ITHACA, N.Y. -- A continent-wide network of bird-feeding enthusiasts have helped researchers at the Cornell Laboratory of Ornithology prove a long-standing theory that a naturally occurring disease can regulate a wildlife population.
The findings, from a study of mycoplasmal conjunctivitis in house finches (Carpodacus mexicanus) that was published May 2, in Proceedings of the National Academy of Sciences, could give scientists insight into the dynamics of other host/disease systems as well, including an epidemic currently affecting fish in the Chesapeake Bay -- and possibly even AIDS.
"Our data showed that high-density populations of house finches that became infected with mycoplasmal conjunctivitis experienced a dramatic drop in numbers within two to three years after the epidemic began and that they stabilized at about 40 percent of their previous abundance," says co-author Andr Dhondt, director of Bird Population Studies and professor of ecology and evolutionary biology at Cornell. "At the same time, emerging house finch colonies increased to approximately those same levels, despite the presence of the disease."
Theoretically, says Dhondt, it makes sense that when a disease emerges in a dense population, it moves quickly through that population and wipes out vast numbers because healthy individuals have a higher chance of coming in contact with infected animals. Conversely, healthy animals in lower-density populations are less likely to cross paths with infected individuals, allowing those populations to continue to grow until the disease reaches a density threshold.
This theory, however, had never before been demonstrated because it is extremely difficult to follow the course of a naturally occurring wildlife disease. Scientists need information on host abundance both before, during and after the epidemic sweeps through the population. They also must begin collecting data at the onset of the disease. To do that, symptoms need
Contact: Allison Wells
Cornell University News Service