Marine Mammals Archives - Page 2 of 4 - Oceana

Risso’s Dolphin

Risso’s dolphins feed primarily on squid of all sizes (including the humboldt squid) and are therefore excellent divers, spending much of their feeding time at depth, hunting for their preferred prey. Scientists believe that much of the white scarring on the heads of these animals may be a result of aggressive interactions with large-bodied squids. Risso’s dolphins … Read more

Polar Bear

Polar bears are aggressive predators, known for taking a variety of prey. They spend most of the year associated with Arctic sea ice, where they hunt ringed seal and bearded seal pups. Polar bears have an excellent sense of smell and can locate pups even when they are buried in snow dens. Polar bears can easily use their size … Read more

Pantropical Spotted Dolphin

This species feeds on schooling, epipelagic and mesopelagic fishes and squids in the open ocean. Like their prey, pantropical spotted dolphins form large groups – typically composed of hundreds or even thousands of individuals – for hunting and socializing. They reach sexual maturity at approximately 10 to 12 years of age and live for at least 40 years. … Read more

Long-finned Pilot Whale

Long-finned pilot whales are active predators that eat mostly squid, including relatively large-bodied species. They will also eat bony fishes when they are common. In some areas, the long-finned pilot whale can be observed forming mixed species groups with sperm whales (another toothed whale that feeds preferentially on squid) and also with smaller dolphins. Like all mammals, long-finned … Read more

Humpback Whale

Interestingly, though they are enormous, humpback whales are not predatory. They filter feed for tiny krill or small pelagic fishes and are totally harmless to people (other than through accidental collisions). This life history strategy is common among several large animals in the ocean, including the whale shark, the basking shark, and the other great whales. Like all … Read more

Harp Seal

Harp seals are foraging predators that eat several dozen species of bony fishes and invertebrates. They will eat just about anything they can catch. Juveniles eat krill and other pelagic crustaceans, and the diet diversifies as they grow. Adult harp seals are eaten by killer whales and large sharks. Juveniles are eaten by polar bears and other terrestrial predators, including foxes … Read more


The dugong, like all sea cows, is herbivorous. It primarily grazes on sea grasses and therefore spends most of its time in sea grass beds. Unlike the closely related manatees, the dugong never enters freshwater and is therefore the only exclusively marine mammal that is herbivorous. As in most herbivores, the dugong’s brain is very small compared to … Read more

Beluga Whale

Belugas, however, are typically more solidly white than their grayish cousins. Adult belugas are also slightly larger than narwhals, reaching lengths of around 18 feet (5.5 m). Interestingly, the beluga whale is the only species of cetacean (whales and dolphins) that has a movable neck. Belugas can move their heads up and down and from side to side. … Read more


Reproductive output, however, is quite low – with females giving birth to only one calf, every other year – and the gestation period is 11 months, longer than most land mammals, including humans. Lifespan is also low, with individuals likely living no longer than approximately 25 years. Vaquitas are predatory and eat a variety of Gulf of … Read more

Southern Elephant Seal

The southern elephant seal is one of two living species of elephant seals. These two species get their name from the trunk-like nose that males develop as they become sexually mature. Only the strongest, most dominant males win the right to mate with females, and ninety percent of males die before developing a harem. Harems defended by the … Read more