Seattle Public Utilities Mami Hara, General Manager/CEO

 

Bats

There are 11 species of bats listed as species of concern in the HCP. None are federally listed as threatened or endangered, and only Keen’s myotis is listed as a candidate species by Washington State.

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Hoary bat - photo by Jennifer Linehan

Forest bats roost, breed, and hibernate in hollow trees and snags, within dense foliage, or in the deep furrowed bark of large old trees. Old-growth forest provides optimal habitat for these small mammals because of the large number of big snags and giant old trees, the diversity of plant species that support large numbers of insects, and the numerous canopy gaps where bats can forage. Many species are colonial breeders, so require the large tall snags and trees in old-growth forest to accommodate up to 500 females and young.

During the night, bats forage in gaps within the forest, as well as over wetlands, streams, and lakes, eating huge numbers of insects. A single bat can eat up to 2,000 insects each night.

Dense second-growth forests often are too “cluttered” for bats to successfully navigate through using echolocation. Difficulty flying through these forests, along with far fewer insects that bats feed on, means that few bats use the second-growth forests in the watershed.

Goals

Our long-term goal, over the next 50 to 100 years, is to maintain existing bat habitat, as well as enhance habitat for bats in the watershed. Our specific objectives include:

  1. Protect and maintain all existing old-growth forest habitat
  2. Enhance bat habitat by accelerating the development of old-growth forest characteristics in young second-growth plantation forests

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What are we doing for bats?

Both upland and riparian forest habitat enhancement projects should facilitate development of the large trees and snags forest bats need for roosting, breeding, and hibernating more rapidly than would passive restoration alone. In addition, habitat enhancement projects that result in fewer trees, small canopy gaps, and greater plant species diversity will provide greater foraging opportunity and ease of navigation for bats.

Upland Forest Habitat Restoration
Upland forest habitat enhancement projects are designed as active restoration projects to accelerate old-growth forest conditions in second-growth forest generated after clearcut logging. One restoration technique, variable density thinning, provides more growing space for remaining trees. This should provide navigation room for bats, as well as facilitate development of the large trees and snags used for roosting more rapidly than would passive restoration alone. Snag creation and planting a variety of plant species that support insect populations will also enhance bat habitat. View more on our upland forest habitat restoration program.

Aquatic and Riparian Habitat Restoration
Riparian habitat enhancement projects include planting conifer trees such as Sitka spruce and western red cedar in areas with few or no conifers, releasing existing conifers in areas where they are being suppressed by dense overstory alder trees, and thinning in dense conifer stands. All of these techniques should accelerate development of the large conifer trees used by bats for roosting, breeding, and hibernation. View more information on our aquatic and riparian habitat restoration program.

Protect All Watershed Habitats
Management of the watershed serves to avoid or minimize adverse effects of major events such as fire, spills of toxic materials, invasive species, and excessive human disturbance. Protecting the forest from fire will likely provide the most benefit for forest bats. This protection helps to maintain all existing old-growth forest and through passive restoration allows second-growth forest to develop the large trees and snags needed for roosting and breeding. View more information on habitat protection.

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