ungulates.
Antler Size Provides an Honest Signal of Male Phenotypic Quality in Roe Deer
The American Naturalist, 2007
Identifying factors shaping secondary sexual traits is es- sential in understanding how their variation may influence male fitness. Little information is available on the allocation of resources to antler growth in territorial ungulates with low sexual size dimor- phism. We investigated phenotypic and environmental factors af- fecting both absolute and relative antler size of male roe deer in three contrasting populations in France and Sweden. In the three populations, we found marked age-specific variation in antler size, with an increase in both absolute and relative antler size between yearling and prime-age stages, followed by a decrease (senescence) for males older than 7 years. Antler size increased allometrically with body mass. This increase was particularly strong for senescent males, sug- gesting the evolution of two reproductive tactics: heavy old males invested particularly heavily in antler growth (potentially remaining competitive for territories), whereas light old males grew small antlers (potentially abandoning territory defense). Finally, environmental conditions had little effect on antler size: only population density negatively affected absolute antler size in one of the three populations. Antler size may therefore provide an honest signal of male phenotypic quality in roe deer. We discuss the implications of these results in terms of territory tenure and mating competition.
The dark ventral patch: A bimodal flexible trait related to male competition in red deer
PLOS ONE
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 tr...
Testosterone and the dark ventral patch of male red deer: the role of the social environment
The Science of Nature
The expression of male sexual traits, which is stimulated by testosterone, entails significant costs for individuals. Consequently, natural selection is expected to favour the modulation of sexual trait development according to the balance between its costs and benefits. The proportion of rivals in a population may affect this balance by increasing or decreasing the reproductive benefits associated with the development of sex traits. Here, we explore the relationship between testosterone level and sex trait size under two populational conditions of mate competition: fenced (i.e. high male-male competition; all male age groups are present) and unfenced (i.e. low competition; most males present are juveniles). Our model species is the Iberian red deer (Cervus elaphus hispanicus), and the sex trait is the dark ventral patch that males exhibit during the rutting season. Our results showed that the positive relationship between testosterone levels and the size of the dark ventral patch depends on the environmental level of male-male competition. Only in populations where the operational sex ratio was high (i.e. high proportion of rival males), individuals with high levels of testosterone developed the sex trait. Conversely, when mate competition was low, there was no significant relationship between testosterone level and trait size. This result reinforces the idea that the effect of testosterone in promoting the development of sex traits may be mediated by the intensity of mate competition in the population, as well as the role of sexual selection in the evolution of the dark ventral patch in red deer.
Biology of Reproduction, 2013
Sperm design and velocity play key roles in influencing sperm performance and, therefore, can determine fertilization success. Several interspecific studies have demonstrated how these features correlate, and it has been hypothesized that selection may drive changes in these sperm traits. Here, we examine the association between sperm design and swimming velocity in a study conducted at an intraspecific level in Iberian red deer (Cervus elaphus hispanicus). We addressed how the structure of different sperm subpopulations, based on sperm morphometry and velocity, are interrelated and, in turn, how they associate with fertility. Our results show that males with high fertility rates have ejaculates with high percentages of spermatozoa exhibiting fast and linear movements and that these are highly correlated with a large proportion of spermatozoa having small and elongated heads. On the other hand, males with low fertility are characterized by a subpopulation structure in which slow and nonlinear as well as small and wide spermatozoa are predominant. These findings provide insight regarding how sperm size and velocity are interrelated and how they both are associated with fertility. ejaculate heterogeneity, fertility, sperm, sperm length, sperm size, sperm subpopulations, sperm velocity
Scientific Reports
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.
Fluctuating asymmetry (FA) has been suggested as a measure of the sensitivity of development to a wide array of genetic and environmental stresses. It has been also suggested that antlers in red deer could be important during social and rutting displays. We used antler measurements of 51 males that were measured over subsequent seasons, from 3-8 years of age, and analysed three antler traits: antler weight, length, and the number of antler tines (antler size). We calculated absolute and relative FA. All three size traits were highly significantly intercorrelated. By contrast to this, the FA of the three traits, did not show such relationships. With increasing age, antler size and FA also increased. When testing the repeatability of FA and antler size, there was a principal difference in the pattern between FA and antler size, with the latter being much more consistent than the former. This suggests that antler size, not FA, may be a good predictor of the bearer's quality in mate selection. This fits well with the good-genes hypothesis that the development of extravagant secondary sexual characters can be an honest advertisement of heritable male quality.
No evidence for a trade-off between sperm length and male premating weaponry
Journal of evolutionary biology, 2015
Male ornaments and armaments that mediate success in mate acquisition and ejaculate traits influencing competitive fertilization success are under intense sexual selection. However, relative investment in these pre- and postcopulatory traits depends on the relative importance of either selection episode and on the energetic costs and fitness gains of investing in these traits. Theoretical and empirical work has improved our understanding of how precopulatory sexual traits and investments in sperm production covary in this context. It has recently also been suggested that male weapon size may trade off with sperm length as another postcopulatory sexual trait, but the theoretical framework for this suggestion remains unclear. We evaluated the relationship between precopulatory armaments and sperm length, previously reported in ungulates, in five taxa as well as meta-analytically. Within and between taxa, we found no evidence for a negative or positive relationship between sperm length...