Research shows wallabies lose on the pokies

January 30, 2014
Research shows wallabies lose on the pokies

( —Biologists have discovered that a wallaby's perception of colour is more similar to a dog than a quokka, sparking questions as to why marsupial colour vision has evolved so selectively.

By developing a pokies-like game for the wallabies, the research – recently published in PLOS ONE by Curtin University's Dr Wiebke Ebeling and colleagues – was able to determine exactly what the animals saw and how their colour perception differed from other species.

"We trained tammar wallabies to respond to different colour stimuli by pressing switches on an automated experimental setup, similar to a poker machine," Dr Ebeling said.

"The most remarkable result was the determination of the 'Neutral Point' which describes a single colour that to wallabies looks identical to white, where the animals cannot make up their mind which switch to choose. In the case of wallabies, this was a shade of cyan (greenish blue).

"The presence of a Neutral Point makes wallabies appear special among . Their vision is more similar to a dog or horse rather than other marsupials, even their close relative the quokka.

"This study has raised new questions as to why good colour vision evolves so selectively and should be beneficial to the quokka but not the ."

Dr Ebeling said the team presented tammar wallabies with a choice between white and different yellows, greens and blues. When choosing the correct stimulus in the experiment, the wallaby would be treated with food, leading to an extremely accurate determination of the Neutral Point.

She said the presence of a Neutral Point, together with results from other colour-mixing and colour discrimination experiments, was typical for 'dichromats' - species with two colour-sensitive photoreceptor types in their retina. Whereas 'trichromats' like humans and other marsupials such as the fat-tailed dunnart, with one more photoreceptor type in their retinas, could not be confused as easily.

"The case of the wallaby is clear-cut now: it's a dichromat, but it still remains a mystery what exactly the additional photoreceptor in other marsupials is and why the wallaby should be the only one to miss it," Dr Ebeling said.

"This diversity will require more research by tracking down the elusive photoreceptor gene and examining the behavioural capabilities of other marsupials to confirm other species as trichromats."

She said behavioural experiments allowed shy and night-active species like the tammar wallaby to participate on their own terms and reveal their perception of colours.

"Our wallabies learned quickly and seemed to enjoy working on the machine and often did not bother actually eating the food - they just played for the fun of it," Dr Ebeling said.

Explore further: Tammar wallaby’s clever immune tricks revealed

More information: Ebeling W, Hemmi JM (2014). "Dichromatic Colour Vision in Wallabies as Characterised by Three Behavioural Paradigms." PLoS ONE 9(1): e86531. DOI: 10.1371/journal.pone.0086531

Related Stories

Tammar wallaby’s clever immune tricks revealed

July 11, 2011

( -- Until now, it was a mystery why many marsupials have two thymuses—key organs in the immune system—instead of the one typical of other mammals. Now postdoctoral researcher Dr. Emily Wong from the ...

The climb to the pouch begins in utero

March 18, 2013

Scientists have visualised the short pregnancy of a small species of the kangaroo and wallaby family of marsupials, the tammar wallaby (Macropus eugenii), for the first time by high-resolution ultrasound. The study has shed ...

The first kangaroo genome sequence

August 19, 2011

Kangaroos form an important niche in the tree of life, but until now their DNA had never been sequenced. In an article newly published in BioMed Central's open access journal Genome Biology, an international consortium of ...

Recommended for you

An epigenetic key to unlock behavior change

October 16, 2017

When it comes to behaviour, researchers have moved beyond the "nature versus nurture" debate. It's understood that genes and environment both play a role. However, how they interact at a molecular level to shape behaviour ...

Unexpected finding in the cell's power plant

October 16, 2017

Researchers at Karolinska Institutet have discovered that the protein complex RNase P in the cell's mitochondria behaves differently than previously thought. The findings, published in Nucleic Acids Research, give important ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jan 31, 2014
another nail for those strange people that like to insist that humans are the only animal that likes to have a good time.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.