Oil spill may wipe out Gulf sperm whales — Just three dead whales could push the Gulf population over the edge
By Ker Than
for National Geographic News
Published May 21, 2010 If the Gulf of Mexico oil spill kills just three sperm whales, it could seriously endanger the long-term survival of the Gulf’s native whale population, scientists say. Right now between 1,400 and 1,660 sperm whales live year-round in the Gulf of Mexico, making up a distinct population from other Atlantic Ocean groups, in which males make yearly migrations. All sperm whales are considered endangered under the U.S. Endangered Species Act. But the Gulf of Mexico population is thought to be especially vulnerable due to its relatively small size. The whales are now at risk from the ongoing Deepwater Horizon oil spill, because they are likely to ingest or inhale toxic crude and noxious oil fumes. “We know there’s going to be some [oil] exposure, and we know there’s an endangered species. If you put those two thing together, there is reason for concern,” said Celine Godard-Codding, an environmental toxicologist at Texas Tech University. A 2009 stock assessment report by the National Oceanic and Atmospheric Administration (NOAA) estimated that the potential biological removal, or PBR, level for the Gulf of Mexico sperm whale population is three. That means the whales’ long-term survival is at risk if, in addition to natural deaths, three sperm whales a year are killed or removed by human causes. The loss of a handful of whales each year can impact a population of hundreds, because sperm whales—especially females—require a very long time to reach sexual maturity. Females then give birth to just three or four calves during their entire lifetimes. “They’re like humans. Most of the human population is not going to have six kids at once and do that every year,” Godard-Codding said. “As soon as we get to the level of three deaths caused by human interaction—and this would include the oil spill—that would jeopardize that particular sperm whale population.” … After the Exxon Valdez disaster, some populations of killer whales were reduced by as much as 40 percent, according to a 2008 study led by marine biologist Craig Matkin of the North Gulf Oceanic Society in Alaska. Even now, that killer whale population has yet to recover and will likely go extinct in a few decades, Matkin said. “We lost so many females out of that group that they couldn’t catch up again. They still haven’t caught up,” he said. If the current oil spill causes more than three Gulf sperm whale deaths this year, it could push that group into the “red zone,” Matkin said. …
