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A Study of Unfaithful Voles Links Genes to Brains to Behaviour

Prairie voles are meant to be models of monogamy. These adorable rodents form intense lifelong bonds, sticking with the same partner year after year, and raising many generations of pups together. But monogamy doesn’t mean fidelity. Male prairie voles will “cheat” on their partners, wandering into neighbouring territories and mating with females from other couples. And the males differ (#notallvoles?), in that  some individuals are steadfastly faithful while others are more likely to stray.

Now, Steven Phelps from the University of Texas at Austin has shown how these differences in behaviour are connected to differences in the voles’ genes. Specifically, males can inherit variants of a particular gene that affect a part of the brain involved in remembering places. If they have variants that confer poorer spatial memory, they are worse at remembering the locations of social encounters, more likely to wander out of their own territories, more likely to meet other females, and more likely to have pups out of volelock.

Phelps’ study does what few others do: It weaves threads that connect genetics, neuroscience, psychology, and evolutionary biology. It shows how a few DNA differences can change the molecules in an animal’s brain, dramatically changing its social behaviour in ways that affect its success at siring the next generation. It’s a bravura piece of work.

Scientists have been studying the social lives of prairie voles since 1971, when Lowell Getz first discovered their long-term bonds. Together with neurobiologist Sue Carter, he showed that these bonds depends on two related hormones called oxytocin and vasopressin, which are involved in many kinds of social behaviours.

Let’s focus on vasopressin. It works by docking into a protein called the vasopressin receptor, like a key fitting into a lock. The receptor is crucial. The monogamous prairie voles have higher levels of it than promiscuous relatives like meadow voles. If you block it, you block the strong bonds between prairie couples. And if you load extra copies of it into the brains of meadow voles, you can convert them to the monogamous ways of their prairie relatives.

Back in 2003, Phelps and Larry Young caught wild prairie voles and marked the locations of the vasopressin receptor in their brains. “We were shocked by how diverse their brains were. It seemed like every animal was a snowflake,” Phelps recalls. “I showed the images to Tom Insel and he literally laughed. He said, ‘You’ve got a couple of species here. This can’t just be prairie voles.’ But sure enough, the genetics confirmed that they were all prairie voles. They were just really diverse.”

Five years later, Phelps showed one part of the brain was especially important—the retrosplenial cortex (RSC), which is involved in spatial memory. If males have fewer vasopressin receptors in the RSC, they were more likely to wander outside their own territories, away from their female partners, and into the domains of other vole couples.

Now, Phelps’ group, including graduate student Mariam Okhovat, have shown that these variations in brain and behaviour are driven by very subtle genetic differences. They found that the gene for the vasopressin receptor comes in two distinctive versions, which lead to either high or low levels of the receptor in the brain’s RSC. These “high” and “low” versions of the gene differ by just four mutations, which are inherited as a stable quartet.

All of this makes for a remarkably coherent story. You have two versions of the vasopressin receptor gene—a “high” one that produces more receptors in the RSC, and a “low” one that produces fewer. We know that vasopressin is released during social and sexual encounters, and that the RSC is involved in spatial memory. So it stands to reason that the levels of vasopressin receptors in this critical region affects a vole’s ability to remember the locations of social encounters—whether fights with rival males, or liaisons with alternative females.

Males with the “high” version of the gene have lots of vasopressin receptors in their RSCs. They remember social encounters very well, spend more time at home, and are more faithful to their partners.

By contrast, males with the “low” version of the gene have fewer vasopressin receptors in their RSCs. “We think that they have a poorer ability to remember the location of social encounters, so they keep coming around more,” says Phelps. They intrude into the territories of other males more often, encounter more females, and have more sex outside their usual relationships. But they’re also poorer at guarding their own mates. Their wanderlust makes them more likely to cuckold and to be cuckolded.

The critical thing is that both of these strategies “work”. The “high” males who stay are home sire more pups with their chosen partners. The “low” ones who wander around sire more pups with other females. Both are valid strategies, and their relative merits probably depend on how big the prairie vole populations are. If they’re booming, there are plenty of females around, and wandering males may have an easier time. If populations are small, the stay-at-home males might do better. This probably explains why natural selection has kept both the high and low versions of the vasopressin receptor gene around.

To Phelps, the weakest part of this story is the link between vasopressin receptor levels in the RSC and memory. “There’s always a question mark at the psychological level: how changes in the brain produce changes in the field behaviour,” he says. “We don’t really know and we only have good guesses.”

He’s now planning to inactivate that particular part of the brain before putting voles through laboratory tasks and watching their behaviour in natural settings. That will tell him what kind of behavioural differences to look out for. Then, he hopes to edit the voles’ DNA—specifically those four mutations that distinguish the “high” and “low” versions of the vasopressin receptor gene—to see if that changes their behaviour.

19 thoughts on “A Study of Unfaithful Voles Links Genes to Brains to Behaviour

  1. Before the feminists start celebrating, I’d like to point out that the male voles were noted as fooling around with females who had a mate as well. Takes two to do the tango. Any thoughts on what makes a female vole a two-timing b#@%&? 🙂

  2. Do you think you could have made your point without derogatory remarks, Jim?

    Similar research on voles (red-backed) in the Yukon was started a few years back except it was looking at neurotransmitter levels in response to stress. I think they later switched over to snowshoe hares for most of the work. I’m sure they’ve noted this research though as they’re still doing small mammal trapping along with various field experiments.

    Incidentally, that ear tagging job in the picture is badly done…the loop should be snug against the ear, not dangling. That poor vole will get the tag snagged on something within hours and have it torn out of the ear, and there goes a mark-recapture data point along with a raggedy-eared vole. /OCD 🙂

    1. Grow up. Most real women understand how the hypersensitivity of the extremists in the women’s liberation movement have damaged their cause of true equality. I mock those extremists at every chance. Besides, the research itself was derogatory for the same reasons I gave. The female cheaters were given a pass and the male voles all the blame. Grow a spine and use your brain.

      1. Hypersensitive, eh, Jim? You mean like someone who goes out of their way to find a reason to bitch about feminism in an empty comment field, on an unrelated article?

        Also, I’m a feminist, and I’m cheering that the female voles refuse to stand by and let themselves be cuckqueaned 😉 Though it’s pretty shitty that the study didn’t say anything about the female vole brain receptors. As always, the female animal is considered secondarily, or not at all.

        1. Thank you for proving my point. Your cheering says it all. Your offense at my humor at the lack of the female’s role and blaming it all on the man is sad. However, you may note that I questioned the same. Hypersensitivity rules again. At least on the lower rungs. You seem to be a lot more offended at the lack of research into the female, than my noting that men are once again blamed for everything. Like I said in my original post, It takes two to tango.

          1. This is a species in which “cheating” depends primarily on the party outside its usual territory, which are wandering males. The role of females is a separate question requiring different methodology; and would be much harder to do since it would require catching voles actually mating, as opposed to simply noting which ones are trying to mate outside their own turf.

            None of this has anything at all to do with feminism. Only an obsessive would try and bring feminism into research on voles; a species to whom none of the concerns of feminism apply.

          2. For your comment to be “humour”, it would have to be funny – which it ain’t. Instead, it’s mean-spirited and bitter – and completely off topic. The only contribution you’ve made is proof of your own status as a low serotonin, low status specimen with little breeding potential; which pretty much answers your originating question: having made a poor initial choice in partners, there’s always a chance to up one’s own potential through infidelity – hence your bitterness and misogyny.

          3. The reason they focused on the males is because their behavior is easier to track. The females stay in their nests / areas, the males go wandering. You can actually visually track them moving from territory to territory.

            It’s also easier to isolate the particular gene in question in the males.

            I’m sure that at some point someone may do a study on the females, they’re just harder to study.

            No one in this study is blaming “MEN” for cheating or saying “WOMEN” don’t cheat. They said, males voles with a particular sequence don’t wander and others with a mutated sequence do wander and that both patterns are evolutionarily viable or they’d’ve been bred out. There was no judgment on the behavior of any of the animals.

          4. Are you per chance a Ferengi, Jim? Because all that “feeeemales” shit gets on people’s ears pretty easily and you just so happen to overuse it. Slow down on talking for women, kid.

          5. No. I am so sick of the militant feminists who claim exploitation at every remark, while cheering any form of castration of men. They sicken me. They ruined the true women’s equality movement, which was the sexual revolution. These are the same women you can’t be nice to, as they take insult at every opportunity. Screw them. They are always the ugliest of people. Not speaking ugly as features. I am speaking ugly as developed. If you have a problem with that, it is your problem. Not mine. Screw them.

          6. I just can’t fathom what part of the article you interpreted as “blaming” the male vole. It is an objective scientific text reporting on research done on male voles. I assume the same kind of connection between spatial memory and vasopressin receptor levels would be much more difficult to observe in females who do not wander about as much simply because in a significant part of their lives they are more house-bound when pregnant and nursing a litter.
            Hypersensitive… yep. Reading “blame” into a text on animals that have no moral code like human communities… that’s rich 😀

          7. Did you even read the article? Sure, I suppose parallels could be drawn between animal and human behavior, but nowhere in the article was such a comparison made. Talk about hypersensitivity, dude. To clarify, the article was about a study done on the reproductive habits of voles. Apparently, this subject threatens you to the extent that you resort to calling animals derogatory names, and then go on to complain about feminism..? Cool story

          8. Talk about hypersensitive. I notice none of you jumped on the woman who held a polar opposite view. And talk about illogic. To deny it was humor by calling it poor humor is not really a sign of your superiority. Even when questions were answered it was done in poorer taste than mine. Admitting the differences while claiming my argument held no validity and then explaining why they were different is a less than logical approach. All of you who are upset have me laughing at you. So tell me, if you are so upset with me taking a supposed anti-feminist viewpoint, why aren’t you equally upset as the woman who took the opposite view. Her view was no less biased (though she took herself seriously and I didn’t, at least on the feminist issue), yet I’m the only one to be accused of such heresy. If you’re upset and wrote a note about it, I’m laughing at you right now. Why? Because you deserve it.

          9. The study isn’t ‘blaming’ anybody. Infidelity often helps increase genetic diversity and isn’t some cardinal sin in the animal world. They didn’t study females because (I’m assuming) the females had no noticeable behavioral differences. In a species where some males are monogamous, some aren’t, and all the females behave the same, would you spend extra time, money, and effort looking into the genetics of the female’s brain? This study was meant to look into the discrepancy between male behaviors. It’s not ignoring or blaming either sex.

            The main interesting thing about this article is that monogamy is a viable option actually practiced by wild animals. It’s incredibly rare because it doesn’t create the wealth of genetic diversity often needed for survival.

        2. As far as I understand it, the reason that they did not focus on females is that they themselves do not actually wander, so the RSC likely has less importance in their infidelity. If a novel male enters the territory of the male with whom she is paired, she will copulate with him; but she herself will not actively go off into a different territory to seek another male. It’s not that the female animals are considered “secondary,” but rather that this lab is in the mechanism that governs the pattern of wandering, which in this system happens to be manifested in the males,

          Hope this clarifies things!

  3. Well if there’s one thing that can be said in the vole’s favor, be they faithful or not, it’s that they keep their opinions to themselves.

    So if this affects spatial memory, do they also get into more fights with males? Are they slower to remember where they got their butts kicked? And I assume females have the same genetic variation, does their capacity differ? Do they bond more of less well with their mates if they’re not sure all their matings were in the same place?

    1. The females have the same genetic variation, but it doesn’t get translated into their patterns of fidelity. This may be because males have a source of vasopressin in a brain region (called the medial amygdala/bed nucleus of the stria terminalis, for the anatomically curious) that generally does not express vasopressin in females. This source of vasopressin could make it a hormone specific for male social behavior. FWIW, there are other sources of vasopressin shared by both males and females. Aubrey Kelly, who took the photos you see in the press coverage, did some beautiful work on various sources of vasopressin for her dissertation with the late great Jim Goodson, but not with prairie voles.

      Also, it’s true. I’m very fond of country music.

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