Cannibal 'T. Rex' Ants Seen Live for 1st Time Ever (and They're Shy)

Tyrannomyrmex rex is a timid, finicky eater, new research finds. The ants can, however, turn to cannibalism in times of need.

Until now, these Asian ants were a complete mystery to science, despite being discovered more than 20 years ago. No one had ever collected more than a single specimen, and no one had ever observed a T. rex ant alive for an extended period of time. So when biologist Mark Wong stumbled across a colony of T. rex ants while conducting an ant diversity survey in Singapore, he knew he had something important.

He and his colleague Gordon Yong from the National University of Singapore carefully collected the colony, which consisted of 13 workers, as well as eggs, larvae and pupae (the liminal stage between larva and adulthood). They then observed the ants in an attempt to figure out what makes them tick. Because the study is the first of its kind, everything the researchers discovered is new, Wong told Live Science. [See Stunning Mug Shots of Ants Across the Globe]

Chance discovery

The T. rex ant was first discovered in Malaysia in 1994. It's part of the rare group of ants in the Tyrannomyrmex genus; there are only two other identified species. (T. dux from India and T. legatus from Sri Lanka.) The ants have pointed snouts, which may explain the T. rex namesake, Wong said.

In March 2016, Wong found the first known live colony of T. rex ants in a piece of rotting wood stuck in the ground in Singapore's Mandai area, just south of Malaysia and north of the Singapore Zoo. The ants were nesting in a second-growth forest that was once the home of 20th-century orchards and rubber plantations, Wong and Yong reported April 27 in the journal Asian Myrmecology.

In the field, it was apparent why the T. rex ant is so little-known. The colony was small, subterranean and unobtrusive. Ant collection methods rarely involve careful underground surveys, Wong said.

"Our finding of T. rex below the ground surface highlights the need for more focused exploration of the ant communities within this environment," he said.

Timid T. rex

In captivity, the colony further exhibited the retiring manner that has made these ants so elusive. They were more active at night than during the day, suggesting that they are probably nocturnal in the wild, Wong said. They are not aggressive. When exposed to a potential threat, like a millipede, the ants curled up and froze, likely hoping to be overlooked so they could run away when the immediate danger passed.

Despite offering the ants an absolute smorgasbord of food, Wong and Yong could not determine what the ant version of T. rex eats. They rejected termites, smaller ants, mites, millipedes and even honey, Wong said. When shown a drop of honey, they kept their distance, except for a tentative poke at the sticky substance with their antennae. [In Photos: Trap-Jaw Ant Babies Grow Up]

Besides the 13 adult workers, the T. rex colony consisted of two worker pupae, one male pupa, nine larvae and five eggs. The male pupa emerged as an adult two days into captivity, but the other ants immediately ate him. It was "unfortunate," Wong said, but not unheard of.

"The colony is one big organism," he said, "and this is one way in which it channels resources from some biological functions [in this case, reproduction] to others, based on which are deemed important in the prevailing environmental conditions."

After 10 days of observation, the researchers euthanized the ants and preserved their bodies for study. Wong and his colleagues returned to Mandai to search for more T. rex ants, but they have had no luck, he said. He plans to keep looking.

"Increasingly, we're finding that many ants which live underground have unique life histories and ecological relationships that are poorly understood," he said. "There's this amazing world right beneath our feet, which we've hardly explored, and I'm excited to get started."

Original article on Live Science

Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.