How Long Can an Animal Remain Motionless?

Opossums have nothing on cave salamanders. While the American marsupials are famous for playing dead when threatened, they snap back into action relatively quickly. Cave salamanders, on the other hand, can spend much of their lives motionless.

Members of one particularly sedentary species known as olms were "followed" for 10 years in the underwater caves of Bosnia-Herzegovina. During that time, the olms moved less than 32 feet (10 m). In fact, one individual in this less-than-energetic group stayed still for seven years, according to researchers from the United Kingdom and Hungary.

Olms are blind, and when they do move, it's usually to find a mate or food, although they can slow their metabolism to such a sluggish rate that a single meal of shrimp or snails can keep them sated for a decade. As for mating, olms tend to get together only once every 12 years or so. They can live for over 50 years, though one study suggests that their lifespan could be much longer than that.

While olms might not be particularly interesting to watch, scientists say they are useful for evaluating the climate change. "The low reproductive activity of the species, together with the reported extreme site fidelity makes this top predator of aquatic cave communities highly vulnerable and a sensitive bio-indicator of habitat-changing human activities," the researchers reported.

Not so fast: