The ‘poop’ on ‘bone-crushing’ dogs


Published May 29, 2018

headshot of Jack Tseng.

Jack Tseng, assistant professor of pathology and anatomical sciences, was senior author on a recent study led by Xiaoming Wang of the Natural History Museum of Los Angeles County that examined the coprolites — fossilized poop — of extinct “bone-crushing” dogs. Tseng talks to UBNow about the research and what it tells us about how ecosystems functioned millions of years ago.

Why is this research important and what gaps in knowledge does it fill in?

JT: 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. 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, either before or after their reign in North America. This means amongst the megafauna lost during the Ice Age, we also lost a type of predator that could have had a significant impact on continental food webs as we know it today if those species were still around. This finding places additional importance on the ecological role of bone-cracking canids that was not emphasized in prior studies.

Does this research tell us anything about the planet’s future?

JT: This research supports recent findings that ecological communities of North America as we know it have undergone dramatic changes very recently, on a geologic scale. This further supports the idea that we don’t have a stable baseline on which to base our long-term decisions about how we preserve or manage nature on this continent. This highlights the importance of ongoing research (emphasized at UB by programs such as RENEW) to understand how we got where we are today in terms of the environment we inherited, and hopefully that will in turn inform how we move into the future.

Why are you interested in knowing whether or not these dog descendants were bone-crackers?

JT: Personally, I am very interested in understanding anatomical features as engineered tools. Bone-cracking is one of the most mechanically demanding task an animal can do. 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.

This research will attract enormous interest, not just because of the poop but because it concerns dog descendants. Does this tell us anything about contemporary dogs or characteristics they inherited?

JT: I LOVE dogs, have had many dogs in my life, but not a single cat. These bone-cracking canids evolved into a lineage totally separate from the lineage containing all living wild and domestic dog species/breeds. We know that three successive waves of canid lineages evolved and replaced each other over the past 40 million years. The fact that species with extreme adaptations, such as the borophagines, died out, and less-specialized canines are the only ones living today suggests that living canids are either very lucky, or they actually possess characteristics that gave them an advantage during extinction events. So, although living dogs may not be as big or as strong as their extinct cousins, they are nevertheless evolutionary winners because they survived. However, as I look out the window into my backyard, I can only imagine the thrill of seeing a borophagine canid cross my yard, instead of the usual suspects (deer and rabbits). Too bad they are extinct!