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Bats and ODOT Bridges. ODOT Environmental Services November 15, 2000. ODOT bridges are used by bats for roosts. 13 species of bats use bridges for roosts; Bridge roosts have replaced tree roosts that have been cut; ODOT bridges are important to bat conservation. Basics of Bat Behavior.

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Bats and odot bridges

Bats and ODOT Bridges

ODOT Environmental Services

November 15, 2000


Odot bridges are used by bats for roosts
ODOT bridges are used by bats for roosts

  • 13 species of bats use bridges for roosts;

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

  • ODOT bridges are important to bat conservation.


Basics of bat behavior
Basics of Bat Behavior

  • Bats live year-round in Oregon;

  • Winter: some bats migrate; most hibernate (not in bridges) - some bats are active in western Oregon;

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

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


Night roosts and day roosts
Night roosts and day roosts

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

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


Bats select certain bridge types
Bats select certain bridge types

  • Concrete bridges:

    • T-beam, Box beam, Sub-structure with vertical surfaces; Larger bridges;

  • Timber bridges:

    • Minor use if not treated with preservatives

  • Steel bridges not used


Bridge location is important
Bridge location is important

  • Sunny locations important

  • Shaded bridges in trees, canyons, or gorges get little use

  • Solar radiation = warmth at night

  • Larger bridges absorb more heat


Bridges are used as day roosts and night roosts

DAY ROOSTS:

Crevices

Inside box beams

Hollow spaces

Caverns

NIGHT ROOSTS:

Vertical surfaces

Ceilings

Abutments

Ends of the bridge

Bridges are used as day roosts and night roosts


How to recognize bat use
How to recognize bat use

  • You see bats. Look in crevices;

  • You hear bats. High-pitched chirps;

  • Bat sign: guano - dirty rice grains beneath vertical surfaces or crevices

  • Bat sign: urine stains - white and powdery on vertical surfaces;

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


Bat guano
Bat Guano

  • Contains insect parts, no vegetation;

  • Dark brown to black: insect skeletons;

  • Gray: moth wing scales;

  • Size: rice grain (small bats);

  • Size: puffed wheat (large bats)


Safety risks
Safety risks

  • Do not pick up bats;

  • Bats out in the open during the day are probably sick, and could be rabid; only rabid bats can transmit the disease;

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

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


Can bat presence affect your bridge work
Can bat presence affect your bridge work?

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

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


What to do if you find bats
What to do if you find bats

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

  • Determine if maternity colony (biologist)

  • Coordinate activities April 1 - September 1.


Big brown bat

Photo by Merlin Tuttle


Big brown bats

Photo by Merlin Tuttle


Pallid bat

Photo by Merlin Tuttle


Pallid bat

Photo by Merlin Tuttle


Silver-haired bat

Photo by

Merlin Tuttle


Hoary bat

Photo by Merlin Tuttle


California myotis

Photo by Roger Barbour


Little brown myotis

Photos by Merlin Tuttle


Long-eared myotis

Photo by B. Moose Peterson


Fringed myotis

Photo by Roger Barbour


Long-legged myotis

Photo by Roger Barbour


Yuma myotis

Photo by Merlin Tuttle


Small-footed myotis

Photo by Merlin Tuttle


Western pipistrelle

Photo by Merlin Tuttle


Brazilian free-tailed bat

Photo by Merlin Tuttle


Townsend’s big-eared bat

Photo by Merlin Tuttle


Townsend’s big-eared bat

Photo by Merlin Tuttle


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