Winter ticks are killing more moose for this reason

A moose with hair loss Photo by Paul Tessier/Shutterstock

While we all know that winter is inevitable in many areas of the world, it’s not wrong to say that climate change has been delaying the process in some locations.

A study published in September from the Canadian Journal of Zoology,  suggested that winter ticks are having negative effects on the New Hampshire’s moose population, more so now than ever before, killing 70 percent of calves. This mortality rate is from March to April – when the calves are about 10 months old and weigh around 300 pounds.

In the past, lower temperatures and extended shelter from snow could keep the ticks away. But now with climate change resulting in later winter seasons, ticks have more time to find cozy and warm bodies to rest upon, says Peter J. Pekins, professor of natural resources and environment, and one of the authors of the study. 

Though Dr. Brian Stevens, wildlife pathologist at the Canadian Wildlife Health Cooperative, does believe that the weather has a big impact as to why more moose may be affected by these ticks, he also says that it could also have something to do with the number of moose. “When moose density is high, then there are more hosts available for ticks to attach to and subsequently, more moose will be affected,” says Stevens. So, the more moose in the area, the more available homes for the ticks, and therefore a larger number of moose being affected.

Likewise, in that same study, many New England moose calves are dying at a new, and fast pace. These calves can see on average 50,000 ticks per deceased body.

“The highest load of ticks measured on a dead calf was 100,000 ticks, says Pekins.” That’s a highly significant number of bugs on just one calf.

The study also identified 125 calves that died between 2014 and 2016 within New Hampshire and Maine, where tick infestations caused about 90 percent of those deaths. Consequently, these pestering insects were also impacting female adults, resulting in fewer newborn calves overall.

But these ticks are not only affecting the moose that inhabit those regions, Canadian moose in New Brunswick and southern Quebec are also being threatened by winter ticks.

What exactly is a winter tick?

Unlike the black-legged common tick, which is known for carrying Lyme disease, the winter tick (Dermacentor albipictus) does not. However, this tick is larger than most, at about 15 millimetres in length. This species is also known to prefer latching onto one single host as opposed to several hosts, says Stevens. More specifically, these ticks prefer moose, caribou, elk, white-tailed mule and deer, black-tailed mule and deer, and bison — some of our largest animals, and those we think of as majestic.

Winter ticks can parasitize humans, but don’t carry diseases that affect us. Likewise, these ticks don’t seem to carry diseases that parasitize cattle and horses. Also, the meat of an infected caribou, for example, is suitable for human consumption.

How do these ticks harm the moose?

Consequently, these infestations can cause health issues that make the moose more vulnerable to predation. The ticks can also cause the moose to groom excessively due to irritation, which could result in hair loss, and overexposure to the environment, says Helen Schwantje, wildlife veterinarian in British Columbia. The moose can also experience reduced growth, distraction from feeding due to the irritating nature of the tick, and anemia, which is blood loss, says Stevens.

“All of these will lead to a negative energy balance and can result in severe loss of body condition to an emaciated state,” he says. The moose may also have an increased chance of potential road collisions with vehicles as they may begin to feel more confused and disoriented. 

But why moose?

According to the Canadian Wildlife Health Cooperative, moose are often more severely affected because of how their mating season coincides with the time period when tick larvae are most abundant. Since the moose are in constant motion during this time, and are continuously active, it is easier for them to pick up the parasites. It’s also been suggested that unlike some other animals, moose’s grooming habits are less effective and they generally tend to have a “delayed response to infestations,” allowing the larger winter ticks to latch, and accumulate.

At the moment, there is no practical way to prevent these ticks from harming the moose, says Schwantje. But there are some suggested ways to handle an infected animal carcass, such as wearing appropriate clothing that covers the entire body.


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