Choosing the Best Camouflage Pattern

 

So how do cuttlefish choose which camouflage tactic they want to use? The environment a cuttlefish is in determines which body pattern it will display (Shohet et al., 2007). Thus, visual input plays a significant role in how cuttlefish change their color and patterning in response to their environment. They use a two part process to determine the 3D environment they are in and then make a decision on which coloration and pattern to use (Kelman et al., 2008; Zylinksi et al., 2009).

1) First, cuttlefish detect separate retinal image cues such as edges, object size, and depth (Kelman et al., 2008).

2) Then they use these visual cues to determine their 3D environment and make a decision on which body color and pattern will be most effective (Kelman et al., 2008).

So which one to choose?:

If there are distinct objects with distinct edges and features in the background, studies have shown cuttlefish will display disruptive patterning. This was seen in both the laboratory and the wild (Kelman et al., 2008; Zylinksi et al., 2009). These findings indicate that cuttlefish have "edge detectors," allowing them to discriminate between different objects in the background (Kelman et al., 2008). The ability to distinguish objects from their background is thought to be similar between cuttlefish and vertebrates (Zylinksi et al., 2009).

Choosing the best camouflage
Night Camouflage
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Experimental Studies conducted on the effect of environment on camouflage choice in cuttlefish

A study done by Kelman, Osario, and Shohet indicates that shadows play an important role in camouflage and cuttlefish have some sense of depth perception. When pale areas were placed in front of dark areas, disruptive patterning was promoted because it appeared as though there were distinct objects in the background. But when dark areas were placed in front of pale areas disruptive patterning wasn't exhibited because it didn't appear as though there were distinct objects present (Kelman et al., 2008). From these findings, Kelman concluded that cuttlefish have depth perception similar to humans, in that pale objects appear to be in front of shadows (Kelman et al., 2008).

 

Another experiment conducted by Shohet, Baddeley, Anderson, and Osorio compared the camouflage used by the European cuttlefish (Sepia officinalis) with that of the Pharaoh cuttlefish (Sepia pharonis). These two species of cuttlefish live in very different environments in the wild. The European cuttlefish lives in temperate waters that are turbid, whereas the Pharaoh cuttlefish lives in tropical waters that have a low turbidity. In this study, the cuttlefish were exposed to black and white checkerboards that differed in the size, contrast, number, and area of white squares on the black background. The Pharaoh cuttlefish used background resemblance (sometimes in combination with disruptive patterning) more often than the European cuttlefish (see Figure 1). In contrast, the European cuttlefish responded to the differing backgrounds by switching between background resemblance and disruptive patterning, but displayed the disruptive more frequently. These findings are consistent with what one would expect based on the different habitats these two species live in. Disruptive camouflage is more effective over shorter distances because the eye is drawn to the pattern on the animal and away from the outline of the animal. But at greater distances, background resemblance is more important. So, it makes sense that the Pharaoh cuttlefish would exhibit background resemblance more often since it lives in tropical waters, where the visibility is high. European cuttlefish on the other hand live in turbid waters where visibility is low, so it is better to use disruptive patterning (Shohet et al., 2007). Thus, it is clear that the environment is integral in determining which camouflage pattern cuttlefish exhibit.

 

officinalis pharonis

Figure 1. Reproduced with permission from Dr. Osorio. A comparison of the Sepia officinalis (left) and Sepia pharonis (right) responses to a fine gravel substrate. Here, the Pharaoh cuttlefish is utlizing a background resemblance pattern more effectively than the European cuttlefish. This supports Shohet et al's. hypothesis that the Pharaoh cuttlefish must exhibit background resemblence more often and effectively due to the environment it lives in. Background resemblance is less important for the European cuttlefish since it lives in more turbid waters, where the visibility is lower than that of the tropical waters the Pharaoh cuttlefish lives in (Shohet et al., 2007).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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