168 C. Maisonneuve, S. Rioux Agriculture, Ecosystems and Environment 83 2001 165–175
where O
ij
is the number of captures of species i in habitat j. Since three habitat types were compared, a
niche breadth value of 1 indicates that a species is only present in one habitat type, whereas a maximum
value of 3 indicates that a species is distributed evenly in all three habitat types. This value of niche breadth
can be used as a tolerance index to habitat modifica- tions; species with great niche breadths are considered
tolerant and to modifications of their habitat and vice versa Best et al., 1979; Stauffer and Best, 1980.
Proportions of insectivores and rodents within each habitat type were compared with G-tests Scherrer,
1984: 484. When this test indicated heterogeneity between the three habitat types, multiple comparison
tests Scherrer, 1984: 488 were carried out to de- termine to which habitat this was due. The G-tests
were also used to compare proportions of pest species among the small mammal communities. Two species
were considered as potential pests: Microtus pennsyl- vanicus, and Mus musculus.
Comparison of observed numbers of individual species with numbers expected according to adjacent
land use availability was carried out with G-tests. This test was carried out for species for which at least
20 captures were obtained in the trap lines. Microtus pennsylvanicus and M. musculus were grouped as
pests species for this analysis.
Table 1 Mean, standard deviation S.D. and total numbers of individuals of each species of small mammals captured within each of three riparian
habitat types and number of sites on which they were detected in agricultural landscapes of southern Qu´ebec, 1995–1997 Species
Habitat Herbaceous
Shrubby Wooded
Mean S.D.
Total Sites
Mean S.D.
Total Sites
Mean S.D.
Total Sites
S. cinereus 15.5
6.6 92
6 27.7
7.6 166
6 26.3
5.9 158
6 S. fumeus
0.3 0.5
2 2
0.8 1.5
5 2
4.0 4.2
24 6
Sorex hoyi 0.2
0.4 1
1 0.5
0.8 3
2 0.2
0.4 1
1 B. brevicauda
6.3 2.6
42 6
9.5 4.2
57 6
8.8 3.9
53 6
Condylura cristata 0.7
0.8 4
3 0.5
0.8 3
2 M. pennsylvanicus
4.5 4.0
27 5
3.5 1.3
21 6
2.2 2.6
13 3
C. gapperi 2.2
2.9 13
3 2.3
1.7 14
4 6.2
5.7 37
6 M. musculus
1.2 1.3
7 3
0.3 0.5
2 2
0.8 0.7
5 4
P. maniculatus 0.5
1.1 3
1 10.8
8.6 65
6 Napaeozapus insignis
0.2 0.4
1 1
0.5 0.8
3 2
Z. hudsonius 25.3
7.1 152
6 35.5
14.8 213
6 41.8
13.3 248
6 Tamiasciurus hudsonicus
0.8 1.5
1 1
0.2 0.4
1 1
1.0 0.8
6 4
Tamias striatus 0.3
0.5 1
1 Mustela herminea
0.5 0.8
3 2
1.7 1.5
10 4
0.3 0.5
2 2
Total 344
496 620
3. Results
3.1. Small mammals A total of 1460 individual small mammals belong-
ing to 14 species were captured Table 1. Total num- ber of captures increased gradually with increasing
complexity of vegetation structure: 23.6 of indi- viduals were captured in herbaceous riparian strips,
34.0 in shrubby strips, and 42.5 in wooded strips Table 2. All 14 species were detected in wooded
strips, 11 species in herbaceous strips and 12 in shrubby strips. Diversity was significantly lower in
shrubby strips than in wooded or herbaceous strips, which had similar diversity indices. Relatively high
values were obtained for overlap indices between habitat types: 0.976 between herbaceous and shrubby
strips, 0.918 between herbaceous and wooded strips, and 0.931 between shrubby and wooded strips, indi-
cating that small mammal communities differed much between herbaceous and wooded strips.
The most abundant species were Zapus hudsonius, Sorex cinereus, and Blarina brevicauda with 42.1,
28.5 and 10.4 of the captures, respectively Table 1. These species were captured on all the sites and had
highest niche breadth values 2.89, 2.84 and 2.95, respectively. M. pennsylvanicus had a niche breadth
C. Maisonneuve, S. Rioux Agriculture, Ecosystems and Environment 83 2001 165–175 169
Table 2 Number of individuals, number of species, and diversity indices of small mammals caught in three riparian habitat types in agricultural
landscapes of southern Qu´ebec, 1995–1997 Habitat
Herbaceous Shrubby
Wooded Total number of individuals
344 496
620 Mean number of individualssite
57.3 82.7
103.3 Minimum number of individualssite
36 73
75 Maximum number of individualssite
76 105
115 Total number of species
11 12
14 Mean number of speciessite
6.5 6.8
9.3 Minimum number of speciessite
4 6
7 Maximum number of speciessite
9 9
12 Shannon’s diversity index
a
0.665
A
0.613
B
0.744
A a
Indices followed by identical letters did not differ significantly Hutcheson’s test.
value of 2.78 and, contrarily to the three preceding species whose abundance increased with complexity
of vegetation structure, occurred mainly 44.3 in herbaceous strips. A niche breadth value of 2.36 was
obtained for Clethrionomys gapperi. The species was detected on all six sites covered in wooded strips,
where 58 of all individuals captured. Over 95 of all Peromyscus maniculatus were captured in wooded
strips, which led to a very low niche breadth value 1.09 for this species. A relatively low niche breadth
value 1.59 was also obtained for S. fumeus with 75 of all captures made in shrubby strips. Other species
represented less than 1 of captures.
Proportions of rodents and insectivores differed sig- nificantly between the three habitat types G = 9.58,
d.f. = 2, P 0.01. A multiple comparisons test indicated that rodents were significantly more abun-
dant in wooded strips 61 than in shrubby strips 52, but failed to detect any difference in the propor-
tion of rodents between herbaceous strips 59 and
Table 3 Observed and expected numbers of individual species according to land use adjacent to trapping stations in riparian strips located in
agricultural landscapes of southern Qu´ebec, 1995–1997
a
Species Cereal
Pastures Prairies
G-test Observed
Expected Observed
Expected Observed
Expected d.f.
Value P
S. cinereus 39
45 72
52 177
190 2
4.128 0.127
B. brevicauda 5
14 27
16 54
57 2
7.360 0.025
P. maniculatus 3
7 12
8 29
29 2
2.451 0.294
Z. hudsonius 25
41 60
47 173
171 2
5.511 0.064
Pest species
b
10 8
10 9
29 32
2 0.423
0.809
a
Fisher’s exact test.
b
Mus musculus and Microtus pennsylvanicus combined.
the two other habitat types. Even though proportions of rodents were similar in herbaceous and wooded
strips, species composition differed. M. pennsylvani- cus and M. musculus were more abundant in herba-
ceous strips, P. maniculatus and C. gapperi being es- sentially present in wooded strips.
The proportion of pest species in the three habitat types varied significantly G = 21.73, d.f. = 2, P
0.001. A multiple comparisons test indicated that this was due to a significantly higher proportion of pest
species in herbaceous strips 10.0 than in shrubby 4.7 or wooded 2.8 strips. Even if the total num-
ber of captures increased from herbaceous to wooded strips, the abundance of pest species decreased with
complexity of vegetation structure.
With the exception of B. brevicauda, which was almost three times less abundant than expected at
stations adjacent to cereals, land use had no ef- fect on species distribution within the buffer strips
Table 3.
170 C. Maisonneuve, S. Rioux Agriculture, Ecosystems and Environment 83 2001 165–175
Table 4 Mean, standard deviation S.D., and total numbers of individuals of each species of herpetofauna captured in each of the three riparian
habitat types and number of sites in which they were detected in agricultural landscapes of southern Qu´ebec, 1995–1997 Species
Habitat Herbaceous
Shrubby Wooded
Mean S.D.
Total Sites
Mean S.D.
Total Sites
Mean S.D.
Total Sites
Ambystoma maculatum 0.3
0.8 2
1 Eurycea bislineata
0.3 0.7
2 1
0.2 0.4
1 1
0.3 0.5
2 2
B. americanus 2.8
2.9 17
4 6.7
7.6 40
6 16.7
9.5 100
6 Hyla cricifer
0.2 0.4
1 1
0.7 1.1
4 2
Rana catesbeiana 0.2
0.4 1
1 0.2
0.4 1
1 Rana septentrionalis
0.5 0.8
3 2
1.3 1.5
8 3
1.0 1.2
6 3
Rana clamitans 0.5
0.8 3
2 0.2
0.4 1
1 0.3
0.5 1
1 R. sylvatica
0.2 0.4
1 1
3.8 4.9
23 4
1.0 1.0
6 4
R. pipiens 1.2
2.6 7
1 0.8
1.1 5
3 14.7
11.4 88
6 Thamnophis sirtalis
0.5 0.8
3 2
0.2 0.4
1 1
Storeria occipitomaculata 0.2
0.4 1
1 0.2
0.4 1
1 Total
35 89
205
3.2. Herpetofauna A total of 329 individual amphibians and reptiles be-
longing to 11 species were captured Table 4, i.e., nine amphibians with more than 98 of all captures, and
two reptiles. All occurred in shrubby strips, whereas eight species were detected in the other habitat types
Table 5. Diversity was significantly lower in herba- ceous and wooded strips than in shrubby strips. Rel-
atively high values were obtained for overlap indices between herpetofaunal communities of the different
habitat types: 0.847 for herbaceous and shrubby strips,
Table 5 Number of individuals, number of species, and diversity indices of herpetofauna caught in three riparian habitat types in agricultural
landscapes of southern Qu´ebec, 1995–1997 Herbaceous
Shrubby Wooded
Total number of individuals 35
89 205
Mean number of individualssite 5.8
14.8 34.2
Minimum number of individualssite 4
7 Maximum number of individualssite
12 36
55 Total number of species
8 11
8 Mean number of speciessite
2.2 4.2
4.0 Minimum number of speciessite
2 3
Maximum number of speciessite 5
7 5
Shannon’s diversity index
a
0.688
A
0.715
B
0.456
A a
Indices followed by identical letters did not differ significantly Hutcheson’s test.
0.862 for herbaceous and wooded strips, and 0.760 for shrubby and wooded strips.
Bufo americanus, Rana pipiens and Rana sylvatica were the dominant species with 47.7, 30.4 and 9.1
of captures, respectively Table 4. The majority of captures of B. americanus 89 and R. sylvatica
97 were made in wooded and shrubby strips, giving niche breadth values of 2.10 and 1.67, respec-
tively. In R. pipiens, 88 of captures were made in wooded strips, for a niche breadth value of 1.29. Rana
clamitans, with 5.2 of all captures, was encountered mostly in shrubby and wooded strips. The other seven
C. Maisonneuve, S. Rioux Agriculture, Ecosystems and Environment 83 2001 165–175 171
species represented less than 2 of captures and niche breadth values were not calculated.
4. Discussion
