Which animal can stay under water longer?

Crocodiles: Dive longer with cardiac arrest

The largest and most dangerous reptiles for humans are the saltwater or saltwater crocodiles. They grow to be over six meters tall and weigh up to a ton. They not only feel good in salt water, but also in lakes, swamps, rivers and brackish water.

While young animals feed on fish and reptiles, adult animals also like to hunt larger mammals on the shore. These animals come there to drink. The crocodiles shoot out of the water at lightning speed, grab their prey and kill it by turning on their own axis with full force.

Saltwater crocodiles are best known from Australia, Indonesia and Papua New Guinea. But their actual habitat is much larger: it stretches from the Indian east coast and Sri Lanka to Micronesia, in the middle of the Pacific.

The animals can swim extremely far. Their metabolism helps them in this: on the one hand, the crocodiles are particularly good at building up body fat reserves, on the other hand they are also very economical.

The pulse also drops in apnea divers

Diving reflex triggers a low pulse

Saltwater crocodiles make use of the diving reflex, a protective mechanism shown by all living things that breathe through their lungs. The resting nerve (parasympaticus) triggers this reflex. This nerve receives its stimuli from receptors in the nose, upper lip, jaw and tongue.

Even when a person descends, breathing comes to a standstill at first. This prevents water from entering the lungs. At the same time, the pulse rate decreases. In normally trained people, the heartbeat drops by a few beats per minute, for example from 80 to 75 or 70.

In popular sports, freedivers can hold their breath for two to three minutes. Record apnea divers manage to reduce their heart rate to just 24 beats per minute through years of training and skillful yoga and meditation techniques. Such top athletes can hold their breath for more than ten minutes.

Different stimuli intensify the diving reflex: The holding of the air itself, the cold water, the rising ambient pressure and the changed oxygen and carbon dioxide levels in the blood act on the many nerve receptors. Taken together, the brain is then signaled: do not breathe - reduce circulatory activity!

A crocodile can stay underwater for up to an hour

Crocodile as a high-performance diver

Apnea divers can only dream of the pulse values ​​of a saltwater crocodile: the reptile's heart almost stands still. It only beats every forty seconds when the animal is completely relaxed underwater. A saltwater crocodile can easily dive for an hour.

And if the heart is barely beating and the crocodile is barely breathing, it is hardly burning any energy. Because an estuarine crocodile can eat all kinds of fat reserves when the times are good, which it then deposits in its heavy tail, it can get by without food for many months on its long journeys through the ocean. A saltwater crocodile can survive without food for up to a year.

If it ventured too far inland during the rainy season, and the river or lake then seeped away and dried up, the animal can sometimes survive for a few months with its degraded metabolism until rain falls again. To do this, it digs itself in the mud of the last remaining water holes or retreats into cool caves. This is how crocodiles can get really old: Seventy years is not uncommon.