Cuttlefish dynamic camouflage: responses to substrate choice and integration of multiple visual cues

Abstract

Prey camouflage is an evolutionary response to predation pressure. Cephalopods have extensive camouflage capabilities and studying them can offer insight into effective camouflage design. Here, we examine whether cuttlefish, Sepia officinalis, show substrate or camouflage pattern preferences. In the first two experiments, cuttlefish were presented with a choice between different artificial substrates or between different natural substrates. First, the ability of cuttlefish to show substrate preference on artificial and natural substrates was established. Next, cuttlefish were offered substrates known to evoke three main camouflage body pattern types these animals show: Uniform or Mottle (function by background matching); or Disruptive. In a third experiment, cuttlefish were presented with conflicting visual cues on their left and right sides to assess their camouflage response. Given a choice between substrates they might encounter in nature, we found no strong substrate preference except when cuttlefish could bury themselves. Additionally, cuttlefish responded to conflicting visual cues with mixed body patterns in both the substrate preference and split substrate experiments. These results suggest that differences in energy costs for different camouflage body patterns may be minor and that pattern mixing and symmetry may play important roles in camouflage.

Figure 1.

Illustration of set-up for substrate preference experiment on (a) artificial and (b) natural substrates showing arena, substrates and dividers. (c) Illustration of split substrates experimental set-up (top view). Note the position of cuttlefish (drawings are not to scale).

Figure 2.

Substrate preference experiment: results with representative images; pie graphs show percentages of trials in which cuttlefish sat on each substrate. (a) Artificial substrates; images left to right: on grey (U), small checks (M), large checks and centre. (b) Natural, glued substrates. (c) Natural, loose substrates (depth: 1 cm of same substrates). (d) Natural, deep substrates (depth: 4 cm of same substrates). For b, c and d, images left to right: sand (U), small shells (M), large shells (D) and centre. Abbreviations: U, Uniform; M, Mottle and D, Disruptive.

Figure 3.

(a) Split substrates experiment: results of image analysis for images of cuttlefish on six different substrates. Control substrates (Uniform, black; Mottle, dark grey; Disruptive, light grey) are shown with broken lines; experimental split substrates (Uniform/Disruptive, dark grey; Mottle/Disruptive, black; Mottle/Uniform, light grey) are shown with solid lines. See text and Barbosa et al. (2008b) for details of image analysis. Error bars are standard deviation. (b) Representative images of cuttlefish sitting on control substrates: (i) Uniform, (ii) Mottle and (iii) Disruptive; and experimental split substrates: (iv) Uniform/Disruptive, (v) Mottle/Disruptive and (vi) Mottle/Uniform.

Figure 4.

Cuttlefish Sepia officinalis showed no strong substrate preference except when they could bury themselves. This behaviour can be seen in the laboratory as well as in the field. (a) Field image of a cuttlefish buried in soft substrate. (b) Same field image; a box is drawn around the animal's body and an arrow points to the right eye to indicate cuttlefish location.