What is a marine mammal? A complete guide

Marine fissipeds are the final group of marine mammals, consisting of polar bears and sea otters. Members of the order Carnivora, these animals are much more closely related to terrestrial carnivores than seals or whales. However, they are still considered marine mammals because they spend significant amounts of time in the water, especially to hunt.

Threats to marine mammals

Various threats affect marine mammals, most of which are directly or indirectly caused by human activity. These animals are very susceptible to being caught in fishing gear, which usually leads to death or horrific injuries. They can also become entangled or ingest plastic waste floating in the ocean and are sometimes killed for meat, blubber, skin, or tusks. Pollution and other human activities damage marine habitats, while ships cause vessel strikes and underwater noise pollution. Here are some of the biggest threats faced by marine mammals today.

Bycatch

Many marine mammals, including seals, porpoises, and dolphins, become victims of bycatch-meaning they are unintentionally caught in fishing nets and gear alongside target species of fisheries.

Climate change

Marine mammals are particularly vulnerable to the effects of climate change. Rising ocean temperatures are a major concern for these animals, from the Arctic species to those found in temperate waters, and the resulting changes in prey distribution are already impacting the health and migratory patterns of marine mammals around the world.

Commercial hunting

Some marine mammals are hunted for their meat and other parts. Commercial hunting is unsustainable and inhumane and poses a major threat to the survival of some species. While there is a global ban on commercial whaling, currently Norway, Japan, and Iceland still permit it.

Entanglement

Marine mammals easily become entangled in active fishing ropes or nets, and without arms and hands, it's nearly impossible for them to free themselves. Experts estimate that hundreds of thousands of whales die every year due to entanglement, which is a serious welfare issue and can have conservation impacts too. Entangled animals often drown, as they cannot reach the surface to breathe, and it also leads to cuts and infection as heavy ropes bite through skin, and to starvation as animals towing heavy fishing gear cannot feed effectively.

Marine debris and ghost gear

Discarded commercial fishing material poses a huge problem for marine mammals. The fishing rope and nets discarded into the ocean in just one year could circle the Earth more than 18 times. Marine mammals can get stuck in this discarded fishing gear, which can cause injuries and fatalities.

Noise pollution

Noise pollution is especially threatening to cetaceans. Because they use sound to locate food and friends, human-made ocean noise can make echolocation impossible, resulting in lost, hungry animals.

Since the 1950s, underwater noise from shipping has doubled every decade, severely impeding whales' only communication channel. Thankfully, this is a far easier problem to solve than other forms of pollution. Slower ship speeds are a simple solution to make the ocean quieter.

Vessel strikes

Vessel strikes, or collisions with boats and ships, are a big threat to whales, especially to small, endangered populations. They usually occur when shipping lanes and high densities of shipping traffic overlap with critical whale habitats.

Water pollution

Water pollution from agricultural runoff, sewage and chemical spills, and more can be highly toxic to marine mammals. Municipal wastewater discharges, ocean spills, runoff, and deposits from air contaminants, as well as discharges from fishing, shipping, oil- and gas- related commercial activities, can accumulate in marine mammals' blubber and tissues over time, affecting their health and reproductive success.

Plastic waste also threatens some marine mammals, as they can accidentally ingest or get tangled in it, causing injuries and infections that can be fatal.

Our work

IFAW is dedicated to protecting marine mammals through conservation, animal rescue, and policy initiatives. Learn more about our marine conservation work that happens around the globe or check out our Marine Mammal Rescue team. Recently, we opened the first-of-its-kind Dolphin Rescue Center on Cape Cod, Massachusetts, to boost stranded dolphins' survival rates. We also advocate for various policy initiatives to protect marine mammals and other animals around the world.

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