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Defining habitat conservation areas for tailed frogs.

Authors:
L. M. Darling, editor. 2000. Proceedings of a Conference on the Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15 - 19 Feb.,1999. Volume Two.
B.C. Ministry of Environment, Lands and Parks, Victoria, B.C. and University College of the Cariboo, Kamloops, B.C. 520pp. 489
Key words: Ascaphus truei, dispersal, headwater streams,
mark–recapture, movement, tailed frog, wildlife habitat
areas.
Tailed frogs live in small, fast-flowing streams with clear, cold
water (Green and Campbell 1992, Leonard et al. 1993,
Corkran and Thoms 1996), that often do not contain fish.
Egg deposition sites are rarely found (Corkran and Thoms
1996), and when they have been found they were located
close to the source of the stream (Brown 1975, Adams 1993),
suggesting that movement of larvae is downstream. The
species requires an unusually long time to develop, spending
1–5 years in larval form (Metter 1964, Metter 1967,
Daugherty and Sheldon 1982a, Brown 1990, Wahbe 1996).
Several studies have documented negative impacts of forest
practices on tailed frog adults and larvae, including complete
absence from clearcut areas (Metter 1968, Bury 1988, Bury
and Corn 1988, Welsh 1990, Bury et al. 1991, Walls et al.
1992, Dupuis and Friele 1995). Some authors (e.g., Welsh
1990) have argued that recolonization of logged sites is crit-
ical to sustaining productive amphibian populations.
Daugherty and Sheldon (1982b) found that 50% of reproduc-
tively mature Ascaphus remained in the same 20-m area of
their previous capture, and concluded adult Ascaphus ex-
hibit extreme site fidelity.
Headwater streams are classified as S4 (may contain fish),
S5 (no fish), and S6 (no fish) in the Riparian Management
Area Guidebook of the British Columbia Forest Practices
Code (B.C. Ministry of Forests and Ministry of Environment,
Lands and Parks 1995). These are Class C streams as de-
scribed in the British Columbia Coastal Fisheries/Forestry
Guidelines (B.C. Ministry of Forests et al. 1993). Headwater
streams are afforded no mandatory protection under current
laws unless the integrity of fish-bearing streams is at risk.
Although the tailed frog is designated “at risk” or “of spe-
cial concern” in Oregon, Washington, and British Columbia,
none of these jurisdictions provide riparian buffers around
small, non-fish-bearing streams (Bunnell et al. 1997). In
each case, forest practices legislation tends to be enacted as
blanket prescriptions. Currently, British Columbia has the
means to apply such prescriptions through the Managing
Identified Wildlife Guidebook of the Forest Practices Code
(B.C. Ministry of Environment, Lands and Parks and
Ministry of Forests 1999). Through this research, we will de-
termine the movement patterns and dispersal abilities of lar-
val and metamorphosed tailed frogs in old-growth forests and
clearcuts. Our goal is to provide scientifically credible guid-
ance for the establishment of wildlife habitat areas for in-
stream biological diversity, with emphasis on tailed frogs.
Given both the documented (e.g., Bunnell and Dupuis 1995)
and undocumented richness of small streams, many other
species undoubtedly would benefit.
Defining Wildlife Habitat Areas for Tailed Frogs
Tanya R. Wahbe
Centre for Applied Conservation Biology
Forest Sciences Centre, University of British Columbia
3004-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
wahbe@interchange.ubc.ca
ABSTRACT
The tailed frog (Ascaphus truei) is designated “at risk” or “of special concern” in British Columbia, Washington,
Oregon, and California, yet none of these jurisdictions provide riparian buffers around small, non-fish-bearing
streams where tailed frogs are found. We are investigating the movement patterns and dispersal abilities of tailed
frogs in south coastal British Columbia. Results of larval research illustrate that larvae in streams flowing through
old-growth forests moved about 7.5 times as far as larvae in streams flowing through clearcuts. Pitfall trapping
results reveal that, although most frogs were found in streamside arrays, some individuals moved as far as 100 m
from the nearest stream. Little is known about the dispersal abilities of tailed frogs, despite the implications to
forest management. Our results will provide information on the potential benefits of streamside buffers and wildlife
habitat areas to connectivity in fragmented landscapes.
Fred L. Bunnell
Centre for Applied Conservation Biology,
Forest Sciences Centre, University of British Columbia
3004-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
R. Bruce Bury
Biological Resources Division, United States Geological Service
3080 Clearwater Drive, Corvallis, OR 97333, USA
WAHBE ET AL.
490 Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999.
STUDY AREA
Research was conducted near Squamish in southwestern
British Columbia (Fig. 1), within coastal western hemlock
(Tsuga heterophylla) forest. Sites were distributed within 4
drainages: the Squamish, Elaho, Ashlu, and Mamquam
rivers, all tributaries to Howe Sound. Six headwater streams
were selected, consisting of 2 treatments (n= 3): old-growth
forest (>250 yr old) and clearcuts (5–10 yr old). Elevation of
sites ranged from 500 to 1,000 m.
All streams in the Squamish Valley were selected after ver-
ifying presence of larvae (15-min searches), and reaches
were chosen >50 m upstream from logging roads (except for
Mamquam and Squamish clearcut sites, which were selected
>50 m downstream from logging roads). Sites selected con-
tained low-order streams without known resident game or
anadromous fish.
METHODS
To determine the movement patterns of tailed frog larvae,
area-constrained stream surveys were employed (Fig. 2;
modified from Bury and Corn 1991, Shaffer et al. 1994) in
the summers of 1994, 1995, and 1996. During these field
seasons 80-year-old forest sites were also surveyed (n= 3).
The dorsal fin of the tail was marked with V-shaped notches
following Turner (1960) and Donnelly et al. (1994). Marks
were “reach-specific” (e.g., 2 notches for larvae in reach 2).
Area-constrained stream surveys and tailfin notches will also
be used in the 1999 field season. Mark-recapture of larvae
will be completed in 1999, using a modified stream sampling
design. The design previously employed (Fig. 2; Wahbe
1996) will be modified in the field to include searches in
larger stream sections (e.g., continuous 50 m).
Mark-recapture of metamorphosed tailed frogs using pitfall-
trap/drift-fence arrays and visual implant fluorescent elas-
tomers began in 1998 and will continue in 1999 and 2000.
The construction and installation of all traps and fences was
completed during the 1998 field season. Streamside and ups-
lope arrays of pitfall traps with drift fences (Fig. 3) were mod-
ified from suggestions by B. Bury and L. Jones. In each of the
Figure 1. Map of British Columbia showing location of
Squamish Valley.
Figure 2. Stream sampling design. Initial marking occurs with-
in 3 5-m reaches (solid boxes) separated by 25 m;
sampling for recaptures also includes 2 additional 10-
m reaches. Arrows indicate direction of stream flow.
Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. 491
Defining Wildlife Habitat Areas for Tailed Frogs
Figure 3. Streamside and upslope trap design (not to scale).
WAHBE ET AL.
492 Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999.
6 sites, 2 types of arrays (streamside and upslope) were
constructed and installed (Fig. 3). There are 3 streamside ar-
rays per site, each consisting of 4 pitfall traps and 1 drift fence.
There are 9 upslope arrays per site, each consisting of 4 pitfall
traps and 5 drift fences. Each of the 6 sites contains 48 5-m
drift fences and 48 pitfall traps. There are a total of 240 m of
drift fence and 288 pitfall traps in all 6 sites combined. Small
mammal escape ropes were constructed and installed to re-
duce small mammal mortality (modified from Wind 1996).
All tailed frogs (as well as other amphibian species cap-
tured) were injected subcutaneously with visible implant
fluorescent elastomers. Marks were unique to individuals. An
animal care certificate and permit were obtained (University
of British Columbia Protocol #A97-0035, British Columbia
Environment Permit #C068233).
RESULTS
Larvae in streams flowing through old-growth sites moved on
average 7.5 times further than larvae in streams flowing
through clearcuts (Fig. 4; Wahbe and Bunnell in prog.). The
maximum distance moved in old-growth sites was 64 m,
while in clearcuts it was 3 m. The 1999 sampling period will
allow final analyses of larval movement data.
Thirty-four tailed frogs were trapped over 21 nights of
sampling (6,048 trap-nights). Sixty-eight percent of tailed
frogs were trapped in old-growth sites (Fig. 5), where the rate
of capture was twice as high as in clearcut sites (Fig. 6).
Although most frogs were trapped in streamside arrays,
some individuals moved as far as 100 m from the nearest
stream. The individuals trapped at 100 m were newly meta-
morphosed tailed frogs moving away from the natal stream.
Of all tailed frogs trapped, 47% were reproductively ma-
ture adults and 38% were metamorphs (Fig. 7). Of the frogs
moving parallel to streams, 88% were moving upstream (Fig.
8). Of the frogs moving perpendicular to streams (through
upland forest), 56% were moving away from streams. With
pitfall-trap/drift-fence array installations complete, mark-
recapture of frogs will continue in 1999 and 2000.
DISCUSSION
Tailed frog larval movement hypotheses we are exploring in-
clude: 1) the stream channel barrier hypothesis, where log-
jams in streams flowing through clearcuts create barriers to
tadpole movement; 2) the algal productivity hypothesis,
where streams with high algal biomass show low movement
of tadpoles; and 3) the gradient/productivity hypothesis,
where tadpoles in high gradient streams move less due to
high productivity.
Given the uncommonly long larval stage of tailed frogs,
movements by larvae may be particularly important to recol-
onization. After clearcutting, however, small streams often
contain logging debris that could impede movement and re-
colonization by larvae from upstream egg deposition sites.
Results to date show that larval dispersal abilities are signifi-
cantly greater in streams flowing through old-growth forests
than in streams flowing through clearcuts (Wahbe and
Bunnell in prog.). All clearcut streams used in this study con-
tained abundant logging debris, lending support to hypothesis
Figure 4. Average distance moved by tadpoles in each forest
habitat type (1994, 1995).
Figure 5. Total number of tailed frogs trapped in old-growth
forests and clearcuts.
Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999. 493
Defining Wildlife Habitat Areas for Tailed Frogs
1. Our data also support hypothesis 3, where high-gradient
streams showed low movement of larvae. Hypothesis 2 will be
tested during the 1999 field season.
Tailed frog post-metamorphic movement hypotheses we
are exploring include: 1) the extreme philopatry hypothesis,
where frogs remain within a restricted range, moving short
distances along streams in both old-growth forests and
clearcuts; 2) the stream dependency hypothesis, where frogs
in clearcuts are more restricted to the stream than frogs in
old-growth forests; 3) the age-specific movement hypothesis,
where metamorphs and juveniles are responsible for most of
the upland movements, while adults remain relatively seden-
tary, moving primarily along the stream; and 4) the macro-
climatic movement hypothesis, where movements of frogs in
wet environments are less restricted than movements in dry
environments. Hypothesis 4 will be tested through compar-
isons between tailed frog movements in British Columbia
and tailed frog movements in southern Oregon.
Preliminary trapping results reveal that, although most
frogs were found in streamside arrays, some individuals
moved as far as 100 m from the nearest stream. This demon-
strates that the dispersal abilities of tailed frogs are much
greater than previously suggested (Daugherty and Sheldon
1982b), and rejects hypothesis 1. More importantly, the indi-
viduals at 100 m were newly metamorphosed tailed frogs,
lending support to hypothesis 3, where early age-classes are
responsible for upland movements. The majority of frogs
found in streamside arrays were reproductively mature and
were moving upstream, which supports suggestions that tailed
frogs breed during the fall in upper reaches of streams. This
also lends some support to hypothesis 3, where adults remain
relatively sedentary, moving primarily along the stream.
MANAGEMENT IMPLICATIONS
Forest management decisions should consider the ecological
integrity of sensitive habitats and species, and the connec-
tivity of ecosystems to ensure continued dispersal and move-
ment of ecologically sensitive species across the landscape.
It is important to ensure the protection of streams because
they provide tailed frogs with breeding sites, over-wintering
sites, and potential dispersal corridors for gene flow between
populations. It may be equally important to ensure
Figure 6. Captures per 100 trap-nights in old-growth forests
and clearcuts.
Figure 7. Number of tailed frogs trapped in each stage of
development.
Figure 8. Number of tailed frogs moving upstream and down-
stream.
WAHBE ET AL.
494 Proc. Biology and Management of Species and Habitats at Risk, Kamloops, B.C., 15–19 Feb. 1999.
protection of the terrestrial habitat required by this species,
and the value of riparian buffers needs evaluation.
Results of this research carry important conservation and
management implications for tailed frogs and their habitats:
cold, rocky streams, which are essential for many animals,
including salmonid fishes. Our goal is to develop wildlife
habitat areas or other alternative forest management designs
to address the needs of identified wildlife.
ACKNOWLEDGEMENTS
We thank Wildlife Habitat Canada and Forest Renewal
British Columbia for providing research funding. K.
Sadowski, N. Job, L. Frid, K. Maxcy, N. Holling, S. Webber, J.
Rodrigues, Y. Ota, and I. Houde assisted with fieldwork.
Special thanks go to M. Wahbe, E. Jovel, R. Mooney, J.
Dojillo, J. Arsenault, J. Peterson, B. Kreowski, and L.
Burrows for volunteering their time on this project. T. R.
Wahbe was supported by Forest Renewal British Columbia
and a British Columbia Environmental Research Scholarship
from the Ministry of Environment, Lands and Parks.
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