|Quick! Introduce yourself to this guy before |
his baby-high wears off! Photo by David
Castillo Dominici at FreeDigitalPhotos.net.
Prairie voles are one of the only 3-5% of mammals that are monogamous and in which both parents help take care of young. In females, maternal care is regulated in part by the hormones associated with pregnancy, birth and lactation. The fact that males don’t do those things and they still provide paternal care is curious. The fact that male prairie voles will often provide care to offspring that aren’t even their own is even more curious.
Will Kenkel, Jim Paredes, Jason Yee, Hossein Pournajafi-Nazarloo, Karen Bales, and Sue Carter at the University of Illinois at Chicago recently explored what happens to male prairie voles when they are exposed to unfamiliar vole pups. Male voles without any experience with females or pups were placed in a new clean cage. Then the researchers put either a pup (that was not related to the male), a dowel rod (an unfamiliar object), or nothing into the cage with them for 10 minutes. Afterwards, they measured oxytocin (a hormone associated with bonding between mothers and their offspring) and corticosterone (a stress hormone) in the males’ blood at different time points. In another study, they also looked at the activity of brain neurons associated with the production of these hormones.
A male prairie vole is startled to find a baby in his cage...
But then he takes care of it. Video by Will Kenkel.
Both adult and juvenile males exposed to a pup for 10 minutes had higher oxytocin and lower corticosterone compared to the males not exposed to a pup. But this effect was short-lived, as male hormone levels quickly evened out again. Most of these males that were exposed to a pup showed alloparental care (care of a baby that is not their own), like approaching the pup, cuddling with it and grooming it. Males with higher oxytocin and lower corticosterone levels were more attentive towards the pups. Additionally, alloparental males exposed to pups had more activity of oxytocin-producing neurons and less activity of neurons associated with corticosterone-production in a specific brain region called the paraventricular nucleus (or PVN for short).
Oxytocin is strongly associated with pair bonding in prairie voles, particularly in females, and corticosterone affects pair bonding too (generally increasing pair bonding in males and preventing it in females). If exposure to a pup affects these hormones, maybe it affects how the male would interact with adult females. To test this, the researchers put male voles in a new clean cage and put a pup, a dowel rod, or nothing into the cage with them for 20 minutes. Then they put the males with an unfamiliar adult female for 30 minutes. After getting acquainted with the female, the males were put in a “partner preference apparatus”, which has three connected chambers: a neutral center chamber, a connected chamber with the familiar female tethered into it, and a connected chamber with an unfamiliar female tethered into it. The researchers measured how much time the males spent in each of the three chambers and with each of the two females over the next 3 hours.
|A prairie vole pair snuggles. Photo from Young, |
Gobrogge, Liu and Wang paper in
Frontiers in Neuroendocrinology (2011)
Hmm… Got your eye on a special someone? Try volunteering him to babysit before your next date.
Want to know more? Check this out:
Kenkel, W., Paredes, J., Yee, J., Pournajafi-Nazarloo, H., Bales, K., & Carter, C. (2012). Neuroendocrine and Behavioural Responses to Exposure to an Infant in Male Prairie Voles Journal of Neuroendocrinology, 24 (6), 874-886 DOI: 10.1111/j.1365-2826.2012.02301.x