Mass Wildlife Die-Off Events
On New Year's Eve, over 3,000 red-winged blackbirds inexplicably plummeted to their deaths from the skies over Arkansas. They may have struck something while in the air such as lightning or hail. It is also possible that the ground itself caused their deaths, and they were merely rendered unconscious while flying by some mysterious force. According to the USGS National Wildlife Health Center and the Arkansas Game and Fish Commission, they were spooked into flying into trees and houses.
On the last day of the year, officials believe, the birds were startled by loud noises (fireworks, parties?). This caused them to fly erratically into objects on the land. The USGS team conducted necropsies (animal autopsy) on the dead blackbirds and found internal hemorrhaging, the kind caused by impact trauma. Tests for pesticides in their systems came up negative.
Mass die-offs may seem rare, but according to the USGS, they are not entirely uncommon. "Although wildlife die-offs always pose a concern, they are not all that unusual," said Jonathan Sleeman, director of the USGS NWHC in Madison, Wis., which is completing its analyses of the Arkansas and Louisiana birds. "It's important to study and understand what happened in order to determine if we can prevent mortality events from happening again."
Last year, there were eight wildlife die-off events in which over 1,000 birds died suddenly. In the past ten years, there were 188 such events in the United States. The largest took place in Utah where 50,000 birds died of avian botulism. In Idaho, 20,000 died of the same disease, and in Washington 10,000 died from a toxic algal bloom.
Other wildlife can also be subject to a mass mortality event, such as the prairie dogs in the American West. A single colony can be completely destroyed by sylvatic plague. The prairie dog deaths then affect the endangered black-footed ferret which preys on them. The USGS is working to administer plague vaccinations to the prairie dogs through bait.
Even though mass die-off events are common, none should be ignored. The diseases that often cause them could pose harm to human populations. The USGS National Wildlife Health Center is actively involved in investigation each incident, looking for diseases like West Nile virus or Avian Influenza. Through greater understanding, it is possible to contain and even prevent such events from occurring.
For more information on Wildlife Health Events: http://www.whmn.org/wher/