I linked to a story yesterday about Inuit hunters in Alaska who caught a bowhead whale last month and began to carve up the carcass when they came across a harpoon tip inside the whale that was only used between 1885 and 1895, making that particular whale at least 115 years old, if not older. Indeed scientists in 1999 examined another bowhead whale and placed its age at 211 years.
So what is the secret of their longevity? Carl Zimmer explores this idea in an essay in the New York Times, and it boils down to reproductive strategies. Species that are under threat, either from carnivores or their punishing environment, tend to live quickly and reproduce like well, rabbits. Rapid reproduction leads to accelerated metabolisms and shortened life spans, but their prolific fecundity ensures the survival of the species. However, bowhead whales evolved with little competition in their environment and minimal pressure from carnivores, so they could devote their metabolic resources to individual growth and health. They take two decades to mature and produce a single offspring every seven years, a stately pace for reproduction that served the whales well for millenia.
Zimmer makes the point that this long lived lifestyle ran into a crisis a century ago. Large scale whaling brought the bowhead population to the brink of extinction and now, a century after commercial whaling ceased on bowheads, their numbers are still scant. They are still considered a threatened species because they reproduce so slowly. He mentions studies done on fruit fly populations where scientists killed off vast amounts of the flies, the population reached sexual maturity faster and consequently shorten the flies’ lifespans. I wonder if we have done the same thing to bowhead whales?