Do Dogs Keep Rats Away?

Predator cues create what ecologists call a "landscape of fear" — prey animals overestimate risk near a predator's scent and spend more time hidden, which can reduce sightings. But the landmark urban study on this exact question, led by Dr. Michael H. Parsons of Fordham University (Parsons et al., 2018, Frontiers in Ecology and Evolution), found that predator presence changed rat behavior far more than rat numbers. As Parsons put it: "People see fewer rats and assume it's because the cats have killed them — whereas it's actually due to the rats changing their behavior." A family dog dozing indoors delivers even less pressure than the free-roaming predators in that study. A dog may make your yard modestly less inviting to rats passing through, but it will not evict a colony living in a burrow or wall void.

Terrier breeds were developed over centuries specifically to hunt and kill rats — Jack Russell terriers, rat terriers, Patterdale terriers, Cairn terriers, and Bedlington terriers among them — and remain effective ratters, historically used on farms, in barns, and aboard ships. That's a genuinely different mechanism from passive deterrence: it's a working dog killing rats one at a time, not a family pet repelling them by smell. It's real, but note the limits — even a skilled ratter can't find rats nesting inside a wall cavity or attic insulation, and won't do anything to stop a new rat from entering tomorrow.

Rats reinvade through unsealed openings regardless of what pets share the property — university extension research is explicit that rodents recolonize any structure with an accessible ½-inch gap. So even on a property with an active ratting terrier, an indoor infestation still requires the same fix as everywhere else: seal entry points and trap the rats already inside. A dog is a genuinely useful supplement, especially on a rural or wooded New Hampshire property with barns, sheds, or woodpiles, but don't let it delay dealing with rats that are already indoors.