By Doug Moore
A friend recently mentioned hearing sounds like “bleating sheep” along Madera Creek in the evening. Her apt description made me smile. It instantly brought back the first time I had heard this strange sound and wandered about trying to discover the source. The culprit is actually a “frog in sheep’s clothing.” It is the little Canyon Treefrog (Hyla arenicolor), the more common of the two frog species that reside in the Canyon.
Canyon Treefrogs live along seasonal and permanent streams with boulders, rock outcrops, and rocky-bottomed pools. They inhabit drainages from Desert Grassland up into Pine-oak Woodlands. Madera Creek provides perfect habitat. Most often seen clinging to boulders or huddled in rock niches within jumping distance of water, adhesive toe-pads help these treefrogs hold their precarious perches. They often appear to “sun” on rocks during the day, periodically returning to the water to rehydrate. Treefrogs eat insects and small invertebrates. In the Canyon they are preyed upon by Black-necked Gartersnakes, Sonoran Whipsnakes, and mammals like raccoons and skunks.
Well-camouflaged, Canyon Treefrogs are not always easy to see, although they often bask in plain sight. They are able to change color and alter skin texture to match their substrate. Individuals resting on smooth, light granite will have smooth skin and creamy-white coloration. Frogs on rough, darker rocks are darker gray with rough, bumpy skin. The frogs can become mottled black and white on the salt and pepper crystal patterns of Canyon granites. When disturbed, they leap for the water and swim quickly into cover or bottom debris.
Reproduction seems to correspond with peaks in precipitation. Good spring rains stimulate breeding in April; monsoon moisture brings another round in July-August. From egg to tadpole to froglet takes between 50-60 days. Look for tadpoles in Canyon pools in August (some of the tadpoles may also be toads) and metamorphosed froglets on the rocks by early September. About the size of a dime when they transform, the plump adults range from about a quarter to almost silver dollar size.
When walking along Madera Creek on warm evenings, listen for the unique mating call. Also look closely and investigate “bumps” on streamside boulders- some of the bumps may turn out to be Canyon Treefrogs!
Canyon Treefrogs - Doug Moore