4 Animals That Change in Captivity

Put a wild animal in a cage, and it’s bound to act differently. Zoologists and vets have many strategies to help an animal get settled and normalize its behavior in captivity. Psychological changes can be overcome with animal enrichment programs that keep creatures entertained and mentally stimulated—but some of the internal and physical changes in these four animals are more difficult to tackle.

1. Koalas

Image courtesy of jsteel's Flickr stream.

While some animals eagerly engage in free love (deep sea squid, bonobos, and penguins have all been found to have bisexual tendencies), koalas are a more conservative bunch. These eucalyptus-munching marsupials are strictly heterosexual—at least in the wild. Once in captivity, female koalas participate in lesbian orgies. According to scientists at the University of Queensland, who monitored 130 koalas using digital cameras, female koalas in captivity engage in homosexual acts three times as often as they participate in heterosexual activities. The orgies often include up to five females at a time. (They don’t count the males out, though: The females' heterosexual activities lasted twice as long as their homosexual encounters.)

Scientists remain uncertain about the cause of these encounters. Some believe that female koalas use the orgies as a method of attracting males, while others think it’s a hormonal behavior. Still others believe it serves to release stress.

2. Komodo Dragons

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Don’t get bitten by a wild Komodo dragon: Their mouths contain 57 septic pathogens including e. coli and Staphylococcus which, according to some scientists, cause horrible infections in the creatures’ victims. (Lucky for the dragons, they’re immune to all the bacteria.) Once in captivity, however, Komodo dragons lose their filthy mouths thanks to cleaner diets and antibiotics which kill the pathogens.

Why give Komodos antibiotics when they’re immune to the bacteria? Once taken from the wild, the dragons are highly susceptible to infection and disease. This may be because the animals have a lower core temperature in captivity, but no one knows for certain.

3. Poison Dart Frogs

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The bright color of a poison dart frog’s skin is a loud warning: Don’t touch me! The poison secreted by these paper-clip-sized amphibians is so deadly that indigenous tribes in South America coat their hunting darts with it. (According to National Geographic, the Golden poison dart frog has enough venom to take out 10 men.) But the frogs generally stop being poisonous once removed from the wild .

As with the Komodo dragon, this change comes down to diet. Poison dart frogs derive toxins from what they eat: Some get their poison from ants, others from beetles, a few from spiders. The toxins are collected in glands in the frogs’ skins and secreted through it, which is what makes them poisonous to the touch. It’s practically impossible for zookeepers and others who take care of the animals to obtain these toxic food sources.

Frogs taken from the wild can hold on to their poison for a long time, sometimes years. But eventually they lose their toxicity, and captive bred frogs will never become poisonous (unless, of course, they’re fed the specific insects that result in that species’ toxicity).

There is one exception to this no-toxin rule: Australia’s corroboree frog, the only species known to produce its own poison rather than deriving it through diet. These creatures maintain their poison no matter how many generations are raised in captivity—a very good thing because captive breeding and eventual release into the wild is the only hope of survival for the critically endangered frogs.

4. Japanese Fire Belly Newts

Image courtesy of Eric Michon's Flickr stream.

Like poison dart frogs, these newts are highly toxic in the wild; they secrete Tetrodotoxin, a neurotoxin for which there is no antidote. But in captivity, the animals may lose their toxicity. The key word here is “may”: Some newts born in captivity actually hold on to their poison instead of losing it. While scientists are unclear about the reason for this occasional biological change, many speculate that the animal’s toxicity is formed through contact with an environmental bacteria that is sometimes, but not always, passed to the next generation.