Common Bottlenose Dolphin

## Description

Bottlenose dolphins are the most well-known and common type of dolphin. They feature front flippers, flukes, and a dorsal fin, which they use for swimming. The dorsal fin, positioned near the middle of the back, is tall and curved. These dolphins are usually black to a light gray, with white bellies, which are sometimes slightly pink. This coloring makes it hard to see them, from both above and below. Sometimes they have spots on their bellies and a stripe from the eye to the base of the flipper. These dolphins have 18 to 28 conical-shaped teeth on each side of each jaw.

## Distribution

Common bottlenose dolphins are found in all of the world's seas, both tropical and temperate. Some populations remain in one area, while others migrate extensively. Some populations live offshore and some inshore. The coastal dolphins appear to adapt to warm, shallow waters. They can be found in harbors, bays, lagoons, estuaries, and occasionally in rivers. Offshore dolphins, however, are adapted to cooler, deeper waters.

## Behavior

Bottlenose dolphins are very social animals. Typically living in groups ranging from just a few individuals to more than 100, they form several types of groups, which include nursery groups, juvenile groups, and groups of adult males. They engage both in aggressive behavior, such as biting, ramming, and tail slapping; and behavior of bonding and acceptance behavior, such as rubbing and stroking. When feeding, Common bottlenose dolphin pods often work as a team to harvest schools of fish, though they also hunt individually. Dolphins search for prey primarily using echolocation, which is a form of sonar. They emit a vast range of squeaks, grunts, and whines, which are categorized into three groups: echolocation clicks, whistles, and pulse sounds. Dolphins also communicate through touch.

## Diet

Common bottlenose dolphins are carnivores (piscivores) and usually eat eels, squid, shrimp, and a wide variety of fishes. Each day an adult can eat 15-30 pounds (6.8-13.5 kg) of food. They do not chew their food with their teeth. Instead, they swallow it whole and head first in order to avoid spines that feature on many of the fish they like to eat.

## Reproduction

Bottlenose dolphins are polygamous and don't form pair bonds. Breeding can take place at any time of the year, but occurs mostly in the spring, with a smaller peak in the fall. The gestation period lasts for about 12 months, after which one calf is born. A female nurse until the calf reaches 18-20 months. These dolphins give birth every 3 to 6 years, females usually fall pregnant soon after weaning, and they can continue to give birth until their late forties. The calves can be born any time during the year, with most born during the warmer months. Females usually reach reproductive maturity at an age between 5 and 10 years, and males between 8 and 13 years.

## Population

### Threats

Climate change is the main threat to bottlenose dolphins, due to the warming of seas and oceans, sending dolphins to colder waters outside their habitual ranges. As these dolphins are coastal creatures, they are affected by pollution, heavy boat traffic, and habitat destruction. Humans are their largest predators. Hunting still occurs in Peru, Sri Lanka, Taiwan, Japan, and other parts of the world. Fishing operations can injure or drown dolphins when they get accidentally caught in gear and nets.

### Number

According to IUCN Red List, the minimum worldwide estimate for the Common bottlenose dolphin is 600,000 individuals. Populations have been estimated for a few specific areas: northern Gulf of Mexico - 52,000, the eastern coast of North America - 126,000, eastern tropical Pacific - 243,500, Hawaii waters - 3,215, coastal California waters - 323, Japanese waters - 168,000, western European continental shelf waters - 12,600, Mediterranean Sea - fewer than 10,000, Black Sea - at least several thousand. Overall, currently, Common bottlenose dolphins are classified as Least Concern (LC) on the IUCN Red List.

### Ecological niche

Dolphins have an important part of the ecosystem in that they are top-level predators, controlling populations of fish and squid and keeping the ecosystem balanced and healthy. The presence of bottlenose dolphins indicates a healthy marine ecosystem.

## Fun Facts

Bottlenose dolphins love riding on the bow waves behind boats.

Bottlenose dolphins sometimes interact with humans. One that was named Percy lived off the coast of Cornwall in England and followed the local fishing boats, was seen playing with their crab pots and would allow strangers to hold onto his dorsal fin while pulling them through the water.

When sleeping, bottlenose dolphins have one eye open while the other is closed. They need to be awake when they breathe. To keep from drowning when asleep only half of their brain goes to sleep. When the left brain is asleep, their right eye is shut and vice versa.

The United States and Russian military train bottlenose dolphins for marine tasks, such as detecting sea mines and enemy divers.

The blowhole is a nose that has evolved and moved toward the top of the head of the dolphin.

A dolphin's eyes produce "dolphin tears," a secretion that protects their eyes against infection and foreign objects.

Bottlenose dolphins are lacking a sense of smell. They do have a sense of taste, being able to distinguish between sweet, sour, salty, and bitter tastes.

A calf is born tail-first so that it will not drown. The mother causes the umbilical cord to break by swimming quickly away, immediately returning to her calf to take it up to the surface so it can breathe.

## References

https://animalia.bio/common-bottlenose-dolphin