Bold Coloration and the Evolution of Aposematism in Terrestrial Carnivores

Abstract

Several species of terrestrial carnivores (Mammalia: Carnivora) have bold contrasting color patterns that, in some species, apparently signal possession of noxious anal gland secretions, or even physical strength and great ferocity; yet the evolutionary drivers of both placement and patterning of these contrasting pelage colors on the body, and the ecological selection pressures underlying them, have yet to be systematically examined. Here we explore these issues and find not only that both boldly colored and dichromatic species do indeed often use anal gland secretions for defense, but also that such species are stockier, and live in more exposed habitats where other forms of antipredator defense are limited. We also show that white dorsa are found in sprayers that are primarily nocturnal; that horizontal stripes are found in species that have an ability to spray anal secretions accurately; and that facial stripes are found in burrowing species that typically leave only their heads exposed to attack. Our phylogenetic reconstructions suggest that aposematic coloration has evolved more than once in terrestrial carnivores. We finish by outlining five evolutionary routes for patterns of pelage coloration in this taxon. K E Y W O R D S :Anal glands, antipredator, Carnivora, pelage, skunks, stripes.

Occupation of bare habitats, an evolutionary precursor to soil specialization in plants

“…Bareness, both naturally occurring and manipulated, was associated with increased levels of damage from herbivores in the field, and a concomitant reduction in plant fitness, in Streptanthus breweri and Streptanthus hesperidis. Apparency in bare or open environments might increase the need for enemy defense (64,65), an investment that could also trade off with competitive ability (15,16; but also ref. 39).…”

Aposematism and crypsis in a rodent: antipredator defence of the Norwegian lemming

“…3). Badgers (Meles meles) and some other carnivores that direct this weapon against an attacking enemy also have contrasting black and white facial patterns (Cott 1940;Newman et al 2005;Caro 2009, 2011, Stankowich et al 2011. The similarities suggest that the colour patterns are partly convergent and have similar function in the Norwegian lemming as in these carnivores.…”

“…Ruxton et al 2004;Mappes et al 2005;Lee et al 2010;Davies et al 2012;Futuyma 2013). Aposematism is common in insects and ectothermic vertebrates (Ruxton et al 2004) but uncommon in mammals, particularly small herbivores (Caro 2005;Stankowich et al 2011Stankowich et al , 2014Kingdon et al 2012). Exceptions in this group can help clarify the ecological conditions favouring evolution of warning signals.…”

“…For instance, experimental black and white bird mounts were avoided by raptors (Götmark 1992). (2) Black and white facial colouration is often combined with sharp teeth or other weapons, for example in terrestrial small carnivores (Caro 2009(Caro , 2011Stankowich et al 2011;below). (3) The distinct colouration of Norwegian lemmings is often complemented by loud calling from a distance and by lunges towards an attacking predator (see video movie sequence in Online Resource 1).…”

“…Koponen et al 1961;Arvola et al 1962;Myllymäki et al 1962;Andersson 1976a;Henttonen and Kaikusalo 1993). As in some small carnivores (Caro 2009;Stankowich et al 2011), larger body size and hence better defence capacity than in the sympatric voles can make aposematic warning signals adaptive in the Norwegian lemming and some other relatively large rodents, such as the hamster (Cricetus cricetus) (Andersson 1976a). Like Norwegian lemmings, it turns with ferocious defence against predators, exposing contrasting black and white colouration to the enemy it threatens to bite with sharp incisors (Petzsch 1950;EiblEibesfeld 1954).…”