The Life Cycle of Bottlenose Dolphins

By Kevin Lee
Sharks are a predatory threat to bottlenose dolphins.

Like coffee cup kittens, musical hamsters and cute bouncing babies, bottlenose dolphins, with their permanently etched "smiles" and playful antics, bring laughter and warmth to people around the world. Some of these seafaring mammals live in captivity, while others roam coastal areas or venture further offshore. Bottlenose dolphins, also known by names such as cowfish and black porpoise, live fulfilling lives in an intriguing cycle that begins at birth.

Pregnancy and Birth

After a female bottlenose dolphin becomes pregnant, it has a gestation period of about 12 months. Although female bottlenose dolphins give birth to calves throughout the year worldwide, births peak at various times in different locations. Along Texas's coast, for instance, more baby bottlenose dolphins are born in March, while more calves arrive in the fall along the Southern California coast.

According to SeaWorld, calves nurse up to four times every hour during their first four to eight days of life. You can identify calves because they are darker in color than adults and have vertical lines on their sides that eventually disappear.

Mothers carefully orchestrate a calf's movements through the water by ensuring that it swims in the mother's slipstream -- a wake that forms as the parent dolphin swims. Because a calf moves along in this slipstream, mother and child can keep up with the other dolphins in their group. Eventually, the calf grows up to become an adult.

Adult Bottlenose Dolphin Feeding

Bottlenose dolphins may look cute and cuddly, but like sharks they are carnivorous predators that capture and eat prey. A dolphin's meal can include aquatic creatures such as squid, fish and crustaceans; their exact diets vary according to where they live.

So smart that they've been taught to read, bottlenose dolphins are incredibly social animals. Adults, working in a team with other dolphins, often use multiple hunting techniques to catch prey. For instance, a group might surround a school of fish and herd it into a small mass or sand bar. The dolphins can then swim through the mass and easily grab fish as needed. Bottlenose dolphins also learn to adapt to human activity and eat fish that fishermen have netted or discarded.

Male Bonding: Surprisingly Complex Social Interactions

Second only to the bond between a calf and its mother, relationships between one or two male bottlenose dolphins begin in their late teens. These alliances form bonds with other groups of males resulting in complex relationships among the male dolphins. Dolphin alliances work together to gain access to female bottlenose dolphins and prevent other males from interacting with individual females.

Fights between alliances or members within them can occur, resulting in the most dolphin aggression humans may witness. Males in these alliances might also attack females who attempt to escape from the males. Male bottlenose dolphins aren't that interested in females that have nursing calves except during weaning time. This means that females, who calve at around 11 or 12 years old, don't experience much male aggression while raising young ones.

Playing the Aquatic Mating Game

Male bottlenose dolphins reach sexual maturity between 10 and 12 years old, while females become sexually mature between 5 and 7 years. Male courtship activity includes posing for females and clinging to them. A male bottlenose dolphin may also rub, nuzzle, stroke and mouth a female during seduction.

After giving birth, a female bottlenose dolphin might swim back to its own mother to raise its young calves. This activity is not unlike some human mothers who return home and create multigenerational groups.

Bottlenose Dolphin Life Styles: Behind the Scenes

Carefree and playful, bottlenose dolphins appear to have fun with life. If you could follow them, you'd discover that they spend quite a bit of time traveling, interacting socially with other dolphins, foraging and resting. With a home range of about 40 kilometers (87 miles), the distance they travel during the day varies. Bottlenose dolphins also body surf on waves near the shore and ride waves created by moving vessels.

Young and old bottlenose dolphins also carry objects, chase each other and toss seaweed between them. These activities may give the dolphins valuable practice in catching food.

All Good Things Must One Day End

A variety of conditions can cause health problems and premature deaths in bottlenose dolphins. Like humans, they get skin diseases, stomach ulcers and even heart diseases. Tapeworms and other parasites have detrimental effects as well.

Dolphins that survive illness, parasites, accidents and predators eventually die of old age. When these animals get older, new layers of dental material appear. Marine biologists can use these layers to estimate a dolphin's age.

Based on data gathered off the Sarasota, Florida coast, SeaWorld estimates a bottlenose dolphin's lifespan at 20 years or less. Dolphins can, however, live to be 40 or 50, with some females exceeding 60. This extreme age is rare and less than 2 percent of these aquatic mammals live that long. Studies show that captive bottlenose dolphins living in Alliance of Marine Aquariums survive longer than those in the wild.

About the Author

After majoring in physics, Kevin Lee began writing professionally in 1989 when, as a software developer, he also created technical articles for the Johnson Space Center. Today this urban Texas cowboy continues to crank out high-quality software as well as non-technical articles covering a multitude of diverse topics ranging from gaming to current affairs.