Turtles are reptiles often associated with aquatic environments, leading many to wonder if they can breathe underwater. Like all reptiles, turtles rely on lungs for respiration, meaning they must periodically surface for atmospheric oxygen. This fundamental need for air shapes their underwater behavior, despite unique adaptations that allow some species to remain submerged for extended periods.
How Turtles Truly Breathe
Turtles primarily breathe using lungs, a system similar to that of mammals and birds. They must surface regularly to inhale oxygen and exhale carbon dioxide. Their lungs are situated beneath the carapace. Since their rigid shells prevent rib cage expansion, turtles employ specialized muscles attached to the pelvic and shoulder girdles and the plastron to pump air in and out. Some species can also adjust lung pressure by moving their limbs.
This respiratory mechanism allows them to draw air through their nostrils and glottis into the trachea, leading to their lungs. Within the lungs, oxygen diffuses into the bloodstream while carbon dioxide is released. Their primary method of obtaining oxygen is from the air, not from water.
Specialized Underwater Respiration
Some aquatic species have evolved accessory respiratory mechanisms to extend their time underwater. One notable adaptation is cloacal respiration, often colloquially termed “butt breathing.” Certain freshwater turtles absorb oxygen from water through highly vascularized sacs, known as bursae, located in their cloaca. They actively pump water in and out of these sacs, allowing dissolved oxygen to diffuse across small, finger-like projections called papillae into the bloodstream. This method is particularly effective for species that hibernate underwater in cold conditions, where metabolic needs are lower.
Another specialized technique is pharyngeal respiration, observed in certain species like softshell turtles. They absorb oxygen through vascularized tissues in their throat. These tissues, lined with villi, increase the surface area for gas exchange, allowing some softshell turtles to acquire up to 30% of their oxygen from the water. These supplementary methods are significantly less efficient than lung breathing and primarily augment oxygen intake during dives or periods of inactivity. Beyond these anatomical adaptations, turtles can also drastically reduce their metabolic rate while submerged, minimizing oxygen consumption. In situations of extreme oxygen deprivation, they can temporarily switch to anaerobic respiration, generating energy without oxygen, though this process results in a buildup of lactic acid and has a finite duration.
The Limits of Underwater Endurance
Despite impressive physiological adaptations for underwater survival, turtles remain air-breathing animals and cannot live indefinitely beneath the surface. Specialized cloacal and pharyngeal respiration, along with metabolic depression, extend dive times but do not eliminate the fundamental requirement for atmospheric oxygen. Turtles must eventually return to the surface to replenish oxygen stores through their lungs.
Inability to surface for air can have severe consequences, leading to drowning. This can occur if a turtle becomes entangled in discarded fishing gear, plastic debris, or other underwater obstructions. Entanglement prevents them from reaching the surface, cutting off their access to the air they need to survive. While highly adapted to aquatic life, their survival remains dependent on periodically accessing air above water.