Background colour matching in a wild population of Alytes obstetricans

Abstract

The capacity for physiological colour change has long been described in anuran amphibians. Camouflage against predators seems to be the most relevant function of dynamic changes in skin colour of frogs, but key aspects such as the rate at which these changes occur, or the specific colour components involved are not completely clear. Whereas most research on the topic has been reported on tree frogs in laboratory conditions, studies in other anurans or in the field are much scarcer. Here we show a potentially plastic, adaptive response in coloration of common midwife toads, Alytes obstetricans, from a population of central Portugal, whose pigmentation varied with their natural backgrounds. Using quantitative image analysis, we compared hue, saturation and brightness of dorsal skin coloration of toads and the colour of the area of ground immediately around them. We found a positive correlation between coloration of toads and background colour for the three components of the colour. As well as other anuran species, A. obstetricans might adjust skin coloration to match the surrounding environment, thus benefitting from short-term reversible crypsis strategies against predators. A less supported hypothesis would be that toads accurately select matching backgrounds to improve concealment as an antipredatory strategy.

Ontogenetic changes in spot configuration (numbers, circularity, size and asymmetry) and lateral line in Neurergus microspilotus (Caudata: Salamandridae)

“…; Polo‐Cavia et al . ). It has also been documented that many colours and pigments can have other adaptive functions such as photoprotection, structural support, microbial resistance and thermoregulation (Rosenblum et al .…”

“…A pigmentation pattern can be defined as an assortment of coloured marks (spots, patches and stripes of various sizes and colours) with sharp contrast with body background. It has been shown that pigmentations are often used for intraspecific communication such as ornamental colour used for mate choice and intrasexual competition (Eizirik et al, 2003) and various interspecific interactions such as antipredatory, aposematic and cryptic behaviour (Hoekstra, Hirschmann, Bundey, Insel, & Crossland, 2006;Polo-Cavia, Oliveira, Redondo Villa, & Márquez, 2016). It has also been documented that many colours and pigments can have other adaptive functions such as photoprotection, structural support, microbial resistance and thermoregulation (Rosenblum, Hoekstra, & Nachman, 2004;Rosenblum, Rompler, Schoneberg, & Hoekstra, 2010).…”

Effects of substrate color on intraspecific body color variation in the toad‐headed lizard, Phrynocephalus versicolor

“…In addition to the fixed color adaptations (Hoekstra, Hirschmann, Bundey, Insel, & Crossland, 2006;Rosenblum, Roempler, Schoeneberg, & Hoekstra, 2010), selective pressure on behavioral preference of local color matching remains to be explored to understand the benefits of color adaptation. As the visual background against which it is viewed is the primary basis of camouflage, various species prefer substrate or habitat that enhance matching for camouflage, including fish (Kelley, Taylor, Hart, & Partridge, 2017;Kjernsmo & Merilaita, 2012;Smithers, Rooney, Wilson, & Stevens, 2018), amphibians (Polo-Cavia, Miguel Oliveira, Redondo Villa, & Marquez, 2016;Rabbani, Zacharczenko, & Green, 2015), reptiles (Hamilton, Gaalema, & Sullivan, 2008;Marshall, Philpot, & Stevens, 2016;Nafus et al, 2015), birds (Lovell, Ruxton, Langridge, & Spencer, 2013), and insects (Gillis, 1982;Kang, Stevens, Moon, Lee, & Jablonski, 2015;Kettlewell & Conn, 1977;Sargent, 1966). Therefore, animal substrate color selections could be indicative of whether they are behaviorally segregated according to their body color and further explain its relationship with camouflage.…”

Colour change of twig-mimicking peppered moth larvae is a continuous reaction norm that increases camouflage against avian predators

“…Visual stimuli exist in two forms: achromatic (luminance), and chromatic (hue/chroma). Responses to achromatic stimuli (luminance) have been reported in sand fleas, geckos, toads, and flatfish ( Polo-Cavia et al, 2016 ; Ryer et al, 2008 ; Stevens et al, 2015 ; Vroonen et al, 2012 ). Tree frogs ( Hyla japonica ) adjust their body colour and luminance, to maximise camouflage against visually heterogeneous backgrounds, although the response to achromatic stimuli was stronger ( Choi & Jang, 2014 ; Kang, Kim & Jang, 2016 ).…”

“…Tree frogs ( Hyla japonica ) adjust their body colour and luminance, to maximise camouflage against visually heterogeneous backgrounds, although the response to achromatic stimuli was stronger ( Choi & Jang, 2014 ; Kang, Kim & Jang, 2016 ). Many of these studies propose that colour change in these animals is induced by visual cues, but the visual pathways were not explicitly studied, and additional cues such as temperature or texture were often not controlled ( Lin, Lin & Huang, 2009 ; Polo-Cavia et al, 2016 ; Yamasaki, Shimizu & Fujisaki, 2009 ).…”