Frogs and toads inhabit a wide range of environments, from trees and ponds to swamps and deserts.
Some frogs even live underground!
Even frogs that spend most of their time on the surface may still retreat underground occasionally. Perhaps you’ve seen a toad crawling out of a burrow in the spring or your brand-new pet treefrog burying itself in the substrate of its vivarium.
You may be wondering: why do frogs burrow?
Frogs burrow when entering hibernation or estivation, periods of dormancy triggered by cold or drought. They may also bury themselves in substrate in low humidity or if they feel unsafe. Some frogs burrow to ambush prey, and others use burrows to amplify their calls!
If you’re wondering where frogs go in the wintertime, why your pet frog burrows into the substrate, or how these water-loving amphibians survive the dry season, you’re in the right place!
Let’s dig into the reasons why frogs burrow!
6 Reasons That Frogs And Toads Burrow
Frogs have many adaptations and behaviors that help them survive and thrive in their environments. Burrowing protects frogs from the elements and from predators, and it may also help them catch prey or attract a mate!
Reason 1: Hibernation
Have you ever wondered where frogs go during the winter?
They might be be underground!
As cold-blooded creatures, frogs and toads don’t do well in the extreme cold. They have had to get a bit creative when it comes to surviving winters.
Frogs hibernate, just like bears, bees, and rodents. Their metabolism slows down, and their heartbeat and normal breathing may even stop completely. They can still get oxygen through their skin via cutaneous respiration, but a hibernating frog might appear dead!
Frogs and toads spend their winters in hibernacula – places where creatures enter a sort of dormancy over winter. Depending on the species of frog, the hibernaculum may be a burrow, a crack in a tree, or the bottom of a pond.
Many land-dwelling anurans – like the American toad and eastern spadefoot, for example – dig their own burrows. Frogs may burrow as little as 6 inches (15 cm) or as much as 3 feet (0.9 m) into the earth. Their main goal is to stay below the frost line. Above the frost line, the soil is so cold that the groundwater freezes.
Frogs don’t always dig their own burrows. They might also take shelter in an old burrow dug by a mammal.
Frogs that aren’t so great at burrowing, like spring peepers and wood frogs, find refuge in holes and cracks in logs, trees, or rocks. They may even burrow into the leaf litter. These frogs are more exposed to the elements than those that burrow deep into the soil. Luckily, they have built-in antifreeze! A high concentration of glucose in these anurans’ bodies keeps them from freezing completely.
Regardless of where a frog spends its winter, it can remain dormant for months. When the weather warms, the frog returns to normal.
Frogs in captivity are kept at a stable temperature and do not go into hibernation.
Reason 2: Estivation
Frogs also burrow when entering estivation. Similar to hibernation, estivation is another kind of dormancy that helps frogs survive extreme environmental conditions. While hibernation is triggered by extreme cold, estivation is a response to prolonged drought.
Interestingly, studies have suggested that frogs prefer the parts of their burrow with a lower oxygen concentration during estivation. The lower level of oxygen may help to slow their metabolism more quickly, thereby conserving more energy.
The ornate horned frog and the African bullfrog are just two examples of frogs that burrow when undergoing estivation. Just like in hibernation, frogs in estivation have slowed metabolisms and can stay that way for months – or even years! Spadefoot toads, for example, can stay in estivation underground for up to 10 years!
Enjoy the video below of a spadefoot toad burying itself:
Who knows when it will return to the surface?
During periods of drought or just the annual dry season, some frogs will shed multiple layers of skin to create a sort of waterproof cocoon laden with mucus, leaving only their nostrils exposed. This helps to conserve water and prevents the frog from drying out during estivation.
When the rains return, the frog will exit estivation and resume normal frog activities.
Because pet frogs are constantly kept at high humidity, they do not undergo estivation.
Reason 3: Low Humidity
Dry conditions can cause frogs to burrow – without triggering estivation.
Frogs have permeable skin, and they will lose water if exposed to dry air. As every frog owner and enthusiast knows: humidity is important! Depending on the species, most pet frogs require a humidity level of 60-100%.
If the air is too dry, a frog might bury itself to try and conserve water without going dormant.
Low humidity is one of the biggest reasons that pet frogs burrow. If your frog is spending a lot of time buried in the substrate, check that your humidity level is adequate for the species.
Wild frogs also burrow to escape temporary dry conditions. For example, the sandhill frog of Australia burrows into the moist sand beneath the surface during the day but will emerge at night to hunt. Rain frogs, like the ones in the video below, spend most of their days underground for the same reason!
Enjoy this adorable compilation of rain frogs tucking themselves in:
Burrowing also keeps rain frogs safe from predators, which we will discuss next!
Not all frogs are capable of coping with low humidity for long periods of time, so you should always closely monitor your hygrometer to ensure your frog has a healthy environment!
Reason 4: Hiding From Predators
Frogs also burrow to hide from predators.
While frogs are fearsome predators of insects, worms, fish, other amphibians, and even small mammals, there are a lot of other animals that they have to watch out for. Birds, snakes, fish, mammals, and even other anurans are all natural predators of frogs.
Because they are prey animals, frogs feel safest when they have plenty of hiding places. Frogs burrow when they feel unsafe in their environment.
A study of gopher frogs, which are named after the tortoises whose burrows they inhabit, found that juveniles are more likely to survive to adulthood when there are plenty of tortoise burrows nearby, illustrating the importance of hiding places when it comes to avoiding predators.
New pet frogs often burrow while they are getting used to their habitat. They don’t yet understand that their new home is free of predators and that you aren’t a threat, so they bury themselves in the substrate to feel safe.
Your frog may also burrow in the substrate if they don’t have plenty of other hiding places available. Make sure that your frog’s home is equipped with plenty of plants, wood, or other natural clutter to make them feel safe and secure!
Reason 5: Ambushing Prey
Frogs also burrow to hide from their prey! As ambush predators, many frogs catch prey simply by sitting very still and waiting for the prey to get close enough to grab.
Pacman frogs, bullfrogs, dart frogs, treefrogs, and toads are all examples of anurans that practice this hunting technique.
Some frogs go the extra mile when it comes to ambushing prey. Not only do they stay very still, they may even hide. Pacman frogs in particular will partially bury themselves in the substrate to wait for their prey to get close.
Reason 6: Good Acoustics
Some frogs use burrows to amplify their calls. While most male frogs have vocal sacs to amplify their calls to attract females, not all of them do!
Burrowing frogs (of the genus Heleioporus) lack vocal sacs and have to resort to other means to boost the volume of their advertisement calls.
These frogs live in burrows, even laying their eggs in them. A study found that, by positioning themselves at a certain point within a burrow, male frogs could use resonance to boost the intensity of their calls! While these frogs probably don’t understand the physics behind their choices, it has been suggested that burrows help compensate for the frogs’ lack of vocal sacs.
My Frog Is Burrowing In The Substrate, Should I Worry?
If your frog is burrowing in the substrate, the cause is most likely low humidity. Your frog may also be trying to cope with an incorrect temperature in the vivarium, or not enough hiding places.
If you just got your frog, and it is burrowing into the substrate, don’t worry! Your new friend just needs some more time to adjust to its new home. If your frog is still hiding after 2 weeks, you should reassess its living conditions. If your frog is not even coming out to eat, consult your veterinarian.
A lack of hiding places can cause frogs to burrow, even if they’ve been in their new home for a while! Try adding more clutter to the vivarium to make your frog feel secure.
If you have a frog that is known to bury themselves in the soil to ambush their prey, like a Pacman frog, then them burrowing into the substrate is no cause for concern. If you own a frog that is known for spending its days underground, like the desert rain frog, your frog is just exhibiting natural behaviors. However, it is a good idea to check temperature and humidity anyway, just in case!
As you have seen, frogs burrow for a lot of different reasons!
Burrowing protects frogs from predators, extreme temperatures, and drought, and it enables them to safely lay dormant for months or even a year or more! Frogs burrow to cope with short-term and long-term environmental stressors. They also may bury themselves to hide from their prey!
Burrowing is a natural behavior for many species of frogs and toads. While it can be a sign that your frog is uncomfortable, it likely isn’t anything too serious. Your frog might need time to adjust to its new environment, or it might need higher humidity, a different temperature, or more hiding places.
Always research your individual species and become familiar with what their natural, healthy behavior looks like. While frogs make a lot of noise, they can’t tell us when something is wrong!
By understanding the reasons behind your frog’s various quirky behaviors, you can better understand their needs and provide an even better standard of care.