Download The low performance of forest versus rural coyotes in northeastern

ECosCIENCE
9 (1) : 44-54 (2002)
The low performance of forest versus rural coyotes
in northeastern North America: Inequality between
presence and availability of prey1
Marie-Claude RICHER, Michel CRÊTE2& Jean-Pierre OUELLET, Département de biologie, Université du Québec
à Rimouski, 300 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada.
Louis-Paul RIVEST, Département de mathématiques et de statistique, Université Laval, Québec G1K 7P4, Canada.
Jean HUOT, Département de biologie, Université Laval, Québec G1K 7P4, Canada.
Abstract: Coyotes, which originate from central and southwestern North America, recently extended their range into forests
of the Northeast. Forest coyotes occur in lower densities, have lower body reserves, and consume more fruits during
summer than their counterparts occupying adjacent rural landscapes. We hypothesised that the forest landscape offered less
animal prey to coyotes during summer than did the rural landscape. Coyote densities were higher in the rural landscape
(2.7 animals 10 km-2) than in the forest landscape (0.5 animals 10 km-2) during the summer of 1997. During the summers of
1996 and 1997, coyotes in both landscapes fed mainly on wildberries (> 45% of dry matter intake), small mammals (> 10%),
and snowshoe hare (> 10%). The biomass of the most abundant animal prey, snowshoe hares, was greater in the forest landscape
(1.24 and 1.53 kg ha-1 in 1996 and 1997, respectively) than in the rural landscape (0.46 and 0.40 kg ha-1 in corresponding
years). The biomass of the other major animal prey (small mammals), was comparable in both landscapes but irrupted during
the second summer (0.09 and 0.50 kg ha-1 in 1996 and 1997, respectively). The biomass of fruits remained relatively constant
in the rural landscape during the summers of 1996 and 1997 (ª 6 kg ha-1), but it tripled in the forest landscape during the
second year (1.69 kg ha-1 in 1996 versus 5.30 kg ha-1 in 1997). Contrary to our prediction, the availability of animal prey in
the forest landscape exceeded that in the rural landscape. Our results illustrate that the presence of prey does not correspond
to its availability to predators. Coyotes appear poorly adapted for hunting in dense forest vegetation during summer and
compensate for shortage of animal prey by consuming more berries.
Keywords: Canis latrans, coyote, feeding behaviour, hare, Lepus americanus, small mammals.
Résumé : Le coyote, qui provient du Centre et du Sud-Ouest de l’Amérique du Nord, a récemment étendu son aire de répartition
dans les forêts du Nord-Est du continent. Les coyotes forestiers vivent à faible densité, possèdent des réserves corporelles
amoindries et consomment plus de fruits, durant l’été, que les coyotes ruraux. Nous avons posé l’hypothèse que le paysage
forestier offrait moins de proies animales durant l’été que le paysage rural. La densité des coyotes était plus élevée dans le
paysage rural (2,7 animaux 10 km-2) que dans le paysage forestier (0,5 animal km-2) durant l’été 1997. Pendant les étés de
1996 et 1997, les coyotes des deux paysages se nourrirent principalement de fruits sauvages (> 45 % de la prise alimentaire,
base sèche), de petits mammifères (> 10 %) et de lièvres (> 10 %). La biomasse de la proie la plus abondante, le lièvre
d’Amérique, dépassait, dans le paysage forestier (respectivement 1,24 et 1,53 kg ha-1 en 1996 et 1997) celle mesurée dans le
paysage rural (0,46 et 0.40 kg ha-1 pour les années correspondantes). La biomasse de l’autre proie animale principale, les
petits mammifères, demeura très semblable dans les deux paysages mais fit irruption au cours du deuxième été (respectivement
0,09 et 0,50 kg ha-1 en 1996 et 1997). La biomasse de fruits resta relativement constante en 1996 et 1997 dans le paysage
rural (ª 6 kg ha-1), mais elle tripla dans le paysage forestier durant la deuxième année (1,69 contre 5,30 kg ha-1).
Contrairement à notre prédiction, la disponibilité de proies animales dans le paysage forestier dépassa celle du paysage rural.
Nos résultats démontrent que la présence de proies ne correspond pas à leur disponibilité pour les prédateurs. Les coyotes
semblent mal adaptés pour la chasse dans la végétation dense des forêts au cours de l’été et compensent la rareté de proie
animale par une consommation accrue de fruits.
Mots-clés : Canis latrans, comportement alimentaire, coyote, Lepus americanus, lièvre d’Amérique, petits mammifères.
Introduction
Historically, the coyote (Canis latrans Say) was mainly
restricted to the open grass prairies and plains of central and
western North America (Young & Jackson, 1951). The
opening of the landscape caused by human settlement, combined with the eradication of wolves (Canis lupus L.) and
coyotes’ adaptiveness, paved the way for range expansion
northward and eastward through New England, Québec, the
1Rec. 2001-05-17; acc. 2001-11-19.
2Author for correspondence.
Mailing address: Société de la faune et des parcs du Québec, Direction de la recherche sur
la faune, 675 boul. René-Lévesque Est (BP 92), Québec G1R 5V7, Canada, e-mail:
[email protected]
Maritimes, the Yukon, and Alaska (Moore & Parker, 1992).
Coyotes were first observed in southwestern Québec in
1944 (Young & Jackson, 1951) and in the Bas-SaintLaurent region of southeastern Québec in the early 1970s
(Georges, 1976).
The eastward range expansion of coyotes was accompanied by an apparent increase in body size (Thurber &
Peterson, 1991; Larivière & Crête, 1993), which makes possible group hunting during winter and killing of large prey
(Messier, Barrette & Huot, 1986; Patterson, Benjamin &
Messier, 1998). The arrival of coyotes in southeastern
Québec seriously affected two ungulate species: whitetailed deer (Odocoileus virginianus Zimmermann) and cari-
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ÉCOSCIENCE, VOL. 9 (1), 2002
Methods
STUDY AREA
The study area covered 1,200 km2 of rolling hills on the
south shore of the St. Lawrence River in southeastern
Québec, with an altitude varying between 220 and 660 m
(Figure 1). Annual precipitation averages 1,105 mm in the
centre of the study area, with 33% falling as snow (Environment Canada, 1993); snow cover persists from early December to late April. As a result of the decline of agriculture
in the region, the rural landscape (473 km2) was a mosaic
of cultivated fields (59 km2) interspersed with old fields
and regenerating forest (58 km2), wood lots (348 km2), and
open water (8 km2). Contiguous forest blocks of various
ages covered the rest of the study area (721 km2) and were
designated as the forest landscape for the study (Tremblay,
Crête & Huot, 1998). The study area occupies a transition
zone between the northern hardwood forest and the boreal
forest (Rowe, 1972; Marie-Victorin, 1995). Dominant tree
species include sugar maple (Acer saccharum Marsh.) and
yellow birch (Betula alleghaniensis Britton) on hill tops and
south-facing slopes and balsam fir (Abies balsamea [L.]
Mill.), white birch (Betula papyrifera Marsh.), aspen
(Populus tremuloides Michx), and black spruce (Picea mariana [Mill.] BSP.) elsewhere. Logging was widespread during the last century and has affected most forest stands.
Large mammals common to the area are moose (Alces alces
L., ª 0.18 km-2; Lamoureux & Pelletier, 1998), white-tailed
deer, (ª 1.1 km-2; Lamoureux, 1997) and black bear (Ursus
americanus Pallas, ª 0.4 km-2; Lamontagne, Jolicoeur &
Lafond, 1996, unpubl. data). Carnivores susceptible to interfere with coyotes include red fox, fisher (Martes pennanti
Erxleben), marten (Martes americana Turton), and Canada
lynx (Lynx canadensis Kerr).
COYOTE DENSITY
In a first step, we estimated the total number of coyotes
inhabiting the entire study area by a mark-recapture technique, using the Lincoln-Peterson model (Seber, 1982) as
modified by Chapman (1951). Coyotes were marked with
radio-collars or tags during the autumns of 1994 (n = 16),
1995 (n = 26), and 1996 (n = 18) (Tremblay, Crête & Huot,
Riviere-du-Loup
`
N
5
20
18
Saint-Honore´
Cabano
185
Saint-Josephde-Kamouraska1
85
Study area
Rural
Forest
Sampling grid
Permanent road
28
2
bou (Rangifer tarandus L.) (Poulle et al., 1993; Crête &
Desrosiers, 1995; Dumont et al., 2000). It also probably
affected bobcat (Lynx rufus Schreber) and red fox (Vulpes
vulpes L.) through interference competition and/or intraguild
predation (Harrison, Bissonette & Sherburne, 1989; Litvaitis
& Harrison, 1989).
Likely due to the landscape features where the species
has evolved (Nowak, 1979), coyotes are well adapted to
open and semiopen habitats (Young & Jackson, 1951)
although they have colonised forested areas in northeast
and northwest North America (Messier & Barrette, 1982).
However, eastern boreal forests seem to provide marginal
habitat for coyotes. Densities in forests of the Gaspé peninsula were among the lowest ever recorded (Samson &
Crête, 1997: 0.2-0.3 coyotes 10 km-2) whereas they vary
between 3 and 20 coyotes 10 km-2 in southern United States
and western Canada (Bowen, 1982; Pyrah, 1984; Andelt,
1985; Hein & Andelt, 1995). In the boreal forest of Alberta,
coyote densities fluctuated from 1.4 to 4.4 coyotes 10 km-2
and were strongly related to snowshoe hare (Lepus americanus Erxleben) densities (Todd, Keith & Fisher, 1981);
they reached 0.1 coyote 10 km-2 in Yukon during the cyclic
low of hare (O’Donoghue et al., 1997).
Body mass, fat, and protein reserves were lower in
summer than in any other season for eastern coyotes frequenting boreal forests (Poulle, Crête & Huot, 1995). This
suggests that coyotes face food shortage in such habitat during summer (Lefebvre et al., 1999; Larivière et al., 2001).
Along with low body reserves in summer, these coyotes
also had low fecundity rates (Poulle, Crête & Huot, 1995;
Dumond & Villard, 2000). Coyote feeding behaviour was
studied in two adjacent landscapes of southeastern Québec:
mixed forest-agricultural (rural) and forest landscapes
(Tremblay, Crête & Huot, 1998). During the period of pup
initiation (15 July to 1 October), forest coyotes consumed
more wildberries, were more active, travelled at a higher
rate, and had lower body size and mass than did rural coyotes. Because these characteristics may affect survival and
fecundity, the authors concluded that forest landscapes were
marginal habitats for coyotes in summer, compared to rural
landscapes (see also Crête et al., 2001).
We hypothesised that the forest landscape, during summer, represents a habitat of lower quality for coyotes than
the rural landscape because the former is characterised by a
lower abundance of animal prey (Tremblay, Crête & Huot,
1998), thereby forcing coyotes to compensate with wildberries. Alternatively, animal prey could be harder to capture
because of the vegetative cover (Harrison, 1992a) since
coyotes depend greatly on their vision for prey detection
(Wells & Bekoff, 1982). The rural landscape offers greater
habitat diversity, prey choice, and feeding opportunities for
coyotes than do boreal forests (Chambers et al., 1974; Person,
1988; Person & Hirth, 1991), in addition to being possibly
more suitable for small mammal irruption (Jedrzejewski &
Jedrzejewska, 1996). Assuming a top-down trophic dominance in our study area (Power, 1992), we predicted that the
availability of animal prey for coyotes would be lower in
the forest than in the rural landscape. To test our prediction,
we estimated coyote densities, food habits, and the biomass
of their principal prey in both rural and forest landscapes
during the summers of 1996 and 1997.
Pohenegamook
´ ´
U.S.A.
2
0
2
4
6
8 10 km
FIGURE 1. Location of the study area in southeastern Québec and distribution of sampling grids for main prey in the rural and the forest landscapes.
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45
RICHER ET AL.: FOOD OF FOREST AND RURAL COYOTES
1998) and recaptured by trappers during the trapping season
(18 October – 1 March). We determined the total harvest
size of coyotes and the number of marked individuals
through a telephone survey of all local trappers in 1995,
1996, and 1997.
In a second step, we estimated the relative density of
coyotes in the rural and the forest landscape using the number of scats found per 100 km-day along trails and gravel
roads, an index linearly related to coyote density (Knowlton
& Stoddart, 1984). Scat surveys occurred from 15 July to 1
October in 1997, but were restricted to one month (15 July
to 15 August) in 1996. We patrolled two permanent road
networks with all-terrain vehicles running at low speed to
collect samples; the length of networks changed between
years because of accessibility and vegetation height, which
prevented us from detecting scats. In the rural landscape,
the network measured 43 and 54 km in 1996 and 1997
respectively whereas it covered 91 and 89 km during corresponding years in the forest landscape. At their closest
point, the two networks were 25 km apart. Both networks
were patrolled twice a month. Prior to the beginning of scat
surveys in July, we cleared up the two circuits in order to
collect only fresh scats of known age; these scats also
served for determining coyote food habits.
COYOTE FOOD HABITS
We determined food habits by identifying undigested
fragments of food items remaining in scats (Tremblay,
Crête & Huot, 1998). Owing to the variation in the recovery
of bone and teeth and the lack of variation in the recovery
of hair in small mammal remains (Kelly & Garton, 1997),
teeth and bone served only to identify prey species, and hair
fragments to estimate volume. We converted the percentage
of volume occupied by fragments of each food item in scats
(visually estimated to the nearest five percent) into food
ingested by correcting for differential digestibility according to Hewitt and Robbins (1996). Results were expressed
as percentages of food ingested on a dry basis.
AVAILABLE BIOMASS OF PREY
We measured the availability of the main food items of
coyotes in the study area (small mammals, snowshoe hare,
and fruits; Tremblay, Crête & Huot, 1998) and estimated
that of secondary prey (moose, white-tailed deer, woodchuck [Marmota monax L.], and beaver) from the literature.
We used a stratified random sampling design (Cochran,
1977) with 6 (1996) or 9 (1997) sampling grids per landscape (Figure 1) to estimate the biomass of small mammals and snowshoe hare in each landscape, but sampling
techniques differed among prey species (Richer, 2000).
Sampling units covered ª 20 ha for hare and ª1 ha for arvicoline rodents (deer mouse [Peromyscus maniculatus
Wagner], Gapper’s red-backed vole [Clethrionomys gapperi
Vigors], meadow vole [Microtus pennsylvanicus Ord.],
meadow jumping mouse [Zapus hudsonius Zimmerman],
and woodland jumping mouse [Napaeozapus insignis
Mill.]) and shrews (masked [Sorex cinereus Kerr], smoky
[S. fumeus Mill.], and short-tailed [Blarina brevicauda
Say]). We estimated the biomass of arvicoline rodents and
hare in each sampling unit using a mark-recapture approach
(Caron, 1998). We estimated shrew biomass using mini46
mum number captured. For estimating the biomass of fruits,
we used a two-stage stratified random sampling design with
7 primary units per landscape (Cochran, 1977). The animal
handling protocol received the approval of the Animal
Protection Committee of Université Laval (97-158).
ARVICOLINE RODENTS
Mice and voles were captured in Sherman and
Tomahawk livetraps baited with a piece of apple and a mixture of peanut butter and rolled oats. Traps, arranged in
10 ¥ 10 grids, were spaced at 10-m intervals and were
deployed during 4 (1996) or 3 (1997) consecutive nights.
Trapping extended from 22 July to 18 August in 1996 and
from 21 July to 29 August in 1997; we visited each grid
once a day. Captured animals were identified to species
(Piérard, 1975), sexed, aged, and weighed, and their reproductive conditions were noted. Animals were marked by toe
clipping in 1996 and by ear tagging in 1997 and released at
the point of capture.
SHREWS
In 1996, we tallied, identified, and weighed all shrews
captured in traps set for arvicoline rodents. In 1997, we
added 10 pitfall traps (3L plastic bucket) with 5-m long drift
fences in some grids where we had captured shrews during
microtine livetrapping (3 and 4 grids in rural and forest
landscape respectively; McCay et al., 1998; Richer, 2000).
Captured animals were euthanised, weighed, and kept
frozen for identification. We computed the ratio of total
shrew biomass captured in grids with livetraps and pitfalls
over that in grids with only livetraps in order to correct for
grids with lower trapping intensity in 1996 and 1997.
SNOWSHOE HARE
We used Tomahawk livetraps baited with fresh alfalfa
and a piece of apple to capture hares. Trapping grids covered 300 m ¥ 400 m, and we set traps 100 m apart. Animals
were marked with tags placed between the 2 longest toes of
both hind feet. Trapping occurred from 24 September to 11
October in 1996 and from 13 September to 16 October in
1997, during 4 (1996) or 3 (1997) consecutive nights, each
grid being visited once a day.
SECONDARY ANIMAL PREY
Available biomass of secondary prey species was
obtained using information from various sources and
approaches (Richer, 2000). Densities of moose, white-tailed
deer, and beaver were obtained from aerial surveys carried
out by the regional office of the Société de la faune et des
parcs du Québec. For woodchuck, we used density and
body mass of animals living in fields due to the absence of
data and the rarity of the species in other habitat types (Lee
& Funderburg, 1983). For moose and white-tailed deer, we
used the biomass of living fawns and of animals dying during summer since coyotes seem to feed mainly on these categories during summer (Patterson, Benjamin & Messier,
1998; Tremblay, Crête & Huot, 1998).
FRUITS
Primary units covered 225 m ¥ 90 m and were sampled with 100 secondary units (3.14-m 2 circular plots).
Secondary units were arranged systematically, spaced at
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ÉCOSCIENCE, VOL. 9 (1), 2002
Percent of diet dry matter (%)
COYOTE FOOD HABITS IN LATE SUMMER
In 1996, fruits dominated the diet of both rural
(55% ± 18) and forest coyotes (67% ± 7) (Figure 2a). In the
forest landscape, snowshoe hare (12% ± 5), moose
(8% ± 4), and other wild mammals (8% ± 4), including
muskrat (Ondatra zibethicus L.), eastern chipmunk (Tamias
striatus L.), and red squirrel (Tamiasciurus hudsonicus
Erxleben), were of secondary importance as prey species
whereas in the rural landscape, small mammals (45% ± 18)
were the only other food item detected besides fruits, given
the limited sample size. In 1997, fruits still dominated the
diet in both landscapes (Figure 2b, 46% [± 4] and 48% [± 6]
in rural and forest landscapes respectively). Other food
items included small mammals (16% ± 3), snowshoe hare
(12% ± 3), bovids (6% ± 2), and other wild mammals (5% ±
2) in the rural landscape and snowshoe hare (16% ± 3),
other wild mammals (13% ± 4), small mammals (10% ± 4),
60 a) 1996 late summer
*
40
20
0
60 b) 1997 late summer
40
20
COYOTE DENSITY
Trappers captured 50, 32, and 29 coyotes in the study
area during the 1994-95, 1995-96, and 1996-97 trapping
seasons respectively, of which 4, 8, and 3 were marked.
This yielded estimates of 171 (± 56), 98 (± 22), and
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STATISTICAL ANALYSES
For each landscape, we estimated the average biomass
of hares, arvicoline rodents, and fruits. In the case of animals, we first estimated the effective grid size, using half
the distance (m) separating two consecutive captures of the
same animal as a strip around each grid (Brooks, Smith &
Healy, 1998). The biomass of each animal prey captured per
grid served as the input variable to calculate an uncorrected
weighted mean density per landscape, given our stratified
random design. This biomass estimate was corrected to
account for effective grid size and for the biomass of animals that we did not capture, using a modification to the
Chao estimator (Chao, 1987; Caron, 1998). The variance of
each estimate included a component related to inter-grid
variability and another associated with the mark-recapture
technique (Caron, 1998). In the case of wildberries, we estimated for each secondary sampling unit the total biomass of
edible ripened fruits, and we estimated a weighted average
(and its variance) per landscape using formulas for twostage sampling (Cochran, 1977).
We used one-tailed tests to compare prey biomass
between landscapes because we predicted greater animal
prey density in the rural landscape. The homogeneity of
annual estimates of coyote numbers in the study area was
compared with the likelihood ratio test (Sokal & Rohlf,
1981). We compared the relative density of coyotes
between landscapes using a paired t-test on scat density
(scats 100 km-day-1) along trail networks patrolled on 5
occasions during the summer of 1997. We compared snowshoe hare and small mammal body mass with t-tests whereas
z-tests served for small mammals and snowshoe hare biomass (separately or combined) and fruits comparison
(Scherrer, 1984). We used two-way ANOVA to compare
food habits among landscapes and years (SAS Institute Inc.,
1988). Means are followed by their standard error (SE).
159 (± 64) coyotes in the study area in autumn of the first,
second, and third year respectively. These three estimates
did not differ significantly (c2 = 2.05, P = 0.36). We collected 6 and 123 scats in the rural landscape in 1996 and
1997 respectively, as opposed to 32 and 55 in the forest
landscape for corresponding years. Given the inadequate
sample size in 1996 and the consistency of scat collection
in 1997 and 1995 (Tremblay, Crête & Huot, 1998), we
compared coyote density using scat density in 1997 only;
we encountered more scats (t = 3.26, P = 0.03, n = 5) in
the rural (3.28 (± 0.72) scats 100 km-day-1) than in the forest landscape (0.88 (± 0.20) scat 100 km-day-1). These
relative indices yielded a density estimate of 2.7 and
0.5 individuals 10 km-2 in the rural and the forest landscape
respectively.
Sm
10-m intervals along 10 parallel transects separated by
25 m. We sampled only species that coyotes eat and that
provided fruits between the ground and 1.5 m: Aralia nudicaulis L., Cornus canadensis L., C. stolonifera Michx,
Fragaria virginiana Duchesne, Prunus pensylvanica L. f.,
Ribes lacustre (Pers.) Poir. , R. sativum Syme, Rubus idaeus
L., R. pubescens Rafinesque Schmaltz, Sambucus pubens
Michx, Streptopus roseus Michx, Vaccinium angustifolium
Ait. In 1996, we measured the percentage of cover by plant
species in all secondary units. For all species, we also collected all ripened fruits in the first 10 secondary units of
each primary unit. Fruits were dried at 70°C until weight
stabilisation and weighed (± 0.01 g). We estimated the dry
biomass of fruit in each secondary unit with the help of a
linear regression relating percentage of cover and fruit biomass. In 1997, we collected and weighed ripened fruits in
all secondary units.
FIGURE 2. Food habits of rural (1996 n = 6 scats, 1997 n = 123 scats)
and forest (1996 n = 32 scats, 1997 n = 55 scats) coyotes in southeastern
Québec, expressed as percentage of diet dry matter, according to the year
of scat collection. a) 1996 late summer: 15 July-15 August 1996; b) 1997
late summer: 15 July-1 October 1997. Rural landscape (grey bars); forest
landscape (solid bars). An asterisk indicates a significant difference
between landscapes (two-way ANOVA, F = 10.87, P = 0.001).
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47
RICHER ET AL.: FOOD OF FOREST AND RURAL COYOTES
and moose (9% ± 4) in the forest landscape. In 1997, all
food categories, expressed as dry matter intake, had comparable importance in both landscapes (two-way ANOVA,
F = 1.34, P = 0.25). In 1996, there was a significant difference between landscapes for small mammals (F = 10.87,
P < 0.001); consumption of small mammals was higher in
the rural landscape (45%) than in the forest landscape
(0.2% ± 0.2). However, the sample size was low, especially
in the rural landscape. There was no interannual difference
when each food item was taken separately (P > 0.05).
When pooling prey as animal or vegetal food items, we
detected a significant difference between years in the forest
landscape (animal prey 1996 = 30% ± 7; 1997 = 52% ± 6;
two-way ANOVA, F = 4.48, P = 0.04). Consumption of
animal prey remained stable in the rural landscape between
both summers (1996 = 45% ± 18; 1997 = 49% ± 4;
F = 0.05; P = 0.83). There was no significant difference in
animal prey consumption between landscapes during any
year (1996: F = 0.52, P = 0.47; 1997: F = 0.14, P = 0.71).
AVAILABLE BIOMASS OF PREY
In 1996, we captured 9 and 21 different snowshoe hares
in rural and forest landscapes, respectively, whereas we captured 15 and 40 hares in the respective landscapes in 1997.
There was no difference between body mass of snowshoe
hares between years or landscapes (t-test, P > 0.05, Table I),
the overall mean body mass being 1.33 kg (± 0.04). During
both summers, in the rural landscape, all hares were captured in woodlots; none were captured in old fields and
regenerating forests (Table II). In the forest landscape, the
greatest number of hares occurred in forests dominated by
conifers; few or no hares were present in regenerating forests.
The three main species of small mammals captured
were short-tailed shrews, red-backed voles, and deer mice.
We corrected biomass of shrews captured in livetraps in
1996 by a factor of 1.4 based on the pitfall trapping done in
1997. Only the body mass of short-tailed shrews differed
significantly between landscapes in 1997 (t-test, t = 2.66,
P = 0.01, Table II). Body mass of all three other dominant
species of small mammals did not differ significantly
between years and landscapes (P > 0.05) although there was
a trend towards greater body mass in the rural landscape.
For both years, in the rural landscape, most arvicoline
rodents (mice and voles) were captured in forests, and fewer
were taken in old fields, regenerating forests, and cultivated
fields (Table III). In the forest landscape, density in coniferous and deciduous forests exceeded that measured in regenerating forests. In 1996, when densities were low relative to
1997, arvicoline rodents occupying the forest landscape
reached the highest density in deciduous stands.
The overall animal prey biomass was greater in the forest
than in the rural landscape during both summers (1996: 0.69
and 1.53 kg ha-1 in rural and forest landscapes, respectively;
1997: 1.02 and 2.17 kg ha-1 in rural and forest landscapes,
respectively), snowshoe hare and small mammals being the
most important prey species (Figure 3). In 1997, hare biomass
in the forest landscape exceeded that in the rural landscape
(1.53 ± 0.22 kg ha-1 compared to 0.40 ± 0.06 kg ha-1 in corresponding landscapes; Z = -1.69, P < 0.05; Table II). We
observed the same trend in 1996, but a statistical comparison
was impossible because we could not obtain a non-biased
estimate of density in the rural landscape due to the insufficient number of hare recaptures. Although not statistically
significant (P > 0.05), there was a ª 5-fold variation in
small mammal biomass between years (0.09 kg ha-1 ± 0.01
in both landscapes in 1996 versus 0.52 ± 14 and 0.47 ± 25 kg
ha-1 in rural and forest landscapes respectively in 1997;
Moose
White-tailed deer
Beaver
Woodchuck
Snowshoe hare
Small mammals
*
Rural
Forest
*
Rural
Forest
1997
1996
FIGURE 3. Availability of the major prey of coyotes in southeastern
Québec according to year and landscape, expressed as live biomass
(kg ha-1). An asterisk indicates a significant difference between landscapes
(one-tailed Z-test, Z = -1.69, P < 0.05).
TABLE I. Body mass (kg) of the main prey species of coyotes captured in rural and forest landscapes in southeastern Québec in 1996 and 1997.
Species
Snowshoe hare
Short-tailed shrew
Red-backed vole
Deer mouse
a
Landscape
Rural
Forest
Rural
Forest
Rural
Forest
Rural
Forest
Mean
1.44
1.22
0.0139
0.0182
0.0200
0.0181
0.0168
0.0155
1996
SE
0.11
0.06
0.0014
0.0012
0.0009
0.0007
0.0008
n
9
21
1
5
9
19
11
11
Mean
1.37
1.35
0.0213a
0.0173a
0.0203
0.0187
0.0160
0.0157
Significant difference between landscapes (t-test, P < 0.01).
48
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1997
SE
0.10
0.05
0.0009
0.0013
0.0008
0.0006
0.0005
0.0003
n
15
40
28
21
67
119
22
61
ÉCOSCIENCE, VOL. 9 (1), 2002
TABLE II. Mean biomass of snowshoe hares (kg ha-1) and fruits (dry kg ha-1), and mean density (hare ha-1) of snowshoe hares, according to
habitat type, southeastern Québec, 1996 and 1997 summers.
Landscape
Habitat type
Snowshoe hares
Biomass
Fruits
Biomass
Density
RURAL
Old fields and regenerating forests
11 to 40 years old forests
> 40 years old forests
Total landscape
1996
0
0.99
0.39
0.46
1997
0
0.43
0.71
0.40
1996
0
0.69
0.27
0.32
1997
0
0.31
0.52
0.29
1996
14.29
9.23
0.20
6.22
1997
14.65
7.80
0.01
5.83
FOREST
Regenerating forests
Forests dominated by deciduous trees
Forests dominated by conifers
Total landscape
0
0.18
2.49
1.24
1.27
0.63
3.17
1.53
0
0.15
2.04
1.02
0.94
0.47
2.35
1.13
5.46
0.04
0.94
1.69
22.00
0.04
0.71
5.30
7
*
***
TABLE III. Mean biomass (kg ha-1) and density (individuals ha-1)
of arvicoline rodents according to habitat type, southeastern
Québec, 1996 and 1997 summers.
***
*
6
Landscape Habitat type
Dry biomass (kg ha-1)
**
RURAL
5
4
FOREST
3
2
**
1
0
1996
Cultivated fields
Old fields and
regenerating forests
Forests
Total
Regenerating forests
Forests dominated
by deciduous trees
Forests dominated by
conifers
Total
Biomass
1996
1997
0.02
0.16
0.03
0.37
Density
1996
1997
0.93
9.09
1.55
20.49
0.11
0.09
0.60
0.52
6.19
4.94
33.12
28.48
0.03
0.19
0.11
0.61
1.79
11.11
6.30
33.50
0.05
0.55
3.04
30.03
0.09
0.47
5.16
25.73
TABLE IV. Relative importance (% dry biomass) of fruits susceptible to be consumed by coyotes in rural and forest landscapes of
southeastern Québec, late summer 1997.
1997
FIGURE 4. Dry biomass of fruits available to rural and forest coyotes in
southeastern Québec according to year of collection. Rural landscape
(open bars); forest landscape (solid bars). Single asterisks indicate significant differences between years in rural landscape (one-tailed Z-test,
Z = 6.37, P < 0.001); double asterisks indicate significant differences
between years in forest landscape (Z = -69.24, P < 0.001); triple asterisks
indicate significant differences between landscapes in both years (1996:
Z = 112.87, P < 0.001; 1997: Z = 7.54, P < 0.001).
Table III). Annual variation of small mammal availability
resulted in a 1.35-fold increase in overall animal prey biomass between 1996 and 1997.
Red-osier dogwood, raspberry, and dwarf cornel represented the bulk of the edible fruit species available to coyotes in 1997 in both landscapes, followed by red-berried
elder in the rural landscape and by swamp currant in the forest landscape (Table IV). During both years, in the rural
landscape, most fruits were collected in old fields and
regenerating forests, fewer in young forests, and very few in
old forests (Table II). In the forest landscape, most fruits
grew in regenerating forests. The biomass of edible fruits
remained relatively constant in the rural landscape in 1996
and 1997, but it tripled in the forest landscape during the
second year (Figure 4). It was impossible to compute an
unbiased variance estimate in 1996 due to the absence of
formulas for estimates derived from combining two-stage
stratified random sampling and estimation by regression.
Species
Aralia nudicaulis
Cornus canadensis
Cornus stolonifera
Fragaria virginiana
Prunus pensylvanica
Ribes lacustris
Ribes sativum
Rubus idaeus
Rubus pubens
Sambucus pudens
Streptopus roseus
Vaccinium angustifolium
Rural
< 0.1
7.8
69.0
2.1
0
0.2
0.2
14.4
0.2
5.2
0
0.8
Forest
0.3
2.7
65.2
1.7
< 0.1
9.7
0
20.0
< 0.1
0.1
< 0.1
0.2
Using only two-stage sampling in 1997, the statistical comparison indicated that the available biomass of fruits was
greater in the rural (5.83 ± 0.02 kg ha-1 dry weight) than in
the forest landscape (5.30 ± 0.02 kg ha -1 dry weight;
Z = 7.54, P < 0.001).
Discussion
We estimated coyote density and availability of their
main prey species in order to test our prediction of greater
access in summer to animal prey for rural than for forest
coyotes. Our density estimate for coyotes for the entire
study area was imprecise due to the limited number of animals marked and recaptured and could be biased given the
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RICHER ET AL.: FOOD OF FOREST AND RURAL COYOTES
greater vulnerability to trapping of immature coyotes
(Sacks, Blejwas & Jaeger, 1999; Crête et al., 2001) and
their propensity for dispersal (Harrison, 1992b). However,
only 2 out 24 radio-tagged coyotes dispersed from the study
area between 1994 and 1998, and our density estimate
remained within the range of those measured with other
methods in comparable landscapes (Messier, Barrette &
Huot, 1986; Samson & Crête, 1997; O’Donoghue et al.,
1997). We partitioned coyotes between landscapes using
scat density in 1997 because the sampling period was too
brief in 1996. Scat density was also much lower in the forest than in the rural landscape during the 1995 summer
(Tremblay, Crête & Huot, 1998) whereas territory size covered larger areas in the forest (111 km2) than in the rural (48
km2) landscape between 1994 and 1998 (Crête et al., 2001).
We conclude that coyote density in the rural landscape
exceeded that in the forest landscape even if anthropogenic
mortality factors tended to attenuate this difference (Crête et
al., 2001).
During both summers, coyotes fed mainly on wildberries, small mammals, and snowshoe hare. Forest coyotes
were more frugivorous in 1996 and consumed comparable
amounts of animal and vegetal food in 1997, during an
irruption of deer mice (Bowman, Forbes & Dilworth, 2001;
Figure 3). Our study was plagued by constraints imposed by
the costs of field surveys. We had to use a case-study
approach without replication for landscapes and to limit the
annual sample size to 6-9 grids per landscape for the main
prey. Hence, our estimates of prey availability were imprecise, yet we clearly detected the irruption of deer mice also
noticed in adjacent northern New Brunswick (Bowman,
Forbes & Dilworth, 2001).We correctly identified the major
prey species of coyotes and estimated their biomass directly
in the field. Clearly, the results do not support our prediction since the availability of animal food was greater in the
forest than in the rural landscape (Figure 3).
COYOTE FOOD HABITS
Tremblay, Crête and Huot, (1998) also found that wildberries, small mammals, and snowshoe hares were the main
food types consumed by coyotes during the second half of
the summer in southeastern Québec. Fruits were the staple
food of coyotes inhabiting more boreal habitats on the
Gaspé peninsula in August (Samson & Crête, 1997) whereas hare was the main food of those living further south in
Québec (Messier, Barrette & Huot, 1986).
In 1995, coyotes of our study area consumed mainly
small mammals in the rural landscape and wildberries in the
forest landscape (Tremblay, Crête & Huot, 1998). During
the summer of 1996, forest coyotes still concentrated their
feeding on wildberries, but for the food items consumed by
rural ones were imprecise due to inadequate sample size (6
scats). In 1997, both rural and forest coyotes made high use
of fruits although forest coyotes consumed less fruit and
more animal food as compared to 1996. In short, forest coyotes consumed high amounts of wildberries three years in a
row, reducing their fruit consumption in 1997, whereas
rural ones changed their food habits, the relative importance
of small mammals and wildberries reversing in 1997 compared to 1995. The diminishing use of wildberries by forest
coyotes between 1996 and 1997 is likely the consequence of
50
an increased density of deer mice and snowshoe hare in
1997 (Tables II and III; Bowman, Forbes & Dilworth,
2001). It is more difficult to explain the higher use of small
mammals by rural coyotes in 1995 than in 1997 since we
have no information about prey densities for the former
year. Rural coyotes could have used more plant food in
1997 in response to a higher fruit production in 1997 than
in 1995 since we know that fruits were abundant in the rural
landscape in 1996 and 1997 (Table II). Our results illustrate
the variability that characterises the foraging behaviour of
coyotes and also the limitations of scat analysis for studying
foraging ecology of carnivores, at best providing information on the relative importance of food items, but no information on absolute food intake. Unlike Tremblay, Crête and
Huot (1998), we corrected the percentages of volume to
take into account the variable digestibility of food items.
This modification did not, however, change general trends.
The high use of berries that we documented in 1997,
i.e., 46% and 48% (percentage of food intake) of diet for
rural and forest coyotes, respectively, is not unusual at the
northeast fringe of the coyote range. In the same study area in
1995, Tremblay, Crête and Huot (1998) obtained comparable results, with fruits making up 25% and 43% (percentage
of volume) of diet for rural and forest coyotes, respectively.
Further to the north, berries represented 55% and 80% of
the volume of coyote scats in boreal forests of the Gaspé
peninsula in 1988 and 1991, respectively (Samson & Crête,
1997) whereas further south, in mixed hardwood-coniferous
forests, berry volume was only 14% (Messier, Barrette &
Huot, 1986). Elsewhere in North America, fruit consumption by coyotes remains generally low, at less than 1% of
scat volume (reviewed by Samson & Crête, 1997) although
occurrence in scats may substantially increase when blueberries become locally abundant (Harrison & Harrison,
1984). A low productivity in animal prey or a low vulnerability of prey to coyote predation could explain the high use
of fruits in southeastern Québec.
PREY AVAILABILITY
Densities of snowshoe hares that we measured in the
rural landscape were comparable to those observed during
lows of cyclic populations in western Canada (Keith &
Windberg, 1978; Krebs et al., 1986) and to the lowest population estimates in Maine and Nova Scotia (Litvaitis, 1984;
Patterson, Benjamin & Messier, 1998). In the forest landscape, our hare densities exceeded those obtained in Maine
and Nova Scotia but were in the range of hare densities in
western Canada (Todd, Keith & Fisher, 1981) and
Wisconsin (Keith, Bloomer & Willebrand, 1993). Cyclic
populations in western Canada reach, however, much
greater densities when at cycle peak (Keith & Windberg,
1978; Todd, Keith & Fisher, 1981; Litvaitis, 1984; Krebs et
al., 1986; Keith, Bloomer & Willebrand, 1993; Boutin et
al., 1995; Patterson, Benjamin & Messier, 1998;
O’Donoghue et al., 1998). Hare density seems to exhibit
more fluctuations in northwestern North America than in
the northeast; this pattern might be related to climatic oscillations (Stenseth et al., 1999). Within our study area, the
greater hare densities in forests compared to the rural landscape likely came from snowshoe hares’ requirement for
dense cover (Ferron & Ouellet, 1992; Keith, Bloomer &
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ÉCOSCIENCE, VOL. 9 (1), 2002
Willebrand, 1993; Cox, Garrott & Cary, 1997; Beaudoin,
2001.).
Small mammal densities increased 5-fold in 1997 compared to 1996, with the increase occurring in all habitat
types (Table III) and in both landscapes; this suggests a
response to a factor operating at a regional scale, e.g., climate. Bowman, Forbes and Dilworth (2001) also observed
an increase of the same magnitude in deer mice in 1997 in
New Brunswick and speculated that exceptional mast production allowed reproduction during the previous winter. In
general, our higher population estimates are comparable to
small mammal densities observed in forests of Canada but
lower than estimates made in forests of northern Europe or
in old fields of the United States (Martell & Radvanyi,
1977; Anthony, Niles & Spring, 1981; Wegner & Merriam,
1990; Boutin et al., 1995; Jedrzejewski, Jedrzejewska &
Szymura, 1995; Jedrzejewski & Jedrzejewka, 1996; Nupp
& Swihart, 1996; Brooks, Smith & Healy, 1998;
O’Donoghue et al., 1997, 1998; Sullivan et al., 1998a,b).
Overall, densities of coyotes’ animal prey in southeastern
Québec seem comparable to those of other areas in northern
North America but are likely lower than those estimated for
open habitats in areas further south (Harrison, 1992a;
Parker, 1995).We expected to observe a greater availability
of animal prey for coyotes in a rural landscape because the
high productivity of ground vegetation in cultivated and
abandoned fields should produce high densities of small
mammals (Jedrzejewski & Jedrzejewska, 1996). The reverse
occurred in both landscapes: open habitats in the forest
(recent cuts: 652 kg per coyote) and in the rural landscape
(cultivated and abandoned fields: 25 kg per coyote) provided less prey than did closed habitats in the forest (3,523 kg
per coyote) and in the rural (314 kg per coyote) landscape
(Richer, 2001). This suggests that animal prey receive better
protection against predators in forested habitats than in relatively open habitats.
C ARRYING
CAPACITY FOR MEDIUM - SIZED AND SMALL
CARNIVORES
We failed to explain the lower body reserves of forest
coyotes than rural coyotes during late summer (Poulle,
Crête & Huot, 1995; Tremblay, Crête & Huot, 1998) by a
lower availability of animal food. We anticipated a direct
relationship between the presence of prey and their availability for coyotes, with similar vulnerability across habitat
type and landscape. This assumption may not hold because,
obviously, prey can occupy places where predators cannot
reach them or can remain undetectable due to the vegetation
(Abrams & Walters, 1996). Since openings cover proportionally a greater area in the rural than in the forest landscape, dense vegetation could reduce hunting efficiency of
coyotes in the forest landscape. Access to farm carrion
(Todd, 1985) could also explain the better nutritional condition of rural coyotes during summer. However, we detected
only small amounts of bovid residues (6% of diet) in scats
collected in the rural landscape; this prey item was not
important for rural coyotes in 1995, either (Tremblay, Crête
& Huot, 1998).
Vegetation, as a spatial refuge, could play an important
role in stabilising medium-sized and small carnivores/prey
systems. For large herbivores, size and strength of prime
adults make them practically invulnerable to predators (e.g.,
moose versus wolf), which concentrate their predator, foraging on young and old individuals (Peterson, 1977). This
contributes to stabilising these systems since prime animals
occupy temporal refuges due to their age (Hassell & May,
1973; Durant, 1998). Prey are generally smaller than predators for medium-sized carnivores (Carbone et al., 1999) and
remain vulnerable to predation throughout their life. It is
likely, however, that habitats exist where small mammalian
prey are practically invulnerable. These habitats would act
as spatial refuges (Abrams & Walters, 1996), stabilising the
system and preventing local prey extinction. We propose
that this situation prevails for coyotes in our study area in
summer for prey occupying habitats with dense vegetation;
we currently have evidence of such refuges for snowshoe
hare (Beaudoin, 2001).
Based on scat density, coyotes in our study area were
more abundant in the rural than in the forest landscape,
which suggests a larger carrying capacity for coyotes in the
former landscape (but see Van Horne, 1983). In addition,
rural coyotes had faster growth and larger body mass than
did their forest counterparts during summer (Poulle, Crête
& Huot, 1995; Tremblay, Crête & Huot, 1998). The presence of more open habitats in the rural landscape would
explain the better performance, during summer, of coyotes
occupying it. Competition with other carnivores might also
be less in the rural landscape if coyotes can tolerate more
proximity to humans than other carnivores can.
It is difficult to test our research hypothesis through a
static approach such as ours. We took an instant snapshot at
the end of two summers, but the main prey we studied have
several litters per summer and energy transfer from one
trophic level to the other is continuous. Energy and protein
transfer from herbivores to coyotes probably was greater in
the rural than in the forest landscape, as evidenced by the
tendency for greater coyote density (shown in this study),
faster pup growth (Tremblay, Crête & Huot, 1998), and
larger human harvest (Crête et al., 2001), even in the presence of a lower prey biomass. Our results on herbivore and
carnivore biomass concur with the prediction of the exploitation ecosystems hypothesis (EEH), which supposes an
instant energy transfer from inferior to superior trophic
level (Oksanen et al., 1981). However, adequate testing of
this prediction would require biomass estimates for all flying and terrestrial carnivores, in addition to those of small
herbivores, because EEH deals with guilds, not species.
Investigating intraguild competition among carnivores
might cast some light on how energy and protein flow in
terrestrial ecosystems of northeastern North America.
Acknowledgements
We thank N. Bergeron, D. Grenier, F. Boileau, N. Soucy, and
C. Langlois for their help in the field, M. Salaté for scat analysis,
N. Caron, H. Crépeau, and G. Daigle for statistical advice, and the
Ministère des Ressources naturelles du Québec for supplying
maps. This research project was supported by the Société de la
faune et des parcs du Québec, Fonds pour la Formation des
Chercheurs et l’Aide à la Recherche, the Natural Sciences and
Engineering Research Council of Canada, Fondation de la Faune
du Québec, and Fédération québécoise de la faune. S. Larivière, D.
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51
RICHER ET AL.: FOOD OF FOREST AND RURAL COYOTES
Murray, and M. O’Donoghue kindly commented on an earlier
draft of this manuscript.
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53
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