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Marine Ecology Progress Series

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MEPS 668:163-175 (2021)  -  DOI:

Ontogenetic profiles of dentine isotopes (δ15N and δ13C) reveal variable narwhal Monodon monoceros nursing duration

Shu-Ting Zhao1,2,*, Cory J. D. Matthews1,2, Gail K. Davoren1, Steven H. Ferguson1,2, Cortney A. Watt1,2

1Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
2Fisheries and Oceans Canada, Winnipeg, Manitoba R3T 2N6, Canada
*Corresponding author:

ABSTRACT: Stable isotope analysis (SIA) of sequential dentine growth layer groups can be used to estimate the lifetime diet of individuals and infer major ontogenetic shifts such as the completion of nursing. We used SIA of dentine from narwhal Monodon monoceros embedded canine teeth to investigate ontogenetic dietary patterns, with a focus on nursing duration. We also determined whether nursing duration differed between sexes and between 2 periods during which narwhals may have undergone dietary shifts due to warming. Embedded teeth from both sexes were collected near Pond Inlet, Nunavut, Canada, in 1982 and 1983 (n = 17) and 2015 and 2017 (n = 14). Nursing duration ranged from ~2 to ~6 yr, with 60% of narwhals being nursed beyond the previously published estimate of <2 yr. The proportion of individuals nursed <2 yr versus >2 yr did not differ between sexes or periods. This study not only revealed that narwhals vary extensively in their nursing duration, but also indicated that extended nursing (>2 yr) with gradual introduction of solid food over this period was common. These findings provide insights into narwhal life-history strategies, as extended nursing may be another feature of a long-lived, slow-reproducing mammal adapted to unique polar conditions that are threatened by global warming.

KEY WORDS: Nursing duration · Narwhal · Growth layer groups · Stable nitrogen isotopes · Teeth · Weaning

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Cite this article as: Zhao ST, Matthews CJD, Davoren GK, Ferguson SH, Watt CA (2021) Ontogenetic profiles of dentine isotopes (δ15N and δ13C) reveal variable narwhal Monodon monoceros nursing duration. Mar Ecol Prog Ser 668:163-175.

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