Are you a prairie vole or a meadow vole?

Can you believe that less than 5% of all mammals are long term monogamous?  Whereas 90% of birds stay with their mate for life.  These are a few of the interesting tidbits I came across while doing some reading homework on sexual motivation.

I think voles are much cuter than lab rats, don't you?

But I think the most interesting story starts with a couple of voles.  Voles are small mammals similar to mice.  The genetic variation between a meadow vole and a prairie vole is nearly zero yet they display almost completely opposite behavioral characteristics.  Prairie voles are how we human would like to view ourselves.  They pair-bond with their mates and act more or less monogamous by sharing a nest and defending one another.  When they have a litter, they demonstrate better parenting and care for their young for a longer time than their meadow counterparts.

In fact, I think this song fits my characterization of meadow voles:

They don't make for life, share a nesting ground, or care for their young any longer than is strictly necessary.  Yet these two species are nearly identical in genetic make up.  What's causing the difference in their behavior?

Well a bit of research into their brain structures revealed a rather interesting set of differences.  The prairie voles had more receptors for two very specific signal molecules when compared with their meadow counterparts.  In the female prairie voles, there were more oxytocin receptors in circuits related to the reward pathways in their brains.  I mentioned oxytocin in a valentine's day post so feel free to reference back to that for more details on its effects.  But the basics show that it increases motherly behavior in the females.

The other change was found in the male prairie voles.  They show increased numbers of vasopressin receptors in the ventral pallidus.  This signal has sometimes been linked to aggression in the context of mate-protective behavior.  Thus it makes the males more likely to stick around and protect the family.

The brain images on the left are of the males and on the right are the females.

Turns out, there's a short "microsatellite" piece of DNA code that allows for the additional production of these receptors and the bonding behavior seen in the prairie voles.  And while you may think, what's this got to do with me?  Well, there's currently evidence coming to light that that these same systems are in play in human systems as well.  Surely it's a more complicated system but what does your DNA code your behavior towards?  Do you know?