SCIENCE LAB SCARCE : PORPOISES

Battling Extinction

Trying to keep 10 porpoises from shrinking down to zero.

The vaquita, a porpoise from Mexico with pandalike eyes, is one of the world's most endangered animals. ONLY about 10 remain.

But now there's some good news about their chances for survival. When species dwindle, scientists worry that inbreeding can doom them to extinction. But that's not true for vaquitas, according to research published in the Journal Science.

Their DNA, it turns out, has a surprising advantage. By sequencing the genomes of 20 animals across about three-generations, researchers found their genes to be surprisingly free of mutations that would threaten the vaquita through inbreeding.

''Despite the small numbers, the species could recover if we stopped killing them,'' said Lorenzo Rojas-Bracho, one of the study's authors. What's killing vaquitas?

A kind of fishing gear, called gill nets, that accidentally traps and drowns them. The nets are prohibited in much of the vaquita's habitat, but the Mexican authorities haven't enforced the ban.

To predict extinction, researchers used computer models that combined the genetic findings with other factors, such as birthrates. The results were clear : Vaquitas are very likely to survive if fishing deaths are stopped - but only if stopped entirely.

Even reducing the fishing deaths by as much as 80 percent would still lead to a 62 percent chance of extinction. [Catrin Einhorn]