After irradiating rodent food, Steenbock discovered the rodents were cured of rickets. The red squirrel is an arboreal, primarily herbivorous rodent. Malaria protozoa are diversified into primate, rodent, bird, and reptile host lineages. Glue board traps are used primarily for rodent and insect control indoors. Remains of pig, deer, rodent, reptile, monkey, crab and fish were found. Humans usually become infected through the bite of an infected rodent flea. The plural for the small rodent is always "mice" in modern usage. Notable mammals include the giant anteater, jaguar, and the capybara, the world's largest rodent. Sexual dimorphism occurs in many rodent species. The aircraft is named after the Chipmunk, a small rodent. The beaver (genus Castor) is a large, primarily nocturnal, semiaquatic rodent. It often makes its home in rodent burrows and is nocturnal. Ecologists consider this rodent to be a keystone species. People sometimes attempt to limit rodent damage using repellents. Balsam fir oil is an EPA approved nontoxic rodent repellent.