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Female Túngara Frogs Mate Irrationally When Presented With Too Many Male Candidates

Aug 28, 2015 04:11 PM EDT
Male túngara frog
Male túngara frogs, one of which is pictured here, attract females with their calls. While females are often attracted to calls of low frequency and long duration, the "decoy" affect may throw them off.
(Photo : Amanda M. Lea)

When it comes to selecting a mate, female túngara frogs seem to get overwhlemed when there are too many options – at least that's what behavioral biologists from the University of Texas have determined. What they expected in conducting their study involving 80 female túngara frog subjects was that each would adhere to the theory of "rational choice" and select the more "attractive" and "suitable" potenial mate from among several choices. In the case of túngara frogs, suitably attractive males are defined as those capable of making low frequency mating calls of long duration.

And while that was precisely the case when the female frogs were allowed to chose between two potential mates, the introduction of a third proved overwhelming. Many of the female frogs in the study became susceptible to what researchers subsequently labeled the "decoy" effect, where the introduction of a third, inferior potential mate actually influenced a "bad" choice – the selection of the less cable male from among the first two candidates.

According to a news release, scientists identified three different mating call variants and measured female preference for each one. The study showed that even though call B (Mr Right) was the preferred choice over call A (Mr Wrong), females were much more likely to choose call A in the presence of a third potential mate, the so-called decoy. This effect occurred whether the decoy call was perceived as coming from a specific location or a spot that was indiscernible to the female.

Overall, the study results contradict the "rational choice" models that define sexual selection theory and reveal the influence that context plays on choosing a mate: that within socially complex situations, female frogs tend to make irrational decisions, perhaps due to time concerns – fear of losing a mating opportunity and of exposure to predators. 

Since the decoy effect has been observed in humans, these findings from female túngara frogs support the idea that irrationality as the result of being presented with too many choices may have deep biological roots.

This study was recently published in Science.

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