Bottlenose Dolphin

Bottlenose Dolphin

Tim Hauf, timhaufphotography.com

Scientific Name
Tursiops Truncatus

Introduction
Bottlenose dolphins are one of the most recognizable and well-known species of the cetacean family. Based upon historical references and their depiction in works of art going back to ancient civilizations, as well as today’s performers in entertainment venues in marine parks, such as Sea World, they are easily identifiable. Being primarily coastal inhabitants, the bottlenose is conspicuous to the public without the need to leave land to view them. In the Ventura area it is not unusual to spot forays by the bottlenose into Ventura Harbor, the site of the park’s administrative center. This species is also seen along the entire Southern California Bight by countless beach goers.

Quick and Cool Facts

• There appear to be two main varieties; a smaller, inshore form and a larger, more robust form that lives mainly offshore. ⁴
• A social species, the bottlenose dolphin may live in groups of 100s of individuals. ⁴
• They employ a feeding strategy called "fish whacking," where they strike a fish with their flukes and knock it clear out of the water. ⁵
• Dolphins can rest one side of their brain at a time, allowing them to sleep whilst remaining conscious enough to surface and breathe. ⁴
• Bottlenose dolphins are born with a few hairs on their "rostrum" or beak that they lose shortly after birth. ⁵
• The bottlenose has more flexibility in its neck than other oceanic dolphin owing to the fact that 5 of its 7 neck vertebrate are not fused together. ⁸
• This species can live as long as 60 years. ⁹

Appearance
As described by the FAO Species Identification Guide: Marine Mammals of the World, “The bottlenose dolphin is probably the most familiar of the small cetaceans because of its coastal habits, prevalence in captivity worldwide, and frequent appearance on television and in advertising. It is a large, relatively robust dolphin, with a short to moderate length stocky snout that is distinctly set off from the melon by a crease. The dorsal fin is tall and falcate, and set near the middle of the back. Color varies from light grey to nearly black on the back and sides, fading to white (sometimes with a pinkish hue) on the belly. The belly and lower sides are sometimes spotted. There is a dark stripe from eye to flipper, and a faint dorsal cape on the back (and sometimes an indistinct spinal sides are sometimes spotted. blaze), generally only visible at close range. Often, there are brushings of grey on the body, especially on the face, and from the apex of the melon to the blowhole. Bottlenose dolphins have 18 to 26 pairs of robust teeth in each jaw. In older animals, many of these may be worn down or missing.

Adults range from about 5.5 to 13 feet in length with males somewhat larger than females. There is incredible variation between different populations. Maximum weight is at least 1400 pounds, although most animals are much smaller. At birth, the bottlenose is about 3 to 4 feet in length.”

Range
Bottlenose dolphins are cosmopolitan in distribution, occurring in most coastal areas in temperate and tropical regions of the world.

Habitat
According to NOAA, Fisheries Office of Protected Resources, the bottlenose dolphin is found in temperate and tropical waters around the world. They 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. ⁵

Feeding
In a comprehensive study of the bottlenose dolphins feeding habits published by Stephen Leatherwood in 1975, it was concluded that the species was both an “opportunistic and catholic feeder”. Additionally he comments, “The observations for coasts of mainland Mexico, Baja California, and southern California similarly involve feeding on varied prey and under varied circumstances. The recurrence of patterns over time at widely divergent locations suggests their adaptive value for the species.”

Feeding strategies in collecting food have shown cooperative efforts of pods in herding or driving fish into shallower water on shorelines, bays or inlets to facilitate easier acquisition of prey. In the Southern California Bight, species utilized as food cover a broad spectrum. Sardines, northern anchovies, squid, shrimp and larger schooling species such fall within the bottlenoses diet. ¹⁰

Reproduction
Based upon studies by Jefferson, et al., 2008; Reynolds, III and Wells, 2003; Reynolds, III, et al., 2000 as found in Animal Diversity Web, the age of the bottlenose dolphins at sexual maturity varies geographically. Typically Female dolphins typically reach sexual maturity between 5 and 10 years of age, while males reach sexual maturity between 8 and 13 years old. Sexual maturity is usually achieved years before reproduction; males that reach sexual maturity at age 10 don’t typically breed until they are at approximately 20 years old. Reproductive seasons vary from region to region. Typically, females ovulate at a particular time of year while males are active throughout the year (but with a peak of testosterone production when females ovulate). Gestation lasts about 12 months and each pregnancy produces one calf. Females nurse their young from nipples on each side of their genital slit until the calf is between 18 and 20 months. Bottlenose dolphins reproduce every 3 to 6 years, with females usually becoming pregnant soon after their calf is weaned. Calves can be born at any time of the year but with a peak in birthing during warmer months. Females can reproduce well into their late forties.

Conservation Status
Based upon a 2008 assessment, the International Union for Conservation of Nature and Natural Resources, (IUCN), states that although there are many threats operating on local populations, the species is widespread and abundant, and none of these threats is believed to be resulting in a major global population decline. It therefore states that the species is of least concern. ¹¹

References and Additional Information

1. FAO Species Identification Guides: Marine Mammals of the World
2. Channel Islands National Marine Sanctuary
3. The Society for Marine Mammalogy
4. arkive.org
5. NOAA Fisheries Office of Protected Resources
6. International Union for Conservation of Nature and Natural Resources, (IUCN),
7. Marine Mammals Commission
8. American Cetacean Society
9. Marine Mammal Science
10. Marine Fisheries Review, Vol. 37, No.9, September 1975, Leatherwood
11. The IUCN List of Threatened Species