We all know that courtship is the best time to highlight our best qualities. But for male Mediteranean field crickets (gryllus bimaculatus), saying “Look! I have stamina!” comes with a price, suggests researcher Sophie Mowles from the University of Nottingham in Loughborough, U.K.
In her latest work on these little guys published in the Journal of Animal Behavior, Mowles found that songs produced by courting crickets require significant amounts of energy and probably serves to advertise the energetic cost capacity of the calling male.
It is not uncommon for males to perform displays during courtship interactions that are assumed to demonstrate some aspect of their quality, but the main function of performing repetitions of courtship displays in particular is debatable.
Scientists have hypothesized that either courtship signals are repeated as a form of validation to make up for errors in transmission or that the act of repetition itself functions to advertise the ability to bear signaling costs.
Mowles investigated signal repetition in field crickets test the latter hypothesis and essentially figure out why these males do the things they do for female attention. By analyzing hemolymph lactate concentrations in male crickets exposed to different courtship encounters, she found that males that had been producing longer and faster courtship songs had higher levels of hemolymph lactate concentration than controls.
What does this accumulation of lactic acid mean? It basically indicates that signaling males exceeded their aerobic capacities and are pushing their limits since this production of lactic acid could potentially damage tissues and cause muscle fatigue.
Why would male crickets go through these lengths? Is repetitive courtship signaling worth the physiological cost?
Does this work for the ladies? It has been shown that female crickets do actually prefer males that produce more vigorous courtship songs. This makes sense if you think about it, vigorous songs must equal vigorous healthy male with lots of energy to avoid predators and produce equally vigorous and fit offspring. Diseased and parasitized males? No thank you.
The present study’s findings demonstrate how a simple repeated courtship display results in the accumulation of energetic costs that come with vigorous signal production- consistent with the idea that these male crickets are most likely showing off some stamina!
Understanding the extent to which these energetic costs push signaling males to their aerobic limits can be valuable for understanding animal communication and, well, priorities.
Watch a singing field cricket here! https://www.youtube.com/watch?v=1w-tWoNKfVY
Mowles, S. L. (2014). The physiological cost of courtship : field cricket song results in anaerobic metabolism. Animal Behaviour, 89, 39–43. doi:10.1016/j.anbehav.2013.12.014