Predation on insects on Tiwai, Sierra Leone
Abstract
Tiwai is a wooded island in the river Moa near the Gola rainforest in eastern Sierra Leone. A particular feature of the island is the lack of Dorylus driver ants, which are usually major predators in African forests, including of termites. Therefore termites are very abundant and this appears to result in efficient decomposition of dry leaves and perhaps leaves less room for other decomposers. Furthermore, arachnids catch the eye, including ferocious-looking whip spiders. Many butterflies and grasshoppers showed signs of predator attacks, especially also wing damage in the shape of a lizards maul. To gain better insight in predation on butterflies, caterpillars made from modeling clay (dummies) were used. Damage to the dummies suggests a daily predation pressure of 50%. Damage to dummies was mainly caused by ants and wasps, and not
by birds. Although it was the dry season, many butterflies appeared to be young, and a good number and variety of caterpillars have been
found, including a species for which no caterpillar records existed. In total, eighty butterfly species were observed, of the about 450 that may be expected locally. Hopefully, these scarce remnants of West-African forest will be conserved, so that nature lovers and entomologists can continue to benefit from the excellent facilities.