Resumen del producto

Kin structure and parentage studies in baleen whales are rather scarce, largely due to the difficulty to of obtaining large samples of individuals in these species. In this study we combined long term (1988-2009) photo-identification data with genetic data to investigate kinship and parentage of blue whales, Balaenoptera musculus, in the Gulf of California, a likely breeding ground of the species. We used 172 photo-identified and biopsy sampled individuals, which were analyzed with nine microsatellite loci. We determined the level of kinship using the Coancestry 1.0 software, which implements five kinship estimators. We performed Monte Carlo simulations to calculate correlation coefficients between the kinship estimators and the expected values in a panmictic population to assess the goodness of fit. We carried out a parentage analysis with the Parente software, which permits to use the individuals age as supplementary information in offspring assignment. Sexual maturity was considered at 5 years of age. We found 78 kin groups, composed by 3 to 11 individuals (mean=4.9, SD=1.9), with a clear bias towards females. Most groups (65.4%) were composed by 1 to 7 kin pairs (mean=2.1, SD=1.4). Most kin pairs involved females (first and second order relatives: n=18), followed by mixed-pairs (second order relatives: n=16, and third order relatives: n=11). Also male kin pairs were observed (n=8). Groups of unrelated individuals were mostly (74%) composed by a mix of adult males and females. We observed 34 mother-calf pairs in 23 groups. In 14 of these groups, we found second or third order relatives of the mother or the calf. We found 32 pairs, 6 of which were relatives (2 female pairs, 4 mixed pairs). These results suggest that both females and males may get inclusive fitness benefits by forming associations. Six fathers were assigned to 8 calves; three at 50%, two at 60 and 70% respectively and one at 90% probability. All of them were first-order relatives. Two fathers were sighted the year before of their calf’s birth, suggesting the southwestern Gulf of California may be an established breeding ground for this species.

Palabras clave: Ballena azul; distribución vertical; Associacion de parentesco

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