Frogs

Every once in a while I will highlight a group of animals that are extremely interesting but are often overlooked because they are not as ‘popular’ as say, crocodiles, bears, sharks, elephants or tigers. So far I have given a brief insight into the facts and figures of dolphins and bears, but I would like to also focus on some of the more unusual animals we don’t know so much about and look at their behaviour too. For this episode I want to look at our amphibian friends, the Frogs.

There are actually three different groups of amphibians, with frogs and toads belonging to one of them. The main characteristic of an amphibian is that it lays its eggs in water and evolves from breathing under water to breathing air out of water. In the case of frogs and toads the eggs gradually grow from fish like creatures with four legs, a tail and gills for breathing under water, to becoming a land dweller and air breather. This is a basic generalization as there are exceptions, for example there is a toad that gives birth to live young and does not lay eggs. Also, the Surinam toad spends most of its time under water although it does breathe air.

Adult frogs and toads, unlike the rest of amphibians, like salamanders and newts and are tailless. They are cold-blooded animals that rely on their environment to regulate their body temperature. There are approximately 6500 amphibian species of which about 5000 are frogs and toads.

Frogs and toads are very delicate creatures, so much so in fact, that they are widely used as ‘environmental indicators’. Essentially this means that any changes occurring to their habitat has a drastic impact on their population. In turn, this serves as a warning sign to humans and other wildlife that there could be something significant impacting the environment. They serve as a good global indicator since they inhabit every continent apart from the Antarctic and live in almost every kind of environment.

One of the most astonishing features of the frog is that it has permeable skin allowing it to essentially breathe or pass liquids through its skin. The oxygen then dissolves through the moisture on its skin and filters through to the blood stream. As you can imagine this is another reason why frogs are so sensitive to their surroundings and is thought to be linked to why they have been in such sharp decline in recent decades.

Frogs come in all shapes and sizes and a whole variety of extraordinary colours. The smallest frog is only about 10mm long and the largest can grow up to about 30cm. Depending on an individual’s habitat their feet might have adapted to be webbed for swimming or flying or have claws or suckers for climbing, some frogs even have highly sensitive star-like tendrils on their feet (like the star-nosed mole has around its snout) to feel their way around and sense prey. Frogs are traditionally recognized for their amazing ability to jump. Their huge strong legs have modified over time to support bigger muscles and bones. One species is an expert jumper and can leap over 50 times its own body length, about 2 meters.

All toads are frogs, but not all frogs are toads. However, there are a number of characteristics that make a toad a toad and not another type of frog. The following lists a number of the most important ones, although there are always exceptions!

Distressingly for them, male frogs do not have a penis! They have a sex organ called a Cloaca. Frogs fertilize externally, so the female lays her eggs, and the male deposits his sperm over them. To ensure this is successful he will clamp the female from behind, with different species using different tactics. Some grab the female under the arms or around the waist, while others secrete a sort of glue and stay stuck together for the duration of Amplexus (The technical name for amphibian mating). They can remain in this position for days! Crazy, that is some stamina.

One of the coolest things about frogs is their communication and vocal display. Some frogs and toads can bark like a dog, squeal like a pig, or hiss like a snake. All their calls have a meaning, and are often related to mating. Advertising calls are made to attract females, however some sneaky chaps will sit quietly next to a male with a strong advertising call (known as Satellite Behaviour), and then jump on the unsuspecting lady to mate! The Release call is used to tell an over-enthusiastic lover to get off. This is often used when another randy male gets a little confused and starts humping the wrong sex. Most calls are made in order to attract a mate and can be heard up to a mile away, pretty amazing for such small little creatures.

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