What's the difference between a seal and a sea lion?

• Seals and sea lions can be differentiated by physical traits and behavior differences
  Sea lions have visible ear flaps and large rotating flippers. Seals don't have visible ears, move by scooting on their belly, and usually move less on shore.
  
• Pinnipeds play a critical role in ocean ecosystems
  Seals and sea lions are predators that help keep fish and squid populations in check. They are also prey for apex predators like orcas, sharks, and polar bears.
  
• Many pinniped species are increasingly under threat from human activity and climate change.
  Overfishing, entanglement in fishing gear, habitat loss, pollution, disease, and shrinking sea ice are putting several seal and sea lion species at risk.

Rule of thumb: if it’s barking, walking, and staring at you, it’s probably a sea lion. If it’s quietly resting on the beach, it’s probably a seal.

Sea lions and fur seals are both considered “eared seals” and belong to a biological family known as “Otariidae.” Aptly named, they can be distinguished from their true seal counterparts by their small ear flaps and are often larger than true seals. Sea lions can also maneuver on land much easier than seals, due to their rotatable back flippers. Last but not least, sea lions are loud! They bark, roar, and growl.

So what’s the difference between a sea lion and a fur seal? One of the biggest tells is their fur. Fur seals have much thicker fur, consisting of a dense and luscious undercoat covered by longer hairs on top.  Sea lions, in contrast, have a much less prominent undercoat. Sea lions also tend to be larger and have a wider, dog-like or bear-like face shape, while fur seals have longer, pointier snouts.

There are six species of sea lion: Steller’s (or Northern) sea lion, the California sea lion, the Galápagos sea lion, the Australian sea lion, the South American sea lion, and the New Zealand sea lion. These species are generally found in coastal areas of the Pacific Ocean.

There are 9 species of fur seal: the Northern fur seal, the Antarctic fur seal, the Subantarctic fur seal, the South American fur seal, the New Zealand fur seal, the Guadalupe fur seal, the Juan Fernández fur seal, the Galápagos fur seal, and the Brown fur seal (sometimes split into Cape fur seal and Australian fur seal). Only one of these species is found in the Northern hemisphere, while all others are found South of the equator.

Many pinniped populations are under threat, including the Hawaiian and Mediterranean monk seals, the northern fur seal, and the Australian, Galapagos, and New Zealand sea lions. The pressures seals and sea lions are facing are only increasing.

In the past, many pinnipeds were targeted by hunters for their fur, leading to the extinction of some species, such as the Japanese sea lion and the Caribbean monk seal. While hunting is more restricted today, pinnipeds now face a host of other anthropogenic threats. One of the greatest is climate change, which especially affects species that rely on sea ice. Less sea ice means fewer places to rest, breed, and escape predators, putting these animals at risk.

Entanglement in fishing gear is another hazard for seals and sea lions, often leading to injury and sometimes drowning. Overfishing is also a major issue: As commercial fisheries deplete ocean fish stocks, pinnipeds have less prey available, threatening their survival. Compounded by habitat loss from coastal development and pollution from plastics and other chemicals, pinnipeds are facing a perfect storm.

Lastly, small, threatened populations are especially vulnerable to disease, which has been a serious problem for endangered Mediterranean monk seals and New Zealand sea lions.