It is a paper about a study I did during my first postdoctoral project, with Gil Rosenthal, who is a co-author on this paper. Work by Gil and those in his lab focuses on the behaviour and biogeography of swordtail fish (check out the lab webpage), which are live bearing poecillids, living in the Sierra Madre Oriental in Mexico. The males of many of these species have extended caudal fins, which look a bit like swords, hence their name. Females of some species show preferences for these swords, sometimes even if the males of their own species don’t show this sword! They also show other visual traits, used in display to females, such as the dorsal fin, and the pattern of bars.
Males not only show off these visual features during courtship to females, they also use olfactory cues. In a very cool experiment (paper can be found here), Gil and co-workers show that males release these olfactory cues in their urine, during a courtship display upstream of the female.
Even though we don’t know as yet what the chemical nature of these signals are, these olfactory cues are species specific, as figured out by a lot of behavioural trials by several people (cited in my & Gil’s paper). Comparing female preferences for olfactory cues and the visual image of each species, females choose more often for males of their own species on the basis of olfactory cues than on the visual image.
In our recent paper, we report a study in which we compared the ontogeny of female preferences for olfactory cues and visual cues and found that both were influenced by experience during early stages of live. Interestingly, the timing of the learning for preferences in the two modalities was different though, with females that had a shorter time available to learn to prefer male features did learn to prefer the olfactory cues, but not the visual cues.
In nature, swordtails live in streams in a mountainous area, where population sizes can be small and highly variable (see picture below of lab sampling and how small the streams can be!). Females may thus have variable opportunities to observe male or female adults of their own species. Why they tune in more to the olfactory cues we can’t explain yet, but given that females are more ‘true to their species’ with olfactory cues than visual cues, this is a very interesting finding.
I think this paper nicely underscores that a closer look at the ontogeny of mate preferences can help explain mate choice preferences, and how they in fact may differ between sensory modalities within a species!