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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

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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

  • 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: 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

  • 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

  • Sunny locations important

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

  • Solar radiation = warmth at night

  • Larger bridges absorb more heat


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

  • 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

  • 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

  • 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?

  • 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

  • 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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