This time, it’s temperature that can regulate wolves.
A collaborative study by the U.S. Geological Survey used thermal imaging cameras to test how sarcoptic mange affects heat loss in Yellowstone’s wolves. The results were as surprising as they were colourful.
Caused by the mite Sacroptes scabiei, sarcoptic mange is highly contagious and causes severe itching, skin lesions and hair loss. Another weapon in the anti-wolf arsenal, it was introduced to the Northern Rockies by state vets in the early 1900s to eradicate the local population. Although initially free of the disease, as of 2015 one in ten of the known Yellowstone packs carries mange, which can lead to hypothermia, starvation and malnutrition. Given that wolves suffering mange are already under stress, remote infrared cameras and camera traps were seen as a less intrusive way of studying them.
For their control group, the authors took four healthy adult wolves – two male and two female – from the Grizzy & Wolf Discovery Center in Montana and shaved patches of fur most commonly affected by mange such as the legs, shoulders and hindquarters. With a combination of photography, thermal imaging, motion-triggered cameras and a weather station, the team recorded both captive and wild wolves during the winter of 2012-2013 and compared behaviour, hair and heat loss. The severity of mange was categorised by hair loss, so Type I indicated 1-5% loss, Type II 6-50% loss, and Type III, more than 50% loss.
Unsurprisingly, wolves suffering Type II or III were twice as likely to die as their healthy companions: severe mange could cause a staggering heat loss of 1240-2850 calories at night, up to 80% of a wolf’s average needs. According to the lead author, USGS ecologist Paul Cross, the wolves would need an extra 2-4 pounds of elk meat per day to compensate. This is where the size of the pack can make all the difference.
The mortality rate of mangy wolves dropped if they belonged to a larger pack with only a few infected members, as food would be more accessible. At the same time, this could increase the spread of mange, because mites can be transmitted by skin-to-skin contact or sharing food sources. Recovering from mange once is no guarantee against re-infection, and unfortunately, if there is enough humidity, sarcoptic mites can survive outside their hosts for a short time.
Interestingly, the team found that wind speed, not temperature, had a greater effect on wolves’ heat loss, and younger animals seemed to be most commonly affected.
Ongoing treatment like dips or oral medication are needed to cure mange, but this is not practical for wild animals, particularly ones who live and travel in groups. However, with time and a healthy immune system, wolves can recover and re-grow their fur. Why some Yellowstone wolves are at higher risk, or have more severe or prolonged mange is not yet known and is still being investigated.
Cross, P.C. et al. 2016. “Energetic Costs of Mange in Wolves Estimated from Infrared Thermography.” Ecology 97(8): 1938-1948.
French, B. 2015. “Study: Wolves in Big Packs More Likely to Survive Mange.” Casper Star Tribune. http://trib.com/lifestyles/recreation/study-wolves-in-big-packs-more-likely-to-survive-mange/article_37d11712-a45c-56f8-bec6-db29aba4b8a5.html
Live Science. 2010. “Psychedelic Images to Aid Study of Wolves with Mange.” https://www.livescience.com/10910-psychedelic-images-aid-study-wolves-mange.html
The Northeast Wildlife Disease Cooperative. N.d. “Mange and Mites.” http://www.state.nj.us/dep/fgw/pdf/mange_factsheet.pdf
PetMD.com. N.d. “Sarcoptic Mange in Dogs.” http://www.petmd.com/dog/conditions/skin/c_dg_sarcoptic_mange?page=2
Trolle, M. 2013. “Wolves with Mange can Heal Themselves.” ScienceNordic. http://sciencenordic.com/wolves-mange-can-heal-themselves
USGS. 2016. “Study Shows Cold and Windy Nights Physically Drain Mangy Wolves.” https://www.usgs.gov/news/study-shows-cold-and-windy-nights-physically-drain-mangy-wolves
USGS. N.d. “Effects of Sarcoptic Mange on Gray Wolves in Yellowstone National Park.” https://www.usgs.gov/centers/norock/science/effects-sarcoptic-mange-gray-wolves-yellowstone-national-park?qt-science_center_objects=1#qt-science_center_objects
Yellowstone Wolf: Project Citizen Science. N.d. “Recent Research: The Dyamics and Impacts of Sarcoptic Mange on Yellowstone’s Wolves.” http://www.yellowstonewolf.org/mange_in_yellowstone_wolves.php