Contrast to background influences predation on aposematic but not cryptic artificial caterpillars in a Brazilian coastal shrubland

Abstract

AbstractAposematism and crypticity are visual defensive strategies against predation; however, the relative effectiveness of these two strategies to reduce the risk of predation is not yet fully understood. We evaluated the risk of predation for caterpillars with cryptic and aposematic colouration as well as the probability of predation relative to the natural variation of contrast with the substrate. We expected that the two models would experience similar predation attempts and that the contrast with the substrate would be negatively related to the predation on aposematic mimic models and positively to the predation of cryptic models. Overall, 224 models were laid out along a transect and exposed to predation for five consecutive days during winter and autumn. Daily predation was 11.0% (winter) and 4.8% (autumn). Significant differences were not observed between predation rates on the two model types (50.6% aposematic). Most of the predated models had arthropod marks (86.4%) and only 13.6% had bird marks. The chance of predation was higher the greater the contrast between the aposematic mimic model and the substrate, although no relationship was observed for the cryptic model. Our results suggest that the two colour patterns do not differ in their defensive effectiveness and that micro-habitat selection might define the predation risk on aposematic mimic caterpillars in environments dominated by arthropod predators.