The nutria (Myocastor coypus) is a large, semi-aquatic rodent that originated in South America, but is now established as an invasive species across many regions worldwide. Also known as the coypu, this mammal is built for an existence on the water, possessing partially webbed hind feet and a capacity for holding its breath. Its success in new environments is due to its powerful swimming and diving abilities, which allow it to exploit aquatic food sources and evade threats efficiently.
Maximum Submergence Duration
The maximum time a nutria can remain submerged is typically cited in the range of five to ten minutes. This extended duration is generally observed when the animal is under extreme duress, such as evading a predator or being pursued by humans. When frightened, nutria often retreat to the water and remain still near the bottom for several minutes until the perceived threat passes.
This maximum limit stands in contrast to the animal’s routine, everyday diving patterns. A typical foraging or exploratory dive is significantly shorter, often lasting between 30 seconds and one minute. These shorter dives are sufficient for gathering roots, tubers, and aquatic vegetation, reflecting an aerobic activity level rather than a desperate, oxygen-conserving effort.
Physiological Adaptations for Extended Dives
The nutria’s ability to sustain long dives is rooted in a suite of specialized biological mechanisms that manage and conserve oxygen. Like other diving mammals, it exhibits the mammalian dive reflex upon submersion, which is an autonomic response to being underwater. This reflex triggers a significant reduction in the heart rate, a condition known as bradycardia, which drastically lowers the body’s overall oxygen consumption.
A second mechanism involves the redistribution of blood flow away from the limbs and non-essential organs. This peripheral vasoconstriction shunts oxygenated blood primarily to the heart, brain, and adrenal glands, ensuring that the most sensitive tissues remain perfused. The nutria’s blood also plays a role, though less pronounced than in marine mammals, in oxygen storage.
The nutria utilizes myoglobin in its muscle tissue, which acts as a localized oxygen reserve, facilitating the continued function of the muscles during a dive. Furthermore, the nutria possesses specialized valves in its nostrils and mouth that seal tightly, preventing water from entering the respiratory system or the oral cavity.
Typical Underwater Behavior
The nutria’s diving ability is primarily an adaptation for feeding and escaping danger within its marsh and wetland habitat. Submerging allows the animal to access the roots and rhizomes of aquatic plants, which are a major component of its diet. This foraging often involves digging and manipulating vegetation underwater.
A unique feature facilitating this behavior is the placement of the nutria’s lips, which are capable of closing behind the front incisor teeth. This adaptation allows the nutria to use its large, orange-enameled incisors to clip or gnaw on plant material while its mouth remains sealed from the surrounding water. Evasion is another frequent reason for diving; when threatened by a terrestrial predator, a nutria will plunge into the water and swim long distances beneath the surface.
The eyes, ears, and nostrils are set high on the head. This placement enables the nutria to swim with minimal exposure, keeping its senses above the waterline while the rest of its body is submerged. Even the young are precocial, able to swim and feed on vegetation within hours of birth.