Frogs

A frog is a big-sized tailless amphibian, distributed all over the world. There are about 6000 species of frogs out of which about 90 of them dwell in the United States. They stand unique among most other amphibians by their jumping skills, croaking abilities, and unique vocalizations.

Appearance and Physical Description

Size: Frogs vary in size, being as small as 7.7 m (.30 inches), or as large as 320 mm (13 inches) like the Goliath frog of Central Africa. Certain species of the prehistoric age, extinct at present, came with a larger size. In most frogs, the males appear thinner and smaller than their female counterparts.

Weight: Some could be small and lightweight, while a few of them appear bulky. The common frog possesses an average body mass of .05 pounds (0.0227kg), while the Goliath frog weighs as much as 7.2 pounds (3.3 kg).

Head: They have a triangular-shaped head, with a tympanum on each side to help in hearing.

Ears: They lack external ears as humans, but do possess inner ears as well as eardrums. The tympanum or the eardrum looks like a small circle located just below the eyes.

Eyes: These amphibians possess large, bulging eyes, positioned on top of their head, helping them get a clear and distinct vision.

Teeth: Frogs mostly have pedicellate teeth where a fibrous tissue separates the crown from the root. Most of the teeth are located on the roof of the mouth and the upper jaw. The lower jaw has no teeth at all.

Legs and feet: The pattern of their feet vary according to their habitat. They have four and five toes each on their front and back legs, respectively. Those living in water like the African Dwarf frog have entirely webbed feet. Species like the White’s Tree frog thriving on trees have half or quarter of their feet as webbed. The toes of arboreal frogs are also equipped with pads, facilitating a firmer grip.

Skin: They have protective skin with several glands situated on their head as well as back. Folds on the surface alongside warts are mostly seen on frogs dwelling on the ground.

Nervous System: It comprises the brain, nerves, and spinal cord.  The cerebellum controls its muscles and postures. The medulla oblongata takes charge of digestion, respiration, and other functions.

Excretory System: Their excretory system is similar to mammals. Frogs have two kidneys that help to eliminate the nitrogenous wastes from their blood. They also produce increased amounts of diluted urine for flushing out the toxins from their kidney tubules.

Reproductive System: The male frog has two testes attached to its kidneys with the semen passing through fine tubes known as efferent ducts. In the females, the ovaries are located near to their kidneys.

Distribution

Frogs live on all continents apart from Antarctica, and can also survive in varied climates. The wood frog distributed all over North America is also found in the Arctic Circle.

Habitat

Frogs dwell both on land and water. They mostly live in water during their juvenile stage, while their adulthood is partially or fully spend on land. They inhabit freshwater regions like creeks, streams, ponds, and rivers so that they can retain the moisture in their body and survive with ease. Because of the same reason, on land also the frogs live in areas that are moist or damp. Some like Cope’s Gray Tree Frog dwell on trees, while species such as the Wood frog hibernate underground, especially in the winter months.

How Long Do Frogs Live

The lifespan of frogs differs from one species to the other, with most of them surviving between 4 and 14 years on average. The Green and Black Poison Dart Frog may live for 7 to 17 years.  The Argentine Horned Frog survives between 5 and 12 years.

What Do Frogs Eat

Since they maintain a carnivorous diet, frogs mostly eat a whole lot of insects such as mosquitoes, dragonflies, snails, worms, slugs, moths, dragonflies, and flies. Certain large species even consume fish, small mammals, baby turtles, snake, mice as well as other frogs.

Behavioral Characteristics

• Most frogs use the technique of camouflage as a defensive mechanism to get away from their prey. Some can change their color in accordance to their surroundings. However, this ability remain confined to a small range. For instance, the White’s tree frog could alter its coloration to pale green as well as dull brown depending on the temperature.
•  Since they are cold-blooded, they resort to specific behavioral patterns to regulate their body temperature. They move to a warmer area and shaded region to heat and cool their body.
• To prevent water loss and even seek shelter from excess heat, they are often seen in a squatting posture, tucking its hand as well as feet within its body and chin. 
• Most of the males have vocal cords that inflate and deflate, particularly in the mating season, helping them produce various croaking sounds for attracting their mates.

• Many frogs hibernate and go underground during the chilly winters. Some also remain in torpor, with less or no activity at all to cope with the extreme weather conditions.
• During their period of hibernation or inactivity, their metabolism decreases. They mostly thrive on their energy reserves.
• Certain species like the Wood frog, Cope’s Gray Tree frog, Western Chorus Frog, and Eastern Gray Tree Frog survive even when in a frozen state.

Adaptation

• Most of them, especially aquatic frogs, possess immense swimming skills, and their stiff, well-muscled limbs make traveling in water easier for them. Their webbed toes, increase the foot area, helping them propel through water with ease.
• Tree frogs have long toes and legs that make them acrobatic, helping to climb trees flexibly.
• Arboreal frogs also have pads located on their toe tips, which help them in getting a perfect grip on dry or wet surfaces. The secretions from mucus glands give the pad an adhesive property, thus helping them to move about on different surfaces with ease.  
• Their muscles have passive flexibility,  being stretched when they remain in a crouched posture, then contracted, and finally stretched once again, allowing them to leap into the air with ease.
• Many tree frogs possess a waterproof layer on their skin, lessening chances of water loss.
• Their eyelids help to maintain the moisture and cleanliness of their eyes. Of the three eyelid membranes, the one that is semitransparent help in underwater vision.
• The tympanum helps it to hear above and below water. It also serves as a protective layer preventing debris and water from entering the frog’s ears when it is swimming.
• The olfactory nerves give them an innate sense of smell. It helps them detect chemical changes circulating in the air and moving about in ease in their respective habitats.
• Their tongues are long and sticky that can be shot out speedily, thus assisting them to catch insects and swallow them with ease. 
• Ground dwelling frogs lack the smooth skin for camouflaging, hence they are equipped with skin folds and warts, which help them seek protection from their prey.
• They have vocal sacs that aids in the amplification of sound, resulting in varied vocalizations.

Life Cycle of a Frog

The life cycle of a frog comprises four distinct stages, namely the egg, larva or tadpole, froglet, and adult. The eggs laid in still water by the female frog appear in the form of a mass. The male frog fertilizes the eggs by releasing sperm upon them. The eggs hatch between one and three weeks, taking the shape of a tadpole or larva. The tadpoles possess a mouth, long tail, and rudimentary gills. They make little movement during the first or second week after hatching. Eventually, it starts growing, developing many of its physical features. The next stage is the young frog or froglet that almost replicates an adult. The lungs replace the gills, and the tail is also on the verge of disappearance. The tails are absent in the adult frog, with the features gaining more prominence.

Reproduction and Mating

Frogs may either have a prolonged or explosive breeding technique. Most frogs adapt the process of prolonged breeding where they assemble near a water body at a particular time of the year for breeding. The majority of them return to the water bodies, where they had developed as a tadpole. In the case of explosive breeding, adult frogs reach the area of breeding on being stimulated by specific triggers. Reproduction, in this case, takes place promptly, with larval growth being extremely fast-paced. The male mounts on the female, gripping her body tightly. After mating, the female frog releases eggs, and the male covers them with its sperm.

Conservation

The population of frogs has declined severely since the 1950s, with 1/3rd of them being on the verge of extinction and about 120 species already becoming extinct since the 1980s. Costa Rica’s Golden Toad, and Australia’s gastric-brooding frogs are a few of the extinct species. Common factors behind the decline in their numbers include habitat loss because of deforestation, climate change, and pollution. Environmental scientists and biologists are taking initiatives for conservation measures to prevent depletion in their numbers.

FAQs

1.  Are frogs nocturnal?

Most frogs adapting the camouflage techniques are nocturnal. In fact, in the day they try finding a position to mix with their surroundings to escape being detected.

2. Do frogs have a brain?

Yes, they do, it is a part of their nervous system.

3. Do frogs lay eggs?

Yes. The eggs are laid in water that eventually hatches and turn into tadpoles, finally growing into frogs.

4. Do frogs have tails?

No, they are tailless.

5. Are frogs vertebrates? 

Yes, as they have a backbone or spinal cord.

6. Is frog a mammal?

No, it is an amphibian.

7. What is a baby frog called?

A tadpole or pollywog

8. What is the difference between a frog and a toad?

Though both are amphibians, they are different in many ways. The skins of frogs are slimy and moist while that of toads are bumpy and hard. The frogs are bigger, with their eggs laid in a mass. The toads, on the other hand, have their eggs arranged in the form of a chain.

9. Do frogs live in groups?

Yes, as they are social creatures.

10. What is a group of frogs called?

A knot, army, or colony.

11. What are a frog’s feet called?

Their front feet on which they first land during a leap is called hands.

 12. What color is a frog’s blood?

Green, because of the biliverdin pigment, which is responsible for giving it this color.

13. Are all frogs green?

No, they may be of other colors too like red, yellow, orange, purple, and blue.

Interesting Facts

• Frog legs have become a vital diet worldwide, particularly in French, Indonesian, and Chinese cuisine.
• The toxins of frogs have immensely interested biochemists. Epibatidine, a pain killer, much more potent than morphine has been made from certain poison dart frog species. 
• Exudations attained from the Golden poison frog’s skin were used by the native Colombians for poisoning their darts that were used for hunting purposes.
• They form an integral part of fairy tales and folklore, portrayed as lazy, clumsy creatures with hidden talents, though.
• Ancient Peru’s Moche tribe worshipped frog among other animals giving them a prominent place in their art.
• As per a local Panamanian legend, anyone coming across a Panamanian Golden Frog would receive good fortune.