Bruce Hecker, director of husbandry in ~ the southern Carolina Aquarium in Charleston, S.C., provides an answer that gives new an interpretation to the expression "half asleep."


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Marine mammals such as whales and also dolphins spend their entire lives at sea. So how deserve to they sleep and also not drown? monitorings of bottlenose dolphins in aquariums and also zoos, and also of whales and also dolphins in the wild, present two an easy methods of sleeping: they either remainder quietly in the water, vertically or horizontally, or sleep while swimming slowly next to an additional animal. Individual dolphins also enter a deeper kind of sleep, mainly at night. The is referred to as logging since in this state, a dolphin resembles a log in floating at the water"s surface.

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When naval mammals sleep and swim in ~ once, they space in a state comparable to napping. Young whales and dolphins in reality rest, eat and sleep if their mom swims, towing them follow me in she slipstream--a placement called echelon swimming. At this times, the mom will additionally sleep on the move. In fact, she cannot stop swimming because that the very first several main of a newborn"s life. If she does for any type of length that time, the calf will start to sink; the is no born with sufficient body fat or blubber come float easily.

Lots of swimming will tire one infant, creating a weak pet susceptible to infection or attack. Adult masculine dolphins, which typically travel in pairs, frequently swim slowly side through side together they sleep. Females and young travel in larger pods. They might rest in the same general area, or companionable animals may pair for sleeping while swimming.

While sleeping, the bottlenose dolphin shuts under only half of its brain, together with the the opposite eye. The other fifty percent of the brain stays awake in ~ a short level of alertness. This attentive next is used to watch for predators, obstacles and also other animals. It additionally signals as soon as to rise to the surface ar for a fresh breath that air. After about two hours, the pet will reverse this process, relaxing the active side the the mind and awaking the rest half. This sample is often called cat-napping.

Dolphins typically sleep at night, yet only because that a pair hours at a time; they are often active late at night, possibly matching this alert period to feed on fish or squid, i m sorry then rise from the depths. Bottlenose dolphins, based upon electroencephalogram (EEG) readings, invest an average of 33.4 percent of your day asleep. The is no clear whether cetaceans experience dream sleep. Rapid Eye motion (REM)--a characteristic of deep sleep--is hard to discern. Yet a pilot whale was detailed as having actually six minutes of REM in a solitary night.

To protect against drowning throughout sleep, that is critical that naval mammals retain control of their blowhole. The blowhole is a flap of skin that is believed to open and close under the voluntary manage of the animal. Although quiet a issue of discussion, many researchers feel that in order to breathe, a dolphin or whale have to be conscious and alert to recognize that that is blowhole is in ~ the surface.

Humans, the course, deserve to breathe while the aware mind is asleep; ours subconscious mechanisms have regulate of this involuntary system. But equipped with a voluntary respiratory tract system, whales and also dolphins must keep part of the mind alert to trigger each breath.

Other methods assist marine mammals to hold their breath longer than other types of mammals can. Naval mammals have the right to take in much more air v each breath, together their lungs space proportionately larger than those in humans. In addition, lock exchange more air with each inhalation and exhalation. Their red blood cells likewise carry an ext oxygen. And when diving, maritime mammals" blood travels only to the components of the body that need oxygen--the heart, the mind and the swim muscles. Digestion and any other processes have to wait.

Finally, these animals have a higher tolerance because that carbon dioxide (CO2). Their brains perform not cause a breathing solution until the levels of CO2 are much higher than what humans can tolerate. These mechanisms, part of the marine mammal diving response, room adaptations to life in an aquatic environment and assist during the procedure of sleeping. Cetaceans minimize the variety of breaths they take during rest periods; a dolphin could average 8 to 12 breaths a minute when fairly active just to have their breathing rate drop come 3 come 7 per minute when resting.

It is in reality rare for a naval mammal to "drown," together they won"t breathe underwater; however they carry out suffocate indigenous a lack of air. Being born underwater can reason problems because that newborn whale and also dolphin calves. The is the touch of waiting on the skin i m sorry triggers that first, an essential breath. And necropsies sometimes show that an pet never gets to the surface to take its first breath the air. The same trouble can take place when an pet is captured in a fishing net. If unable to with the surface, or if in a panic, the pet may dive deeper, where it will be can not to breathe and also suffocate.

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Obviously resting safely at sea have the right to pose problems, however the naval mammal system has addressed them.