Capture, Anesthesia, and Disturbance of Free-Ranging Brown Bears (Ursus arctos) during Hibernation

Abstract

We conducted thirteen immobilizations of previously collared hibernating two- to four-year-old brown bears (Ursus arctos) weighing 21–66 kg in central Sweden in winter 2010 and 2011 for comparative physiology research. Here we report, for the first time, an effective protocol for the capture and anesthesia of free-ranging brown bears during hibernation and an assessment of the disturbance the captures caused. Bears were darted in anthill, soil, or uprooted tree dens on eleven occasions, but two bears in rock dens fled and were darted outside the den. We used medetomidine at 0.02–0.06 mg/kg and zolazepam-tiletamine at 0.9–2.8 mg/kg for anesthesia. In addition, ketamine at 1.5 mg/kg was hand-injected intramuscularly in four bears and in six it was included in the dart at 1.1–3.0 mg/kg. Once anesthetized, bears were removed from the dens. In nine bears, arterial blood samples were analyzed immediately with a portable blood gas analyzer. We corrected hypoxemia in seven bears (PaO2 57–74 mmHg) with supplemental oxygen. We placed the bears back into the dens and antagonized the effect of medetomidine with atipamezole. Capturing bears in the den significantly increased the risk of den abandonment. One of twelve collared bears that were captured remained at the original den until spring, and eleven, left their dens (mean ± standard deviation) 3.2±3.6 (range 0.5–10.5) days after capture. They used 1.9±0.9 intermediate resting sites, during 6.2±7.8 days before entering a new permanent den. The eleven new permanent dens were located 730±589 m from the original dens. We documented that it was feasible and safe to capture hibernating brown bears, although they behaved differently than black bears. When doing so, researchers should use 25% of the doses used for helicopter darting during the active period and should consider increased energetic costs associated with den abandonment.

Decrease in the red cell cofactor 2,3-diphosphoglycerate increases hemoglobin oxygen affinity in the hibernating brown bearUrsus arctos

“…Samples of blood were taken from the same six free-ranging 2-to 3-yr-old Eurasian brown bears, Ursus arctos, three females and three males captured during winter hibernation (February: females 35, 57, and 59 kg; males 21, 25 and 58 kg) and summer (June: females, 28, 72, and 47 kg; males, 27, 51, and 22 kg) in Dalarna county, Sweden, as described previously (17). The bears were immobilized by darting in the den during February 2011 and again by darting from a helicopter during June.…”

“…The bears were immobilized by darting in the den during February 2011 and again by darting from a helicopter during June. Bears were anesthetized as described in detail in a previous study (17). Briefly, in winter, a mixture of tiletamine-zolazepam (1.1 mg/kg, except 2.5 mg/kg in one male bear, 25 kg), medetomidine (0.03 mg/kg) and ketamine (1.3 mg/kg, except 3 mg/kg in one male bear, 25 kg) was used, and in summer, a mixture of tiletamine-zolazepam (4.7 mg/kg) and medetomidine (0.09 mg/kg) was used.…”

“…Briefly, in winter, a mixture of tiletamine-zolazepam (1.1 mg/kg, except 2.5 mg/kg in one male bear, 25 kg), medetomidine (0.03 mg/kg) and ketamine (1.3 mg/kg, except 3 mg/kg in one male bear, 25 kg) was used, and in summer, a mixture of tiletamine-zolazepam (4.7 mg/kg) and medetomidine (0.09 mg/kg) was used. Doses were based on body mass and time of year (due to differences in expected metabolism), as previously reported (17). Blood samples were taken within ϳ20 min from darting.…”

“…During this time, bears appear to be resistant to loss of muscle mass, strength, or bone density (18,24,29,43,14,44). During hibernation bear body temperature is downregulated only slightly, fluctuating from ϳ37°C to a minimum of 30°C, as found in brown and in black bears (Ursus americanus) (17,26,27,36,43), whereas O 2 consumption rate is downregulated by 75% (43). In comparison, in most smaller hibernators, such as ground squirrels and marmots, body temperature drops dramatically to values close to ambient temperatures (32, 37, 48), with a consequent strong Q 10 -induced depression of metabolic rate (where Q 10 is the rate coefficient for a 10°C change in temperature).…”

Winter blood values of selected parameters in a group of non-hibernating captive brown bears (Ursus arctos)

“…The obvious indicator of lower activity was body temperature (mean 35.9 o C) comparing to brown bears in the stage of full activity (37-37.5 o C, Hissa et al 1994). The temperature of hibernating free-ranging brown bears immobilized for research ranged from 32.2 to 34.8 o C within 35 minutes after inducing anesthesia (Evans et al 2012).…”