Self Tutorial 7: Role of Predators Versus the Use/Control of Predators: Monday 8H30-9H30 29-30Th October
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Self Tutorial 7: Role of Predators versus the use/control of Predators: Monday 8h30-9h30 29-30th October Videos "When we try to pick out anything by itself, we find it hitched to everything else in the Universe." - John Muir (Noted Preservationist). Contrast this to Conservationist Gifford Pinchot who believed that natural resources should be used for the benefit of humanity - “the greatest good of the greatest number [of people] for the longest time.” (See First Week Lecture). When wolves were reintroduced to Yellowstone National Park in the United States after being absent nearly 70 years, the most remarkable "trophic cascade" occurred. What is a trophic cascade and how exactly do wolves change rivers? George Monbiot explains in this movie remix. https://www.youtube.com/watch?v=ysa5OBhXz-Q When whales were at their historic populations, before their numbers were reduced, it seems that whales might have been responsible for removing tens of millions of tonnes of carbon from the atmosphere every year. Whales change the climate. The return of the great whales, if they are allowed to recover, could be seen as a benign form of geo-engineering. It could undo some of the damage we have done, both to the living systems of the sea, and to the atmosphere. https://www.youtube.com/watch?v=M18HxXve3CM Based on the documentary watched in class entitled “Strange Days on Planet Earth - Part 3 of 4 - Predator” https://www.youtube.com/watch?v=SIXAytRvDQ0&t=1771s This is a series of videos described as the following: Around the globe, scientists are racing to solve a series of mysteries. Unsettling transformations are sweeping across the planet, and clue by clue, investigators around the world are assembling a new picture of Earth, discovering ways that seemingly disparate events are connected. Crumbling houses in New Orleans are linked to voracious creatures from southern China. Vanishing forests in Yellowstone are linked to the disappearance of wolves. An asthma epidemic in the Caribbean is linked to dust storms in Africa. Scientists suspect we have entered a time of global change swifter than any human being has ever witnessed. Where are we headed? What can we do to alter this course of events? National Geographic's Strange Days on Planet Earth, premiering in Spring 2005 on PBS, explores these questions. Drawing upon research being generated by a new discipline, Earth System Science (ESS), the series aims to create an innovative type of environmental awareness. By revealing a cause and effect relationship between what we as humans do to the Earth and what that in turn does to our environment and ecosystems, the series creates a new sense of environmental urgency. It has four parts. Part 3 dealt with predators and their role in ecosystem maintenance. Summary of the Documentary Deep in the wilds of Venezuela, the natural order is being turned inside out. Miles of savanna and verdant forest have given way to small, scattered islands with the construction of the controversial dam called lake Guri. Fig 1. Lake Guri, Venuzuela, with a surface area of 4,250 square kilometres is one of the largest constructed to generate hydro-electricity. The dam has long been the focus of much controversy, because the lake it created forever destroyed thousands of square miles of a forest that was renowned for its biodiversity and rare wildlife, including the only place where the recently discovered Carrizal seedeater (a finch-like tanager) was ever found Some of these islands are now overrun by bands of howler monkeys, a glut of iguanas and hordes of ravenous ants. What's driving this bizarre transformation? and could it be linked to other mysterious events around the world? A team of scientists may have the answers. They believe that life on these islands is running amok in large part because the top predators are gone. In fact, in Venezuela and around the world, experts are learning that predators could play a crucial role in structuring entire ecosystems and when the predators disappear, the consequences may be dramatic. 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 have recently put forth an amazing hypothesis linking these forest losses to the expulsion of the gray wolf some 70 years ago. Wolves were once a vital part of North American ecosystems before bounty hunters, starting at the turn of the century, decimated their numbers. A big question for biologists worldwide is what has been the effect of removing large carnivores? In Yellowstone, researchers have looked for answers in the way wolves impact the ecosystem. This impact starts with their kills. In a lot of ways, a wolf kill is not an ending but a beginning. Every wolf kill becomes an epicenter of animal activity, replete with ravens, magpies, coyotes, bald eagles and grizzly bears that feed on the wolf-kill remains. These kills then become extremely important to the ecological community of Yellowstone. In this way, one wolf kill serves hundreds. Perhaps, even more importantly, by hunting elk in particular, wolves literally may be reshaping the landscape. By keeping elk on the move, researchers say elk spend less time grazing on Yellowstone's aspen and willow trees. Research suggests that the elimination of Yellowstone's wolves allowed the elk to browse aspens and willows unchecked. Though other factors may have played a role, it seems the disappearance of trees and streamside vegetation can, in fact, be traced to the missing wolves. Now, following the controversial reintroduction of wolves to the environment, where elk are on the run, trees and shrubs are starting to make a comeback. It's not just on land that predators appear to be crucial. In the Caribbean, once-vibrant coral reefs are under attack by insidious algae. With the reefs suffocating under shaggy layers of algae, scientists are investigating the role that the loss of top predatory fish such as sharks, groupers and jacks have played in the reef's slow demise. As these large fish were decimated by fisheries, smaller fish became the next commercial target – including those vital grazers that kept fast-growing algae in check. With the grazers gone, the algae were free to take over. In contrast to the above video are the two following papers which are based on the idea that large, charismatic, and predator species represent economic value that can a) support the financing of the conservation and b) support impoverished communities with economic benefits. This is through trophy and sport hunting. Extracts from Publications Sport Hunting, Predator Control and Conservation of Large Carnivores Craig Packer1*, Margaret Kosmala1, Hilary S. Cooley2, Henry Brink3, Lilian Pintea4, David Garshelis5, Gianetta Purchase6, Megan Strauss1, Alexandra Swanson1, Guy Balme7, Luke Hunter7, Kristin Nowell8 1 Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, Minnesota, United States of America, 2 Wildlife Demographics, Logan, Utah, United States of America, 3 Durrell Institute of Conservation and Ecology, Kent University, Canterbury, Kent, United Kingdom, 4 The Jane Goodall Institute, Arlington, Virginia, United States of America, 5 Minnesota Department of Natural Resources, Grand Rapids, Minnesota, United States of America, 6 The Zambesi Society, Bulawayo, Zimbabwe, 7 Panthera, New York, New York, United States of America, 8 Cat Action Treasury, Cape Neddick, Maine, United States of America Abstract Sport hunting has provided important economic incentives for conserving large predators since the early 1970s, but wildlife managers also face substantial pressure to reduce depredation. Sport hunting is an inherently risky strategy for controlling predators as carnivore populations are difficult to monitor and some species show a propensity for infanticide that is exacerbated by removing adult males. Simulation models predict population declines from even moderate levels of hunting in infanticidal species, and harvest data suggest that African countries and U.S. states with the highest intensity of sport hunting have shown the steepest population declines in African lions and cougars over the past 25 yrs. Similar effects in African leopards may have been masked by meso-predator release owing to declines in sympatric lion populations, whereas there is no evidence of over-hunting in non-infanticidal populations of American black bears. Discussion Mortality from state-sanctioned and illegal predator control likely contributed to the overall population declines of cougars and lions; while leopards are also killed as pests, the leopard’s CITES Appendix I status requires international approval for national export quotas, potentially providing safeguards against overharvest. However, leopard exports have declined in some countries, quotas have risen in others, and concerns have been raised over the level of problem animal off-takes and the management of leopard hunting practices. Further, leopard populations in many areas may have been ‘‘released’’ by large scale declines in lion numbers: lions inflict considerable mortality on leopards; consequently, hunting blocks in Tanzania’s Selous Game Reserve with the highest lion harvest intensities showed the largest increases in leopard harvests (P = 0.0059 after controlling for declines in lion off-takes, n = 45 blocks). Thus the full impact of current trophy hunting practices on leopards may not be fully apparent for several more years. Harvest policies for infanticidal species such as lions, cougars and leopards that relied on ‘‘constant proportion’’ or ‘‘fixed escapement’’ could help protect populations but require accurate information on population size and recruitment rates, which are virtually impossible to collect; a harvest strategy of ‘‘constant effort’’ can more easily be achieved by measuring catch rates and regulating client days . Hunting efficiency could be reduced by banning or limiting the use of baits and hounds, but the absence of direct oversight in remote hunting areas would make enforcement difficult.