04 April 2014

Lizard Love Colors

Welcome back. Did you hear that an advice-to-the-lovelorn columnist in Australia received a note from a just-married guy asking about his new wife’s belly? It seems her belly changes color from white to orange when she’s feeling romantic. It kind of freaks him out, and he wanted to know what he should do.

Lake Eyre dragon lizard (Ctenophorus
 maculosus
) from 2 minute video
 aso.gov.au/titles/tv/sunburnt-country/clip2/
Well, if that story is true--and I’m not saying it is--the note was probably written as a gag by a bored herpetologist, filling in for a male Lake Eyre dragon lizard (Ctenophorus maculosus). I say this because there’s a recent paper about a study of how the females of that lizard species signal their reproductive status by their behavior, of course, but also by changes in ventral (abdominal, belly) color.

Lizard Life

Australia has several very large salinas--arid region salt lakes that rarely fill with water though there may be residual smaller sub-lakes. Lake Eyre, or more properly Kati Thanda-Lake Eyre, is the largest as well as being the continent’s lowest elevation.

The lake’s salt crusted shores, with wind, dust storms, temperatures often exceeding 100 deg F and no shade or fresh water, are the Lake Eyre Dragon lizard’s habitat.

Based on earlier studies of the lizard, the males are expected to make greater efforts to court females that are reproductively mature and sexually receptive, which might be advertised by female behavior and coloration.

Non-receptive females are white, but during the breeding season, mature, receptive females develop intense orange abdominal color patches, which don’t fade or become speckled until they lay eggs. (A repeat performance is possible during the same breeding season.)

Color versus Behavior

To examine the relative influence of female behavior and color, researchers from Australia’s University of Melbourne conducted experiments with 34 female and 27 male, reproductively mature lizards, in glass tanks that provided sand, salt crust, moisture, heat and ultraviolet (UV) light to simulate as closely as possible the lizards’ natural habitat.

In the first experiment, the researchers painted (yes, painted) females with colors that matched spectrally (including UV) the three general stages of reproductive cycle: (1) non-receptive, when females are white and exhibit “appeasement” behaviors; (2) receptive, when females develop orange coloration and accept the males, and (3) gravid (pregnant), when females are not receptive, exhibit rejection behaviors but retain the orange color.

In the second experiment, designed to assess male behavior toward females that differed in color but not in reproductive stage, the researchers painted non-receptive (white) females in four different treatments: large, small and pale orange patches and orange patches with no UV.

Wrap Up

The study found that female coloration did indeed signal information that influences male courtship decisions. The males generally chased, bit and mated more with orange than with white females at any reproductive state, though they mated more frequently with receptive females. Courting preference was for females with small orange patches, especially those that were intensely colored rather than pale, regardless of the presence of UV.

It’s kind of dicey for me to extrapolate the study results beyond herpetology. Whatever I say might sound off color. I suppose I could suggest that showing your true colors might not always be wise or that you should choose your colors wisely. I could go on about dressing for success, but that’s a horse of a different color. Thanks for stopping by.

P.S.

Research study in Frontiers in Ecology and Evolution journal:
journal.frontiersin.org/Journal/10.3389/fevo.2014.00002/full#B5
Science Daily article on study: www.sciencedaily.com/releases/2014/02/140227164524.htm
Background on Lake Eyre: en.wikipedia.org/wiki/Lake_Eyre
Background on Australian lizards: www.publish.csiro.au/pid/6604.htm

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