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at their backs. They began hopping while flapping their wings, and then were aloft,
chattering loudly. This was all the motivation one of the more skittish theropods
needed to start running, and the rest of his group followed suit. The ornithopods
only hesitated a second or two before doing the same. First, though, more than a
few of both species lightened the load before taking off, involuntarily voiding their
bowels and leaving variably colored and sized scat, peppered with seeds, on top of
their distinctive footprints. In her haste, one
Thescelosaurus
slipped on a muddy
patch and fell on her side. She quickly righted herself and bolted to catch up with
the others, leaving a long, smeared body impression on the sand among the tracks.
Abandof
Mononykus
-liketheropodsbecametoocrowdedneartheedgeofthe
river and, in a moment of desperation, jumped into the water and began swimming.
In the river shallows, their feet touched the bottom and claws on each toe gouged
thesand,makingparallelgrooveswitheachstroke.Bodiesbuoyedbythewaterand
swimming with the current, their tracks were nearly twice as far apart from one an-
other as if they had been on land.
Thesethreeseparate butrelatedshockwaves—the aggressivemovementofthe
big male
Triceratops
, the raucous flocks of birds and pterosaurs, and the panicked
stampede of the theropods and ornithopods—triggered overt and subtle changes in
thebehaviorsofnearlyeverydinosaurnearby.Inthisrespect,itwaslikemanyother
days in the Cretaceous Period, where long periods of quiet stability were occasion-
ally interrupted by near-chaotic commotion.
Onhighergroundabovethefloodplain,amale-femalepairofpredatorythero-
pods (
Dromaeosaurus
) paused from digging up small mammals from out of their
burrows with their rear feet. They raised their heads, looking for whatever had pro-
voked alarm calls from the birds and pterosaurs now passing overhead. Their foot-
prints and excavations had disturbed a considerable amount of soil in the area. But
they had much more to do before leaving. Once convinced the alarming behavi-
or below had nothing to do with them, they went back to uncovering their furry
morsels, sniffing the ground and scraping with their rear feet.
