Longitudinal changes and consistency in male physical and behavioural traits have implications for mating success in the grey seal (Halichoerus grypus)

Abstract

We examined age-related changes and consistency in physical and behavioural traits of 20 male grey seals (Halichoerus grypus (Fabricius, 1791)) and implications for a proxy of mating success (number of oestrous females attended) over four successive breeding seasons on Sable Island, Canada. Across the study, young males (10-15 years) gained body mass, while old males (23-31 years) lost body mass. Body length was an important determinant of tenure (time spent at a site among females) and males of all ages exhibited a high level of consistency in duration of tenure (r = 0.40-0.50). In young males, our proxy of success showed a strong relationship with arrival body mass and also exhibited a high level of consistency (r = 0.50). None of the physical traits measured explained variation in success by exhibiting mating tactics that did not involve tenure, which is likely due to the opportunistic nature of those tactics. Whereas young male grey seals exhibited age-dependent improvements in success owing to changes in their physical state, later in life physical traits were less influential and suggest that nonphysical traits may compensate for a deteriorating physical state and its impact on male success.Résumé : Nous avons examiné les changements associés à l'âge et la cohérence des caractères physiques et comportementaux de 20 phoques gris mâles (Halichoerus grypus (Fabricius, 1791)) et leur signification en ce qui concerne une variable substitutive du succès d'accouplement (le nombre de femelles en oestrus accouplées) pendant quatre saisons de reproduction successives dans l'île de Sable (Canada). Durant l'étude, la masse corporelle des jeunes mâles (de 10 à 15 ans) a augmenté alors que celle des vieux mâles (de 23 à 31 ans) a diminué. La longueur du corps était un important déterminant de la rési-dence (le temps passé en un lieu parmi des femelles) et les mâles de tout âge présentaient un degré élevé de cohérence relativement à la durée de la résidence (r = 0,40 à 0,50). Chez les jeunes mâles, notre variable substitutive de succès présentait un fort lien avec la masse corporelle à l'arrivée ainsi qu'un degré de cohérence élevé (r = 0,50). Aucun des caractères physiques mesurés n'explique les variations du succès découlant de tactiques d'accouplement ne comprenant pas la résidence, ce qui est probablement attribuable au caractère opportuniste de ces tactiques. Si les jeunes phoques gris présentent des améliorations du succès qui dépendent de l'âge en raison de changements à leur état physique, l'incidence des caractères physiques est moins importante à des âges plus avancés, ce qui porte à croire que des caractères non physiques pourraient compenser la détérioration de l'état physique et son impact sur le succès des mâles.

Individual size, sex, and rearing environment impact on aggression in newly weaned seals

“…This could be an early expression of behavioral strategies seen in adults, as an adult male's size, dominance ranking, and aggression frequencies have been linked to each other and to mating success in several phocid species (gray seals: Anderson and Fedak , Godsell , Lidgard et al . ; harbor seal: Sullivan ; southern elephant seal, Mirounga leonina : McCann , Modig ; northern elephant seal, Mirounga angustirostris : Haley et al . ).…”

“…In our study group, male weaned pups showed more aggression the larger they were compared to other individuals. This could be an early expression of behavioral strategies seen in adults, as an adult male's size, dominance ranking, and aggression frequencies have been linked to each other and to mating success in several phocid species (gray seals: Anderson and Fedak 1985, Godsell 1991, Lidgard et al 2012harbor seal: Sullivan 1982;southern elephant seal, Mirounga leonina: McCann 1981, Modig 1996; northern elephant seal, Mirounga angustirostris: Haley et al 1994). However, the males in our study were approximately 8 yr away from the age they would typically first be able to hold tenure on a breeding colony (Godsell 1991).…”

Macro-evolutionary trade-offs as the basis for the distribution of European bats

“…Each individual strives to contribute to the future generation, but reproduction has its costs: the energy and nutrient demands of reproducing are large. Furthermore, morphological changes are needed to better meet these demands (e.g., Cockbum, 1989;Lidgard et al, 2012). In each matemity roost only between 50-90% of females participate in reproduction, because some females need a recovery year after successful reproduction (Ransome, 1995;Barclay et al, 2004).…”

Age–length relationships in UK harbour seals during a period of population decline

“…Comparing morphometric measures, such as maximum body length and juvenile growth rates, can therefore assist in understanding how nutritional and food-related constraints may be impacting populations. Indeed, for pinniped species with polygynous breeding systems and large degrees of sexual dimorphism, attaining maximum body length may be particularly important for males where size is related to mating success (Lidgard, Bowen, & Boness, 2012). Indeed, for pinniped species with polygynous breeding systems and large degrees of sexual dimorphism, attaining maximum body length may be particularly important for males where size is related to mating success (Lidgard, Bowen, & Boness, 2012).…”