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Fashion-conscious lizards show animal colour bias


Attempts to get up close and personal support species confidence hypothesis.


A western fence lizard displaying its characteristic blue colouring.
A western fence lizard displaying its characteristic blue colouring.
Danita Delimont / Getty

Here’s a handy tip: if you want to catch a western fence lizard (Sceloporus occidentalis), found through the US southwest and Pacific northwest, wear a dark blue tee-shirt.

That’s the take-home message from research conducted by Breanna Putman from the University of California, Los Angeles, and published in the journal PLOS ONE.

Putman set out to see if the colour of clothing she wore influenced how close she could get to the lizards before they fled, and how easy they were to catch after they took flight.

In doing so, she was testing an animal behavioural idea known as the “species confidence hypothesis”, which holds that various animals are more likely to tolerate the approach of a human if the person’s clothing matches in part its own skin or plumage colour.

The idea is not without support. In 2004, for instance, researchers at Australia’s primary science body, the CSIRO, tested it on a species of bird called the Spiny-cheeked Honeyeater (Acanthagenys rufogularis). They found they could get much closer to the birds when wearing shirts that were bright red, a colour found in honeyeater plumage, rather than yellow ones.

Western fence lizards, also known as blue-belly lizards, have dark blue patches on their throats and chests used for signalling.

Putman experimented with approaching lizards – some living around humans, others residing in a largely human-free nature reserve – while wearing dark blue, light blue, red and grey shirts. She tested each shirt colour 30 times.

The results provide strong support for the species confidence hypothesis.

When she wore a red top, the lizards tended to zip off when she got to within 2 metres. When she wore the dark blue number, that distance contracted to 1 metre.

Furthermore, while wearing the blue shirt she was able to catch the running lizards 84% of the time; her success rate dropped to 42% in the red.

She suggests her findings may have implications for eco-conscious hikers and ramblers. Wearing colours that encourage species confidence could minimise anxiety caused when humans trek through wilderness.

“What we wear can have indirect effects on animals through changes in their behaviour,” she says.

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Andrew Masterson is an author and journalist based in Melbourne, Australia.
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