Iguanas Die to Find Mr. Right

A territorial male marine iguana surrounded by visiting females. Credit: Martin Wikelski

Male (top) and female Galapagos marine iguanas. Credit: Martin Wikelski

Mating pair of Galapagos marine iguanas. Credit: Martin Wikelski

Decisions, decisions. Picking a mate from a long line of suitors is an exhausting process for a female iguana. In fact, it can really kill her.

Scientists have generally assumed that being choosy about a mate carried a low cost for female animals, particularly when those males roam territories that are tightly clustered into groups called leks, because the females don’t have to travel very far to check out their prospects.

But the female Galápagos marine iguana spends a lot of energy choosing her mate, even though all she seems to get from the effort is better genetic material for her young. And visiting the more “attractive” males that provide this high-quality DNA (those that display more often) carries the highest costs in energy for the female because she can lose more weight and therefore produces smaller eggs.

Low body weight can decrease the female’s chances of survival. During El Niño years, marine iguanas have a hard time finding food, so those who start at a low weight are less likely to survive the season.

Further research is needed to determine whether the genetic material the female gets outweighs the costs she pays for finding Mr. Right.

The new study is detailed in the June 27 issue of the online journal PLoS ONE.

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