Though many humans are really into fitness, marmots are really into fatness.
The marmots of North America are found out west. One of their favorite habitats is mountain meadows, which are places that look like the bottom half of this:
Marmots like mountain meadows because they eat plants like grass, flowers, and seeds. They can only do this for about four months out of the year, though, because for the other eight months, mountain meadows look like the bottom half of this:
Snow often covers the tops of mountains in the western United States from September until May. Though some mountain animals deal with the lack of food in winter by migrating to warmer places, you are never going to look up and see a flock of marmots flying south for the winter. Marmots are pretty much stuck on the mountain where they live. Since marmots can’t leave, they have another strategy to survive the winter. They get really, really fat.
Fat is not just something that makes adults watch exercise videos. Fat is a way that animals, including people, store energy.
Like all living things, animals need energy to live. You, for example, are using energy right now, even if you sitting as still as humanly possible. Try it! As you sit as still as humanly possible, your body is using energy to breathe, to pump blood, to see, to hear, to keep your body temperature at 98.6 degrees Fahrenheit, and even to think to yourself, “How long am I going to sit here and do this?”
All animals get their energy from food. When a marmot eats a bunch of flowers, there is energy in the flowers. The marmot’s body will use this energy to power them through the day as they breathe, chew, drink water, scurry around, and pose on rocks for Glamour Shots. If a marmot eats more flower energy than it needs that day, then that extra energy gets turned into fat. The fat stores the energy so it can be used on a later day. Fat is basically like flabby batteries for animals.
Each marmot’s goal is to eat more energy then they use so they can be as fat as marmotly possible by the end of the summer. Being a big, fat marmot in September allows marmots to survive the winter when there's no food. Marmots can live off the energy stored in their fat.
Marmots do not have enough stored energy to be particularly active in the winter, though. You’re not going to see marmots skiing down the mountain or making snowmarmots. You’re probably not even going to see any of them awake. The fat can only keep marmots alive if they hibernate all winter.
Hibernating is kind of like sleeping through the winter, except it's different. When marmots, or any other animal, hibernate, their inner body temperature cools down and their heartbeat, breathing, and everything else happening inside their body slows down. By doing this, they need less energy to survive. If marmots just slept all winter, with normal heartbeats and body temperature, they would not have enough energy to make it to spring.
Marmots hibernate in holes in the ground, often with their entire family joining them. Scientists think marmots hibernate in groups to help them stay warm so they use up less energy (basically, a marmot’s hibernating family members act like big, fat blankets). As marmots hibernate, they keep getting thinner and thinner as they burn off their fat energy. They stop hibernating when it warms up and the plants start growing and there is food available again. By the time marmots wake-up, they are super-skinny. In September they look like a ham, but by April they look like a sausage.
As soon as marmots stop hibernating, they start eating as much as they can. Some of them will double their body weight over the summer in order to have enough energy to survive the next winter.
So, yes, fat is an adaptation that helps animals survive, with the exception, of course, of humans and their overfed pets. Someday, I may write about why, in the 21st Century, we're the only animals whose fat adaptation has become a problem.
To learn more about marmots, read my book A Day on the Mountain.
Online References and Resources:
The Alpine Marmot Foundation. "Hibernation."
Animal Diversity Web. "Marmota flaviventris: yellow-bellied marmot."
BBC Animals. "Cute marmots waking up from hibernation" video.
Encyclopedia of Life. "Marmota flaviventris: yellow-bellied marmot."
UCLA. "What's the life of a marmot like?"
Photos and Images:
Click the photos and images used above to find their sources.