Animal of the Month
September 2016

Name: Paradoxical Frog (AKA Shrinking Frog)
Scientific Name: Pesudis paradoxa

Class: Amohibia
Order: Anura
Family: Hylidae
Genus: Pseudis
Number of Species: 1
Size: 11 inches long as tadpoles, 2-2¾ inches long as adult frogs
Weight: N/A


Webbed front and back feet, powerful legs for kicking, triangular-shaped head.
Color(s): Tadpoles are tanish-brown and cream colored. Adults range from brownish-green to dark green
Behavior: Highly aquatic, most active when mating.
Preferred Habitat: Ponds, lagoons and lakes.
Range: Northern and central South America.
Diet: Insects, small invertebrates and other frogs.
Lifespan: Up to 11 years in captivity

Status: Least Concern

An idea or concept with a conclusion that makes no sense is called a paradox. Nature has produced one living paradox in the lakes, swamps and lagoons of South America. Usually, animals are smaller when they are young and grow to larger sizes as they get older. This is not true for the paradoxical frog, which begins life as a large tadpole, and then shrinks into a smaller frog!

For the most part, paradoxical frogs are not that unusual for tropical frogs. The adults are about average-size for tropical frogs, inhabiting wetland areas and feeding on smaller aquatic animals. They become the most active during the mating season, when males will attract females by croaking loudly. After mating, females will lay average-sized eggs in a floating foam nest. The eggs will hatch and paradoxical tadpoles will be born. These tadpoles, however, experience a dramatic growth spurt, reaching sizes of ten or eleven inches. As metamorphasis sets in, the tadpoles absorb parts of their body, namely their large tail, and shrink into frogs about two inches long. When scientists first observed these tadpoles and frogs in the wild, they thought that the frogs were the offspring and the tadpoles were the adults! This is an excellent reminder that nature does not always live in a set pattern. Life is dynamic; living and growing in a myriad of different ways.

Paradoxical frogs also have another interesting trait. They contain a chemical compound in their skin called pseudin-2. This compound is thought to provide an antimicrobial defense for the frog. In 2008, it was discovered that a synthetic version of this compound stimulates the production of insulin in pancreatic cells. This means that pseudin-2 may be useful in treating people with type-2 diabetes! This is one reason why natural conservation is so important; not only is nature unique and diverse, but it also can hold the keys to solving many of our medical issues.

The paradoxical frog is a common resident of South America and is currently listed as Least Concern by the IUCN. However, there are concerns that habitat destruction due to agriculture and human settlement could threaten this species. There is also the possible threat of chytridiomycosis, a terrible disease that has decimated frog populations across the planet. The paradoxical frog may be in a good place at the moment, but it is important to be aware of threats and risks so this unique species can continue to be paradoxical.

To learn more about how to protect frogs and other amphibians, check out these awesome organizations:

Save The Frogs!—An international organization dedicated to protecting all amphibians.

EDGE of Existence, Amphibian Page—A remarkable conservation organization dedicated to protecting threatened species that have significant biological history. This page highlights the threats to amphibians, and the website offers ways people can become involved.

Amphibian Ark— A joint effort of the World Association of Zoos and Aquariums (WAZA), the IUCN SCC Conservation Breeding Specialist Group, and the IUCN SCC Amphibiah Specialist Group. This organization is dedicated to protect all amphibians, especially focusing on species that currently cannot be protected in their natural environments.


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