Compared to many other snakes, vipers often appear rather sluggish. Most are [[Ovoviviparity|ovoviviparous]], giving birth to live young, but a few lay eggs; the word "viper" is derived from Latin ''vivo'' = "I live" and ''pario'' = "I give birth".<ref name="Sch02">Schuett GW, Höggren M, Douglas ME, Greene HW. 2002. Biology of the Vipers. Eagle Mountain Publishing, LC. 580 pp. 16 plates. ISBN 0-9720154-0-X.</ref>

Viperid snakes are found in the [[Americas]], [[Africa]] and [[Eurasia]]. In the Americas, they are native from southern [[Canada]], through the [[United States]], [[Mexico]], [[Central America]] and into [[South America]]. The adder branch of the Viperidae family contains the only venomous snake found in the [[United Kingdom]].<ref name="McD99"/> Wild viperids are not found in [[Australia]].