Abstract 330 – How far is the female den

Slaven Reljic, Goran Guzvica, Lidija Sver, Gaja Hana Francky, Laura Schulte, Ratko
Popovic, Djuro Huber

If you see a bear family with newborn cubs, the typical question is: How far away is their den?
The answer is particularly important if new infrastructure (such as wind turbines) is planned in
the area. The Environmental impact assessment is expected to determine the minimum safe
construction exclusion zone. We know that bears tend to choose remote areas with no human
influence, which are usually difficult to access and/or at higher altitudes. It is of utmost
importance to preserve the brown bears’ denning areas. In Croatia, the construction of wind
farms in these areas has been rising in recent years.
In this study, we wanted to answer the question of how far a female bear, alone, with cubs of
the year (COYs) or yearlings, moves away from the den in the moment of the observation (with
an automatic camera or by a human). In this way, we can make the best possible estimate of
the minimum distance at which the wind turbine can be built. We collected the telemetry data
of 11 female brown bears tracked in Croatia in a period from 2010 to 2024. For each of the
females, we have verified data on their reproductive status. We analyzed the GPS data for four
standard seasons and compared the size (MCP 100%) of the females' seasonal ranges in terms
of the presence or absence of COYs or yearlings. We also measured the greatest distance from
the den to the edge of the range in certain seasons. The smallest home ranges and the smallest
distance from the den occurred in spring after females had emerged from the den with cubs of
the year, on average 6.5 km2 and 3.9 km, respectively. The seasonal range size of females with
COYs increased in summer (22 km2; 5.7 km) The largest range and the greatest distance from
the den was in the autumn (females with COYs making excursions; 349 km2 and 47 km,
respectively). Excursions occurred mostly in September or October, except for one female who
made it in the spring season. The length of the trips ranged from 10 to 38 km.