Bottlenose Dolphin (Tursiops truncatus)

Bottlenose Dolphins
(Tursiops truncatus)
Photo: NMFS Southwest
Fisheries Science Center

Did You Know?

· Females as old as 45 years have given birth!

· Bottlenose dolphins employ a feeding strategy called "fish whacking," where they strike a fish with their flukes and knock it clear out of the water.

· Bottlenose dolphins are "bow riders" and also sometimes ride in the surf mafde by storms.

Status
MMPA Depleted - Western North Atlantic Coastal stock

Taxonomy
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus: Tursiops
Species: truncatus

Species Description
The bottlenose dolphin is one of the most well known species of marine mammals. They have a robust body and a short, thick beak. Their coloration ranges from light gray to black with lighter coloration on the belly. Inshore and offshore individuals vary in color and size. Inshore animals are smaller and lighter in color, while offshore animals are larger, darker in coloration and have smaller flippers. Bottlenose dolphins can sometimes be confused with the rough-toothed dolphins, Risso's dolphins, and Atlantic spotted dolphins in regions of overlapping distributions.

Bottlenose dolphins range in lengths from 6.0 to 12.5 ft (1.8 to 3.8 m) with males slightly larger than females. The adult weights vary from 300-1400 lbs (136-635 kg). This is a long-lived dolphin species with a lifespan of 40-45 years for males and more than 50 years for females.

Bottlenose dolphins are commonly found in groups of 2 to 15 individuals. Offshore herds sometimes have several hundred individuals. This species is often associated with pilot whales and other cetacean species. They frequently ride the bow wakes of ships and sometimes ride in the surf caused by storms.

Bottlenose dolphins are generalists and feed on a variety of prey items "endemic" to their habitat, foraging individually and cooperatively. Like other dolphins, bottlenose dolphins use high frequency echolocation to locate and capture prey. Coastal animals prey on "benthic" invertebrates and fish, and offshore animals feed on pelagic squid and fish. Bottlenose dolphins employ multiple feeding strategies, including "fish whacking," where they strike a fish with their flukes and knock it out of the water.

Sexual maturity varies by population and ranges from 5-13 years for females and 9-14 years for males. Calves are born after a 12 month gestation period and are weaned at 18 to 20 months. On average, calving occurs every 3 to 6 years. Females as old as 45 years have given birth.

Habitat
Bottlenose dolphins are found in temperate and tropical waters around the world. There are coastal populations that migrate into bays, estuaries and river mouths as well as offshore populations that inhabit pelagic waters along the continental shelf.

Distribution
The bottlenose dolphin has a worldwide distribution ranging from latitudes of 45°N to 45°S.

Population Trends
There are currently 11 stocks of bottlenose dolphins in U.S. waters: California Coastal; California-Oregon-Washington Offshore; Hawaii; Eastern Gulf of Mexico Coastal; Gulf of Mexico Bay, Sound and Estuarine; Gulf of Mexico Continental Shelf and Slope; Gulf of Mexico Outer Continental Shelf; Northern Gulf of Mexico Coastal; Western Gulf of Mexico Coastal; Western North Atlantic Coastal and Western North Atlantic Offshore. NMFS Stock Assessment Reports (SARs) include estimated population sizes for 10 U.S. stocks are summarized below. Current population sizes for the Gulf of Mexico Bay, Sound and Estuarine stock can be viewed from stock assessment links below since there are numerous estimates for small areas in this region. Population trends for all of the U.S. stocks are currently unknown.

Stock	Estimated Abundance	Reference*
California Coastal	323	SAR 2006
California-Oregon-Washington Offshore	5,065	SAR 2007
Hawaii	3,215	SAR 2006
Eastern Gulf of Mexico Coastal	8,963	SAR 2005
Gulf of Mexico Continental Shelf and Slope	25,320	SAR 2007
Northern Gulf of Mexico Oceanic	2,239	SAR 2007
Northern Gulf of Mexico Coastal	4,191	SAR 2007
Western Gulf of Mexico Coastal	3,499	SAR 1997
Western North Atlantic Coastal	17,466	SAR 2007
Western North Atlantic Offshore	81,588	SAR 2007

* NMFS Stock Assessment Reports (SARs) for the Bottlenose Dolphin

Threats
A primary threat to bottlenose dolphins is incidental injury and mortality from fishing gear, such as gillnet, seine, trawl, and longline commercial and recreational operations. Other threats include exposure to pollutants and biotoxins as well as viral outbreaks. Direct harvest of bottlenose dolphins still exists in Japan and Taiwan.

Conservation Efforts
In 2006, NMFS implemented the Bottlenose Dolphin Take Reduction Plan (BDTRP) to reduce the serious injury and mortality of Western North Atlantic coastal bottlenose dolphins incidental to nine U.S. commercial fisheries. In addition to multiple non-regulatory provisions for research and education, the BDTRP requires modifications of fishing practices for small, medium, and large-mesh gillnet fisheries from New York to Florida. The BDTRP also established seasonal closures for certain commercial fisheries in state waters.

Bottlenose dolphins are classified as Data Deficient on the IUCN Red List .

Regulatory Overview
This species is protected under the Marine Mammal Protection Act (MMPA) of 1972, as amended. The Western North Atlantic Coastal stock of bottlenose dolphins is listed as "depleted" under the MMPA. In addition, NMFS has classified five U.S. stocks of bottlenose dolphins as "strategic" stocks: Eastern Gulf of Mexico Coastal; Western Gulf of Mexico Coastal; Northern Gulf of Mexico Coastal; Gulf of Mexico Bay, Sound and Estuarine; and Western North Atlantic Coastal.

Key Documents
(All documents are in PDF format.)

Title	Federal Register	Date
Bottlenose Dolphin Take Reduction Plan (BDTRP)	71 FR 24776	04/26/2006
Depleted Designation for Western North Atlantic Coastal Migratory Stock	58 FR 17789	04/06/1993
Proposed Depleted Designation for Western North Atlantic Coastal Migratory Stock	56 FR 40594	08/15/1991
Advance Notice of Proposed Rule (ANPR) for Depleted Designation for Western North Atlantic Coastal Migratory Stock	54 FR 41654	10/11/1989
Stock Assessment Reports	n/a	various

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