Using camera traps to assess temporal responses of brown bears to human presence in Croatia
Whilst studying for my MRes at Imperial College London, I was very lucky to conduct one of my research projects in Croatia with Professor Josip Kusak and Professor Djuro Huber from the University of Zagreb.
Croatia is home to three of Europe’s five large carnivores: brown bears (Ursus
arctos), grey wolves (Canis lupus), and Eurasian lynx (Lynx lynx):
Prof. Kusak and Prof. Huber have been studying the ecology and conservation of these species since the 1980s and it was great to be able to help with their research. Monitoring these large carnivores can be conducted in a variety of ways including snow tracking, camera trapping and radio/GPS tracking animals that are wearing collars that transmit signals. To fit a collar, you first need to capture the animal and so Josip and Djuro taught me how to do that in the form of setting box traps for lynx and foot hold traps for bears and wolves.
Most wildlife collars are both VHF and GPS transmitters. The GPS locations are sent to the researchers remotely, whereas the VHF signal has to be tracked with an antennae receiver at closer proximity to the animal. The VHF radio signal is very useful as it allows researchers to continue tracking animals even if the GPS is faulty. However, without the GPS location as a guide, it’s difficult to know where to look for an animal to get close enough to pick up its VHF signal, especially for wide-ranging species like most large carnivores. Therefore, the most efficient approach is to conduct an aerial search, whereby the radio antennae are attached to the wings of a small plane. Luckily for me, Josip took me on one of these aerial searches and it was quite the experience to fly over Plitvice Lakes National Park listening out for the beeping of bear collars!
I used data gathered from camera traps to investigate whether increasing numbers of tourists are altering brown bear behaviour in the Plitvice Lakes National Park (PLNP).
The PLNP is known for its stunning system of inter-connected lakes and waterfalls, which attract more and more visitors each year. Although access to natural areas can play an important role in connecting people with nature, outdoor recreation may have detrimental impacts on wildlife. A recent study by Gaynor et al. (2018) found that diurnal human activity is driving increased nocturnal activity of many different mammalian species. Shifts in activity can alter how animals feed and breed and consequently affect their survival.
I was therefore investigating whether the brown bears in the PLNP changed their activity patterns when frequenting the areas most visited by humans. Camera traps were deployed along trails and roads within the park and designated as being in either low or high disturbance areas. I then compared the times at which bears were active in these low and high disturbance areas to elucidate any shifts in activity patterns.
Although I am waiting for the research to be peer reviewed, I can share that
my preliminary results showed adult bears spent more time active at night in areas of high human usage. Optimistically, avoidance of humans by bears may facilitate coexistence between the two and reduce the number of fatal collisions on roads and railways. However, if one species changes its activity patterns, this can lead other species to change their behaviour too. It is therefore important that we try to alleviate human impacts on wildlife, to prevent unknown and potentially unwanted knock-on effects in the ecosystem.
For everyone’s amusement, here’s a sequence of photos of bear cubs play-fighting: