'Frog'-quently Asked Questions (FAQ's)
1. How many types of frogs and toads are there?
As of 1994, there are 3,500 species of the order Anura (frogs and toads) of which 80 species are found in the United States. In Minnesota there are 14 native species of Anura.
2. What is the classification of frogs?
The classification of frogs is:
For example, the classification for the Strawberry Poison Dart Frog is:
Breeding: In the spring when breeding starts, the male anurans will be the first to come to breeding ponds. Here they use their specialized calls to atract female mates. The male anuran will climb on top of the female's back and clasp the female around her "waist" in what is called amplexus, and the eggs are fertilized in the water as she lays them.
Eggs: The number of eggs that are layed and the length of time that it takes for them to hatch varies upon species. For example, Bullfrog tadpoles take two to three years to metamorphose (grow into adult frogs). The average length is between 6 to 21 days after fertilization.
Tadpoles: consist of gills, a mouth and a tail. Immediately after hatching, they will usually stick themselves to weeds or grasses in the water. After about seven to ten days, the tadpoles will start swimming around and feeding on algae. After about six to nine weeks, the tadpoles start to absorb their tails and grow legs and arms. Now the tadpoles will eat plants and dead insects floating on the water.
Froglet: By approximately twelve weeks, the tadpole has a tiny tail stub and will soon leave the water.
Frog: Between twelve to sixteen weeks, the froglet totally absorbs its stubby tail and leaves the water becoming an adult frog. And the cycle begins again in the spring.
4. Will frogs and toads breed with other species?
Not successfully. Some males are nonselective of mates and will mount other males, which will give a warning noise for the other to release its grasp.
5. How long do frogs and toads live?
Depending on the species, between 2 to 40 years! The average age for a frog or toad is about 4 to 15 years.
6. Do frogs and toads sleep?
Frogs and toads will sit very still with their eyes closed. The assumption is that they are asleep, but it is not clear how long they sleep per day.
7. Is it true that frogs and toads hibernate in the winter?
Yes. During Minnesota winters the frogs and toads become dormant, hibernating either in the aquatic vegetation of lakes and ponds, under the water, or under leaf litter on the ground. For example, the Northern Leopard Frog and the Mink Frog will spend the winter swimming slowly under the ice, in the water of lakes, ponds and streams. The Wood Frog and the Spring Peeper can withstand partial freezing of body fluids buried under leaf little on the woodland floor. There are a lot of interesting facts about hibernating frogs that can be found in Mattison's Frogs and Toads of the World, and in Duellman and Trueb's Biology of Amphibians. Most state amphibian and reptile books have a section on hibernation.
8. How do frogs and toads choose their breeding
There are several theories on how frogs and toads choose their breeding ponds:
1. They return to the closest pond regardless of whether or not they originated from that pond. Although it is hard to keep track of individual frogs and toads, we can observe the numbers and the diversity of the amphibian populations in the ponds every year.
2. There a chemical clues left by other frogs and toads, especially the adults.
3. The light reflection varies from pond to pond. The frogs and toads may be selecting the different reflective qualities.
4. The frogs and toads may remember the way they left the pond.
To learn more about this phenomenon, check out Biology of Amphibians by Duellman and Trueb.
9. How do tree frogs reproduce?
The method of reproduction is different depending on what species of tree frog you are talking about. For example, there is an Asian tree frog that lays its eggs in a foam nest on a tree branch hanging over water. The eggs hatch into tadpoles, and when it rains the outside of the nest softens, and the tadpoles drop directly into the water and then continue their metamorphosis.
The Gray Tree Frog (the largest tree frog found in Minnesota) breeds and lay its eggs in ponds. At the beginning of the breeding season (mid-May), the males sit in the trees between 10 and 30 feet up and call for the females. This will last through June when the breeding season is over. When the females are ready to lay their eggs, the frogs will climb down from the trees and travel to the ponds. The males will climb up on the females' backs and grab them around their waist in what is called amplexus. The males will aid in the egg laying by squeezing the eggs out of the female. As the females lay their eggs in the water, the males fertilize them externally. Female Gray Tree Frogs will lay up to 2,000 eggs. The tadpoles transform in about eight to ten weeks into young frogs. The young frogs will leave the pond to join the adults in late July or early August, feeding in shrubs and trees. They eat many insects, but favor beetles and caterpillars. To learn more about reproduction in anurans, check out The Fascinating World of Frogs and Toads by Marice Julivert.
10. How long have amphibians been around?
Amphibians have been around for an estimated 350 million years. The earliest known frog appeared about 190 million years ago, during what is known as the late Jurassic period.
11. What are some predators of frogs and toads?
Frogs and toads have many predators including, fish, snakes and birds.
AMPHIBIANS IN CAPTIVITY
1. How do I raise tadpoles and what do I feed them?
If you have the tadpoles inside you will need to feed
them until they go through metamorphosis. You can feed them prepared fish
food or cooked greens, such as romaine lettuce. When the tadpoles turn
into frogs, you can feed them live crickets, waxworms or earthworms. It
is also necessary to provide the tadpoles with something they can climb
onto to get out of the water when they go through metamorphosis. There
is good information in Keeping and Breeding
Amphibians by Chris Mattison. One problem
you will run into is that if you are in a state like Minnesota you cannot
release the frogs until next April or May. One thing you can try, it may
not be completely successful is to put the tadpoles in a gallon jar of
water ( no more than 5 per gallon) and place the jar in the back of the
refrigerator so that they will "hibernate". If you are in a
state where the ponds have not frozen for the winter you can try to release
them in the spring/summer.
3. I have a small pond in my backyard that is about 16 inches deep and there is not much room on the bottom for hiding. In preparation for the winter, I have taken my fish out of the pond and brought them indoors. It is starting to get pretty cold at night and I still have frogs and toads hanging around my pond. What should I do with the frogs and toads? Should I take them indoors for the winter? If I need to bring them in, what should I provide them to ensure their survival until the spring when I can let them go?
A pond that is 16 inches deep is shallow enough that it will freeze over in the winter. Many frogs will over-winter in the mud and vegetation on the bottom of lakes and ponds that do not freeze over. Normally the frogs and toads start their winter hibernation in October. Watch what the frogs and toads do as the weather gets colder and the lakes start to freeze. If the weather starts getting colder and the frogs and toads are still hanging around your pond, you may want to either transport them to a nearby lake or pond that does not feeze through, or take the frogs and toads indoors for the winter. (For instructions on setting up an indoor vivarium, see question 2. under Amphibians in Captivity.)
4. How do I handle frogs?
Use extreme caution when holding frogs. It is best to grasp their shoulder blades (or scapulae) with your thumb and forefinger. Be careful not to squeeze their abdominal area. Touch frogs only with wet hands that have been cleaned of all sunscreens or insect repellants, which can kill frogs, tadpoles, or eggs.
THE ANATOMY OF FROGS AND TOADS
For pictures of the anatomy and physiology of frogs check out these fantastic web sites!
Frog Morphology & Physiology Tutorials
Anatomy of the Frog
1. Can frogs hear?
Yes. Frogs hear using big round ears on the sides of their head. What you can see is called the tympanum. It is the outside covering that protects the external ear opening.
2. How do frogs and toads breathe?
Most frogs and toads breathe (and take in moisture) through their skin through a process called cutaneous gas exchange, but they also have lungs with which they breathe.
3. How do frogs and toads call?
They squeeze their lungs with their nostrils and mouth shut. Air flows over their vocal chords and into their vocal sacs located on their throat, which then blow up like balloons. There are some frogs that can make noises without vocal sacs.
4. How do I tell the sex of my frog or toad?
Sexing frogs depends on the species. There are a number of tropical species that are dimorphic in regards to color, with the males being more colorful than females. In Minnesota, Bullfrogs and Green Frog males have larger eardrums than females. In some species males will have enlarged thumbs. Most good field guides will provide descriptions of the differences.
Under certain conditions, some frogs can change
their sex! Check it out:
5. What is the function of a frog's skin?
The function of frog skin is to regulate moisture and fluid transfer. This is why frogs live near lakes, ponds, and streams. This is also why it is not good to hold a frog for too long. Your dry hands will cause the frog's skin to become dry.
6. Do frogs and toads change color?
There are a number of frogs and toads that can change color, depending on the temperature or substrate. In the US the best known example is the Gray Tree Frogs which regularly change from bright green to gray. For more information check Mattison's Frogs and Toads of the World.
7. Do frogs and toads have teeth?
Yes, one of the few characteristics that the three living orders of amphibians (frogs, toads, etc) share is 'jointed' or 'hinged' teeth.
8. How long is a frog's tongue and how fast is it?
The frog's digestive system starts in the mouth with its tongue. For the most part, frog tongues are attached near the back of the jaw and folded on the base of the mouth with the tip of the tongue pointing back toward its throat. Their tongues can be flipped out very rapidly and accurately in order to catch an insect or other tasty treat (mucus glands in the mouth produce a sticky substance that helps to catch prey) (http://tqd.advanced.org/11034/anat.htm).
9. How does frogs' blood and human blood compare?
Check out the following site to find out: http://www.greatscopes.com/act013.htm
10. Can some frogs really clean out their stomach with their legs?
Yes, there are some species of frogs that are able to throw up their entire stomach and wipe it off with their legs. The frogs will do this when they eat something toxic. For more information on this, check out the following site: http://www.frogweb.gov/kratts.html
11. How do frogs and toads deal with water loss?
Different species of frogs and toads have different ways of reducing
water loss. Most frogs and toads live in habitats that provide access
to some sort of water body. The frogs and toads will then spend time in
the water 'replenishing' any water they have lost. However, there are
some frogs and toads that have unique methods of dealing with water loss.
For example, the Water-holding Frog from
South Australia lives in the desert and spends most if its time underground.
Because the desert is very dry, the frog seals itself in a water-proof
cocoon it makes from laters of shed skin.
Another frog that has a unique way of reducing water loss if the the Giant Waxy Treefrog. This species lives high in the rainforest canopy where humidity levels may get relatively low. To reduce water loss, this species produces a waxy substance that it spreads over its skin.
COMPARISONS OF SPECIES
1. What is the difference between frogs and toads?
2. How do I tell the difference between a young Bullfrog and a young Green Frog?
Juvenile Green Frogs and Bullfrogs should be easily separated by the presence or lack of dorsolateral folds (which are folds of skin, not bony ridges). The dorsolateral folds are the raised lines on a frog's back. They are present inGreen frogs, but not in Bullfrogs. In addition, female Bullfrogs and Green frogs will have a small tympanum (eardrum) compared to the males. Bullfrog tadpoles regularly take two years before metamorphosis. In some areas it can be three years. Bullfrogs will not breed without calling, but juvenile frogs will disperse from adjacent ponds or rivers. Bullfrogs and Green Frogs will not interbreed.
3. How do I tell the difference between the Gray Tree Frog and the Cope's Gray Tree Frog?
The physical characteristics of the Gray Tree Frog and the Cope's Gray Tree Frog are very similar, so the best way to distinguish between the two is by their calls. The Gray Tree Frog has a musical, birdlike call and the Cope's Gray Tree Frog has a fast, metallic buzzlike trill.
4. What is the largest frog in the world?
The largest frog is the Goliath Frog of Cameroon in Africa, and is found near swiftly flowing rivers and in dense rain forests. They look like giant bullfrogs. Its body can be more than a foot long, and its entire length with the legs extended can be more than two and a half feet long. Goliath Frogs have been known to weigh more than seven pounds!
5. What is the smallest frog in the world?
"A new frog discovered in Cuba by scientists funded by the National Science Foundation is the smallest in the Northern Hemisphere, and is tied for the world record with the smallest frog in the Southern Hemisphere...The one-centimeter-long frog also is the smallest of the tetrapods, a grouping that includes all animals with backbones except fishes...Scientists S. Blair Hedges of Penn State and his Cuban colleagues discovered the tiny orange-striped black frog living under leaf litter and among the roots of ferns in a humid rainforest on the western slope of Cuba's Monte Iberia. Hedges and Cuban scientist Alberto Estrada gave the frog the scientific name Eleutherodactylus iberia. Those two words are more than three times longer than the frog itself."
6. What is the smallest frog in North America?
The smallest frog in North America is the Little Grass Frog (Pseudacris / Limnaoedus ocularis), which ranges in length from 7/16 to 5/8 inches.
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