Gender-coded messages in colourful throat displays of lizards
doi:10.1038/nindia.2017.60 Published online 29 May 2017
India’s spectacular male fan-throated lizards send out multiple messages when they wave their colourful throat flaps during breeding season. Other members of the species are then able to pick the message intended specifically for their gender, new research suggests1.
The fan-throated lizard (Sarada superba) was first described last year as endemic to the semi-arid plateaus of India’s Western Ghats. The species weighs only 3–5g, fitting into the palm of your hand, and many live only a year. Between February and March these compact reptiles turn from juveniles to adults within a month and then they eat, fight and mate until the seasons change.
Robotic lizards used to test colour-coded messages
During their short summer breeding season the males attract attention by sitting on rocks and flapping brightly coloured flaps of skin beneath their jaw known as dewlaps. Daubed with orange, black and iridescent blue patches, the colours communicate important information about their health and aggression levels to potential female mates and male competitors.
Since lizards have eyes on either side of their head, researchers Amod Zambre and Maria Thaker from the Centre for Ecological Sciences at the Indian Institute of Science, Bangalore placed a live lizard in a glass tank with robotic lizards on either side. They then tested different colour combinations, recording which way the lizard turned, finding distinct preferences based on gender.
What the lizard’s colours are saying
“When given a choice between blue and orange dewlaps, 80% of males chose blue dewlaps while 100% of females chose orange dewlaps. When given a choice between black and orange dewlaps, 85% of males chose black dewlaps whereas 90% of females chose orange dewlaps,” the authors noted.
Thaker says “differences in their preferences for individual colours suggests that colours contain distinct pieces of information”. Orange, usually made from a diet of yellow, orange or red pigments known as carotenoids, probably helps the female assess the health of males, their territory quality and foraging success.
Blue, however, has to be made during a lizard’s sexual development, and may relate more to aggression levels. Males also enhance this blue on their front, back and the sides of their tails in male to male interaction.
Black, which is a very high-contrast shade and thus often used to communicate important information, may also convey information about aggression levels.
1. Zambre, A. M. & Thaker, M. Flamboyant sexual signals: multiple messages for multiple receivers. Anim. Behav. 127, 197–203 (2017) doi: 10.1016/j.anbehav.2017.03.021