Estimated population:
The exact worldwide population of
the bottlenose dolphin is not known. In the eastern tropical Pacific
the population is estimated to be 243,500, while in the waters of Japan
the population estimates are as low as 37,000.
Ways to identify this species:
Bottlenose
dolphins are gray with a soft color pattern, have a robust body with a
short to medium-length beak, and a large curved dorsal fin. This
species usually travels in groups of 10-25 and are often seen very
close to shore. They can travel in groups of hundreds when off-shore.
Biology
- Dolphins are considered to be some of the most intelligent species on Earth.
- Bottlenose dolphins measure from 8-12 feet and typically weigh between 400 and 600 pounds.
- This
species feeds on a variety of organisms depending on habitat location.
They eat invertebrates, pelagic and mesopelagic fish, and are often
attracted to trawlers where they feed on escaped fish.
- They
use echolocation-bouncing sound off objects to determine their
location-to hunt and use a series of high-pitched clicks to stun prey.
- Dolphins have strong eye muscles that can change the shape of the eye lens in order to focus in both air and water.
- Females usually give birth every 3 years, with gestation lasting a year.
- The average life span of a male dolphin is between 40 and 45 years, while females tend to at least 5 years longer.
- Bottlenose
dolphins like to surf in breakers and waves from whales or storms, and
are well-known for riding the bow waves of powered vessels.
- Bottlenose
dolphins often associate with other cetacean species such as pilot
whales; however, they may become aggressive if other species try to
occupy their bow-riding territory.
Threats
- This species has two major natural predators; killer whales and sharks.
- Climate
change has affected certain populations of this species. The California
coastal population has been pushed northward due to rising water
temperatures associated with El NiƱo events.
- Bottlenose dolphins often get caught in fishing nets and are adversely affected by pollution and near shore habitat destruction.
- Bycatch
in tuna nets has been a significant contribution to dolphin mortality.
In 1990, a program to label tuna cans "Dolphin safe or Dolphin
friendly" drastically reduced the number of tuna-related deaths.
Standards have since been weakened and dolphins remain at risk.