Bats and ODOT Bridges

ODOT Environmental ServicesODOT Environmental Services

November 15, 2000November 15, 2000

ODOT bridges are used by bats for roosts

13 species of bats 13 species of bats use bridges for use bridges for roosts;roosts;

Bridge roosts have Bridge roosts have replaced tree roosts replaced tree roosts that have been cut;that have been cut;

ODOT bridges are ODOT bridges are important to bat important to bat conservation. conservation.

Basics of Bat Behavior Bats live year-round in Oregon;Bats live year-round in Oregon; Winter: some bats migrate; most Winter: some bats migrate; most

hibernate (not in bridges) - some bats hibernate (not in bridges) - some bats are active in western Oregon;are active in western Oregon;

Summer: Day roosts (females in Summer: Day roosts (females in maternity colonies; males solitary or in maternity colonies; males solitary or in bachelor colonies); Night roosts;bachelor colonies); Night roosts;

Emerge at dusk, drink, feed, rest at night Emerge at dusk, drink, feed, rest at night roosts, feed again, go to day roost at roosts, feed again, go to day roost at dawn, sleep (in torpor) all day.dawn, sleep (in torpor) all day.

Night roosts and day roosts

Night roosts: Resting places to keep Night roosts: Resting places to keep warm, digest food, engage in social warm, digest food, engage in social behavior.behavior.

Day roosts: Hidden, dark places Day roosts: Hidden, dark places (crevices, caves, tree cavities) where (crevices, caves, tree cavities) where the bats sleep through the day.the bats sleep through the day.

Bats select certain bridge types

Concrete bridges:Concrete bridges: T-beam, Box beam, Sub-structure with T-beam, Box beam, Sub-structure with

vertical surfaces; Larger bridges;vertical surfaces; Larger bridges; Timber bridges:Timber bridges:

Minor use if not treated with preservativesMinor use if not treated with preservatives Steel bridges not usedSteel bridges not used

Bridge location is important

Sunny locations importantSunny locations important Shaded bridges in trees, canyons, or Shaded bridges in trees, canyons, or

gorges get little usegorges get little use Solar radiation = warmth at nightSolar radiation = warmth at night Larger bridges absorb more heat Larger bridges absorb more heat

Bridges are used as day roosts and night roosts

DAY ROOSTS:DAY ROOSTS: CrevicesCrevices Inside box beamsInside box beams Hollow spacesHollow spaces CavernsCaverns

NIGHT ROOSTS:NIGHT ROOSTS: Vertical surfacesVertical surfaces CeilingsCeilings AbutmentsAbutments Ends of the bridgeEnds of the bridge

How to recognize bat use

You see bats. Look in crevices;You see bats. Look in crevices; You hear bats. High-pitched chirps;You hear bats. High-pitched chirps; Bat sign: guano - dirty rice grains Bat sign: guano - dirty rice grains

beneath vertical surfaces or crevicesbeneath vertical surfaces or crevices Bat sign: urine stains - white and Bat sign: urine stains - white and

powdery on vertical surfaces;powdery on vertical surfaces; Bat sign: body oil stains - dark, on Bat sign: body oil stains - dark, on

vertical surfacesvertical surfaces

Bat Guano

Contains insect parts, no vegetation;Contains insect parts, no vegetation; Dark brown to black: insect skeletons;Dark brown to black: insect skeletons; Gray: moth wing scales;Gray: moth wing scales; Size: rice grain (small bats); Size: rice grain (small bats); Size: puffed wheat (large bats)Size: puffed wheat (large bats)

Safety risks

Do not pick up bats;Do not pick up bats; Bats out in the open during the day are Bats out in the open during the day are

probably sick, and could be rabid; only probably sick, and could be rabid; only rabid bats can transmit the disease;rabid bats can transmit the disease;

Bats can get rabies but they do not carry Bats can get rabies but they do not carry the rabies virus;the rabies virus;

If you need to move a bat, use a tool If you need to move a bat, use a tool (shovel, broom);(shovel, broom);

Can bat presence affect your bridge work?

Yes, if the bridge has a maternity Yes, if the bridge has a maternity colony; the young cannot fly until late colony; the young cannot fly until late July; disturbance or demolition could kill July; disturbance or demolition could kill the young bats.the young bats.

Night roosting and day roosting by Night roosting and day roosting by males is not a concern; they can find males is not a concern; they can find other roosts.other roosts.

What to do if you find bats

Contact the Region Environmental Contact the Region Environmental Coordinator (Richard Beck, Molly Cary Coordinator (Richard Beck, Molly Cary or Brian Bauman, Max Mizejewski; or Brian Bauman, Max Mizejewski; Shelly Schmidt, or Chuck Howe);Shelly Schmidt, or Chuck Howe);

Determine if maternity colony (biologist)Determine if maternity colony (biologist) Coordinate activities April 1 - Coordinate activities April 1 -

September 1.September 1.

Big brown batPhoto by Merlin Tuttle

Big brown batsPhoto by Merlin Tuttle

Pallid batPhoto by Merlin Tuttle

Pallid batPhoto by Merlin Tuttle

Silver-haired batPhoto by

Merlin Tuttle

Hoary batPhoto by Merlin Tuttle

California myotisPhoto by Roger Barbour

Little brown myotisPhotos by Merlin

Tuttle

Long-eared myotisPhoto by B. Moose Peterson

Fringed myotisPhoto by Roger Barbour

Long-legged myotisPhoto by Roger Barbour

Yuma myotisPhoto by Merlin Tuttle

Small-footed myotisPhoto by Merlin Tuttle

Western pipistrellePhoto by Merlin Tuttle

Brazilian free-tailed batPhoto by Merlin Tuttle

Townsend’s big-eared batPhoto by Merlin Tuttle

Townsend’s big-eared batPhoto by Merlin Tuttle