ORI GIN AL PA PER
Human-disturbance and caterpillars in managed forest
fragments
Peter J. T. White • Brian J. McGill • Martin J. Lechowicz
Received: 23 December 2010 / Accepted: 16 April 2011
 Springer Science+Business Media B.V. 2011
Abstract The impact of forest-edge habitat on Lepidoptera assemblages has been well-
studied, but the impact of trailside habitat has rarely been considered. We surveyed cat-
erpillar populations in relation to recreational trails at 72 quadrats in four forest fragments
in southeastern, Quebec, Canada. We found a consistent negative relationship between
trails in the forest and both the abundance and species diversity of caterpillars within and
among forest fragments. Conversely, caterpillar presence was not related to the presence of
favorable host trees at a given quadrat. We suggest that the negative effect of trails may be
due to increased predation pressure in trailside habitat and to conditions that make trailside
habitat less preferable for oviposition. These results underscore the importance of man-
aging trails to limit the amount of intra-forest disturbance experienced in important forest
fragment remnants.
Keywords Lepidoptera  Caterpillar diversity  Forest management 
Human disturbance  Trails  Disturbed landscape
Introduction
The temperate deciduous forests of eastern North American have been subjected to
widespread habitat destruction over the past 200 years (Drushka 2003; Hannah et al. 1995).
The forest fragments that remain have high levels of edge-related effects that can have a
significant impact on many forest-dwelling assemblages (Alverson et al. 1988; Murica
1995; Wilcove 1985). Habitat destruction has been particularly widespread in the St.
Lawrence Valley of southeastern Quebec, Canada where most of the historic mixedwood
P. J. T. White (&)  M. J. Lechowicz
Department of Biology, McGill University, 1205 Docteur Penfield Avenue,
Montreal, QC H3A 1B1, Canada
e-mail: peter.white@mail.mcgill.ca
B. J. McGill
School of Biology and Ecology, University of Maine, Deering Hall Room 202,
Orono, ME 04469, USA
123
Biodivers Conserv
DOI 10.1007/s10531-011-0059-3

forests have been cleared in favor of agricultural development. The few forest fragments
that remain are critical habitat for many forest-dwelling species (Warman et al. 2004).
Since many of these remnant forest fragments are in close proximity to urban areas they
experience high volumes of human traffic on both designated and unofficial hiking trails.
Much has been made of the necessity to protect forest fragments from external threats
(such as cutting and isolation), but there has been comparatively little focus on internal
threats to forest fragments such as recreational hiking or walking trails. Trailside habitat is
distinct from forest-edge habitat because the latter marks a transition to a different habitat
type (e.g. agriculture, open field, urban area, etc.) whereas the former often does not. Trails
can facilitate soil-compaction via trampling that adversely affects root development and
the growth of trailside woody plants (Bhuju and Ohsawa 1998). For many taxa, trailside
communities differ significantly in species composition from forest interior communities,
the former often characterized by a high proportion of early-succession, disturbance-tol-
erant and invasive species (Dickens et al. 2005; Hall and Kuss 1989). Trails can also lead
to increased soil erosion, muddiness and vegetation trampling in trailside habitat (Bhuju
and Ohsawa 1998; Dale and Weaver 1994; Farrell and Marion 2001).
The few studies that have examined the impact of trailside habitat on forest-dwelling
species have often uncovered a pattern similar to what is found associated with edge
habitat. Recreational trails generally have a negative effect on small-mammal populations
(Boyle and Samson 1985; Meaney et al. 2002; Sauvajot et al. 1998)—a relationship that is
typically mirrored by small mammal populations in forest-edge habitat (Bayne and Hobson
1998; Miller and Hobbs 2000; Wolf and Batzli 2004; but see also Anderson et al. 2003).
Certain bat species are well known to prefer both forest-edge and trailside habitat over
forest-interior habitat (Krusic et al. 1996; Patriquin and Barclay 2003). Many carabid
beetles often favor heavily-trampled trailside habitat over forest-interior habitat (Grand-
champ et al. 2000; Raymond et al. 2002), a similar pattern occurring in forest-edge habitat
(Magura 2002; Magura and Tothmeresz 1997; Molna´r et al. 2001; but see also Davies and
Margules 1998). Among birds, many disturbance-tolerant species tend to favor trailside
habitat over forest-interior habitat (Miller et al. 1998) in contrast to forest-edge habitat
where the overall species diversity and abundance of the bird assemblage can be signifi-
cantly higher than the forest-interior (Best et al. 1990; Strelke and Dickson 1980).
The impact of forest-edge habitat on forest-dwelling moth populations has also been
well-examined, but little research exists on the effects of trailside habitat. Insight from
edge-effect literature on forest-dwelling moths can help inform an a priori hypothesis about
the impact of trails. For example, in boreal forest habitat, Mo¨nkko¨nen and Mutanen (2003)
found no difference in moth species richness or abundance in edge versus non-edge
(interior) habitat which may suggest that trails could have little or no impact. Conversely,
in tropical areas, Arctiidae moths have been found to be significantly more species rich in
recovering secondary forests (edge-like habitat) compared to mature forest (non edge-like
habitat) (Fiedler et al. 2007; Noske et al. 2009). Noske et al. (2009) argue that this pattern
may be because recovering forest stands tend to have more habitat niches than mature
forest stands—a feature that could certainly be applicable to trailside habitat. In temperate
regions, Summerville and Crist (2004) show that small forest fragments can have higher
than expected moth richness in cases where there is a high host plant diversity to offset the
loss of forest area. A similar pattern could be predicted for trailside habitat especially if
there is an increase in host plant richness driven by an increase in disturbance-tolerant
plants. This higher-than-expected richness typically results from a greater proportion of
matrix-dwelling moths, sometimes at the expense of the forest-dwellers (Summerville
2004). Fortin and Mauffette (2001) found better caterpillar performance (bigger pupae,
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