Male zebra finches growing up without mothers prefer to bond with each other in adulthood, a new study shows, and sexual imprinting may explain why.
We know surprisingly little about why individual animals pair with the opposite sex. After all, the sex of a potential partner is arguably an important part of mate choice, yet little is known about the factors causing those pairings.
To shed some light, Sunayana Banerjee and Elizabeth Adkins-Regana from Cornell looked at the role of exposure to adult females during the development of adult male choice. For their study, they picked zebra finches (Taeniopygia guttata), which are monogamous and biparental, tending to mate for life and raise their offspring together.
The duo raised zebra finch babies in one of two experimental settings: in the presence of adult males and females (control) or in the absence of all adult females, including their mothers. The female-deprived finches were successfully raised by their male parents, and they grew up without any growth deficits. When the finches were fully matured, the team tested the partner preference of the control and female-deprived birds.
They found that 57 percent of the males raised without adult females paired with each other. By contrast, 76 percent of males who were raised with adults of both sexes paired with females. None of the same-sex pairs were females.
"And it wasn't as if the males raised by their dad alone were outcompeted by the males raised by both parents," Banerjee says. "They were actively looking for other males to bond with."
The most likely interpretation of this dramatic effect on pairing outcome is imprinting: when young animals learn the features of another animal and use this to inform their adult choices, Banerjee explains to LiveScience. Previous studies have found that females prefer partners with ornamental blue feathers if their fathers had them, and males preferred female partners with bills that were more vividly colored than their mothers. In this case, the motherless males imprinted on adult males in the aviary in the absence of all adult females.
Their results suggest that social learning is a key developmental process for sexual partner preference, and brain imaging studies could really help suss out the link. But before anyone jumps to any conclusions, Banerjee adds: "Human mate choice is so much more complex."
The work was published in Animal Behaviour this month.
Image: Patrick_K59 via Flickr Creative Commons