Visual and chemical masquerade in a bird dropping crab spider: predator avoidance and prey attraction (#653)
A masquerading animal evolves to closely resemble inedible and generally inanimate objects such as bird droppings to avoid predation by being misidentified as inedible objects by its predators and/or gain access to prey by not correctly identified as innocuous objects by its prey. Almost all previous theoretical and empirical studies have exclusively focused on visual masquerade, in which the animal’s body colour, size and shape mimic an inanimate object. Here we provide the first evidence of both visual and chemical masquerade in animals. The crab spiders of the genus Phrynarachne not only visually resemble a typical bird dropping in colour, size and shape, they are also smelled like bird droppings. Yet this notion remains untested. We hypothesized that the bird dropping crab spiders resemble bird dropping not only visually but also chemically to repel predators and also attract prey. We tested this hypothesis by using visual modeling and by performing behavioural assays using Portia sp. as predators and houseflies (Musca domestica) as prey. We provided the first empirical evidence that like bird droppings, either visual, volatile chemical cues emitted from P. ceylonica’s body and silk alone or both repelled significantly more Portia and attracted significantly more flies compared to the controls. Accordingly, we concluded that P. ceylonica forms a visual and chemical masquerade that resembles bird droppings, thus reducing predation risk and at the same time increasing foraging success.