Open Library - открытая библиотека учебной информации

Открытая библиотека для школьников и студентов. Лекции, конспекты и учебные материалы по всем научным направлениям.

Категории

Биология Dolphins
просмотров - 268

Dolphins are warm blooded like man, and give birth to one baby called a calf at a time. At birth a bottlenose dolphin calf is about 90-130 cms long and will grow to approximately 4 metres, living up to 40 years. They are highly sociable animals, living in pods which are fairly fluid, with dolphins from other pods interacting with each other from time to time.

Dolphins use their powerful tail flukes in an up and down motion to move through the water. They also use their tails when hunting, hitting a fleeing fish up into the air with their tail, stunning it, then scooping the fish up when it falls back into the water. A dolphin slapping its tail on the water in the wild may be a sign of annoyance, or a warning to other dolphins of danger.

Their teeth are interlocking rows of conical pegs, suitable for holding slippery fish. They eat their fish whole, head first. In the wild an open mouth is a sign of aggression, as is head nodding. A sign of greater aggression is violent jaw clapping.

Dolphins breathe through their blowhole located at the top of their head. A dolphin may empty and refill its lungs in less than a fifth of a second. As the dolphin breathes the air leaves the blowhole at speeds of over 100mph. Complex nerve endings around the blowhole sense pressure changes so the dolphin knows exactly when the blowhole is in or nearing the air and can be opened. Water in a dolphin's blowhole will actually drown it so powerful muscles close the blowhole as it dives under the water again.

The dolphin's eyes produce a special slippery secretion which protects the eyes from foreign objects and water friction. To sleep, a dolphin must shut down only half of its brain, as its breathing is under voluntary control. Dolphins take short cat-naps, floating just below the surface, then slowly rising to breathe. Often dolphins are very active during night time, for some this is their main feeding time.

The dolphin's skin is completely smooth allowing the dolphin to move easily through the water, and also reduce heat loss.

Dolphins are able to dive to great depths, and also leap to great heights. They may leap to avoid predators or to show how powerful they are to females at mating time. Noisy splashing jumps may also be used to herd fish. Bottlenose dolphins can dive to depths of over 500m

Dolphins carry their young inside their womb and gestation is about 12 months for a bottlenose. The baby emerges tail first, and will suckle from its mother for up to 4 years (a calf may stop suckling sooner depending on circumstances).

The baby will however stay with its mother for between 3-6 years, during which time it learns all about feeding techniques, social interaction and group foraging.

Dolphins have defined home ranges, an area in which they will roam and feed. Though dolphins live in small groups called pods, these pods can be quite fluid and dolphins can be interacting with dolphins from other pods from time to time. If another dolphin is drowning, other dolphins will come to it's aid, supporting it with their bodies so it's blowhole is above the water allowing it to breathe.


Читайте также


  • - Dolphins

    Dolphins are warm blooded like man, and give birth to one baby called a calf at a time. At birth a bottlenose dolphin calf is about 90-130 cms long and will grow to approximately 4 metres, living up to 40 years. They are highly sociable animals, living in pods which are fairly fluid, with dolphins from other pods interacting with each other from time to time. Dolphins use their powerful tail flukes in an up and down motion to move through the water. They also use their tails when hunting,... [читать подробенее]