Fossilized Poop Provides Scoop on ‘Bone-Crushing’ Dogs

Jack Tseng, PhD

Jack Tseng, PhD

Published July 26, 2018

Jack Tseng, PhD, assistant professor of pathology and anatomical sciences, is senior author on a study that looked at fossilized feces to confirm the diet of extinct “bone-crushing” dogs.

“Our discovery and analysis of the coprolites are important for making accurate reconstructions of the ecological roles played by the bone-cracking canids of North America.”
Assistant professor of pathology and anatomical sciences

The ancient canids lived throughout North America about 6 million years ago. Their powerful, heavyset jaws earned them their nickname.

Evidence of Marking Territories

Tseng and fellow researchers from the Natural History Museum of Los Angeles County were able to find 14 extremely rare coprolites — fossilized feces — at a fossil site in central California.

The site is where researchers have found numerous bones from the bone-crushing dog species Borophagus parvus. Coprolites are exceptionally rare — bones are more likely to be preserved than soft tissue or feces.

From studying the fossilized feces, scientists can tell, based on how they were found at the fossil site, that the feces occurred in clusters from multiple individuals and multiple “dropping events.”

This could mean that these dogs were marking their territories, a behavior seen today, but one that has never been documented before in extinct carnivores.

Size of Prey Shows Evidence of Social Hunting

The fossils still contain the partially digested bones of 6-million-year-old meals, such as a bird limb bone and a large mammal’s rib, among others. And while scientists can’t determine which exact species these dogs ate, they can estimate the rough size of the prey based on some of the bones’ measurements.

From the looks of it, these bone-crushing dogs regularly dined on animals many times bigger than themselves, which suggests they were hunting in groups to accomplish this. Social hunting might also explain why they ate so much bone: If mealtime is a competitive sport, there’s really no time to pick and choose each bite carefully.

Bone-crushing dogs went extinct around the time the Ice Age was setting in, about 2 million years ago. The special bone-eating role they played in these ancient ecosystems was never replaced, so their absence may have had an outsized effect on the ecosystems they were once a part of.

Learning Ecological Roles Extinct Species Had

Tseng says discoveries like these coprolites help scientists get a clearer picture of what life was like and how ecosystems functioned long before humans arrived on the scene.

“Our discovery and analysis of the coprolites are important for making accurate reconstructions of the ecological roles played by the bone-cracking canids of North America,” he says.

“Those top dogs looked like they could crack a lot of bones (based on anatomy), and we know that no modern predators in North America resemble the extinct canids, so having coprolites to confirm those speculations really solidified the idea that these predators were unlike any other we have seen.”

Tseng says this means amongst the megafauna lost during the Ice Age, a type of predator that could have had a significant impact on continental food webs as they are known today was lost.

Bone-Cracking Mechanically Demanding Task

Tseng says he also is interested in understanding anatomical features as engineered tools.

“Bone-cracking is one of the most mechanically demanding tasks an animal can do,” he notes. “After all, large predatory mammals are made of the same flesh and bone as those of their prey, so their ability to crack bones requires ingenious rearrangements of the functional anatomical traits produced by evolution under natural selection.”

“On a broader level, we paleobiologists like to know if extinct species played similar ecological roles as living species, and if not, what that tells us about worlds of the past and the world we live in at the present,” Tseng says.

Natural History Museum Curator Lead Author

The study, “First Bone-Cracking Dog Coprolites Provide New Insight Into Bone Consumption in Borophagus and Their Unique Ecological Niche,” was published online May 22 in the journal eLife.

Lead author was Xiaoming Wang, PhD, curator of the Natural History Museum of Los Angeles County, where Tseng is a research associate.

Co-authors on the paper were from the following institutions:

  • American Museum of Natural History, New York City
  • California State University, Fullerton
  • California State University, Stanislaus
  • Natural History Museum of Los Angeles County
  • University of California, Los Angeles

The National Science Foundation and the University of California, Los Angeles, funded the study.