Environmental correlates of badger social spacing across Europe
Authors: Johnson Dominic D. P. , Jetz Walter , Macdonald David W. 
Published: March 2003

Aim

The European badger (Meles meles, innaeus 1758) has been a focus for numerous studies of behaviour, physiology and ecology and, in particular, for testing theories concerning the evolution of sociality. However, most of these studies originate from the British Isles, where the behavioural ecology of this species differs markedly from elsewhere across its pan‐Eurasian geographical range. We use data in the literature, from all available parts of the badger's distribution, to test whether environmental variables can explain observed variation in densities and social spacing.

Location

We used published data from studies across Europe (mainly in the western part of this region).

Methods

Data covered all of Europe, spanning Great Britain to Kazakhstan in lon‐gitude and Norway to Spain in latitude. We used simple and multiple linear regression models to test for environmental correlates of the following four dependent variables, recorded at exact study sites: (1) badger densities, (2) sett densities, (3) group sizes and (4) territory sizes. Independent variables were extracted at these same locations from meteorological databases of climate data from across Europe. Those used in the analyses were: (1) annual mean of mean monthly temperatures, (2) mean of the difference between mean January and July temperatures, (3) mean of the difference between minimum and maximum monthly precipitation and (4) annual mean of monthly actual evapotranspiration. We also tested for relationships between mean badger densities and mean values of environmental variables reported for whole countries.

Results

None of the environmental variables correlated with group or territory sizes, or with whole country measures of badger densities. However, the annual difference in minimum and maximum temperature was consistently correlated with both badger densities and sett densities recorded at specific study locations, in both single‐variable and multiple regressions. We found these relationships disappeared when single mean values were used for all of the studies on the British Isles, although in doing so sample sizes were drastically reduced as well. Further investigation revealed that the original positive relationship was composed of negative trends among the data from Great Britain and continental Europe, when these were analysed separately. This has important implications for understanding the behavioural ecology of this species, as well as the general biases that spatial correlation may cause in studies comparing populations.

Main conclusions

The precise relationship between the temperature range variable and badger densities appears to be complicated. Nevertheless, because the annual difference in the minimum and maximum temperature is related, in some way, to seasonality, this implies that badger densities are associated with seasonal constraints, or some other constraint(s) that covary with seasonality. We suggest that, if models of sociality are either seasonally or density dependent, then this finding has an important bearing on why badger social behaviour is so different across Europe. In particular, we discuss the implications of these results for the most pervasive model of social organization in the badger, the resource dispersion hypothesis.