Environmental Engineering Reference
In-Depth Information
species had declined to only four known wild birds,
including one breeding pair, as a result of habitat loss
and pesticide contamination. A conservation project
begun in 1973 has used many management techniques
including captive breeding, supplemental feeding of
wild birds, provision of nestboxes, multiple clutching,
egg pulling, artificial incubation, hand rearing and
release of captive-bred and captive-reared birds by
hacking, fostering and predator control. A total of
331 kestrels were released in the 10 years up to the
end of the 1993 - 4 breeding season; one-third of these
were captive bred and the rest were derived from eggs
harvested from the wild. By the 1993 - 4 season, an
estimated 56 - 68 pairs had established territories in
the wild with a postbreeding population, including
floating birds and independent young, of 222- 86.
Since the pesticides responsible for their decline are
no longer used, the number of Mauritius kestrels
should continue to rise through natural recruitment.
The distribution of suitable habitat suggests that an
eventual population of 500-600 kestrels on Mauritius
is possible. Due to its outstanding success, the release
programme for the Mauritius kestrel ended after the
1993-4 breeding season (Jones
et al.
1995).
a 10-ha pre-release enclosure. Social organization
was established peacefully, and the oryx adjusted to
the new climate and natural foods. In July 1987, the
oryx were released from the enclosure into the total-
protection zone of the park. This zone is a 2400-ha
area that has been protected from domestic livestock
since 1977 (Bertram 1988).
Sometimes a more spectacular technique is indeed
the only solution. In a translocation project for
beaver (
Castor canadensis
) in Idaho, the mountains,
heavy forests and lack of roads in Idaho made trans-
planting a labour-intensive, expensive and time-
consuming task. In addition, it resulted in high
beaver mortality. The use of planes and parachutes
with animal holding boxes proved to be a much
more efficient and much less expensive method of
transportation. In 1948, 76 live beavers were dropped
with only one casualty. Observations made in 1949
showed that the beavers that had participated in the
airborne transplantation had settled and were well on
their way to producing colonies (Heter 1950).
7.6 Socio-economic aspects and
concerns
7.5.4 Mammals
The California population of sea otter (
E. lutris
), in
the 1970s introduced from Amchitka, Alaska, is con-
sidered vulnerable and therefore a Fish and Wildlife
Service Recovery Plan for the sea otter has been
made which calls for the establishment of a second
California population as a hedge against devastation
by a possible oil spill. During the 1970s transplant opera-
tions, 86 animals were captured, 24 of which died in
the nets or holding pens. Of the 79 otters caught in
1971, 15 died due to capture complications (Mate 1972).
Also the second translocation was not without its prob-
lems, including emotional reactions of various groups
with widely different interests (Booth 1988). This
example demonstrates that re-introductions can be
highly controversial, especially with species that com-
bine a high cuddling status with potential negative
interaction with economic interests. The European
habitats directive 92/43/EEC demands a proper con-
sultation of the public in case of re-introduction of
species listed in Annex IV of the directives (EC 1992a).
Re-introductions are generally long-term projects that
require the commitment of long-term financial and
Mammals can be taken from wild source populations
or from captive breeding stock. Catching animals
from the wild can be a costly and time-consuming
operation, and is not without risk. Like birds, also
mammals should be given the opportunity to acquire
the necessary information to enable survival in the
wild, and soft releases are therefore recommended.
Mammals propagated in an enclosure tend to develop
an affinity for their immediate surroundings and
therefore, upon release, exhibit a slow dispersal rate.
This behaviour generally enhances survival. An ex-
ample of a successful soft release is the case of the
scimitar-horned oryx (
Oryx dammah
) in Tunisia
which disappeared from that country in 1902 due to
desertification, competition with domestic livestock,
disturbance and hunting. Ten young scimitar-horned
oryx (five males, five females) from Britain were re-
introduced into the Bou-Hedma National Park in
Tunisia in December 1985. They were acclimatized in
a 600-m
2
pen for 4.5 months and then released into
