The thorny devil (Moloch horridus) is also known as the thorny dragon or the mountain devil. It’s a small (up to 8 inches in length), spiky lizard native to Australia. They live in the arid scrubland and desert of the interior of the continent. Thorny devils are the only species in the genus Moloch, and they can live between six and 20 years.
Thorny devils have a number of defenses against predators and specializations for living in the desert. But do they live up to their name of devil? Read on to find out.
1. They are named after a human sacrifice god. The thorny devil’s scientific name, Moloch horridus, was inspired by John Milton’s poem “Paradise Lost.” In the poem, Milton describes the Caananite god Moloch as a horrible king smeared with the blood of human sacrifice. The Latin word horridus can mean rough or bristly, or dreadful.
2. They specialize in eating ants. Thorny devils are what’s known as obligate myrmecophages: they eat only ants. They can consume thousands of small, black ants a day. Thorny devils are “sit-and-wait” predators who find a feeding site near ant trails and wait for their prey to pass right in front of them. They use their sticky tongues to capture the ants. Their teeth are modified to deal with the hard, chitinous bodies of their prey, with the mandibular teeth fitting neatly between two maxillary teeth to create a shearing tool in their mouths.
KeresH, via Wikimedia Commons. Distributed under a CC-BY-SA-3.0-2.5-2.0-1.0 license 3. Thorny devils are covered in spikes. Their heads and bodies are covered in densely-packed spikes, each no bigger than the thorns of a rose. These spikes are thought to make predators think twice before attempting to swallow a thorny devil.
4. They can puff themselves up to appear bigger. Thorny devils have another defense mechanism in which they inflate their chests with air to make themselves bigger and harder for a predator to swallow.
5. They have a funny walk. The thorny lizard’s unusual gait entails walking slowly, stopping often, and rocking back and forth. This characteristic slow, shaky movement appears very deliberate. Presumably, their jerky movements and frequent freezing in place helps conceal them if a predator spots them out in the open.
6. They deposit distinctive fecal pellets. Thorny devil droppings are glossy, black prolate spheroids. They crumble easily to reveal the exoskeletons of their ant prey. Individual thorny devils tend to have specific defecation sites away from their basking and feeding sites, and they may return to the same site for several days.
7. Thorny devils can change color. In warm weather, the lizards are usually pale yellow and red, but they can change rapidly to darker colors in cold weather or when alarmed. They undergo this color change daily as the sun rises and they become more active. In the cool morning, thorny lizards are a drab olive-brown and get lighter as the temperature climbs.
8. Thorny devils don’t like extreme hot or cold. Thorny devils have a bimodal seasonal pattern of activity. They are almost completely inactive during the hottest summer months (January and February) and the coldest winter months (June and July), when they take refuge in underground burrows. Thorny devils are active in the autumn (March, April, and May) as well as the later winter through early summer (August – December), during which they mate and lay eggs.
9. Thorny devils have a “false head” on their shoulders. Thorny devils have a strange, knob-like appendage on the backs of their necks, which is sometimes called a false head. When threatened, the lizard can tuck its real head down between its forelegs, leaving the false head where its real head used to be.
By Wouter!, via Wikimedia Commons. Distributed under a CC-BY-SA-3.0 license
10. They concentrate and drink dew. Not only does their spiny armor protect them from predators, it also helps them absorb water in their arid habitat. There are hygroscopic (moisure-attracting) grooves between their thorns. They obtain water from the dew that condenses on their bodies overnight, during rare rainfalls, or by brushing up against dew-coated grass. Any water that gets into the grooves between its thorns is drawn by capillary action to its mouth, allowing the thorny dragon to suck water from all over its body.
References and Other Resources:
Bentley, P. J. and F. C. Blumer. 1962. Uptake of water by the lizard, Moloch horridus. Nature 194: 699–700.doi:10.1038/194699a0
Dewey, T. 2009. “Moloch horridus” (On-line), Animal Diversity Web. Accessed August 10, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Moloch_horridus/.
“Moloch horridus (Thorny Devil): (On-line), Encyclopedia of Life. Accessed August 10, 2014 at http://eol.org/pages/791432/details.
Pianka, E. R. Australia’s thorny devil. (On-line), Accessed August 10, 2014 at http://uts.cc.utexas.edu/~varanus/moloch.html.
Pianka, E. R. and H. D. Pianka. 1970. The ecology of Moloch horridus(Lacertilia: Agamidae) in Western Australia. Copeia 1970: 90-103.
“Thorny Devil (Moloch horridus)” (On-line), Arkive. Accessed August 10, 2014 at http://www.arkive.org/thorny-devil/moloch-horridus/.
Withers, Philip. 1993. Cutaneous Water Acquisition by the Thorny Devil (Moloch horridus: Agamidae). Journal of Herpetology. 27(3): 265-270.
