Differences in trappability of badgers
Journal of Applied
Ecology, Volume 36,Number 6, December 1999, pp. 1051-1062(12) -
Many ecological studies on the European badger, as well as certain programmes to control bovine tuberculosis, would
benefit from a greater understanding of the factors that influence the
probability of capturing this animal in cage-traps. We therefore investigated
some of the factors that could explain differences in trappability between three
badger populations in England: the high-density protected populations of Wytham
Woods and Woodchester Park, and the low-density culled population of North
Trappability (the percentage of all individuals known alive
that were actually captured) did not differ between sexes or adult age classes,
but significant differences were found between cubs and adults, study areas,
seasons and years, and various interactions between these variables.
Circumstantial evidence suggests that the culling of badgers in
North Nibley may have resulted in a decrease of adult trappability in the
Adult badgers at Wytham Woods and Woodchester Park were
significantly more likely to be trapped zero times (‘trap-shy’) or all three
times (‘trap-happy’) in 1996 than predicted by the estimated capture
probabilities under the assumption of equal trappability.
Wytham Woods differed from the other study areas in that
trappability of its badgers was positively related to their body weight and its
adult badgers were more likely to be trapped than cubs. These differences could
be a consequence of differences in trapping procedures that were followed at
Wytham (no prebaiting and fewer traps per badger).
Trappability of badgers was not associated with social group
size. Although it is difficult to determine precisely the movement and
tuberculosis status of badgers based on mark–recapture data, our analyses did
not suggest that either variable affected the likelihood of being trapped.
Studies that compare demographic, biometric and epidemiological
parameters based on data collected from badgers captured at different times or
places ought to account for the observed differences in trappability.
cage-trapping; capture–mark–recapture; capture
probability; Mycobacterium bovis; population estimation