Createspace Independent Publishing Platform Field manual of wildlife diseases - general field procedures and diseases of birds, paperback/j. christian franson

• O stea, bazat pe 1 voturi

DO WILDLIFE DISEASES REALLY MATTER? The waterfowl manager who wakes up one morning to find ten thousand dead and dying birds in the marsh would think so.

Yet virtually every wild bird and mammal harbors at least a few parasites seemingly without obvious adverse consequences.

Parasites, viruses, bacteria, and fungi are component parts of the ecosystems in which wildlife are found, but do not necessarily cause disease.

Millennia of coevolution have engendered a modus vivendi that assures the survival of both host and parasite populations.

Then why the ten thousand sick and dying birds? Ecosystems are changing.

Waterfowl are concentrated on shrinking wetlands and remain there for longer periods of time, facilitating bird-to-bird spread of the bacteria that cause avian cholera.

Or permitting the buildup of parasites in their hosts from a small, relatively benign number to massive numbers that cause disease and death.

Water quality of wetlands changes, favoring the production of deadly botulinum toxin by bacteria and its mobilization up the food chain to waterfowl.

New, totally artificial habitats are created with unpredictable results.

The extreme temperature, salinity, and other conditions of the Salton Sea have created an unusual ecosystem in which botulism occurs in fish and in birds through biological cycles that are not yet understood.

Wetland loss in southern California leaves few alternative places for waterbirds to go, so they are attracted to the Salton Sea.

Behavior changes.

Mallard ducks take up residence on the ponds and lakes of city parks and lose their migratory habits.

They share these bodies of water with exotic species, such as Muscovy ducks that have also taken up residence there after introduction by people, setting the scene for outbreaks of duck plague, and creating the risk of spread to migratory waterfowl that also use these areas.

Raccoons and skunks become well adapted to urban life, bringing rabies and canine distemper with them into the city.