Study of background color-matching in Hyla japonica through digital photography (#544)
Treefrogs can change their dorsal color to match backgrounds, most likely for crypsis. Most studies utilize uniform backgrounds in their experiments, and the effect of a mixed background has not been studied previously. This is significant because uniform backgrounds are rare in the forests and wetlands that these frogs inhabit. We hypothesized that treefrogs would react to mixed backgrounds in one or both of two ways: 1) develop spots, 2) perceive the background as a uniform, combined color.
Captured frogs were allowed to accommodate for 8 hours in the dark. Temperature, humidity and brightness were all controlled. There were 4 different background treatments (black, black and white checkered, middle gray, white), which were randomized so that the order of treatments would not affect them. We photographed the frogs at regular intervals alongside a Macbeth color checker, which was then used as a reference in order to linearize the photos and remove biases inherent in the camera’s image processing. We used ImageJ, a free program available online, to linearize the photos.
The frogs reacted similarly to our expectations. A significant amount of individuals developed spots on checkered backgrounds, but the base dorsal color was similar between black and white checkered backgrounds and gray backgrounds.
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- Pike, T. (2011). Using digital cameras to investigate animal colouration: Estimating sensor sensitivity functions. Behavioral Ecology and Sociobiology, 849-858.