New research on this little-known and much endangered genus of agamid lizard, which is found only in the tropical lowland and mountain cloud forests of Sri Lanka, is poised to shed a great deal of light on these creatures’ unusual horns.
Some other agamids have ornamentation including throat sacs or crests, like the burst of reptilian sunshine that is Lyriocepahlus scutatus (see picture below). The rarest ornaments, however, belong to the closely related Cerataphora lizards: Four of the five species have a horn on their noses that vary in size and shape depending on the species and sex.
Despite their odd appearance, few studies have been done on these unique lizards, two of which are endangered and three of which are critically endangered, according to The National Redlist 2012 of Sri Lanka.
And the functions of these horns, scientists are discovering, might be as different as the horns themselves.
What’s in a Horn?
Ruchira Somaweera, a zoologist at the University of Sydney and principal investigator in the yearlong field study, which is funded by the National Geographic Society, said the data is still being analyzed, but the primary hypothesis is that the horns are used in communication within specific species.
Somaweera and his team focused mainly on the critically endangered leaf-nosed lizards (C. tennentii) and found that on these and on rhino horn lizards (C. stoddartii), the males of both species can move their horns slowly at a 45-degree angle while opening their mouths in a threat display.
This may aid in communication between males, he said.
For some species, Somaweera said, the fact that both sexes have horns but they’re larger in males, might mean they have a role in attracting mates: For example, males with bigger horns could be more appealing to females.
Another theory is that the horns may be a form of camouflage helping the reptiles blend into their environment. This theory applies mainly to the leaf-nosed and rough-horned lizard (C. aspera), which may be able to blend in among twigs and leaves on the forest floor. (See “Colorful New Lizard Identified in Vietnam.”)
Adaptable Lizards
As different as their faces are, these lizards’ choices of habitat vary greatly as well. That’s why the team is also researching how lizards, especially C. tennentii, choose where they live, which includes factors such as climate, prey availability, and lack of human threat.
Ceratophora lizards’ current distribution—and scarcity—is shaped largely by historical and current agricultural practices, Somaweera said.
During the late 18th century, “expansive forest cover in Sri Lanka’s central mountain regions began to give way to ‘colonial landscape,’ including land used for cultivation of coffee and then tea, destroying most of the historic range of the rhino-horned C. stoddartii,” he said.
For the leaf-nosed C. tennetii, which is found only in the Knuckles mountain range, the current culprits of habitat loss are tea, pine, and cardamom plantations, he said.
He also said that Sri Lanka has a high population density, “by far the highest among the global diversity hotspots.” In the wet zone where Ceratophora lives, it’s approximately double the national average. The growing population means more land is needed for agriculture and other endeavors.
“On a positive note,” Somaweera said, “our work shows that these lizards are quite adaptable, and as long as there is sufficient canopy cover and [climatically favorable] pockets remaining, they could maintain stable populations in these disturbed habitats.”
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