Researchers analyzed both mitochondrial DNA, which is inherited exclusively from the mother, and microsatellite genotypes, which are inherited from both parents, from 490 whales involved in 12 stranding events. Contrary to the hypothesis that stranding groups consist of whales descended from a single ancestral mother (the "extended matriline" hypothesis), multiple matrilines were found in the groups stranded together.
In some strandings, the researchers assessed the spatial relationships of individual whales on the beach. The position of each stranded whale was mapped to determine if individuals found near each other were related. No correlation was found between location and kinship, even when considering only the location of nursing calves and their mothers, who were often widely separated when the group drove itself onto the shore.
Most surprising was the evidence of "missing mothers" that is, many of the stranded calves and juveniles had no identifiable mother among the other beached whales.
"Several scenarios could account for the lack of spatial cohesion, including the disruption of social bonds among kin before the actual strandings," commented Oremus. "In fact, the separation of related whales might actually be a contributing causal factor in the strandings, rather than simply a consequence."
The results of this study have important implications for rescue efforts aimed at "refloating" stranded whales. "Often, stranded calves are refloated with the nearest mature females, under the assumption that this is the mother," explained Sco
|Contact: Nancy Steinberg|
American Genetic Association