Primack: Chapters 13 and 14
Discussion reading: The next discussion reading (25th Oct) is a case study of an
attempt to translocate a rare species.
The attempt failed, and the species is possible now extinct. Think especially about why this attempt might
have failed, and what could have been done differently. Also, think about when
it might make sense to do a translocation, and when it might not. Groombridge et al. 2003.
An attempt to recover the Po’ouli by
translocation and an appraisal of recovery strategy for bird species of extreme
rarity. Biological Conservation.
1. Introduction
A)
Definitions
i)
In situ
conservation means that the conservation activities occur where the species
naturally occurs in the wild.
ii)
Ex situ conservation
means that actions are taking place that involve removing the species from its
natural setting.
B)
When is ex situ conservation used?
i)
Ex situ
conservation is usually used as a last resort, when a population has become so
small or so endangered that extinction is considered inevitable without extreme
intervention. E.g., California condor.
ii)
Sometimes ex situ
conservation is the only choice, because a species no longer exists in the
wild. E.g., Père
David’s deer – see the text book.
2. Where does ex situ
conservation occur?
A)
Zoos, wildlife parks, private collections, Aquariums, etc.
i)
Over 7,000
vertebrate species are kept in zoos worldwide.
A number of endangered invertebrates (e.g., Pacific island snails) are
also kept in captivity. For the most
part, however, the species represented in zoos are a biased subset of all
species, typically emphasizing species that are big and flashy.
ii)
Zoos are
relatively good places for maintaining species in captivity and for captive
breeding programs, because they already have large facilities geared towards
keeping a wide variety of species and a trained staff with husbandry skills
geared towards exotic species. Since
zoos have an economic function they are also in a good position to take
advantage of captive breeding programs and use them to generate some of the
money that keeps the program going.
iii)
Probably the
major conservation function that zoos play is captive breeding. Many techniques are used in captive breeding,
often species-specific. In most cases, however,
these methods are geared towards the simple goal of increasing reproductive
output and the survival of offspring. A
few examples include:
iv)
Example: The guar is an endangered wild ox from Asia. Researchers have used the species to develop
and experiment with many of the techniques described. In 2001, the first cloned guar was born. This individual was implanted into a
surrogate mother of a different species (a cow).
v)
Example: The whooping crane is an endangered bird that breeds
in Canada and winters in Texas. Less
than 200 are left in the wild, but there is also a growing captive population. Double-clutching can be done, but raising the
young can be difficult without their parents.
Initially a different species (sandhill crane)
was used to incubate and raise the young.
But the baby whooping cranes imprinted on their surrogate parents and
some subsequently preferentially mated with sandhill
cranes. When humans raise the young,
imprinting is also a problem, so people have to dress up like adult whooping
cranes whenever they interact with the young birds to prevent them from getting
too mixed-up.
B)
Improving husbandry
i)
Some species do
not survive or breed well in captivity.
Consequently, new husbandry techniques constantly need to be developed
for these problematic species.
ii)
Different
facilities vary greatly in their quality. Consequently, there is a lot of
variation in how well species do in different settings. Some places, like the San Diego Zoo, have
made the breeding of endangered species a major part of their mission and have
devoted considerable resources to captive breeding programs. But not all facilities have such a strong
commitment or the resources to follow through.
iii)
There is also
variation in the needs of different species and although there is a lot of
“institutional knowledge” (i.e., the knowledge of individual practitioners),
there are relatively few detailed studies that attempt to understand how
captivity affects particular species.
iv)
In a high profile
study published in 2003, researchers showed that species with large home ranges
in nature (e.g., polar bears) tended to do worse in captivity (i.e., they had
higher infant-mortality rates, and were more prone to show repetitive behaviors
associated with stress, such as constant pacing). One upshot from this study was the suggestion
of ways to improve the zoo environment for susceptible species.
C) Botanical gardens, arboretums, etc.
i)
Many plants can
be kept in captivity too. Botanical
gardens and arboretums are the main type of location, but lots of plants are
grown in gardens, in private collections, etc.
We even have some critically endangered species (<100 individuals in
the wild) growing right here on campus in the EEB greenhouses.
ii)
Worldwide about
80,000 plant species are grown in botanical gardens. This is about 30% of the World’s plants. Kew Gardens (just outside London) alone has
about 25,000 species, about 10% of which are globally threatened.
iii)
Often it is
easier to maintain plants away from their natural settings than it is for
animals. This is because they don’t go
anywhere, they don’t need much space (usually), and they often require fairly
similar growing conditions (dirt). Most
plants also lack the complex behaviors that many animals have, making it much
easier to keep them alive and breeding.
D)
Seed banks
i)
Just as
technology is changing the way zoos function, with increasing attention to
cryogenics, there are parallel changes in plant conservation and breeding. In particular, there is an increasing focus
on developing seed banks – places where the seeds (and sometimes also pollen,
tissue cultures, etc.) can be stored over the long term.
ii)
For a long time
seed banks have existed, but primarily as a repository for storing seeds of
commercially important species. Now
there is a shift to expanding their function, especially for endangered species.
iii)
In seed banks,
the seeds are kept in cold, dark conditions, which slows down metabolism and
prevents the seeds from germinating. In
this state, they can be preserved for many years (even decades) as a back-up in
case species disappear in the wild.
iv)
Currently about
10,000-20,000 of the world’s plants are represented in seed banks. Some seed
banks (e.g., the one at Kew) have a goal of obtaining not only a high
representation of the world’s plants but also good geographic (and therefore
genetic) representation for each species.
v)
Because seeds are
small and don’t do anything, they take up very little space and require simple
maintenance at relatively low cost.
vi)
On the other
hand, seeds do not last forever and so, periodically, seeds have to be
germinated to form plants that can produce new seeds. Seed banks are also vulnerable to breaks in
the power supply that keep the refrigerators running. Another disadvantage is that there are some
seeds that simply don’t produce plants that can be stored in this way. Just as with zoos, seed banks will not work
as a repository for all species.
3. Captive breeding
in practice
A)
Problems
i)
Captive
breeding programs are expensive. For example, it is estimated that it is fifty
times more expensive to protect elephants and rhinos in zoos than in the wild.
ii)
They are also
inefficient. Conservation work proceeds one species at a
time in a captive setting, and it fails to do anything to protect functioning
ecosystems. Consequently, it is really
only useful as an absolute last resort and can never realistically be applied
to more than a tiny proportion of all species on Earth.
iii)
Limited
capacity. Captive settings (especially zoos,
arboretums, and other settings that deal with big organisms) usually cannot
maintain very big populations – hence all the problems associated with small
populations in the wild exist in captive settings. Genetic problems are especially relevant in
captive settings and much of the work that has been done on conservation
genetics has been done in conjunction with zoo populations.
iv)
Populations
are concentrated. Another problem also parallels what happens
in nature – individuals become concentrated into a small area. This is akin to
having a narrow range and is a problem for the same reasons.
v)
Adaptation to
artificial conditions. Taking species out of their natural setting
can have serious problems because species sometimes adapt (i.e., they evolve)
to their captive conditions. This is
because there is selection for individuals that do well in captivity, but it
has the consequence that certain characteristics of the species are lost. The characteristics that are selected for are
often not those that will be most important in the wild (e.g., you might select
for individuals that are not afraid of people – which might create a population
that is especially vulnerable to persecution if they are ever released back
into the wild).
vi)
Behavior. Some individuals also fail to learn key behaviors
needed to survive in the wild. Or learn
behaviors that are harmful in the wild.
Again these can be huge problems if captive breeding is being done with
the idea that individuals will be released back into nature. E.g., this has been a concern in the condor
release program where several released condors have learned to hang out around
people, beg for food, etc. Several of
these “nuisance” birds have had to be brought back into captivity; others have
died as a result of their interactions with people.
vii)
Logistic
concerns. Finally, there are logistic problems. Captive breeding programs require a long-term
commitment because you can’t just decide that you want to stop doing them for a
few years once they are in progress.
Also, when breeding is successful there can be so much production that
facilities cannot cope with the number of animals. If there are no release programs to use the
“excess” individuals there are ethical issues about what should be done with
them.
B)
Does it work?
i)
Ultimately, the
biggest question is: Does ex situ conservation work? In some cases the answer is clearly yes.
Although there are other cases when things do not go so well.
ii)
The Mauritius
kestrel provides an example of how ex situ conservation and captive breeding
can save a species from extinction. These
small falcons were down to only 4 individuals in 1974 (due to habitat losses
and the effects of pesticides such as DDT).
A captive breeding program was initiated with birds being bred in
Britain and the US. By 1996, the
population had increased so that there were about 100 breeding pairs in the
wild and a total population of about 400.
In 2000, the IUCN decided that the species was doing well enough that it
did not need to be classified as Endangered any more (though it is still
considered Vulnerable because the population is still small and restricted to a
tiny range).
4. Release programs
A)
Three types of release
i)
Reintroductions. These involve
the release of individuals into an area from which the species has been
extirpated. The release of gray wolves
into Yellowstone described in the text book is an example of an extremely
successful reintroduction.
ii)
Augmentation. Sometimes a
species persists in the wild, but is precariously close to going extinct. In these situations, captive-bred individuals
might be released into the population to increase the population size or
increase genetic diversity in the population.
Examples include the whooping crane release program and the Florida
panther example given in a previous lecture.
iii)
Introduction
program. In some cases it is not possible to release
individuals into their native range, or it is desirable to move individuals
away from their native range to a new site (this is called a translocation). Can you think of reasons why this might be
desirable?
B)What
makes a release program work?
i)
Removal of the
threat. Seems pretty obvious, but often this is hard
to do. If you don’t remove the threat though, the chances of success are
limited.
ii)
“Soft” release. Various
things can be done to make it easier for released individuals to survive,
especially in the period immediately after release. These include: providing supplemental food,
providing shelter where animals can rest, putting up pre-release cages for the
animals to live in for a period prior to release, timing the release to occur
at a time of year when conditions are good, ensuring that some of the released
individuals have experience living in the wild, providing behavioral training
(e.g., to be afraid of predators) for individuals prior to their release, etc.,
etc.
iii)
Population
size.
Release programs are more likely to be successful if a large number of
individuals (<100) are released, or if additional individuals are
periodically added to the population. Releases at multiple sites also increase
the long term persistence of the population.
iv)
Correct
genetic stock. Ensuring that released individuals are as
genetically similar as possible to the historic population is important. These individuals are generally most likely
to have appropriate adaptations for the environment into which the release
occurs.
v)
Release in
core of original range. Studies have shown that release programs are
more successful when they release individuals into the core of the species’
historic range than when the release occurs near the periphery of the historic
range. Why do you think this is?
vi)
Post-release
monitoring. Monitoring the population after the release
is important, not just because it tells you whether the release worked, but
also because it can guide you as to whether you need to release more
individuals (e.g., to help the population overcome stochastic events such as
inbreeding or sex ratio imbalance), or alternatively whether you should not
release any more (e.g., if the threat is still present and all released individuals
just die).
vii)
Public
education. Release programs are expensive and
consequently need to be well justified through effective public education
programs. In some cases the education is
critically important if the program is to exceed. For example when pink pigeons were first
released back into Mauritius many of the released birds were killed for
food. No one knew what they were, or
that there was a good reason for leaving them alone.