Stenella frontalis
Atlantic spotted dolphin

Stenella frontalis, the Atlantic spotted dolphin, is found in the tropical and temperate waters of the Atlantic Ocean (Wilson and Reeder, 1993).

Along the southeastern and Gulf coasts of the U.S., Stenella frontalis inhabits the continental shelf, usually within 250-350 km of the coast. In the Bahamas, the Atlantic spotted dolphin spends most of its time in the shallow water over sand flats. (Ridgway, 1994; http://whales.ot.com, 1999).

As the common name spotted dolphin suggests, S. frontalis has a spotted color pattern on its body. These spots are not present at birth, and generally do not appear until the onset of weaning. The first spots to appear on the calves are dark spots on the animal's ventral surface. As the dolphin approaches puberty, the ventral spots increase in number and size and pale dorsal spots appear as well. The number of spots continues to increase with age, similar to the development of spotting in Stenella attenuata. There is a large amount of variation in the adult color pattern, between populations and between individuals. At times some individuals become so heavily spotted that they appear white from a distance. Spotting seems to decrease with the distance from the continental shores of North America. In the Azores some specimens have had few or no ventral spots, but well developed dorsal spotting.

The beak of S. frontalis is long and narrow, a typical feature of all Stenella dolphins. S. frontalis has a robust head and body, that make it larger in size, but not length, than S. attenuata. Proportionately larger flippers, flukes and dorsal fins are also characteristic of S. frontalis. The average adult body length of the Atlantic spotted dolphin is 166-229cm. The adult S. frontalis females tend to be slightly larger than the males, and an average adult weight is approximately 200 pounds (90k).

The skull of the Atlantic spotted dolphin varies in size with individuals and with geographical region. Skull size is generally correlated with body size. S. frontalis has small conical teeth, 3-5mm in diameter. In each rostral row there are 32-42 teeth, and 30-40 teeth in each mandibular row. S. frontalis have on average a distally broader rostrum and fewer but larger teeth than S. attenuata. At times differentiating between these two spotted dolphins is difficult, especially in areas where they converge geographically. (Ridgway, 1994; http://wwwa.com/dolphin/index.html, 1999; http://whales.ot.com, 1999).

Dolphins, including S. frontalis, are highly intelligent and social animals. They live in close knit groups called pods, that involve complex social organization with individual recognition and bonding. Pods range in size from a few dolphins to several thousand in offshore regions. Generally pods consist of less than 50 individuals. Atlantic spotted dolphins often school with other species, such as spinner dolphins. The pods of S. frontalis vary in make-up. Segregation by age, sex, and reproductive status has been observed.

The Atlantic spotted dolphin is a vigorous swimmer, quite active at the surface doing forward flips and hurling itself into the air. S. frontalis also has a complex communication system that is made up of narrow-band whistles. These whistles differ enough between individuals that the human ear can distinguish between individual dolphins. The dolphins are able to communicate with each other by whistling, clicking their tongues, cackling and uttering sharp cries. (Ridgway, 1994; http://whales.ot.com, 1999).

The diet of Stenella frontalis varies with location. They eat a variety of invertebrates, as well as small eels and herring. They have even been known to follow trawlers to eat discarded fish. Other feeding habits include feeding at or near the surface and "tracking" schools of small fish. (Ridgway, 1994; http://whales.ot.com, 1999).

The cost and complexity of the tuna fishery has been increased because of regulations that have been designed to lessen the number of dolphins killed by tuna fisherman.

In the past dolphin flesh was considered a delicacy. Besides being used for food, certain parts of its body were used for medicinal purposes. For example, the oil from the liver was used to treat ulcers. Today zoologists are interested in dolphins because they have a high intelligence level. Due to their high intelligence level, dolphins have been trained to help in underwater salvage operations and have even taken part in military exercises. (Stephen, 1973).

Stenella frontalis is listed in Appendix II of the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES). Those listed in Appendix II, as stated on the CITES web site,are "species which although not necessarily threatened with extinction may become so unless trade is subject to strict regulation." As well as non-threatened species that must be subject to regulation in order to control threatened species. (http://www.wcmc.org.uk/CITES/english/index.html).

If a dolphin is in distress it can call out for help. The dolphin puts out an intermittent distress signal that alerts the other dolphins and they hurry to help it. S. frontalis is known to aid other dolphins in its pod that are in distress. If a member of the group is wounded or sick, the others will take turns supporting it in the water until it recovers or dies. (Ridgway, 1994; Stephen, 1973).