Results (
Thai) 1:
[Copy]Copied!
MANAGEMENT OF PLANT AND ANIMAL POPULATIONS IN PROTECTED AREASControlling Exotic SpeciesExotic species introduced into PA's can cause major problems. Predatory animals e.g. dogs, cats, rats etc. prey on rare local species, which may not be able to escape or avoid them. Introduced herbivores can cause plants to go extinct. For example in New Zealand many plants have gone extinct due to the introduction of red deer from Europe. Usually exotic species should be eliminated from PA's unless they are themselves threatened with extinction. Hunting, trapping and poisoning are the methods used, but care must be taken not to harm native animals. Poisoning, for example, is not very specific. Exotic plants can also cause problems by out-competing the local flora. They may be controlled by fire, cutting, herbicides or biological control. Overabundant Native AnimalsSometimes native animals can become so numerous that they threaten the survival of rarer species. For example in Africa the elephant is a threatened species, but in some parks there are too many and they destroy the vegetation on which many other species depend, so they have to be CULLED (killed to reduce the population in a controlled way).The manager of a PA must ask why an animal species has become too abundant. Sometimes this occurs when the predator of a species has been eliminated from a PA. In this case Man must take over the job of the predator or the predator must be re-introduced. Will the over-abundant species destroy the vegetation? Or will it compete with a much rarer species for food and other resources? The manager should check the age structure of the over- abundant species to determine if its population is continuing to increasing or has stabilized. If it is increasing and the manager decides to reduce the population, then he has to decide on what methods to use: shooting trapping, poisoning or biological control (i.e. re-introduce the missing predator). There will normally be public opposition to killing wild animals in a PA, especially large mammals and especially if the species is rare elsewhere. In such cases it is better to TRANSLOCATE the animals to areas where the species is not so common.Problems Caused by Animals Leaving PA'sWhen the population of a species within a PA reaches carrying capacity, young individuals will tend to disperse outwards in search of new areas of suitable habitat in which to establish territories. Such animals may conflict with surrounding farmers, especially if the animal damages crops (e.g. elephants) or kills livestock or people (e.g. tigers). There are several options open to the PA manager in such a situation:i) encourage the animal to stay inside the PA by providing extra food or other resources,ii) erect barriers - fences (use interlocking netting rather than horizontal strands), grids across roads, moats or ditches,iii) make a BUFFER ZONE of unsuitable habitat around the edge of the PA - e.g. eucalyptus plantations (animals are unlikely to cross through a eucalyptus plantation to leave a PA because it provides no food and local people can harvest wood from the plantation),iv) shoot or trap animals leaving the PA,v) pay financial compensation to farmers who have their crops damaged by animals leaving the PA.Rare SpeciesBefore management decisions concerning rare species can be made, research must be carried out to determine which species are rare. What is the population density of the rare species? Is the population increasing or decreasing? This can be determined by looking at the age structure of the population. A population with many young ones and few older individuals is increasing whereas a population in which most individuals are old is probably decreasing. If the population is decreasing, then the factor causing the decline must be identified and appropriate action taken e.g.:i) not enough food? - provide extra food at feeding stations (SUPPLEMENTARY FEEDING),ii) predation or competition? - reduce predator or competitor populations by culling,iii) disease? - capture and quarantine infected individuals; prevent dispersal of infected individuals into disease-free areas; vaccination (but very difficult in practice,iv) lack of breeding sites - build artificial breeding sites (mostly used to provide nest sites for rare birds)iv) infertility due to inbreeding? - artificial dispersal andv) population so sparse that males cannot find females? - translocation or captive breeding.Only when these measures fail should the species be removed from its natural habitat for captive breeding and eventual re-introduction.
Being translated, please wait..
