Our animals are becoming so beleaguered that they are learning techniques of self defense. For instance, fish are learning how to locate (and thus avoid) Dead zones. These have long been a source of concern around the world, including in the Baltic Sea, the Black Sea and Chesapeake Bay.

In the United States, the most widely recognized dead zone is in the Gulf of Mexico, where the Mississippi River deposits fertilizer runoff from agricultural regions in the Midwest. These areas became known as dead zones because the accumulation of fertilizers, sewage, and other sources of nutrients generated by humans deplete the oxygen and make them hostile to many life forms.

Dead zones are fish killers. But fish are learning to escape these areas in order to save themselves. It turns out that they pick up a "chemical signature" from them so that they can quickly swim away from them. Environmentalist Karin Limburg says that this "has the potential to revolutionize the way we understand fish interactions with this growing environmental problem." She discovered that manganese, which becomes dissolved in bottom sediments under low oxygen conditions, can be detected by cod. In addition, two other trace elements, strontium and barium, are also taken up sensed by fish in low oxygen environmental conditions.

One critter that knows how to practice a special form of self-defense is the possum, which pretends to "sleep" until predators leave it alone. This has been such a successful strategy that it’s the only living example of a marsupial mammal (one that gestates its young in an outer pouch) that still exists in the US–in fact, it’s one of the most common mammals here, found in all parts of the country. The earliest possums date to the age of the dinosaurs.

In the June 14th edition of the New York Times, Natalie Angier quotes biologist Ines Horovitz as saying, "Every time I see an opossum I get moved. They’ve managed to survive all this time looking the same as their ancestors did 60 million years ago or more."

We sympathize with the fish (but we hope to become as long-lived as the possum)! At unknowncountry.com, we’re not becoming oxygen starved, we’re starved for support from our readers and listeners! Did you know you can subscribe for a month for less than a latte a WEEK? If you want to keep getting our incredible edge news and extraordinary radio shows, you can’t afford NOT to (and we always have something special for our subscribers).

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