December 12, 2011 § Leave a comment
Gone with the wind: the dinosaurs who kicked up a stink
It would have been a sight to take Sir David Attenborough’s breath away: herds of huge, long-necked dinosaurs known as sauropods made an annual migration like the wildebeest of the Serengeti, scientists have discovered.
Camarasaurus made a noisy, smelly, 200-mile migration each year to find food
Herds of Camarasaurus, a herbivore that grew to a maximum length of 23m (75ft), would have cut a swath of destruction as they trudged almost 200 miles from the plains to the mountain in a cacophony of noise — not least from their flatulence as they digested their food. “I think it would have been rather slow going, with animals eating as they walked, maybe only going a few kilometres a day at most as they headed uphill before turning around and heading downhill again,” said Henry Fricke, of Colorado College, who led the research.
“I also imagine that herd size couldn’t be very large — in the 10s to low 100s — or else there wouldn’t be enough vegetation to support and sustain them.
“Perhaps at this pace juveniles could keep up and could be protected from predators by staying near their huge parents. Lastly, I imagine a lot of noise — rustling of trees as leaves are eaten, and lots of farting: sauropods didn’t chew — they did all of their digesting in their gut.”
While scientists have long suspected that sauropods may have migrated in regions with dry seasons in similar fashion to the many modern herbivores that travel long distances to find food and water, this behaviour has been difficult to prove.
However, a chemical analysis of the teeth of Camarasaurus fossils from the western United States, dated to about 145 million years ago, has found compelling evidence that the dinosaurs indeed made such seasonal migrations.
Many chemicals, such as oxygen, come in different forms known as isotopes, which vary in abundance according to environmental factors such as wetness and altitude. The ratio of such isotopes in tooth enamel can thus be used to work out characteristics of the habitats in which the creatures fed.
A team led by Dr Fricke has used this technique to show that Camarasaurus lived both in the plains where their fossils were found, and in mountains around 300km (186 miles) away.
The isotope data shows that the dinosaurs must have been drinking water from these high-altitude regions — and thus that they migrated between the lowlands and highlands. Details of the research are published in the journal Nature.
Dr Fricke said that the most likely explanation for the migration was that the dinosaurs left the arid plains during the dry season for mountain slopes where there was more water and vegetation. “We hope to test this idea by studying Camarasaurus populations from less arid environments to see if they exhibited similar migratory behaviour [or not],” he added.
The researchers are studying whether teeth from predatory dinosaurs found at the same sites have the same isotope signatures, which could indicate that they followed their prey’s migrations.
“It will be very interesting to see if they actively followed sauropods as they migrated, or whether they appear to have had specific home ranges that they occupied, and then preyed on what happened to wander through them,” Dr Fricke said.
Camarasaurus means “chambered lizard”, because of the hollow chambers in its vertebrae. The largest species of Camarasaurus, C. supremus, grew up to 23m and weighed an estimated 47 tonnes. Most of the specimens analysed for the study were from C. lentus, which grew to about 15m (49ft).