Mexican Burrowing Toad

Rhinophrynus dorsalis

Amphibian

Transcript:

Today on Animal Fact Files we’re discussing Mexican burrowing toads. Although their name is Mexican burrowing toads, these amphibians range from southern Texas to Costa Rica. They're also known simply as burrowing toads, likely for this reason, but they aren't the only frogs that burrow, so that name can be confusing as well. These vertebrates are also known as cone nose frogs which is in reference to their pointed snout. These animals are round, have no neck, and possess loose skin. Their eyes are tiny, which alludes to their fossorial nature, and they have blotchy yellow to red spots across their black to dark brown body color.

Mexican burrowing toads have the common name “toad” but they aren't classified in the true toad family. They're the only living species of their entire taxonomic family and are currently believed to be most closely related to aquatic clawed frogs, although they themselves are largely terrestrial. In fact, these frogs spend most of their time underground, and they're rarely observed by humans. Mexican burrowing toads live in dry forests and grasslands with permeable-soil they're able to dig through. They have shovel-like structures on their inner ankles that help them dig into and through the soil. Here, they spend their days finding subterranean food and waiting for the rain.

Just about the only time Mexican burrowing toads excavate themselves from the ground and hop about on the surface is directly after a heavy rain. The rain fills in temporary ponds where the frogs gather to mate. The males, who don't quite grow as large as the females, find a place at the edge of a pool and let out a sound unlike any other frog. Here's what they sound like: (ouuuuuu sound in raising pitch) It's got to be one of my favorite frog calls. Let's listen again because it's so fun. What lady could resist that? The male mounts an interested female and she'll lay her hundreds to thousands of eggs in the water to be fertilized by the male as they're laid. These take a few days to hatch, and the tadpoles take about two months to develop into juvenile frogs.

Mexican burrowing frog tadpoles are filter feeders, eating any floating organic material in the water column. After leaving the water, the frog digs into the earth and uses its special tongue to gather ants, termites, and other insects living underground. Most frogs flick their tongue out with a flipping motion, but a Mexican burrowing toad’s tongue comes straight out, no flip necessary. It's believed this method, somewhat like an anteater licking up its prey, is specialized for underground feeding.

In size, these toads reach about 3 inches, 8 centimeters, long, although they can super inflated their body to ward off predators. When faced with an opponent, a Mexican burrowing toad will essentially turn into a balloon-shaped ball with a pointed nose sticking out of one end. Of course, it's likely that they rarely encounter predators due to their fossorial nature. Their tadpoles are even kept safe because they're laid in pools that don't house larger animals, but they are sometimes cannibalistic upon one another and they may face competition from other tadpole species.

Something really noteworthy about Mexican burrowing toad tadpoles is that they change color depending on the time of day. During the day, they're dark across their back with a silver belly, but at night they become transparent! It's not fully understood why this occurs, do you have a hypothesis? Mexican burrowing toads are also able to survive long periods of time without water. At least in captivity, an individual remained underground without eating for over eighteen months before becoming active again after being hydrated. This implies that these frogs may be able to replicate this behavior in the wild, so it's difficult to say how long they might live!

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