When it comes to finding mates, that privilege is usually saved for the biggest, strongest, smartest, and whatever other positive adjective you might think of to describe the “perfect mate.” But that leaves you to wonder, what about those who aren’t necessarily the best at what they do, but still find a way to mate? The answer is simple: they’re the cheaters! The saying goes that “cheaters never win,” but in the case of this species of frog, that isn’t always necessarily the case.
A study was done on the European tree frog, Hyla arborea, to figure out why the males in this species choose to either seek out mates “traditionally” or “parasitically.” The traditional way would include actually going out and finding attracting or procuring a mate on their own, while parasitically involves using another competitors skills in order to procure a mate. They wanted to know if this behavior is caused by the size of the frog, or if it is caused by the energy cost that it would take to attract a mate. In order to test these two hypotheses, Brepson and his team set up an experiment in which they randomly caught 100 male frogs from a pond in France and emptied said frogs’ stomachs. The frogs were then split into two groups, one group was fed crickets and flies for seven days consecutively while the other group was starved for the same period of time. Then each frog was put into a container with two speakers, one in the center that played the “chorus” noise (mating calls at the average frequency of the male H. arborea’s croak), and one at the end of the container that played either “attractive” or “unattractive” mating calls for that species. A call was determined to be “attractive” or “unattractive” depending on how low or high the frequency of the call was as well as how often the call was played, with lower and more often was considered more “attractive.” The “satellite” zone was set at any point that was 10 cm or less from the speaker playing the mating calls as a standard for measuring levels of parasitism in this species. Males found in the satellite zone were identified to be acting more “parasitically” than “traditionally”.
In the experiment, they observed that when with faced “attractive” competition, the male H. arborea would exhibit more parasitic behavior. Additionally, it was observed that the smaller frogs were the ones that were more likely to act as satellites than the larger frogs. This result helped to support the hypothesis of size affects the mating behavior of the males. However, there seemed to be no real correlation between the starved males and the fed males as to which sort of mating tactic they would use, which disqualified the hypothesis that the male frogs’ choose how they attracted mates was based on energy cost. Furthermore, the researchers made the observation that all males were more active in their mate seeking tactics earlier in the experiment time, than towards the end, which also aligned with the fact that male H. arborea are more actively mating in the beginning of their season than at the end.
When doing research about this topic, I was able to not only find the original paper of the study (linked below) but I was also able to find a news article on the story to compare it to (article also linked below). Naturally when comparing the article to the original study, the study had much more information with charts and graphs and actual data that you could look into to see how exactly the results turned out. The news article also spent a little more time talking about how being “parasitic” or “traditional” played a role more in terms of a general sense, than about the frogs themselves, most likely because in most animal species, the general behavior of procuring a mate parasitically or traditionally are the same, even if the means are a little bit different. The news article never really analyzed the data, it just gave a you a vague synopsis and left a lot of information about the experimental setup out. However, seeing as the article is meant for general populations to read, the article did an excellent job in articulating the mating habits of the frogs. The original study had a lot of information, which was helpful to a biologist in trying to follow along with the experiment. Because they so thoroughly mapped out their methods and materials, the experiment is replicable and therefore something that can be tested and qualified many times as well as help to find trends in the populations of frogs. However, I felt as though the observations and results for the original article were everywhere, and sometimes the information seemed thrown together, so I feel as though if the data were more organized, the literature would have been easier to get through.
All in all, the study found in this case that sometimes the cheaters DO because smaller frogs acting parasitically by standing nearby to larger frogs with deeper mating calls are still able to secure mates by either mating with females before the larger frogs have a chance to, or by stealing the leftovers when larger frogs attract many females to their area. Cheaters may not always get their first choice in female, but they are given a chance to mate even though their traits are a little less desirable and that is still pretty lucky in their own way.
Articles:
News Article: Bardo, Matt. “Size Matters for Sex Cheat Frogs.” BBC News. BBC, 15 Oct. 2012. Retrieved Feb. 2014. <http://www.bbc.co.uk/nature/19886131>.
Study: Brepson, Loïc, Mathieu Troïanowski, Yann Voituron, and Thierry Lengagne. (2012) Cheating for Sex: Inherent Disadvantage or Energetic Constraint? Animal Behaviour 84(5): 1253-1260. <http://www.sciencedirect.com/science/article/pii/S0003347212004010>.
Tags: communication, competition, frogs, mating