Numerous animal species are diminishing
at a much higher rate than they should be by nature. Endangerment and
extinction of animal species around the world is a serious issue in
conservation biology, which is my current field of study. Humans have increased the endangerment and extinction of many species. According to
McCleery, Hostetler, & Oli (2014), humans have
severely threatened at least one fifth of all vertebrate species over the last
four decades. This is an important issue because all animal species are
interconnected, so when one species dies out it will affect the whole ecosystem.
Although we don’t know the entire impact of losing a certain species, it could
affect the health and wellness of people everywhere. Many plant species, and
even some animal species, are used for medical purposes. All plants, including medicinal plants, are influenced
by a variety of animal species from insects pollinating flowers to birds and
animals dispersing seeds.
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| Guam rail (left), Black-footed ferret (center), Przewalski's horse (right) |
One conservation technique used to preserve these
species is the captive breeding program. Endangered and rare species have
benefited greatly from captive breeding programs. Some species were saved from
extinction due to these breeding programs including the Guam rails,
black-footed ferrets, and Przewalski’s horses. According to the National Zoo,
captive breeding programs are designed to institute genetically healthy captive
populations that are large enough to be demographically stable and possibly
reintroduce them back into the wild. However, most captive
breeding programs are reducing the genetic integrity of many endangered and
rare species.
The genetic impacts on endangered and rare species
in captive breeding programs include negative genetic adaptations due to
captive conditions and a loss of genetic diversity.
Captive breeding programs have a stable environment providing
health care, removal of predators, and food given to the animals that they
wouldn’t have received in the wild, so if many generations are kept in
captivity, mutations can occur. This could cause the species to evolve with the
captive environment altering the species’ genotype from the wild genotype. Therefore,
reintroduction of captive species into the wild may not be possible or
successful. Many species only live in captivity due to genetic adaptations from
captive conditions and human expansion into their habitat.
On the IUCN Red List, 61 species, 31 being animal species,
are considered Extinct in the Wild, and they only exist in
captivity. For a list on all of them, click on this link.
A decline in genetic diversity is
another harmful impact of captive breeding programs. This decline is due to a high
occurrence of inbreeding because of an endangered or rare species’ small
population size. Inbreeding strengthens the selection of deleterious and
detrimental recessive alleles by increasing genomic homozygosity (Leberg
& Firmin, 2008). This decreases the genetic
diversity and causes a species to be at risk of extinction because more
individuals rely on the same set of genes. For example, a study on the wild
mallard (Anas platyrhynchos) presented
a decline in genetic diversity, specifically a decrease by 17% in heterozygosity
and 39% in allelic richness in captive populations compared to the wild
population (Čížková,
Javůrková, Champagnon, & Kreisinger, 2012). According to
Jiang et al. (2005), genetic diversity shows the evolutionary potential within
a species to evolve to new environmental changes. Therefore, the decline of
genetic diversity tends to reduce the species’ ability to adapt to these new changes,
which hinders the probability of survival.
Reintroductions of various species have been
unsuccessful in many cases due to the genetic effects of breeding in captivity.
As of today, there are only unsupported recommendations of how to implement
captive breeding programs, as many of them have contradicting results. More research needs to be done to preserve our world’s
endangered and rare species.
The following are the current guidelines by
the Association of Zoos and Aquariums (AZA) for captive breeding programs
aiming to reintroduce a species into the wild.
These guidelines may improve the genetic integrity
of captive-bred animals, however, they need to be scientifically studied for
their effectiveness. Employing a set of proven procedures in captive breeding programs should allow them to preserve the species' genetic integrity, so they can achieve their primary aim: that a reintroduced species would survive and thrive in the wild.
References:
Captive Breeding. Retrieved June 19,
2014, from http://nationalzoo.si.edu/scbi/endangeredspecies/capbreedpops/default.cfm
Čížková,
D., Javůrková, V., Champagnon, J., & Kreisinger, J. (2012). Duck’s not
dead: Does restocking with captive bred individuals affect the genetic
integrity of wild mallard (Anas platyrhynchos) population? Biological
Conservation, 152, 231–240. doi:10.1016/j.biocon.2012.04.008
Jaing, P., Lang, Q., Fang. S., Ding, P., & Chen, L. (2005) A genetic diversity comparison between captive individuals and wild individuals of Elliot's Pheasant (Syrmaticus ellioti) using mitochondrial DNA. Journal of Zhejiang University. Science. B, 6(5), 413-417. doi: 10.1631/jzus.2005.B0413
Jaing, P., Lang, Q., Fang. S., Ding, P., & Chen, L. (2005) A genetic diversity comparison between captive individuals and wild individuals of Elliot's Pheasant (Syrmaticus ellioti) using mitochondrial DNA. Journal of Zhejiang University. Science. B, 6(5), 413-417. doi: 10.1631/jzus.2005.B0413
Leberg, P. L., & Firmin, B. D.
(2008). Role of inbreeding depression and purging in captive breeding and
restoration programmes. Molecular Ecology, 17(1), 334–343.
doi:10.1111/j.1365-294X.2007.03433.x
McCleery, R.,
Hostetler, J. A., & Oli, M. K. (2014). Better off in the wild? Evaluating a
captive breeding and release program for the recovery of an endangered rodent. Biological
Conservation, 169, 198–205. doi:10.1016/j.biocon.2013.11.026
I really enjoyed reading your post Kayla because I agree that this is a very important topic that people aren't putting enough emphasis on! The problem with endangered species has become an even greater issue - birds are migrating at the wrong times, there has been an increase in the number of prey recently because of the drastic decline in predators (lions, tigers, etc) in Africa due to man-hunting, and no one is doing much about it!I also personally think that there has been a rise in the amount of squirrels in the US - every time I go out somewhere, I have encounters with so many squirrels and they NEVER seem to run away from the car, they don't even seem frightened by humans anymore! It's very strange.
ReplyDeleteBut the point of my little rant was to show that there is something going on in the environment and the food chain (which is already fragile) is going through many changes because of the rise in endangered species. I think your topic is very relevant and important and something that we should not forget.
DeleteKayla,
ReplyDeleteI feel like I learned a lot from reading your blog. For some reason, not many are considering this a big issue that needs to be looked upon. I personally think that any change in the ecosystem will eventually affect the human race. There are many things that humans are encouraged to do that we generally just ignore and I feel that the public should highlight this issue a little bit more boldly. You blog did a great job explaining the problem thoroughly and what we are supposed to do to help stop the endangerment of these precious animals. Great job!
Kayla,
ReplyDeleteA great and informative post, I agree that it is true that keeping an endangered species in a protected environment like Zoo does save them but also affects their genetic diversity. Taking them back to the outside habitat is mostly not very fruitful as they get more prone to be affected negatively. In our ecosystem everything is interrelated if one species either of animals or plants gets affected, it disturbs others that are directly or indirectly related to it through food chain or food web. This results in disturbing the balance of nature. We as human beings have definitely disturbed their habitat thus bringing them on the verge of extinction and some of them are already extinct due to our activities. However, good news is that through the media or internet, now we are more aware of the situation and trying to make the things better for them and us as well.
Kayla,
ReplyDeleteI really thoroughly enjoyed reading your post, because I think you effectively communicated both the negatives and positives associated with captive breeding programs. It is important to me that you captured the duality that exists within this issue because while all captive breeding programs start out with the good intentions of saving a particular species, they often fall short due to the problems with genetic diversity. Additionally, some of the more "successful" species reintroductions into the wild are somewhat misleading, such as the black footed ferret whose inbred genes cause a myriad of health problems. It really raises the question of, why save these species if they are going to just suffer health problems and be ill suited to the environment? It's definitely a conundrum, especially because a lot of these species are endangered due to human activity.
It’s amazing to think how much we harm our environment around us. It seems that throughout history we have placed an importance of ourselves over the surrounding environment, which has meant the destruction of natural habitats. We have greatly increased the rate that species become endangered and extinct. It’s pretty sad honestly how much we just don’t care sometimes. It seems like we will only care when we are trying to destroy the habitat of an endangered species that is protected by the law; however, by doing this we are destroying the natural habitat of other animals thus contributing to the ultimate drop in their population.
ReplyDeleteVery informative and eye opening. It’s amazing how actions can be put in place in order to save a population but still does damage because the animal does not know how to adapt. That’s really unfortunate that there has to be hindering when helping, but the animals are helped in order to not become extinct. I had no idea there were that man extinct species, both animals and plants. I believe the captive breeders have the right idea, but need to implement the idea in a better fashion in order to be more successful, such as creating an environment for the animals as similar as possible to their natural environment without the dangers of whatever was threatening them to become extinct.
ReplyDelete