Description
1. Although background matching decreases prey detectability, resemblance
between camouflaged prey and their visual background is seldom perfect.
This could be because even a moderate resemblance might provide sufficient
protection, and additional adjustment of colour pattern might give little
benefit. Alternatively, close resemblance to background may not be
attained due to trade-offs or constraints. To understand selection on
colour patterns of camouflaged prey and the existence of inaccurate
background matching, it is necessary to investigate how detectability of a
colour pattern varies with its resemblance to the background. 2. We
trained wild-caught blue tits (Cyanistes caeruleus) to search for
artificial prey. We manipulated the resemblance of the artificial prey
items to the visual backgrounds. 3. For the first half of the twelve
repeated prey presentations we found a non-linear relationship between
resemblance and detectability, such that for prey that had high background
matching, a change in resemblance resulted in a larger change in
detectability than an equal change in resemblance did for prey with lower
background matching. However, for the second half of the presentations
this relationship was linear. Moreover, in a two-patch-type habitat a prey
pattern that was a compromise between the two different backgrounds did
after few initial presentations equally well as the prey pattern that
matched highly one of the backgrounds. 4. Our results indicate an intense
selection for close matching in a single background. Yet, in the
heterogeneous environment that consisted of two backgrounds the
compromise, which only loosely resembled either background, provided good
protection. Therefore, we conclude that cryptic colour patterns that bear
only a loose resemblance to a given background, and thus represent
inaccurate background matching, may be adaptive outcomes.
Search times for background-matching preyData on blue tits'
(Cyanistes caeruleus) search times for artificial, cryptic prey items on
two different backgrounds (a or b). The colour pattern of the prey
consisted of 4 black shapes, but the prey differed with respect to how
closely they resembled the patterning of the two backgrounds. The number
of elements that match backgrounds a and b are used to describe prey
appearance. Thus for example 3:1 means that the prey had 3 shapes that
were found in background a and 1 shape that was found in background b.
Each of the 70 birds received 12 subsequent presentations of one prey type
and in one background type only. The data show the 12 search times (in
seconds) for each individual (s1, s2,...s12).searchtimes.txt
between camouflaged prey and their visual background is seldom perfect.
This could be because even a moderate resemblance might provide sufficient
protection, and additional adjustment of colour pattern might give little
benefit. Alternatively, close resemblance to background may not be
attained due to trade-offs or constraints. To understand selection on
colour patterns of camouflaged prey and the existence of inaccurate
background matching, it is necessary to investigate how detectability of a
colour pattern varies with its resemblance to the background. 2. We
trained wild-caught blue tits (Cyanistes caeruleus) to search for
artificial prey. We manipulated the resemblance of the artificial prey
items to the visual backgrounds. 3. For the first half of the twelve
repeated prey presentations we found a non-linear relationship between
resemblance and detectability, such that for prey that had high background
matching, a change in resemblance resulted in a larger change in
detectability than an equal change in resemblance did for prey with lower
background matching. However, for the second half of the presentations
this relationship was linear. Moreover, in a two-patch-type habitat a prey
pattern that was a compromise between the two different backgrounds did
after few initial presentations equally well as the prey pattern that
matched highly one of the backgrounds. 4. Our results indicate an intense
selection for close matching in a single background. Yet, in the
heterogeneous environment that consisted of two backgrounds the
compromise, which only loosely resembled either background, provided good
protection. Therefore, we conclude that cryptic colour patterns that bear
only a loose resemblance to a given background, and thus represent
inaccurate background matching, may be adaptive outcomes.
Search times for background-matching preyData on blue tits'
(Cyanistes caeruleus) search times for artificial, cryptic prey items on
two different backgrounds (a or b). The colour pattern of the prey
consisted of 4 black shapes, but the prey differed with respect to how
closely they resembled the patterning of the two backgrounds. The number
of elements that match backgrounds a and b are used to describe prey
appearance. Thus for example 3:1 means that the prey had 3 shapes that
were found in background a and 1 shape that was found in background b.
Each of the 70 birds received 12 subsequent presentations of one prey type
and in one background type only. The data show the 12 search times (in
seconds) for each individual (s1, s2,...s12).searchtimes.txt
| Date made available | 13 Jan 2014 |
|---|---|
| Publisher | DRYAD |
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