Life history parameters of narwhals (<i>Monodon monoceros</i>) from Greenland

Garde, Eva; Hansen, Steen Honoré; Ditlevsen, Susanne; Tvermosegaard, Ketil Biering; Hansen, Júlia; Hårding, Karin C.; Heide‐Jørgensen, Mads Peter

doi:10.1093/jmammal/gyv110

Cited by 38 publications

(45 citation statements)

References 27 publications

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“…Records of the only close relative of the narwhal, the beluga whale, outside its natural range originate in a number of cases also from rivers or estuaries (Gewalt, 1967;De Smet, 1974, 1981Van Gompel, 1991;Camphuysen & Peet, 2006). The Bornem animal was a juvenile, likely around 5 (95% CI: 2 to 11 y) to 6 (95% CI: 2 to 13 y) y old, applying the von Bertalanffy growth model as presented by Garde et al (2015) for East and West Greenland, respectively. The animal was sexually immature.…”

Section: Discussionmentioning

confidence: 99%

“…The animal was sexually immature. Hay (1984) estimated sexual and physical maturity at 395 and 470 cm, respectively, for males; and Garde et al (2015) estimated a length of 350 to 400 cm for sexual maturity in East and West Greenland animals, and physical maturity at 462 and 456 cm for East and West Greenland animals, respectively. Applying the regression curve for tusk length vs body length from Garde et al (2015), it is apparent that the tusk of the Bornem animal was relatively long.…”

Section: Discussionmentioning

confidence: 99%

“…Hay (1984) estimated sexual and physical maturity at 395 and 470 cm, respectively, for males; and Garde et al (2015) estimated a length of 350 to 400 cm for sexual maturity in East and West Greenland animals, and physical maturity at 462 and 456 cm for East and West Greenland animals, respectively. Applying the regression curve for tusk length vs body length from Garde et al (2015), it is apparent that the tusk of the Bornem animal was relatively long. A male of 5 y old (based on dentinal growth layer groups [GLGs] with one GLG assumed to constitute 1 y of growth) with a body length of 306 cm had a much shorter tusk (external tusk length of 13 cm; total tusk length of 34 cm), while an animal with an unknown length, but with a total tusk length (external tusk length of 62 cm; tusk length of 91.5 cm) similar to the one of the animal of Bornem, had 17 GLGs (Garde et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

“…They may have been traces of injuries sustained while swimming upside down close to the seabed (Dietz et al, 2007), through contact with ice during temporary ice entrapment (HeideJørgensen et al, 2002b; as reported in Huntington et al, 1999, for beluga whale), through failed predation attempts by killer whale (Orcinus orca) or polar bear (Ursus maritimus) (Hay & Mansfield, Fraser, 1974 1989; Reeves et al, 1994), or through intraspecific aggressive behaviour, although this is more typical in adult males (Silverman & Dunbar, 1980;Gerson & Hickie, 1985). Applying the Gompertz body mass growth model for West Greenland narwhal in Garde et al (2015), the mass of a 5-y-old narwhal would be 447 kg. Applying the equation of Hay (1984) for body mass from length measurements, a narwhal of 3.04 m would weigh 464 kg; therefore, as the Bornem animal was complete, it would have been around 150 kg underweight, although some weight loss due to dehydration and during decomposition may have occurred.…”

Section: Discussionmentioning

confidence: 99%

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New Extralimital Record of a Narwhal (Monodon monoceros) in Europe

et al. 2018

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On 27 April 2016, a dead narwhal (Monodon monoceros) was found on the bank of the River Scheldt, Belgium. It was the first record of this high Arctic cetacean in Belgium, and one of the most southerly records ever in Europe. Due to the decomposition of the carcass, the results of the autopsy remained inconclusive, but it is likely that the animal had died due to a long process of starvation. In the stomach, a large number of litter items were found which were probably ingested during the process of dying. We further provide information on the sighting of the live animal prior to the stranding and present an overview of the very few known records of narwhal in northwestern Europe.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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New Extralimital Record of a Narwhal (Monodon monoceros) in Europe

et al. 2018

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“…Known ages were regressed against individual ratios of (eq. (1); Garde et al 2015). The ages from the 35 goats were not known exactly and the uncertainty (as standard deviation) differed between goats (Appendix 1) thus weighted regressions were used.…”

Section: The Pygmy Goatmentioning

confidence: 99%

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

et al. 2018

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The aspartic acid racemization (AAR) technique has been applied for age estimation of humans and other mammals for more than four decades. In this study, eye lenses from 124 animals representing 25 mammalian species were collected and D/L ratios obtained using the AAR technique. The animals were either of known age or had the age estimated by other methods. The purpose of the study was to: a) estimate the accuracy of the AAR technique, and b) examine the effect of body temperature on racemization rates. Samples from four of the 25 species covered the range of ages that is needed to estimate speciesspecific racemization rates. The sample size from a single species of known age, the pygmy goat (Capra hircus, n = 35), was also large enough to investigate the accuracy of ages obtained using the AAR technique. The 35 goats were divided into three datasets: all goats (n = 35), goats >0.5 yrs old (n = 26) and goats >2 yrs old (n = 19). Leave-one-out analyses were performed on the three sets of data. Normalized root mean squared errors for the group of goats >0.5 yrs old were found to be the smallest. The higher variation in D/L measurements found for young goats <0.5 yrs can probably be explained by a period of continued postnatal growth of the eye lens. Normalized root mean squared errors from the leave-one-out cross-validation analyses based on goats >0.5 yrs old was for three age groups of the goats: 0.934 yrs for young goats <2 yrs (n = 16), 0.102 yrs for adult goats from 2-8 yrs (n = 15) and 0.133 yrs for old goats >8 yrs (n = 4). Thus, the age of an adult or an old animal can be predicted with approximately 10% accuracy, whereas the age of a NAMMCO Scientific Publications, Volume 10 young animal is difficult to predict. A goat specific racemization rate, as a 2k Asp value, was estimated to 0.0107 ± 3.8 x 10 -4 SE (n = 26). The 2k Asp values from 12 species, four estimated in this study and another eight published, were used to examine the effect of core body temperature on the rate of racemization. A positive relationship between AAR and temperature was found (r 2 = 0.321) but results also suggest that other factors besides temperature are involved in the racemization process in living animals. Based on our results we emphasize that non-species-specific racemization rates should be used with care in AAR age estimation studies and that the period of postnatal growth of the eye lens be considered when estimating species-specific D/L 0 values and ages of young individuals.

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Hierarchical Classification of Narwhal Subpopulations Using Social Distance

et al. 2019

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Effective wildlife management and conservation require knowledge of distribution, sex composition, and age structure of a population. We explored the distribution of the Baffin Bay narwhal (Monodon monoceros) population in August 2013 by documenting sex and age distribution across the Canadian Arctic Archipelago covering 2,317,152 km2. For 6,314 narwhals identified in 3,393 aerial images taken across the Eastern Canadian Arctic, we calculated a matrix of swimming distances between all individuals. We then used a quantitative clustering approach to partition our dataset (partitioning around the medoids). The clusters obtained from the analysis supported the delimitation of the 5 narwhal management stocks currently used by the Department of Fisheries and Oceans but did not support the hypothesized division of Jones Sound and Smith Sound stocks. Across the 5 clusters, male:female ratios varied between 0.72 and 1.44 and the proportion of newborns relative to the number of females varied between 0.07 and 0.18. As a highly detailed snapshot of narwhal distribution across a very large region, our study is a step toward better documentation of the basic population information required for stock assessment, sustainable harvest, and habitat protection of narwhals in an era of rapid Arctic change. © 2019 The Wildlife Society.

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Life history parameters of narwhals (Monodon monoceros) from Greenland

Cited by 38 publications

References 27 publications

New Extralimital Record of a Narwhal (Monodon monoceros) in Europe

New Extralimital Record of a Narwhal (Monodon monoceros) in Europe

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

Hierarchical Classification of Narwhal Subpopulations Using Social Distance

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