Amphibians
Eastern Narrow-mouthed Toad
Gastrophryne carolinensis · also called eastern narrow-mouthed toad
Some eastern narrow-mouthed toads live inside the burrow of an animal fully capable of killing and eating them: a tarantula. Researchers suspect it is a trade, shelter for the toad in exchange for eating ants that might otherwise threaten the spider’s eggs — one of the stranger tolerated partnerships in the animal world, and it still is not entirely understood why the spider allows it.
Overview
The eastern narrow-mouthed toad, Gastrophryne carolinensis, is a small amphibian of the southeastern United States, easily identified by its pointed head and tiny mouth. It specialises heavily on ants and termites, protected from their bites by a sticky, distasteful skin secretion.
An unlikely roommate
In parts of its range, the toad shelters inside tarantula burrows, seemingly tolerated in what may be a mutually beneficial relationship. Its short, buzzing, sheep-like call gives away its presence after heavy rain triggers explosive breeding in temporary pools, though otherwise it stays hidden underground or in leaf litter most of the time.
Status
Least Concern — common and widespread across the southeastern US, secure thanks to broad habitat tolerance and a reliable ant-and-termite food supply.
Eastern Narrow-mouthed Toad: common questions
Why does the eastern narrow-mouthed toad live in tarantula burrows?
Researchers studying this unusual relationship believe the toad benefits from the shelter and protection a tarantula burrow provides, while the tarantula may benefit from the toad eating small ants and other invertebrates that could otherwise threaten the spider's own eggs, suggesting a mutually beneficial arrangement despite the tarantula being fully capable of killing and eating the much smaller toad. The exact mechanism by which the toad avoids being eaten, whether through some form of chemical signal, scent recognition, or simple tolerance, is not yet fully understood and remains an area of ongoing scientific interest.
How does the eastern narrow-mouthed toad avoid being bitten while eating ants?
Its skin produces a sticky, distasteful secretion that is thought to provide some physical and chemical protection against the bites and stings of the ants and termites that make up the bulk of its diet, reducing the risk involved in preying so heavily on insects capable of swarming and biting defensively. This adaptation, combined with quick, precise strikes using its small, sticky tongue, allows the toad to specialise on a food source that would be considerably riskier for many other frogs and toads to exploit so heavily.
What does the eastern narrow-mouthed toad's call sound like?
Its breeding call is a short, nasal, buzzing sound often compared to a sheep's bleat or an insect's buzz, quite distinct from the more melodic trills, chirps, or peeps typical of many other small frog and toad species found in the same region. Because the toad itself spends much of its time hidden in leaf litter or underground, this distinctive buzzing call, usually heard after heavy rain during the breeding season, is often the clearest and most reliable sign of its presence in a given area.
Why is the eastern narrow-mouthed toad's head shaped so differently from other toads?
Its narrow, pointed head and small mouth are considered specific adaptations suited to a diet focused heavily on tiny prey such as ants and termites, allowing precise, targeted feeding using a small, sticky-tipped tongue rather than the wider gape needed by frogs and toads that regularly tackle larger insect or invertebrate prey. This distinctive head shape is one of the clearest visual differences separating narrow-mouthed toads from the more familiar wide-mouthed toads and frogs most people are used to seeing.