For starters, lemmings—mouse-like rodents that live in tundras of North America and northern Europe—don't kill themselves on purpose.

Gordon Jarrell , a retired biologist at the University of Alaska Museum of the North in Fairbanks, says the myth may have its roots in the animals' cyclical population booms, which are driven by factors such as food availability. (Also see " Animal Myths From Around the World .")

In Sweden and Finland, these springtime spikes push lemmings to disperse from the mountains in search of better accommodations, a journey described by National Geographic magazine in 1918.

When lemmings encounter water bodies, some are jostled into swimming, Jarrell says, and, being unable to swim far, "huge numbers wash up on the beaches."

As for the migrating lemmings that avoid a watery death, they often survive and produce colonies for a few years "where you wouldn't ordinarily find lemmings," he adds—quite the opposite of self-destructive.

A 1958 Disney nature documentary, White Wilderness, also reinforced the suicidal myth by fabricating scenes of lemmings leaping to their deaths, according to the Alaska Department of Fish and Game .

Can you teach old dogs new tricks?

Yes, says Tami Pierce , a veterinarian at the University of California, Davis. This notion may have arisen because older dogs can have medical conditions such as arthritis that cause chronic pain, making them appear less willing to engage.

Since dogs also lose cognitive function as they age, Pierce actually recommends that owners teach their older dogs new tricks through positive, reward-based training—it helps stimulate their brains. (See " Do Animals Get Dementia? How to Help Your Aging Pet .")

Do ostriches hide their heads in the sand?

This myth may stem from a strategy ostriches use to avoid predators, Rosalina Angel , a bird expert at the University of Maryland, College Park, says by email.

If these big birds anticipate a threat, they'll lay down with their heads flat, making their round, dark bodies appear like a bush—and not a tasty meal. To some people, this may have seemed like the African native was putting its head in the sand.

Ostriches are experts at camouflage: Black-feathered males lay on the eggs at night, and the brownish-gray females, which blend into the sand, take over during the day.

Do cats always land on their feet?

There's some truth to this one. Even month-old kittens typically land upright, but "not all cats develop at the same rate, and not all cats get it right each time," Natalie Waran , a veterinarian at the University of Edinburgh in Scotland, says via email. (Watch video: " A Cat's Nine Lives .")

Cats have a self-righting mechanism regulated by a part of their inner ear that triggers the head, neck, and body to rotate into "the appropriate landing position," Waran says. Flexing their backbone also helps absorb the impact of landing.

View Images Cats (such as this leaping British blue) have a built-in mechanism that allows them to usually land on their feet. But they can still be injured, experts caution. Photograph by Stephen Dalton, Minden Pictures/Corbis

"High rise syndrome," first reported by the American Medical Center , is a phenomenon in which cats fall from apartments onto the ground with a surprisingly high survival rate.

However, these fallen felines can experience serious injuries, according to research studies.

So your cat may be remarkable—but it's not unbreakable.