Zoologists: Lusty voles, mindless of danger, mate li...(euthanized the voles so they could exami...),Health

The work quickly led to some surprises.

The researchers originally theorized that the wanderers would have less vasopressin 1a receptor in regions of their brains necessary for forming long-term relationships. Vasopressin 1a receptor is a protein that responds to the hormone vasopressin. Previous experiments have proven that the hormone is essential for the voles monogamous behavior if they are injected with the hormone, they form monogamous pairs; if it is removed, they go on the prowl.

To the researchers surprise, the long-term relationship or pair-bonding brain regions in straying males had no shortage of receptors, Ophir found.

Other regions of the voles brains, however, proved more telling.

In the paper, Ophir and his colleagues report that the dissections and analysis revealed that the wanderers lacked vasopressin 1a receptors in two regions known to be critical for spatial memory knowledge needed when navigating the environment in search of food or fun. Stay-at-home voles, by contrast, had lots of receptors in these dedicated spatial regions.

That led the researchers to infer that wandering males may not remember the territories where they are attacked by defending faithful males. So rather than avoiding these risky sites, the males keep returning, possibly enduring repeated attacks but sometimes successfully mating with females. What we think is that animals that lack this receptor have a hard time remembering where they encountered aggressive males, Phelps said. That keeps them coming back, which increases their contact with the females.

Phelps added that from an evolutionary perspective, the faithful and wandering male strategies likely arose and persisted because both are successful strategies for procreation.

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