by Sally Burn
“If music be the food of love, play on” said the lovesick Orsino in Shakespeare’s Twelfth Night. Music is intimately entwined with romance; from a lovelorn John Cusack holding aloft his boombox in Say Anything, to One Direction breaking teenage hearts with their love paens, to tear-stained mixtapes littering a breakup. However, love songs aren’t just for humans. Mice are another species that use the power of song to attract mates. Male mice are quite the warblers, emitting ultrasonic “songs” when they meet a female or encounter female urinary pheromones. A number of previous studies have shown that female mice are attracted by male songs. Now a team of researchers from Japan have discovered that not just any old song will do: females demonstrate song preferences, more specifically they prefer the songs of males unrelated to them. This, the authors propose, helps to prevent inbreeding and is therefore beneficial for maintaining genetic heterogeneity.
It was already known that male songs vary between different strains of mice. The researchers therefore played female mice from two different strains the songs of males from both these strains. The songs were played in separate cage compartments, which also contained the scent of the corresponding male. Females could recognize strain-specific songs and sought out songs from a different strain, indicating that they would seek to mate with a less-related male. Song preference showed links to sexual reproduction as it was modulated by the female’s reproductive status (increased preference for different strain when in diestrus) and by the male pheromones (these further enhanced the preference for a different strain’s song). However, the most influential factor was the song itself.
The researchers hypothesized that song choice is a form of sexual imprinting, given that it promotes outbreeding. Sexual imprinting is an evolutionarily important phenomenon that facilitates kin recognition and thus avoidance of inbreeding. The researchers showed that song preference is indeed imprinted in females during their upbringing. Song preference was reversed if they raised females of one strain with foster parents from a second strain: the females now preferred the songs of males of their own strain. More specifically, imprinting relied on exposure to the father’s song. When female pups were raised without a father they lost preference for any strain-specific song. This study shows for the first time that male songs are a socially-programmed form of kin recognition in mammals. It also adds weight to the argument that ladies should really not date someone who sings like their dad…