Indiana bats give birth to only one young in mid-summer. The young bats are capable of flight in a month.
Indiana Bat Forestry Project
Guidance for Creating Better Woodland Bat Habitat
New Jersey is home to nine bat species, including the endangered Indiana bat (Myotis sodalis). Indiana bats inhabit forests and wooded wetland areas in summer, where they roost and raise their young under the loose bark of certain living trees (such as shagbark hickory) and a variety of dead or dying trees (elms, oaks, maples, sycamores, hickories, etc.).
Ideal roost locations are near a wetland or water body that provides a reliable insect prey base and a source of drinking water. Maternity roosts must also receive around eight hours of sunlight to help with the development of bat pups. Indiana bats have been documented across much of northern NJ and are known to hibernate in Hibernia and Mt. Hope Mines, Morris Co.
Indiana Bat Forestry Project
The Conserve Wildlife Foundation of New Jersey worked with fifteen forest landowners to conduct silviculture (forestry) management practices to benefit Indiana bats as well as New Jersey’s more common bat species. We performed the following practices, which you can try on your own:
- Selective tree girdling. Girdling results in standing dead trees whose breaking, flaking bark provides space for bats to roost under. Studies have found that the average DBH (diameter at breast height) of Indiana bat maternity roost trees is 45 cm, so trees of that size should be targeted. Girdling can be accomplished by chain-sawing two horizontal cuts – about 6” wide, 1” or deeper, and 2-4” apart – around the entire tree trunk, or cutting one groove and applying an herbicide.
- Removal of competing trees. Where appropriate, felling smaller trees can open a potential roost tree to more sunlight, making it more attractive to maternity colonies. Alternatively, girdling multiple trees in a "patch" can reduce canopy shading without felling trees.
- Artificial roost enhancements. For instant and longer-lasting bat roosts, tree-trunk-wraps, shingles, and standard bat boxes can be installed around girdled trees. This can also be done to dead trees whose bark has dropped off - like turning back time. The goal is to mimick the loose bark that bats prefer.
We intend for our 15 projects to be monitored over a minimum five-year period for usage by bats. We will instruct and assist landowners in surveying their own sites. Because we do have nine different bat species in New Jersey (and they’re difficult to identify without capturing them), we will also use acoustic devices to record and identify species by their echolocation calls. Acoustic monitoring allows for passive study, without disturbing the animals.
Funding for this project was provided by the New Jersey Landowner Incentive Program (LIP).
Creating Forest Roosts For Bats - 449.9KB
- Forest Management & Bats - a 14-page Bat Conservation International publication by Daniel Taylor, 2006.
- Controlling Undesirable Trees, Shrubs, and Vines in Your Woodland - an Ohio State University Extension fact sheet on tree girdling techniques.
- Tree Girdling Tools (Part 1: Intro; Part 2:Girdling tools; Part 3: Comments on girdling tools) - a USDA Forest Service instructional, 1999.
- Small Woodlot Improvement Guide - a 4-page NRCS publication for forest owners, especially those with 10-30 acre lots.
- USDA NRCS Forestry Conservation in New Jersey webpage, including best management practices, farmland assessment info, and more.
General Forest Management Recommendations for Bats:
The following recommendations were developed by the US Fish and Wildlife Service, New Jersey Field Office.
- Maintain at least 60% canopy closure after timber harvest within forested stands.
- Retain standing snags, except where they pose a serious human safety hazard due to their location near a building, yard, road or power line. A live tree with less than 10% canopy should be considered a snag. Snags with no remaining bark and no visible cracks, splits, or hollows may be felled, as well as any snags leaning more than 45º from vertical. When possible, delay removal of hazard trees until bats are hibernating (between October 1 and March 31).
- Do not harvest or manipulate shagbark hickory trees (Carya ovata) unless the density of shagbark hickory exceeds 16 trees per acre. If present, maintain at least 16 live shagbark hickory greater than 11" dbh (diameter at breast height) per acre. If there are no shagbark hickory trees >11" dbh, then the live shagbark hickory trees retained per acre must include the largest specimens in the stand.
- Maintain at least 16 live, high-value roost trees per acre on average with at least 3 live trees >20" dbh and 6 live trees >11" dbh. The remaining trees retained per acre should be among the largest or highest roost value trees present within the stand.
- Do not harvest trees or conduct timber stand improvement within 300 feet of a stream bank or wetland, or within 500 feet of a known bat hibernaculum.
- Do not fell trees >3" dbh while Indiana bats may be present, generally April 1 – September 30.
- Avoid prescribed burns from April 1 to September 30 in forest stands containing potential Indiana bat live roost trees and / or snags.
- Avoid prescribed burns year-round within 1,000 feet of a known bat hibernaculum.
The following tree species have been identified as having relatively high value as potential Indiana bat roost trees (*denotes the more commonly used roost tree species, although characteristics such as loose or shaggy bark, crevices, or hollows are more important than tree species):
Red maple (Acer rubrum), Shagbark hickory* (Carya ovata), White oak* (Quercus alba), Silver maple* (Acer saccharinum), Other hickories (Carya spp.), Pin oak (Quercus palustris), Sugar maple* (Acer saccharum), White ash (Fraxinus americana), Post oak (Quercus stellata), Yellow birch (Betula alleghaniensis), Green ash* (Fraxinus pennsylvanica), Red oak (Quercus rubra), Gray birch (Betula populifolia), White pine (Pinus strobus), Slippery elm (Ulmus rubra), Bitternut hickory (Carya cordiformis), Eastern cottonwood* (Populus deltoides), Sweet pignut hickory (Carya ovalis), and American elm* (Ulmus americana)
Stephanie Feigin, Wildlife Ecologist:
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