Article Review: Chemical Cues in Spanish Terrapins

Several scientists from the National Museum of Natural Sciences in Madrid, Spain worked together in a study concerning chemical cues in Spanish terrapins. They proposed that chemical cues in the water may help other Spanish terrapins determine characteristics such as body size and health, which is important to choosing/fighting for mates. As both experiments concerned sexual selection, the turtles were captured from the wild during mating season and allowed two weeks to acclimate.

In their first experiment, they allowed an individual turtle to choose from a pool of clean water and a pool of water which came from an individual of the opposite sex. The size of the shell, weight, and health state (determined by immune responses) of both sexes were recorded. When shown the two pools of water from which to choose from, the turtles would often spend time moving in between pools before choosing to spend time in one more than the other. The results show that males spent significantly more time in pools with water from females of a greater immune response/better health. However, body size/weight did not significantly affect the pool the male chose. Therefore, male terrapins must be choosing females based on the presences of “good genes,” which can be indicated by stronger immune response to foreign bodies. Females spent more time in pools with chemical traces from males with larger weights. However, immune response/body size didn't impact their decisions.

In their second experiment, the authors exposed male terrapins to pools of clean water and pools of water from another male. Males were sensitive to chemical cues indicating the weights of other males, as they avoided males with larger masses. This is to avoid male-male competition in which the smaller males would most likely lose.

This article was very interesting, because when I think about reptiles that use chemosensory clues for information about their environment, turtles are not too high on the list. However, it does make a lot of sense that they would have chemosensory ability, as a lot of animals that are aquatic are sensitive to chemical cues. This article increases our knowledge about the family Emydidae, and allows us to understand how turtles modify their behavior according to other members of their species which are living around them. 

Ibanez, A., Lopez, P., Martin, J. 2012. Discrimination of conspecifics' chemicals may allow Spanish terrapins to find better partners and avoid competitors. Animal Behaviour. 83, 1107-1113.