Spiders are renowned predators that utilize an arsenal of silk and venom to capture prey, but they are far from the top of the food chain. These eight-legged arthropods are a widely consumed food source, making them a significant component of many terrestrial and aquatic food webs. Their role as prey extends across multiple kingdoms, providing a nutrient-rich meal for a diverse array of animals. The variety of creatures that eat spiders highlights a complex ecological dynamic where different species have developed unique methods to overcome arachnid defenses.
Generalist Vertebrate Hunters
The most common predators of spiders are generalist vertebrates that consume them as an opportunistic part of a varied diet. Among the most prolific consumers are insectivorous and omnivorous birds, such as wrens, sparrows, and robins, which routinely pluck spiders from foliage and webs. Many bird species, including blue tits, actively feed spiders to their young because the arachnids contain high levels of taurine, a nutrient that promotes chick development.
Small mammals also pursue spiders as part of their ground-level foraging. Shrews, in particular, are constant hunters with extremely high metabolic rates that drive them to consume various invertebrates, including spiders. The Northern short-tailed shrew (Blarina brevicauda) is one of the few venomous mammals, using neurotoxic saliva to paralyze prey that it may then cache for later consumption. Amphibians and reptiles round out this group, with frogs and toads using their sticky, projectile tongues to capture terrestrial spiders, and lizards like geckos controlling spider populations in their habitats.
Specialized Invertebrate Hunters
The most dramatic predation events involve specialized invertebrate hunters, particularly the spider wasps in the family Pompilidae. These solitary wasps, often called tarantula hawks, are famous for their hunting strategy aimed at large spiders. The female wasp locates a host, such as a tarantula or a large wolf spider, and delivers a paralyzing sting directly to the spider’s nerve ganglia.
Once the spider is paralyzed, the wasp drags the massive arachnid back to a prepared burrow. The female wasp then deposits a single egg on the spider’s abdomen. Upon hatching, the larva bores a small hole and begins to feed, carefully avoiding the host’s vital organs to keep the spider fresh. This ensures the larva receives a sustained supply of living tissue until it is fully developed and ready to pupate.
Intraspecific and Inter-Arachnid Predators
Spiders face threats not only from other classes of animals but also from within their own ranks, including their own species and other arachnids. Cannibalism is common in the class Arachnida, often observed as juvenile predation where young spiders consume their smaller siblings. A more widely studied form is sexual cannibalism, where a female, such as a black widow, consumes the male before, during, or after mating. This behavior provides the female with a large protein boost for egg production.
Other non-spider arachnids are also predators of their cousins. Solifugids, known as sun spiders or camel spiders, are voracious, opportunistic hunters that utilize massive chelicerae, or jaws, to tear apart prey. These arachnids readily consume smaller spiders they encounter on the ground. Scorpions and large predatory mites will also feed on spiders, creating complex interactions where the hunter can quickly become the hunted.
Predator Adaptations for Overcoming Silk and Venom
Predators have evolved various tools and behaviors to bypass the spider’s primary defenses of silk and venom. For generalists like birds, the venom of most spiders is not a concern, as it requires injection into the bloodstream to be effective, and the bird’s digestive system neutralizes the toxins. Birds also exhibit “kleptoparasitism,” snatching insects or the spider itself from an orb web without becoming entangled.
Specialized predators, like parasitic wasps, avoid the silk defense by chewing through the web or using superior strength to drag the paralyzed host out. Some spiders, such as the Argiope orb-weavers, build conspicuous silk decorations called stabilimenta that may function as a visual defense to deter mud-dauber wasps from attacking.