Wood frogs (Lithobates sylvaticus) are fairly small frogs found in the northeastern quarter of the United States and throughout most of Canada to central and southern Alaska. Like most frogs, Wood frogs are obligate carnivores as adults, which means they eat animal protein instead of plants or vegetation.
Wood frogs are generalist predators and will eat almost any prey they can catch, overpower, and fit into their mouths. In the wild, they eat snails, slugs, earthworms, ants, spiders, a wide variety of insects, and other invertebrates. In captivity, they can be fed crickets, dubia roaches, nightcrawlers, mealworms, and other invertebrates.
Wood frogs develop in two main life stages. They start their lives as tiny tadpoles that live entirely in the water. At this stage, they eat algae, plant tissue, and detritus in their aquatic environments.
After about 65 – 130 days, these tadpoles will through a process known as metamorphosis and develop into the adult form wood frogs that most people are more familiar with.
At this point, they become obligate carnivores and will eat a wide variety of prey they can catch
What Wood Frog Tadpoles Eat in the Wild
Wood frogs start their lives as tiny embryos inside eggs. Their first food source for the developing embryos is the yolk of their eggs.
The yolk provides enough nutrition to sustain the developing tadpoles until they are ready to hatch into the water. This can take anywhere from 9 to 30 days.
After hatching, the tadpoles will have poorly developed gills, mouths, and tails – so they can not properly swim or eat yet.
For this reason, they will spend the first few days feeding on the remaining yolk of the eggs. This will provide them with enough energy to grow and develop further.
After about a few days, the tadpoles would have developed enough to start free swimming and feeding on food sources available in the water.
At this early stage, wood frog tadpoles are mostly herbivorous, and will eat:
- Algae
- Soft roots and leaves of aquatic plants (eg. duckweed mosses)
- Phytoplankton
- Detritus (mostly composed of degraded plant materials)
Due to a mostly herbivorous diet, the tadpoles have very long tightly coiled intestines, that make up more than half of their body mass.
Plants contain cellulose, a compound that is very hard to digest. Because of this, plant matter needs to spend more time in the digestive system. This long intestinal tract gives tadpoles more time to break down the plant matter and absorb as many nutrients as possible.
Wood Frog Tadpoles Become Omnivores
A few weeks into their development, the tadpoles start to grow legs, starting with the back legs. Their digestive tract will also gradually shorten.
Wood frog tadpoles at this stage become omnivores and will eat animal protein in addition to plant matter.
They will also eat:
- Aquatic insect larvae (glass worms, mosquito larvae, etc.)
- Water striders
- Zooplankton
- Small insects that fall into the water
- Worms
- Carcasses in the water
Wood frog tadpoles will also eat eggs and larvae of some salamanders and frogs, including those of wood frogs.
Whatever they eat, they will eat constantly. They have high energy demands because they are growing very rapidly. Growing big as fast as possible is necessary for survival, as it enables them to escape their ponds before they dry up.
What Juvenile Wood Frogs Eat in the Wild
After about 65 – 130 days, the tadpoles will go through a process known as metamorphosis, in which they will transform into juvenile frogs.
During metamorphosis, the thyroid gland secretes a growth hormone called thyroxine.
This hormone triggers the tadpoles to:
- Lose the gills, and develop lungs for breathing air
- Absorb the tail into the body
- Grow strong legs for moving on land
- Remodel other organs to form an adult frog
In addition, the digestive tract shortens dramatically, and the inner lining of the remaining intestine thickens, creating many folds in the process. These folds create a very large surface for the absorption of nutrients during digestion.
Once metamorphosis fully is complete, tiny wood frogs will leave the water and live on land.
At this point, Wood frogs become obligate carnivores, which means they stop eating plant matter and will only eat animal-based foods.
Their diet will shift away from aquatic prey and toward mainly terrestrial prey. However, since they are not fully grown yet, they can only eat small live prey.
Wild Juvenile Wood frogs will eat:
- Ants
- Mites
- Small worms
- Small snails, slugs
- Spiders
- Beetles
- Termites
- Springtails
- Fruit flies, and other small insects
As they grow in size, they will be able to eat larger prey.
What Adult Wood Frogs Eat in the Wild
Adult Wood frogs are fully grown, meaning they have bigger mouths and stronger jaws. They basically eat a larger version of the diet they did as juveniles, but their larger size also allows them to eat things they did not eat as juveniles.
Like the juveniles, adult Wood frogs generally prefer to eat live prey and will almost not eat dead bugs or other dead prey items.
Here’s a list of things that make up an adult Wood frog’s diet in the wild:
- Worms, slugs, snails
- Beetles, stinkbugs, wasps, bees, grasshoppers, cockroaches
- Spiders, centipedes, millipedes
- Mosquitos, termites, ants, mites, springtails
- Mosquitoes, fruit flies, crane flies, crickets
- Moths (and their larvae), butterflies (and their larvae), and a wide variety of other insects
Adult Wood frogs are generalist carnivores and will eat just about anything they can fit in their mouths. During spring and summer nights, they often catch and eat insects as they fall to the ground under outdoor lights.
Most frogs use their long tongues to catch prey. In the process, an extensive amount of tongue surface is applied in the feeding strikes, resulting in the prey being engulfed by the fleshy tongue.
However, wood frogs make contact with the prey with just the tip of the tongue, much like toads.
Once the prey is in the mouth, the frog will swallow it whole (although frogs have teeth, they do not use them to chew, but rather to maintain a grip on their prey as they swallow it whole).
A frog can shoot out its tongue, capture prey, and pull it back into its mouth within 07 seconds; which is five times faster than the human eye can blink. This speed makes it effective at catching even fast-flying insects such as flies.
What Adult Wood Frogs Eat In Captivity
Captive Wood frogs can eat all the food they would eat in the wild. The only reason they have a different diet is that most hobbyists cannot easily obtain the wide variety of prey these frogs eat in the wild.
So they are limited to only prey items they can purchase or culture on their own.
However, even in captivity, Wood frogs have to be fed live prey. These live prey items can be purchased in a pet store, online, or even from another hobbyist.
Alternatively, you could culture feeder insects at home if you are up for the challenge.
Here’s a list of things you can feed a Wood frog in captivity:
- Crickets, dubia roaches, orange head roaches
- Wingless fruit flies, nightcrawlers
- Mealworms, waxworms, Super worms,
- Phoenix Worms, black soldier fly larvae
- Silkworms, hornworms
Wood frogs are not picky eaters, and will readily accept most soft-bodied invertebrates. Crickets and Dubia roaches can make up a majority of their diet. However, the key to a healthy frog is a varied and nutritious diet, so remember to switch up the food items offered every few feedings.
Be careful to feed the proper size prey for your frog’s size. A good rule of thumb is that a cricket should never be larger than the distance between the frog’s eyes, or the distance from its eyes to its nose.
Also, IT IS NOT RECOMMENDED to feed red wigglers (Eisenia fetida) to captive amphibians. This is because they exude a noxious fluid that contains a toxin known as Lysenin – which is poisonous to many animals.
When feeding insects with a hard exoskeleton to your pet (such as mealworms or super worms), try to make sure the insects have recently molted, as an insect with a large, hard exoskeleton is difficult to digest and may cause impaction.
As for fruit flies, I recommend Hydei fruit flies as they are considerably bigger than the Melanogaster fruit flies and make a richer meal for your frog.
Can You Feed a Captive Wood Frog Wild Bugs?
You could feed your Wood frog wild-caught bugs. Just be 100% sure they are from a clean area that’s free of pesticides or other chemicals. Avoid feeding bugs that can sting or bite, such as large spiders, hornets, bees, etc.
However, it is generally not a good idea to feed captive toads wild bugs or other wild prey. This is because wild insects may carry diseases and parasites that your toad is vulnerable to.
Also, wild bugs in a seemingly clean area could be carrying pesticides they picked up from another area.
Gut-Loading & Nutrient Supplements
Captive-bred feeder insects are often raised on a cost-conscious diet that is meant to help them grow quickly. This means they are not as nutritious as wild insects that eat a wide variety of vitamin and mineral-rich food.
If your frog is given a low-nutrient diet, it could develop health problems such as metabolic bone disease – which is a fairly common issue in captive amphibians.
For this reason, it is important to increase the nutritional value of the food you give to your frog.
This is mainly done in two ways: dusting, and gut loading.
Gut Loading
Gut loading is the process by which feeder insects are fed nutrient-dense foods at least 48 hours before they are offered to the frog. The intention is to pass those nutrients on to the toad when the insects are eaten.
The process is simple
- Give your feeder insects nutrient-dense foods, such as fresh vegetables with lots of vitamin C.
- After eating this food, the feeder insects will be much more nutritious and pass the nutrients on to the frog when they are eaten.
Dusting
Besides gut loading, another way to ensure your frog gets all the vitamins and minerals it needs is by dusting its food with high-quality powder calcium and vitamin supplements.
Most hobbyists use commercially manufactured supplement powder specifically designed for reptiles and amphibians.
The process is simple:
- First, add a small pinch of supplement powder into a small container such as a cup or an empty cereal container. The powder should only be enough to lightly dust the insects.
- Place one feeding’s worth of feeder insects in the container
- Gently shake the container so the supplements lightly coat the insects
- Once finished, you can offer the dusted insects to your frog
It is a good idea to consult a veterinarian for specific directions on supplementing your pet’s food since many variables go into determining the best supplementation regimen for each animal.
Following your veterinarian’s instructions could help you avoid over-supplementing food.
Otherwise, a good starting point is to dust with a good quality calcium supplement fortified with vitamin D3, 2-3 times a week.
How Much & How Often to Feed Your Wood Frog
Generally, adult Wood frogs will have to be fed every two or three days, while young frogs will need to be fed every day or two.
However, this is not set in stone. If an adult does not eat much during feeding sessions, they may have to be fed every other day.
In addition, the enclosure’s temperature will determine the feeding frequency.
If the temperature is low, your Wood frog will have a slower metabolism and be less active, so it won’t need to each much.
At warmer temperatures, your Wood frog will have a much faster metabolism and will need to be fed much more frequently (every other day).
Regarding how much to feed your Wood frog, the general rule is to only offer as much as the frog can eat in a 20-minute feeding session.
Be careful to not overfeed your frog. Use personal judgment to ensure most of the food offered is being consumed.
Avoid leaving uneaten food (such as crickets) in the enclosure for too long as they can bite or irritate the toad. Remove all uneaten food within 6 hours of feeding.
How Long Can a Wood Frog Go Without Food?
Generally, healthy adult Wood frogs can go for as long as two weeks without food if the environmental temperatures are low, and the frogs have a reduced rate of metabolism.
Juvenile Wood frogs can not survive long without food as they are still growing and have higher energy needs.
However, this isn’t to say you should test the endurance of your frog.
In most situations, it’s a good idea to offer food to your Wood frog at least two to three times per week.
What Human Foods Can Wood Frogs Eat?
Adult Wood frogs are obligate carnivores that are instinctively attracted to movement while hunting for food. For this reason, they will not eat the vast majority of human food.
Humans do not typically eat live food and tend to cook most of their food, so human food will not even register as food to most frogs, including Wood frogs. If you try to offer human food to a Wood frog, it will not eat it.
How to Feed a Wood Frog in Captivity
The most straightforward way to feed a frog is to simply dump the food into its enclosure and let the frog have its fill.
However, some amphibian owners find it easier and safer to feed their pets in a separate enclosure, free of bedding and furniture.
This way you can be sure your frog eats all its insects, the prey cannot hide, and the frog will not pick up any bedding when grabbing prey and mistakenly ingest it along with the prey.
Some frogs, especially those that are still getting used to a new place may be shy and reluctant to eat. In this case, you could entice the frog to eat with the use of some feeding tongs.
Use the tongs to gently hold the food item, then rub it near the nose of the frog. Once he sees it, he will grab it and eat it.
Common Feeding Mistakes
There are a few common mistakes many new toad owners make when feeding their pets.
Using Dead Bugs
In the wild, frogs and toads are ambush hunters that are attracted to prey by movement (motion). For this reason, Wood frogs won’t eat dead bugs. If you offer your Wood frog dead bugs, it will most likely ignore the food and starve. You should only offer live bugs and other prey items.
Using the Wrong-Sized Feeder Insects
Frogs do not chew their food but rather swallow it whole. Feeding a tiny frog a disproportionately large insect could lead it to choke.
Never give a frog anything larger than the distance between its eyes. The bigger the toad, the larger the prey it will be able to eat.
Forgetting to Gut Load Insects
As mentioned earlier, captive-bred feeder insects do not contain as many nutrients as wild insects. They are often raised on a cost-conscious diet that is aimed at making them grow quickly and keeping costs low.
Forgetting to gut load or dust insects before feeding them to your Wood frog means the frog will not get all the nutrients it needs. This nutritional deficiency can lead to serious health problems, and could even be fatal.
Not Using a Varied Diet
Different food items have different nutrients. Not giving a Wood frog a varied diet means it will not get the right variety of nutrients it needs and may end up weak and malnourished.
Switch up the food items offered to the frog every few feedings so it gets a nutrient-rich diet.
Feeding Food With High-Fat Content Too Often
Captive amphibians are not very active animals, so they do not burn off calories. This means giving a captive Wood frog high-fat food (such as wax worms) too often may lead to obesity.
Obesity can then lead to many health problems. For this reason, it is important to limit food with a high fat content to only an occasional treat.
Overfeeding/ Underfeeding
Overfeeding a frog can lead to obesity, which could lead to several health problems. Alternatively, underfeeding means the toad will be undernourished and have poor health.
Common Questions About Wood Frog Diet
Do Wood frogs eat ants? Wood frogs eat ants they can catch. They are very opportunistic predators with very diverse diets – and ants are not off the menu. A single Wood frog can eat hundreds of ants every day.
Do wood frogs eat grasshoppers? In general, Wood frogs eat grasshoppers. However, some grasshopper species such as the eastern lubber grasshopper secrete a toxic foamy, slimy liquid with a nauseating, which makes them foul-tasting, so most Wood frogs will avoid eating them.
If a Wood frog eats a toxic grasshopper, it may gag and regurgitate the insect. For this reason, most frogs quickly learn to avoid eating toxic grasshoppers.
Do Wood frogs eat grass? Wood Frogs do not eat grass. They are obligate carnivores, which means they only eat animal matter. Adult frogs have short alimentary canals, suited for their strictly carnivorous diets – and can not digest grass, or other plants.
Do Wood frogs eat mosquitoes? Wood frog tadpoles eat mosquito larvae in the ponds they live in. Adult Wood frogs eat mosquitoes, found in their environments. For this reason, Wood frogs (and other frog species) help control the population of these pest insects.
Do Wood frogs eat butterflies? In general, wood frogs eat butterflies they can catch and fit into their mouths. In addition, they also eat butterflies in their larval form (caterpillars).
Sources:
Virginia Herpetological Society. Wood Frog Lithobates sylvaticus. Accessed at: https://www.virginiaherpetologicalsociety.com/amphibians/frogsandtoads/wood-frog/index.php
Kiehl, K. 2015. “Lithobates sylvaticus” (On-line), Animal Diversity Web. Accessed at: https://animaldiversity.org/accounts/Lithobates_sylvaticus/
Cardini, F. (1973). Characteristics and Adaptedness of Feeding Behaviors of North American Anurans, Paper presented at June 1973 meetings of the Animal Behavior Society, Amherst, MA
AmphibiaWeb. University of California, Berkeley, CA, USA. Rana sylvatica (LeConte, 1825) Wood Frog. Accessed at: https://amphibiaweb.org/cgi/amphib_query?where-genus=Rana&where-species=sylvatica&account=lannoo
