Native people living in the ancient city of Teotihuacan, now a World Heritage site located in modern-day Mexico, likely bred rabbits to eat and used their bones for tools, researchers said Wednesday.

The study in the open-access journal PLOS ONE represents one of the first known examples of small mammal breeding in an indigenous culture that existed from the first to the seventh century AD.

"Because no large mammals such as goats, cows or horses were available for domestication in pre-Hispanic Mexico, many assume that Native Americans did not have as intensive human-animal relationships as did societies of the Old World," said lead author Andrew Somerville, a researcher at the University of California, San Diego.

"Our results suggest that citizens of the ancient city of Teotihuacan engaged in relationships with smaller and more diverse fauna, such as rabbits and jackrabbits, and that these may have been just as important as relationships with larger animals."

Many archeological excavations have been done at the site, which covers eight square miles (20 square kilometers) and was home to some 100,000 residents, making it the largest urban center of its time, said the study.

Analyses have shown that wild rabbits were among the most common mammals there, making up 48 percent of all identified fauna remains near a residential compound called Oztoyahualco.

Evidence of animal butchering was found in several rooms, where "high soil phosphate levels in the floor suggest the presence of disintegrated fecal matter or blood from butchering," said the study.

Researchers found obsidian blades, multiple rabbit foot bones and low stone walls that may have been used as pens for keeping rabbits.

There is also "a unique stone sculpture of a rabbit" in a nearby public courtyard.

The study said many of the rabbits were likely acquired through the practice of garden-hunting. 

Villagers would have nabbed rabbits from fields where squash, maize and beans were grown. Similar practices were seen in other pre-Hispanic societies of the era.

But saving their crops was not the only reason for the high number of rabbit remains, the study said.

Stable carbon and oxygen isotope analysis of 134 rabbit and hare bone specimens from the ancient city and 13 modern wild specimens from central Mexico showed that those inside the compound were eating more human-farmed crops, such as maize, suggesting that people were feeding them and raising them in Oztoyahualco.

"The specimens with the greatest difference in isotope values came from a Teotihuacan complex that contained traces of animal butchering and a rabbit sculpture," said the study.

That means people were likely feeding the rabbits excess maize and other crops, and breeding them for food, thereby "converting excess carbohydrates into high quality protein and economically valuable secondary products, such as fur, hide, glue and bones for tools."

Source: AFP