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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
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