Research Areas
Nearly all animals have some sort of adaptive coloration or camouflage patterning that is often linked to a behavior to make it adaptive.
Some of the functions of adaptive coloration include:
- defense against predators,
- communication with conspecifics,
- attracting or deceiving mates,
- repelling or deceiving rivals,
- signalling alarm to conspecifics and so forth,
- protection from the environment (e.g., ultraviolet radiation, cold), and
- approaching prey
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Camouflage
A primary defense against predators throughout the animal kingdom (and against the enemy during human warfare) is to avoid detection or recognition through camouflage. Achieving effective camouflage requires a suite of appropriate actions by an animal:
- sensing the local environment (including the animals in it),
- filtering the sensory input,
- using selected sensory input to make a behavior decision,
- directing the appropriate effectors (be they muscles/postures/color patterns, etc.) to achieve some form of camouflage, and
- implementing the appropriate behavior to render the camouflage effective.
How many kinds of camouflage are there?
There is still active debate on how to best "categorize" camouflage. Generally the tactics involve hindering or preventing detection or recognition. Some of the generally accepted mechanisms of camouflage include:
- general background resemblance (or "background matching,"
- deceptive resemblance (or "masquerade" including mimicry),
- disruptive coloration,
- countershading/concealment of the shadow.
Other mechanisms include self-shadow concealment, obliterative shading, distractive markings, flicker-fusion camouflage, motion dazzle and motion camouflage. Ongoing research worldwide is occurring on many of these features.
Cephalopods: ultimate adaptive coloration?
A distinguishing feature of cephalopods is that individual animals can change their appearance with a speed and diversity unparalleled in the animal kingdom: we term this “rapid, neurally controlled polymorphism.” Some squids, octopuses and cuttlefish can show 30-50 different appearances. In fact, these marine invertebrates manifest most aspects of their behavior through body patterning. An example of their versatility is that – unlike other animals that use one or a few mechanisms of camouflage – cephalopods use most of the mechanisms listed above.
Sensory/motor mechanisms of achieving adaptive coloration in cephalopods
Due to their sophisticated neural control of the skin, cephalopods can adapt to a wide range of backgrounds. What sensory cues do they use to achieve background matching? Vision is probably the main cue, but cephalopods do not seem to have color vision. We are currently investigating the mechanisms and functions of polarization sensitivity in cephalopods. We have also begun to look at visual features of the background that cuttlefish use to switch on disruptive coloration.
Tactile cues seem not to be used by cuttlefish for regulating their skin texture - vision seems to be used. Olfactory cues are used by cuttlefish females to choose mates, yet we do not know if/how this translates to certain body patterns for communication. Read more about skin ultrastructure and neurobiology in the next section.
How do you study camouflage?
Field work is mandatory to experience and understand the dynamic features of light throughout each daily, lunar, seasonal, and yearly cycle. Field work also enables observation and analysis of animal behavior under natural conditions. Laboratory experiments provide detailed testing of sensory cues, motor output and sequences of behavior. Computer simulations allow additional testing of hypotheses at multiple levels of analysis.