Editing Harp seal (section)

===Physiology===
The harp seal is a modest [[:Category:Diving animals|diver]].<ref name="Perrin-2009" /> Dive depth varies with [[season]], [[time of day]] and [[location]]. In the [[Greenland Sea]] sub-population, the average dive rate is around 8.3 dives per hour and dives range from a depth of less than {{convert|20|m|abbr=on}} to over {{convert|500|m|abbr=on}}.<ref name="Folkow-2004">{{Cite journal|last1=Folkow|first1=L.P.|last2=Nordøy|first2=E.S.|s2cid=27841378|date=2004|title=Distribution and diving behaviour of harp seals (Pagophilus groenlandicus) from the Greenland Sea stock|journal=Polar Biology |volume=27 |issue=5 |pages=281–298 |doi=10.1007/s00300-004-0591-7|bibcode=2004PoBio..27..281F }}</ref> Dive duration ranges from less than two minutes to just over 20 minutes.<ref name="Folkow-2004" /> During the spring and summer when seals forage along the [[pack ice]] in the Greenland Sea, most dives are less than {{convert|50|m|abbr=on}}.<ref name="Folkow-2004" /> In the late fall and winter, dive depth has been found to increase, particularly in the [[Denmark Strait]], where the mean dive depth was found to be {{convert|141|m|abbr=on}}.<ref name="Folkow-2004" />

Lactating female harp seals spend about 80% of the time in the water and 20% of the time on the [[fast ice]], [[weaning]] or staying near their pups. However, almost half of the time spent in the water is at the surface, well beyond what is expected to recover from dives.<ref name="Lydersen, Christian 1993">{{cite journal |last1=Lydersen |first1=Christian |first2=Kit M. |last2=Kovacs |s2cid=53203432 |title=Diving behaviour of lactating harp seal, ''Phoca groenlandica'', females from the Gulf of St Lawrence, Canada |journal=Animal Behaviour |volume=46 |issue=6 |year=1993 |pages=1213–1221 |doi=10.1006/anbe.1993.1312}}</ref> This behavior allows the mother harp seal to conserve energy and avoid the harsh conditions of the fast-ice while remaining near her pup. As with most phocids, she requires vast amounts of energy to ensure sufficient mass transfer to her growing, weaning pup.  Harp seals remain within their aerobic dive limit for 99% of dives.<ref name="Lydersen, Christian 1993"/>

====Thermoregulation====
[[File:Blanchon-idlm2006.jpg|thumb|left|Whitecoated pup]]
Harp seal [[Thermal insulation|insulation]] changes over the course of a seal's lifetime. Young harp seals rely on a lanugo [[pelt]] from nursing all the way up to their [[weaning]] age.<ref name="Pearson 501–511">{{Cite journal |last1=Pearson |first1=Linnea E. |last2=Weitzner |first2=Emma L. |last3=Burns |first3=Jennifer M. |last4=Hammill |first4=Mike O. |last5=Liwanag |first5=Heather E. M. |date=August 2019 |title=From ice to ocean: changes in the thermal function of harp seal pelt with ontogeny |url=http://link.springer.com/10.1007/s00360-019-01214-y |journal=Journal of Comparative Physiology B |language=en |volume=189 |issue=3–4 |pages=501–511 |doi=10.1007/s00360-019-01214-y |pmid=30923894 |s2cid=253890521 |issn=0174-1578|url-access=subscription }}</ref> The insulating quality of this fur depends on its ability to keep a layer of air trapped inside or between the hairs.<ref name="Kvadsheim 952–962">{{Cite journal |last1=Kvadsheim |first1=P. H. |last2=Aarseth |first2=J. J. |title=Thermal Function of Phocid Seal Fur |date=October 2002 |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2002.tb01084.x |journal=Marine Mammal Science |language=en |volume=18 |issue=4 |pages=952–962 |doi=10.1111/j.1748-7692.2002.tb01084.x |bibcode=2002MMamS..18..952K |issn=0824-0469|url-access=subscription }}</ref> It takes a year for their blubber to develop and for their first-year [[pelage]] to grow. This transition from thick [[lanugo]] fur to [[blubber]] is important because lanugo fur does not insulate well in water.<ref name="Pearson 501–511"/> Adult harp seals primarily use blubber for insulation.<ref name="Bioweb"/>

Harp seals combine [[anatomical]] and [[Ethology|behavioral]] approaches to managing their [[body temperature]]s, instead of elevating their [[metabolic rate]] and subsequently their energy requirements.<ref>{{cite journal |last1=Lavigne |first1=D. |last2=Innes |first2=S. |last3=Worthy |first3=G. |last4=Kovacs |first4=K. |last5=Schmitz |first5=O. |last6=Hickie |first6=J. |year=1986 |title=Metabolic rates of seals and whales |journal=Canadian Journal of Zoology |volume=64 |issue=2 |pages=279–284 |doi=10.1139/z86-047|bibcode=1986CaJZ...64..279L }}</ref> Their lower critical temperature is believed to be under {{convert|-10|C|abbr=on}} in air.<ref>{{Cite journal|last1=Boily|first1=Patrice|last2=Lavigne|first2=David M.|year=1996|title=Thermoregulation of juvenile grey seals, ''Halichoerus grypus'', in air|journal=Canadian Journal of Zoology|volume=74|issue=2|pages=201–208|doi=10.1139/z96-025|bibcode=1996CaJZ...74..201B |issn=0008-4301}}</ref> A thick coat of [[blubber]] insulates its body and provides energy when food is scarce or during [[fasting]].<ref name="Bioweb">{{Cite web|url=http://bioweb.uwlax.edu/bio203/s2012/lind_vale/adaptation.htm|title=Adaptation of the Harp Seal|website=bioweb.uwlax.edu|language=en-us|access-date=2018-04-03}}</ref> Blubber also [[wikt:streamline|streamline]]s its body for more efficient swimming. [[Brown fat]] warms [[blood]] as it returns from the body surface as well as providing energy, most importantly for newly weaned pups.<ref name="Perrin-2009" /> This blubber insulates the harp seal's core but does not insulate the flippers to the same extent. Instead, the flippers have circulatory adaptations to help prevent heat loss.<ref>{{Cite journal|last1=Kvadsheim|first1=P. H.|last2=Folkow|first2=L. P.|year=1997|title=Blubber and flipper heat transfer in harp seals|journal=Acta Physiologica Scandinavica|volume=161|issue=3|pages=385–395|doi=10.1046/j.1365-201x.1997.00235.x|pmid=9401592|issn=0001-6772}}</ref> [[Flipper (anatomy)|Flippers]] act as heat exchangers, warming or cooling the seal as needed. On ice, the seal can press its fore flippers to its body and its hind flippers together to reduce heat loss.<ref name="Perrin-2009" /> 

They can also redirect blood flow from the periphery to minimize heat loss;<ref name="Bioweb" /> the nostrils and eyes of harp seals are adapted to conserve heat, possessing a [[countercurrent heat exchange]] system and [[Rete mirabile|retia mirabile]], respectively.<ref>{{cite journal |last1=FOLKOW |first1=L. P. |last2=BLIX |first2=A. S. |last3=EIDE |first3=T. J. |title=Anatomical and functional aspects of the nasal mucosal and ophthalmic retia of phocid seals |journal=Zoology |date=November 1988 |volume=216 |issue=3 |pages=417–436 |doi=10.1111/j.1469-7998.1988.tb02439.x |url=https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1988.tb02439.x |access-date=20 March 2025|url-access=subscription }}</ref> 

====Senses====
The harp seal's eyes are large for its body size and contain a large [[spherical]] lens that improves focusing ability. Its mobile [[pupil]] helps it adapt to the intense [[Glare (vision)|glare]] of the Arctic ice. Its [[retina]] is [[Rod cell|rod]]-dominated and backed by a [[cat]]-like and reflective [[tapetum lucidum]], enhancing its low light sensitivity. Its [[cornea]] is lubricated by [[lacrimal gland]]s, to protect the eye from sea water damage.<ref name="Perrin-2009" />

On ice, the mother identifies her offspring by [[Olfaction|smell]]. This sense may also warn of an approaching [[predator]]. Underwater, the seal closes its nostrils, disabling its sense of smell.<ref name="Perrin-2009" />

Its whiskers, or [[vibrissae]], lie in horizontal rows on either side of its snout. They can sense to low-frequency [[vibration]]s, and may be able to detect movement of nearby animals during dives.<ref name="Perrin-2009" />