Believe it or not, the frogs actually coordinate their chorus: One male acts as the “chorus master” and starts calling, then the other males in the area start joining the chorus a few at a time, and the music swells.
I lived many years along the riverbed in Valencia, and that was always one of the first sounds to tell me spring had arrived.
Male Pacific tree frogs sing by puffing out their dark gold vocal sacks and can be heard as far as a mile away.
Most frog breeding occurs at night. The males sit near the edge of the water and use different types of calls to communicate both with other males and with females. We are all familiar with the common call of the pacific tree frog: “kreek-eeck.” When Hollywood makes a movie and wants to tell us it is nighttime, they put these sounds in the background.
The most important reason for the call is to attract a mate. Choosing a mate is an important decision, and a large male that makes frequent calls gets first choice. Nothing new there; I guess survival of the fittest – big muscles and a strong voice – still makes sense when you have to reproduce in a tough environment.
Aggressive encounters between males are common, and another sort of call is used. The male makes a trilling sound to serve as a warning if another male gets too close. Sometimes both males will make this encounter call until one backs off. The females are not attracted by the encounter calls, so the males need to settle their competition fast – otherwise the female might go elsewhere to find a mate.
In the midst of all of those calls, the females find a suitable mate. When the female approaches the male, the male will move to her back and grasp her in a position called the amplexus. Then the female will swim to vegetation in the water to lay eggs, where they attach to avoid floating away.
If they survive, the embryos will hatch into tadpoles within one to three weeks. They feed using a beak-like mouth to scoop plant matter off the bottom of their puddles.
Their growth rate is related to the number of other tadpoles they share a home with. The more tadpoles, the more body heat generated and the faster they grow, thanks to the warm water. The metamorphosis happens about two to 2-1/2 months later, but if the conditions are not good, the metamorphosis can be delayed until five months after hatching.
During the last stage of their transformation, when the tadpoles have four limbs and a tail, they are unable to eat for several days while their digestive systems change from their initial vegetarian state to one that can handle their final carnivorous appetite.
When the little frog body is finally ready, it measures less than 1 cm (less than the size of a dime, if you are not metric-thinking).
This change is not caused by the color of the environment, but by the difference in background brightness. This type of change is caused by seasonal fluctuation and is a great adaptation for survival.
Their trademark is an eye stripe that stretches from the nose to the back of the shoulder. They are slender with long and slightly webbed toes, and skin covered in small bumps. On the end of each toe, there is a round sticky pad used to cling to surfaces. And yes, they can climb trees like their name implies – but not too high; just far enough to get to safety if needed.
These are cute little creatures. It’s too bad the winter was so dry this year and the stream is not running through the entirety of Placerita Canyon State Park. But there is water on the Waterfall Trail, so this is where you should be able to hear them.
Good luck.
Evelyne Vandersande has been a docent at Placerita Canyon Nature Center for 27 years. She lives in Newhall.
Spring Chorus Master | Commentary by Evelyne Vandersande
