Male reproductive success and its behavioural correlates in a polygynous mammal, the Galápagos sea lion (Zalophus wollebaeki)

Abstract

Sexual selection theory predicts competitive males and choosy females. Nevertheless, since molecular marker-based studies, paternity outside the expected mating patterns has increasingly been described. Even in highly polygynous systems, where paternity is expected to be strongly skewed towards large, dominant males, alternative mating tactics have been suggested. We examined reproductive success in the polygynous Galápagos sea lion (Zalophus wollebaeki). Semiaquatic territoriality allows females to move freely and may lower the degree of polygyny otherwise suggested by both territorial behaviour and strong sexual dimorphism. We assigned paternities with 22 microsatellites and analysed how male reproductive success was related to size, dominance status, intra-sexual agonistic behaviour, proximity to females, and attendance in the colony. Male behaviour was consistent across two seasons for all parameters under consideration. Attendance was by far the most important determinant of paternal success. Skew in reproductive success towards large, dominant males was weak and dominance status played no role. This appears to be caused by an extremely long reproductive season lasting five or more months, making it difficult for any male to monopolize receptive females. Females seem to choose displaying males that were present in the colony for a long time rather than dominance per se. Sexual dimorphism in Galápagos sea lions may thus be more influenced by selection for fasting than fighting ability. Our data provide further evidence for alternative mating tactics, as several males gained relatively high reproductive success despite short attendance and hardly any involvement in agonistic interactions.

Divergent allele advantage at MHC-DRB through direct and maternal genotypic effects and its consequences for allele pool composition and mating

“…In previous work, we have shown that male behaviour influences paternity success [33]. From the individuals investigated in 2006 and 2007, we here took a subset for which we now had obtained MHC-DRB genotypes (100/146) and rerun their best model (table 3 in [33]).…”

Proximity loggers on amphibious mammals: a new method to study social relations in their terrestrial habitat

“…We conducted 2 to 3 daily resight rounds (between 05:00 and 18:00 h), noting the presence of each male identified from numbered tags, permanent characteristics or bleach marks. In total, we observed 227 individually identified adult males (≥5 yr old; Pörschmann et al 2010). In addition to the ID of a focal male, we recorded the ID of its closest associates.…”

Applicability of Single-Camera Photogrammetry to Determine Body Dimensions of Pinnipeds: Galapagos Sea Lions as an Example

“…In polygynous species, male reproductive success is expected to increase with male body size and mass ([5],[6]) which have been selected for increased fasting ability ([2],[7]) or advantages in intra-sexual competition for access to females ([8],[9]). Furthermore, body length and mass have been used as indicators to assess habitat quality (e.g., [10]) as an individual’s body condition provides information about the quantity and quality of resources in a habitat (e.g., [11], [12]).…”