Capturing and marking animals is a key method for studying wildlife populations around the world. Biologists monitor a wide array of animals this way, ranging from land and aquatic mammals to birds, reptiles, amphibians, and fish.
Data from captured and marked animals provides a wealth of information about their movements, behaviour, and population status, which are crucial for conservation and management of the various species.
Capture can be a stressful event for an animal, and we still know very little about how different types of capture events affect their physiology as well as our research and our subsequent understanding of their biology.
Through Alexandra Thiel research, we know a little more. She has evaluated the short- and long-term effects of different methods of capturing, marking and sampling on Scandinavian brown bears in her PhD work.
"I have found that capturing, marking, and sampling bears had a range of short- and long-term effects on bear movement, behaviour, physiology, body condition, and reproductive success, with more invasive methods and higher drug doses showing more negative effects", writes Thiel to inn.no.
Thiel also investigated the seasonality in biological rhythms of bears and developed a method to detect litter loss.
Investigating the potential effects of capture is rarely among the primary objectives of research projects.
"One reason for this could be that capture effects are difficult to study, mostly because we have nothing to compare them to. How do you monitor the movement or physiology of an animal that has not been caught and equipped with tracking or monitoring devices?" says Thiel.
Yet, different capture, marking, and sampling methodologies can vary widely in how invasive they are, which provided an interesting opportunity to compare methods.
"This study highlights the importance of understanding the effects of different wildlife monitoring methods on both animal welfare and research conclusions and provides robust information for the improvement of capture protocols", says Thiel.
The thesis is titled "Effects of capture in Scandinavian brown bears".
Main findings in the doctoral work:
- Capturing bears in their dens during winter resulted in reduced movement after they exited the den the following spring and lasted until late summer.
- More invasive sampling and marking procedures as well as higher immobilizing drug doses result in longer recoveries from the capture process.
- Capturing bears at a young age had long-term effects on their body condition and reproductive state.
Thiel's PhD project was part of the Scandinavian Brown Bear Research Project (SBBRP), which is run by the Norwegian Institute for Nature Research. It is primarily funded by the Environmental Protection Agency (Naturvårdsverket) in Sweden and the Norwegian Environment Agency (Miljødirektoratet) in Norway.
Physiological sensors (heart rate and body temperature) were funded by the Norwegian Environment Agency in Norway and by Medronic Inc.
Contact information:
- alexandra.thiel@inn.no