I'll bet that a lot of you folks think that elephant seals have the weirdest noses of all pinnipeds.
You are wrong.
The Hooded Seal (Cystophora cristata) is so called because adult male Hooded Seals possess a skin bladder that hangs down from their forehead between their eyes when it's deflated. This bladder is called a "hood." When engaging in aggressive displays toward other males or showing off for females, these males can inflate this membrane by closing one of their nostrils and forcing air into the membrane, which then protrudes from the other nostril and inflates like a big red balloon, like so:
Hooded Seals can be found in the central and western parts of the North Atlantic ocean. They are large, with adult males reaching lengths of 8.5 feet, and weighing 900 pounds (410 kg). Females are smaller, growing to only 6.7 feet in body length and weighing about 661 pounds (300 kg). Hooded Seal coats are a mixture of dark and light spots, each individual having a different pattern. Pups are called "blue backs" because their natal coats are light on their bellies and a dark blue-gray on their backs.
The diet of Hooded Seals consists primarily of crustaceans, fish, krill, starfish, squid and mussels. During the winter, they tend to consume large amounts of small forage fish like capelin, which are rich in lipids and fatty acids. This helps them to build up their layer of blubber as insulation against the cold, which is important because they tend to make deep dives in search of food. Their dives can range from 330 to 1,970 feet (100 to 600 meters) and can last up to 25 minutes. Longer dives have been observed, at even lower depths (52 minutes and 3,333 feet/1,016 meters), but they are not as common.
Hooded Seals are not as social as other pinnipeds, and tend to be more aggressive and territorial with each other. Between adult males, that's where the inflated "hood" comes into play - this display is intended to ward off the other males, and hopefully avoid a fight. Pupping and breeding season takes place from March to May, and while males will often mate with more than one female per season, they will at times act protectively toward just one female, chasing off other interested males. Pups are nursed for only 4 days, which is the shortest known lactation period of any mammal species. Hooded Seal milk is incredibly rich in fat, however, and pups gain 15 pounds (7 kg) each day they nurse. They will stay on the ice for some weeks before they are big enough to enter the water, but they don't shed their natal coats until 14 months.
The Hooded Seal has been a hunting staple of the First Nations people of Greenland and Canada for hundreds of years, but the over-hunting that significantly decreased most pinniped populations during the 19th and early 20th century did not spare these animals. Legislative measures intended to protect Hooded Seals have also had an impact on the First Nations peoples, and negotiations about yearly quotas and treaties have had to take into account the health of the overall population. Despite these measures, the northeast Atlantic population is still declining. Hooded Seals are also negatively affected by climate change, oil spills and getting tangled up in the equipment of commercial fisheries.
Source for all images used in this post.