Environmental Engineering Reference
In-Depth Information
Genetic analyses may also permit prediction of the like-
lihood of hybridization taking place with other taxa in
the target or release area or region. For this reason, it
is preferable that source animals for reintroductions be
taken from wild populations and not from captive ones.
Captivity can affect adaptive behavioural traits. For
plants, it is important that seeds or
propagules
of
locally adapted
provenances
be used because many
local populations show a home-site advantage and
nonlocal genotypes may be maladapted (see Chapter
7). For plants and animals, the source population
should ideally be closely related genetically to the ori-
ginal native stock and also show ecological charac-
teristics (morphology, physiology, behaviour, habitat
preference etc.) similar to the original population or
subpopulation.
If a subspecies has become extinct in the wild and in
captivity, a substitute form may be chosen for possible
release or reintroduction. Such substitutions can actu-
ally be seen as a form of benign introduction. Selection
of a suitable substitute should focus on extant subspe-
cies and consider genetic relatedness, phenotype, eco-
logical compatibility and the conservation value of
potential candidates. For example, a local population
of ibex (
Capra ibex
) that became extinct in former
Czechoslovakia was replaced by reintroductions of
Austrian
C. ibex
and Turkish
C. hircus aegagrus
and
C.
ibex nubiana
from the Sinai desert (reviewed in Stanley-
Price 1989). The inevitable hybrid forms dropped their
kids in the middle of the winter, 3 months earlier than
pure
C. ibex
, resulting in the death of all offspring. This
case illustrates the need to assess both hybridization
risks and ecological compatibility (Seddon & Soorae
1999). In general, there is a need for information on
whether the introduction can literally be considered a
reintroduction
or whether it entails a risk of effects
like those related to unintended
invasions
by aliens.
Additional considerations concern the pool or source
from which organisms are removed. Removal of indi-
viduals for reintroduction should not endanger the
wild source population, and individuals should be
removed from a wild population only after the effects
of translocation on the donor population have been
assessed and evaluated. This is especially so when
the source population is threatened. Sometimes this
can go well, especially with territorial species where
empty territories can be taken quickly by 'superfl uous '
animals which did not have a territory (Bain & French
2009), but a species may become so threatened in the
wild that it is taken into captivity, and the loss of wild
animals may leave only captive populations. Examples
include the Arabian oryx (
Oryx leucoryx
), the Przewal-
ski horse (
Equus przewalskii
) and the sorocco dove
(
Zenaida graysoni
; Stanley - Price 1989 ). In such cases,
there is still the potential to breed species in captivity
although the results of genetic and phenotypic changes
such as genetic drift, inbreeding, domestication, in-
creased tameness and the loss of behavioural traits will
tend to preclude the chances for successful reintroduc-
tion and subsequent
in situ
conservation. Attempts of
the reintroduction of captive-bred animals into suita-
ble habitats include programmes for the black-footed
ferret (
Mustela nigripes
), the golden lion tamarin (
Leon-
topithecus rosalia
) and the red wolf (
Canis rufus
). Unfor-
tunately, the success rate of reintroduced captive-bred
individuals is highly variable and often very low (James
et al
. 1983). The process of translocation (including
catching, captivity and transport) may lead to altered
corticosterone levels and chronic stress and this can
have serious effects on the performance of translocated
animals as has been found in widely different species
like the chukar partridge
Alectoris chucar
(Teixera
et al
.
2007 ) and elephants (Pinter - Wollman
et al
. 2009 ).
A special hazard related to the reintroduction of
animals is the risk of unintentional introduction of
disease or pathogens. The guidelines of IUCN (1998)
prescribe that prospective release stock should be
subjected to a thorough veterinary screening process
before transport from the original source. There are
many examples of devastating effects of diseases intro-
duced unintentionally. The parasitic round worm
Pneu-
mostrongylus tenuis
was the likely cause of the failure
of elk (
Cervus canadensis
) to survive in the Adirondacks
(Severinghaus & Darrow 1976 ); following successful
release in the region in the early nineteenth century,
presence of the species has not been reported in the
region since 1953. Another example concerns amphib-
ians, which are declining at alarmingly fast rates
worldwide. Four hundred and thirty-fi ve species have
shown rapid declines, and nine species have become
extinct since 1980, while 113 more are possibly extinct
(Skerrat
et al
. 2007). At present amphibians are threat-
ened by the disease chytridiomycosis caused by the
fungus
Batrachochytrium dendrobatidis
(Walker
et al
.
2008). This highly lethal pathogen has been shown to
be introduced in novel habitats (e.g. the island of
Majorca) with relocated individuals that were, alas,
already infected with the fungus. A recent survey
revealed that many breeding facilities for amphi-
bians in different parts of the world are infected with
