The Atlantic white-sided dolphin is a mid – large-sized dolphin that can be found traveling in the North Atlantic ocean. Given its name, because of its white belly and sides, the Atlantic white-sided dolphin has a visual appeal that stands out when compared to other dolphin species.
These dolphins are playful species that enjoy traveling together in large groups containing several dozen or more dolphins. Compared to other dolphin species, the Atlantic white-sided dolphin appears to be slightly larger in nature than average.
Physical Characteristics and Appearance
When fully grown, the Atlantic white-sided dolphin can reach lengths of 8 – 9 1/2 ft. long and weigh between 425 – 525 lbs. on average, with the female dolphins growing smaller and lighter than their male counterparts. The body itself is often described as robust in nature, and the beak is relatively short compared to other dolphin species.
They have a long pointed dorsal fin that curves towards the flukes located in the middle of their back, and the flippers are small, pointed, and sickle-shaped. The flukes are also short but wide to help these dolphins propel themselves through the water.
As the name suggests, these dolphins have a white under-body that rises along their sides and around their eyes; however, the eyes are a dark gray to black color. They also have an additional white/pale yellow patch along the sides of the dorsal fin, hence the name white-sided. The back is primarily dark gray or black with a yellow patch, and a portion of the beak is also a dark gray to black coloring.
Diet and Hunting Methods
These dolphins consume various fish, shrimp, and squid as part of their primary diet. Some of the most commonly hunted fish include hake, herring, and mackerel. To assist with catching their prey, these marine mammals have 30 – 40 pairs of teeth that can be used to grab their food to prevent it from escaping.
When searching for prey, these dolphins have been observed holding their breath for up to 5 minutes during long dives. Echolocation can also locate prey, coordinate hunting attacks, and navigate the ocean. Given their strong social nature, these dolphins may hunt together when searching for prey.
During feeding periods, the Atlantic white-sided dolphin may be observed inhibiting their local habitat with other cetaceans such as the fin whale, humpback whale, and long-finned pilot whale.
Habitat and Migration
As the name suggests, these dolphins can be found primarily in the north Atlantic ocean in temperate to subarctic waters that range between 5 – 20 degrees Celsius. Their range can extend from 35°-80° N of the equator and extend from North Carolina to Greenland.
Large groups of Atlantic white-sided dolphins have been spotted in Cape Cod, Greenland, the North Sea, and the United Kingdom. They can also be spotted swimming in parts of the eastern United States, such as North Carolina, as we mentioned before. In fact, large-scale stranding has been known to occur in Northeastern U.S. territories. However, the cause of these strandings is unknown.
In terms of habitat depth, they tend to prefer living in waters that are at least 130 ft. deep (40m.) and can often be spotted in waters several times that depth. As a species, the Atlantic white-sided dolphin is often found in offshore waters around the Continental shelf, making it hard to spot from the local shoreline.
Social Structure and Communication
These dolphins have been spotted traveling in pods of up to 60 dolphins in certain locations. They have also been observed traveling in small groups of less than a dozen and pods of up to 500 dolphins.
Atlantic white-sided dolphins are often described as highly social animals that enjoy interacting and playing with one another. They may often be seen leaping out of the water or breaching the surface. As stated earlier, these dolphins may be seen associating with other cetacean species such as the fin whale, humpback whale, and long-finned pilot whale.
Mating, Reproduction and Lifespan
The average gestation period for these dolphins is 10 – 11 months. After birth, young dolphins may be nursed for up to 18 months or until they can survive independently. Sexual maturity for the Atlantic white-sided dolphin occurs between the ages of 6 – 12. Once sexually mature, these dolphins may mate and produce their own offspring. The average lifespan of these dolphins is estimated to be between 20 – 30 years.
Threats and Predators
The Atlantic white-sided dolphin faces several threats such as being captured by poachers that want to sell their meat, getting caught in fishing/gill nets which can cause these marine mammals to drown, and potentially life-threatening hazards due to water pollution. Here are some of the potential threats the Atlantic white-sided dolphin may face:
- Hunting/poaching
- Bycatch
- Pollution
- Habitat degradation
- Predators – Killer whales and sharks
While hunting/poaching has been known to exist among the Atlantic white-sided dolphin species (especially in the past), there are no recent studies/assessments done on this topic regarding potential hunting trends and the effect this may have on Atlantic white-sided dolphins.
Bycatch affects some white-sided dolphins as fisheries cast nets and other fishing equipment, which these dolphins may end up entangled in. Once caught in a fishing net, these marine mammals become unable to surface for oxygen, leading to drowning. However, given their offshore nature, these dolphins are less likely to face threats from bycatch than other small dolphin species.
As with all marine mammals, chemical pollution and waste from metals and plastics can also affect dolphin populations. Pollution may either harm these dolphins directly or affect their ability to reproduce offspring. The effects of pollution on this species aren’t well understood.
Lastly, habitat degradation can affect specific populations where commercialization may occur, such as travel routes for passing boats/ships and offshore construction. Aside from human-related threats, Atlantic white-sided dolphins may occasionally be attacked by some of the most common predators to the dolphin species, including killer whales and large carnivorous sharks.