Foraging ecology in the mehely¿s horseshoe batfrom resource preferences to competitive interactions

Abstract

Rhinolophus mehelyi and R. euryale are two morphologically very similar, sibling rhinolophids. Both often co-exist within the same areas and their maternity colonies often roost together, forming mixed clusters. Similarities in morphology and echolocation between bats should be reflected in ecological similarities. Contrarily, co-existence of these species should be associated with a mechanism of resource partitioning. Since basic knowledge on resource selection in allopatric R. mehelyi populations remained unknown, we carried out some basic behavioural studies of this species prior to focussing on examining these apparently contradicting paradigms in sympatric rhinolophids. The bulk of the diet of R. mehelyi consisted of moths, representing more than the 80% of the average volume, and more than 90% of the average occurrence. Moths were the preferred prey category, followed by lacewings and crane flies. Therefore, R. mehelyi can be considered a moth specialist. R. mehelyi mainly foraged in structurally-complex and highly-cluttered environments, particularly when close to water sources. No foraging activity was recorded in open environments. Structural complexity of foraging sites together with prey abundance seems to determine habitat selection in R. mehelyi. R. mehelyi showed a higher resting frequency than R. euryale. Body mass, forearm length, aspect ratio, and wing loading were also higher in R. mehelyi. However, a high degree of overlap occurred between species in all these parameters. Differences in resting frequency are deemed insufficient for segregation of dietary features and they may compete for trophic resources in sympatry. Nevertheless, differences in wing morphology are probably large enough to permit spatial resource partitioning. Foraging habitats were spatially segregated and also differed structurally. According to results, R. mehelyi preferred structurally less-complex foraging sites than R. euryale. Fine-scale differences in foraging habitat preferences appeared to be the principal mechanism mediating resource partitioning between R. mehelyi and R. euryale.