Bats and ODOT Bridges

1. Bats and ODOT Bridges ODOT Environmental Services November 15, 2000

2. 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.

3. 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.

4. 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.

5. 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

6. 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

7. 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

8. 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

9. 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)

10. 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);

11. 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.

12. 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.

13. Big brown bat Photo by Merlin Tuttle

14. Big brown bats Photo by Merlin Tuttle

15. Pallid bat Photo by Merlin Tuttle

16. Pallid bat Photo by Merlin Tuttle

17. Silver-haired bat Photo by Merlin Tuttle

18. Hoary bat Photo by Merlin Tuttle

19. California myotis Photo by Roger Barbour

20. Little brown myotis Photos by Merlin Tuttle

21. Long-eared myotis Photo by B. Moose Peterson

22. Fringed myotis Photo by Roger Barbour

23. Long-legged myotis Photo by Roger Barbour

24. Yuma myotis Photo by Merlin Tuttle

25. Small-footed myotis Photo by Merlin Tuttle

26. Western pipistrelle Photo by Merlin Tuttle

27. Brazilian free-tailed bat Photo by Merlin Tuttle

28. Townsend’s big-eared bat Photo by Merlin Tuttle

29. Townsend’s big-eared bat Photo by Merlin Tuttle