It would seem logical that in nature females tend to choose the most attractive male, which could mean many things including the best looking or the best sounding. This is indeed usually true when it comes to mating in living organisms but a new study shows this may not always be the case. This study on tungara frogs suggests that females may not always make the best decision in the presence of three or more males competing to mate with her.
The selection of attractive males by females is described by the theory of sexual selection. It was originally put forth by Darwin to explain why bright coloured animals can exist in nature. Bright animals initially posed a threat to Darwin’s theory because they should be easily captured by prey and thus shouldn’t live to mate and pass on their genes. This dilemma had a simple solution: females are attracted to bright males so while predation was pushing towards dull males, sexual selection was pushing towards brighter males. Since evolution was first put forth, examples of sexual selection have been found in many plants and animals and extends beyond just exterior characteristics.
The theory of sexual selection has been successful in explaining a wide variety of adaptations in animals including mating calls in frogs. Generally long, low frequency calls are favoured by females but according to biologists from the University of Texas this may not always be the case.
In the study, 80 females frogs were first allowed to choose a mate between two males. One had a favourable low frequency call while the other had a less favourable call. In this part of the study, females almost always choose to go with the ‘good’ call. This was no surprise. However, things got interesting when a third, less than suitable male was introduced. When the females went to choose a mate, more often than not, they would choose the non-suitable male. This behavior cannot be explained by the theory of sexual selection.
It seems that when females are given many options, they became overwhelmed and made poor decisions when it came to choosing mate. This study shows that the theory of sexual selection may not always be suitable when describing mate choice in complex social situations. The reason for this irrationality may happen because choosing a good mate from a large group may be time consuming and ultimately cost the female precious mates.