dolphins

If you haven't seen whale trackers, it's a very cool documentary series about whales, dolphins and porpoises and the international scientists researching them.

One of the current series follows scientists in the northern gulf of California (the Sea of Cortez) this month as they follow the rare vaquita marina, or desert porpoise.

The vaquita, dubbed the desert porpoise because their strip of ocean is wedged between the deserts of Northwestern Mexico and Baja California, is the most critically endangered of all cetaceans, and what few are left (an estimated 150 individuals) are caught as bycatch by local fishermen's nets, particularly gillnets.

You can read more about the expedition and watch the vaquita video -- check it out.

And while you're at it, you can watch another episode, "Fishy Business," about illegal driftnet fishing in the Meditteranean. The episode features the work of the Oceana Ranger in Europe and an interview with Oceana's Xavier Pastor.

A new report looks at the effects of increased ocean acidity on how sound travels in seawater, which scientists have long suspected to be influenced by pH.

The report found that drops in pH affect the ocean's chemical balance and consequently lower its sound absorption, especially to frequencies below 10 kilohertz (kHz). The researchers say that by the 1990s, the oceans absorbed 15% less sound than during the previous century, which will likely affect the communications of ocean wildlife as well as military operations, by making sound travel farther and increasing the ocean's ambient noise level. Already, scientists have discovered that blue whales, which normally communicate below1 kHz, have started calling at lower frequencies.

The most thorough assessment of land and marine mammals in 12 years, just published in Science, says that a quarter of the world's wild mammal species are at risk of extinction.

It took nearly 2,000 experts in more than 100 countries five years to complete the research. In other words: this one's big, and ought to be paid some serious attention.

While land mammals are most threatened by habitat loss and hunting, marine mammals are more in danger from bycatch, ship strikes and pollution.

A wild dolphin in south Australia has been teaching members of her group to walk on their tails, a behavior usually seen only after training in captivity.

Scientists are scratching their heads -- why would the dolphins do this?

Well, one of the female dolphins, Billie, could have learned the behavior by observation during her brief stint in a dolphinarium.

Or they might be watching too much Olympic gymnastics. Plus, it just looks like fun.