Applied Cryptozoology – Using Leeches to Locate the Thylacine

Authors: Michael Weinzierl ’15 and Professor Eugene Domack, Hamilton College, Clinton, New York, USA.

Learn more about their field excursion at Tasmanian Field Studies


The Tasmanian Tiger (scientifically known as the thylacine) has survived in Tasmanian folklore as a legend and highly elusive animal to many who insist in its existence. A new technique in cryptozoology has allowed researchers to locate highly elusive and thought-to-be extinct animals, thereby proving their existence and increasing efforts to protect these ultra-rare animals. The technique, which involves collecting local leech samples and cross-analyzing the ingested blood with known target animal genomes, has proven effective in past trials and could be applied to Tasmania and the Tiger. Piggybacking off previous work from thylacine researchers, it may be possible to find leeches containing tiger blood and narrow the extent of their geographic range.

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The Future of Cryptozoology: Locating a Legend with a Leech

Michael Weinzierl

Blood sucking animals, including leeches, mosquitos, ticks, bedbugs and fleas, have always been regarded by humans through a negative context. They can be vectors and carriers of disease, pain and annoyance, which have earned them the universal label of ‘pests’. Various anti-flea, ticks, mosquito and leech products exist for both humans and our pets; a market subsists to purge the world of these decidedly pesky organisms. However, recent research and subsequent effort in the field of cryptozoology has utilized newfound abilities of these blood-sucking animals, giving them a purpose with a more positive connotation. This technique, which involves extrapolating sucked blood from these invertebrates and cross-analyzing the blood with known genomes, can be used to identify and potentially locate host animals that the blood-suckers have been in contact with (Hance). This emerging technique sheds blood-sucking animals in a new, positive light and adds a huge economic and scientific importance to these widely underappreciated animals. By analyzing mealblood, it can be possible to prove the existence of or even locate ultra-rare and endangered species that are difficult to find with conventional techniques, such as traps, cameras, infrared detectors, etc. The economic viability and relative ease of this method is noteworthy and attention should be given to this emerging method as cryptozoologists continue to search for endangered or thought-to-be extinct species, such as the Tasmanian tiger. Tasmania and the Tasmanian tiger, otherwise known as the thylacine, would be the perfect next logical location and target for this technique because of the quantity and quality of the blood-sucking organisms (especially leeches) found in Tasmania and the immense public attention and financial support such a project would receive.

Copenhagen Zoo and University of Copenhagen have in collaboration developed a new and revolutionary, yet simple and cheap, method for tracking mammals and getting an accurate account of the biodiversity of a tested area (Hance). Researchers collected haematophagous leeches from tropical jungles and cross-analyzed the blood for mammal DNA using extensive DNA library databases. By using this method, researchers can get an overview of the biodiversity of the mammals of the region without having to find them (Schnell et al.). Though the method has only been tested in the Central Annamite region of Vietnam, it could potentially be used universally wherever leeches are present. Before the advent of using leeches, it was difficult and expensive to monitor mammal species and populations living in impassable rainforest areas around the globe. Conventional methods such as camera traps, infrared sensors, collecting hair or fur samples, analyzing feces and tracking footprints are all time consuming and relatively ineffective, especially when dealing with rare, shy animals that occupy dense forest habitats. The problem is particularly acute in these tropical forests, where a disproportionate number of species are listed by the IUCN (International Union for Conservation of Nature)as ‘data deficient’ due to the difficulty of monitoring with these conventional approaches. Collecting leeches, however, requires little more than watching and waiting, as hungry leeches will eagerly come to the researchers in search of a host. The sampling and analysis does not require specially trained scientists, but can be carried out by local scientists. This would not be possible without recent advances in DNA-sequencing technology, which is what makes this method so innovative and contemporary.

With nearly one-quarter of mammalian species threatened, it is important to understand and maintain an accurate description of their distribution and conservation statues (Schnell et al.). In order to resolve this issue, the first leech field test was conducted in late 2012 in the dense forests of Vietnam with high success (Hance). Ultra-rare mammalian species, including the soala (Pseudoryx nghetinhensis) native to the Annamite Mountains of Vietnam and Laos, were the primary targets. This first (and only) field test did not present evidence for the existence of the target animal (the soala), but it did manage to present evidence for the existence of several other extremely rare species. 21 out of 25 leeches tested yielded mammalian mtDNA sequences, representing six species spanning three orders — Artiodactyla, Carnivora and Lagomorpha (Schnell et al. – See Figure 1b). The orders represented included the mainland serow (Capricornis maritimus), Chinese ferret-badger (Melogale moschata), the Annamite stripped rabbit (Nesolagus timminsi) and the Truong Son muntjac (Muntiacus truongsonensis) – some of which have not been seen in over twenty years.

There are several blood-sucking invertebrate candidates that could prove useful in implementing this technique, such as ticks, mosquitos or louses; however, the leeches are by far the most efficient and viable contenders for this project for specific reasons. According to Ida Schnell et al., in their research paper following the trial in Vietnam, “In addition to ticks and mosquitoes, haematophagous leeches represent promising candidates as, following feeding, they store concentrated blood for several months”. Later in the paper, they go on to describe the advantage of using leeches: “Terrestrial Haemadipsidae leeches (found in Southeast Asia, Madagascar, South Asia and Australia) are ideal for this method, due to their diverse prey base and readiness to attack humans, making them easy to collect.” Leeches are segmented, eucoelomate worms of the phylum Annelida, distinguished from other annelids by anterior and posterior suckers used for locomotion and feeding – on blood or soft body parts of other animals (Weisblat 752). Annelids (also called “ringed worms”) are a large phylum of segmented worms, with over 2,000 modern species including ragworms, earthworms and leeches, though are not to be confused with nematodes. Leeches have precisely 32 segments from five bilaterally paired stem cell lineages and are not capable of regeneration and do not add body segments throughout their life (Weisblat 752). They are bilaterally symmetrical, triploblastic, coelomate organisms and have specialized parapodia for locomotion ( They are found in marine environments from tidal zones to hydrothermal vents, in freshwater and in moist terrestrial environments. There are 650 known species of leeches in the world and about one fifth of leech species live in the sea, where they feed on fish. Leeches are hermaphrodites, each individual having both male and females reproductive organs. The bite of a leech is painless, due to its own anesthetic. After contact, an anti-coagulant serum is injected into the victim to prevent the blood from clotting. The leech will gorge itself up to five times its body weigh until it has had its fill and then just fall off. Sucked blood can stay in the leeches’ bloodstream for up to 4-18 months, depending on the leech, which represents a significant time frame for extrapolation and blood analysis. Furthermore, several studies have demonstrated that in the medical leeches (Hirudo medicinalis), viruses remain detectable in the blood meal for up to 27 weeks, indicating viral nucleic acid survival (Schnell et al.). A leech can survive several months to a year before feeding again, and its relatively large size and slow movement (compared to other blood-sucking invertebrates) make it the ideal candidate for this study.

About 100 species of leeches are known from Australia, and at least a dozen are found in Tasmania – most of which live in water. Among the common terrestrial species in Tasmania are Philaemon pungens, reaching about 20mm, and the striped P. grandis, or Tiger leech, which reaches about 56mm ( The Tiger leech is known locally as ‘limatang’ or ‘pacat’ (leaf leech), because it is usually found on leaves of lower vegetation ( It sports green, yellow / orange and black stripes and the bite can be physically felt. All leeches utilize thermoregulation to locate and identify prey, which is why warm-blooded mammals, such as the Tasmanian tiger, comprise the majority of their prey. It would not be uncommon for a leech to feed on the thylacine; in fact, leeches would have an easier time locating the elusive animal than humans would because of their specialized ability to locate prey. Leeches use a basic visual and mechanical system to locate prey, interpreting vibrations and shadows in their environment to determine where a potential host animal is located and what direction it is going (Harley et al/). As leeches mature, the visual system and the mechanical system don’t really change. What does change, however, is the integration of the visual and mechanical cues to make a final, more informed behavioral decision (Harley et al.). Terrestrial leech species, including the Tasmanian tiger leech, have been known to attack a host aerially by dropping out of the dense forest brush onto unsuspecting animals below using their acute visual and mechanical targeting systems. Additionally, the small size of the leech would go unnoticed by a thylacine, or any other elusive rare mammal, unlike the clumsy movement of a human, which would easily scare a suspecting tiger. Another strength of using leeches is that most leeches show clear species preferences in feeding, and some have strong preferences as to the anatomical site of attack (Weisblat 752). The thylacine would be an ideal host for a hungry leech because of its short fur, which would make it easier for a leech to penetrate its skin, its propensity to dwell in thick forest habitats, and its relatively large body, which would create substantial vibrations and offer a big target for a leech to locate and aerially attack.

The Tasmanian tiger (Thylacinus cynocephalus), declared officially extinct after the last known specimen died in the Hobart Zoo in 1936, has become a creature of legends and the subject of various Tasmanian folklore. The Tasmanian tiger, otherwise known as the thylacine, is a carnivorous marsupial native to Tasmania. The animal can reach up to 1.3 meters (51 inches) long, with its tail accounting for between 19-25 inches of that total (Campbell). Long, distinctive stripes cover its back and tail, which is inflexible and could be dragged along the ground. It had an incredibly large and powerful jaw as well as distinctively shaped paws. They do not howl but have been observed to produce a “yip-yip” sound when hunting and have been observed as having a very distinctive odor (Paddle 78).

Ignorance and irrational fear led to the supposed extinction of the Tasmanian tiger. The perceived economic threat of the thylacine against the livestock of the island-state led to a concerted government funded war of extermination waged against the species (Paddle 43). This led to a focused hunting of the thylacine and its eventual destruction by the “Tasmanian Bushmen”. By the time the persecution was seen as the tragedy that it was, the thylacine had been reduced to the brink of extinction, with the last known surviving member residing at the Hobart zoo his death on September 7th, 1936 (Bailey 26). Today, the thylacine is listed as officially extinct by the WWF and IUCN. However, the Australian Rare Fauna Research Association reports to have 3,800 sightings on file from mainland Australia since the 1936 extinction date, while the Animal Research Centre of Australia recorded 138 reports up to 1998 and the Department of Conservation and Land Management recorded 65 in Western Australia over the same period (Fausch). Additionally, Independent thylacine researchers Buck and Jonne Emburg of Tasmania have 360 Tasmanian reports and 269 post extinction reports (Campbell). Mainland sightings are frequently reported in South Victoria. Col Bailey, Thylacine researcher and author of Shadow of the Thylacine, has dedicated his life to proving the existence of the animal, stirring public support and protecting it from any further potential harm. He has had several supposed personal sightings and has documented all local sightings in Tasmania. Judging by his experience, any thylacine left in Tasmania would be in either Northeast or Southwest corners of the island, where the wilderness is the most dense and undisturbed. Thylacine dens tend to be in caves near large bodies or water or semi-aquatic environments, much like terrestrial leeches (Bailey 142). Lobster Lake, located in southern Tasmania, might be a good place for the first leech blood analysis beta test.

Despite the proven success of using leech blood to identify the DNA of the leech’s last meal, there are still some obvious limitations involved. First and foremost, though leech blood can help determine the biodiversity of an area, it does not help determine specific time and location of a host animal. A leech may feed on an animal and, 3 months later, the animal may be many miles away from the site of the feeding, especially fast-moving, nomadic mammals. Another issue may arise when trying to find a correlation between the initial feeding and the concentration of DNA left in the leech and the time that has lapsed (See Figure 1a). There is still no exact formula for determining the time between feeding and extrapolation/analysis, but rather a general curve, which is a weakness if trying to pinpoint the exact location or movement of an animal. Despite this, the method works well in determining the biodiversity of a general area. This is important in the field of cryptozoology, where proving the existence of an ultra-rare or assumed extinct animal is a success in itself. In the future, as the method receives more attention and develops, it may be possible to more accurately determine the time that has lapsed between feeding and extrapolation. Another useful advance may be to use other blood-sucking invertebrates, including ticks and mosquitos, for the same purpose. Though there is little primary research that has been conducted, there is one paper accepted in February 2012 focusing on Lyme disease in ticks that proved the viability of using tick blood meal for identifying the last host animal. The results were promising: “Of the 61 field-collected ticks, conclusive genus- and species-level identification [of the last host] was possible for 72% of the specimens” (Gariepy et al. Abstract). However, no further research has been implemented and leeches still remain the superior vector for identifying host DNA.

As cryptozoologists work to increase our knowledge of global biodiversity- and even work to prove the existence of animals thought to be extinct- it will be important to develop more sophisticated methods of locating and documenting these animals. The prospect of using blood sucking invertebrates, animals typically seen as harmful and annoying, to help identify target animals is promising. Using leeches to this effect has produced substantial results for the beta test in Vietnam in late 2012, and Tasmania and the thylacine are a great next logical step in continuing this research. In the future, more accurate results concerning time lapse may be possible, as well as using other blood sucking invertebrates such as ticks and mosquitos. Movement of the research to aquatic or marine environments, utilizing aquatic leeches, may be possible, but no research has yet been published in this realm. Future attention will be necessary to perfect this emerging method of cryptozoology, and the prospects of consequent results are exciting.


Figure 1. (Source: Schnell et al.)

A. Survival of mtDNA in goat blood ingested by Hirudo medicinalis over time, relative to freshly drawn sample.

B. Vietnamese field site location and examples of mammals identified in Haemadipsa leeches. From left to right: Annamite striped rabbit, small-toothed ferret-badger, Truong Son muntjac, serow.

Works Cited

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Hance, Jeremy. “Beyond Bigfoot: The Science of Cryptozoology.” Mongabay, 26 Mar. 2012. Web. 19 Sept. 2013. <>.

“Leeches.” Parks & Wildlife Service -. Tasmania Parks and Wildlife Service, 28 Nov. 2011. Web. 19 Sept. 2013. <>.

Bailey, Col. Shadow of the Thylacine. Scoresby, Vic.: Five Mile, 2013. Print.

Campbell, Cameron R. “A Natural History of the Tasmanian Tiger.” The Thylacine Museum – A Natural History of the Tasmanian Tiger. The Thylacine Museum, 2012. Web. 20 Oct. 2013. <>.

Paddle, Robert. The Last Tasmanian Tiger: The History and Extinction of the Thylacine. Cambridge: Cambridge UP, 2000. Print.

Fausch, Jeff. “Cryptozoology – Haunted History Society Australia.” Haunted History Society Australia. N.p., 2013. Web. 28 Oct. 2013. <>.

California Insititue of Technology. C. M. Harley, J. Cienfuegos, D. A. Wagenaar. “Switching Senses: Leeches shift the way they locate prey in adulthood.” ScienceDaily, 2 Nov. 2011. Web. 10 Dec. 2013

Ida Bærholm Schnell, Philip Francis Thomsen, Nicholas Wilkinson, Morten Rasmussen, Lars R.D. Jensen, Eske Willerslev, Mads F. Bertelsen, M. Thomas P. Gilbert. “Screening Mammal Biodiversity Using DNA from Leeches”. Current Biology – 24 April 2012 (Vol. 22, Issue 8, pp. R262-R263)

Gariepy, T.D., R. Lindsay, N. Ogden, and T.R. Gregory. “Identifying the Last Supper: Utility of the DNA Barcode Library for Bloodmeal Identification in Ticks.” Molecular Ecology Resources 12 (2012): 646-52. Blackwell Publishing Ltd., 16 Feb. 2012. Web. 10 Dec. 2013.

Weisblat, David A. “Leeches.” Current Biology 13.19 (2003): R752. Print.