Creature Feature: Hiber-Nation

December 04, 2024| Education, Environment

By: Patrick Krudop

Welcome to this month’s Creature Feature, where we explore the wildlife that call Lake Hopatcong and New Jersey home. In previous articles, we’ve covered birds, fish, rodents, and mammals. This time, we’re shifting focus from species to behavior. Let’s dive into a fascinating topic: hibernation—or at least, what most people imagine it to be!

If you grew up learning about hibernation in school and imagined bears finding cozy spots to sleep for a few months, you’re not alone. However, there’s more to the story! In New Jersey, only a few animals are true hibernators, meaning they enter a deep dormant state for an extended period during winter. Most wildlife in the state, however, fall into different categories that don’t fit the traditional definition of hibernation. So, without further ado, grab a snack, find a comfy spot, and settle in for this month’s Creature Feature (but no sleeping!).

Groundhog

First on our list is a true hibernator: the groundhog. Otherwise known as a woodchuck, the groundhog is a very common animal to spot in the spring, summer, and even fall months. But as winter approaches, these rodents dig extensive burrows to create a cozy den where they can sleep for the colder winter months. Groundhogs enter true hibernation, significantly lowering their heart rate and body temperature to as low as 38°F to conserve energy. During this period, they may lose up to half their body weight.

They typically emerge in early February, which might sound familiar if you’ve heard of the famous Punxsutawney Phil. In warmer months, these furry- forecasters feed primarily on grasses, leaves, and vegetables (much to many gardeners’ chagrin) to build up fat reserves for their long winter nap.

Little Brown Bat

The little brown bat is another true hibernator, spending the winter months in caves, mines, or other dark, humid locations. These bats enter a deep state of hibernation, drastically reducing their metabolic rate and heart rate to conserve energy. In hibernation, little brown bats can survive for months without eating, relying on the fat reserves they’ve accumulated during the summer from their diet of mosquitoes, midges, moths, beetles, and other insects. Remarkably (and to our pleasure), bats are some of the best insect eaters in New Jersey. The little brown bat is able to eat half of their body weight in bugs a day and can easily catch 1,000 mosquito-sized insects in an hour!

Beyond their incredible appetite for bugs, these little critters might grow on you even more when you learn that their Latin name, Myotis lucifugus, translates to “mouse-eared light shunner", a fitting nod to their nocturnal habits and distinct ears.

Sadly, little brown bat populations have been severely affected by white-nose syndrome, a fungal disease that disrupts hibernation and depletes their critical energy reserves. To learn more about efforts to combat this disease, visit the U.S. Fish and Wildlife Service website.

Wood Frog

The wood frog is one of New Jersey’s most remarkable winter survivors, capable of surviving partial freezing! Unlike typical hibernators, wood frogs enter a state of brumation, allowing their bodies to freeze and thaw with changing temperatures. Unlike hibernation, brumation enables these cold-blooded amphibians to wake on warmer days to feed, drink, or sunbathe—a flexibility mammals lack, as waking from hibernation can be fatal.

During brumation, wood frogs rely on special proteins to protect their cells from ice damage. Once temperatures rise in spring, they thaw out and resume their normal activities. The easiest way to identify these little critters from other species of frogs we have in New Jersey is to look for the dark brown or black mask that they have running over and around their eyes.

Wood frogs are an incredible example of adaptation, thriving in environments that would be inhospitable to many other species. Their ability to freeze and thaw earns them the title of the northernmost amphibian in North America, with populations even found above the Arctic Circle.

Eastern Box Turtle

Known for its distinctive, domed shell with vibrant patterns, the eastern box turtle is easily recognizable amongst other turtle species in New Jersey. These critters are also unique from other turtles because they have a hinged shell that allows them to completely close themselves off from the outside world (hence the name “box” turtle), which can provide excellent protection against predators like raccoons and opossums.

The box turtle prefers moist habitats such as forests, meadows, and wetlands, where they can find ample food. Their diet is quite varied, including fruits, berries, insects, and macroinvertebrates. Box turtles are also known for their longevity, often living upwards of 40-50 years in the wild and even reaching over 100 years old in professional human care!

As winter approaches, box turtles enter a state of brumation, similar to the wood frog. As they burrow into the ground or under leaf litter, they start to become less active, and their metabolism slows. Unlike the mammalian hibernators, they can wake up during warmer winter days if necessary, making them quite adaptable to changing temperatures.

As a protected species, it’s crucial to respect their habitats to help ensure these remarkable turtles continue to thrive in our ecosystem.

Black Bear

If you live in New Jersey, chances are you’ve heard of—or even seen—this native mammal: the black bear. Though often associated with hibernation, black bears actually enter a state called torpor, which allows them to wake more easily if disturbed.

As temperatures drop, black bears find a den, often in hollow trees or caves, where they settle in for the winter. Depending on age and health, they can weigh anywhere from 100 to 600 pounds. They are primarily solitary animals, often roaming vast territories in search of food. Black bears are omnivorous, with a diet that includes fruits, nuts, insects, small mammals, and even carrion. Their keen sense of smell helps them locate food from very far away with some estimates saying that they can detect a scent up to 20 miles away, making them expert foragers. More conservative estimates place this sense of smell as being somewhere between 2-4 miles- impressive nonetheless! In reality, these estimates could be largely dependent on weather conditions, like wind direction, wind speed, terrain, etc.

As summer transitions to fall, black bears enter a phase where they consume large amounts of food to build up fat reserves for winter. As the weather gets cold, the bear will find that cozy den, and (much to the jealousy of many) sleep away the cold months. Pregnant females will usually give birth near the end of this time (between late December and early February) and nurse their cubs in the safety of the den.

At Lake Hopatcong and throughout New Jersey, you may encounter some of these sleepy residents! Whether you're a naturalist or simply curious about local wildlife, there's always something new to discover about the fascinating creatures that call Lake Hopatcong home.  Every footprint, from tiny to large, helps shape the vibrant life of our lake. Even the smallest presence can have a big impact.

I hope you enjoyed learning about some of the hibernating species we have at Lake Hopatcong. If you have any wildlife photos from Lake Hopatcong, or if there’s a critter you’d like to see featured in an upcoming Creature Feature, please send your submissions to info@lakehopatcongfoundation.org. See you next time!