Environmental factors influencing the presence and abundance of a log-dwelling invertebrate, Euperipatoides rowelli (Onychophora : Peripatopsidae)

The microenvironments of decaying logs support a large invertebrate fauna, but are vulnerable to the effects of logging and land-clearing. We present an analysis of the relationship between a number of environmental variables and the occurrence and abundance of the onychophoran Euperipatoides rowell i within decomposing logs in a forest in south-eastern Australia. Aspect of slope is strongly associated with most of the environmental variables and is a good predictor of both presence and abundance of animals in logs; sout h-easterly slopes show higher levels of log colonization, larger population s within logs and a larger median weight of both males and females than nor th-westerly facing slopes. Degradation state of logs, log length, presence of termites and shrub cover are also associated with the presence of onycho phorans, while log volume shows the most marked association with abundance. Euperipatoides rowelli prefers wetter logs, although there is considerable overlap between relative water content of logs with and without onychophor ans. Log degradation state, an important factor in the presence of animals, is associated with years since felling, and our data indicate that logs be come capable of supporting large populations of E. rowelli after a minimum of 45 years of decay. Thus future logging practices have important implicat ions for the maintenance of suitable log environments for this species, and this result may be generalized to other log-reliant fauna.