Above: A moose in winter (image © istockphoto.com/jentaylor)
Winter can be a harsh time for many animals, especially if they don’t hibernate or migrate for the season. Factors such as available food, temperature, and snow depth can affect an animal’s ability to survive. Moose are an example of a species that is generally well-adapted to winter conditions. Even if they usually can’t find enough food in winter to sustain their body weight, moose eat lots of woody plants in the summer to fatten up. Their long legs help them manoeuver through the deep snow and their large bodies mean they lose less heat (energy) than a smaller animal would.
Did you know? Moose infected by winter ticks have weakened immune systems, making them vulnerable to other infections such as lungworms. What moose aren’t well prepared for is climate change, and the parasitic ticks that thrive in warmer temperatures. In recent years, scientists have been trying come to terms with this new threat to moose populations in North America. There have been an increasing number of sightings of ghost moose. These are not moose demonstrating albinism, which causes all of a moose’s fur to be white. Rather, ghost moose have large patches of missing outer hair. The underlying hair and skin give them a ghostly appearance.
Ghost moose are victims of a parasitic tick, not a genetic disorder. The winter tick (Dermacentor albipictus) is not only causing moose to look different, but it may also be the cause of declining moose populations. The tick latches onto white-tailed deer, elk, and moose in order to survive harsh winter environments in its own way. However, the infestation affects moose much more severely. This is might be because moose only came to North America about 10,000 years ago, whereas white-tailed deer and elk have been here longer. White-tailed deer and elk are also known to lick off tick larvae when they latch on to prevent infestation. Moose tend to ignore the tick larvae and suffer the consequences.
Did you know? A typical infected moose will have around 32,500 winter ticks. The highest number of ticks ever recorded on a moose was 150,000.The winter tick lays its eggs in the spring under the leaf litter, the decomposing leaves that fell the previous fall. The eggs remain unhatched until cooler temperature arrive in the fall. Young ticks can sense the increase in carbon dioxide caused by a moose breathing and releasing heat. At this point, they migrate to tall grasses where they can latch onto passing moose and remain there until spring, when the cycle starts over again. Moose fur is a great environment for ticks to stay warm in the winter, as they feed off the larger animal’s blood.
When it feels irritation from the tick bites, an infected moose will scratch and groom itself to try and remove the ticks. This causes large patches of guard hairs—longer hairs that help protect insulating fur—to fall off. Without guard hairs, moose can end up losing large amounts of heat and even suffer from hypothermia. Blood flow is also essential for energy and, if they don’t get enough, moose become exhausted. To put things in perspective, a single moose that has 40,000 ticks can have its total blood supply drained. That’s 32 litres of blood! Infected moose can also spend more time scratching than feeding, which makes them even weaker and easy prey for wolves.
In recent years, tick infestations have only gotten worse. Many experts believe that climate change is playing a large role in the situation. Because of warmer temperatures, spring arrives sooner and ticks are more likely to live longer. As more moose get infected and the number of ticks on individual moose increases, moose are dying in greater numbers. In particular, moose calves infected with ticks often can’t store enough fat to survive the winter. As a result, their development is delayed and many die from exhaustion.
Did you know? Reports suggest that magpies, gray jays, and ravens feed on winter ticks they find in moose beds (areas where a moose has lain down).With all this talk about ticks, you might be wondering if humans are at risk. Well, the winter tick is considered a one host parasite. This means it only needs to latch on to one animal to survive its whole life, rather than switching between multiple animals as it grows. So even if you encounter a moose, it’s unlikely its ticks would leave it for you. Also, winter ticks aren’t fond of human blood. Although there have been rare cases of humans being bitten, the winter tick is not known to carry disease.
In regions of the far north, like parts of the Yukon, winter ticks aren’t as big a problem for moose as they are in places like Alberta. But as temperatures increase, the tick problem could get worse for even more moose. It’s another example of how human activity can threaten the Earth’s ecosystems and many of the organisms that inhabit them! Ghost moose are just one more problem that could be made worse by climate change, and one more thing to keep in mind when working to reduce carbon emissions.