Animals Keeping Warm

This appealing quartet of economical, full-color photographic picture books portrays animals feathered, furred, scaled and finned, as well as insects: how they survive in changing climatic conditions, among predators and as organisms constantly obliged to adapt to life's hazards. One of the series' strong points is a clean and simple design; though dominated by pictures, most pages include captions, each equipped with an arrow directing the reader to the correct image. The photographs themselves are clear, vivid, friendly and only occasionally contrived (a portrait of mallard ducklings huddled in fleecy softness looks too good to be true, like a greeting card). Factual information is succinctly presented, reliable and sometimes surprising (hippopotamuses have been known to suffer from sunburn and rabbits with dirty feet can't run fast). Ages 4-8. (Apr.)