Growing Up in the Zoo Head-Start Lab

Raising Turtles and Frogs for the Wild

1Lakeshore Zoo runs a conservation program for two threatened animals from nearby wetlands: a small pond turtle and a leopard frog. In the wild, many hatchlings and tadpoles are eaten before they grow big. So the zoo "head-starts" them: keepers raise the young in the zoo until they are large enough that fewer predators can catch them, then release them into protected ponds. Keeper Joy Abernathy and teen volunteer Hana Yoshida ran two tests to learn how to raise the animals faster.

2For the turtle test, the keepers took 20 hatchlings that came from the same nest, so they were all siblings. They placed 10 in a tank of water kept at 27 °C and 10 in an identical tank kept at 22 °C. Both tanks had 12 hours of light each day. Twice a day, each tank was offered as much food as the turtles would eat in 15 minutes. Turtles cannot make their own body heat, so their bodies stay close to the temperature of the water around them. Hana noticed that the turtles in the warm tank swam and ate more, while uneaten pellets were often left in the cool tank. Every two months the keepers weighed each turtle and found the average.

3For the frog test, all the tadpoles hatched from one egg mass. The keepers set up three identical 40 L tanks at 24 °C, each with 12 hours of light a day. Tank A held 10 tadpoles, Tank B held 40 and Tank C held 80. Each day every tank got the same amount of food for each tadpole. On day 40, the keepers weighed the tadpoles and counted how many had grown back legs, an early step in turning into a frog.

4Hana also learned that common snapping turtles live in the same wetlands. Adult snapping turtles grow much larger than adults of the small pond turtle species, even when both live in the same pond.