Stenella coeruleoalbastriped dolphin

Geographic Range

Stenella coeruleoalba is found in warm-temperate and tropical seas throughout the world. S. coeruleoalba has been observed in the Mediterranean Sea, eastern and western Pacific Ocean, Atlantic Ocean, Indian Ocean, Caribbean Sea, and in the northern Gulf of Mexico (Baird et. al., 1993; Archer and Perrin, 1999).

Habitat

Striped dolphins occupy both offshore and inshore warm-temperate and tropical waters. S. coeruleoalba appears to avoid sea surface temperatures of less than 20 degrees C (Van Waerebeek et. al., 1998).

Physical Description

Stenella coeruleoalba, otherwise known as striped dolphins, are a fascinating member of the family Delphinidae. S. coeruleoalba ranges in body length from 220cm to 236cm. Like many other delphinids, striped dolphins have a fusiform body, tall dorsal fins, long, narrow flippers, and a prominent beak (Archer and Perrin, 1999). S. coeruleoalba can be identified from other delphinids by their distinctive color and stripe patterns. Striped dolphins are typically bluish-gray in color with a dark dorsal cape and light (usually white) ventral coloration. They are called 'striped' dolphins because of the dark bluish-black stripe running across the entire length of the body, from the eye to the anus, and because they possess black flipper stripes (Archer and Perrin, 1999).

  • Range mass
    135.9.5 to 0.16 kg
    to 0.35 lb
  • Average mass
    0.15 kg
    0.33 lb

Reproduction

The age of sexual maturity is quite variable within sexes. Males reach sexual maturity between the ages of 7 and 15, and females become sexually mature between 5 and 13 years of age. The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean (Archer and Perrin, 1999). The gestation period of striped dolphins lasts 12-13 months. Females typically have a four year calving interval, having a resting period of approximately 2-6 months between lactation and the next mating (Calzada et al., 1996).

  • Breeding interval
    Females typically have a four year calving interval
  • Breeding season
    The mating season of the striped dolphin is in the winter and early summer in the western north Pacific, while it occurs in the fall in the Mediterranean
  • Average number of offspring
    1
  • Average number of offspring
    1.5
    AnAge
  • Range gestation period
    12 to 13 months
  • Range weaning age
    16 (high) months
  • Average weaning age
    16 months
  • Range age at sexual or reproductive maturity (female)
    5 to 13 years
  • Range age at sexual or reproductive maturity (male)
    7 to 15 years

Fetuses grow at an approximate rate of 0.29cm/day. At birth, striped dolphins are 90-100cm long (differing slightly between ranges) and weigh approximately 11.3kg (Calzada, Aguilar, Sorensen, and Lockyer, 1996). Young calves then nurse for almost 16 months. (Archer and Perrin, 1999; Calzada et. al., 1996).

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Behavior

Group size in S. coeruleoalba ranges from a few individuals to over one-thousand individuals, but most schools consist of 100-500 dolphins. Three different kinds of schools often occur: juvenile, breeding adults, and non-breeding adults. Calves do not usually join the juvenile school until one or two years after weaning (Archer and Perrin, 1999). As females reach the transition stage between juvenile and adult, they usually join the non-breeding adults, only a small number go straight to the breeding school. However, as males join an adult group, equal numbers tend to join the breeding and non-breeding schools (Archer and Perrin, 1999).

Striped dolphins are very active, performing aerial maneuvers such as breaching (jumping out of the water), chin slaps, bow-riding (swimming along the wave created by a boat or ship, while often twisting and jumping) and a unique behavior called "roto-tailing," in which "they make high arcing jumps while violently and rapidly performing several rotations with the tail before reentering the water" (Archer and Perrin, 1999).

Like other delphinids, striped dolphins often vocalize with clicks and whistles, which presumably function in communication.

Communication and Perception

Food Habits

S. coeruleoalba seems to have an opportunistic feeding habit. Examining the stomach contents of many striped dolphins, researchers have found S. coeruleoalba to mainly feed on cephalopods, crustaceans, and bony fishes (Wuertz and Marrale, 1993). There is some variation in diet between ranges of S. coeruleoalba. Mediterranean striped dolphins seem to prey primarily on cephalopods (50-100% of stomach contents), while northeastern Atlantic striped dolphins most often prey on fish, frequently cod (Archer and Perrin, 1999). The ranges of observed prey indicate that striped dolphins primarily feed in pelagic or benthopelagic zones of the ocean, often along the continental slope (at the edge of the continental shelf where the ocean floor plunges steeply four to five kilometers) (Archer and Perrin, 1999).

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans

Economic Importance for Humans: Positive

Striped dolphins provide much entertainment to sailors and travelers, as they flip, twist, and breach alongside the waves created by ships and boats. In addition, they are sometimes hunted for meat.

Economic Importance for Humans: Negative

Striped dolphins are in constant competition with humans over prey. The dolphins and fisheries compete over anchovies, tuna, and cod. Fisherman often kill striped dolphins that are caught in their fishing nets. The number of striped dolphins killed in the western Pacific was estimated at 14,000 each year between 1950-1969, but more recently has decreased to between 2,000 and 4,000 per year ( http://www.cetacea.org/striped.htm, 1998).

Conservation Status

S. coeruleoalba is currently listed at Lower Risk in the IUCN - Red List. It is further categorized as being "Conservation Dependent," meaning that the species is in a taxa that is the focus of a conservation program. Without a conservation program, the striped dolphin will qualify for a threatened/endangered status within five years.

Habitat degradation, commercial fisheries, and killing dolphins for their meat all contribute to striped dolphin population declines.

Other Comments

'/Stenella coeruleoalba/' is derived from the Latin "caeruleus" (sky-blue) and "albus" (white).

Some striped dolphins have been held in captivity, but have not been successfully trained.

( http://www.cetacea.org/striped.htm, 1998)

Contributors

Melissa Savage (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

piscivore

an animal that mainly eats fish

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

1998. "Cetecea" (On-line). Accessed November 21, 1999 at http://www.cetacea.org/striped.htm.

Archer, F., W. Perrin. 1999. Stenella coeruleoalba. Mammalian Species, 603: 1-9.

Baird, R., P. Stacey, H. Whitehead. 1993. Status of the Striped Dolphin, Stenella coeruleoalba, in Canada. Canadian Field-Naturalist, 107(4): 455-465.

Calzada, N., A. Aguilar, C. Lockyer, E. Grau. 1997. Patterns of growth and physical maturity in the western Mediterranean striped dolphins Stenella coeruleoalba. Canadian Journal of Zoology, 75(4): 632-637.

Van Waerebeek, K., F. Felix, B. Haase, D. Palacios, D. Mora-Pinto. 1998. Inshore records of the striped dolphin, Stenella coeruleoalba, from the Pacific coast of South America. Report of the International Whaling Commission, 0(48): 525-532.

Wuertz, M., D. Marrale. 1993. Food of striped dolphin, Stenella coeruleoalba, in the Ligurian Sea. Journal of the Marine Biological Association of the United Kingdom, 73(3): 571-578.