Spiders do eat frogs. This predatory interaction occurs in various parts of the world, demonstrating the diverse diets some spider species maintain. It shows how unexpected hunters can capture prey much larger than themselves.
Spider Species and Hunting Methods
Over 100 spider species have been documented preying on frogs in natural environments. Around 85% of these incidents involve web-less spiders known as cursorial hunters. These predators, such as wandering spiders (Ctenidae), wolf spiders (Lycosidae), and fishing spiders (Pisauridae), stalk their prey rather than relying on webs.
Wandering spiders are generalist predators, hunting frogs at night across forest floors. Wolf spiders also hunt frogs in various habitats, including dense ground cover. Fishing spiders, semi-aquatic arachnids, typically wait at the water’s edge, detecting vibrations from passing prey like small fish, tadpoles, or frogs.
Upon detecting prey, fishing spiders pounce, subduing their catch under their bodies. Spiders kill frogs by injecting neurotoxins, which incapacitate the prey and begin the digestive process.
Spiders are often smaller than their amphibian prey, with most frog victims averaging around 2.76 cm. However, large species like the Goliath bird-eater tarantula can consume frogs up to 9 cm.
Ecological Context and Rarity
Spider predation on frogs is not common in the broader ecological landscape. Most spider species primarily consume insects, with frogs serving as a supplementary food source. Over 80% of recorded incidents occur at night, as many frog-eating spiders are nocturnal.
Frog-eating spiders are found on all continents except Antarctica, but incidents are most frequently documented in warmer regions, particularly in the Neotropics. Specific habitats, such as areas near water bodies where fishing spiders reside, or dense leaf litter in forests, can increase the likelihood of these interactions. The presence of invasive plants, like Japanese stiltgrass, can also create favorable conditions for wolf spider populations, leading to increased predation on small amphibians.
All life stages of frogs, from eggs and tadpoles to adult individuals, are vulnerable to spider predation, though most reports involve post-metamorphic frogs. Some small microhylid frog species exhibit a symbiotic relationship with certain tarantulas. These frogs possess skin toxins that make them unpalatable to the spiders, allowing them to coexist within the tarantula’s burrow. In this arrangement, frogs may benefit from protection against other predators, while potentially consuming small insects that could threaten the tarantula’s eggs.