Oil to wipe out gulf whales
Ker Than
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 US 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," an environmental toxicologist at Texas Tech
University Celine Godard-Codding.
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."
Oil spills can affect sperm whales and other cetaceans, including
dolphins, in a number of ways.
For starters, the marine mammals have to surface to breathe, and if
they come up through an oil slick, they can suck the toxic substance
into their lungs.
Also, the fumes on the surface of the water after a recent spill can
be powerful enough to knock out full-grown whales, causing them to
drown.
Finally, the oil can taint the toothed whales' prey-fish and
squid-affecting the whales' diets and hurting their chances of raising
healthy calves.
"The chemicals in the oil product that move up through the food web
are a great concern for us," said Teri Rowles, coordinator of NOAA's
marine-mammal health and stranding response program.
Previous studies have shown that at least some of the Gulf of Mexico
sperm whales are known to hang around where the Deepwater Horizon oil
rig was located before it exploded on April 20, triggering the spill.
"Between 2000 and 2005, about 300 (sperm) whales were seen on a
consistent basis right in that area," Texas Tech's Godard-Codding said.
Some experts worry that the Gulf oil spill could be as damaging to
sperm whales as the 1989 Exxon Valdez oil spill was to killer whales in
Alaska's Prince William Sound. 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.
- National Geographic News
|