Study Finds High Testosterone May Hurt Newborn Deer


Testosterone in male deer can play a large role in how the animals behave, grow, and when they shed their antlers. While high levels of testosterone in bucks may lead to aggressiveness and dominance over their peers, previous studies found that elevated testosterone also made the deer more susceptible to disease and yielded a shorter lifespan. Now, scientists at the University of Edinburgh found that the same may hold true for newborn deer.

According to a press release by the university, researchers conducted the study on 850 newborn wild red deer on the Isle of Rum between 1996 and 2012. They found that a doe’s firstborn male deer generally has higher testosterone levels than its younger siblings. Researchers are not sure why this seems to be the case, but suggest that perhaps mother deer are weakened by each consecutive male calf, which are heavier and suckle longer than female calves.

The study, which was published in the journal Functional Ecology, also suggested that newborn deer with higher testosterone may be less likely to survive.

“For adult animals such as red deer, high testosterone can increase strength and dominance but reduces immunity and longevity,” said Alyson Pavitt, who lead the study. “This latest finding suggests that individuals born with high testosterone may be subject to similar costs.”

Testosterone plays a vital role in the lives of male deer, including how large and strong their antlers grow. In whitetail deer, a buck’s testosterone level typically skyrockets during the fall rut and will dramatically decline shortly afterwards. When it drops below a certain level, it triggers a reaction between the buck’s antlers and its skull to cause its antlers to detach. Does with an unusually high testosterone level can grow antlers as well.

Researchers said the new study will provide insight into how hormones affect the early development of wild deer, a subject that has received little attention so far.

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