Mastodon dung reveals diet, environment in Nova Scotia some 75,000 years ago

Three decades after researchers recovered mastodon remains from a Nova Scotia gypsum quarry, the find is generating new insights into the species' habitat in the days before one of the elephant-like animals fell into a sinkhole and died, around 75,000 years ago.

Thanks to a small, rock-like specimen of dung, scientists have reconstructed the animal's diet and environment, concluding the mastodon was a browser — largely staying in a forest setting taking in shrubs and boughs, but also insects, pollen and algae.

Scott Cocker, now a PhD student at the University of Alberta, led the research and is publishing the findings in the Canadian Journal of Earth Science.

"They gave us a view of a time in Nova Scotia 75,000 years ago. The plants were fairly similar to what we see in Nova Scotia today," Cocker told CBC News.

"Lots of spruce, there's birch, there's alder. A mixed forest, spruce dominant, where we still have lots of hardwoods like oak. And also there were wetlands, still freshwater wetlands in the area."

More importantly, he said, is what the mastodon accidentally consumed while browsing.

Analysis revealed the earliest known Canadian remains of a bark beetle. The dung also contained remnants of a freshwater sponge. Its size indicated the mastodon was feeding in late summer or early fall.

"We're picking up other kinds of microorganisms that all ended up being in the water or happened to be on the trees they're eating," Cocker said.

"And so that's what actually gives us the perfect picture. Because if we just were reconstructing based on what [the animal] meant to consume, we're getting a really small picture of what is actually going on."

Half a cup of dung

Cocker obtained a 50-gram chunk — about half a cup — of dung, which he broke down in a weak solution of hydrochloric acid, and sifted the parts through a series of sieves.

The specimen was released by the Nova Scotia Museum of Natural History in Halifax, which houses the partial skeletal remains of two mastodons found in East Milford, N.S., in 1990-91. In addition to bones and dung, researchers found two turtles and a frog at the site.

Tim Fedak, geological curator of the museum, said the dung is an ecological archive.

"What I was really struck by was just the sheer diversity of plant and insect life that he [Cocker] was able to reconstruct from that small sample that we provided to him," Fedak said.

"You can imagine this mastodon walking down from a highland area down into a lowland and just grabbing some spruce boughs and chomping those down, and there happen to be bugs on them and some seed cones and things.

"So you just get a really great snapshot of that particular environment at that time."

Sifting for clues 

Cocker said the dung specimen and other research indicates this was likely an optimal period for mastodons, providing a baseline of conditions prior to their extinction around 13,000 years ago, after the last ice age.

"The only way we can really understand extinctions is by looking back to understand how past animals and plants lived," he said. 

"What kind of environments they lived in, how they functioned ecologically. What happened? What were the factors that drove that change? Was it climate, was it a changing environment? Was it pressure from humans?"

What tooth enamel can reveal

The search for clues to understand extinction is also motivating research by Laura Eastham at Saint Mary's University in Halifax.

She is carrying out isotope testing on tooth enamel from the jawbone of one of the East Milford mastodons.

Chemical analysis can tell when it reached maturity, whether it was drinking freshwater from a glacial stream or a lake, whether it migrated a long distance over its lifetime and whether its diet changed.

"I'm doing that not only because it's really interesting to understand what these fossil mammals were doing, but also because looking at how they were reacting to changing climates tells us a lot about how modern species might react to climate change," Eastham said.

"So that's going to help us constrain modelling and also help us inform how we develop conservation strategies."

Fedak said new techniques are allowing scientists to look at specimens in new ways.

"There'll be people looking at these specimens 100 years from now, I'm sure, with even more new tools and questions," he said.