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The Curious Case of the Balding Moose
Minnesota’s moose aren’t the only ones with problems. In Norway, these icons of the north are going bald.

Moose have had better days. In Minnesota, these majestic animals are up against blood-draining ticks, brain-eating worms, climate change, disease, and even tangles with wolves (see “What’s Killing Minnesota’s Moose”). And across the Atlantic in Norway, they’re not faring much better.

During the spring of 2007, Norway’s moose started balding. What hunters, tourists, and scientists observed in moose living in the southeastern corner of the country would strike fear into the heart of any young buck: pathological hair loss. But the story gets scarier. Before long veterinarian Madslien Knut identified the likely cause: a particularly nasty fly known as the deer ked (Lipoptena cervi). Yup, the mangy moose were infested with parasites.

Deer keds drink blood. To get it, the insects crawl out of the ground and fly onto nearby hosts, most commonly moose and deer. Once they find a cozy home, they discard their wings and chow down for a while. They then strike up conversations with other deer keds on the host —“You engorge here often?”—and start mating. Unlike most other creepy crawlies, deer keds produce just one larva at a time, which would be sort of adorable if the larva didn’t immediately dig into the moose’s skin for a blood meal. Once the larva pupates, it hops off the animal and holes up in the soil where someday it, too, will turn into a winged adult. It’s all very circle-of-life-ish—you know, if The Lion King were a vampire flick.

Of course, the relationship between parasite and host is nearly as old as life itself. Usually, it behooves the parasite to keep the host healthy enough to provide it with sweet, sweet sustenance. But when external factors like a changing climate disrupt this delicate dance, the consequences can turn deadly.

To put things into perspective, a study conducted in Finland stated that a typical moose might host around 3,500 keds. But Knut was finding Norwegian moose infested with 6,000 to 16,500 bloodsuckers. The researchers aren’t positive why more deer keds would correlate with pathological hair loss, but they have some theories. Perhaps the excessive number of parasites feeding 15 to 20 times a day is simply too much for moose skin to handle, resulting in a widespread inflammatory reaction. Or maybe that many bug bites alters blood flow in some way that negatively impacts hair papillae. In any case, whatever was happening to the moose was more than a cosmetic problem.

Hair loss is no joke in northern latitudes. It decreases a moose’s ability to stay warm and forces the animal to consume more calories to survive the winter. And a bald moose doesn’t do much good for deer keds either. The parasite needs to reproduce in nice, thick shocks of fur.

According to a study led by Knut, the parasite boom may have had something to do with some unseasonably warm weather. The year preceding all the balding had the highest average temperature since such record keeping began in 1940. The researchers believe an extremely warm summer and autumn allowed an exceptional number of deer ked pupae to survive to adulthood. Additionally, a “particularly long period with the absence of night-frost” may have given juvenile keds with wings a longer than usual window to find a host.

The study period covers just one year and makes no mention of long-term climate change’s effect on moose. But the climate is, in fact, warming. And if that means better breeding seasons for deer keds, the balance between host and parasite might be pushed further out of whack—leading, in turn, to some pretty whack-looking moose.

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image of Jason Bittel
OnEarth news blogger Jason Bittel contributes to Slate and serves up science for picky eaters on his website, Bittel Me This. He lives in Pittsburgh with his wife and two tiny wolves. (Note: wolves may be Pomeranians.) MORE STORIES ➔