NS 02-04

The effect of a Genetic Bottleneck on Elephant Seals

    See discussion for Fig 2.3. Northern Elephant Seals (Mirounga angustirostris) underwent a drastic reduction population at the beginning of the 19th century when they were hunted for their blubber: estimates are that there were < 20 individuals by the time protection was introduced in the 1920s. Rookeries such as this one at Año Nuevo Island on the California coast are now protected, and overall seal numbers at several such reserves have increased to >100,000. Observed genetic variation has not recovered to that expected for this population size at equilibrium.

    Recovery of genetic variation in Elephant Seals is further limited by their mating system. Any given rookery is dominated by a single male [above, with prominent proboscis] who guards "harems" comprising almost all of the reproductive females. Non-alpha males father few or none of the pups in the next generation. This reduces the effective population size of the rookery.

Figure ©2013 by Sinauer; Text material © 2021 by Steven M. Carr