The Atlanta Journal-Constitution
As female elk age, they learn to evade hunters
Scientists study if nurture or caution adds to longevity.
If you come across an old elk in southwestern Canada, chances are it is female.
Though male elk, or bulls, rarely make it past 5 years old because they are targeted by hunters, female elk, or cows, can live as long as 20 years. Remarkably, cows over age 10 seem nearly invulnerable to hunters.
A team of scientists wanted to know: What makes senior cows so survival-savvy? Is it because these elk are more cautious by nature, which made them better at evading hunters all along? Or is it nurture, meaning cows can learn to dodge hunters over their lifetime, even if they start out more daring?
It seems both factors are at play, the researchers at the University of Alberta reported in PLOS One. Tracking dozens of female elk over several years, the authors found that, overall, careful cows were better at surviving. But they also found that individual cows were able to adjust their behavior and adopt more stealth strategies as they aged. In particular, as females got older, they moved shorter distances and sought safer ground if they faced a higher risk of encountering hunters.
During a postdoctoral stint in Alberta, Henrik Thurfjell, now a research specialist at the Swedish Species Information Center, led an effort to track 49 cows, monitoring each for two to five years with GPS collars that logged the animals’ locations every two hours.
The scientists then tried fitting all their data to various statistical models, which allowed for differing degrees of fixed behavior versus behavior that could change with age. The model that best explained the variation in their data incorporated the two, suggesting that both learning and innate personality traits had a role in influencing how cows act over time.
On top of that, the changes in behavior that the researchers observed suggested that the elk were actually avoiding hunters. Generally, cows moved shorter distances as they aged, which probably decreased their chances of being detected by hunters. They also became better at avoiding roads, or traveling in forest or rugged terrain when close to roads, especially during dawn and dusk, when hunters were out.
Most striking to Thurfjell, older cows clearly used rugged terrain more often during bowhunting season than rifle-hunting season.
“It’s really hard to stalk an elk in rugged terrain as a bow hunter because you need to get really close,” he said. A rifle hunter, however, can fire into rugged terrain from hundreds of yards away.
Astonishingly, the elk seemed to pick up on these “different stories for how hunters behave” and possibly responded accordingly, Thurfjell said. He suspects that, given the chance, male elk would probably learn, too. But where his group surveyed in Alberta and British Columbia, male elk are more heavily hunted, for a few reasons: They are prized more as trophies, some jurisdictions place limits on hunting females, and it is easier to trick a bull by mimicking the bugle call of a competitor. In addition to being less targeted, female elk live in groups, and often only a few cows are killed at a time, providing possible opportunities for those that escape to learn what works and what does not in avoiding hunters.
Farmers who want to keep elk away from their crops could potentially use this dynamic, Thurfjell said, by killing just a single animal so the others learn to avoid that location in the future.