Management of Exotic Species
Sometimes, the introduction of a species
to a new area has proven to be very
Often, however, these introduced
organisms have become tremendous
pests causing great damage.
Four factors are primarily responsible for
determining whether an introduced
species will become established:
1. The suitability of the new habitat.
2. The adequacy of the introductory unit.
3. The degree of escape from diseases,
parasties, and predators.
4. The competitive regime of the new
A suitable habitat and niche:
Depends partly on abiotic conditons.
Also involves biotic factors such as
appropriate vegetation and the absence or
presence of certain species.
The Hutchinsonian niche:
Many introduced species that have done well in North
and South America have taken well to agricultural
and urban conditions that were created with human
The cattle egret was
introduced from West
Adequacy of Introductory Unit
The introduced individuals must be
capable of successfully starting a
This implies that they must be healthy, of
reproductive age, and sufficient in
number to breed successfully.
Attempts to reintroduce the red wolf in areas of
North Carolina have suffered from the wolves’
inability to resist certain diseases.
Certain types of plants (“weed species”)
are well adapted to invading new habitats.
In vertebrates, it is
that the group be
able to establish
or fit into a social
A whooping crane population could not
be established at Gray’s Lake National
Wildlife Refuge in Idaho because the
young cranes had no established
social structure to join.
Often, when an organism is introduced
into a new area, it finds itself free from
Rabbits at waterhole.
Escape from Competitors
Under some circumstances, an invading species
may find itself in a situation or a niche where it has
little competition. Invading species seem to do best
when invading systems with few species. This is
probably a function of reduced competition. This
may explain why exotic species often do well on
islands, or in places like Florida that have relatively
few native species.
Mechanisms of Introduction
Some are deliberate:
c. Predators imported for control
d. Crop plants.
Some are accidental:
a. Seeds mixed with crop seeds.
b. Animals carried with plant hosts.
c. Animals carried accidentally on ships.
What is the impact?
Since urban and agricultural areas are
particularly susceptible to invasion by
exotics, human interests are often
The impact of exotics in natural systems
often depends on their ecological
distinctiveness and their potential for
competitive displacement, disease
transmission or genetic swamping.
Ecological distinctiveness – successful invaders are often
quite different in some way from native species.
This results in the absence of counteradaptation. This
can lead to a species becoming a keystone exotic, one
which can lead to an almost complete reorganization of
“Mimosa tree” – Albizia sp.
Introduced livestock have had a major effect on
plant communities in many areas:
have also played
a major role in
Olympic National Park
Dealing with Detrimental Exotics:
1. Prevent them from entering.
2. Control of spread.
3. Protection of pristine areas.
4. Local eradication.
5. Protection of individuals of critically reduced
6. General population reduction.
7. Biological control.