Editing Narwhal (section)

=== 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}}</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>