Amphibians
Sheep Frog
Hypopachus variolosus · also called sheep frogs, Mexican sheep frog
The sheep frog spends most of its life hidden underground, emerging mainly after heavy rain to do the one thing that gave it its name: bleat. Its breeding call is a drawn-out, nasal sound close enough to an actual sheep that plenty of people hearing it for the first time genuinely look around for livestock.
Overview
The sheep frog, Hypopachus variolosus, is a small, plump, pointed-snouted amphibian found from southern Texas through Mexico and Central America. It specialises on ants and other tiny invertebrates, sheltering in loose burrowed soil or under debris for most of its life.
A bleat, not a leap
Rather than relying on speed to escape danger, the sheep frog stands its ground behind a distasteful skin secretion, a chemical defence better suited to its small, slow-moving body than any attempt to flee. Breeding is triggered by heavy rain, with large numbers gathering quickly in temporary pools.
Status
Least Concern — widespread and adaptable across grassland and disturbed habitat throughout its range, secure as long as loose soil and temporary breeding water remain available.
Sheep Frog: common questions
Does the sheep frog's call really sound like a sheep?
Yes, the male's breeding call is a distinctive, drawn-out, nasal bleating sound that many people who hear it for the first time genuinely mistake for an actual sheep somewhere nearby, a close enough resemblance that it is the direct source of the species' common name in English. This unusual, sheep-like quality makes the call one of the more immediately memorable and easily identifiable amphibian calls within its range, even for listeners with little prior experience identifying frog and toad species by sound.
How is the sheep frog related to the eastern narrow-mouthed toad?
Both species belong to the same broader group of narrow-mouthed toads and share a similar small, plump body with a distinctly narrow, pointed snout adapted to a diet focused heavily on ants and other tiny prey, along with broadly similar defensive reliance on distasteful skin secretions rather than rapid flight. They are separate species with somewhat different geographic ranges, with the sheep frog found further south and west through Mexico and Central America, but their shared body plan, diet, and general ecology make them close ecological counterparts within their respective ranges.
Why does the sheep frog rely on skin secretions instead of running away from danger?
As a small, relatively slow-moving amphibian without strong jumping or sprinting ability compared with many other frog species, the sheep frog has instead evolved a chemical defence, producing distasteful or irritating skin secretions that make it an unpleasant, and potentially harmful, meal for many potential predators. Remaining still or adopting a defensive posture rather than attempting to flee allows this chemical defence time to have its deterrent effect, which is generally a more reliable survival strategy for the sheep frog than trying to outrun a faster predator.
When is the best time to see or hear a sheep frog?
Because the species is a committed burrower that spends much of its life hidden underground or under surface debris, it is most likely to be encountered and heard calling during and immediately after significant rainfall events, when large numbers of individuals emerge together to breed in temporary pools and flooded low-lying areas. Outside of these rain-triggered breeding events, sheep frogs are considerably more secretive and much less likely to be seen or heard going about their day-to-day burrowing and foraging activity.