Why do pests chew or gnaw on everything?

If one pest genuinely deserves the "chews everything" label, it's the rodent. A mouse's incisors grow roughly 0.4 millimeters every day for its entire life, and because those teeth are rootless (hypselodont), they never stop growing and never self-limit the way human teeth do. Left unworn, they overgrow into malocclusion, and an animal that can't close its jaw properly eventually starves. Gnawing is therefore not optional behavior driven by hunger or destructiveness — it's obligate maintenance, which is exactly why a house with no food left out anywhere still gets chewed wiring and gnawed trim.

Recent neuroscience adds an important layer to this. Duan and Emrick et al., publishing in Neuron in 2026, identified a touch-guided neural circuit that rewards gnawing with a dopamine release in the nucleus accumbens — the brain's reward center. Disrupting that circuit abolished gnawing behavior and caused severe malocclusion; activating it triggered the reward response directly. As the study's lead author put it, the old assumption was that gnawing was "a very passive behavior driven by mechanical considerations." It isn't — it's actively motivated, which helps explain why rodents gnaw at accessible edges even when there's no mechanical need to.

"Pests chew everything" quietly folds in a lot of animals that don't gnaw anything structural. Carpenter ants are the most commonly misunderstood: university extension entomologists at Penn State, the University of Maryland, and Michigan State are consistent that carpenter ants excavate wood to create nesting galleries — they do not eat the wood they remove, and they overwhelmingly colonize wood that's already softened by moisture or decay rather than sound lumber. Their presence is much more a symptom of an existing water problem than an independent chewing threat.

Mud daubers chew nothing whatsoever. These solitary wasps gather wet mud in their mandibles and plaster it into a tube-shaped nest, a construction behavior with no destructive component at all — the material moves toward the structure, not away from it. Spiders, ticks, fleas, and bed bugs, often mentally grouped with "gnawing pests" in a general sense of household threat, don't chew or damage property in any capacity.

It's worth distinguishing rodent gnawing from wood-destroying insects that genuinely consume material as food, because they're different mechanisms entirely. Subterranean termites and powderpost beetles actually digest wood cellulose or starch — that's a feeding relationship, and it's the one genuinely structural threat in this comparison. Rodent gnawing is mechanical tooth maintenance that happens to target whatever soft material is nearby; the material isn't food, isn't digested, and isn't sought out for nutritional value. Knowing which mechanism you're dealing with tells you what class of damage to expect and which professional actually fixes it.