— Night hunters help control the insect population
Story and photos by Anita Westervelt, Texas Master Naturalist
The Lower Rio Grande Valley is the northern most range of the common Mexican tree frog, Smilisca baudinii. Their range includes the Sonoran Desert in Arizona, Cameron and Hidalgo counties in Texas and south to Costa Rica. They inhabit forested or brushy areas near permanent water sources such as resacas and roadside irrigation ditches.
Common Mexican tree frogs are nocturnal. Their diet includes insects, flies, mosquitoes, moths, ants, beetles, crickets, spiders, and other small invertebrates.
Full grown, these frogs measure about two and one-half inches long — measuring vent to snout. Females are larger. The frogs range in color from brownish grey to green and are known to change color while retaining their pattern of irregular dark blotches that spread across their backs and legs. Their skin is smooth.
During the heat of the day, common Mexican tree frogs shelter under loose tree bark, in tree holes and in damp soil. They mostly live in the tops of palm trees and in the leaves of banana plants and other plants with banana-plant type leaves. The frog’s round, silky toe pads work like suction cups to help them cling to slick leaves and other smooth surfaces.
These small frogs are most active following rains when they move to and from wetlands to breed — these rain-induced migrations can occur at any time of year. The frogs are most vulnerable to predators when travelling to and from their breeding grounds. Predators include raccoons, squirrels, hawks, possibly bats, fish and some snakes.
Another local frog is the Rio Grande leopard frog, Rana berlandieri, the only leopard frog found in the Valley. Their range is southern New Mexico to western and central Texas and south to northern Mexico.
Texas has three species of leopard frogs; their territory is distinctly defined with minimal overlap. Plains leopard frog, Rana blairi, is scattered across the panhandle and north central Texas. Southern leopard frog, Rana utricularia, is confined to east Texas, its western most range.
Leopard frogs in Texas are found near permanent or temporary water sources. Their habitat includes shrub lands, grasslands, deserts and grasslands with trees. The Rio Grande leopard frog can tolerate dry conditions.
Leopard frogs in Texas are green, brown or grayish with darker spots that vary in density and shapes from round to square and other shapes in between. They have dorsolateral folds — a raised ridge that appears as a light-colored stripe along the back of the frog at either side from behind the eye to the back end of the frog. In the Rio Grande leopard frog, the dorsolateral fold is disrupted back by the hind legs and jagged inward somewhat toward the center of the back.
Rio Grande leopard frogs are opportunistic eaters, depending on what is seasonally available. In the spring, their diet includes flies, wasps, bees, ants, moths, butterflies and beetles. In the fall, they eat dragonflies and damselflies, bugs, grasshoppers and crickets. They hunt at night and hide in vegetation during the day. They are prey to crayfish, birds, turtles, fish, snakes and small mammals.
Sources: amphibiaweb.org, amphibianrescue.org, animaldiversity.org, frogcalls.blogspot.com