Behaviour 2019
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Factors influencing the efficacy of bird-dropping masquerade in a crab spider
Long Yu1,2, Xinran Miao2,3, Daiqin Li2. 1Hubei University, Wuhan, Hubei, China; 2National University of Singapore, Singapore, Singapore, Singapore; 3Australian National University, Canberra, Canberra, Australia

Phrynarachne spiders are often cited as a classical example of bird-dropping masquerade, which functions in avoiding predation because predators misidentify them as inedible bird droppings. However, it is unclear what factors cause bird-dropping resemblance to serve protective function. Phrynarachne spiders usually show black and white color patterns, which vary considerably among and within species, yet whether such a variation is adaptive remains untested. Here we explored how the black and white color patterns contribute to the efficacy of bird-dropping masquerade using 3D models. We manipulated models ranging from black to white, and presented them to predators, specialized spider-eating jumping spider. We found while predators take similar time to detect all models differing in the proportion of white patch size, predation risk significantly increases with increasing white patch size. We also found predators take longer to attack as the proportion of white patch is decreasing. Our results suggest that Phrynarachne with different black/white proportion can be equally detected but gain greater protection from bird-dropping masquerade function by decreasing in white patch size.