Ribbon seal

The ribbon seal has a short snout with broad, deep internal nares and large, rounded, front-facing orbits.^[6] Like other phocids, it possesses enlarged auditory bullae and lacks a sagittal crest.^[6] The ribbon seal has curved, widely spaced dentition and smaller canines than other phocid species.^[6]

The ribbon seal has a large inflatable air sac that is connected to the trachea and extends on the right side over the ribs. It is larger in males than in females, and it is thought that it is used to produce underwater vocalizations, perhaps for attracting a mate.^{[citation needed]} Unlike other pinnipeds, the ribbon seal lacks the lobes that divide the lungs into smaller compartments.^[7] The ribbon seal can grow to a length of about 1.6 m (5.2 ft) and a weight of 95 kg (209 lb), with males being larger than females.

The main predators of ribbon seals include great white sharks and orcas.^[8]

Sexual dimorphism[edit]

Male ribbon seals are typically larger than females. This is particularly recognizable in their skull morphology because male nares openings are much larger than female nares openings.^[6] Larger males are hypothesized to have a better chance of reproducing with multiple females. They have a higher fitness level and win in competition with other males over females.^[9]

Habitat[edit]

The ribbon seal lives in the Arctic parts of the Pacific Ocean. During winter and spring, it hauls out on pack ice to breed, molt, and give birth. During this time, it is found at the ice front in the Bering and Okhotsk Seas.^[10] During the winter and spring, the ribbon seal lives in open water, though some move south as the ice recedes with warmer temperatures. Little is known about its habit during this time, as it is so far from land and human observation. The ribbon seal almost always comes to land.

Thus far, there have been three acknowledged instances where ribbon seals have been found as far south as Squamish, British Columbia, Long Beach, Washington, and even further south at Morro Bay, California. There was nothing to suggest that illness was the cause of the seals appearance, as they appeared to be healthy.^[11][12]

Behavior[edit]

Ribbon seals are rarely seen out on the ice and snow. Their method of movement on the ice is highly specialized. While quickly undulating their body in serpentine motion, they grip into the ice with their claws and use alternating flipper strokes to pull themselves across the ice's surface. It has been observed that this form of locomotion is rendered ineffective on other surfaces, most likely due to the increased friction between the animal's fur and the substrate.^[5]

While out on the ice, ribbon seals are noticeably indifferent to their surroundings. Humans in boats have been able to closely approach these seals before disturbing them. Mothers have been observed leaving pups by themselves for extended lengths of time. This would suggest that they experience little predation from land predators such as bears or humans, relative to other seals. When these seals are captured in nets, they are known to engage in feigning death behavior.^[5]