Are mammals the only group that gives live birth?

No, mammals are not the only animals that give live birth. There are several species of reptiles, fish, amphibians, and even insects that give birth to live young. For example, some reptiles such as the rattlesnake and the common lizard give birth to live offspring, as do some fish like the blue shark and the Pacific Ocean perch. Among amphibians, the common toad and the African bullfrog are examples of live-bearing species. The giant water bug, an insect, is another example of a species that gives birth to live young.