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Small Mammal Communities in the Oregon

Cascade Range

Frederick F. Gilbert and Rochelle Allwine

Authors

FREDERICK F. GILBERT is a professor and wildlife biologist and ROCHELLE ALLWJNE is an agriculture research

technician, Department of Natural Resource Sciences, Washington State University, Pullman, Washington 991646410.

Abstract

Pitfall and snap-trapping of small mammals in the western

Oregon Cascade Range in 1984-85 revealed no significant

differences in species richness among young, mature, and oldgrowth Douglas-fir stands. Trowbridge’s shrew was the most

abundant small mammal captured, accounting for about half

of all captures. Species showing some association with older

stands included Trowbridge’s shrew, the shrew-mole, the

deer mouse, and the red tree vole. The coast mole was found

only in mature and old-growth stands in 1985. These species’

associations with vegetational and physical characteristics

indicated temporal and spatial differences in habitat use. The

tree squirrels (Douglas’ squirrel and northern flying squirrel)

showed strong positive correlations with snags. The Soricidae

segregated themselves on latitudinal, elevational, and moisture gradients.

Results from this study need to be treated with some caution:

the young and mature stands contained many characteristics

of old-growth stands because they had been naturally

regenerated (usually after fire) and thus did not represent

conditions that might be expected in stands managed for

timber production.

Introduction

The effects of forest fragmentation or general loss of habitat

are seldom immediately visible in small mammal communities. Studies in the western National Parks, though, support

the contention that declines in species richness are likely

over time with insularization of habitat (Weisbrod 1976).

Harris and others (1982), Raphael (1988c), and Rosenberg

and Raphael (1986) suggest that the long-term reduction of

old-growth forests will negatively affect small mammal populations. Comparisons of species occurrence and abundance in

different-aged stands may provide insight into the effects of

truncation of seral development on existing faunal communities. The objectives of the current study were to assess the

small mammal communities of young, mature, and oldgrowth Douglas-fir stands in the Oregon Cascade Range and

and determine which environmental factors might be

responsible for any differences observed.

Materials and Methods

Three locations on the western slopes of the Oregon Cascades

were studied in 1984. Twenty stands were selected in the

Rogue River and Umpqua National Forests (Rogue-Umpqua),

20 near the H.J. Andrews Experimental Forest (Andrews)

and 16 in the Mount Hood region (Mt. Hood). These stands

257
were selected to represent young, mature, and old-growth

Douglas-fir forests and a moisture gradient (wet, mesic and

dry) in the old-growth stands (Gilbert and Allwine, this volume b: see appendix table 15). In addition, a few stands were

selected to represent either a mature-age moisture gradient or managed stands. Final analyses were done for fewer

than 56 stands to assure comparison between mesic, unmanaged stands of the three age-classes (22 old-growth,

17 mature, and 9 young); 28 old-growth stands were in the

moisture-gradient analysis (7 dry, 9 mesic, 12 wet).

Trapping Methods

Pitfall grids (6 x 6) were established in each stand and

checked during September and October 1984. One pitfall

trap consisting of 2 number 10 cans taped together and lined

with plastic margarine tubs was buried within 2 m of each

grid station. A cedar shake was placed above the opening to

minimize rain and snow accumulation in the cans. Water

was removed at each check. The traps were opened in early

September and checked every 5 to 7 days for at least 50

days. In 1985, 15 stands at the Andrews were studied; the

old pitfall grids were used in all stands, and new grids were

established in 8 of them (Gilbert and Allwine, this volume b:

see appendix table 15). Results from the old and new pitfall

grids were compared to determine whether the previous

year’s trapping had affected the resident populations. Chisquare testing was used to examine species captured and

number of individuals of each species in the eight stands.

Because the new grids showed no difference in species composition and abundance, the old grids were used for analysis.

In 1984, snap trap grids (12 x 12) with 15-m spacing between grid locations also were used to sample the smallmammal fauna. Trapping took place in July and August, and

each stand was trapped for 4 consecutive nights. Two Museum Special traps (Woodstream Corp., Lititz, PA) baited

with a mixture of peanut butter and rolled oats were placed

within a 1.5-m radius of each grid location.

Mammals caught in the pitfall traps usually had drowned or

otherwise died by the time of collection. All animals were

identified to species, sexed, measured, and preserved in the

Conner Museum at Washington State University as skulls,

skeletons, or skins and skulls. Identifications were verified

by museum staff. Even with the examination by museum personnel, many Soricidae could not be identified to species.

Vegetative Measurements

The physical and vegetative characteristics of the trapping

grids were sampled at 9 points within the pitfall grid and

16 points within the snap trap grids, with the center of each

sampling point equidistant from four stations. Measurements

were made using a nested-plot design, with 5.6-m and 15-m

radius circles (appendix table 12). Percentage cover was

visually estimated. The species capture rates (corrected for

actual trap nights of operation) were compared to these

environmental variables.

Statistical Analysis

Data analysis was based on two major statistical goals: testing the hypotheses that animal abundance did not differ

among age-classes, moisture-classes, and locations, and number of species (species richness) did not differ among these

classes; and using exploratory statistics to associate individual species with individual habitat components and with

either age-classes or moisture-classes.

We used nonparametric analysis of variance (ANOVA) to

test the hypothesis that abundance (number of captures per

1000 trap-nights) of animals and species richness did not

differ among the age- and moisture-classes or locations. We

used detrended correspondence analysis (DCA) (Hill 1979a)

to explore the relations between animal abundances and

habitat-classes or environmental variables. Detrended

correspondence analysis is an ordination technique that

arranges a matrix of species’ abundances (communities) by

samples (stands) in low-dimensional space so that the communities occurring in each stand are represented in space

along several axes. Thus, many components are reduced to a

few important ones and variability is reduced. Communities

with similar species composition and relative abundances

occupy positions near each other within the space described

by the first and second DCA axes. In this way, it functions

as a principal components analysis. To determine whether

stands grouped themselves according to a physiographic

gradient, a plot of the detrended correspondence analysis

axes scores was examined to detect clustering.

To classify sites into community phases, two-way indicator

species analysis (TWINSPAN) (Hill 1979b) was used. This

method, based on a multi-level two-way partitioning of the

correspondence analysis scores, was used to classify species

into categories related to location or to age- or moistureclasses. Species found to be associated with old-growth

forests, from TWINSPAN analysis or from Spearman rank

correlations of animal abundances with stand age, were then

correlated (Spearman rank correlations) with individual environmental and vegetative variables to examine the relation

between animal species and individual habitat features.

Statistical significance was determined as P < 0.05. Means

are given + SE.

Results

Pitfall Trap Results

A total of 18 species of small mammals were caught in the

pitfall traps in 1984. Species richness was greatest at Mt.

Hood (16) and lower at Andrews (11) and Rogue-Umpqua

258
(13). Species’ abundances (number of captures per 1000 trapnights) varied by subprovince, with five species having significantly more captures at Mt. Hood and two more at RogueUmpqua (table 1). Trowbridge’s shrew, by far the most common species at all three locations, accounted for 62.6 percent

of all captures and ranged from 53.0 percent at Mt. Hood to

59.2 percent at Rogue-Umpqua and 75.8 percent at Andrews

(table 2). The Soricidae represented 76.9 percent of the total

captures. The western red-backed vole was the only nonshrew

species to represent more than 10 percent of the captures

(14.6 percent) mainly because of a relative abundance of

26.5 percent at Rogue-Umpqua.

Old-growth stands had 17 species, mature 15, and young 12.

The average number of individuals captured by age-class

was old-growth (49.5 + 5.0), mature (46.5 + 5.7), and young

(49.1 + 12.9). The deer mouse (R = 0.35, P = 0.01) and the

red tree vole (R = 0.37, P = 0.005) were significantly positively associated with stand age. No species were significantly associated with any age category in the chronosequence

(ANOVA, P < 0.05) (table 3). The average number of captures per stand was not different along the moisture gradient

(wet 47.3 + 5.7, mesic 50.8 + 7.5, dry 53.0 + 12.1), and no

species were significantly associated with the moisture gradient (ANOVA, P < 0.05) (table 3). DECORANA analysis

confirmed that age and moisture conditions did not influence

the mammal distribution (figs. 1,2). A location effect was

related to the pitfall captures (fig. 3), however. TWINSPAN

analysis showed no indicator species for age or moisture

conditions, but the Pacific jumping mouse, the montane

shrew, the heather vole, Townsend’s chipmunk, the northern

flying squirrel, and the ermine separated out as Mt. Hood

indicators; Townsend’s vole and the northern pocket gopher

were indicator species for Rogue-Umpqua.

No significant differences were found between the old and

new grids in species abundances or richness (P < 0.05). Significantly more small mammals were caught in young stands

(average 59.0 + 4.6) than in old-growth stands (29.8 + 4.2) in

1985. The mature-stand average (46.7 + 6.8) was not different from the other two age-categories. Fourteen species were

captured in 1985 compared to 10 in the same stands in 1984.

The four additional species (red tree vole, Pacific shrew,

Townsend’s chipmunk, and the montane vole) were represented only by 1 to 3 specimens each.

None of the small mammals captured in 1985 were significantly related to old growth in the chronosequence,

although five species showed an association with mature

or young stands (table 4). The coast mole and red tree vole

were only captured in mature and old-growth stands. The

only significant difference in age- or moisture-classes for

any species between 1984 and 1985 was the increased proportion of Trowbridge’s shrew caught in young stands in

1985 (x2 = 56.6, P < 0.0001).

Table 1-Signiflcant ANQVA values for small mammal abundance based on pitfall captures corrected for effort (number of

captures per 1000 trap-nights) related to subprovince location,

Oregon Cascades 1984

Species LocationaF-Value

Western red-backed vole RRU > HJA,MTH

Pacific shrew RRU > HJA, MTH

Deer mouse RRU > HJA

sorex spp. HJA > MTH, RRU

Pacific jumping mouse MTH > HJA, RRU

Northern flying squirrel MTH > HJA, RRU

Montane shrew MTH > HJA, RRU

Ermine MTH > HJA, RRU

Townsend’s chipmunk MTH > HJA, RRU

Heather vole captured only at MTH

25.59

11.33

4.81

45.37

35.64

16.40

8.10

3.91

2.91

P

<0.0001

<0.0001

0.01

<0.05

<0.0001

<0.0001

<0.0001

<0.0009

<0.03

0.06

a

 RRU = Rogue River-Umpqua; HJA = H.J. Andrews; MTH = Mt. Hood.

Table 2-Small mammal relative abundance (captures per 1000

trap-nights) from pitfall trapping by location, Oregon Cascades,

1984 (values in brackets are percentage of capture at that

location)

Species Rogue-Umpqua Andrews Mt. Hood

Trowbridge’s shrew

Western red-backed vole

sorex spp.

Montane shrew

Pacific shrew

Vagrant shrew

Marsh shrew

Water shrew

Pacific jumping mouse

Shrew-mole

Deer mouse

Northern flying squirrel

Coast mole

Townsend’s chipmunk

Creeping vole

Townsend’s vole

Heather vole

Northern pocket gopher

Douglas’ squirrel

Ermine

331.1 (59.2)

148.3 (26.5)

8.3 (1.5)

0.6 (<1.0)

39.0 (7.0)

2.8 (<1.0)

2.7 (<1.0)

0.0 (0.0)

1.2 (<1.0)

6.1 (1.1)

12.9 (2.3)

0.0 (1.0)

3.8 (<1.0)

0.0 (0.0)

1.7 (<1.0)

0.5 (<1.0)

0.0 (0.0)

0.6 (<1.0)

0.0 (0.0)

0.0 (0.0)

316.9 (75.8) 244.2 (53.0)

21.2 (5.1) 39.9 (8.7)

42.2 (10.1) 2.7 (<1.0)

1.7 (<1.0) 76.0 (16.5)

12.8 (3.1) 0.0 (0.0)

2.2 (<1.0) 12.3 (<1.0)

4.4 (1.1) 5.1 (1.1)

0.0 (0.0) 0.5 (0.0)

1.7 (<1.0) 35.1 (7.6)

8.8 (2.1) 11.2 (2.4)

1.1 (<1.0) 7.3 (1.6)

0.0 (0.0) 11.9 (2.6)

4.5 (1.1) 6.2 (1.3)

0.0 (0.0) 3.4 (<0.0)

0.6 (<1.0) 0.5 (<1.0)

0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 0.6 (<1.0)

0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 1.1 (0.0)

0.0 (0.0) 2.9 (<1.0)

Snap Trap Results

Eighteen species and 1493 individuals were captured in the

snap traps (table 5). Trowbridge’s shrew was the dominant

species at all locations (44.8-55.4 percent of all captures).

The Pacific shrew was the second most captured species

(24.1 percent) at Andrews, the montane shrew (14.2 percent)

at Mt. Hood, and the western red-backed vole (29.4 percent)

at Rogue-Umpqua. Species richness was not significantly

different between locations. The western red-backed vole, the

deer mouse, and the marsh, montane, and Pacific shrews

were significantly associated with location (table 6). This

259
Table 3-Caphwes of individual mammals in pitfall traps (mean number captured per stand, corrected for effort in 

parentheses) for age- and moisture-classes, Oregon Cascades 1984 

Western red-backed vole 

Townsend’s chipmunk 

Northern flying squirrel 

creeping vole 

Townsend’s vole 

Ermine 

Shrew-mole 

Deer mouse 

Coast mole 

Marsh shrew 

Montane shrew 

Sorer spp. 

Heather vole 

Pacific shrew 

location effect was verified by the DCA scores, which 

showed definite clustering (fig. 4). No similar moisture or 

age effects were found (table 7; figs. 5,6). 

The mean captures per stand were highest in mature (29.2 ? 

3.6) and lower in old-growth (26.3 * 2.5) and young stands 

(15.5 * 3.5) (ANOVA, F = 3.24, P < 0.05). The mature and 

’ 

95 (10.7) 86 (0.7)96 55 3(0.3)44 : 

- 

6 (0.7) 7 (0.6) 

l(O.1) l(O.1) 

l(O.1) 2 (0.2) 

T(l.0) -G (0.8) 

2 (0.2) 

4 (0.6) 12 (1.4) ‘i $ii 

2 (0.3) 4 (0.4) 7 (0.6) 

l(O.1) 4 (0.4) 7 (0.6) 

l(O.1) 6 (0.8) 47 (3.8) 

10 (1.6) 13 (1.4) 19 (1.7) 

17 (2.9) 

’ _I l(O.1) 

24 (2.8) 17 (1.4) 

54 (34.4) 264 (29.6) 334 (27.7) 

4 (1.3) 2 (0.2) 12 (1.1) 

2 (0.1) 

G(1.4) 24 (2.2) 

young values were significantly different, but the values for 

old-growth did not differ significantly from the other two 

age-classes. Captures of the Pacific shrew were significantly 

associated with mature stands (ANOVA, F = 3.62, P < 0.04). 

Spearman rank correlations showed the shrew-mole and 

Trowbridge’s shrew to have a positive association with stand 

age that neared significance (P = 0.06). The mean capture 

rates of all species did not differ along the moisture gradient 

(wet 26.4 k 3.7, mesic 30.3 * 3.9, dry 21.0 f 3.5). Only the 

260 
140 = Mount Hood 

q Rogue-Umpqua 

tJ *O 

60 

40 

20 

1 

0 20 40 60 80 100 120 140 1.40 

DCA 1 

Table 4-SmaU mammals significantly awxlated 

(ANOVA) with age of stand for pitfall captures, 

Oregon Cascades 198.5 

Species Stand age associatiw, 

Western red-backed vole Mature > old-gmwth 

Coast mole M&UIe 

Momme shrew Young > old-growth 

Tmwbridge’s shrew Young > old-growth 

vagrant shrew Mature > old-growth 

Table SSmaU mammal captures on the snap-trap grids, 

Oregon Cascades 1984 

Location 

247 262 217 126 

165 54 41 2.56 

52 12, 2 175 

46 15 1, 72 

8 6n 3 7, 

0 

1: 

50 52 

11 17 39 

14 13 3 30 

0 4 11 15 

0 3 11 14 

3 3 4 10 

7 1 1 9 

3 3 2 7 

0 1 1 * 

0 I 0 1 

1 0 0 I 

1 0 0 I 

1 0 0 1 

0 1 0 1 

559 555 379 1493 

Table 6-Small mammal species-abundance values corrected 

for effort (number of captures per 1000 trap-nights) snaptrapped In the Oregon Cascades, 1984, showing significant 

(ASOVA) associations with location 

Species 

capture locationn 

association F-value P 

western red-backed vole showed a relation to moisture conditions that was near significance, with average captures in 

mesic conditions (6.4) greater than dry (4.0) or wet (2.8) 

(ANOVA, F = 3.14, P = 0.06). 

No differences were found in the average number of small 

mammals caught per stand by location (Rogue-Umpqua, 

27.7 f 2.8; Andrews, 24.9 * 3.1; Mt. Hood, 24.0? 3.6). The 

western red-backed vole and the deer mouse were captured 

more frequently (P < 0.05) at Rogue-Umpqua, the marsh and 

the montanc shrew at Mt. Hood, and the Pacific shrew at 

Andrews (table 5). The marsh, montane, vagrant, and Pacific 

shrews all had significant (P < 0.05) Spearman rank COTrelations for latitude. 

Habitat Relations 

Pitfall results-In 1984, the shrew-mole had a significant 

positive association with very large trees in the overstory, 

a feature of old-growth stands. It was found in stands 

dominated by very large westem hemlock (R = 0.31, 

Western red-baEk.4 

V& RRU>HJA. RRU>h%TH 9.67 o.ooo3 

Deer mouse RRU>HlA 4.35 <o.oz 

Marsh shrew MTH>RRU 3.51 <O.M 

Montvle shrew MTH>HJA. MTH>RRU 20.03 <O.OOOl 

Pacific shrew HJA>RRU, HJA>MTH 13.23 <O.ooOl 

a RRU = Rogue River-“mpqua: HJA = H.J. Andrcws: Mm = ML “md. 

P = 0.02). The Douglas’ squirrel was caught at sites with 

very large sugar pine (R = 0.29, P = 0.03). and incense-cedar 

(R = 0.37.P = 0.005). 

The forest floor conditions at the capture sites differed. For 

example, the western red-backed vole, the red tree vole, and 

the deer mouse were all caught at sites with lichen (table 8). 

The Pacific jumping mouse’s capture locations were significantly associated with ground cover of moss and logs of 

decay-classes 3 and 4. The understory components at Pacific 

jumping mouse caphne sites included ferns. berryproducing, 

and deciduous shrubs (table 9) and tended to exclude broadleaf evergreen trees of all heightxlasses. The deer mouse 
= Mount Hood 

= Rogue-Umpqua 

Table ‘I-Captures of individual mammals In snap traps (mean number captured per stand corrected for effort in 

parentheses) for age- and moisture-classes, Oregon Cascades, 1984 

Moisture 

Western red-backed vole 

Townsend’s chipmunk 

Montme vole 

creeping vole 

Shrew-mole 

Deer mouse 

Coast mole 

Townsend’s mole 

Marsh shrew 

Montme shrew 

Pacific shrew 

Tmwbridge’s shrew 

Vagrant shrew 

sorer spp. 

Western pocket gopher 

Pacific jumping mouse 

Dusky-footed woodrat 

also was captured at sites with deciduous shrubs and trees 

(table 9). The western red-backed vole was positively associated with needleleaf evergreen trees in all height-classes. 

The montane shrew was the most widely distributed shrew 

based on shrubs and understory trees. It was positively associated (R = 0.51-0.59; P < 0.0001) with berry-producing 

shrubs of all three height-classes and deciduous shrubs in 

the first two height-classes (R = 0.42-0.46; P < 0.001). The 

montane shrew was the only species associated with evergreen shrubs (0.5-2 m; R = 0.36; P = 0.007). 

The northern flying squirrel was positively associated with 

large and medium sized (lo-50 f cm d.b.h.), tall (15-m) 

snags of decay-classes 3 and 4, as well as medium snags of 

decay class 5. The Douglas’ squirrel was found in stands 

with various-sized snags of decay-class 5. 

Pitfall resultsIn 1985, the red tree vole was captured at 

sites with small bigleaf maple, (R = 0.53, P = 0.04) large 

golden chinkapin, and very large grand fr. Also, it was 

highly correlated with sites with medium Pacific dogwood 

(R = 0.995; P < 0.0001). In 1984, it was associated only with 

262 
DCA 1 

q Old 

N 

medium canyon live oak (R = 0.29; P < 0.03). Limited consistency was found in vegetative and physical characteristics 

with which the small mammal species were positively or negatively associated between years. The red-backed vole was 

negatively associated with moss ground cover (R = 4.55, 

P = 0.04) in 1985 as was Trowbridge’s shrew (R = -0.58, 

P = 0.02). Both showed similar results in 1985. 

Table S-Qniflcant Spa-man rank correlations (P 5 0.05) 

for forest floor charscterlstics at the pitfall grids and selected 

small mammals captured, Oregon Cawades, 1984 

Table 9-SignUicaot Spesrmao rank correlations (P S 0.05) for 

understory and ground-cover characteristics at the pitfall grids 

and selected small mammals captured, Oregon Cascades, 1984 

Deer mowe 

Grasses (c-O.5 In) 0.45 

Fern (O-0.5 m) a47 

km (0.5-Z m) -0.44 

Mduoussblubs(O4Sm) 0.27 

Decid”O”S trees (O-0.5 m) 0.50 

Deciduous trees (0.5-Z m) 0.47 

Needle-leaf evergreen 

(2 m-midstory) 0.34 

Bellyproducing shrubs 

(00.5m) 0.29 

Dezidws *@.lbs(&O.5m) 0.29 

Deciduous Wee6 (O-O.5 m) 0.42 

Dezidwus trees (0.5-Z m) 0.32 

Deciduous sb~bs (2 mmidstay) 0.32 

Grass (oa.5 m) -0.43 

Fem(Oa5m, 0.31 

Berry-p-ducingshrubs 

(0.0.5 m) 0.50 

Evergrrmskmbs(O.O.5m) -0.42 

Deciduous shbs (CKxSm) 0.35 

D,%id”O”S shrub (0.5~2m) 0.43 

Benypmhcing shrubs 

(2 m-midJtor/) 0.54 

Most species varied behveen years in the characteristics 

of the sites at which they were caught, but few significant 

changes (Spearman rank correlations) occurred from positive 

to negative or from negative to positive. The more common 

result was that some characteristics were significantly asscciated one year and not the other. 

263 
The montane shrew was positively associated with berryproducing shrubs up to the midstory level (R = 0.26-0.50;

P < 0.05) and all deciduous shrubs (R = 0.34; P = 0.001) up

to 2.0 m high (table 10). The montane shrew, the marsh

shrew, and Trowbridge’s shrew were caught at sites where

ferns were a dominant ground cover. The Pacific shrew was

associated with broadleaf evergreen trees in the 0.5- to 2.0-m

zone (R = 0.50, P c 0.0001); it was negatively associated

with berry-producing and deciduous shrubs (R = 0.32) and

was caught at sites with evergreen shrubs (R = 0.47) up to

0.5 m tall (table 10). Forest floor characteristics associated

with the marsh shrew were logs of decay-class 1 (R = 0.26)

and 3 (R = 0.26), and with the montane shrew were lichen

and aspect (R = 0.30; P = 0.02); the vagrant shrew was

negatively associated (R = -0.38) with lichen (table 11).

Townsend’s mole was caught in traps with logs of decayclasses 2 to 5 (R = 0.27-0.32) nearby.

Discussion

The red tree vole, deer mouse, Trowbridge’s shrew and the

shrew-mole were the only small mammals positively associated with older stands in our study, and none seemed dependent on the availability of old growth. Corn and others (1988)

generally concur with this and found that only the red tree

vole was significantly associated with old-growth Douglas-fir

stands in their study of the Oregon Cascades. Raphael (1984,

1988c) and Raphael and Barrett (1984) listed 10 small mammals significantly associated with old-growth Douglas-fir forests in northern California, an area not dissimilar to RogueUmpqua. Trowbridge’s shrew can be discounted as an

old-growth associate because it is a very common species

that occurs in all ages of stands.

The mean species richness observed in this study was higher

and more variable on the chronosequence than that observed

by Corn and others (1988) or Raphael (1984). Species diversity studies are limited usually by the short temporal span of

sampling the environment, and, because studies such as ours

tend to rely on data gathered from many single sample surveys, erroneous correlations can be drawn (Wiens 1981b).

Greater replication, especially between years, would have

been useful. Temporal fluctuations in small mammal communities and their use of the environment are known to occur

(Asher and Thomas 1985, McCloskey 1975, Nel 1978,

Whitford 1976). The relations to habitat structure may be

highly variable if temporal shifts are occurring. Yet many

authors have shown or inferred that habitat factors are important in determining small mammal community structure (for

example, Dueser and Shugart 1979, McCloskey 1975, Morris

1984, Rosenzweig and Winakur 1969). Generally, the animals we trapped were found associated with different vegetation conditions between years and between times of year.

Table M-Significant Spearman rank correlations for

vegetative characteristics at snap-trap capture locations for

small mammals, Oregon Cascades, 1984

Species Vegetative characteristics R-value P

Western red-backed

vole

Trowbridge’s shrew

Marsh shrew

Pacific shrew

Grass (0-0.5 m)

Fern (0-0.5 m)

Evergreen shrub (0-0.5 m)

Fern (0-5.-2 m)

Berry-producing shrub

(2 m-midstoty)

Deciduous shrubs (2 mmidstory)

Needleleaf evergreen trees

(super canopy)

Fern (0-0.5 m)

Fern (0.5-2 m)

Grass (0-0.5 m)

Fern (0-0.5 m)

Fern (0.5-2 m)

Berry-producing shrubs

(0.5-2 m)

Needleleaf evergreen tree

(super canopy)

Berry-producing shrubs

(0-0.5 m) 

Evergreen shrubs (0-0.5 m)

Deciduous shrubs (0-0.5 m)

Broadleaf evergreen trees

(0-0.5 m)

Broadleaf evergreen trees

(0-0.5 m)

Needle-leaf evergreen trees

(0-0.5 m)

Needleleaf evergreen trees

(2 m-midstory)

Grass (0-0.5 m)

Fern (0-0.5 m)

Berry-producing shrubs

(0-0.5 m)

Evergreen shrubs (0-0.5 m)

Broadleaf evergreen trees

(0-0.5 m)

Berry-producing shrubs

(0.5-2m) 

Deciduous shrubs (0.5-2 m)

Broadleaf evergreen trees

(0.5-2 m)

Berry-producing shrubs

(2 m-midstory)

Evergreen shrubs (2 mmidstory)

Broadleaf evergreen trees

(2 m-midstory)

Broadleaf evergreen trees

(main canopy)

Needleleaf evergreen trees

(super canopy)

0.54 <0.00

-0.36 0.007

0.26 0.05

-0.28 0.04

-0.28 0.04

0.29 0.03

0.39 0.003

0.40 0.002

0.40 0.002

-0.31 0.02

0.35 0.007

0.28 0.04

0.29 0.03

-0.37 0.005

-0.41 0.002

0.47 0.0003

-0.32 0.02

0.50 <0.0001

0.61 <0.000l

-0.28 0.04

-0.28 0.03

-0.27 0.04

0.29 0.03

0.49 <0.000l

-0.38 0.003

-0.55 <0.0001

0.50 <O.OOOl

0.34 0.001

-0.40 0.002

0.26 0.05

-0.27 0.05

-0.41 0.002

-0.32 0.02

-0.45 0.0004

264
Table 11-Significant Spearman rank correlations for forestfloor characteristics at snap-trap capture sites for small

mammals, Oregon Cascades, 1984

Species Variable R-value P

Trowbridge’s shrew

Marsh shrew

Logs, decayclass 2

Fine litter

Logs, decay-class 1

Logs, decay-class 3

0.31 0.02

-0.30 0.03

0.26 0.05

0.26 0.05

Pacific shrew

Montane shrew

Lichen

Bare soil

Lichen

-0.37 0.006

-0.33 0.01

0.35 0.008

Townsend’s mole Bare rock -0.29 0.03

Coarse litter 0.28 0.04

Logs, decay-class 2 0.39 0.02

Logs. decay-class 3 0.30 0.03

Logs, decay-class 4 0.27 0.04

Logs, decay-class 5 0.32 0.02

Coast mole Bare rock -0.26 -0.05

This supports the speculation that temporal variation of habitat use occurred, which reduced the predictability of results

based on physiognomy.

We captured too few red tree voles for meaningful statistical

analysis or to conclude that they are related to older stands

of Douglas-fir. Such a relation has been suggested for this

species by other authors, and old-growth Douglas-fir is considered to be optimum habitat (Corn and Bury 1986, Franklin

and others 1981, Meslow and others 1981). We, and the

other authors, found the red tree vole primarily in mesic to

wet old-growth stands but the strong associations with medium Pacific dogwood, berry-producing shrubs, and deciduous

trees of smaller diameter may be a function of the small

sample size. They may have been selecting such vegetation

for food, however. Some of the animals we captured may

have been dispersing; most of the males were juveniles, and

the species is supposed to be arboreal and thus seldom found

on the ground (Maser and others 1981). The females were

mainly adult, and the sex ratio was almost equal. Although

we cannot draw any conclusion as to the function of terrestrial activity in the species, it obviously occurs. Terrestrial

nesting has been suggested for males (see Corn and Bury

1986). but we found equal numbers of females. Corn and

Bury (1986) caught predominantly females in their pitfall

traps.

The shrew-mole is an insectivore (Terry 1978, Whitaker and

Maser 1976) and, in a study in King County, WA, it was

found in forested areas with a high organic content to the

soil (Terry 1981). We found no such clear delineation of

habitat use, although the shrew-mole is a known shallow

burrower (Dalquest and Orcutt 1942). What associations did

exist in our study suggested an ubiquitous use of the environment, similar to the findings of Corn and others (1988).

Red-backed voles were negatively associated with sites with

fern as a dominant ground cover. Ferns were often found

with shrub or other understory cover, which suggests avoidance of such areas. As a mycophagist (Maser and others

1978, Ure and Maser 1982), the red-backed vole would be

expected to occur in conifer-dominated locations, at least at

the time of foraging for fungi. Negative associations with

Pacific dogwood and golden chinkapin support this. Lichens

are preferred food for red-backed voles in the Pacific Northwest (Vre and Maser 1982), and these voles were highly associated with areas of lichen ground cover in our study. Maser

and others (198 1) say that the distribution of red-backed

voles is influenced by the presence of rotting, punky logs.

Hayes and Cross (1987) found capture of the species to be

positively correlated with mean log diameter and size of the

log overhang, suggesting they use this space as travel corridors. Our captures were positively associated with logs of

decay-class 5, and many of our captures (Gilbert, pers. obs.)

were in the space under log overhangs.

The Soricidae were segregated somewhat in the western

Oregon Cascades. The vagrant shrew was found primarily in

higher elevation stands in the northern Oregon Cascades. Although the montane shrew was also associated with Mt.

Hood, it selected young stands and thus was significantly

associated with shrubby areas. The Pacific shrew was

restricted to the central and southern subprovince locations,

and it was a generalist in its use of the habitat. A lot of the

shrews from Andrews could not be identified to species

(other than that they definitely were not Trowbridge’s shrew)

because of mixed characters. Hennings and Hoffman (1977)

and Findley (1955) have discussed the taxonomic difficulties

with the montane, Pacific, and vagrant shrews, and, until the

taxonomic issue is resolved we decided to identify these

individuals only to genus. Terry (1981) could not correlate

the montane shrew with any vegetational factors and found

the vagrant shrew may have been excluded competitively by

Trowbridge’s shrew. Dalquest (1941) considered the vagrant

shrew to be dominant over Trowbridge’s shrew. Our findings

did not reject competitive exclusion by either species.

Although this study provided data on habitat usage by small

mammals, it showed the difficulties that occur in timerestricted analyses of vertebrate communities. Three of the

four species that had some old-growth association were either

weakly linked (the shrew-mole), relatively abundant species

in other age-classes (western red-backed vole and the deer

mouse), or both (the deer mouse). The deer mouse is of interest because other authors (for example, Gashwiler 1970a,

265
Hooven 1973, Hooven and Black 1976, Martell and Radvanyi

1977) consider the species to be most abundant in early successional forests. We trapped during a low in the population

cycle of the deer mouse in the Oregon Cascades, and the

species seemed to be related to older successional forests.

Anthony and others (1987) had similar results trapping riparian zones at Andrews in 1983, as did Raphael (1984) in northem California. Scrivner and Smith (1984) found the species

to be most associated with older successional stages (>80 yr)

of spruce-fir forests in Idaho, and Monthey and Soutiere

(1985) had similar results with a related subspecies in Maine

conifer forests. Sullivan (1979) stated that clearcut areas may

be population sinks for dispersing deer mice. Although the

species is not restricted by any means to older successional

stages, older forests may provide its best habitat.

Douglas’ squirrels were not sampled adequately by trapping

to provide any information on their dependence on oldgrowth. Data derived from avifauna surveys (Gilbert 1985)

provided no evidence of dependence on old-growth, although

Raphael (1984,1988) and Raphael and Barrett (1984) found

a significant positive correlation with stand age for the

Douglas’ squirrel in Douglas-fir forests in northern California.

Flying squirrel abundance was positively correlated with

large-snag density (Volz 1986, this study), suggesting this

habitat feature is necessary for suitable den trees and cavities

and may be limiting for that species. Maser and others

(1981), however, note that in locations in western Oregon

where these more suitable nesting sites have been removed

by logging, the species will build outside nests. We noticed

some of these nests as well.

One cautionary note is that virtually all the stands we studied

were natural and not the intensively managed stands that can

be expected in the future. Even the young stands had large

amounts of coarse woody debris and snag numbers almost

equivalent to old-growth stands. Vegetational features and

coarse woody debris in stands originating from logging rather

than fire are considerably different. We did sample a few

such stands with a previous history of logging, and these

young and mature stands had fewer species and individuals

in the small mammal communities than comparable natural

stands (Gilbert 1985). Other evidence supports such impacts

of logging on particular species; Corn and others (1988),

state that we have probably already eliminated much of the

red tree vole habitat by extensive logging of low elevation,

old-growth forests. The habitat features supporting the abundance of small mammals we observed in the Oregon Cascades will be reduced or eliminated in managed forests, creating a risk that species richness will decline (compare to

Weisbrod 1976) unless forest management practices provide

opportunities for maintaining such elements as coarse woody

debris and large trees in the managed Douglas-fir forests of

the future. Some of the species we captured were definitely

linked with these features of structural diversity (for example,

the red tree vole, flying squirrel, and western red-backed

vole). Therefore, although old-growth may not be itself limiting to very many species, the structural complexity of

naturally regenerated forests may be required for maintaining

small mammal diversity.

Acknowledgments

The Oregon Cascades study was made possible by the contributions of many people, including U.S. Forest Service

personnel. Effective field supervision was given by Wynn

Cudmore, and crew leaders Jim Reichel and Troy Cline at

Rogue River-Umpqua, Kathleen Fulmer at H.J. Andrews,

and Jeff Picton at Mount Hood in 1984. The 1985 crew

leader was Tony Fuchs. John Teburg, Dick Gilbert, Rich

Alldredge, and Betsy Piersone all assisted in data entry and

analysis. The hard-working field crews, primarily made up of

Washington State University wildlife students, were essential

to successful completion of the work.

This paper is contribution 119 of the Wildlife Habitat

Relationships in Western Washington and Oregon Research

ific Northwest Research Station, USDA Forest

266
Appendix

Table 12-Vegetation and site measurements for pitfall and snap trap grids, Oregon Cascades, 1984

I. Measurements on a 100 m

2

 area (5.6-m radius)

Forest floor:

1. Cover of logs by decay-class (%) (>lO cm diameter).

2. Litter depth at three points (01, 02) (mm).

3. Coverage of forest floor by various substrates: exposed bare rock, exposed bare mineral soil, fine organic litter (<l0-cm diameter),

coarse organic litter (>10-cm diameter), moss, lichen.

(Total - 100%).

A. Vegetation characteristics

4. Coverage of foliage by height interval and life form (%).

a. Height intervals

1. 0-0.5 m (100 m

2

 area)

2. 0.5-2.0 m (100 m

2

 area)

3. 2.0 m through midstory (shrubs and trees not entering main canopy) (707 m2 area).

4. Canopy trees forming main canopy layer (707 m

2

 area).

5. Super canopy trees (crowns extending well above main canopy layer) (707 m

2

 area).

b. Life forms

1. Herbs

2. Graminoids (grass & grasslike plants including sedges)

3. Ferns

4. Berry-producing ericaceous shrubs (Vaccinium and Gaultheria)

5. Evergreen shrubs (including shrubs of #4)

6. Deciduous shrubs (including shrubs of #4)

7. Deciduous trees

8. Broadleaf evergreen trees

9. Needleleaf evergreen trees

B Stand characteris tics

5. Number and species of small diameter, live trees (l-10 cm d.b.h.).

6. Number and species of medium diameter, live trees (l0-50 cm d.b.h.).

7. Number by decay-class of large diameter, medium tall snags (>50 cm d.b.h. and 5-15 m tall).

8. Number by decay-class of medium diameter, medium tall snags (l0-15 cm d.b.h. and 5-15 m tall).

9. Number by decay-class of short snags (any d.b.h., 1.5-5 m tall).

10. Number stumps (<l.5 m tall, natural or cut).

II. Measurements on a 707 m2 area (15-m radius, the distance to next trap station).

A. Stand characteristics

11. Number and species of large live trees (50-100 cm d.b.h.).

12. Number and species of very large live trees (>l00 cm d.b.h.).

13. Number by decay-class of large diameter, tall snags (>50 cm d.b.h. and 15 m tall).

14. Number by decay-class medium diameter, tall snags (l0-50 cm d.b.h. and >15 m tall).

B. Site characteristics

15. Surface water (presence/absence).

16. Type of water: I (intermittent stream), P (perennial stream); S (seep); 0 (pool/pond).

17. Rock outcrop (>l% of area) (presence/absence).

18. Exposed talus (>l% of area) (presence/absence).

19. Number of recent tree-fall mounds-pits with exposed roots and mineral soil.

267

Small Mammal Communities in the Southern

Washington Cascade Range

Stephen D. West

Author

STEPHEN D. WEST is an associate professor, Wildlife

Science Group, College of Forest Resources, University of

Washington, Seattle, Washington 98195.

Abstract

Small mammal faunas on the western slope of the southern

Washington Cascade Range were sampled to describe patterns of abundance along gradients of forest age and moisture

and to identify structural, vegetative, and environmental features associated with these patterns. Forty-five primary sites

were sampled by snap and pitfall trapping in 1984 and 1985,

resulting in the capture of 6751 individuals of 20 species, of

which 11 were regularly caught and statistically analyzed.

Four of these 11 species had different abundances between

years. The abundance of two species differed between forest

age-classes. The deer mouse was caught more often in oldgrowth than young forest, and the forest deer mouse was

caught more often in mature and old-growth than young

forest. The abundance of three species differed between

moisture-classes of old-growth forest. The marsh shrew was

caught more often in wet than in moderate old-growth forest,

and the southern red-backed vole was caught more often in

dry than in moderate or wet old-growth forest. In 1985 only,

the deer mouse was caught more often in moderate than in

wet old-growth forest. Elevation (404 to 1218 m) was not a

strong factor influencing small mammal abundance. Clustering sites by similarity coefficients (Jaccard’s) based on

mammalian presence-absence data or by the abundance of

frequently captured species (K-means) did not indicate a

mammalian community that was strongly organized with

respect to gradients of forest age or moisture. Habitat variables were weakly correlated with the abundance of mammalian species. The forest-floor small mammal community in

these naturally regenerated forests appears adapted to a broad

range of conditions related to forest age and moisture.

Introduction

The small mammal communities of the western slopes of

the southern Washington Cascade Range are composed of

species from two mammalian faunas (Dalquest 1948). Before

the last glacial period (Vashon-Wisconsin), species characteristic of the temperate forests of the Pacific coast, such

as the shrew-mole, Townsend’s mole, Trowbridge’s shrew,

the marsh shrew, Townsend’s chipmunk, the deer mouse,

Townsend’s vole, and the creeping vole, probably were the

most common species in the region. As glacial advance

proceeded, species associated with boreal conditions to the

north, such as the water shrew, the yellow-pine chipmunk,

the heather vole, the southern red-backed vole, the water

vole, and probably the forest deer mouse, moved southward

through the Cascades. At glacial maximum, species of both

faunas inhabited this unglaciated region. With retreat of

glacial ice, these species expanded their distributions generally north and east, colonizing the Cascades as habitats

became suitable (Dalquest 1948).

269
Small mammals, therefore, have inhabited the southern portion of the Washington Cascades longer than areas farther

north. If consistent associations occur between small mammals and naturally occurring gradients of forest age and

moisture, they might be expected to occur in the south. Do

unique species combinations occur along these gradients, or

are the constituent species capable of persisting in an array

of forest conditions? These questions have gained importance

in recent years, with increasing attention to the issue of

preserving old-growth forests. This study addresses the

relationships between small mammal communities and

naturally regenerated forests. Extrapolation of conclusions

from this work to potential relationships in managed forests

will be difficult, as discussed below.

The central objective of this paper is to describe the patterns

of small mammal species abundances over a gradient of forest age, and within old-growth forests, to describe patterns of

abundance over a gradient of moisture. This paper also will

investigate correlations between small mammal abundances

and selected environmental and vegetational variables.

years old), 9 sites in mature forest (80-190 years old), and 18

sites in old-growth forest (210-730 years old). All 27 oldgrowth sites were classified into moisture-classes, yielding 9

wet sites, 11 moderate sites, and 7 dry sites.

Small Mammal Sampling

Sampling techniques varied, reflecting the different natural

histories of the small mammal fauna. This study used four

techniques: vocalization frequencies of tree squirrels, track

records from smoked aluminum plates, snap-trapping, and

pitfall trapping. Vocalization frequency data were collected

as part of the spring avian surveys, using variable circular

plots (Manuwal, this volume). These data were used in conjunction with the other techniques to assess the presence or

absence of squirrels on the study sites. Data on track frequency (Carey and Witt 1991) were used in the same fashion.

They were particularly useful in establishing the presence of

squirrels and chipmunks, species not sampled efficiently by

snap or pitfall trapping. By far the most important techniques,

and the ones yielding information on relative abundance,

were snap-trapping and pitfall trapping.

Methods As noted by Briese and Smith (1974), Bury and Corn (1987),

Study Sites

This work was conducted on 54 sites on the western slopes

of the southern Washington Cascade Range. Sites were

located predominantly within the Western Hemlock Zone

(Franklin and Dymess 1973) at elevations ranging from 404

to 1218 m. Some of the higher elevation sites extended into

the Pacific Silver Fir Zone. Most forested sites had Douglasfir as the dominant tree species, although wet old-growth

forests had a large proportions of western redcedar. The sites

chosen for small mammal studies form a subset of a large

number of sites investigated botanically. For an extensive

treatment of the vegetational composition and structure of

the study stands, see Spies (this volume) and Spies and

Franklin (this volume).

and Williams and Braun (1983), capture efficiency differs

consistently between snap and pitfall traps. In general, pitfall

traps sample nonjumping rodents and insectivores more

effectively than do snap traps, which sample more agile

rodents most effectively. Species lists exclusively derived

from one technique will reflect this sampling bias. Estimates

of relative abundance in this paper consequently combined

information from both techniques. West (in press) describes

the snap-trapping methods used in this study and a rationale

for developing this particular protocol. Briefly, we used two

Museum-Special traps at each of 144 trapping stations. Most

of the traps were new-model Museum Specials with plastic

treadles (West 1985). Stations were arrayed on a 12 by 12

grid with 15-m interstation distances. Traps were baited with

peanut butter and whole oats, and operated for four consecOf the 54 sites, 8 were on areas recently clearcut (cut 6-21 utive days. We trapped each site once during July and August

years previously). These sites were sampled for small mam- in both years. Trapping grids were relocated within sites

mals in 1984, but could not be included in sampling during between years to avoid sampling potentially depleted popu1985. One forested site was sampled only in 1985, and the lations in 1985. Corn and Bury (1990) also describe methods

remaining 45 sites were sampled in both years. These 45 of pitfall trapping that were developed primarily for sampling

sites (see frontispiece), which ranged in size from 51 to 1690 amphibians and reptiles. Mammals and herpetofauna were

ha (mean size = 488 ha), are the focus of this paper. sampled simultaneously. Pitfall arrays consisted of 36 traps

on a 6 by 6 grid with 15-m spacing between traps. Pitfall

Sites were chosen based on several physical and vegetational traps were operated continuously for 30 to 34 days each fall,

characteristics (Carey and Spies, this volume), and subse- beginning in October. Traps were checked once a week and

quently placed into classes along gradients of age and moist- were relocated within sites between years. All captured aniure (Spies and Franklin, this volume). Of the 45 sites, 36 mals were given to the Burke Memorial Museum at the

were judged sufficiently similar in site moisture conditions University of Washington.

(moderate vs. very wet or dry) to be compared along an age

gradient. Elimination of very wet or dry sites resulted in a

chronosequence consisting of 9 sites in young forest (55-75

270
Vegetation Sampling 

Information on the physical features of the sites and their 

vegetational composition and structure was gathered on the 

snap and pitfall trapping grids in a similar manner. Variables 

appropriately measured at a small scale, such as coverage of 

the forest floor by different substrates, percentage cover of 

logs by decay-class, and percentage cover of herbs, ferns, 

most shrubs, and small trees, were recorded on 100-m’ circular plots. Variables of larger scale, such as large trees, large 

standing snags, and site characteristics (presence and type of 

water, rock outcrops, or talus) were measured on 707-m circular plots centered on rhe smaller plots. Centers of the concentric plots were equidistant from four pitfall traps or snaptrapping stations, resulting in 9 vegetation plots on the pitfall 

grids and 16 plots on the snap-Impping grids. Because these 

grids were relocated between years, we collected data from 

different grids each year. 

Data Analyses 

This paper is concerned with the responses of small mammal 

populations at the site or stand scale. Abundance patterns 

were. characterized, and correlations with habitat features 

were sought, from summations of snap and pitfall captores in 

each year with site and vegetation variables averaged over all 

plots in both years. Such an approach was taken to provide a 

comprehensive data seL As discussed above, combining snap 

and pitfall data enlarges sample sizes and helps reduce the 

known biases of each method. By combining information 

from all vegetation plots (n = 50), a good average value could 

be obtained for most variables. All statistical work was done 

with SYSTAT microcomputer programs (Wilkinson 1988). 

Counts of captured animals are reported as numbers per 100 

trap-nights. For snap-trap data, these coonts were corrected 

for empty, snapped traps, and for traps occupied by another 

species. Because pitfall traps were multiplecapture imps, 

such adjustments to the capture totals were unnecessary. 

Before statistical analyses, capture data were transfomwd 

logarithmically @(x+1)). 

All variables measured on the vegetation plots were inspected for statistical normality and transformed using logarithmic @1(x+1)), square root ((x+3/8)), and arcsine (am(x)) 

functions as appropriate. Redundant variables were either 

eliminated from furtber analysis or combined with similar 

variables after inspecting the Pearson correlation matrix of 

the data. Of the field-recorded variables, a subset of 3 1 variables consisting of original and combined variables was 

used to examine correlations between small mammal 

abundance and habitat features (appendix table 7). 

Small mammal responses to forest-age and moisture gradients, and to selected environmental variables were investigated in three general ways. Analyses of variance (repeated 

measures ANOVA) of small mammal abundance with forest 

age (young, mature, and old-growth forest) and moistureclasses (dry, moderate, and wet old-growth forest) assessed 

the variation in abundance for successive years aaoss both 

gradients. When significant class-by-year interactions were 

present, I used separate one-way ANOVAs with Tukey’s 

HSD test for multiple comparisons. I used Pearson correlation coefficients to test for associations with selected environmental parameters, and multiple regression to assess the 

consistency and strength of association between vegetative 

physiographic variables and the abundance of mammals. The 

ANOVAs and correlation coefficients were calculated for 

species for which at least 40 individuals were captured. The 

composition of mammalian communities, based on the 

presence or absence of species for each site, was obtained by 

combining capture totals in both years with information from 

the aviao surveys and the track plates. The resulting matrix 

of presence-or-absence data by sites (species in table 1 plus 

the Douglas’ squirrel) was clustered hierarchically by 

Jaccard’s similarity coefficients (Jaccard 1912) to reveal 

community pattern along the forest-age and moisture 

gradients. In addition, K-means clustering (Hartigan 1975) 

on the abundance of the most frequently captured species 

(11 species) was used to investigate community pattern from 

a different perspective. 

Table ISmall mammals captured in snap (July and 

August) and pltfall traps (October and early November) 

on 45 forested sites in the southern Washington Cascade 

RaIIge 

Comon name 1984 1985 TOtal 

hsectivora 

Vagrant shrd 

Montane shrew” 

Water shrew 

Marsh shrew 

Trowbridge’s shrewb 

Unidentified shrew 

ShW-IllOk 

Coast male 

Lagomorpha 

Pika 

Rodemia 

Yellow-pine chipmunk 

Townsend’s chipmunk 

Unidentified chipmunk 

Northern flying squinel 

Northern pocket gopher 

Deer mouse 

20 48 68 

452 859 1,311 

6 3 9 

7.1 25 46 

1,105 x41 1.946 

26 12 38 

116 115 231 

11 10 21 

1 1 2 

1 11 12 

26 16 42 

0 1 1 

2 27 29 

0 1 1 

101 125 226 

271