Editing Narwhal (section)

== Behaviour and ecology ==

[[File:Narwhal tail above surface.jpg|thumb|Narwhal tail fluke|alt=Photo depicting narwhal tail flukes, which are broad, flat, and horizontal in shape.]]

Narwhals normally [[Sociality|congregate in groups]] of three to eight individuals. Groups may be "nurseries" with only females and young, or can contain only juveniles or adult males ("bulls"); mixed groups can occur at any time of year.<ref name=":22" /><ref name=":21" /><ref>{{Cite book |last=Beer |first=Amy-Jane |url=http://archive.org/details/encyclopediaofno0000beer |title=Encyclopedia of North American mammals |date=2004 |publisher=San Diego, Calif. : Thunder Bay Press |others=Internet Archive |isbn=978-1-59223-191-1 |pages=122}}</ref> In the summer, several groups come together, forming larger aggregations which can contain 500 to over 1,000 individuals.<ref name= Macdonald/><ref name=":20" /> Male narwhals have been observed rubbing each other's tusks, a behaviour known as "tusking".<ref name="Broad" /><ref name="NOAA Ocean Explorer">{{Cite web |title=The biology and ecology of narwhals |url=http://oceanexplorer.noaa.gov/explorations/06arctic/background/biology/biology.html |url-status=live |archive-url=https://web.archive.org/web/20220814234737/https://oceanexplorer.noaa.gov/explorations/06arctic/background/biology/biology.html |archive-date=14 August 2022 |access-date=15 January 2009 |website=noaa.gov |publisher=National Oceanic and Atmospheric Administration}}</ref>

When in their wintering waters, narwhals make some of the deepest dives recorded for cetaceans, diving to at least {{cvt|800|m|ft|-1|abbr=off}} over 15 times per day, with many dives reaching {{cvt|1,500|m|ft|-1|abbr=off}}.<ref name="laidre2003" /><ref>{{Cite journal |last=Kumar |first=Mohi |date=March 2011 |title=Research Spotlight: Narwhals document continued warming of Baffin Bay |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2011EO090009 |journal=Eos, Transactions American Geophysical Union |language=en |volume=92 |issue=9 |pages=80 |bibcode=2011EOSTr..92...80K |doi=10.1029/2011EO090009 |issn=0096-3941}}</ref> The greatest dive depth recorded is {{cvt|2370|m|ft}}.<ref name="laidre2003" /><ref name="davis">{{Cite book |last=Davis |first=Randall W. |title=Marine Mammals. Adaptations for an Aquatic Life |publisher=Springer |year=2019 |isbn=978-3319982786 |location=Berlin/Heidelberg |chapter=Appendix 3. Maximum Recorded Dive Depths and Durations for Marine Mammals}}</ref> Dives last up to 25 minutes, and vary in depth depending on the season and local variation between environments. For example, in the Baffin Bay wintering grounds, narwhals tend to dive deep within the steep coasts, typically south of Baffin Bay. This suggests differences in habitat structure, prey availability, or genetic adaptations between subpopulations. In the northern wintering grounds, narwhals do not dive as deep as the southern population, in spite of greater water depths in these areas. This is mainly attributed to prey being concentrated nearer to the surface, which causes narwhals to alter their foraging strategies.<ref name="laidre2003">{{Cite journal |last1=Laidre |first1=Kristin L. |last2=Heide-Jørgensen |first2=Mads Peter |last3=Dietz |first3=Rune |last4=Hobbs |first4=Roderick C. |last5=Jørgensen |first5=Ole A. |date=17 October 2003 |title=Deep-diving by narwhals (''Monodon monoceros''): differences in foraging behavior between wintering areas? |url=https://www.int-res.com/abstracts/meps/v261/p269-281/ |journal=Marine Ecology Progress Series |language=en |volume=261 |pages=269–281 |bibcode=2003MEPS..261..269L |doi=10.3354/meps261269 |issn=0171-8630}}</ref>

=== Diet ===
Narwhals have a restricted and specialised diet.<ref name="Laidre2005" /><ref name=":18">{{Cite journal |last1=Chambault |first1=P. |last2=Tervo |first2=O. M. |last3=Garde |first3=E. |last4=Hansen |first4=R. G. |last5=Blackwell |first5=S. B. |last6=Williams |first6=T. M. |last7=Dietz |first7=R. |last8=Albertsen |first8=C. M. |last9=Laidre |first9=K. L. |last10=Nielsen |first10=N. H. |last11=Richard |first11=P. |last12=Sinding |first12=M. H. S. |last13=Schmidt |first13=H. C. |last14=Heide-Jørgensen |first14=M. P. |date=29 October 2020 |title=The impact of rising sea temperatures on an Arctic top predator, the narwhal |journal=Scientific Reports |language=en |volume=10 |issue=1 |pages=18678 |bibcode=2020NatSR..1018678C |doi=10.1038/s41598-020-75658-6 |issn=2045-2322 |pmc=7596713 |pmid=33122802}}</ref> Due to the lack of well-developed [[dentition]], narwhals are believed to feed by swimming close to prey and [[Suction feeding|sucking]] them into the mouth.<ref>{{Cite journal |last1=Jensen |first1=Frederik H. |last2=Tervo |first2=Outi M. |last3=Heide-Jørgensen |first3=Mads Peter |last4=Ditlevsen |first4=Susanne |date=25 March 2023 |title=Detecting narwhal foraging behaviour from accelerometer and depth data using mixed-effects logistic regression |journal=Animal Biotelemetry |volume=11 |issue=1 |pages=14 |bibcode=2023AnBio..11...14J |doi=10.1186/s40317-023-00325-2 |issn=2050-3385 |doi-access=free}}</ref> A study of the stomach contents of 73 narwhals found Arctic cod (''[[Boreogadus|Boreogadus saida]]'') to be the most commonly consumed prey, followed by Greenland halibut (''[[Reinhardtius hippoglossoides]]''). Large quantities of Boreo-Atlantic armhook squid (''[[Gonatus fabricii]]'') were also discovered. Male specimens had a higher likelihood of showing two additional prey species within their stomach contents: polar cod (''[[Arctogadus glacialis]]'') and redfish (''[[Sebastes marinus]]''), both of which are found at depths of more than {{cvt|500|m}}. The study also concluded that the size of prey did not differ between genders or age groups.<ref name="Finley1982" /> Other items found within narwhal stomach contents include [[wolffish]], [[capelin]], [[Skate (fish)|skate]] eggs and sometimes rocks.<ref name= Macdonald/><ref name="Laidre2005" /><ref name="Laidre2004">{{Cite journal |last1=Laidre |first1=K. L. |last2=Heide-Jørgensen |first2=M. P. |last3=Jørgensen |first3=O. A. |last4=Treble |first4=M. A. |date=1 January 2004 |title=Deep-ocean predation by a high Arctic cetacean |url=http://dx.doi.org/10.1016/j.icesjms.2004.02.002 |journal=ICES Journal of Marine Science |volume=61 |issue=3 |pages=430–440 |bibcode=2004ICJMS..61..430L |doi=10.1016/j.icesjms.2004.02.002 |issn=1095-9289}}</ref>

Narwhal diet varies between seasons. In winter, narwhals feed on [[Demersal fish|demersal]] prey, mostly [[flatfish]], under dense pack ice. During the summer, they eat mostly Arctic cod and Greenland halibut, with other fish such as polar cod making up the remainder of their diet.<ref name="Finley1982">{{Cite journal |last1=Finley |first1=K. J. |last2=Gibb |first2=E. J. |date=December 1982 |title=Summer diet of the narwhal (''Monodon monoceros'') in Pond Inlet, northern Baffin Island |journal=Canadian Journal of Zoology |volume=60 |issue=12 |pages=3353–3363 |doi=10.1139/z82-424 |bibcode=1982CaJZ...60.3353F |issn=0008-4301}}</ref> Narwhals consume more food in the winter months than they do in summer.<ref name="Laidre2005" /><ref name="Laidre2004" />

=== Breeding ===

Most female narwhals reproduce by the time they are six to eight years old.<ref name="Fisheries and Oceans Canada" /> [[courtship display|Courtship]] and [[Reproduction|mating]] behaviour for the species has been recorded from March to May, when they live among offshore pack ice, and is thought to involve a dominant male mating with several partners. The average [[gestation]] period lasts 15 months, and births appear to be most frequent between July and August. Female narwhals have a birth interval of around 2–3 years.<ref name=":4">{{Cite journal |last1=Garde |first1=Eva |last2=Hansen |first2=Steen H. |last3=Ditlevsen |first3=Susanne |last4=Tvermosegaard |first4=Ketil Biering |last5=Hansen |first5=Johan |last6=Harding |first6=Karin C. |last7=Heide-Jørgensen |first7=Mads Peter |date=7 July 2015 |title=Life history parameters of narwhals (''Monodon monoceros'') from Greenland |url=http://dx.doi.org/10.1093/jmammal/gyv110 |url-status=live |journal=Journal of Mammalogy |volume=96 |issue=4 |pages=866–879 |doi=10.1093/jmammal/gyv110 |issn=0022-2372 |archive-url=https://web.archive.org/web/20240128092012/https://academic.oup.com/jmammal/article/96/4/866/853421 |archive-date=28 January 2024 |access-date=22 January 2024}}</ref><ref name=":24">{{Cite book |url=https://books.google.com/books?id=QynOriR1MxEC&dq=Narwhal+reproduction&pg=PA85 |title=Dolphins, Porpoises and Whales of the World: The IUCN Red Data Book |date=1991 |publisher=IUCN |isbn=2-88032-936-1 |editor-last=Klinowska |editor-first=Margaret |pages=79 |language=en |access-date=28 January 2024 |archive-url=https://web.archive.org/web/20240128091605/https://books.google.com/books?id=QynOriR1MxEC&dq=Narwhal+reproduction&pg=PA85#v=onepage&q=Narwhal%20reproduction&f=false |archive-date=28 January 2024 |url-status=live}}</ref><ref>{{Citation |last1=Würsig |first1=Bernd |title=Sex and Behavior |date=2023 |work=Sex in Cetaceans: Morphology, Behavior, and the Evolution of Sexual Strategies |pages=1–27 |editor-last=Würsig |editor-first=Bernd |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-031-35651-3_1 |isbn=978-3-031-35651-3 |last2=Rich |first2=Jacquline |last3=Orbach |first3=Dara N. |editor2-last=Orbach |editor2-first=Dara N. |doi-access=free}}</ref> As with most marine mammals, only a single calf is born, averaging {{cvt|1.5|m|ft|abbr=off}} in length with white or light grey pigmentation.<ref>{{Cite book |last=Tinker |first=Spencer Wilkie |url=https://books.google.com/books?id=ASIVAAAAIAAJ&dq=Narwhal+reproduction&pg=PA213 |title=Whales of the World |date=1988 |publisher=E. J. Brill |isbn=0-935848-47-9 |pages=213 |language=en |access-date=28 January 2024 |archive-url=https://web.archive.org/web/20240128091622/https://books.google.com/books?id=ASIVAAAAIAAJ&dq=Narwhal+reproduction&pg=PA213#v=onepage&q=Narwhal%20reproduction&f=false |archive-date=28 January 2024 |url-status=live}}</ref><ref>{{Citation |last=Mann |first=Janet |title=Parental Behavior |date=1 January 2009 |pages=830–836 |editor-last=Perrin |editor-first=William F. |editor-last2=Würsig |editor-first2=Bernd |editor-last3=Thewissen |editor-first3=J. G. M. |url=https://www.sciencedirect.com/science/article/pii/B9780123735539001942 |access-date=17 July 2024 |place=London |publisher=Academic Press |isbn=978-0-12-373553-9|encyclopedia=Encyclopedia of Marine Mammals (Second Edition)}}</ref> Summer population surveys along different coastal inlets of [[Baffin Island]] found that calf numbers varied from 0.05% of 35,000 in [[Admiralty Inlet (Nunavut)|Admiralty Inlet]], to 5% of 10,000 total in [[Eclipse Sound]]. These findings suggest that higher calf counts may reflect calving and nursery habitats in favourable inlets.<ref name="newsci">{{Cite magazine |last=Evans Ogden, Lesley |date=6 January 2016 |title=Elusive narwhal babies spotted gathering at Canadian nursery |url=https://www.newscientist.com/article/dn28729-elusive-narwhal-babies-spotted-gathering-at-canadian-nursery/ |url-status=live |archive-url=https://web.archive.org/web/20160921124956/https://www.newscientist.com/article/dn28729-elusive-narwhal-babies-spotted-gathering-at-canadian-nursery/ |archive-date=21 September 2016 |access-date=6 September 2016 |magazine=New Scientist}}</ref>

Newborn calves begin their lives with a thin layer of blubber. The blubber thickens as they [[lactation|nurse]] their mother's milk, which is rich in fat; calves are dependent on milk for about 20 months.<ref name="Macdonald" /><ref name=":23" /> This long lactation period gives calves time to learn the skills they will need to survive as they mature.<ref name="newsci" /><ref name=":23">{{Cite journal |last1=Zhao |first1=Shu-Ting |last2=Matthews |first2=Cory J. D. |last3=Davoren |first3=Gail K. |last4=Ferguson |first4=Steven H. |last5=Watt |first5=Cortney A. |date=24 June 2021 |title=Ontogenetic profiles of dentine isotopes (δ15N and δ13C) reveal variable narwhal Monodon monoceros nursing duration |url=https://www.int-res.com/abstracts/meps/v668/p163-175/ |journal=Marine Ecology Progress Series |language=en |volume=668 |pages=163–175 |bibcode=2021MEPS..668..163Z |doi=10.3354/meps13738 |issn=0171-8630|url-access=subscription }}</ref> Narwhals are among the few animals that undergo [[menopause]] and live for decades after they have finished breeding. Females in this phase may continue to protect calves in the pod.<ref name=":4" /><ref name="Menopause in narwhals" /> A 2024 study concluded that five species of [[toothed whale]] evolved menopause to acquire higher overall longevity, although their reproductive periods did not change. To explain this, scientists hypothesised that calves of these species require the assistance of (post-)menopausal females for an enhanced chance at survival, as they are extremely difficult for a single female to successfully rear.<ref name="Menopause in narwhals">{{Cite journal |last1=Ellis |first1=Samuel |last2=Franks |first2=Daniel W. |last3=Nielsen |first3=Mia Lybkær Kronborg |last4=Weiss |first4=Michael N. |last5=Croft |first5=Darren P. |date=13 March 2024 |title=The evolution of menopause in toothed whales |journal=Nature |language=en |volume=627 |issue=8004 |pages=579–585 |bibcode=2024Natur.627..579E |doi=10.1038/s41586-024-07159-9 |issn=1476-4687 |pmc=10954554 |pmid=38480878 |doi-access=free}}</ref>

=== Communication ===
{{See also|Whale vocalization}}
Like most toothed whales, narwhals use sound to navigate and hunt for food. They primarily vocalise through clicks, whistles and knocks, created by air movement between chambers near the [[Blowhole (anatomy)|blowhole]].<ref>{{Cite journal |last1=Blackwell |first1=Susanna B. |last2=Tervo |first2=Outi M. |last3=Conrad |first3=Alexander S. |last4=Sinding |first4=Mikkel H. S. |last5=Hansen |first5=Rikke G. |last6=Ditlevsen |first6=Susanne |last7=Heide-Jørgensen |first7=Mads Peter |date=13 June 2018 |title=Spatial and temporal patterns of sound production in East Greenland narwhals |journal=PLOS ONE |language=en |volume=13 |issue=6 |pages=e0198295 |bibcode=2018PLoSO..1398295B |doi=10.1371/journal.pone.0198295 |issn=1932-6203 |pmc=5999075 |pmid=29897955 |doi-access=free}}</ref><ref name=":25">{{Citation |last=Wei |first=Chong |title=Chapter 17 - Sound production and propagation in cetaceans |date=1 January 2021 |work=Neuroendocrine Regulation of Animal Vocalization |pages=267–295 |editor-last=Rosenfeld |editor-first=Cheryl S. |editor-last2=Hoffmann |editor-first2=Frauke |url=https://www.sciencedirect.com/science/article/pii/B978012815160000013X |access-date=18 July 2024 |publisher=[[Academic Press]] |isbn=978-0-12-815160-0 }}</ref> The frequency of these sounds ranges from 0.3 to 125 [[hertz]], while those used for [[Animal echolocation|echolocation]] typically fall between 19 and 48 hertz.<ref>{{Cite book |last1=Still |first1=Robert |url=https://books.google.com/books?id=z9B-DwAAQBAJ&dq=Narwhal+reproduction&pg=PA161 |title=Europe's Sea Mammals Including the Azores, Madeira, the Canary Islands and Cape Verde: A field guide to the whales, dolphins, porpoises and seals |last2=Harrop |first2=Hugh |last3=Dias |first3=Luís |last4=Stenton |first4=Tim |date=2019 |publisher=Princeton University Press |isbn=978-0-691-19062-4 |pages=16 |language=en |access-date=28 January 2024 |archive-url=https://web.archive.org/web/20240128092010/https://books.google.com/books?id=z9B-DwAAQBAJ&dq=Narwhal+reproduction&pg=PA161#v=onepage&q=Narwhal%20reproduction&f=false |archive-date=28 January 2024 |url-status=live}}</ref><ref>{{Cite journal |last1=Miller |first1=Lee A. |last2=Pristed |first2=John |last3=Møshl |first3=Bertel |last4=Surlykke |first4=Annemarie |date=October 1995 |title=The click-sounds of narwhals (''Monodon monoceros'') in Inglefield Bay, Northwest Greenland |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.1995.tb00672.x |url-status=live |journal=Marine Mammal Science |language=en |volume=11 |issue=4 |pages=491–502 |bibcode=1995MMamS..11..491M |doi=10.1111/j.1748-7692.1995.tb00672.x |issn=0824-0469 |s2cid=85148204 |archive-url=https://web.archive.org/web/20221005045122/https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.1995.tb00672.x |archive-date=5 October 2022 |access-date=27 January 2024|url-access=subscription }}</ref> Sounds are reflected off the sloping front of the skull and focused by the animal's [[Melon (cetacean)|melon]]: a mass of fat which can be controlled through surrounding musculature.<ref name=":25" /><ref>{{Cite journal |last1=Senevirathna |first1=Jayan Duminda Mahesh |last2=Yonezawa |first2=Ryo |last3=Saka |first3=Taiki |last4=Igarashi |first4=Yoji |last5=Funasaka |first5=Noriko |last6=Yoshitake |first6=Kazutoshi |last7=Kinoshita |first7=Shigeharu |last8=Asakawa |first8=Shuichi |date=January 2021 |title=Transcriptomic insight into the melon morphology of toothed whales for aquatic molecular developments |journal=Sustainability |language=en |volume=13 |issue=24 |pages=13997 |doi=10.3390/su132413997 |issn=2071-1050 |doi-access=free}}</ref> Echolocation clicks are used for detecting prey and locating barriers at short distances.<ref name=":25" /><ref>{{Cite journal |last1=Zahn |first1=Marie J. |last2=Rankin |first2=Shannon |last3=McCullough |first3=Jennifer L. K. |last4=Koblitz |first4=Jens C. |last5=Archer |first5=Frederick |last6=Rasmussen |first6=Marianne H. |last7=Laidre |first7=Kristin L. |date=12 November 2021 |title=Acoustic differentiation and classification of wild belugas and narwhals using echolocation clicks |journal=Scientific Reports |language=en |volume=11 |issue=1 |pages=22141 |bibcode=2021NatSR..1122141Z |doi=10.1038/s41598-021-01441-w |issn=2045-2322 |pmc=8589986 |pmid=34772963}}</ref> Whistles and throbs are most commonly used to communicate with other pod members.<ref name=":25" /><ref>{{Cite journal |last1=Marcoux |first1=Marianne |last2=Auger-Méthé |first2=Marie |last3=Humphries |first3=Murray M. |date=October 2012 |title=Variability and context specificity of narwhal (''Monodon monoceros'') whistles and pulsed calls |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2011.00514.x |journal=Marine Mammal Science |language=en |volume=28 |issue=4 |pages=649–665 |bibcode=2012MMamS..28..649M |doi=10.1111/j.1748-7692.2011.00514.x |issn=0824-0469|url-access=subscription }}</ref> Calls recorded from the same pod are more similar than calls from different pods, suggesting the possibility of group- or individual-specific calls. Narwhals sometimes adjust the duration and pitch of their pulsed calls to maximise sound propagation in varying acoustic environments.<ref name="WinterWhales" /><ref>{{Cite journal |last=Shapiro |first=Ari D. |date=1 September 2006 |title=Preliminary evidence for signature vocalizations among free-ranging narwhals (''Monodon monoceros'') |url=http://dx.doi.org/10.1121/1.2226586 |journal=The Journal of the Acoustical Society of America |volume=120 |issue=3 |pages=1695–1705 |bibcode=2006ASAJ..120.1695S |doi=10.1121/1.2226586 |issn=0001-4966 |pmid=17004490 |hdl-access=free |hdl=1912/2355}}</ref> Other sounds produced by narwhals include trumpeting and "squeaking-door sounds".<ref name="Fisheries and Oceans Canada" /> The narwhal vocal repertoire is similar to that of the beluga whale. However, the frequency ranges, durations, and repetition rates of narwhal clicks differ from those of belugas.<ref>{{Cite journal |last1=Jones |first1=Joshua M. |last2=Frasier |first2=Kaitlin E. |last3=Westdal |first3=Kristin H. |last4=Ootoowak |first4=Alex J. |last5=Wiggins |first5=Sean M. |last6=Hildebrand |first6=John A. |date=1 March 2022 |title=Beluga (''Delphinapterus leucas'') and narwhal (''Monodon monoceros'') echolocation click detection and differentiation from long-term Arctic acoustic recordings |url=https://doi.org/10.1007/s00300-022-03008-5 |journal=Polar Biology |language=en |volume=45 |issue=3 |pages=449–463 |bibcode=2022PoBio..45..449J |doi=10.1007/s00300-022-03008-5 |issn=1432-2056 |s2cid=246176509|url-access=subscription }}</ref>

=== Longevity and mortality factors ===
[[File:A polar bear (Ursus maritimus) scavenging a narwhal whale (Monodon monoceros) carcass - journal.pone.0060797.g001-A.png|thumb|A polar bear [[scavenging]] a narwhal carcass|alt=Polar bear feeding/scavenging on a beached narwhal carcass.]]
Age determination techniques using the number of [[periosteum]] layers in the [[lower jaw]] reveal that narwhals live an average of 50 years, though techniques using [[amino acid dating]] from the [[Lens (vertebrate anatomy)|lens]] of the eyes suggest that female narwhals can reach 115{{Nbsp}}±{{Nbsp}}10 years and male narwhals can live to 84{{Nbsp}}±{{Nbsp}}9 years.<ref>{{Cite journal |last1=Garde |first1=Eva |last2=Heide-Jørgensen |first2=Mads Peter |last3=Hansen |first3=Steen H. |last4=Nachman |first4=Gösta |last5=Forchhammer |first5=Mads C. |date=28 February 2007 |title=Age-specific growth and remarkable longevity in narwhals (''Monodon monoceros'') from West Greenland as estimated by aspartic acid racemization |url=http://dx.doi.org/10.1644/06-mamm-a-056r.1 |journal=Journal of Mammalogy |volume=88 |issue=1 |pages=49–58 |doi=10.1644/06-mamm-a-056r.1 |issn=0022-2372}}</ref>

Death by [[suffocation]] often occurs when narwhals fail to migrate before the [[Climate change in the Arctic|Arctic freezes over]] in late autumn. This is known as "sea-ice entrapment".<ref name="Macdonald" /><ref name=":7">{{Cite journal |last1=Laidre |first1=Kristin |last2=Heide-Jørgensen |first2=Mads Peter |last3=Stern |first3=Harry |last4=Richard |first4=Pierre |date=1 January 2012 |title=Unusual narwhal sea ice entrapments and delayed autumn freeze-up trends |url=https://doi.org/10.1007/s00300-011-1036-8 |journal=Polar Biology |language=en |volume=35 |issue=1 |pages=149–154 |bibcode=2012PoBio..35..149L |doi=10.1007/s00300-011-1036-8 |issn=1432-2056 |s2cid=253807718|url-access=subscription }}</ref> Narwhals drown if open water is no longer accessible and ice is too thick for them to break through. Breathing holes in ice may be up to {{convert|1450|m|ft|-1|abbr=on}} apart, which limits the use of foraging grounds. These holes must be at least {{convert|0.5|m|ft|abbr=on}} wide to allow an adult whale to breathe.<ref name=":8">{{Cite journal |last1=Williams |first1=Terrie M. |last2=Noren |first2=Shawn R. |last3=Glenn |first3=Mike |date=April 2011 |title=Extreme physiological adaptations as predictors of climate-change sensitivity in the narwhal (''Monodon monoceros'') |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.2010.00408.x |journal=Marine Mammal Science |language=en |volume=27 |issue=2 |pages=334–349 |bibcode=2011MMamS..27..334W |doi=10.1111/j.1748-7692.2010.00408.x |issn=0824-0469|url-access=subscription }}</ref> Narwhals also die of [[starvation]] from entrapment events.<ref name=":21" />

In 1914{{endash}}1915, around 1,000 narwhal carcasses were discovered after entrapment events, most occurring in areas such as [[Disko Bay]] in [[West Greenland]].<ref>{{Cite journal |last=Porsild |first=Morten P. |date=1918 |title=On 'savssats': a crowding of Arctic animals at holes in the sea ice |url=https://www.jstor.org/stable/207815 |journal=Geographical Review |volume=6 |issue=3 |pages=215–228 |bibcode=1918GeoRv...6..215P |doi=10.2307/207815 |issn=0016-7428 |jstor=207815|url-access=subscription }}</ref> Several cases of sea entrapment were recorded in 2008–2010, during the Arctic winter, including in some places where such events had never been recorded before.<ref name=":7" /> This suggests later departure dates from summering grounds. Wind and currents move sea ice from adjacent locations to Greenland, leading to fluctuations in concentration. Due to their tendency of returning to the same areas, changes in weather and ice conditions are not always associated with narwhal movement toward open water. It is currently unclear to what extent sea ice changes pose a danger to narwhals.<ref name=":18" /><ref name=":7" /><ref>{{Cite book |last1=Macdonald |first1=David Whyte |url=https://books.google.com/books?id=rdRFAAAAYAAJ |title=Mammals of Britain & Europe |last2=Barrett |first2=Priscilla |date=1993 |publisher=HarperCollins |isbn=978-0-00-219779-3 |pages=173 |language=en}}</ref>

Narwhals are preyed upon by [[polar bear]]s and [[orca]]s. In some instances, the former have been recorded waiting at breathing holes for young narwhals, while the latter were observed surrounding and killing entire narwhal pods.<ref name="Macdonald" /><ref>{{Cite book |url=https://books.google.com/books?id=2rkHQpToi9sC&q=narwhals+attacked+by+polar+bears&pg=PA929 |title=Encyclopedia of Marine Mammals |publisher=Academic Press |year=2009 |isbn=978-0-08-091993-5 |editor-last=Perrin, William F. |pages=929–930 |access-date=18 November 2020 |editor-last2=Wursig, Bernd |editor-last3=Thewissen, J. G. M. 'Hans' |archive-url=https://web.archive.org/web/20240128092123/https://books.google.com/books?id=2rkHQpToi9sC&q=narwhals+attacked+by+polar+bears&pg=PA929#v=snippet&q=narwhals%20attacked%20by%20polar%20bears&f=false |archive-date=28 January 2024 |url-status=live}}</ref><ref>{{Cite journal |last1=Ferguson |first1=Steven H. |last2=Higdon |first2=Jeff W. |last3=Westdal |first3=Kristin H. |date=30 January 2012 |title=Prey items and predation behavior of killer whales (''Orcinus orca'') in Nunavut, Canada based on Inuit hunter interviews |journal=Aquatic Biosystems |volume=8 |issue=1 |pages=3 |bibcode=2012AqBio...8....3F |doi=10.1186/2046-9063-8-3 |issn=2046-9063 |pmc=3310332 |pmid=22520955 |doi-access=free}}</ref><ref>{{Cite web |date=19 November 2014 |title=Invasion of the killer whales: killer whales attack pod of narwhal |url=https://www.pbs.org/wnet/nature/invasion-killer-whales-killer-whales-attack-pod-narwhals/11165/ |url-status=live |archive-url=https://web.archive.org/web/20161022071130/http://www.pbs.org/wnet/nature/invasion-killer-whales-killer-whales-attack-pod-narwhals/11165/ |archive-date=22 October 2016 |access-date=23 October 2016 |publisher=Public Broadcasting System}}</ref> To escape predators such as orcas, narwhals may use prolonged submersion to hide under [[ice floe]]s rather than relying on speed.<ref name=":8" />

Researchers found bacteria of the ''[[Brucella]]'' genus in the bloodstreams of numerous narwhals throughout the course of a 19-year study. They were also recorded with [[whale lice]] species such as ''[[Cyamus monodontis]]'' and ''[[Cyamus nodosus]]''. Other [[pathogen]]s that affect narwhals include ''[[Toxoplasma gondii]]'', [[morbillivirus]], and [[papillomavirus]].<ref>{{Cite journal |last1=Barratclough |first1=Ashley |last2=Ferguson |first2=Steven H. |last3=Lydersen |first3=Christian |last4=Thomas |first4=Peter O. |last5=Kovacs |first5=Kit M. |date=July 2023 |title=A review of circumpolar Arctic marine mammal health—a call to action in a time of rapid environmental change |journal=Pathogens |language=en |volume=12 |issue=7 |pages=937 |doi=10.3390/pathogens12070937 |issn=2076-0817 |pmc=10385039 |pmid=37513784 |doi-access=free}}</ref> In 2018, a female narwhal was recorded with an [[alphaherpesvirus]] in her system.<ref>{{Cite journal |last1=Nielsen |first1=Ole |last2=Rodrigues |first2=Thaís C. S. |last3=Marcoux |first3=Marianne |last4=Béland |first4=Karine |last5=Subramaniam |first5=Kuttichantran |last6=Lair |first6=Stéphane |last7=Hussey |first7=Nigel E. |last8=Waltzek |first8=Thomas B. |date=6 July 2023 |title=Alphaherpesvirus infection in a free-ranging narwhal (''Monodon monoceros'') from Arctic Canada |url=https://www.int-res.com/abstracts/dao/v154/p131-139/ |journal=Diseases of Aquatic Organisms |language=en |volume=154 |pages=131–139 |doi=10.3354/dao03732 |issn=0177-5103 |pmid=37410432 |doi-access=free}}</ref>