Lone changer: Fish camouflage better without friends nearby
Fish feel calmer and more secure in groups: Have less need to hide

Date:
October 14, 2021
Source:
University of Sydney
Summary:
While gobies aren't the only fish with camouflage abilities, new
research shows that their colour change is influenced by their
social context: they transform faster and better when alone. This
is likely an adaptive, stress response to perceived threat from
predators - with possible application to other camouflaging species.



FULL STORY ==========================================================================
It's like a half-hearted dress up party: gobies don't camouflage
completely in groups, new research finds. They change colour to avoid
detection by predators and do so faster and better when alone.


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In the research, published in Royal Society Open Science, University
of Sydney academics suggest this is because lone fish are more
vulnerable. They add that camouflage has a metabolic cost, so gobies
likely preserve this energy when, due to safety in numbers, they don't
need it as much.

"Grouping behaviour can reduce stress in fish, partly because they are
in less danger of attack by predators. This 'safety in numbers' effect
may allow them to change colour more slowly without added risk," lead researcher Miss Stella Encel said.

"Since stress hormones like cortisol and adrenaline are central to
the neurological mechanisms of colour change in fish, it's possible
that stress levels also directly affect their ability to camouflage."
The presence of other individuals having a calming effect is known as
'social buffering'. It has wide-reaching physiological and psychological benefits for many species, including humans. For example, people with
rich and supportive social networks have been found to live longer
and enjoy a lower risk of cardiovascular disease than their lonelier counterparts. Meanwhile, rats exposed to new environments are less
fearful when accompanied by a friend.

Testing gobies in black & white Miss Encel, a PhD candidate in the School
of Life & Environmental Sciences, and her supervisor, Professor Ashley
Ward, visited Narrabeen Lagoon, Sydney from August last year. There,
gobies are subject to predation by many larger fish and wading birds,
which means they have a great need for camouflage.



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They collected gobies from mud, sand, and gravel flats in shallow areas
and then, in a lab, tested the gobies -- alone and in pairs -- against
black and white backgrounds (which they had previously acclimated the
fish to). Over time, they used Adobe Photoshop to measure the RGB values
(a mathematical model for colour) of each fish and the background against
which it was tested.

After statistically analysing the results, they found that changes in
body colour plateaued within about three minutes. However, when the fish
were alone, they were able to match their background much more closely
and did so more quickly than in pairs.

Miss Encel said: "Very few studies have examined the role of social
context in influencing colour change in camouflaging animals, and
these have often been done without the benefit of modern colour analysis techniques. So, not only does our study build knowledge of goby behaviour;
it could inform research on the thousands of other camouflaging animals."
Goby facts Goby is a general term to describe thousands of species
of small to medium bottom-dwelling fish from the family Gobiidae, the
largest family of fish.

Gobies are spread all over the world in tropical and temperate near shore- marine, brackish, and freshwater environments.

They are widespread: on coral reefs, for example, they constitute 35
percent of the total number of fishes. In Australia, they are found in
coastal waters from southern Queensland to Victoria.

They grow to a maximum size of 3.5cm in length and generally choose to
dwell on darker surfaces that enhance their camouflage abilities.

========================================================================== Story Source: Materials provided by University_of_Sydney. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Stella A. Encel, Ashley J. W. Ward. Social context affects
camouflage in
a cryptic fish species. Royal Society Open Science, 2021; 8 (10)
DOI: 10.1098/rsos.211125 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211014102032.htm

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