View source for Ross seal

{{Short description|Species of mammal}}
{{Speciesbox
| name = Ross seal
| image = Ommatophoca rossii (Ross Seal), off Wilkes Land, Antarctica 1.jpg
| image_caption = Ross seal off Wilkes Land, Antarctica
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="iucn status 12 November 2021">{{cite iucn |author=Hückstädt, L. |date=2015 |title=''Ommatophoca rossii'' |volume=2015 |page=e.T15269A45228952 |doi=10.2305/IUCN.UK.2015-4.RLTS.T15269A45228952.en |access-date=12 November 2021}}</ref>
| genus = Ommatophoca
| parent_authority = [[John Edward Gray|Gray]], 1844
| species = rossii
| authority = ([[John Edward Gray|Gray]], 1844)
| range_map = Ross Seal area.png
| range_map_caption = Ross seal range
}}

The '''Ross seal''' ('''''Ommatophoca rossii''''') is a [[true seal]] (family Phocidae) with a range confined entirely to the [[pack ice]] of [[Antarctica]]. It is the [[monotypic|only species]] of the genus '''''Ommatophoca'''''. First described during the [[Ross expedition]] in 1841, it is the smallest, least abundant and least well known of the Antarctic pinnipeds. Its distinctive features include disproportionately large eyes, whence its scientific name (''Ommato-'' meaning "eye", and ''phoca'' meaning "seal"), and complex, trilling and siren-like vocalizations. Ross seals are [[brachycephalic]] as they have a short broad muzzle, and also have shorter fur than any other seal.

==Taxonomy and evolution==

The Ross seal shares a recent common ancestor with three other extant Antarctic seals, which are together known as the [[lobodontine seals]]. The other species are the [[crabeater seal]] (''Lobodon carcinophaga''), [[leopard seal]] (''Hydrurga leptonyx'') and [[Weddell seal]] (''Leptonychotes weddelli'').<ref name="Fyler2005">{{Citation |title=Historical biogeography and phylogeny of monachine seals (Pinnipedia: Phocidae) based on mitochondrial and nuclear DNA data |last1=Fyler |first1=C. A. |last2=Reeder |first2=T.W. |last3=Berta |first3=A. |last4=Antonelis |first4=G. |last5=Aguilar |first5=A. |last6=Androukaki |first6=E. |year=2005 |journal=Journal of Biogeography |volume=32 |issue=7 |pages=1267–1279 |doi=10.1111/j.1365-2699.2005.01281.x|bibcode=2005JBiog..32.1267F |s2cid=15187438 }}</ref> These species, collectively belonging to the seal [[tribe (biology)|tribe]] Lobodontini, share teeth adaptations, including lobes and cusps useful for straining smaller prey items out of the water column. The ancestral Lobodontini likely diverged from its sister [[clade]], ''[[Mirounga]]'' (elephant seals) in the late [[Miocene]] to early [[Pliocene]], when they migrated southward and diversified rapidly in relative isolation around Antarctica.<ref name=Fyler2005/> However, the only fossils of Ross seals so far known date from much later, during the early [[Pleistocene]] of New Zealand.<ref name="Berta2012">{{cite journal |last1=Berta |first1=A. |last2=Churchill |first2=M. |year=2012 |title=Pinniped Taxonomy: evidence for species and subspecies |journal=Mammal Review |volume=42 |issue=3 |pages=207–234 |doi=10.1111/j.1365-2907.2011.00193.x}}</ref>

==Etymology==
The seal was named for [[James Clark Ross]]. <ref>{{cite book|last=Riffenburgh|first=Beau|title=Encyclopedia of the Antarctic|url=https://books.google.com/books?id=fRJtB2MNdJMC&pg=PA815|year=2007|publisher=Taylor & Francis|isbn=9780415970242|page=815}}</ref>

== Description ==
[[File:Ross Seal skull 1844.jpg|thumb|upright|left|Sketch of the Ross seal skull.]]
Ross seals reach a length of about {{convert|1.68|-|2.09|m|ft|abbr=on}} and weight of {{convert|129|-|216|kg|lbs|abbr=on}}; females are slightly larger at {{convert|1.96|-|2.5|m|ft|abbr=on}}.<ref name="iucn status 12 November 2021" /> A molecular genetic based technique has been established to confirm the sex of individuals in the laboratory.<ref>{{Cite journal|last1=Curtis|first1=Caitlin|last2=Stewart|first2=Brent S.|last3=Karl|first3=Stephen A.|date=2007-05-01|title=Sexing Pinnipeds with ZFX and ZFY Loci|journal=Journal of Heredity|language=en|volume=98|issue=3|pages=280–285|doi=10.1093/jhered/esm023|issn=0022-1503|pmid=17548861|doi-access=free}}</ref> Pups are about 1 m and 16&nbsp;kg at birth. The coat is colored dark-brown in the dorsal area and silvery-white beneath. At the onset of the Antarctic winter, the coat fades gradually to become light brown. At close range, the Ross seal can be easily identified by its large eyes, which are up to 7&nbsp;cm in diameter. They also have shorter muzzles.

The Ross seal is able to produce a variety of complex twittering and siren-like sounds that are performed on ice and underwater, where they carry for long distances.<ref name=Watkins1985>{{Citation | title = In-air and underwater sounds of the Ross seal, Ommatophoca rossi | url = http://link.aip.org/link/?JAS/77/1598/1 | year = 1985 | journal = The Journal of the Acoustical Society of America | pages = 1598–1600 | volume = 77 | issue = 4 | doi = 10.1121/1.392003 | last1 = Watkins | first1 =  William A. | last2 =  Carleton Ray | first2 =  G. | bibcode = 1985ASAJ...77.1598W | access-date = 2010-06-06| url-access = subscription }}</ref> The underwater siren sound can be composed of two harmonically unrelated superimposed tones that are pulsed with the same rhythm. Uniquely, the vocalizations, whether on ice or in water, are made with a closed mouth - emitting no air. The purpose of these sounds is unknown, though their distinctive nature and long range are likely to facilitate either encounters or avoidance of individuals.<ref name=Watkins1985/>

Compared to other earless seals, the Ross seal has reduced semicircular canals and parafollicular volume. These traits are adapted because of their preferred aquatic lifestyle.<ref>{{Cite journal |last=Loza |first=Cleopatra Mara |last2=Latimer |first2=Ashley E. |last3=Sánchez-Villagra |first3=Marcelo R. |last4=Carlini |first4=Alfredo A. |date=2017-10-11 |title=Sensory anatomy of the most aquatic of carnivorans: the Antarctic Ross seal, and convergences with other mammals |url=https://royalsocietypublishing.org/doi/10.1098/rsbl.2017.0489 |journal=Biology Letters |volume=13 |issue=10 |pages=20170489 |doi=10.1098/rsbl.2017.0489 |pmc=5665775 |pmid=29021317}}</ref>

== Range and population status ==
[[File:Researchers catching a Ross Seal in Antarctica - NOAA Photo Library.jpg|thumb|left|upright=0.94|Researchers attempting to capture a Ross seal in the [[Ross Sea]]]]
Although its close relatives [[Weddell seal]]s, [[crabeater seal]]s and [[leopard seal]]s are ubiquitous in Antarctic waters, the Ross seal is an uncommon and relatively unknown animal, considered to be the least common [[pack ice]] seal. It almost never leaves the [[Antarctic Ocean]], with the very rare exception of stray animals found around [[subantarctic islands]], and uniquely, off the south coast of [[Australia]]. Nonetheless, its distribution is circumpolar, with individuals found in low densities - usually singly - in very thick pack ice in all regions of the continent.

The total Ross seal population is estimated at around 130,000 individuals, but there is great uncertainty in this estimate (reported 95% [[confidence intervals]] range from 20,000 to 227,000).<ref name=Southwell2008>{{Citation
 | title = Estimating population status under conditions of uncertainty: the Ross seal in East Antarctica | year = 2008 | journal = Antarctic Science | pages = 123–133
 | volume = 20 | issue = 2 | last1 = Southwell | first1 =  C.J. | last2 =  Paxton | first2 =  C.G.M. | last3 =  Borchers | first3 =  D.L. | last4 =  Boveng | first4 =  P.L. | last5 =  Nordøy | first5 =  E.S. | last6 =  Blix | first6 =  A.S. | last7 =  De La Mare | first7 =  W.K. | doi=10.1017/s0954102007000879| bibcode = 2008AntSc..20..123S | s2cid = 130100515 | doi-access =  free }}</ref> Thus, very little is known about trends in the population.  A genetic survey did not detect evidence of a recent, sustained genetic bottleneck in this species,<ref>{{Cite journal|last1=Curtis|first1=Caitlin|last2=Stewart|first2=Brent S.|last3=Karl|first3=Stephen A.|date=2011-07-07|title=Genetically effective population sizes of Antarctic seals estimated from nuclear genes|journal=Conservation Genetics|language=en|volume=12|issue=6|pages=1435–1446|doi=10.1007/s10592-011-0241-x|bibcode=2011ConG...12.1435C |s2cid=732351|issn=1566-0621}}</ref> which suggests that populations do not appear to have suffered a detectable and sustained decline in the recent past.

Interactions with humans have been limited. They have been collected historically by Antarctic expeditions and for scientific collections. Their range does not generally overlap with commercial fishing.

== Feeding and reproductive behavior ==

Ross seal feeds primarily on 19% invertebrates, 47% [[squid]] and 34% [[fish]], primarily [[Antarctic silverfish]], in the [[pelagic]] zone.<ref name="Skinner19942">{{Citation |last1=Skinner |first1=J.D. |title=On some aspects of the biology of the Ross seal Ommatophoca rossii from King Haakon VII Sea, Antarctica |title-link=King Haakon VII Sea |journal=Polar Biology |volume=14 |issue=7 |page=472 |year=1994 |doi=10.1007/bf00239051 |s2cid=28880147 |last2=Klages |first2=NTW}}</ref> Competition with whales or other arctic seals reduces their highly specialized diet.<ref name=":0">{{Citation |last=Thomas |first=Jeannette A. |title=Ross Seal: Ommatophoca rossii |date=2009-01-01 |work=Encyclopedia of Marine Mammals (Second Edition) |pages=988–990 |editor-last=Perrin |editor-first=William F. |url=https://www.sciencedirect.com/science/article/abs/pii/B9780123735539002261 |access-date=2025-03-28 |place=London |publisher=Academic Press |isbn=978-0-12-373553-9 |last2=Rogers |first2=Tracey |editor2-last=Würsig |editor2-first=Bernd |editor3-last=Thewissen |editor3-first=J. G. M.}}</ref> Ross seals are presumed to be preyed upon by [[killer whale]]s (''Orcinus orca'') and leopard seals, large predators that share their Antarctic habitat, though there are no documented observations of predation. Haul-out behavior among Ross seals varies seasonally, with a preference for midday haul-outs observed in certain months (September, October, February, and December). The Ross Seal is a solitary species, therefore they do not gather in large breeding season.<ref name=":02">{{Citation |last=Thomas |first=Jeannette A. |title=Ross Seal: Ommatophoca rossii |date=2009-01-01 |work=Encyclopedia of Marine Mammals (Second Edition) |pages=988–990 |editor-last=Perrin |editor-first=William F. |url=https://www.sciencedirect.com/science/article/abs/pii/B9780123735539002261 |access-date=2025-03-28 |place=London |publisher=Academic Press |isbn=978-0-12-373553-9 |last2=Rogers |first2=Tracey |editor2-last=Würsig |editor2-first=Bernd |editor3-last=Thewissen |editor3-first=J. G. M.}}</ref> Additionally, during the breeding season, female seals entering the pack ice engage in continuous haul-outs lasting 5 to 7 days. These periods are occasionally interrupted by brief water entries lasting 1 to 3 hours, indicating a potential alternation between capital and facultative income breeding strategies.<ref>{{Cite journal |last=Wege |first=Mia |last2=Bornemann |first2=Horst |last3=Bester |first3=Marthán Nieuwoudt |date=February 2023 |title=The nightlife of a Ross seal: diving and haul-out behaviour from the eastern Weddell Sea |url=https://www.cambridge.org/core/product/identifier/S0954102022000438/type/journal_article |journal=Antarctic Science |language=en |volume=35 |issue=1 |pages=31–42 |doi=10.1017/S0954102022000438 |issn=0954-1020|hdl=2263/93347 |hdl-access=free }}</ref>

Females give birth to their young on the ice in November. Ross seal pups are taken care of on the ice rather than water where they are less likely to be attacked.<ref name=":2">{{Cite journal |last=Arcalís-Planas |first=Anna |last2=Sveegaard |first2=Signe |last3=Karlsson |first3=Olle |last4=Harding |first4=Karin C. |last5=Wåhlin |first5=Anna |last6=Harkonen |first6=Tero |last7=Teilmann |first7=Jonas |date=2015-04-01 |title=Limited use of sea ice by the Ross seal (Ommatophoca rossii), in Amundsen Sea, Antarctica, using telemetry and remote sensing data |url=https://link.springer.com/article/10.1007/s00300-014-1602-y |journal=Polar Biology |language=en |volume=38 |issue=4 |pages=445–461 |doi=10.1007/s00300-014-1602-y |issn=1432-2056|url-access=subscription }}</ref> Pups are nursed for only four weeks before [[weaning]]. Mating is thought to occur underwater shortly after the pup is weaned, but has never been observed. The species is more resilient towards ice loss because of their extensive use of water over ice for the majority of their life.<ref name=":22">{{Cite journal |last=Arcalís-Planas |first=Anna |last2=Sveegaard |first2=Signe |last3=Karlsson |first3=Olle |last4=Harding |first4=Karin C. |last5=Wåhlin |first5=Anna |last6=Harkonen |first6=Tero |last7=Teilmann |first7=Jonas |date=2015-04-01 |title=Limited use of sea ice by the Ross seal (Ommatophoca rossii), in Amundsen Sea, Antarctica, using telemetry and remote sensing data |url=https://link.springer.com/article/10.1007/s00300-014-1602-y |journal=Polar Biology |language=en |volume=38 |issue=4 |pages=445–461 |doi=10.1007/s00300-014-1602-y |issn=1432-2056|url-access=subscription }}</ref> Ross seals mature sexually at approximately three years of age, and are thought to live around 20 years in the wild.<ref name="Skinner1994">{{Citation |last1=Skinner |first1=J.D. |title=On some aspects of the biology of the Ross seal Ommatophoca rossii from King Haakon VII Sea, Antarctica |title-link=King Haakon VII Sea |journal=Polar Biology |volume=14 |issue=7 |page=472 |year=1994 |doi=10.1007/bf00239051 |s2cid=28880147 |last2=Klages |first2=NTW}}</ref>

==See also==
{{Portal bar|Marine life|Mammals}}

==References==
{{Reflist}}

==External links ==
{{Commons category|Ommatophoca rossii}}
* [http://animaldiversity.ummz.umich.edu/site/accounts/information/Ommatophoca_rossii.html University of Michigan museum of zoology]
* [https://web.archive.org/web/20051217225012/http://www.pinnipeds.org/species/ross.htm Seal conservation society webpage]
* [http://www.fao.org/figis/servlet/species?sname=Ommatophoca%20rossii&sname_op=is Fisheries Global Information System factsheet]

{{Carnivora|C1.}}
{{Pan-Pinnipedia|P.|state=autocollapse}}
{{Taxonbar|from=Q837610}}
{{Authority control}}

[[Category:Lobodontins]]
[[Category:Mammals described in 1844]]
[[Category:Mammals of South Australia]]
[[Category:Pinnipeds of Antarctica]]
[[Category:Taxa named by John Edward Gray]]
[[Category:Vulnerable fauna of Australia]]