Herds of Dinosaurs and Bison

Herds of Dinosaurs and Bison

In 1978 western Montana was the site of a remarkable discovery: the fossilized remains of 15 baby Maiasaura ("good mother lizards"). The presence of numerous eggshell fragments and of many very young dinosaurs indicated a nest. The young dinosaurs had well—worn teeth and were too large—three feet long—to have been newly hatched. The implication is, therefore, that the young stayed together for some time because they were being cared for by their parents. Food would have been brought to the nest, for if the young left to search for food, they would not likely return to a nest abandoned by parents.

This picture of dinosaurs is not surprising. Crocodiles, distant relatives of the dinosaurs, show considerable care of their young. The parents move hatchlings to nursery pools and guard them against predators until they are large enough to defend themselves.

Further excavation and exploration of the Montana nest sites uncovered numerous nests at different levels, evidence that the Maiasaura returned year after year to rebuild their nests and raise their young. Each nest lay about 23 feet from the others, the length of an adult. The nesting colonies must have been enormous because the herds migrating to this area were, according to recent discoveries, also enormous. Scientists have uncovered the remains of an entire herd in the vicinity of the nesting site; all died simultaneously 80 million years ago.

Under the direction of John Horner of the Museum of the Rockies in Boseman, Montana, seasonal exploration and excavation were continuous during the 1980s. Researchers uncovered a massive bed of maiasaur bones, with an estimated concentration of up to 30 million fossil fragments covering an area 1.25 miles wide and .25 mile long. Without exception all of the bones were of Maiasaura. These were the remains of a single herd, conservatively estimated at no fewer than 10,000 dinosaurs.

The layer of volcanic ash that rested just above the layer of bones tells us what happened. The eruption of Mount St. Helens in 1980 produced a widespread, devastating ash fall; such volcanoes were run—of—the—mill in the Rockies of the Maiasaura's time. The entire herd fell victim to the gases, smoke, and ash of a huge eruption. Since researchers found no evidence of scavengers or predators gnawing on the bones, the eruption doubtless also killed everything else around. Imagine a feeding carpet of dinosaurs staring in confused disbelief as an enormous choking black cloud of volcanic ash swept over them. In a few seconds there remained only a huge killing field strewn with the corpses of 10,000 dinosaurs under a soft cover of volcanic ash. Soon the stench of rotting corpses would have been overpowering. Until the ever—present insects cleaned the remains, it must have been one heck of a mess.

Perhaps surprisingly such a great herd of maiasaurs survived on just sedges and berry bushes, common vegetation of that time. By comparison the bison, which numbered at least 60 million in the early 19th century, ate nothing but grass. The demise of the maiasaur herd was small stuff compared with the fate of a larger, more recent herd of bison. They also lived in the state of Montana but 80 million years later.

The American bison, incorrectly called buffalo, measures 60 to 70 inches at the withers and weighs almost a ton. It is a powerful beast, and the slightest movement of its shoulder muscles reveals a fantastic potential energy that defies comparison to that of any other living creature. Bison enclosed behind huge tree—trunk fences may remain docile, almost immobile, prisoners for months. Then suddenly, with no apparent warning, they will smash the barrier as if it were made of matchsticks.

During the mid—1800s the bison herds were so large that trains were known to wait for days as an entire herd crossed the railroad tracks. Their numbers were so vast that nobody thought or believed they could ever become extinct. Perhaps even nature thought so.

In February 1858, Montana's unusually harsh winter seemed to reach a climax. A blinding blizzard had been raging for days. The migrating herd of bison knew instinctively that they must keep moving, and move they did. None dared lie down to rest. The vanguard of the herd perceived only a whirling, swirling mass of snow. The howling of the wind was continuous and deafening, and visibility varied from a few feet to a few yards. With the entire landscape blotted out and blended into the white opaque air, the bison headed blindly against the storm and swirling wind. They stayed very close together, and each individual could see only the hind legs and rumps of bison immediately in front of it.

The frontline bison received no warning, no variation in color of the snow or furious movement of the snow—flecked air to alert them to any change in terrain. Even had they been aware of the precipice, however, those in front could not halt because of the formidable pressure of thousands of animal engines behind. Like a carpet shoved off a ledge, the entire herd streamed over the precipice.

Nothing could have prevented this catastrophe. The wind howled so furiously that the animals couldn't possibly hear the noise of those before them tumbling one over the other from a height of more than 150 feet. Without exception, all 100,000 of them walked off the cliff to their deaths. The vast assemblage of their carcasses spread over hundreds of acres. It was a true killing field—and eventually a boneyard awesome even to seasoned men of the mountains.

In the days when bison herds roamed the west, the loss of 100,000 bison at one strike was of little significance. They had no real enemies except wolves, Native Americans, and the elements. One herd might have disappeared, but a thousand other herds survived. And so the bison lived on through all seasons, overcoming all difficulties, surviving for centuries. It was as though the American bison were immortal.

Then one fine spring day the white hunter arrived.

From the book: 
Petrified Lightning