Material affects attack rates on dummy caterpillars in tropical forest where arthropod predators dominate: an experiment using clay and dough dummies with green colourants on various plant species

Abstract

International audiencePredation can be one of the key factors that determine abundance in insect herbivore communities, and drive evolution of body size, and anti-predator traits, including crypsis. Population dynamics and selection pressures will depend on the identity of dominant predators in the system, and these may vary substantially among habitats. Arthropods emerge as chief predators on caterpillars in the understorey of non-montane tropical forest, whereas birds dominate elsewhere. In a tropical forest in Uganda, Africa, we evaluated marks on dummy caterpillars that differed in size, material (clay vs. dough), colourant, and plant species on which dummy caterpillars were exposed. We included live caterpillars to estimate the extent to which studies using artificial caterpillars reflect actual levels of predation. Ants and wasps were the most important damagers of dummy caterpillars, whereas bug and beetle damage was very rare, and no bird or small mammal damage was observed. Daily attack rates did not differ significantly from apparent mortality of live caterpillars (daily mortality = 12.1%), but dummy caterpillars made from dough were attacked more frequently (daily attack rate = 18.4%) than those from clay (daily attack rate = 6.9%). Caterpillars of different colour and size, and caterpillars exposed on different plant species had the same chances to be predated. This is in contrast to results from temperate area studies where birds dominate and are not affected by dummy caterpillar material, but prefer larger caterpillars. Our results are consistent with dominant predators on tropical forest caterpillars being invertebrates that are more chemically than visually oriented, so that: (1) material used for dummy caterpillars is important, (2) background matching is relatively unimportant, and (3) being large may have less of a cost. These patterns in predation might facilitate polyphagy and evolution of large body size in tropical Lepidopter

A review of the sentinel prey method as a way of quantifying invertebrate predation under field conditions

“…While parasitoids were the only natural enemy group readily identifiable using real prey, identified natural enemies of artificial caterpillars (median = 3 per study) included vertebrates (birds n = 40; mammals n = 14; reptiles (Posa et al ., ), as well as invertebrates, among them ants ( n = 12), predatory wasps (Faveri et al ., ; Jordani et al ., ; Molleman & Safian ; Sam et al ., ,b), parasitoid wasps (Tvardikova & Novotny, ; Howe et al ., ), other insects, predatory bugs, cockroaches (Molleman et al ., ), and spiders (Posa et al ., ).…”

Opposite latitudinal patterns for bird and arthropod predation revealed in experiments with differently colored artificial prey

“…In line with the study by Roslin et al (), we found that attack rates by arthropod predators on model prey decreased from low to high latitudes. The tropics are habitats with a very high abundance and diversity of arthropod predators, especially ants and wasps, which dominate the predator communities in tropical forest understoreys (Floren, Biun, & Linsenmair, ; Sam et al, ). More than a half of the studied ant species attack large caterpillars (Floren et al, ), and experiments with live insect prey have demonstrated higher predation rates by ants in the tropics than in temperate forests (Jeanne, ).…”

“…This may lead to an underestimation of bird predation in tropical forests, where both bird enclosures (van Bael, Brawn, & Robinson, ) and model caterpillars (Loiselle & Farji‐Brener, ) revealed higher rates of bird predation in the top canopy than in the lower forest strata. Model caterpillars placed in tropical forest understoreys sometimes showed no signs of bird predation (Sam et al, ). These results may be at least partly due to the higher abundance of natural prey in the top canopy than in the understorey of a tropical forest (van Bael et al, ; Basset et al, ).…”

A estrutura da paisagem e o potencial controle das “cigarrinhas-das-pastagens”

“…Therefore, these methods are being increasingly used (Meyer et al, 2015;Sam et al, 2015). However, the influence of methodological procedures on the detection of predation responses is still poorly known ).…”

“…Particularly, the effects of the type of prey Molleman et al, 2015) and the time of exposure of preys (e.g. Loiselle et al, 2002;Molleman et al, 2015;Sam et al, 2015) should be better explored. Providing different preys and using different exposure times to predation can impede the comparison of results, which may cause confusion in detecting general ecological patterns of predation and pest control.…”