Predators-Group1

“Deep in the wilds of Venezuela, the natural order is being turned inside out. Miles of verdant forest and savannah have given way to small and scattered islands. Some of these islands are now overrun by bands of voracious howler monkeys, a glut of iguanas and hordes of ravenous ants. What is driving this bizarre transformation? A team of scientists believes that life here has run amok in large part because its top predators are gone. Similarly, the majestic wilderness of Yellowstone National Park is also showing signs of change that some scientists trace to the depletion of natural predators. Familiar and revered forests have vanished. Researchers are linking these forest losses to the expulsion of the gray wolf some seventy years ago. In Venezuela and around the world, experts are learning that predators seem to play a crucial role in the structure and function of entire ecosystems. When the predators disappear, the consequences can be dramatic. If predators are so vital, should they — and can they — be brought back?”

//**Group 1: Predator Loss at Lake Guri**// · Describe the transformations in the plants and animals at Lake Guri. · What event caused the loss of predators at Lake Guri and Caroni Valley Venezuela? · What are some advantages and disadvantages to this event? · Where in Arizona did this same event happen?

You guys need to summarize the video first. Tell what happened in your section before you answer questions.
__Summary__: In the Video, the whole island of Lake Guri was being flooded. Every animal on the island is in danger of being killed. Only animals who can stay in the treetops can survive. A group of researchers try to save the animals by taking the animals and transferring them into a different habitat. Only 9000 animals were saved. Back then, there were a bunch of animals and predators. The predators ruled the land, but when humans came and killed the predators, the prey overpopulated.

Answers: 1. The transformations of the animals and plants at Lake Guri were most of the population of predators died off and most of the plant life died off. But only the toughest plants survived, armed with thorns and poisonous toxins. 2. The event that caused lots of damage at Lake Guri was a flood from a dam. The dam was used for scientists to study electricity. The dam got out of control and most of an ecosystem that was in Lake Guri. 3. The advantages that we get from this event are, that we get electricity. The disadvantages that we get from this event were the dam ruined a whole recreational park. 4. The type of situation that happened at Lake Guri, also happened at Glen Canyon Dam in Arizona. The lack of water in Glen Canyon is crippling many species in the surrounding ecosystems and has forced a decline in the health of the animals in the Glen Canyon. Though, the costs of the Glen Canyon haven't only effected those in the U.S., but have also impacted Mexico as well.

When they made the dam at Lake Guri and at Glen Canyon it was to create a hydro-electric power system. When they did this it flooded the whole area where Lake Guri is located, and it completely filled in Glen Canyon with water. This destroys the ecosystem. Here are more details about the video from the Strange Days website. http://www.pbs.org/strangedays/episodes/predators/experts/lakeguri.html "Every time ecologist [|John Terborgh] visits Lake Guri, he and his team members, including [|César Aponte] and [|Luis Balbás], document significant changes to the life on these islands. They suspect that as the floodwaters created these islands, a key group of animals fled – the big predators. In their absence, their prey began wreaking havoc. According to Terborgh, the predators haunt the place by not eating their prey. On one island, iguanas are living at 10 times normal densities. On another, howler monkeys are living at 50 times higher density than on the mainland. And these normally vociferous primates are completely silent in such overcrowded conditions. On a different island, leaf-cutting ants are living at 100 times their normal numbers. Only the toughest plants now survive on these over-grazed quarters and these survivors are heavily defended with thorns or chemicals.

Lake Guri presents a classic example of a top-down mediated system wherein the removal of top predators initiates a cascade of effects on other populations – mainly the prey species and their food supplies. For example, predators keep prey populations at levels below the population size that would be observed in the absence of predators. On the other hand, if factors such as food and/or habitat availability are the main influences driving population fluctuations, that population is said to be regulated by bottom-up (resource) processes. In truth both processes often regulate populations, either through a seasonal or temporal shift from one process to the other, or when both processes act in concert." 60/75 points