Spatial and temporal variation in prey color patterns for background matching across a continuous heterogeneous environment

Abstract

In heterogeneous habitats, camouflage via background matching can be challenging because visual characteristics can vary dramatically across small spatial scales. Additionally, temporal variation in signaling functions of coloration can affect crypsis, especially when animals use coloration seasonally for intraspecific signaling (e.g., mate selection). We currently have a poor understanding of how wild prey optimize background matching within continuously heterogeneous habitats, and whether this is affected by requirements of intraspecific signaling across biological seasons. Here, we quantified color patterns of a wild population of shore skink (Oligosoma smithi), a variably colored lizard endemic to New Zealand, to (a) investigate whether background matching varies across a vegetation gradient; (b) assess potential signaling functions of color; and (c) to determine whether there is a trade-off between requirements for crypsis and intraspecific signaling in coloration across seasons. Although all pattern types occurred throughout the vegetation gradient, we found evidence for background matching in skinks across the vegetation gradient, where dorsal brightness and pattern complexity corresponded with the proportion of vegetation cover. There was also a significant disparity between ventral color (saturation) of juveniles and adults, and also between sexes, suggestive of sex recognition. However, there was little indication that color was condition-dependent in adults. Despite some evidence for a potential role in signaling, crypsis did not greatly differ across seasons. Our study suggests that selection favors a mix of generalist and specialist background matching strategies across continuously heterogeneous habitats.

Keywords: camouflage; crypsis; intraspecific signaling; temporal variation.

Figure 1

Shore skink (Oligosoma smithi) on the mainland North Island, New Zealand

Figure 2

Range of body color patterns of the shore skink population at Tāwharanui Regional Park: (a) four dorsal body pattern types, from left to right; plain, midplain, spot, and midspot; (b) Examples of ventral colors, ranging from both extreme ends of their coloration, with an intermediate in the middle

Figure 3

Color contrasts between body regions (dorsal body, ventral body, and ventral tail) and habitat background of shore skinks: a) achromatic contrast and b) chromatic contrast. (n = 352)

Figure 4

Color pattern trends of shore skinks at Tāwharanui. a) Frequency of four pattern types of skinks across the categorical percentage of vegetation cover. Mean color values (hue, saturation, and brightness) of body regions (dorsal, ventral, and ventral tail) and habitat background across b) the categorical percentage of vegetation cover; and c) age (adult and juvenile) of shore skinks. Bars represent 95% confidence intervals

Figure 5

Color pattern trends of adult shore skinks at Tāwharanui. Mean color values (hue, saturation, and brightness) for body regions (dorsal, ventral, and ventral tail) and habitat background across a) seasons and b) sexes. Bars represent 95% confidence intervals