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The Dramatic Life Of A Mule Deer Buck

mule-deer
Mule deer buck (TPWD).

You're driven from your childhood home, to wander alone through hostile, unfamiliar terrain. You get no respect from your elders – and if you think you're going to breed, well, good luck.


Coming of age is no picnic. Just ask a mule deer buck.


Mule deer populations in the Trans-Pecos and Llano Estacado can range from 100,000 to 250,000. Mule deer are critical to the ecology, and the economy, of the region, but there has been little research on the animals.


Scientists at the Borderlands Research Institute in Alpine are working to fill that gap. What they're finding has surprised them.


Mule deer life begins gently enough. Fawns nurse and browse alongside their mothers. The does, as they mature, establish new ranges nearby.


But some time after the age of one and a half, a buck finds he's not welcome. Older bucks harass him, and his mother will kick him out.


The dispersal of bucks safeguards the herd's genetic diversity. It also marks an uncertain period in a buck's life. He must find new sources of food and water. He's vulnerable to predation from coyotes and mountain lions. A young buck can travel 10 miles or more from his original home.


He bides his time. He surveys the social scene of his new terrain, looking for a way in.


Fall is when things get interesting for mule deer. The buck's antlers, which appeared in May or June, grow larger. Testosterone begins to flow, and the bucks' necks swell. As the rut, or breeding season, approaches, the bucks come into conflict, vying for dominance.


Meanwhile, the females have gathered into harems, in the best habitat they can find.– in foothills or rolling country, where forbs, or weedy plants, are abundant. Bucks that have proven their dominance will assert control over a harem. Harems can range in size from five to 50 does. In the weeks of the rut, which typically peaks at Christmas, a dominant buck seeks to breed with every doe in his harem.


Maintaining that monopoly is no small task. Dr. Louis Harveson is the director of the Borderlands Research Institute.


In the past, researchers assumed the dominant bucks did all the breeding. But Harveson says the situation is more complex. The larger the harem, the more difficult it is for a buck to guard. Harveson believes that genetic research would show that less-dominant bucks are having breeding success.


Still, a significant percentage of bucks never develop the weight or antler size to compete. They remain at the periphery throughout their lives.


By the end of the rut, the bucks are in a sickly condition.


The bucks drop their antlers in March or April. As the does sequester themselves to birth, the bucks browse together in “bachelor groups.” The companionship ends when the hormones return.


In research in the Apache Mountains, Harveson and his team have found that the bucks' range is much larger than previously thought. Earlier estimates put it at 3,000 to 5,000 acres. But the BRI has found that mature bucks range over 15,000 acres or more.


One finding has been particularly surprising. Scientists assumed that, after dispersal, bucks adhered to a home range. BRI researchers put radio collars on deer. And in more than one case, they found mature bucks traveled 20 miles or more to adjacent mountain ranges during the rut, apparently on the hunt for different breeding opportunities.


It was a finding that underscored the complexity, and the mystery, of wildlife behavior, Harveson says.