Geoscience Reference
In-Depth Information
Part of this situation was because wolves killed and ate some of these glut-
tonous plant munchers, but they also managed to exert a sort of mind control over
their prey. For instance, once wolf packs had hunted elk over several generations in
this area, these herbivores restricted themselves to eating vegetation only in certain
places, and skittishly, with the threat of death as a big motivator for not hanging out
in any one place and browsing too long. This fear factor even caused elk to have
smaller families, as the added stress of possible predation triggered hormones that
decreased female-elk fertility. With fewer elk, and elk eating less, plant communit-
ies expanded and became more contiguous. This effect even helped wolves' super-
friends, grizzly bears, which then had lots more berries to eat during lean times. In
short, wolves helped to change the ecosystems around and in Yellowstone National
Park for the better, and as a result riparian plants there breathed a sigh of oxygen-
laden relief.
Now imagine this situation with theropods as the predators—whether as pack
hunters, or carrying the biomass of a dozen wolf packs in a single body—and herds
of big herbivores as prey. Transfer these same concepts to their Mesozoic ecosys-
tems, in which certain predators kept certain herbivores in check, preventing them
fromstayinginanyoneplaceandeatingtoomanyplants.Considerallofthehealed
bite marks, other toothmarks, gut contents, coprolites, and other trace fossils that
tellusaboutpredator-preyrelationsbetweendinosaursatdifferenttimesduringthe
Mesozoic. Then multiply these trace fossils by millions to recreate what must have
happened over more than 150 million years, and envisage the aggregate effects of
predators on herbivores in their plant-filled ecosystems.
Also contemplate how Mesozoic streams may have changed their dynam-
ics—flow patterns, erosion rates, and flooding—according to a presence orabsence
of predatory theropods. Lastly, visualize how riparian plants, flowering or other-
wise, then thrived and were more able to pass on their genes to future generations.
If any or all of these scenarios happened, then these are additional subtle but large-
