Hooded seal (Cystophora cristata)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



The hooded seal is a relatively large seal, famous for its balloon-like nasal appendage. It has a small head, reaches up to 2.5 m in length and weighs up to 400 kg. Males are typically longer and heavier than females. Its flippers are short compared to the size of the body and are dark in colour. The face is completely black. The young are generally blue all over with silver bellies. After maturity, it develops a silver to greyish body colour with irregular dark spots over most of the body. Males have a distinct nasal appendage that hangs as a sac over the nose. When inflated this sac covers the front of the face and top of the head. The sac is dark in colour. Males can also inflate an elastic balloon-like bladder from one nostril. The bladder appears red and can cover part of the face.

Recorded distribution in Britain and Ireland

Cystophora cristata is probably an occasional visitor (vagrant) to the waters of Britain and Ireland.

Global distribution

Recorded in the Arctic Ocean and the high latitudes of the North Atlantic. The majority of hooded seals (Cystophora cristata) are recorded off the east coast of Canada, Davis Strait, West Ice and the east of Greenland. It has also been sighted in the Strait of Gibraltar and off the Spanish coasts of the Mediterranean Sea.


The hooded seal is a marine neritic and oceanic species. It is associated with sea ice and exhibits seasonal migration with females and males keeping separate except when meeting to breed in the spring.

Depth range

0-1000 m

Identifying features

  • Relatively large reaching 2.5 m in length.
  • Small head with short dark flippers.
  • Dark face with a silver to grey body colouration with irregular dark spots.
  • Dark nasal appendage that hangs as a sac or is inflated to cover part of the face and top of the head.
  • Red balloon-like bladder that appears from the nostril.

Additional information

Cystophora cristata are very efficient divers. They can dive to 1000 m for at least an hour. Diving depth and duration depend greatly on the season and are generally longer in the winter. This is thought to be associated with prey behaviour and the vertical distribution of fish and zooplankton (Folkow & Blix, 1999). Cystophora cristata stores oxygen in their blood and skeletal muscles during dives, which helps prevent diving hypoxia. Low oxygen levels can cause traumatic injuries or even death if they are prolonged. They also undergo cardiovascular alterations such as the constriction of capillaries to ensure oxygen is reaching the most vital organs e.g. the heart and the brain. The brain of Cystophora cristata has cerebral neurones, located in the uppermost part of the brain, that have a high tolerance to hypoxia and are able to fire effective signals during long dives (Folkow et al., 2008).


  1. Kovacs, K.M. 2016. Cystophora cristataThe IUCN Red List of Threatened Species 2016: e.T6204A45225150. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T6204A45225150.en. Downloaded on 09 February 2021.

  2. Folkow, L.P. & Blix, A.S., 1999. Diving behaviour of hooded seals (Cystophora cristata) in the Greenland and Norwegian Seas. Polar Biology, 22 (1), 61-74. DOI https://doi.org/10.1007/s003000050391
  3. Folkow, L.P., Ramirez, J.M., Ludvigsen, S., Ramirez, N. & Blix, A.S., 2008. Remarkable neuronal hypoxia tolerance in the deep-diving adult hooded seal (Cystophora cristata). Neuroscience Letters, 446 (2-3), 147-150. DOI https://doi.org/10.1016/j.neulet.2008.09.040
  4. Kovacs, K.M., 2009. Hooded Seal: Cystophora cristata. In Perrin, W.F., Würsig, B. and Thewissen, J.G.M. (eds.). Encyclopedia of Marine Mammals (Second Edition), London: Academic Press, pp. 569-573. Available from: https://doi.org/10.1016/B978-0-12-373553-9.00132-2


  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-07-14


This review can be cited as:

Nash, R.A., -unspecified-. Cystophora cristata Hooded seal. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 14-07-2024]. Available from: https://www.marlin.ac.uk/species/detail/2333

Last Updated: 01/01/1970