08-09-2009 by Trellius

"How many species of dolphin are there?"

Well, why don't we have a look? Here is a list of the 32 KNOWN species.

"What are some of their characteristics?"

Some characteristics remain more or less the same for all species:

Dolphins swim by moving their tail flukes up and down to propel them through the water.

"Are dolphins very social?"

Social structure

Bottlenose dolphins live in groups called pods. A pod is a coherent long-term social unit and it's size varies significantly with its composition. In the wild, pod composition and structure are based largely on age, sex, and reproductive condition. For example: subadults typically occur in mixed-sex and single-sex groups.

Adult males are often observed alone, or in pairs or occasional trios. Adult males commonly move between female groups in their range, and may pair up with females for brief periods. They rarely associate with subadult males.

In general, size of pods tend to increase with water depth and openness of habitat. This may be correlated with foraging strategies and protection.

Several pods may join temporarily (for several minutes or hours) to form larger groups called herds or aggregations. Up to several hundred animals have been observed traveling in one herd.

Social behavior

Dolphins in a pod appear to establish strong social bonds. Behavioral studies suggest that certain animals prefer association with each other and recognize each other after periods of separation. Field observations suggest that mother-calf bonds are long-lasting.

Dolphins often show aggression by scratching one another with their teeth, leaving superficial lacerations that soon heal. Traces of light parallel stripes remain on the skin of the dolphin. These marks have been seen in virtually all species of dolphins. Dolphins also show aggression by emitting bubble clouds from their blowholes.

During courtship, dolphins engage in head-butting and tooth-scratching, and sometimes include twisting and nuzzling.

"OK where do baby dolphins come from?"

Gestation period is about 12 months.

Birth seasons

A female dolphin can potentially bear a calf every two years, but calving intervals generally average three years.

Calving

Calves are born in the water. Deliveries can be either tail-first or head-first. The umbilical cord snaps during or soon after delivery. Sometimes an assisting dolphin may stay close to the new mother and calf. Although this assisting dolphin often is referred to as an "auntie" dolphin, it may be male or female. This "auntie" dolphin is often the only other dolphin a mother allows near her calf.

The calf is approximately 106-132 cm. n the first few days after birth, the dorsal fin and tail flukes are flaccid and pliable, but gradually become more stiff. Calves are darker than adults and show several vertical, light-colored lines on their sides, a result of fetal folding. These lines disappear within six months.

Care of the young

Calves nurse under water, close to the surface. The calf suckles from nipples concealed in abdominal mammary slits. Observations in zoological parks show that nursing usually begins within six hours of birth. A calf nurses as often as four times per hour for the first four to eight days.Each nursing instance usually lasts only about five to ten seconds. A calf nurses three to eight times per hour throughout the day and night.

Milk is composed of 33.0% fat, 6.8% protein, and 58.3% water (Oftedal, 1984), with traces of lactose. The rich milk helps the baby rapidly develop a thick insulative layer of blubber. A calf may nurse for up to 18 months. A mother dolphin stays close to her calf and attentively directs its movements. The baby swims close to its mother and is carried in the mother's "slip stream," the hydrodynamic wake that develops as the mother swims. This helps the baby to swim and enables the mother and calf to stay up with the group.

Related: Dope Ass Dolphin Section Part Two, Dope Ass Dolphin Section Part One