Stenella frontalis

Atlantic Spotted Dolphin

Alyssa C. AlbroBiology Department

Frostburg State University

Species Description Lack pelage, “rubbery” skin. Born without spots, typically gain

spots as they age. Individual variation and range

the dolphin lives in has an impact on spotting.

Long rostrum, white coloration around lips and tips of beaks particularly in males.

1.8-2.3m in length, 100-140kg in weight; females typically smaller.

Have 100-200 similar teeth (Nishiwaki, 1966).

Symphyseal mandible, dorsally asymmetric skulls and facial tissue.

Habitat Use & Activity PatternsLittle observed compared to T.

truncatus.Use prey items as direct

teaching tools when females are with their calves. Females spend significantly longer demonstrating hunting and chasing techniques with prey when with a calf than not.

No documentation of “sponging” techniques to protect rostrum (Miles & Herzing, 2003).

Forage for crustaceans along ocean floor, and fish.

Active at all times of day (Dudzinski, 1996).

Do not fit definitions of nocturnal, diurnal, or crepuscular.

Species may be cathemeral (metatumal) – behavior during day has varying intervals during both light and dark portions.

Habitat & DistributionWarm to temperate

waters, typically not far from coasts.

Found from mid-New England down the coast of Brazil (Lopes et al., 2012).

Gulf of Mexico to east coast of Africa, from Morocco to Nambia (Jefferson et al., 1997).

May migrate seasonally, or be year-round residents (Griffin & Griffin, 2004).

Nesting & ReproductionCetaceans do not ‘nest’.No specific indication of birthing regions, nor designated home range.Not extremely territorial, though will defend pod against predators that

stray too close.Sexual behavior not species-exclusive. Individuals in Bahamas have been recorded to produce hybridized

offspring by copulating with T. truncatus (Herzing & Elliser, 2013).Reach sexual maturation as early as eight years, as late as 15 years.

Males and females probably mature at different ages.Calving intervals every three years on average. As little as one, as many

as five.Females who lose a calf in the first year typically conceive again in the

same year (Herzing, 1997).Usually only one calf per birth, twins extremely rare.Gestation 11-12 months.

Social Patterns, Vocalizations, and LongevityHighly intelligent pod animals.Multiple methods of communication, recognition, and

organization.Mother-calf connection exclusive; different behavioral and

communication set between mother and pod, or calf and pod (Miles & Herzing, 2003).

Echolocation in the form of short clicks, sharp squeals, and repetitive clicks.

Playful and acrobatic.Extreme environmental and demographic changes (ex:

hurricanes) are capable of changing social structure within a pod (Elliser & Herzing, 2014).

Exact lifespan of species unknown. Estimated to be around 20 years or as many as 40, as seen in other species.

Ecological RolesFeeding Habits Predators & DangersPrey upon pelagic and

demersal prey items (including, but not limited to: crustaceans, small- to medium-sized fish, and squid) and are predominantly teuthophagous but also ichthyofagous.

Hypercarnivorous, but generally not considered apex predators.

May eat up to 13.5kg of food in one day.

Aggressive shark species including great white, dusky, tiger, bull (Melillo-Sweeting et al., 2014).

Orcas.Humans: harpoon fishermen

targeting the species for meat (as food and bait), naval sonar, accidental bycatch in gill nets, pollution contaminating waters and the dolphins themselves (Leonel et al., 2012).

Ecological Roles (cont.)Cannot be considered keystone predators.There are other species (most of which are

also members of Delphinidae) which can fill the same predatory niche as S. frontalis, or are apex predators themselves.

Removal of S. frontalis, for this reason, would not have a significant impact on other organisms.

Species diversity would suffer slightly.

Economic ImportanceAll species of

dolphin are hunted for their meat, served in Japan and Peru.

Therapy animals.Can be trained to

assist oceanic military operations.

Performance animals.

Conservation StatusEstimated 60,000-82,000 individuals in Gulf of

Mexico and Northwest Atlantic combined.Different populations in both of these locations

have been identified and recorded for the sake of estimating population size.

Not enough data for conservation status to be accurately assessed.

Therefore listed as “data deficient” according to ICUN v3.1.

Not enough data to determine population trends, either.

Health IssuesDolphins Exclusively Threats to HumansSkeletal diseases‘Dolphin Pox’ skin

diseaseParasites

Bolbosoma vasculosum (hookworm)

Anisakis sp. (parasitic nematode)

Phyllobothrium delphini (tapeworm)

SalmonellaHerpesvirusPhocine Distemper VirusLombomycosisOther Morbillivirus

infections

Literature Cited Dudzinski, K.M. 1996. Communication and Behavior in the Atlantic Spotted Dolphins (Stenella frontalis):

Relationships Between Vocal and Behavioral Activities. Office of Graduate Studies of Texas A&M University. Elliser, C.R., & Herzing, D.L. 2014. Social Structure of Atlantic Spotted Dolphins, Stenella frontalis, Following

Environmental Disturbance and Demographic Changes. Marine Mammal Science 30: 329-347. Griffin, R.B. & Griffin, N.J. 2004. Temporal Variation in Atlantic Spotted Dolphin (Stenella frontalis) and

Bottlenose Dolphin (Tursiops truncatus) Densities on the West Florida Continental Shelf. Aquatic Mammals 30: 380-390.

Herzing, D.L. 1997. The Life History of Free-Ranging Atlantic Spotted Dolphins (Stenella frontalis): Age Classes, Color Phases, and Female Reproduction. Marine Mammal Science, 13: 576.

Herzing, D.L. & Elliser, C.R. 2013. Directionality of Sexual Activities During Mixed-Species Encounters Between Atlantic Spotted Dolphins (Stenella frontalis) and Bottlenose Dolphins (Turisops truncatus). International Journal of Comparative Psychology 26: 124-134.

Jefferson, T.A., Curry, B.E., Leatherwood, S., & Powell, J.A. 1997. Dolphins and Porpoises of West Africa: a Review of Records (Cetacea: Delphinidae, Phocoenidae). Mammalia 61: 87-108.

Lopes, X.M., Santos, M.C.O., Silva, E., Bassoi, M., & Santos, R.A. 2012. Feeding Habits of the Atlantic Spotted Dolphin, Stenella frontalis, in Southeastern Brazil. Brazilian Journal of Oceanography 60: 189-198.

Melillo-Sweeting, K., Turnbull, S.D., & Guttridge, T.L. 2014. Evidence of Shark Attacks on Atlantic Spotted Dolphins (Stenella frontalis) off Bimini, The Bahamas. Marine Mammal Science 30: 1158-1164.

Miles, J.A., & Herzing, D.L. 2003. Underwater Analysis of the Behavioral Development of Free-Ranging Atlantic Spotted Dolphin (Stenella frontalis) Calves (Birth to 4 Years of Age). Aquatic Mammals 29: 363-377.

Nishiwaki, M. 1966. A Discussion of Rarities among the Smaller Cetaceans Caught in Japanese Waters. Pp. 192-204 in Norris, K.S. (Ed.) Whales, Dolphins, and Porpoises. University of California Press, Berkeley and Los Angeles, CA.

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