Another of Pringle's competent reports, this is a census of feral animals in North America. Beginning with birds, Pringle reports that, ""overall,"" health officials do not consider pigeons a health hazard; however, the tropical monk parakeets brought in as pets can cause serious crop damage when they escape and breed in the wild. There are, we learn, well established American populations of both true wild pigs (originally imported from the Ural Mountains) and feral pigs. The latter, perhaps two million of them, become quite different from their tame ancestors--hairy, rangy, wary, and alert--after a few generations in the wild. As for dogs, scientific observers have found that free-ranging pets are far more numerous and do more damage (killing livestock, for example) than true feral dogs. Feral cats (many abandoned in vacation areas at the end of summer) really don't kill many songbirds, as has been charged--but they might be carriers of toxoplasmosis, which kills several thousand American children each year. Feral burros, who compete with wildlife (such as the bighorn sheep) as well as with livestock, have experienced a rocky history of protection, sale for slaughter, adoption, and systematic shooting. Both burros and feral horses, also the subject of controversy between ranchers and humane societies, have a strong social structure which varies according to the environment. We need to know more, says Pringle, about the wild horse population and its impact on the range. For the present, an informative status report on a cross-section subject of likely interest.