Butterfly spatial distribution and habitat requirements in a tropical forest: impacts of selective logging.
Spatial distribution, abundance and habitat requirements of Ragadia makuta (Satyrinae) were studied in Sabah (Borneo) during August 1997, in undisturbed forest and forest that had been selectively logged 8-9 years previously. Measurement of vegetation structure indicated that undisturbed forest had significantly larger trees and greater canopy cover than logged forest, and a principal components analysis extracted 2 factors related to forest density and tree size that were also significantly higher in undisturbed forest. However, there was significant spatial heterogeneity in vegetation structure within logged forest. In undisturbed forest, a logistic regression model identified suitable habitat for R. makuta as areas of less dense forest close to streams. There were no differences observed between logged and unlogged habitats in spatial distribution and abundance of R. makuta. Availability of suitable habitat and habitat requirements of butterflies also did not differ between habitats. There was, however, significant heterogeneity in butterfly abundance within logged forest, corresponding with availability of suitable habitat. Fieldwork in 1997 coincided with a severe drought, and butterfly spatial distribution and abundance were significantly reduced compared with a year of more normal rainfall (1996), while populations in 1997 contracted to areas around streams and to areas with high cover of host-plant. It is concluded that selectively logged areas can be highly heterogeneous in relation to levels of disturbance and the effects of selective logging on forest structure and the availability of suitable habitat is discussed in relation to the responses of R. makuta to habitat disturbance.