The ribs may spread, flattening the top of the body, or the body may just expand slightly. This makes the monitor look larger than it actually is. It often raises up on its hind legs just before attacking. The tail delivers a well-aimed blow. Monitors tend to swallow their prey whole, like snakes.
Monitors are daytime lizards and most species actively search for food.
Combat between males is frequently observed during the breeding season in some species. Monitors lay 7 to 35 soft-shelled eggs, usually deposited in holes in riverbanks or in trees along water courses. The Nile monitor often lays its eggs in termite nests. Eggs are 2 inches long with leathery shells. Incubation is 8 to 10 weeks.