Multimedia Reporting (Kuhr-Musser)

When William Duellman stumbled across a small, odd frog in the jungles of Panama in 1963, it was the start of a long—and strangely evolved career—.

While in the field with graduate students studying tree frogs at night, Duellman came across a frog with, of all things, a pouch on his back. It was sitting on a tree trunk. Now, 42 years later and 22 marsupial frog species later he is still adding to his life list.

“I am not one of, I am the leading expert on marsupial frogs,” Duellman said.

Duellman, retired ecology and systematics professor and curator of Herpetology at the University of Kansas, found the most recent frog species in northern Peru with the help of Pablo Venegas in November 2003. Venegas is a member of the faculty at Facultad de Medicina Veterinaria de la Universidad Nacional Pedro Ruiz Gallo in Peru. Their findings were recently published by the Herpetologists’ League in their quarterly journal, Herpetologica.

The new species is different from other species because of a flat spatula-shaped skull with skin that is fused to the skull and different coloration of the frogs, Duellman said. Most marsupial frogs have big robust skulls, according to Duellman. The new discovery brought the number of species Duellman has discovered to 22. Only 46 species of these amphibians are known at this time

The marsupial frog is a rarity in the frog world, said Juan Manuel Guayasamin, graduate student in the division of evolutionary biology at the University of Kansas.

“Marsupial frogs are one of the extreme products of evolution,” he said. “Through time, female marsupial frogs have evolved a pouch on the back where fertilized eggs are placed.”

10 Species of Tree Frogs are scattered throughout Northern Peru and Ecuador. Based on the Peru Political Physical Map,1973

The marsupial frog generally lives from Costa Rica south to Argentina. Most of the species live in the Andes Mountains. These frogs can range from a couple of centimeters long to almost 4 inches long. They mostly eat insects, Duellman said.

“I have been chasing the damn things for 43 years,” he said. “Sometimes you are successful, but just as many times you are not.”

According to Duellman, there is nothing special about the structure of the brood pouch on female marsupial frogs. It is a pocket in the middle of the back that is used as a form of incubation system to hold fertilized eggs. The females carry these eggs in the pouch until they hatch as live froglets and leave “momma and go off on their own,” said Duellman.

This evolutionary rarity has helped the marsupial frog become partially or completely independent of water, said Guayasamin. By being independent of water the marsupial frog can live up high in trees.

“It is possible that generations and generations can go by without any of these frogs ever touching the ground,” Duellman said. “These are the ones that are hard to find as you can imagine.”

Duellman has been doing research on the marsupial frog since that night in 1963. The species fascinated him and it seemed that scientists knew very little about marsupial frogs at the time, he said. He continues to do research on marsupial frogs because he, along with the museum, is trying to understand the biodiversity of the planet. The greatest diversity of life is in the tropics where his frogs live, he pointed out.

Since 1963 The National Science Foundation has funded all of his research on the marsupial frogs, according to Duellman. He has traveled the equivalent of traveling around the world many times to such places like Panama, Columbia and other central and south American counties looking in places where people haven’t been before, Duellman said.

Scientists think the marsupial frog evolved from another species of tree frog that had indentions similar to a honeycomb on its back where it kept the fertilized eggs, Duellman said. This type of tree frog lived mainly in North and South America. Over time, a brood pouch developed and the marsupial frog was born, according to Duellman.

Currently, Duellman is working on a diary of DNA analyses to better understand the marsupial frogs. He needs tissue samples that have not been preserved, so he must go back into the field and look for more live specimen, Duellman said.

Even though Duellman, 76, retired in December 1996 from teaching systematics and ecology, he still enjoys being able to use the University’s facilities for his work.

“What is better than getting paid for what you like to do,” said Duellman, and then he thought again, “ At least I used to get paid."

Marsupial frogs are a rare species because of the pouch on their back. These frogs are found in varying elevations. Some even live high up in the tree tops.

Scientists believe the pouch on the marsupial frog evolved from this species of tree frog. The honeycomb indentions on this frog were used to carry eggs.

Marsupial frogs can range from a few centimeters all the way to 4 inches long. These specimen have been collected from all over Central and South America.