|Atlantic Spotted Dolphin, Stenella frontalis Common Names:
General Description The Atlantic Spotted Dolphin is relatively small in comparison to others of the dolphin family (Delphinidae). As the name suggests the Atlantic Spotted Dolphin gains spots as it ages, young completely lack spots while adults have dorsally grayish-white spots and ventrally darker spots. The spots do not occur on their head. Females (80-90kg) are slightly larger than males (70-85kg). Head-body length is anywhere from 2-2.3 meters. The Atlantic Spotted Dolphin closely resembles the Atlantic Bottlenosed dolphin, however, Spotted Dolphins tend to be stockier. They are frequently seen jumping clear of the water, and riding the bow wave of moving vessels. The Atlantic spotted dolphin is well known for its tolerance of human swimmers. The opportunity to swim with and observe their behavior has provided valuable information on the complexity of the social lives of delphinids. These Dolphins are sleek and aerodynamic, with tight skin, which feels rubbery to the touch.
Geographical Distribution and Habitat Requirements: The Atlantic Spotted Dolphins is found in both temperate and tropical waters, from the Atlantic Coast of North America, the Gulf of Mexico, and the Bahamas. They are also found along the African and European coasts. The Atlantic Spotted Dolphin is not a full time resident of New Brunswick’s water. Atlantic Spotted Dolphins are normally a pelagic species and rarely come within 20 km of shore. However, when they do come in close to shore they are able to attain the shallowest bottom depths of almost any dolphin species, including the Bottlenose. On average the Atlantic Spotted Dolphin occurs on the continental shelf or along the shelf break at oceanic depths of about 185m or deeper.
The Atlantic Spotted Dolphin lives in close-knit social groups called pods, with some pods of up to several hundred individuals or smaller groups that could include ten to fifty animals. All Dolphins have a complex communication system, made up various clicks and whistles. Atlantic Spotted Dolphins are able to hunt in a coordinated group in which they round up their prey, usually anchovies, herring or other surface dwelling fish, into a tightly packed ball. The dolphins then proceed to slam into this ball of prey stunning the fish so that they can feed at their leisure. Atlantic Spotted Dolphins are also known to prey upon squid and other small cephalopods and other benthic invertebrates. Atlantic Spotted Dolphins have a home range of 400 or more kilometers, and can travel an average of 72km a day. When diving these dolphins tend to only remain below the surface for short periods of time, usually two minutes, and go to depths of less than 30m. There is a correlation between the age of an Atlantic Spotted Dolphin and the amount of spots it has. When a dolphin is born (calf) it is a two tone, gray-white without spots. This phase can last from 2-6 years. An Atlantic Spotted Dolphin becomes a juvenile when they pass into the speckled phase. This is when they develop black spots on the ventral surface and few light gray spots on the dorsal surface. This phase lasts for about 4-7 years. The next phase is the mottled this is when dolphins become young adults. It’s characterized when they develop extensive and merging gray and white spots on the dorsal surface and continuation of black spots on the ventral surface. This phase can last from 4-10 years. The last phase is the fused phase in which Atlantic Spotted Dolphins are considered adults. This is when fused black and white spots become extensive and coalesced on the ventral and dorsal surface. Females become sexually mature between 9-11 years of age and have a gestation rate of 11 months. Only one calf is normally produced which stays with the female for 1-5 years.
The primary impact on Atlantic Spotted Dolphins is from tourism and dolphin swim or watching programs. While there is documentation of humans and spotted dolphins swimming amongst one another, the effects caused by humans have not been examined. However, some dolphins have been killed in tuna purse seines. A mass mortality of Atlantic Spotted Dolphins in Mauritania led the government to ban the use of purse seines throughout the country. There is insufficient knowledge to be given a status by the IUCN although it is felt that there is a relatively large population with no threat of extinction.