How did the telemetrically monitored roe deer bucks in Slovenia spend the summer?

After we captured 12 roe deer (6 males and 6 females) last season and equipped them with telemetry collars in six hunting clubs from the Jelovica study area in Slovenia, we have been following their movements with great interest this spring and summer. With members of the hunting clubs Železniki, Selca, Jošt – Kranj, Bohinjska Bistrica, Sorica and Jelovica – Ribno we followed their spatial behaviour, as roe deer have a distinct annual biological cycle, thus we expected to witness their seasonal movements between their winter home ranges and summer territories.

Here we present the movements of three roe deer bucks from the Jelovica study area.

Jule

We have been tracking the movements of Jule on the southern slopes of Ratitovec mountain for a year and a half, which gives us an insight into the stability of his seasonal home ranges. Jule is an example of a roe deer that migrates between two areas during the year: he spends the winter half of a year in his winter home range, where he socialises with other roe deer, and during the summer season he moves to his summer territory, the borders of which he defends from other roe deer males. It turns out that Jule uses the same seasonal ranges every year.

He left his winter home range (Map 1: blue polygon) in February both years (2021 and 2022). At that time, the transition period to the summer area started, when he was moving between the winter and summer ranges (blue locations on the map) for about one month. Jule then occupied the same summer territory both years (orange polygon for 2022, red polygon under it for 2021), which is a typical breeding strategy of a male roe deer. After the breeding season, the summer territories of the males dissolve and roe deer spend the winter in mixed groups. In autumn 2021, Jule migrated back to his winter territory in just one afternoon.

Miro and Forti

Two adult roe deer males that we caught in the same box trap last winter, on the other hand, did not migrate at the end of the winter. They stayed in the same area during the summer as they had used during the winter, when a large part of their home ranges overlapped. However, they use their space differently in different months. For example, before the start of the territorial season in February, they used home ranges of approximately 44 ha (Miro) and 32 ha (Forti) (Map 2: dashed polygons). Then, in March, both bucks restricted their movements to smaller areas: Miro to approximately 26 ha and Forti to 20 ha. In June, at the full extent of the territorial season, they used territories of 24 ha (Miro) and 15 ha (Forti) only (Map 2: polygons bordered by solid lines). In parallel with the reduction of their territories during the territorial season, their territories overlapped less and less, too, until they were completely excluded from the same areas. Thus, in February their home ranges overlapped by as much as 63 % of Forti’s territory (dashed polygons), whereas in June there was almost no overlap between their territories (solid line polygons).

After the captures, the box traps are still monitored by automatic photo-traps. Here, roe deer buck Forti returned to the box trap again, after being captured and tagged.