Przewalski's Horse and Conservation Ethics
Photo retrieved from the World Wildlife Fund, 2013
The Przewalski’s (cha-VAL-ski, apparently) Horse recently made scientific headlines as the birth of the first foal to be successfully conceived via artificial insemination occurred. In the popular LiveScience article circulating the internet, artificial insemination was stated to be difficult but doesn’t go into the details as to why it was so difficult. A little searching on the internet has cropped up suggestions from various academic sources that the difficulty in getting the Przewalski’s Horse to breed in captivity (or to successfully have viable offspring via artificial insemination) has to do with anything from behavioral causation to the severe decline in genetic diversity that occurred in the early to mid-1900’s.
It’s this decline in genetic diversity that has me intrigued.
The current Przewalski’s Horse population derives from a mere 12-13 individuals. Over the years, numerous catastrophes have set back the population’s genetic diversity; World War II took a heavy toll on captive populations while behavioral modification due to different settings took a heavy toll on future breeding populations. In their native habitat, they were decimated by hunting practices, over grazing by agricultural animals, and territory loss through human pressure (Boyd & King, 2011). Since then initial recovery efforts in the early to mid-1900’s, it has been a rocky road for this species. Successes in reintroduction were not only hampered by human presence in their natural areas, but by environmental factors such as harsh winters.
In captivity, it hasn’t been easy either. According to the Conservation Centers of Species Survival (n.d.), a better understanding of the Przewalski’s Horse’s reproductive physiology and endocrinology could lend itself towards better captive reproduction. By recent headlines, one can assume that research in these areas has led to the successful birth of a foal conceived via artificial insemination.
Yet, is it too little too late?
According to Boyd and King (2011), 60% of the unique genes that were once present in the studbook no longer exist; may I repeat, those genes do not exist for this species any longer. This phenomenon is known as the founder’s effect. The founder’s effect occurs when a new population is built off a small number of the original population, leading to the loss of genetic variety within the new population. This effect can be particularly strong in species such as the Przewalski’s Horse where the new population consists of members that all derive from severely limited stock. The loss of 60% of unique genes is no small matter when it comes to the survival of the species as whole.
Take for example, the cheetah. Around 10,000 years ago, the various cheetah species faced collapse due to climactic changes, leaving only the modern day cheetah species surviving. This extreme example of genetic bottlenecking and further population decimation through hunting, loss of habitat, and forced competition with other predatory species has led to the cheetah species as we know today sharing 99% of its genes with each individual within the species; roughly, each individual is more closely related than a pair of identical twins.
The effect of such extreme loss of genetic variation has over the years led to many issues in modern day cheetah conservation. Cheetahs suffer from low birth numbers, low sperm count, and should a disease pass through the species, almost every individual will be wiped out due to genetic similarity (Cheetah Conservation Fund, 2012). The study on cheetah genetics has spanned decades and their survival is highly reliant upon human intervention and careful breeding practices within the captive population.
So what will happen to the Przewalski’s Horse down the road? The wild populations have shown to be fragile when it comes to climatic changes; harsh winters over the years have set back reintroduction efforts and at certain sites, led to the round up and containment of wild populations during winter to try and offset the loss of mature individuals (Boyd & King, 2011). Even if a steady population is built up, as the cheetah shows, all it takes is one catastrophic change to devastate the genetic viability of a species.
With a 60% loss of unique genes, the Przewalski’s Horse is arguably more genetically similar between individuals than the original population. The difficulty in breeding this animal both by traditional means and through artificial means has in part been attributed to the lack of genetic diversity within the species. Disease is already a factor being considered when it comes to the survival of the species; because of the genetic similarity of individuals and contact with domestic horses, the spread of disease could be disastrous to the reestablished populations. Extremely close monitoring of populations by researchers is required to prevent such a disaster from occurring.
Which to me, brings up the interesting question of how far conservationists should go in saving a species. To me, it has to do highly with ethics. The conservation of species is essential to the overall biodiversity of ecosystems worldwide. Yet how far, exactly, is it appropriate to go? Animal Ecology is my designated major; I have a high interest in wildlife rehabilitation (as is my present internship), and would love to work in large scale ecosystem conservation at some point. The strongest part of me screams that we should go as far as possible in conserving species, but the more logical part of me questions the morality behind cases such as the cheetah.
No one would sit back and claim to want to see species such as the cheetah or Przewalski’s Horse go extinct. Yet, I look at how fragile these populations are and I begin to question my convictions about conservation in these specific cases. Without us, we can assume that these species would hardly be in as perilous situations as they are. Conversely, without us, these species would have disappeared decades ago. Like with many species in this world, we are directly responsible for either the salvation or destruction of that species. When it comes to such dangerously limited populations, are we doing the right thing in saving them? Going beyond the majestic vision of cheetahs stalking the Africa savannah, going beyond their magnificent spotting and expressive faces, we are left with a genetic nightmare. Wildlife rehabilitation, and many areas of conservation, is about returning to nature what we, as humans, have taken out.
But when we put a species back into nature, are we always doing the best thing? In a world where saving is easier than preventing, we have run across an area of muddy ethics. Is it always the most humane option to return a genetically fragile species to what was formerly its natural habitat? Are we really saving a species, or are we just forestalling an inevitable collapse?
The Przewalski’s Horse has some advantages over the cheetah; as of now it remains more genetically diverse than the total cheetah population and is the benefactor of improved breeding practices and genetic record keeping. Historically, it seems that the Przewalski’s Horse escaped the genetic bottlenecking that cheetahs experienced and this may give the species as a whole an edge when it comes to survival. If its population can be protected from environmental hazards, exposure to disease, and loss of habitat, then it may stand a chance to survive long term. As with other species, the impact of the Pzrewalski’s Horse on its environment and the impact of its limited genetic pool on its survival will only be told with time. While the Pzrewalski’s Horse may not end up in the same boat as the cheetah, this case of conservation in action does bring to light some troubling questions: is it truly commendable to save a species that has no genetic viability without the direct control by and intervention from humans? In the end, are we doing the truly humane thing to release a species back into the wild that has such limited genetic potential? Where do we, as conservationists and future conservationists, draw the line?
And also, from the LiveScience article:
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Boyd, L. & King, S.R.B. 2011. Equus ferus ssp. przewalskii. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. Retrieved from www.iucnredlist.org.
Cheetah Conservation Fund. (2012). Genetic diversity. Retrieved from http://www.cheetah.org/?nd=genetic_diversity
Conservation Centers for Species Survival. (n.d.). Przewalski’s horse. Retrieved from http://www.conservationcenters.org/species-conservation-priorties/przewalski’s-horse/
