Arctic Foxes And Polar Bears Are Partners In Crime

One of the most well-adapted animals for cold climates, this little hunter can withstand the harshest environments, the most notorious predators, and the greediest fur trappers. Equipped with looks and smarts, there's nothing that can stop it. This is the miniature killer of the north, the arctic fox. Hi, I'm Danielle Dufault and you're watching Animalogic. Today we're in Churchill, Manitoba, home of the polar bear, looking for its unlikely occasional companion, the arctic fox. This frigid landscape on the west side of Canada's Hudson Bay has an average winter temperature of minus 25 degrees Celsius, with some days getting as cold as minus 45 degrees. It is no home for the weak. Without proper gear, a person could develop hypothermia in as little as five minutes. Welcome to the set of Animalogic. Today we're blessed by the presence of this beautiful arctic fox. These canids are relatively small, at about 60 centimeters in length and weighing just over three kilograms. They're just slightly larger than a chihuahua. And yet, they can survive in the expanse of the Arctic. In the past, we've talked about how animals in colder climates tend to be larger than in the tropics. Having more fat and a smaller surface area relative to volume helps them keep warm. But arctic foxes buck that trend. So how do they survive in one of the coldest and most unforgiving climates on Earth? Well, through a multi-pronged survival strategy. The first and most crucial part is being really, really, really good at withstanding the cold. Even at extreme temperatures, arctic foxes can keep warm due to their multi-layered pelage. About 70% of it is a fine underfur that acts similar to down on birds. Even the pads on their toes are covered in fur, a feature that gives them a rabbit-like appearance. Their scientific name, Vulpes legopus, means hair-footed fox, as this furry pad adaptation is unique among canids. Fur alone doesn't keep you warm and usually, heat gets lost through the skinniest parts of your body. To avoid this, arctic foxes have short snouts, ears, legs, and tails. You can see that her ears are actually very short and round and that's one of the key adaptations that helps her hold on to her heat. Long ears are a little too good at radiating heat outwards, so if they're shorter and rounder, they help her hold on to that heat closer to her body. Her legs are also a lot shorter than other species of foxes, which again, helps retain the heat close to her body. During cold snaps, they basically roll themselves into a ball to minimize heat loss. But the arctic fox's coolest cold-fighting adaptation is something called counter-current blood circulation. This is basically a mechanism that keeps the fox's paws at a lower temperature than its core. Blood entering the paws is used to heat up the blood that's leaving, which prevents the fox's core from being cooled down by losing heat out of its extremities. But just like Thanos, extreme cold in the arctic is inevitable. But arctic foxes can withstand it like nobody else. Their metabolic rate doesn't go up until it's minus 50. And they don't even start shivering until it's minus 70 degrees Celsius, which is as cold as it gets in the arctic. Only the barren plateaus of Antarctica get colder than this. By slowing down their metabolic rate in the cold, their food will digest slower and their bodies will store sugars and fats longer. But it's no guarantee they won't starve. Food is scarce in a harsh arctic winter. All of this sounds like problems that other animals would solve by being bigger. But being large is energetically expensive. And for most of the year, there isn't much to eat around here. During the summer, when their fur turns brown to help them blend in with their environment, the pressure is on to eat as much as possible. On an average day, an arctic fox will patrol the beach during low tide to hunt for fish and invertebrates caught in tide pools. Waterfowl provide ample feeding opportunities. Nesting birds and their eggs are taken with such gusto that a single arctic fox can consume over a thousand eggs in a single season. Voles and lemmings are also heavily consumed when available. But these species go through boom and bust periods and are usually only readily available every three to four years. But when they're abundant, they make up to 70% of the fox's diet. Arctic foxes' ears are adapted to hear the frequency of their prey's chirps and steps under the snow. And then they strike, diving headfirst into the snow to ambush their prey. Foxes are universally known as being smart and resourceful. Arctic foxes are no exception. They figured out that by living in the subarctic, they can refrigerate their food by simply burying it in the snow. Saving food for the lean months can be a literal lifesaver. Some of the caches are huge and in some cases, they can hold over a hundred birds, most commonly petrels and auklets. By the end of fall, they will have increased their weight by up to 50%. But that doesn't mean they can just wait it out until spring. Even when they have food stashes, finding food is a year-round challenge. But everything is much harder in the winter. In the northern part of their range, the sun sets in late November and doesn't rise again until January. During those long, dark days, temperatures dip into the minus 40s. If they can't find anything to eat, they won't see the sun rise again, and they will die in the dark. One of their survival strategies is to follow this ecosystem's apex predator and hope to eat its leftovers. Polar bears are seal specialists, and once they catch one, they make sure to eat all the fat, which is premium bear fuel. Muscles and other soft tissues are sometimes left behind, and that's when arctic foxes come in. It's sort of a free meal, but it means traveling vast distances. They've been seen as far as 800 kilometers away from the nearest landmass, and about 150 kilometers from the North Pole. And beyond that, it means being exposed to lots of predators, such as wolves, wolverines, eagles, owls, and even domestic dogs. Unfortunately, three out of four arctic foxes don't make it past their first winter. And in adults, the mortality rate is still very high, at about 33%. Those who do survive the winter go back to their home ranges for the most beautiful time of the year. Mating season! Foxes are monogamous and live in labyrinthine dens and tunnels, which can be up to 1,000 square meters. Dens are reused every year, and some have been reported to be over 100 years old. The largest ones have dozens of chambers and close to 100 entrances. These furry real estate moguls are usually monogamous, but sometimes live with extended family groups. This is most common in the southern part of their range, where food is more abundant. Because of their high mortality rate, these cuties produce a fox-ton of babies. The record for biggest litter is 22, which is one of the largest of all mammals. Parents feed them until summer, but after that, they're forced to go out and become independent. Females sometimes stay nearby, but males have to go far away, sometimes up to 200 kilometers away from their native range. Males defend their territory aggressively and market with bodily fluids on conspicuous places, such as mounds of polar bear poo, an unorthodox but effective pedestal. Another of their unique features is their color-changing fur, which is chocolate in the summer and vanilla in the late fall. The color changes help them camouflage better, be it on the brown tundra or on the white ice. But unfortunately, all of these adaptations made their fur too desirable. As recently as the late 70s, over 40,000 arctic foxes were being taken every year. This, combined with climate change and diseases such as rabies, have led to dwindling numbers. As the permafrost melts, red foxes, which are twice as big as their northern cousins, are also moving northward and taking over the arctic fox's domain. But thankfully, their range is enormous. And because they reproduce so quickly, there are still enough foxes to consider them a species of least concern. So what should we talk about next? Let me know in the comments and be sure to subscribe for new episodes every week. Thanks for watching! See ya!