Biology Reference
In-Depth Information
ic it is, therefore, to learn that the lowly toad may yet prove to be the savior of some of its more charis-
matic relatives.
The Center for Research of Endangered Wildlife (CREW) and the Herpetology Department of the
Cincinnati Zoo are busily engaged in developing assisted reproductive techniques to help propagate
endangered species of toads and frogs. Oddly enough, their quest started with an old test originally for-
mulated for humans, rather than for frogs and toads.
The Galli-Mainini test was developed fifty years ago to determine human pregnancy. It was dis-
covered that male toads injected with urine from a pregnant woman began to release their sperm, while
the urine of non-pregnant women had no effect. Evidently the human pregnancy hormone replicates the
hormone normally released in the male toad during amplexus.
The CREW team first tested different methods of introducing human urine into the toad in order to
attain maximum effectiveness. Application on the skin of the back had no effect, and application on the
skin of the abdomen only induced sperm release in about one-third of the males. Injection under the
abdominal skin caused some sperm release, but by far the best results were obtained by injecting the
urine into the toad's abdominal cavity.
Using this technique developed with the common toad, CREW and the Cincinnati Zoo have suc-
cessfully bred endangered toads (and ultimately will breed frogs, one would assume) and released their
offspring into the wild. The poor relation, it turns out, is not so poor after all!
During cool, damp weather, toads are active both day and night. When the weather turns hot and dry,
however, they burrow into soft soil, forest litter, or beneath some other shelter. There they wait through
the heat of the day, emerging at dusk to forage during the cool, damp night.
On numerous hot summer evenings, as my wife and I have sat in front of our house to watch the
evening bat circus, we've heard tiny noises as dusk settles—perhaps a slight scratching or scraping, or
the movement of a small pebble. Peering around us, we've been able to see a toad that has just emerged
from beneath the huge, flat stone that constitutes our doorstep. There, in relative coolness, the toad
waited out the heat of the day.
At first the toad's movements are cautious and tentative—a single hop, followed by total immobility
for several minutes. Then comes another hop, followed by another pause. Then, as twilight deepens,
the toad seems to gather confidence; soon it hops slowly but steadily away, quickly disappearing in the
gathering gloom. Toads are abroad again, seeking sustenance, and we're left with the comforting feel-
ing that one more thing is right with the world.
