Keeping Up with the Voles
Male voles are quite the Casanovas, thanks in part to recently discovered memory abilities that once were considered unique to humans
PICTURE A MEADOW VOLE and what may come to mind is, at best, a hungry hawk’s delectable morsel and, at worst, a farmer’s nemesis. But take a closer look and be prepared to blush: The male meadow vole is a four-footed mating machine, a little hot rod of the ’hood and, surprisingly, a window into the workings of human memory. Fortunately for biologist and vole expert Michael Ferkin of the University of Memphis and other wildlife scholars, the rodents’ neighborhoods are the nearby meadows of our rural landscapes, from the East Coast to the Great Plains.
Male voles are wildly successful at reproducing, but their Casanova creds rest on much more than simple numbers. It’s their strategy: The animals have an impressive ability to remember which of the seven or so females residing in their territory will be putting out the welcome mat, Ferkin has found. Just as anxious humans hoping for children jot down the optimal time of month for a tryst, voles, too, appear able to track such vital data.
Ferkin and his colleagues made this discovery through a series of laboratory experiments described in Animal Cognition in 2008. First, the researchers created a little “dormitory” for female voles that were either almost ready to give birth, within hours to days of having given birth, or neither pregnant nor lactating. They allowed male voles to explore the females’ dorm and then removed all the animals and called in housekeeping.
Within 24 hours, they let the males back into the clean, empty complex. Almost without fail, the animals went first to the chambers of females that were about to give birth, and this is the chamber they spent the most time checking out. Why? Because a vole that just—as in hours ago—gave birth is more receptive to mating than any other female. She is not only quite receptive, she’s a time-saver—ready to mate after only about five minutes of courtship. Normally, the male must court a female for 20 to 90 minutes, which involves grooming himself to waft his scent in her direction and lots of sniffing, of course.
“We thought voles were very good at tracking down scents like a hound dog and that is what made them successful at mating,” says Ferkin. “They will do that; they can smell and see who is there. But they also remember that if a female was in a heightened state of sexual receptivity yesterday it probably doesn’t pay to go over there today.”
For a male vole, there are big advantages to knowing which females will be quick to copulate. As Ferkin points out, “everything eats voles.” Scampering from one female to the next increases the likelihood a vole will become lunch meat, so he needs to maximize the benefits of his risky runs. Another advantage of getting to the right female first is that it increases the odds that his offspring—and not another male’s—will be in her next litter. And he needs to get to her before the siren call of her abandoned pups proves more beckoning than his masculine wiles.
Scientists have long debated whether having so-called episodic memory—remembering the what, where and when of a single past event—was unique to humans. Ferkin’s research suggests that voles can perform the cognitive gymnastics required to store episodic memories, he and others assert. What this tells us is that “voles can time travel—they aren’t just living solely in the present,” says Ferkin. And voles are not alone: Studies of scrub jays, laboratory rats and monkeys show they also may have episodic or episodiclike memory.
Jonathon Crystal, a psychologist at the University of Georgia who studies rats, believes Ferkin’s studies show that voles are either planning for the future, remembering the past, or both. During their first visit to the female dorm, the males may be planning what they will do when they return. If instead of planning ahead they act based on their memory of a past event, on that second visit they may be recalling their first visit and, at that moment, deciding what chamber to visit first.
“Looking back in time is episodic memory and the other would be planning for the future … [both] tap into the same type of brain systems,” says Crystal. “Both are really fascinating possibilities.”
Some researchers argue that the animal version of episodic memory differs considerably from that of humans. People reconstruct past experiences in their brain—recalling, for example, the details of a previous event, William Roberts and colleagues at the University of Western Ontario wrote in a 2008 Science article. Animals “appear to remember only how much time has gone by since an important event occurred.” Just like with female voles, it’s harder to impress some scientists than others.
Tina Adler is a science writer in Cabin John, Maryland. She recently wrote for ScientificAmerican.com about whether dogs can talk.
Voles in Love?
Unlike meadow voles—and the majority of the world’s animal species—most prairie voles are monogamous. Native to grasslands of central North America, male and female prairie voles form pair bonds, huddle and groom one another, and share pup-rearing duties. Scientists studying the rodents attribute their unusual mating system to brain receptors that respond differently to the neuropeptides oxytocin and vasopressin—released during social bonding and mating—than do the brains of their closely related cousins.