Reptiles are vertebrates with organ systems similar to those of mammals. However, they are ectothermic and rely on environmental temperature and behavior to control their core body temperature. They possess both renal and hepatic portal circulations, and predominantly excrete ammonia (especially aquatic species), urea (especially chelonians), or uric acid (especially snakes and lizards) depending on their evolutionary adaptations. Their RBCs are nucleated, and their metabolic rates are approximately 7–10 times lower than those of mammals. All reptiles exhibit ecdysis—a normal process by which the outer skin is periodically shed. Diurnal species require broad-spectrum light containing UVB (290-300 nm) for vitamin D3 synthesis and calcium homeostasis. Fertilization is internal, and females may produce eggs (oviparous) or live young (ovoviviparous).
Reptiles are not considered highly social creatures, and multiple-male groups can lead to intra-species aggression. Single-male, multiple-female groupings can work well for certain species, but the solitary reptile is often the healthiest pet. The life span of many reptiles can exceed 10–20 yr, requiring a long-term commitment from owners.
Reptiles are tetrapod vertebrates, creatures that either has four limbs or, like snakes, are descended from four-limbed ancestors. Unlike amphibians, reptiles do not have an aquatic larval stage.
Leopard gecko
