1. Forest Bats: Biology and Habitat Requirements in the PNW
With Comments on Study Methods for Bats of Washington’s Forests

2. Bats World-wide Present-day bats occur in two lineages Megachiroptera
1 Family; 166 species
Microchiroptera
16 Families; 759 species
All PNW bats are “evening bats” in the family Vespertilionidae
Megachiroptera (Old World Fruit Bats)
Icaronycteris †
Archaeonycteris †
Hassianycteris †
Palaeochiropteryx †
Microchiroptera (Echolocating Bats)

3. Megachiroptera Semi-tropical and tropical environments
Grey-headed flying fox
Semi-tropical and tropical environments
Primarily fruit-eating, generally do not echolocate
As a group they are of conservation concern
Little red flying fox

4. Microchiroptera Cosmopolitan
Insectivorous in temperate regions, but diverse food habits in the tropics
Show all mammalian reproductive modes
Facultative control of body temperature
Echolocate
Southern long-nosed bat
Hairy-legged vampire bat

5. Washington’s Bats 16 species total 4 desert species Pallid bat
Western small-footed bat (Myotis species)
Western pipistrelle
Spotted bat added to our fauna in 1991.

6. Washington’s Bats 12 forest dwelling Big brown bat
Western red bat in the Okanogan?
Hoary bat
Silver-haired bat

7. Washington’s Bats Townsend’s big-eared bat 7 Myotis species
Keen’s myotis our only PNW endemic bat.

8. All PNW Bats Echolocate
Larynx makes loud outgoing call
Echo used for navigation and feeding
Most calls kHz

9. Group Living in the PNW
Unlike elsewhere, bats in PNW usually occur in small colonies
Large cave systems relatively uncommon
Most species roost in rock or tree crevices
Most species will use “bat friendly” human structures

10. Day Roosts: Large Living Trees
Exfoliating bark of old trees provides roosts unlike young conifers
Source for large snags
Roosts often are on southern exposures and on forest edges

11. Day Roosts: Large Snags
Provide thermal choices for bats
Cavities provide space for maternity colonies
May need buffering with live trees as they decompose
Need to work out replacement schedules

12. Super-canopy Trees and Snags
We know from radio-telemetry work that bats often will roost in the largest tree or snag in a stand
In addition to excellent roosting habitat these trees may serve as navigational features

13. Bats & Forest Succession
Use early successional areas and water bodies for foraging
Roost in forests with suitable trees & snags
High quality habitat is close to food, water, and roosts
Commuting a hassle for bats as well!
Roosting
Foraging 1
Grass-forb 2
Shrub-seedling 3
Pole-sapling 4
Mature 4
Old growth 4
Young
Six successional stages

14. Common Approaches for Studying Bats
Early work conducted with shotguns
Mist nets were a marked improvement
Radio-telemetry with miniature transmitters
Harp or Tuttle traps
Echolocation detectors
Daubenton’s bat (John Altringham 2000)

15. Harp or Tuttle Traps Ingenious design!
Very effective in restricted flyways, but sample smaller areas
Fairly easy on the bats
Fairly easy on the batters

16. Placement Requires Deviousness
Bats are smart and they may be older than the humans studying them
Restrict flyways if needed

17. The Anabat SD1 Detector
Automated voice-activated system converts high frequency sound into the audible range
Consists of broadband microphone, sensitivity switch, “divide-by-X” circuitry, calibration tone, clock, digitizer, and a CF-card
PLTO

18. Anabat Call Displays
Display has header information and the frequency/time display
Lowest frequency and shape of call are the most useful
Can key most non-Myotis calls to species
Myotis species calls too similar to key
EPFU
MYYU

19. Analysis of Detection Data
Can reveal patterns of activity
Allows comparison of activity across habitats
Detection rates and abundance do not correspond directly
Comparisons can be made within species but not between them

20. Bat Activity in the PNW
Foraging and raising young are functions of flying insects that like warm, dry nights
Activities highest east of the Cascades and in rain shadows and at low elevations west of the Cascade crest

21. Bat Activity in Managed Forest Landscapes
Timber, Fish, Wildlife Landscape Study
In managed forests NW of Mt. Rainier NP
Four stand types, 6 replicates of each
Studied 3 consecutive years
Anabat call surveys used; therefore a study of frequencey of use patterns across stand types
Results similar to other studies in managed forests of the PNW

22. Recently Harvested Sites
2-3 yrs after harvest
Douglas-fir seedlings 3-6 ft. tall

23. Pre-commercially Thinned Sites
12-20 yrs after harvest
Light still reaching ground between trees

24. Young, Unthinned (Dog-hair) Sites
30-40 yrs after harvest
High tree density
Small diameter trees
Poor development of understory and ground-level vegetation

25. Harvest-age Sites 45-70 yrs after harvest
Pre- and commercially thinned
Understory present
Ground-level vegetation productive

26. Average Activity per Site Type
Highest activity in open, early successional areas
Intermediate activity in transitional and harvest-age forests
NO activity on six sites over 3 years in unthinned, young forest !

27. Bat Activity Varies on Forested Landscapes1
Grass-forb 2
Shrub-seedling 3
Pole-sapling 4
Young 5
Mature

28. Conversion of Old Forests to Young
Lose roosts: large living trees and snags
Create dense stands without foraging gaps
May lose insect diversity within stand

29. Factors of Decline for Bats in the PNW
Forest conversion to urban/suburban development and agriculture—bat declines regionally
Loss of large trees and snags—bat declines on forest lands
Creation of large acreages of dense, young forests (dog-hair)—effective elimination of bat habitat
Proportional increase in non-Myotis bats with predominance of young forest mosaic?

30. Factors of Decline for Bats in Forests
West-side Forests
East-side Forests
Increase in irrigation systems, livestock ponds—bats increase
Elevational constraints on bat activities not as severe as west side—national forests may play a larger role than on west side
Reduction of wetland area—bat declines
Breeding habitat (low elevation) reduced by human development
Breeding habitat located in forests managed for timber (low elevation)

31. How to Retain Our Forest Bats?
Can you say, “Growth management”? Especially on the west side
Thin dense, young forests—an economic challenge
Maintain large live trees and snags on uplands (one / 7 acres?) not just within riparian zones
Harvest patches might substitute for foraging gaps in old forests (bats seem willing), but quality roosts must be maintained nearby

32. Bat Photographs Bats are a pain to photograph!
This is the ultimate photo book for North American mammals
A cooperative venture between the Smithsonian and the American Society of Mammalogists

33. More Bat Photographs Wonderful slide sets available from BCI
batcon.org