Comprehensive DescriptionRead full entry
Phyllobates bicolor is a small frog, with males reaching an adult size of 32.1-39.5 mm and females reaching 35.7-42.7 mm (Myers et al. 1978). The skin is smooth (Silverstone 1976). Both premaxillary and maxillary teeth are present (Silverstone 1976). The first finger is longer than the second, and the digits have expanded discs (Silverstone 1976). Toes lack webbing (Silverstone 1976).
Phyllobates bicolor color patterning is very striking. The dorsum and sides are a uniform golden yellow or orange, as well as the dorsal surfaces of the upper arm and thigh (Myers et al. 1978). In contrast, the dorsal surfaces of the forearm and calf are black, and may or may not have dense yellow (or sometimes blue) spotting (Myers et al. 1978). The ventrum may be completely black, or washed with light orange, light gold, or bluish green (Myers et al. 1978). There is occasionally a black patch on the throat (Silverstone 1976). The tympanum is partly yellow-orange and partly black (Silverstone 1976). In some individuals, the tip of the snout is black (Silverstone 1976). Irises are black or reddish-brown (Silverstone 1976).
This species, like P. terribilis, exhibits an ontogenetic color change; juveniles are dark brown to black in color, with two yellowish dorsolateral bands. As the frogs reach maturity, the dorsolateral stripes disappear, and the frogs become more brightly colored. In contrast, the juvenile pattern of light stripes on a dark background is retained into adulthood in other members of the P. bicolor group, P. aurotaenia, P. lugubris and P. vittatus (Myers et al. 1978; Silverstone 1976).
As is true of other species in the genus Phyllobates, this species produces batrachotoxins. However, captive-born and bred dendrobatid frogs lack toxicity, since the toxins are acquired at least in part from dietary sources such as ants, mites or beetles (Daly et al. 1980; Daly et al. 1992; Dumbacher et al. 2004). In contrast, the toxins persist in wild-caught animals even when they are maintained in captivity (Daly et al. 1978).
Myers et al. (1978) have speculated that there might be either hybridization or a cline between P. bicolor and P. aurotaenia in the upper San Juan drainage, due to the intermediate size and coloration of the Phyllobates found there.