Ansonia vidua is a highland stream toad. It has been recorded exclusively from Gunung Murud, at 2,152 m asl altitude.

According to the original description (Hertwig et al. 20214) "Ansonia vidua (...) can be differentiated from all other congeners by the following combination of characters: SVL 33.5 and 34.3 mm in the two females known; body not flattened; canthus rostralis slightly swollen; two low longitudinal interorbital ridges present; dorsum of body, flanks and upper surfaces of the limbs covered with numerous small, regular, low, rounded warts, resulting in a velvet-like appearance, only warts on scapular and temporal regions slightly enlarged; warts on dorsum, head and limbs terminating in a single fine, keratinous spine;first finger short, not reaching tip of second finger when adpressed; no sharp tarsal ridge; no skin flaps on posterior thigh near vent; third and fifth toe with 2½ phalanges free of web medially; colouration of the dorsal surface of head and body uniformly black-brown; limbs dark brown with lighter areas on joints of the limbs and phalanges; ventral surface uniformly dark grey to yellowish brown; dorsal and ventral parts of body and limbs completely patternless."

Much of the biology of this high-elevation species remains mysterious. Only females have been reported sofar (species named "widow" because of that and the black color). Tadpoles are unknown. The ecology is unknown. The species has been encountered at night when perching on low vegetation near streams in undisturbed montane mossy forest.