The Surinam Toad: A Strange Amphibian and Unusual Egg Care
A Very Strange Amphibian
The Surinam toad lives in South America and is one of the strangest amphibians on Earth. It has a flattened body, a triangular head, and tiny eyes. It also has one of the weirdest methods of reproduction of any amphibian.
Reproduction begins with the male and female toad performing an elegant mating swim. The female releases eggs, which the male fertilizes. He carefully places the fertilized eggs on the female’s back. The eggs then sink and become embedded in the female’s spongy skin. A honeycomb-like structure develops, with one egg in each chamber of the honeycomb. Skin grows over the eggs and they eventually disappear from view.
The eggs hatch inside the chambers. As the young toads grow they move around, creating a rippling appearance on the female’s back. Eventually the tiny toads break out of their chambers and escape into the world.
The Surinam toad is also known as the Suriname toad after one country where it's found as well as the star-fingered toad due to the appearance of its front toes.
Habitat and Distribution
The scientific name of the Surinam toad is Pipa pipa. It belongs to the class Amphibia, the order Anura (which contains frogs and toads), and the family Pipidae. The animal lives in the northern part of South America. It's named after the country of Suriname but is found in neighbouring countries, too. It's also found in the Caribbean on the island of Trinidad.
The toad is most common in the Amazon basin. It inhabits tropical rain forests at low elevations and is found in murky ponds, swamps, and slow-moving streams. It also lives in captivity around the world as a pet and a zoo animal.
The toad has a very strange, squished appearance that make it look as though it has been been involved in a nasty accident. Unlike other frogs and toads, the Surinam toad doesn't sit upright on its hind legs. It's constantly in a flattened posture.
The animal has a wide body with a triangular head and tiny black eyes that have no eyelids. Its nostrils are located at the end of tubular structures on its snout. It reaches a maximum length of about eight inches, not including the legs, but most individuals are four to six inches in length.
The long “fingers” on the toad's front legs have star-shaped structures at their tips, giving the animal the alternate name of star-fingered toad. The rays of the stars end in filaments. These filaments are very sensitive to touch. Unlike its front feet, the toad's hind feet are webbed. The back legs are strong and are used for propulsion, but the front legs are weaker.
Feeding a Captive Surinam Toad
Skin and Colouration
The toad is grey, brown, or olive in colour. Its skin is covered with warty protuberances. Small tentacle-like extensions project from the chin and the corners of the jaw. Some individuals have a dark grey line on their undersurface that extends from the middle of their throat to the end of their abdomen. This line is known as a seam due to its appearance. The top of the seam occasionally meets a horizontal bar across the chest, producing a T shape.
The animal's mottled and drab colour, its flat body, and its habit of lying motionless on the bottom of a pond or stream make it look like plant debris or a dead and decaying body. This is probably a very useful feature for disguising the toad in the wild, since it's often an ambush hunter.
The Life of a Surinam Toad
The Surinam toad is almost completely aquatic, although it does move over land when its watery habitat dries up or during heavy rains. It comes to the water surface every half hour or so to breathe air, but it can stay underwater for an hour or more.
The toad doesn’t have a tongue or teeth. It either probes sediments for food with its long and sensitive fingers or waits to ambush its prey. It sweeps the prey into its mouth with its fingers or lunges at it with its mouth, using suction to ingest the food. The Surinam toad eats worms, insects, crustaceans, and fish.
Like fish, the toad has a lateral line on each side of its body. This organ developed in fish as an adaptation to aquatic life and is sensitive to water motion. The lateral line helps the toad to detect the movement of other animals in the water and is probably a valuable tool for detecting prey.
The video below shows the paired swim during egg laying in the Sabana Surinam toad (Pippa parva). This animal is a relative of the Surinam toad.
Male and Female Sabana Surinam Toads During Egg Laying
Mating and Fertilization
Surinam toads mate under water. The male toad doesn’t croak. Instead, he makes clicking sounds to attract a mate. He produces these sounds by moving the hyoid bone in his throat. Once the male has found a receptive female, he climbs on to her back and wraps his front legs around her body in a process known as amplexus.
While they are joined together, the pair swim through the water. They gracefully somersault as they swim and may stay attached for hours. The female is larger than the male and provides most of the propulsion with her hind legs. While the toads are both upside down during a somersault, the female releases eggs, which fall on to the male’s belly. The pair then move into their upright positions. The eggs drop on to the female’s back and the male fertilizes them.
Unlike many other anurans, Surinam toads have neither vocal cords nor vocal sacs. Any sounds that they make are made by parts of their body other than vocal cords.
Female Toad Carrying Her Eggs
Egg Laying and Deposition
After fertilization, the male gently sweeps the eggs up with his feet. The webs of his front feet expand to form a fan, enabling the male to position the eggs carefully on his mate’s back. The eggs stick to the female's back, although how they do this is a mystery. The eggs don't stick to the male, even when they are in contact with his body, and they don't stick to each other.
The egg laying and depositing processes are repeated multiple times. The female eventually ends up with 60 to 100 eggs on her back. Once all the eggs have been positioned, the male leaves the female, his job done.
Babies Emerging From Their Mother's Skin
The cavities left on the female's back after the youngsters leave may look weird or even unpleasant, but they don't seem to bother the frog. She sheds the damaged skin and the cycle begins again.
Development of the Eggs and Youngsters
Over a period of about twenty-four hours, the eggs sink into the female’s skin. The skin swells up to surround them. A covering forms over the eggs, which hides the presence of the babies. The baby toads take three to four months to develop.
As the babies grow, their activity in the female's skin becomes more and more noticeable. Once the youngsters reach a certain size, the skin "bubbles" as the babies move.
Eventually the young toads emerge from their chambers, leaving holes in their mother's skin. They snap at food as soon as they're released. The female sheds her damaged skin after the babies leave and grows a new skin layer for the next breeding season.
A Close-Up View of the Surinam Toad's Amazing Birth
The Red List categories shown from left to right in the above diagram are as follows:
EX - Extinct
EW - Extinct in the wild
CR - Critically Endangered
EN - Endangered
VU - Vulnerable
NT - Near Threatened
LC - Least Concern
The IUCN (International Union for Conservation of Nature) has established a Red List that classifies animals according to their nearness to extinction. The Surinam toad is currently classified in the "Least Concern" category of the Red List based on a 2014 population assessment. Some other members of its biological family are not so lucky.
The Myers' Surinam toad (Pipa myersi) has a similar reproductive method to its Pipa pipa relative. It lives in Panama and possibly in Columbia. It's threatened by habitat loss due to deforestation and by water pollution. It's classified as endangered on the Red List.
Some people worry that the Surinam toad population could run into trouble in some parts of its range. The animal is facing habitat destruction in its natural habitat due to logging and the clearance of land for agriculture. It may also be sensitive to water pollution. In addition, it's collected for the pet trade. Wild toads have been discovered in Puerto Rico. These animals are believed to have been released or escaped pets.
Overall, however, the Surinam toad population seems to be doing okay at the moment. Hopefully it will continue to do well and researchers will be able to learn more about this very interesting and unusual animal.
Questions & Answers
© 2011 Linda Crampton