Contrasting coloration in terrestrial mammals

Abstract

Here I survey, collate and synthesize contrasting coloration in 5000 species of terrestrial mammals focusing on black and white pelage. After briefly reviewing alternative functional hypotheses for coloration in mammals, I examine nine colour patterns and combinations on different areas of the body and for each mammalian taxon to try to identify the most likely evolutionary drivers of contrasting coloration. Aposematism and perhaps conspecific signalling are the most consistent explanations for black and white pelage in mammals; background matching may explain white pelage. Evidence for contrasting coloration is being involved in crypsis through pattern blending, disruptive coloration or serving other functions, such as signalling dominance, lures, reducing eye glare or in temperature regulation has barely moved beyond anecdotal stages of investigation. Sexual dichromatism is limited in this taxon and its basis is unclear. Astonishingly, the functional significance of pelage coloration in most large charismatic black and white mammals that were new to science 150 years ago still remains a mystery.

Polarotactic tabanids find striped patterns with brightness and/or polarization modulation least attractive: an advantage of zebra stripes

“…These and more explanations have been thoroughly discussed and criticized by Ruxton (Ruxton, 2002) and Caro (Caro, 2009), who concluded that the majority of these hypotheses are experimentally unconfirmed, and thus the exact cause of stripes in zebras remains unknown. Nevertheless, the explanation of Waage (Waage, 1981) for the benefit of zebra stripes (i.e.…”

“…Nevertheless, the explanation of Waage (Waage, 1981) for the benefit of zebra stripes (i.e. protection from tsetse flies) has been the only hypothesis to be partially supported experimentally (Turner and Invest, 1973;Brady and Shereni, 1988;Gibson, 1992;Ruxton, 2002;Lehane, 2005;Caro, 2009).…”

“…Since the 19th century, a number of alternative hypotheses (Waage, 1981;Ruxton, 2002;Lehane, 2005;Caro, 2009) have been proposed to explain the striped pattern of zebras, including predator defence, social interaction, indication of physical condition, thermoregulation, and protection from tsetse flies (a more detailed account is given in the Appendix). These and more explanations have been thoroughly discussed and criticized by Ruxton (Ruxton, 2002) and Caro (Caro, 2009), who concluded that the majority of these hypotheses are experimentally unconfirmed, and thus the exact cause of stripes in zebras remains unknown.…”

Optimizing countershading camouflage

“…camouflage | defensive coloration | animal coloration | shape-from-shading | shape perception M any animals, across diverse taxa and habitats, are darker on their dorsal than ventral side (1)(2)(3)(4)(5)(6)(7)(8). One of the oldest theories of animal camouflage (9)(10)(11)(12)(13) suggests that this "countershading" has evolved to cancel the dorsoventral gradient of illumination across the body, thus obliterating cues to 3D form and enhancing background matching.…”

White plant shoots, wax-producing insects and other white structures made by arthropods: A mimicry complex?

“…White colouration is also useful for thermoregulation, and may provide camoufl age in snowy or icy environments or in deserts with light-coloured sand (e.g. Cloudsley- Thompson, 1979;Caro, 2005Caro, , 2009Lev-Yadun, 2016). In insects, various taxa produce white waxes that are mixtures of long-chain esters, straight-chain hydrocarbons and free fatty acids (Brown, 1975) as a defence against natural enemies, UV radiation and desiccation (Pope, 1979(Pope, , 1983Eisner et al, 2005;Yamazaki, 2012).…”