Bottlenose Dolphin

Lore & Background

Until 1998, all bottlenose dolphins were considered one species T. truncatus. That year, the Indo-Pacific bottlenose dolphin (T. aduncus) was recognized as a separate species. The two species are thought to have split during the mid-Pleistocene, about 1 million years ago. Currently, four common bottlenose dolphin subspecies are recognized: T. t. truncatus, T. t. ponticus (the Black Sea bottlenose dolphin), T. t. gephyreus (Lahille's bottlenose dolphin), and T. t. nuuanu (the Eastern Tropical Pacific bottlenose dolphin). A 2020 study identified four distinct lineages within T. truncatus, each of which could be a distinct subspecies: a lineage native to the coastal regions of the western North Atlantic, an offshore lineage found worldwide in pelagic ecosystems, a lineage native to the Mediterranean, and a lineage restricted to the Black Sea. The coastal dolphins of the western North Atlantic are now recognized as Tamanend's bottlenose dolphin (T. erebennus).

In Their Own Story

As a very social species, the common bottlenose dolphin lives in groups called pods that typically number about 15 individuals, but group size varies from pairs of dolphins to over 100 or even occasionally over 1,000 animals for short periods of time. Group structure depends on the sex and age of the dolphins. Types of groups include nursery groups, juvenile groups, and groups of adult males. Male dolphins tend to form pair bonds, which are the strongest of dolphin bonds, while females stay with their calves for 3-8 years and then tend to stay in social groups. Typically, common bottlenose dolphins are more social after they have eaten in the mid-day or evening. During these times, they are often seen engaging in group interactions, including play, vocalizations, and cooperative swimming behaviors.

Reader's Guide

Common bottlenose dolphins use echolocation to navigate and hunt, emitting sound waves that are bounced back and received as nerve impulses in the brain which can be interpreted at a frequency of 120 kHz. This allows them to know the location, shape and size of objects. Their diet consists mainly of eels, squid, shrimp and a wide variety of fishes. They do not chew their food, instead swallowing it whole. Dolphin pods often work as a team to harvest schools of fish, though they also hunt individually. Along the U.S. Atlantic coast, the main prey includes Atlantic croakers, spot, and American silver perch, while in South Africa, African maasbankers, olive grunters, and pandora are typical prey. Dolphins eat 10–20% of their body weight each day, with pregnant and nursing females eating the most. Mating behavior is polygamous, and after a year-long gestation period, females bear a single calf. Newborn calves are between 0.8 and 1.4 m long and weigh between 15 and 30 kg. The calf's suckling lasts between 18 and 20 months and they are weaned between three and eight years of age.

Did You Know?

• Five of the common bottlenose dolphin's seven neck vertebrae are not fused together, giving them more flexible necks than other dolphins.
• Dolphins can emit and receive sound waves at a frequency of 120 kHz for echolocation.
• Mother dolphins change their signature whistle when their calf is present, reaching a higher frequency or using a wider frequency range, similar to human child-directed speech.
• Male dolphins form pair bonds, which are the strongest of dolphin bonds.
• Newborn calves are between 0.8 and 1.4 m long and weigh between 15 and 30 kg.