Postnatal growth in body length and mass of polar bears (<i>Ursus maritimus</i>) at Svalbard

Derocher, Andrew E.; Wiig, Øystein

doi:10.1017/s0952836902000377

Cited by 141 publications

(73 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, it is possible to estimate body masses for extant animals with reasonable precision since detailed information is often available in the literature relating body mass to specific linear body dimensions. We measured appropriate dimensions (shoulder height for most species but femur length for Cervus elaphus and body length for Ursus maritimus) directly from the point clouds and calculated the predicted body mass based on literature derived scaling equations [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. In most cases, there was good information available but the values for Dicerorhinus sumatrensis, Megaloceros giganteus and Tapirus indicus are somewhat less reliable since no systematic assessment of body mass and dimensions could be found.…”

Section: Methodsmentioning

confidence: 99%

Minimum convex hull mass estimations of complete mounted skeletons

et al. 2012

View full text Add to dashboard Cite

Body mass is a critical parameter used to constrain biomechanical and physiological traits of organisms. Volumetric methods are becoming more common as techniques for estimating the body masses of fossil vertebrates. However, they are often accused of excessive subjective input when estimating the thickness of missing soft tissue. Here, we demonstrate an alternative approach where a minimum convex hull is derived mathematically from the point cloud generated by laser-scanning mounted skeletons. This has the advantage of requiring minimal user intervention and is thus more objective and far quicker. We test this method on 14 relatively large-bodied mammalian skeletons and demonstrate that it consistently underestimates body mass by 21 per cent with minimal scatter around the regression line. We therefore suggest that it is a robust method of estimating body mass where a mounted skeletal reconstruction is available and demonstrate its usage to predict the body mass of one of the largest, relatively complete sauropod dinosaurs: Giraffatitan brancai (previously Brachiosaurus ) as 23200 kg.

show abstract

Section: Methodsmentioning

confidence: 99%

Minimum convex hull mass estimations of complete mounted skeletons

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Standard body measurements (standard length and axillary girth) were taken and total body mass was estimated using the approach by Derocher & Wiig [26]. Field estimates of age and reproductive status were recorded.…”

Section: (B) Field Methodsmentioning

confidence: 99%

Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears ( Ursus maritimus )

et al. 2013

View full text Add to dashboard Cite

Intraspecific differences in movement behaviour reflect different tactics used by individuals or sexes to favour strategies that maximize fitness. We report movement data collected from n ¼ 23 adult male polar bears with novel ear-attached transmitters in two separate pack ice subpopulations over five breeding seasons. We compared movements with n ¼ 26 concurrently tagged adult females, and analysed velocities, movement tortuosity, range sizes and habitat selection with respect to sex, reproductive status and body mass. There were no differences in 4-day displacements or sea ice habitat selection for sex or population. By contrast, adult females in all years and both populations had significantly more linear movements and significantly larger breeding range sizes than males. We hypothesized that differences were related to encounter rates, and used observed movement metrics to parametrize a simulation model of male-male and malefemale encounter. The simulation showed that the more tortuous movement of males leads to significantly longer times to male-male encounter, while having little impact on male-female encounter. By contrast, linear movements of females are consistent with a prioritized search for sparsely distributed prey. These results suggest a possible mechanism for explaining the smaller breeding range sizes of some solitary male carnivores compared to females.

show abstract

“…As one female could not be weighed, we estimated its body mass using morphometric measurements (i.e., axillary girth and dorsal straight-line body length) following Derocher and Wiig (2002). For all females, dorsal straight-line body length (SL) measures the straight line above the bear (lying in sternal recumbency) from the tip of the nose to the tip of the last tail vertebra.…”

Section: Field Samplingmentioning

confidence: 99%

Potentiation of ecological factors on the disruption of thyroid hormones by organo-halogenated contaminants in female polar bears (Ursus maritimus) from the Barents Sea

Bourgeon

Riemer

Tartu

et al. 2017

Environmental Research

View full text Add to dashboard Cite

As apex predators, polar bears (Ursus maritimus) are among the most heavily polluted organisms in the Arctic. In addition to this anthropogenic stressor, climate warming has been shown to negatively affect their body condition, reproductive output and survival. Among potential underlying physiological mechanisms, thyroid hormones (THs), which control thermoregulation, metabolism and reproduction, can be affected by a variety of both natural and anthropogenic factors. While THs have been extensively used as proxies for pollution exposure in mammals, including polar bears, there is a lack of knowledge of their natural variations. In this context, we examined seasonal variations in body condition and circulating TH concentrations in free-ranging female polar bears. Females with variable reproductive status (i.e., solitary, with cubs of the year or with yearlings) were sampled from locations with contrasted sea ice conditions. Furthermore, we studied THs in relation to levels of organohalogenated contaminants. As predicted, solitary females were in better condition than females caring for offspring, especially in spring. In addition, TH levels were lower in autumn compared to spring, although this seasonal effect was mainly observed in solitary females.Finally, the negative relationships between organochlorine and perfluoroalkyl substances and some THs suggest a possible alteration of homeostasis of THs. Since the latter relationships were only observed during spring, we emphasize the importance of considering the ecological factors when using THs as proxies for pollution exposure. Yet, the combined effects of natural and anthropogenic stressors on THs might impair the ability of polar bears to adapt to ongoing climate changes.

show abstract

Postnatal growth in body length and mass of polar bears (Ursus maritimus) at Svalbard

Cited by 141 publications

References 31 publications

Minimum convex hull mass estimations of complete mounted skeletons

Minimum convex hull mass estimations of complete mounted skeletons

Females roam while males patrol: divergence in breeding season movements of pack-ice polar bears ( Ursus maritimus )

Potentiation of ecological factors on the disruption of thyroid hormones by organo-halogenated contaminants in female polar bears (Ursus maritimus) from the Barents Sea

Contact Info

Product

Resources

About