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Ungulates have some of the longest migrations of all terrestrial
animals, up to several thousand kilometres for species such as
the North American caribou (
Rangifer
ssp.). Migration is a cru-
cial element in the survival of many ungulates, their ability to
survive in marginal landscapes being based on the opportunity
to migrate. Twenty-four large mammal species (and their sub-
species) are known to migrate in large aggregations today – all
of these are ungulates (Harris
et al.
, 2009).
Infrastructure may have an impact on wild ungulates by creat-
ing direct disturbance and road kills locally, though this effect
is usually less important compared with avoidance or blocking
of migrations. Of far greater concern is when infrastructure
generates increased traffic and human activity surrounding
these corridors leading to increased logging, hunting, poach-
ing and settlements, as well as introduction of invasive species,
livestock and agricultural expansion. This in turn, may lead to
more regional indirect impacts such as avoidance of road cor-
ridors in the range of 4–10 km, and even up to 30 km, by mi-
grating ungulates, thus generating semi-permeable corridors.
These are corridors that in theory are passable, but rarely, de-
pending on the situation at hand, are crossed in reality. The
combined actions lead to cumulative impacts, resulting in a
partial or full breakdown of the ecological network involved,
Road development and agricultural expansion