Elephant seals are having more and more pups on the California coast, which is a good sign -- sort of. The hulking marine mammals, once on the brink of extinction, have boosted their numbers in recent years. But a high birth rate isn't the only indicator of population success; it's also not the only population measure that's going up right now, according to a new report:
About 5,300 elephant seal pups were born in the rookery at Piedras Blancas this year, up 2.5 percent from last year, but the survival rate was lower than last year. Brian Hatfield, the marine biologist who counts them, bases the number of pups born on the number of adult females on the beach, assuming that each one will have one pup. (No one has ever observed twins being born.)
When the birthing is over, he counts live pups, including those that have been weaned, and orphaned pups. That number was about 4,500, a loss of 15.5 percent of those born. Last year, births were up 4 percent from the year before, and the mortality rate was only 7 percent.