The engine room of the island's food web and a rat that almost nobody sees on purpose. It is a
stocky, grizzled brown rodent of 80 to 150 g with coarse, stiff guard hairs — the "hispid" of the
name — and a statewide Texas distribution; the subspecies of the Rio Grande Plains is *S. h.
berlandieri* (NSRL). It lives in tall grass, cutting a network of runways five to eight centimetres
wide through the base of the sward and building a globular grass nest about 12 cm across, either in
a clump or underground.
Two facts make it matter here. It breeds prodigiously — several litters a year of two to ten young
after a 27-day gestation — and its populations swing through booms and crashes driven by disease
(NSRL). When cotton rats are abundant, the island's coyotes, harriers, owls and snakes have an easy
year; when they crash, predators switch to whatever else is available, including ground-nesting
birds. Cotton rats also eat the eggs of ground-nesting birds themselves, which puts them on both
sides of the ledger on an island full of nesting terns and plovers.
Observe responsibly
Wildlife, tides and access conditions change. Keep a respectful distance, do not feed wildlife, stay out of dunes and marked nesting areas, and use current official rules before fishing or handling any catch.