Use of stable isotopes to determine diets of living and extinct bears

1996 ◽  
Vol 74 (11) ◽  
pp. 2080-2088 ◽  
Author(s):  
G. V. Hilderbrand ◽  
S. D. Farley ◽  
C. T. Robbins ◽  
T. A. Hanley ◽  
K. Titus ◽  
...  
Keyword(s):  
Ursus Arctos ◽  
Isotopic Fractionation ◽  
Columbia River ◽  
Late Summer ◽  
Isotopic Signature ◽  
Grizzly Bears ◽  
Brown Bears ◽  
River Drainage ◽  
Carbon And Nitrogen ◽  
Isotopic Analyses

The potential use of stable-isotope analyses (δ13C and δ15N) to estimate bear diets was assessed in 40-day feeding trials using American black bears (Ursus americanus). Bear plasma and red blood cells have half-lives of ~4 days and ~28 days, respectively. The isotopic signature of bear plasma is linearly related to that of the diet, and with the exception of adipose tissue, there is no isotopic fractionation across bear tissues. Isotopic analyses were used to estimate the diets of three bear populations: Pleistocene cave bears (U. speleaus) in Europe, grizzly bears (Ursus arctos horribilis) inhabiting the Columbia River drainage prior to 1931, and brown bears (U. arctos) of Chichagof and Admiralty islands, Alaska. Cave bears were omnivores with terrestrially produced meat contributing from 41 to 78% (58 ± 14%) of their metabolized carbon and nitrogen. Salmon contributed from 33 to 90% (58 ± 23%) of the metabolized carbon and nitrogen in grizzly bears from the Columbia River drainage. Finally, most brown bears on Chichagof and Admiralty islands feed upon salmon during the late summer and fall; however, a subpopulation of bears exists that does not utilize salmon.

scholarly journals Quantifying N<sub>2</sub>O reduction to N<sub>2</sub> based on N<sub>2</sub>O isotopocules – validation with independent methods (helium incubation and <sup>15</sup>N gas flux method)

2017 ◽  
Vol 14 (3) ◽  
pp. 711-732 ◽  
Author(s):  
Dominika Lewicka-Szczebak ◽  
Jürgen Augustin ◽  
Anette Giesemann ◽  
Reinhard Well
Keyword(s):  
Isotopic Fractionation ◽  
Isotopic Signature ◽  
Residual Fraction ◽  
Simultaneous Estimation ◽  
Site Preference ◽  
Isotopic Enrichment ◽  
Flux Method ◽  
Gas Flux ◽  
Isotopic Analyses

Abstract. Stable isotopic analyses of soil-emitted N2O (δ15Nbulk, δ18O and δ15Nsp = 15N site preference within the linear N2O molecule) may help to quantify N2O reduction to N2, an important but rarely quantified process in the soil nitrogen cycle. The N2O residual fraction (remaining unreduced N2O, rN2O) can be theoretically calculated from the measured isotopic enrichment of the residual N2O. However, various N2O-producing pathways may also influence the N2O isotopic signatures, and hence complicate the application of this isotopic fractionation approach. Here this approach was tested based on laboratory soil incubations with two different soil types, applying two reference methods for quantification of rN2O: helium incubation with direct measurement of N2 flux and the 15N gas flux method. This allowed a comparison of the measured rN2O values with the ones calculated based on isotopic enrichment of residual N2O. The results indicate that the performance of the N2O isotopic fractionation approach is related to the accompanying N2O and N2 source processes and the most critical is the determination of the initial isotopic signature of N2O before reduction (δ0). We show that δ0 can be well determined experimentally if stable in time and then successfully applied for determination of rN2O based on δ15Nsp values. Much more problematic to deal with are temporal changes of δ0 values leading to failure of the approach based on δ15Nsp values only. For this case, we propose here a dual N2O isotopocule mapping approach, where calculations are based on the relation between δ18O and δ15Nsp values. This allows for the simultaneous estimation of the N2O-producing pathways' contribution and the rN2O value.

Bears napping nearby: daybed selection by brown bears (Ursus arctos) in a human-dominated landscape

2018 ◽  
Vol 96 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Michaela Skuban ◽  
Slavomír Find’o ◽  
Matúš Kajba
Keyword(s):  
Ursus Arctos ◽  
Late Summer ◽  
Fruit Trees ◽  
Early Summer ◽  
Adult Males ◽  
Human Settlements ◽  
Activity Data ◽  
Brown Bears ◽  
North Central ◽  
Linear Mixed Effects

Daybeds are essential for the survival of brown bears (Ursus arctos L., 1758) and may represent a population-limiting resource in human-dominated landscapes. In this study, we demonstrate which land-cover types and bear characteristics affect daybed selection in north-central Slovakia. We used the positional and activity data of 21 bears acquired by GPS–GSM telemetry to identify 3864 daybeds. By use of K-select analysis and linear mixed-effects modelling, we explored how bears chose these places for their daytime resting. The most important drivers for daybed selection were the presence of dense regenerating forests and forest–shrubbery belts in farmland. Bears avoided resting in older forests without suitable undergrowth. Females selected daybeds differently depending on the presence of dependent cubs. During spring – early summer, females with cubs of the year avoided other bears by selecting more rugged terrain. These females also selected daybeds significantly closer to human settlements than adult males, possibly to avoid the risk of infanticide. In late summer – autumn, all bears selected daybeds closer to human settlements than in spring, probably because they were attracted by maize (Zea mays) fields and fruit trees. Many daybeds were located outside protected areas in farmland closer to people, which could increase bear–human conflicts.

Seasonal occurrence, body composition, and migration potential of army cutworm moths in northwest Montana

1998 ◽  
Vol 76 (5) ◽  
pp. 835-842 ◽  
Author(s):  
Don White, Jr. ◽  
Katherine C Kendall ◽  
Harold D Picton
Keyword(s):  
Body Mass ◽  
Great Plains ◽  
Ursus Arctos ◽  
Late Summer ◽  
Grizzly Bears ◽  
Cost Of Transport ◽  
Alpine Zone ◽  
Migration Potential ◽  
Gross Energy ◽  
And Migration

Grizzly bears (Ursus arctos horribilis) consume adult army cutworm moths (Euxoa auxiliaris) from late June through mid-September on alpine talus slopes in Glacier National Park (GNP), Montana. As part of a study carried out to better understand the ecological interactions between grizzly bears and army cutworm moths in GNP, we studied temporal abundance patterns, body mass and composition, and migration potential of moths collected from alpine moth aggregation sites throughout the summer of 1994 and 1995. Army cutworm moths arrived in the alpine zone of GNP in late June or early July and departed by late August or early September. While moths were in the alpine zone, their body mass and moisture, lipid, and gross energy contents markedly increased and crude protein decreased. The absence of moths from the alpine zone coincided with the presence of moths on the Great Plains. Using published estimates of the cost of transport in flying animals, we calculated that an army cutworm moth flying in late summer through still air could fly 140 km using body lipid reserves alone.

Major components of grizzly bear diet across North America

2006 ◽  
Vol 84 (3) ◽  
pp. 473-489 ◽  
Author(s):  
Garth Mowat ◽  
Douglas C Heard
Keyword(s):  
British Columbia ◽  
North America ◽  
Rangifer Tarandus ◽  
Ursus Arctos ◽  
Nitrogen Isotope ◽  
Grizzly Bears ◽  
Grizzly Bear ◽  
Carbon And Nitrogen ◽  
Skull Size ◽  
Meat Diet

We measured stable carbon and nitrogen isotope ratios in guard hair of 81 populations of grizzly bears (Ursus arctos L., 1758) across North America and used mixing models to assign diet fractions of salmon, meat derived from terrestrial sources, kokanee (Oncorhynchus nerka (Walbaum in Artedi, 1792)), and plants. In addition, we examined the relationship between skull size and diet of bears killed by people in British Columbia. The majority of carbon and nitrogen assimilated by most coastal grizzly bear populations was derived from salmon, while interior populations usually derived a much smaller fraction of their nutrients from salmon, even in areas with relatively large salmon runs. Terrestrial prey was a large part of the diet where ungulates were abundant, with the highest fractions observed in the central Arctic, where caribou (Rangifer tarandus (L., 1758)) were very abundant. Bears in some boreal areas, where moose (Alces alces (L., 1758)) were abundant, also ate a lot of meat. Bears in dryer areas with low snowfall tended to have relatively high meat diet fractions, presumably because ungulates are more abundant in such environments. Kokanee were an important food in central British Columbia. In areas where meat was more than about a third of the diet, males and females had similar meat diet fractions, but where meat was a smaller portion of the diet, males usually had higher meat diet fractions than females. Females reached 95% of their average adult skull length by 5 years of age, while males took 8 years. Skull width of male grizzly bears increased throughout life, while this trend was slight in females. Skull size increased with the amount of salmon in the diet, but the influence of terrestrial meat on size was inconclusive. We suggest that the amount of salmon in the diet is functionally related to fitness in grizzly bears.

Diet reconstruction of ancient brown bears (Ursus arctos) from Mont Ventoux (France) using bone collagen stable isotope biogeochemistry (13C, 15N)

2004 ◽  
Vol 82 (4) ◽  
pp. 576-586 ◽  
Author(s):  
Hervé Bocherens ◽  
Alain Argant ◽  
Jacqueline Argant ◽  
Daniel Billiou ◽  
Evelyne Crégut-Bonnoure ◽  
...  
Keyword(s):  
Ursus Arctos ◽  
Bone Collagen ◽  
Isotopic Data ◽  
Brown Bears ◽  
Diet Reconstruction ◽  
Carbon And Nitrogen ◽  
Open Environment ◽  
Food Items ◽  
Nitrogen Isotopic Composition ◽  
Isotopic Variations

A very rich assemblage of ancient brown bears (Ursus arctos arctos Linnaeus, 1758) from Mont Ventoux caves (France) has been investigated using carbon and nitrogen isotopic composition of bone collagen. The isotopic data showed that these bears were feeding in an open environment and consumed mainly plant food items. The access to livestock meat appeared to have been much more limited for these ancient brown bears than for 20th-century Pyrenean bears, suggesting that husbandry patterns had kept bears away from domestic herds. The isotopic variations observed are large according to the ontogenic stage of the bears when they died, which could be accounted for by the isotopic changes that occur during hibernation of the lactating female bear and by different time periods averaged in bone collagen, and without the need to involve different food resources for cubs relative to adult bears.

Estimating population growth of grizzly bears from the Flathead River drainage using computer simulations of reproduction and survival rates

1996 ◽  
Vol 74 (8) ◽  
pp. 1409-1416 ◽  
Author(s):  
Frederick W. Hovey ◽  
Bruce N. McLellan
Keyword(s):  
Ursus Arctos ◽  
Survival Rates ◽  
Population Increase ◽  
Grizzly Bears ◽  
Grizzly Bear ◽  
Reproduction Rate ◽  
River Drainage ◽  
The North ◽  
Flathead River ◽  
Subadult Female

Using survival and reproduction data obtained from radio-tracking 23 adult female, 24 subadult female, 49 yearling, and 44 cub grizzly bears (Ursus arctos) in the Flathead River drainage of British Columbia and Montana, we estimated the finite rate of population increase [Formula: see text] from 1979 to 1994 at 1.085 ± 0.026, with ≈95% confidence limits of 1.032–1.136. Estimated annual survival rates were 0.946 ± 0.026 for adult females, 0.931 ± 0.038 for subadult females, 0.944 ± 0.039 for yearlings, and 0.867 ± 0.050 for cubs (rates for cubs and yearlings represented both sexes). The estimated annual reproduction rate and age at first parturition were 0.422 ± 0.042 female cubs per female and 6.44 ± 0.45 years, respectively. We found that uncertainty in [Formula: see text] was mostly attributable to uncertainty in survival rates (76.7%), with subadult (47.5%) and adult (21.9%) survival contributing the largest portions. These results indicated that to reduce uncertainty in [Formula: see text], further research on grizzly bears in our study area should focus on improving estimates of adult and subadult female survivorship. Other demographic variables are not as important in estimating the grizzly bear population trend in the North Fork of the Flathead River drainage.

Hair structure of brown bears (Ursus arctos L.) from North America and Scandinavia

1991 ◽  
Vol 69 (9) ◽  
pp. 2404-2409 ◽  
Author(s):  
K. Elgmork ◽  
H. Riiser
Keyword(s):  
United States ◽  
North America ◽  
Ursus Arctos ◽  
Age Groups ◽  
Significant Negative Correlation ◽  
Hair Shaft ◽  
The Body ◽  
Grizzly Bears ◽  
Brown Bears ◽  
Hair Diameter

Analysis of measurements of guard hairs from North American brown or grizzly bears and Scandinavian brown bears (Ursus arctos L.) showed variation over the body and along the hair shaft. Using the medullary index, i.e., the medullary diameter as a percentage of the hair diameter, comparisons were made among body areas, age groups, geographical areas, sexes, and seasons. Statistically significant differences were found among body areas. Hairs from the foreleg were shorter and wider, with a smaller medullary index than those from other body areas. There was a weak but statistically significant negative correlation between the medullary index and age of individuals. Medullary indices from Scandinavian bears were significantly greater than those from Alaskan bears, which in turn were greater than those from bears of the contiguous United States. There were no statistically significant differences between the medullary index and sex or season.

scholarly journals Isotopic fractionation of N<sub>2</sub>O to quantify N<sub>2</sub>O reduction to N<sub>2</sub> – validation with Helium incubation and <sup>15</sup>N gas flux methods

2016 ◽  
Author(s):  
Dominika Lewicka-Szczebak ◽  
Jürgen Augustin ◽  
Anette Giesemann ◽  
Reinhard Well
Keyword(s):  
Isotopic Fractionation ◽  
Isotopic Signature ◽  
Residual Fraction ◽  
Simultaneous Estimation ◽  
Site Preference ◽  
Isotopic Enrichment ◽  
Gas Flux ◽  
Isotopic Signatures ◽  
Isotopic Analyses

Abstract. Stable isotopic analyses of soil-emitted N2O (δ15Nbulk, δ18O and δ15Nsp = 15N site preference within the linear N2O molecule) may help to quantify N2O reduction to N2, a main unknown magnitude in the soil nitrogen cycling. The N2O residual fraction (rN2O) can be theoretically calculated from the measured isotopic enrichment of the residual N2O. However, various N2O producing pathways may also influence the N2O isotopic signatures, and hence complicate the application of this isotopic fractionation approach. Here this approach was tested based on laboratory soil incubations with two different soil types applying two reference methods for quantification of rN2O: Helium incubation with direct measurement of N2 flux and the 15N gas flux method. This allowed a comparison of the measured rN2O values with the ones calculated based on isotopic enrichment of residual N2O. The results indicate that the performance of the N2O isotopic fractionation approach is related with the accompanying N2O and N2 source processes and the most critical is the determination of the initial isotopic signature of N2O before reduction (δ0). We show that δ0 can be well experimentally determined if stable in time and successfully applied for determination of rN2O based on δ15Nsp values. Much more problematic is to deal with temporal changes of δ0 values leading to failure of the approach based on δ15Nsp values only. For this case we propose here a dual N2O isotopocule mapping approach, where calculations are based on the relation between δ18O and δ15Nsp values. This allows for the simultaneous estimation of the N2O producing pathways contribution and the rN2O value.

scholarly journals Cortisol levels in blood and hair of unanesthetized grizzly bears ( Ursus arctos ) following intravenous cosyntropin injection

2021 ◽  
Author(s):  
Marc Cattet ◽  
David M. Janz ◽  
Luciene Kapronczai ◽  
Joy A. Erlenbach ◽  
Heiko T. Jansen ◽  
...  
Keyword(s):  
Ursus Arctos ◽  
Grizzly Bears ◽  
Cortisol Levels
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