Elusive game: Cow elk become more elusive as they age

Older cow elk traditionally see the least hunting pressure, a factor in their overall survival, but a recent study by researchers from the University of Alberta in Canada is adding a twist to the story.
Courtesy photo |


According to Merriam-Webster’s the term nimrod has two meanings. Many are familiar with the definition most commonly associated with the word, “idiot, jerk”. But the term also means, “hunter”, a reference to the Biblical figure Nimrod who was said to be a great-grandson of Noah and a might hunter.

Fall is in the air in Middle Park and throughout Grand County hunters of various stripes are getting up very early, slipping on camo or blaze orange, and trekking deep into the mountains in search of their elusive prey.

Some will hunt for trophies, others for meat, but all will encounter the difficulty that comes with hunting down creatures who have evolved to survive the harsh rugged landscapes of the western slope. Now new research out of Canada is shedding light on just how elusive big game species can be and how cow elk learn to become masters of survival.

Male elk, called bulls, have a tendency of ending up dead relatively quickly. Elk can live upwards of 20 years in the wild but many bull’s in hunted areas do not reach even half that age before they are harvested. Boisterous bulls are the top prize for trophy hunters and the fall rut causes many to focus more on the fertile cows that roam the woods than the hunters hiding in the thickets.

Cows are a favorite of meat hunters, but most seasoned nimrods will tell you they are looking for a young cow, maybe two or three years old at the most. As such older cows traditionally see the least hunting pressure, a factor in their overall survival, but a recent study by researchers from the University of Alberta in Canada is adding a twist to the story.

“Once female elk reach the age of about 10 years, they are nearly invulnerable to human hunters,” states researcher Henrik Thurfjell. “This age-related difference could be driven only by selection by hunters — or it could also be driven by learning.”

To test their theory that cow elk learn to avoid hunters as they get older Thurfjell and his fellow researchers fitted 49 cows, ranging in age from one to 18 years, with radiocollars and tracked their movements for between two and four years. The researchers were looking for movement and behavior patterns that were common across multiple tagged cows, but also exclusive to older age cohorts.

According to the study older cows had unique movement patterns, indicating learned behavior. In the study older female elk reduced their movement rates, lowering the possibility of detection by hunters, and increased their use of rugged terrain and forests to when near roadways.

The researchers also claimed elk could differentiate between bow and rifle hunters by noting cow elk were more likely to use steep rugged terrain during bow season, when hunters must be closer to their prey, than rifle season.

Kirk Oldham is a wildlife biologist with Colorado Parks and Wildlife in Middle Park. Oldham said he is aware of the study and offered some perspective on the topic in Middle Park. There is a four point restriction on harvesting bulls in Grand County, which prevents hunters from taking yearlings and very young bulls. Oldham said he did not have data on the average age of bulls taken in Grand County but based on his anecdotal observations he would put the average age at time of harvest somewhere between three and six years old.

Oldham did have data on cow harvests though. The data looked at late season private property hunts in Middle Park from 2004 through 2014. During that time period fully 50 percent of the cows taken were five years old or younger while six years of age was the average. Elk can live as long as 20 years in the wild though during the 11 years for which Oldham had data only two cows were taken that were 20 years old.

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