Spiders are widespread predators, occupying nearly every terrestrial habitat and consuming an immense biomass of insects annually. Their abundance makes them a significant resource, positioning them as a foundational link in countless food webs. A diverse group of animals has evolved to capitalize on this readily available protein source, transforming the spider from hunter into the hunted. Spiders thus play a dual role in the ecosystem, acting as regulators of insect populations and as sustenance for other wildlife.
Generalist Vertebrate Hunters
The most common predators of spiders are generalist insectivores across the vertebrate classes, consuming spiders opportunistically as part of a varied diet. Birds are numerous consumers; common species like wrens, robins, and sparrows routinely include spiders in their foraging. The great tit, a small European bird, demonstrates a preference for spiders when feeding its nestlings, sometimes making up a majority of the food brought to the young.
Reptiles and amphibians also rely on spiders. Lizards such as geckos, chameleons, and anoles actively hunt them, and their introduction to an area can significantly reduce local spider populations. Amphibians like frogs and toads frequently ambush spiders near the ground or water. Fish, including trout, will readily snatch spiders that fall onto the water’s surface.
Small mammals, including shrews and bats, also target spiders while foraging in leaf litter or in the air. While most mammals do not specialize in arachnids, spiders provide valuable nutrients for these high-metabolism animals. For these vertebrate hunters, a spider is a convenient, calorie-dense meal that supplements their primary intake of insects or other invertebrates.
Highly Specialized Insect Predators
A more focused threat comes from insect species that have evolved unique life cycles centered entirely on arachnid prey. The most prominent are the Pompilidae wasps, known as spider wasps or tarantula hawks, which are obligate parasitoids. The female wasp actively hunts large spiders, such as tarantulas, paralyzing them with a potent sting that leaves the victim alive but immobile.
After paralysis, the wasp drags the spider to a prepared burrow and lays a single egg on its abdomen. The spider becomes a living larder; when the wasp larva hatches, it consumes the paralyzed host from the outside in, targeting non-vital organs first. Other insects, such as centipedes, use venom-injecting claws to subdue and consume spiders, often capturing soft-bodied prey at night.
Spiders Eating Spiders
One intense threat spiders face comes from their own kind, a behavior known as araneophagy. This manifests as non-sexual cannibalism, where a larger spider preys on a smaller one, or as territorial aggression between individuals of similar size. Specialized spider-hunting spiders, such as certain spitting spiders, have adapted techniques specifically to bypass the defenses of their arachnid relatives.
The most recognized form of this behavior is sexual cannibalism, where the female consumes the male before, during, or after mating. This act is often related to the male’s size; smaller males are more likely to be consumed by a hungry female, who gains a nutritional boost for egg production. In extreme cases, like the Australian redback spider, the male actively somersaults into the female’s jaws during copulation, increasing his paternity success.
How Spiders Avoid Being Eaten
Spiders employ an array of physical and behavioral defenses to survive predation. Camouflage is a primary strategy, with many species exhibiting crypsis, or the ability to blend seamlessly into their background, such as bark, leaves, or flowers. Other spiders utilize mimicry, adopting the appearance of less palatable animals, such as ant-mimicking jumping spiders that resemble dangerous insects to avoid birds.
When camouflage fails, spiders rely on active defenses and escape mechanisms. Many orb-weavers drop instantly from their web on a silk dragline when disturbed, rapidly removing them from a predator’s vicinity. Larger spiders, like tarantulas, use urticating hairs—fine, barbed bristles flicked at an attacker—to cause irritation and serve as a deterrent. Some also use venom as a final-resort defense, while others feign death, a behavior called thanatosis, to deter predators.