Animals will contort their bodies into all sorts of peculiar shapes in an attempt to attract a mate (have you ever seen Brits dancing abroad?), and in some species there is a fine line between what’s considered sexy and what’s just frightening. The toad-headed agama (Phrynocephalus mystaceus) – a lizard that gives Stranger Things' Demogorgons a run for their money – is one such species.
Agamas can unfurl their vibrantly-colored cheeks to create a spiky display rather like a flower that’s grown teeth, and such flashes of coloration are often tied to courtship displays (have you seen the tiny, twirling, blue arms of Carnotaurus?). However, new research published in the Biological Journal of the Linnean Society suggests that instead these fierce face flaps are a means of telling predators to back up.
“Conspicuously coloured signals may evolve via sexual selection to be ornaments or armaments, thereby conferring a fitness advantage to their bearer,” said the authors, quite poetically, in their paper.
“Conversely, conspicuous colours may also evolve under natural selection as either [warning] signals or [startle] displays that deter attacks from predators. While conspicuous colour patches may evolve for one purpose (e.g., quality indicators), they may later be co-opted for another (e.g., anti-predator defence).”
To better understand what motivated the agamas to flare their cheek flaps, researchers captured some in China’s Tukai so they could observe their interactions in arenas. They recorded 14 male-male pairs and 17 female-female pairs but saw no cheek action indicating they’re not used against competing mates.
Trials between males and females also seemed to demonstrate that these cheek flaps had no place in the species’ courtship, as, while there was lots of tail wagging going on, nobody flared the face.
However, when shown images of predators, things started to change. First, they were shown a flying falcon image, which largely caused the animals to flee, though 3 percent got their cheeks out. That percentage jumped to 12 when they subbed the hawk pictures for actual free-roaming lizards.
An attack from dental floss eventually proved to be the biggest cheek instigator, as lassoing lizards in an ambush triggered 84 percent of those observed to respond with what the researchers suspect is a startle display. How this would prove effective is that the flaps are tucked away when the lizard is at rest, so should an agama find itself in the clutches of a predator it may be able to spook them by suddenly transforming its appearance.
A particularly memorable fight scene from the latest series of Stranger Things certainly springs to mind when imagining an agama unfurling its face before a foe, but as for how effective it is in reality? The researchers say there’s more work to be done.
Currently, we need more empirical studies testing the predictions of deimatic display theory and how context may influence an animal’s decision to deploy a deimatic display,” they wrote.
“Our experiments and measures of anti-predator responses were very much focused on the perspective of potential prey. The next stage is to test the response of a potential predator to establish whether the display does indeed induce a startle response by overwhelming their sensory system.”