Taking the temperature of big game

Jeff Martin, Ph.D., drives through a bison herd with his FLIR camera recording temperature data. (Texas A&M Agrilife Photo)

• Graduate students monitor thermoregulation habits, climate impact on moose and bison

Big game are usually resilient and adaptive mammals, but increased warming in productive regions of Alaska and the Great Plains poses a threat to populations of moose and bison.

This comes as no surprise to Jeff Martin, Ph.D., and Dan Thompson, Ph.D., both recent graduates from Texas A&M College of Agriculture and Life Sciences, who dedicated their doctoral research to examining the effects of warming temperatures on big game.

One component of Martin’s research measured heat flux in bison, while Thompson aimed to understand body temperature regulation in moose.

Understanding how large game respond to rising temperatures provides key insights into the future sustainability of moose and bison populations on landscapes where increased warming has become a concern.

Perry Barboza, Ph.D., a Texas A&M AgriLife Research professor in the Departments of Ecology and Conservation Biology and Rangeland, Wildlife and Fisheries Management,  served as Martin and Thompson’s primary mentor for the duration of their program.

“Critical areas of bison habitat and moose habitat are getting hotter and that is affecting the productivity of moose and bison,” Barboza said. “These animals are keystones to their ecology, culturally important and vital to the livelihood of many.”

Factors influencing thermoregulation of moose

Dan Thompson works full-time as a wildlife biologist for the Alaska Department of Fish and Game at the Kenai Moose Research Center, a role he also held while in graduate school.

With support from his employer and Texas A&M’s Boone and Crockett Club, Thompson was able to complete research for his doctoral dissertation, which remotely assessed the thermal tolerance of moose on the Kenai Peninsula and how they regulate body temperature.

Thompson said his study worked off of previous research, which indicated moose exhibit signs of heat stress above a certain temperature. However, he noticed that at ambient temperatures above those thresholds, the captive moose he was working with weren’t exhibiting signs of heat stress indicated in earlier studies. His study aimed to reassess those thresholds and better understand how the moose were actually coping.

“I examined their actual body temperature by placing sensors inside them to determine what their normal ranges are and monitored them to see when they were exceeding those ranges,” Thompson said. “Then, I looked at physiological and behavioral indicators to identify ways they were able to control their body temperature.”

In addition to the body heat sensors, Thompson said they used a variety of technology to monitor the moose’s heart rate, respiration rate, respiration temperature and to collect hormone samples, all to evaluate their responses to warm environmental conditions.

Contradictory to the historical research, evidence from Thompson’s findings indicated that heat stress thresholds once identified for moose are less rigid than previously reported, suggesting a higher tolerance or resiliency of moose to heat stress.

Additionally, Thompson found that certain behaviors influence moose body temperature during the summer. Contrary to logic, Thompson found that moose body temperature decreases during low to moderate activity associated with foraging, which may be a result of ingesting large amounts of cool, wet vegetation.

A warming climate can lead to fires, which affect locations for cooling and forage. Digging deeper, he concluded that factors like intensity and duration of weather, and the capacity of moose to use physiological and behavioral responses, all affect their ability to regulate body temperature. Warm, humid weather can result in prolonged heat loads that reduce feeding and mass gain in moose especially in mid-summer, when they need to gain fat for the next winter.

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