November 2006





Now is the time of year when animals start looking for winter shelter. What is the best way to keep bats out of my house?

The first step in excluding bats is to locate the entry points to your house. Bats can enter through holes as small as three-quarter inches, the diameter of a dime. Typical entry points include chimneys, louver fans, air intakes, exhaust vents, openings around plumbing, power or cable lines, spaces around doors and windows, and where exterior siding has shrunken, warped or loosened. Close inspection during the day will help determine the exact location of these entry points. Caulk, weatherstripping, insulation materials, screening, steel wool, or even duct tape can be used to close these and other entry points. Efforts to bat-proof your home will also often improve its energy efficiency. Another good way to keep bats out of the interior of your home is to make sure doors to attics and basements are well sealed, and that dampers are kept closed when the chimney is not in use.

Lori Naumann, DNR Nongame Wildlife Program


Buckthorn has become a major problem throughout the state. Can planting native species help suppress the growth of buckthorn, especially after buckthorn is removed from an area?

Depending on the circumstances, restoring native plant species after buckthorn removal may help suppress the regrowth of buckthorn. Without follow-up control of resprouting plants and seedlings that emerge after initial control, buckthorn will come right back. Buckthorn seeds in the soil can remain viable for up to five years. As a result, it is essential to monitor and manage buckthorn stands each year to suppress its growth and allow native plants to establish. The best time to cut and chemically treat the stumps is in late summer and throughout the fall. Control methods are available on the DNR Web site at

Luke Skinner, DNR Invasive Species Program


The red pine is the Minnesota state tree. How did it earn this distinction?

The legislature felt it was important to adopt a state tree as a symbol of the history and physical characteristics of the state. The red pine, or Norway pine, is native to Minnesota and is found in pure stands in many parts of the state. In the early history of Minnesota, red pine timber played an important part in the state economy. Most importantly, the red pine is a sturdy and majestic tree. It was adopted as the state tree in 1953. The tallest red pine in Minnesota, located in Itasca State Park, stands over 126 feet tall and is over 300 years old.

Rick Klevorn, DNR Division of Forestry


Are there benefits to low lake and river levels as a result of the recent drought?

There are benefits to fluctuating levels as long as they are not extreme. Moderate fluctuations can benefit certain plants and animals by allowing revegetation of the shallow wetlands and lakes. In some areas, DNR lowers levels of shallow wetlands on purpose to enhance vegetation growth, and to control rough fish. Drought impacts would benefit those projects, like the Swan Lake project. Flood flows and extreme drought can cause damage to infrastructure and habitat that could take years to recover. More extreme drought could allow invasive species to establish in a wetland, which would have negative resource impacts. It is very difficult to answer with a statewide perspective since the resource varies, as does the degree of drought.

Kent Lokkesmoe, DNR Waters Division director


DNR Question of the Week Archive