De-extinction of the Tasmanian Tiger

Danielle Cassista: Animal Science

Paige Crowley: Animal Science

Stephen Hynes: Environmental Science

It all began in 1859, when Thomas Austin brought 24 wild European rabbits from England to Australia to use for hunting (Cox, 2012).  By the 1920’s there were over 10 billion invasive rabbits inhabiting the continent of Australia and since then the population has only grown (Rabbit Free Australia, 2015). Cox (2012) stated that these rabbits reproduced in exponential quantities and currently inhabit 70% of southern Australia, which equates to 5.3 million square kilometers. These rabbits are destructive in nature; their burrowing ruins infrastructure and causes erosion, their eating destroys farmland and vegetation, and they are a threat to native species (Rabbit Free Australia, 2015). Attempts to fix the issue of the invasive rabbit species have not been successful thus far. The past solutions included releasing diseases, destroying the warrens that rabbits live in, and building a fence to keep them from spreading to other areas of Australia. None of these methods effectively eliminated the rabbit population to a manageable number (Cox, 2012). In addition, the natural predators in Australia saw a decline when the rabbit population was nearly eliminated by the released myxoma virus in the 1950s (Rabbit Free Australia, 2015).  The rabbits that survived the virus built immunity, and repopulated the island, but the predators never made a significant comeback (Rabbit Free Australia, 2015). Therefore, we propose that the de-extinction and reintroduction of the Tasmanian Tiger, also known as the thylacine, into Australia is necessary to help decrease the overpopulation of rabbits, which will consequently improve agriculture and vegetation, eliminate the threat to native species, and save infrastructure.

Since Thomas Austin brought rabbits to Australia, the species overpopulated and to this day are causing problems involving agriculture, infrastructures, and the native species that already inhabit the land (Cox, 2012). The plan is to reintroduce the Tasmanian tiger back to the Australian habitat to eliminate the rabbit problem. Since the tiger is extinct, there will be some obstacles to consider when reintroducing this species through de-extinction, but it is possible. De-extinction is completely feasible with the science and technology present in the world today. Ogden (2014) explains that the science to perform the act of bringing a species back to life is available in the forms of nuclear transfer cloning, genetic engineering, and back breeding.

The process of nuclear transfer cloning starts with the nucleus of the extinct (or dead) animal cell being inserted into an unfertilized egg cell, and then this egg cell is placed into a surrogate mother (Ogden, 2014). This process was used on the first animal successfully cloned from the cell of a dead ewe, Dolly the sheep (Ogden, 2014). Nuclear transfer using an udder cell of a frozen, preserved ewe, cloned Dolly and she successfully lived for almost seven years (Ogden, 2014). Eventually, Dolly succumbed to lung problems and died, which is a common problem in animals cloned by nuclear transfer (Ogden, 2014). For this reason, we will not focus on nuclear cloning as a de-extinction method.

A second method that can be used to bring a species back to life is genetic engineering. Ogden (2014) explains that this process is when an incomplete genome is used, potentially retrieved from a well-preserved but extinct specimen, and at areas where there are gaps in the genome, the DNA of a close living relative is inserted to fill them. The gaps in old DNA occur because over time, the DNA breaks down and can go through chemical changes that alter and degrade the original DNA (Edwards, 2015). This method is costly, time consuming, and difficult since there are billions of base pairs to sequence in each genome (Ogden, 2014). Therefore, genetic engineering is an unrealistic way to bring back the Tasmanian tiger.

Edwards (2015) believes that in order for de-extinction to work it “[makes] sense to start with modern DNA and add in the elements needed to reproduce the ancient species” (p. 32) as opposed to trying to figure out the entire genomic sequence and clone the species from pieced together DNA. So while nuclear transfer cloning and genetic engineering are available and possible, the most feasible method involving the de-extinction of the Tasmanian tiger is back breeding. Back breeding is when scientists determine the closest living relative of the extinct animal, select the most desirable traits that resemble the extinct animal, and breed successive generations until they have the appearance of that animal (Ogden, 2014). With the Tasmanian tiger, this would be accomplished by back breeding it with the Tasmanian devil, the only living relative of the thylacine (The Tasmanian Tiger, 2015). The downside to this method is that it is time consuming, but it is the best and safest chance of bringing back healthy, functioning Tasmanian tigers to Australia. Once back breeding produces a Tasmanian tiger that very closely resembles the extinct tiger, our intention is to introduce the tiger back into the habitat it once lived in. Our plan is to enforce this de-extinction method since it is something researchers have yet to try. We believe this will eradicate the rabbit problem once and for all.

When determining the ability of the species to survive in an ecosystem, it is important to calculate human presence and developments around this ecosystem to result in better survival (Seddon et al., 2014). In addition to the consideration of human presence in the ecosystem, a major factor to consider when deciding on which species to resurrect is climate change, because the climate is different now from what it was when the species was still at large (Seddon et al., 2014). The Tasmanian tiger not being extinct for long, likely would survive with no issues. In fact, the last Tasmanian tiger died in captivity at the Hobart Zoo in Tasmania (The Tasmanian Tiger, 2015), so there should be no issues of them surviving in the wild since their main predator was humans by hunting.

The rabbits in Australia quickly caused major deterioration of the land and vegetation. Before rabbits, Australian land perfectly provided for the livestock, but with the invasion of the rabbits there was not enough pasture for them both (Rabbit Free Australia, 2015). This is causing farmers to lose livestock and also causing a decrease in weight gains for livestock (Cox, 2012). Just between seven to ten rabbits can eat as much as one adult sheep, and this is a problem because the rabbits inhabit the same areas as the livestock (Cox, 2012). What is detrimental about this is that “during drought periods, rabbits can totally strip a landscape bare leaving no food for sheep, cattle or native animals” (Rabbit Problems, 2015, para. 6) and the Australian farmers take a hit on their livestock resources. Not only do the livestock have competition, the soil also has a tough recovery from rabbit destruction (Cox, 2012). The “loss of vegetation leads to soil erosion as the exposed soil is washed or blown away” (Rabbit Problems, 2015, para. 4) and with the loss of all the nutrients, it is difficult for plants to re-grow in their place. Additionally, the nutrients from the soil are being deposited in waterways and ruining the nutrient balance in the aquatic ecosystems as well (Rabbit Problems, 2015). With the rabbits gone, the continent will slowly regain the ability to improve the agriculture, re-grow the lost vegetation, and support the native animals.

Since the rabbits arrived in Australia they competed with native species for resources (Rabbit Free Australia, 2015). They greatly outnumber every other species currently inhabiting the area and therefore make it extremely difficult for others to obtain food and find shelter (Rabbit Free Australia, 2015). Australia lost a total of 22 species, more than any other nation, due to the destruction of rabbits (Rabbit Free Australia, 2015). In the mid 2000’s, “17 bird species, 13 mammal species, 4 reptile species, 1 fish species and 1 insect species that are considered to be vulnerable, endangered or critically endangered native species were threatened by rabbits” (Rabbit Free Australia, 2015, para. 2). The only way to save all 36 of these species is to eliminate the rabbit population once and for all and the Tasmanian tiger will be the savior for all of these native species. There are currently some predators inhabiting Australia including foxes and feral cats (Rabbit Free Australia, 2015), however their diets are focused on the native species rather than the rabbits, therefore decreasing those numbers more and more. The rabbits being so high in numbers will be a good, strong food source for the tigers.

Rabbits are burrowing animals that cause erosion, deplete foundations, and ruin infrastructures of buildings (Hunter et al., 2008). Rabbits tend to take over the burrows of native animals and turn them into their warrens, or underground tunnel systems (Hunter et al., 2008). This displaces the native creatures that were in these places and requires them to dig new burrows for themselves, leading to more tunneled earth. Hunter et al. (2008) explains that when rabbits inhabit a new area they make a harbor, a temporary warren, which sometimes is under a building. This can cause extremely expensive infrastructure problems, including the cracking and collapsing of infrastructures. If this occurs in more urban settings around taller buildings, the damages can be much more significant and much more costly to fix. Rabbits are known to dig under gravesites and that causes difficult issues for Australians to deal with (Hunter et al., 2008). These structural damages would no longer be obstacles with the decline of the rabbit population due to the Tasmanian tiger.

When bringing back a species it is important to ensure that it does not go extinct again. In general, the authors found that “extinction rates cannot exceed diversification rates” (De Vos et al., 2015) and this should also be considered. This involves incorporating them into an environment that they can thrive in. The Tasmanian tiger returning to it’s own domain before extinction ensures that it can survive when reintroduced. The problem that caused the tigers to become extinct before was from overhunting by humans (The Tasmanian Tiger, 2015), so nothing that was naturally in the environment caused the tigers to die off. It should now be known that the Tasmanian tiger was not harmful to humans and avoided any contact with them (The Tasmanian Tiger, 2015). If the tigers were captured, they generally gave up without a struggle and died from shock (The Tasmanian Tiger, 2015), showing that they really are not of harm to humans. If hunting restrictions are put in place and simple conservation methods are used to protect them from humans, becoming extinct again most likely will not be an issue.

Bringing back the Tasmanian tiger will in fact be a costly process, but the current damage and methods of control are already costing Australia a lot of money (Zuckerman, 2009). Current control methods like diseases such as myxomatosis and rabbit hemorrhagic disease helped to decrease the rabbit population (Zuckerman, 2009) however it is a costly process. It costs primary production around $113 million a year in losses of production (Rabbit Free Australia, 2015). Some of the rabbits grew resistant strains to these diseases and therefore will continue to reproduce unaffected (Zuckerman, 2009). These productions will continue to increase if we do not solve this problem. In addition to these diseases, calicivirus has proved to be very useful in the eradication process, but the research to develop it costs more than $20 million (Zuckerman, 2009).

The Tasmanian tiger is the best option for eradicating the rabbits in Australia. To bring the tiger back, de-extinction through back breeding is the most feasible method. To eliminate the entire rabbit population rapidly could cause extreme ecosystem imbalance. Even though the rabbits are invasive, it may have been long enough that if they were suddenly absent from the system, there would be a detrimental drastic change. This is why we propose introducing the Tasmanian tiger to control the rabbit population instead. The tiger preferred to eat “kangaroos and other marsupials, small rodents and birds” (The Tasmanian Tiger, 2015, para. 14) that will likely include rabbits. The rabbits fit the profile of the tiger diet and their abundance makes them a viable food option. Both creatures are known to be nocturnal, so the crossing of paths most likely will happen for the rabbits to be prey of the tiger (The Tasmanian Tiger, 2015). The Tasmanian tiger will have better ability to survive this time around. The main reason for their extinction was “mainly due to direct human persecution” (The Tasmanian Tiger, 2015, para. 16) which is now very much avoidable. Restrictions can be put on the hunting, the ultimate downfall of the tiger, and monitoring the species will help to ensure survival and prevent a second extinction. The Tasmanian tiger making a return to Australia is a feasible feat and it will greatly improve the current problem associated with the rabbits.

References

Cox, T. (2012). Rabbit biology. Retrieved from http://www.dpi.nsw.gov.au/agriculture/pests-weeds/vertebrate-pests/pest-animals-in-nsw/rabbit-biology

De Vos, J. M., Joppa, L. N., Gittleman, J. L., Stephens, P. R., & Pimm, S. L. (2015). Estimating the normal background rate of species extinction. Conservation Biology, 29(2), 452–462. doi: 10.1111/cobi.12380

Edwards, Chris. (2015). Recipe for de-extinction. Engineering & Technology, 10(5), 30-33. Retrieved from Academic Search Premier.

Hunter, C., Johnson, K., and Osmond, R. (2008). Rabbit control in Queensland. 1-54. Retrieved from https://www.daf.qld.gov.au/__data/assets/pdf_file/0011/55964/IPA-Rabbit-Control-In-Queensland.pdf

Ogden, L. (2014). Extinction is forever… or is it? Bioscience, 64(6), 469-475. Retrieved from Academic Search Premier.

Rabbit free Australia. (2015). Retrieved from http://www.rabbitfreeaustralia.org.au/rabbit_problem.html

Rabbit problems in Australia. (2015). Retrieved from http://www.animalcontrol.com.au/rabbit.htm3

Seddon, P. J., Griffiths, C. J., Soorae, P. S., & Armstrong, D. P. (2014). Reversing defaunation: Restoring species in a changing world. Science, 345(6195), 406-412. doi: 10.1126/science.1251818

The Tasmanian Tiger. (2015). Retrieved from http://www.australia.gov.au/about-australia/australian-story/tasmanian-tiger

Zukerman, W. (2009). Australia’s battle with the bunny. ABC Science. Retrieved from http://www.abc.net.au/science/articles/2009/04/08/2538860.htm