As Female Elk Age, They Learn to Evade Hunters
Older female elk are able to adjust their behavior and adopt more stealth strategies through life, scientists found.
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, and 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 on Wednesday. Tracking dozens of female elk over several years, the authors found that, over all, 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 Dr. Thurfjell, older cows clearly used rugged terrain more often during bow-hunting 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 shoot 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, Dr. 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’s easier to trick a bull, by mimicking the bugle call of a competitor.
In addition to being less targeted, female elk live in groups, where often only a few cows are killed at a time, providing possible opportunities for those that escape to learn what works and what doesn’t in avoiding hunters.
Farmers who want to keep elk away from their crops without decimating local populations could potentially use this dynamic, Dr. Thurfjell said, by killing just a single animal from trespassing herds, so the others learn to avoid that location in the future.
Daniel Sol Rueda, a researcher at the Center for Research on Ecology and Forestry Applications in Spain who was not involved in the study, said that the study did not fully rule out other, non-learning explanations, such as hormonal changes or social dominance leading older elk to use safer areas, .
However, the results were elegantly “suggestive of learning,” he added, and underscored the importance of better understanding how, and to what extent, animals adapt behaviorally to changes in their environment.
“The general perception is that learning is only important for humans,” he said, “but the truth is that it is crucial for many nonhuman animals.”