FEEDING STRATEGIES OF HOUSE GECKOS

Abstract

The feeding strategies of three species of house geckos were investigated. Because these three species occur together on a single study site, namely the darker and brighter parts of a building, emphasis is placed on differences that might reduce competition and allow their coexistence. The three species were found to be largely insectivorous, from an analysis of their gut contents. Only a slight difference in the types of prey eaten was evident. The range of prey items consumed by G. mutilata differed more widely than those consumed by C. platyurus and H. frenatus, which was more similar. This is attributed to the fact that G. mutilata prefers the more poorly-lit areas for hunting whereas the other two species prefer to hunt near lights. This is reflected in their dietary overlap values : 0.64 between C. platyurus and H. frenatus, 0.58 between C. platyurus and G. mutilata and 0.55 between H. frenatus and G. mutilata. There was little food preference; the geckos feeding mainly on whatever prey is available. Interspecific competition was reduced by two factors. Larger geckos tend to eat larger prey, ie the larger sex takes the larger prey while the juveniles take the smaller prey. Average prey size was however, not significantly correlated with predator size (P>0.05). Temporal differences in daily activity among the two gecko species, C. platyurus and H. frenatus are very slight and are not statistically significant (p< 0.05). Both their activity levels peak between 1800 and 1900 hrs. The daily activity of G. mutilata was not compared with that of the other two species as it prefers to hunt in the darker areas, so there may not be temporal differences separating them. Resource partitioning by means of such temporal separation of activities appear to be relatively limited among many animals (Rioklefts, 1966; Schoener, 1974). This led Huey (1974) to conclude that "because ........... geckos prefer temperature higher than those at which they are nocturnally active, it is unlikely that one would observe temporal activity segregation: all geckos should be active as early as possible in the evening". The sense of sight, smell and hearing were significantly important in prey hunting (p< 0.01) in both C. platyurus and H. frenatus with sight being by far the most important sense. This was followed by the sense of hearing and smell respectively, in hunting for flying insects . The feeding behaviour of G. mutilata with respect to these three senses was not investigated due to the insufficient numbers obtained. From the data collected from this preliminary study, only a brief idea of the comparative ecology of these three species of house geckos is possible. Further data must be collected and examined in order to interpret the ecological relationships among these three sympatric species of nocturnal geckos, particularly in resource partitioning and competitive interactions.