Wednesday, September 5, 2012

Mmm… The Scent of a Stud

Your smell can say a lot about you… How often you bathe, for example. But in many species, smells can communicate much more… What else might they be saying? And how do you ask them?

What secrets do we hide
when we put on deodorant
and perfume? Image by
Field crickets are one of many species that use pheromones, compounds released by an animal that affect the physiology and/or behavior of others of the same species. Female field crickets can recognize individual males by the pheromones they produce… That is pretty specific information! If females can smell who a male is, what else can she tell about him based on his pheromones?

Male field crickets fight for and defend both females and shelters. Furthermore, females are very picky about what males they mate with and tend to go for males who are better fighters. Raine Kortet and Ann Hedrick at the University of California at Davis asked female field crickets whether they could smell the difference between winners and losers.

Raine and Ann took pairs of male crickets that were the same age and size and placed each one on a separate piece of filter paper in a petri dish for 24 hours. This process infuses each filter paper with that particular crickets’ pheromones. Then they put each of the two pheromone-infused filter papers, plus a third clean filter paper, into an arena. They placed a female in the arena and timed how long she spent on each of the three filter papers. Then they repeated the whole process again with another 58 pairs of males.

Next, Raine and Ann put the size-matched pairs of males together in the same arena and allowed them to compete. Cricket fights generally involve wrestling and biting and then one of the crickets will retreat and avoid his dominant competitor. At this point, they were assigned the ranks of “dominant” (winner) and “subordinate” (loser).

This drawing by Edward Julius Detmold from the 1921 book
Fabre's Book of Insects depicts a dominant cricket defending his
shelter while a subordinate cricket retreats. Image from Wikimedia.
Females spent way more time on the pheromone-infused filter papers than on the clean filter papers. But even more fascinating, the females spent more time on the filter papers infused with the dominant male smell than the papers that smelled like losers. Remember, this was before the males even competed. So now female crickets can predict the future?! …Yeah, kinda. Females can smell which males will win.

But maybe this isn’t as mysterious as it looks at first glance. Pheromones are chemical compounds created by the body – the very same body that wins or loses fights. Bodies that are not in good shape may not be able to produce high-quality pheromones. Another possibility is that the same hormones that influence dominant behavior and fighting ability may also influence pheromones. Or maybe males that are more energetic simply move around more and deposit more scent on the paper. In any case, by picking up the scent of the dominant male, females may be able to choose a mate that is a good fighter, in good physical health, and who may pass these traits on to her offspring.

When you think about it that way, smells can contain a lot of information… So be careful what signals you’re putting out there.

Want to know more? Check this out:

Kortet, R., & Hedrick, A. (2005). The scent of dominance: female field crickets use odour to predict the outcome of male competition Behavioral Ecology and Sociobiology, 59, 77-83 DOI: 10.1007/s00265-005-0011-1

1 comment:

  1. This is simply amazing. The power of scent is so understudied. Thanks for a very thought provoking (as always!) post!