TPO 29 # 1

The article provides three arguments to support the hypothesis that edmontosaur , one of the most common North slope dinosaurs, survived in the winters by migrating south to more hospitable regions. The professor opposes this hypothesis and says that it is not convincing.

First, the reading states that the edmontosaur's diet supports the migration theory because they left the slope at least part of the year to find food on more temperate zones. The professor counters this point and explains that they do not have to migrate to find plants since the North slope regions were warmer than today and the sun used to shine 24 hours a day creating good growing condition for plants. Therefore, he adds that when the winter came, there were so much nutrition form died plants on the ground available for these dinosaurs to feed on.

second, the author points out that many edmontosaur skeletons have been discovered from the same site which suggests that they live in herds and migrate like others herds. The professor casts doubt on this point and illustrates that living in herds do not mean they migrate because there are other benefits from living in groups. He mentions that they could live in herds to get extra protection from predators when they live the whole year on one place. He gives an example of rosvelt elks that live in herd in Western US and do not migrate to support his interpretation.

Third, the reading claims that These kind of dinosaurs had the capability to run fast and move to far distance. Although the professor demonstrates that the young donsaurs could not run fast as much as the adults. As a result they could slow down the herd migration and the adults could not leave them because they were unable to survive alone. Therefore, they adult were more likely to stay together in the same place in arctic slope with their youngers in cold winter.