Denning Ecology of Brown Bears on Admiralty and Chichagof Islands

Schoen, John W.; Beier, LaVern R.; Lentfer, Jack W.; Johnson, Luke

doi:10.2307/3872636

Cited by 36 publications

(63 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Brown bears in our study areas usually den at high elevations with females entering their dens earlier (late October) and emerging later (mid-May) than males (Schoen et al 1987). After emergence from dens bears travel to lower elevations in late April and May and begin feeding on new growth vegetation, often in estuaries, grass flats and muskegs.…”

Section: Brown Bears In the Alexander Archipelagomentioning

confidence: 94%

Consumption of salmon by Alaskan brown bears: a trade-off between nutritional requirements and the risk of infanticide?

2004

Self Cite

View full text Add to dashboard Cite

The risk of infanticide may alter foraging decisions made by females, which otherwise would have been based on nutritional requirements and forage quality and availability. In systems where meat resources are spatially aggregated in late summer and fall, female brown bears (Ursus arctos) would be faced with a trade-off situation. The need of reproductive females to accumulate adequate fat stores would likely result in a decision to frequent salmon streams and consume the protein- and lipid-rich spawning salmon. In contrast, aggregations of bears along salmon streams would create conditions of high risk of infanticide. We investigated consumption of salmon by brown bears on Admiralty and Chichagof Islands in Southeast Alaska from 1982 to 2000 using stable isotope analysis and radiotelemetry. While nearly all males (22 of 23) consumed relatively large amounts of salmon (i.e., >10% relative contribution to seasonal diet), not all females (n=56) did so. Five of 26 females for which we had reproductive data, occupied home ranges that had no access to salmon and thus did not consume salmon when they were mated or accompanied by young. Of females that had access to salmon streams (n=21), all mated individuals (n=16) had delta(15)N values indicative of salmon consumption. In contrast, 4 out of 16 females with cubs avoided consuming salmon altogether, and of the other 12, 3 consumed less salmon than they did when they were mated. For 11 of 21 females with access to salmon streams we had data encompassing both reproductive states. Five of those altered foraging strategies and exhibited significantly lower values of delta(15)N when accompanied by young than when mated, while 6 did not. Radiotelemetry data indicated that females with spring cubs were found, on average, further away from streams during the spawning season compared with females with no young, but both did not differ from males and females with yearlings and 2-year-olds. Females with young that avoided salmon streams were significantly lighter indicating that female choice to avoid consumption of salmon carries a cost that may translate to lower female or cub survivorship. The role of the social hierarchy of males and females, mating history, and paternity in affecting the risk of infanticide and foraging decisions of female brown bears merit further investigation.

show abstract

Section: Brown Bears In the Alexander Archipelagomentioning

confidence: 94%

Consumption of salmon by Alaskan brown bears: a trade-off between nutritional requirements and the risk of infanticide?

2004

Self Cite

View full text Add to dashboard Cite

show abstract

“…Additionally it has been reported that black and brown bears in excellent condition start hibernation earlier [28], [61], [62]. We created individual activity indices by summing the acceleration values on the orthogonal axes (0–510) for each 5-minute interval.…”

Section: Methodsmentioning

confidence: 99%

Factors Affecting Date of Implantation, Parturition, and Den Entry Estimated from Activity and Body Temperature in Free-Ranging Brown Bears

Friebe

Evans²,

Arnemo

et al. 2014

PLoS ONE

View full text Add to dashboard Cite

Knowledge of factors influencing the timing of reproduction is important for animal conservation and management. Brown bears (Ursus arctos) are able to vary the birth date of their cubs in response to their fat stores, but little information is available about the timing of implantation and parturition in free-ranging brown bears. Body temperature and activity of pregnant brown bears is higher during the gestation period than during the rest of hibernation and drops at parturition. We compared mean daily body temperature and activity levels of pregnant and nonpregnant females during preimplantation, gestation, and lactation. Additionally we tested whether age, litter size, primiparity, environmental conditions, and the start of hibernation influence the timing of parturition. The mean date of implantation was 1 December (SD = 12), the mean date of parturition was 26 January (SD = 12), and the mean duration of the gestation period was 56 days (SD = 2). The body temperature of pregnant females was higher during the gestation and lactation periods than that of nonpregnant bears. The body temperature of pregnant females decreased during the gestation period. Activity recordings were also used to determine the date of parturition. The parturition dates calculated with activity and body temperature data did not differ significantly and were the same in 50% of the females. Older females started hibernation earlier. The start of hibernation was earlier during years with favorable environmental conditions. Dates of parturition were later during years with good environmental conditions which was unexpected. We suggest that free-ranging pregnant brown bears in areas with high levels of human activities at the beginning of the denning period, as in our study area, might prioritize investing energy in early denning than in early parturition during years with favorable environmental conditions, as a strategy to prevent disturbances caused by human.

show abstract

“…One study with three brown bears exposed to a total of five seismic exploration events reported that in three of five cases the bears responded with increased HR or movement to seismic shots, drilling or vehicle driving at a distance of 1–2 km (Reynolds et al ., 1983). Another study found increased activity levels when the bears were tracked with VHF receivers from an aeroplane (Schoen et al ., 1987). …”

Section: Introductionmentioning

confidence: 99%