Relationships between earthworm populations, grassland management and badger densities in County Kilkenny, Ireland: The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

Earthworms, especially the larger anecic species such as Lumbricus terrestris, comprise the most significant component of the diet of the European badger (Meles meles) in northern Europe. The objective of the present study was to obtain baseline information on the earthworm populations in selected farms in a 'badger removal' area in Co. Kilkenny, and to investigate the relationships between earthworms and grassland management, and between earthworm and badger densities. Sixty eight fields in 32 farms, representing a range of grassland management intensities, were sampled between November 1999 and October 2000. Seventeen earthworm species were recorded. Mean earthworm populations (′ s.e.) were 161 ′8 individuals m - 2 in November 1999 and 136 ′ 9 in September - October 2000. Biomass estimates were 81 ′ 5 and 69 ′ 5 g m - 2 respectively. Spring estimates were lower (72 ′ 6 individuals m - 2 , 44 ′ 4 g m - 2 ), reflecting reduced earthworm activity due to dry soil conditions. ANCOVA revealed significant (P < 0.01) positive effects of both stocking rate and N fertilizer use on total earthworm biomass, but not on earthworm abundance. The response mainly reflected trends in anecic species (mainly L. terrestris). The correlations between earthworm populations and badger densities were generally weak, but when badgers located within 250 m of farm boundaries were included in the analysis, there were significant positive correlations between badger and total earthworm (r = 0.60) and L. terrestris (r = 0.40) abundance. The lack of stronger relationships probably reflects the wide availability of earthworm-rich grazed grassland suitable for badger foraging.