Understanding How Invasives Do Us Harm

©Lorraine Wozniak

Invasive species are harmful in a number of ways. Many invasive plants change soil chemistry making it unsuitable for other plants. Invasive vines smother and strangle important trees and shrubs. Still others are aggressive spreaders that create monocultures in our woodlands and wild places, outcompeting native flora. These are the ways invasives disrupt healthy ecosystems and displace plants essential for providing food and habitat for birds and other wildlife.

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©Lisa Shirk

Some invasives are extremely harmful to humans. The sap of giant hogweed, for example, contains toxic chemicals that can cause severe burns and risk permanent eye damage if precautions are not taken. Japanese barberry has not only escaped our landscapes to invade woodlands, but it is preferred by white-footed mice seeking shelter in the warmth and moisture of this thorny shrub. White-footed mice are responsible for spreading Lyme disease in North America. The mice infect ticks with the Borrelia burgdorferi bacteria, passed to humans with a bite. According to the CT Agricultural Experiment Station, removing invasive barberry from your property can reduce your risk of tick related illness by as much as 60%.

Eliminating barberry near your home makes good sense. If mice are encouraged to dwell close by, they are likely to find cracks and openings in your home’s exterior, seeking shelter during colder months for warmth, food, and protection from predators.

Sometimes humans seek solutions that actually make things worse. Bait boxes are a perfect example. Bait is meant to be appetizing and to attract. When placed around a building, bait boxes actually bring rodents to your doorstep. And, the poisoned bait does not kill quickly so rodents keep coming back for more. When a victim eventually succumbs to the poison, the bait continues attract new occupants.

Poisons used in bait boxes are called rodenticides and they are horrible poisons that do not kill quickly or humanely.  Animals suffer terribly before succumbing to death. Rodents are not the only victims of these poisons. Many predators succumb to secondary poisoning when they eat a poisoned rodent that is sickened and easy prey. Hawks, owls, foxes, coyotes, bobcats, wolves, raccoons, skunks, opossums, deer, and squirrels have all been victims, either directly or by secondary poisoning. Dogs, cats and even young children are also at risk for rodenticide poisoning.

A Place Called Hope Rehab Center in Killingworth, reports that rodenticides are fast becoming the number one threat to predatory birds of prey (including Bald eagles) due to overuse of these toxic poisons. 80% of raptors they see test positive for second generation anticoagulant rodenticides (SGARS), including birds who were fatally injured from other conflicts, such as vehicle collisions. A bird weakened by the poison is less capable of navigating its environment, increasing the likelihood of a fatal injury. Tufts University conducted a study to determine the extent and impact of rodenticide poisoning on red-tailed hawks. Results showed 97% had been exposed to rodenticides. There is a very low survival rate among victims. Most birds must be euthanized.

Owls, hawks, falcons and eagles all have federal protection and many have been victims of rodenticides. One might ask, how can the use of these poisons be acceptable when they are killing unintended animals, including those with federal protection?

There is simply no justification for the use of rodenticides when safer alternatives exist for controlling rodents. Mice enter homes through small cracks and openings. Sanitation and exclusion are the first line of defense against these intruders. It is important to identify and seal rodent entrance points to keep them out. Additionally, snap traps, CO2 traps, repellents and noise makers are all effective for controlling mice. Fertility control products are an innovative and humane alternative to traditional poisons and effective in reducing rodent populations when used in combination with other non-poisonous methods. For more information, go to www.ctforanimals.org to view webinar videos. 

The Newtown Conservation Commission is actively working to encourage healthy habitats and increase the diversity of our native wildlife and vegetation. www.newtownconservation.org

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