Effects of Capture on
Scandinavian Brown Bears

Key Points

The utilization of wild animals for research requires evaluation of the effects of capture and invasive sampling. Determining the severity and duration of these interventions on the animal’s physiology and behavior allows for refining study methodology and for excluding or accounting for biased data.

Human disturbance, including research efforts, can affect animal life history and even population dynamics. However, the consequences of these disturbances are difficult to measure.

Hibernating animals are highly vulnerable to disturbance, because hibernation is a process of major physiological changes, involving conservation of energy during a resource-depleted time of year.

Both body temperature and heart rate increased during winter capture and returned to hibernation levels after 15–20 days. We showed that bears required 2–3 weeks to return to hibernation levels after winter captures, suggesting high metabolic costs during this period.

Movement rates of bears captured in winter were affected from den exit until hyperphagia phase

The wax coating of Telonics transmitters, used for VHF tracking, was not biocompatible, and the technical quality of the devices was poor, thus these implants should not be used in brown bears.

Research on wild animals often necessitates the capture, immobilization, and tagging of individuals, often with GPS or radio collars or tags. Although already intrusive, tagging procedures may include even more invasive methodologies such as pulling teeth or hair, drawing blood, muscle biopsies, or surgery, depending on the goal of the scientific study. How these procedures affect the subsequent physiology and behavior of the study species is a central question in wildlife ecology. This is because capture-induced shifts in behavior may cloud our understanding of the actual behavioral patterns we are attempting to measure in the first place. Furthermore, animal models serve as vital tools in translational medicine, bridging scientific discoveries to practical applications for human health (see Bear physiology and human health). However, ethical considerations demand a careful balance between societal benefits and the welfare of research animals, particularly when utilizing wild animals and employing invasive sampling methods. Studies involving Scandinavian brown bears captured both in the dens during hibernation and via helicopter revealed altered behavior and physiology post-capture and surgery (1, 2). This underscores the need for cautious interpretation of data collected from animals after subjecting them to invasive techniques.

Effect of captures during summer

Here, we explored the effect of invasive capture procedures (captures that included abdominal surgery or muscle biopsy) on bear behavior in the days, weeks, and months following the capture event. Subadult bears captured in summer showed reduced movement and body temperature for at least 14 and 3 days, respectively, with an 11% decrease in hourly distance, compared to pre-capture levels, but did not differ in the timing of hibernation onset (2). We reveal that brown bear behaviour and physiology can be altered in response to capture and surgery for days to months, post-capture (2). This has broad implications for the conclusions of wildlife studies that rely upon invasive sampling. Currently ongoing research is evaluating the short-term effects of capture during spring on Scandinavian brown bears. Preliminary results on the effects of captures in spring indicate that bear behavior is disturbed for about one week after capture.

Effect of captures during winter hibernation

Human disturbances can profoundly impact animal life history and population dynamics, especially for hibernating species vulnerable to disturbance-induced physiological changes. Research on subadult brown bears captured in winter showed increased body temperature and heart rate during captures (1). These changes took 2-3 weeks to return to normal hibernation levels, suggesting high metabolic costs associated with the capture event (1). In other words, the capture event altered the hibernating bears baseline physiology which likely resulted in increased energy expenditure, a high cost for hibernating bears. Winter captures resulted in delayed den emergence and reduced movement rates after den exit persisting into summer (2), emphasizing the need for careful consideration of disturbance effects on hibernating wildlife populations (1).

Effects of tagging equipment

Intraperitoneal VHF radio transmitters (very high frequency (VHF) radio transmitters placed with an animal’s abdominal cavity) are sometimes used as a marking device in free-ranging wild mammals, including brown bears. However, the quality and compatibility of the device with the species raises concerns over the long-term effects of implanting such devices. A comprehensive 19-year study assessing Telonics intraperitoneal VHF radio transmitters in brown bears highlighted significant technical issues (3). These included battery failures that lead to ‘foreign body reactions’ in about half of all study bears, and long-term effects that lead to the death of 2 individuals 10 to 13 years after implantation (3). Histopathological analysis indicated that the transmitters were of poor quality and had serious technical problems, ranging from metal corrosion, detachment of the end cap, and melting of the devices wax coating (3). These results emphasize the need to avoid using Telonics intraperitoneal VHF radio transmitters with brown bears (3).

References

1. Evans AL, Singh NJ, Fuchs B, Blanc S, Friebe A, Laske TG, et al. Physiological reactions to capture in hibernating brown bears. Conservation physiology. 2016;4(1):cow061.

2. Thiel A, Hertel AG, Giroud S, Friebe A, Fuchs B, Kindberg J, et al. The cost of research: Lasting effects of capture, surgery and muscle biopsy on brown bear (Ursus arctos) movement and physiology. Animal Welfare. 2023;32:e75.