GREEN
04/24/2010 05:12 am ET Updated May 25, 2011

Peru Poison Frog Is Monogamous, For One Reason Only

Genetic tests have revealed that male and females of one species of Peruvian poison frog remain utterly faithful.

More surprising is the discovery that just one thing - the size of the pools of water in which they lay their tadpoles - prevents the frogs straying.

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