Annual and circadian activity patterns of badgers in Bialowiez
Annual and circadian activity patterns of badgers in Bialowiez·a Primeval Forest (eastern Poland) compared with other Palaearctic populations.
The annual and circadian rhythms and duration of activity of badger were studied in a low-density population inhabiting the primeval woodland in the European temperate zone. Results were compared with available data from the literature on seasonal changes in body mass and winter inactivity of badgers from across the Palaearctic region.
Field work was carried out in Bialowiez·a Primeval Forest, eastern Poland. Biogeographical variation was reviewed based on twenty-three localities in the Palaearctic region (from Western Europe to Central Siberia).
Thirteen badgers were radio-collared in 1997–2001. Their circadian activity was sampled by 24-h sessions of continuous radio-tracking with location taken at 15-min intervals. Annual activity was studied by radio-tracking and inspections of setts. Earthworm (badgers’ main food) biomass was estimated in four types of habitats throughout the year.
Badgers were nocturnal with one long bout of activity. Their rhythms of diel activity differed between spring and autumn, and between adult and subadult individuals. On average, badgers emerged from setts at 19:00hours and returned to them at 03:42hours. Thehighest level of activity was recorded between 20:00 and 03:00hours. Duration of daily activity was, on average, 8.2hday-1, but varied significantly between seasons. The seasonal changes were inversely related to the abundance of earthworms. Duration of activity also depended on daily temperature, especially in the cold season. In winter, badgers stayed inactive for an average of 96days per year. In autumn, they built fat reserves and their body mass nearly doubled compared with the spring values.
The literature review on annual cycle of activity and body mass changes in Eurasian badgers showed that fat storage and duration of winter sleep strongly depended on climate (best approximated by January mean temperature). In regions with warm climates, badgers were active year round and their body mass changed only slightly, while in regions with severe winters badgers increased their body mass twofold from spring to autumn, and stayed inactive for as long as 6months per year.
We propose that, in the temperate and boreal zones of the Palaearctic region, the ultimate determinant of biogeographical variation in badgers’ annual activity is the winter shortage of earthworms, which are the main component of badger diet.
Activity rhythm; biogeographical variation; body mass change; earthworm abundance; Eurasian badger; winter sleep; intraspecific variation