(page 10)

1936 to present (continued):

    In the early 1990s, Professor Henry Nix of the Australian National University's Centre for Resource and Environmental Studies was intrigued by the frequency of thylacine sightings, and decided to investigate how closely they coincided with a computer generated map of where thylacines would most likely exist.  Nix developed a program called BIOCLIM, which accurately predicts where an animal, plant or particular ecosystem should occur.

    Nix drew upon scientific collections and official government records of where thylacines were shot and trapped by farmers and bounty hunters from the late 1800s until the early 1900s.  From this data, he generated a map showing optimal, sub optimal, and marginal areas of potential habitat.

    He then compared sighting records from 1936 onwards, and classified them into three groups based on their reliability - e.g., reliable, less reliable, and unreliable.  Discarding the unreliable sightings, he used the remaining sightings as independent data sets matching them against the BIOCLIM map.  The data sets matched the BIOCLIM predictions of where thylacines should occur almost perfectly, with the greatest frequency of sightings clustering within the areas of predicted optimum habitat.  Statistically, the chance that these independent data sets should so closely coincide is virtually zero.  Nix concluded: "These people really are seeing thylacines.", and advised that a thorough search for living thylacines be made before expending considerable resources in an attempt to clone the species.

    Adherents to the 1936 extinction hypothesis argue that if the thylacine were still extant, then a body would surely have been found or reported as road kill.  Also, prior to the appearance of Devil Facial Tumour Disease (DFTD), the devil population was increasing, and this they state, indicates the removal of the top predator.  Both these points are valid considerations.

    They also contend that a small population of thylacines could not survive because of the problems encountered with inbreeding.  Thylacines and their cousins, Tasmanian devils, have a low level of genetic diversity in comparison to other Australian marsupials (Miller et al. 2009), consistent with a "founder effect".  In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population - this is true for many island species. 

    Inbreeding and the subsequent loss of genetic diversity would certainly expose any remnant thylacine population to an increased risk of extinction.  This can be seen in DFTD, where few devils show any natural resistance to the disease.  A DFTD Management Strategy Report produced by the Department of Primary Industries, Water and Environment (February 2005) states:

    "Research has shown that due to the naturally low genetic diversity of Tasmanian devils, only a relatively low number of founder animals are required to represent the natural diversity of the species.  Population genetic research suggests that 25 individuals collected from a range of locations will be appropriate to establish and maintain a captive population long term".

    This is also likely to be true for the thylacine.

    It is not the intended purpose of this section to provide detailed analysis and comment on each and every sighting, as there have been literally hundreds in the last 80+ years.  Neither is it the museum's intention to argue that all sightings are genuine, as that too is blatantly not the case.  Rather, we aim to provide evidence for the reader to at least question the blank acceptance of the 1936 extinction hypothesis.

    Post-1936 sightings do not appear to be area specific - rather, they have been reported throughout the thylacine's entire historic range.  A number of the reported sightings were made by experienced bushmen who had previously hunted the thylacine, or by park rangers, both of which are highly unlikely to have made an error in identification.

distribution of all thylacine sightings 1936 - 1980
Distribution of all thylacine sightings 1936-1980.  Source: Smith 1980.

    Steven Smith (1981), in his report "The Tasmanian Tiger - 1980", proposed a scale to grade thylacine sightings.  The Smith scale is divided into 4 divisions: 

    1. Observer's reliability 
    2. Circumstances of report 
    3. Description of animal 
    4. Correlation with other sightings since 1934

    Each division is subdivided further with marks awarded in an ascending scale concurrent with the level of credibility.

A. Familiarity With Native Fauna
i. little or no knowledge of Tasmanian animals 0
ii. quite familiar with most Tasmanian animals 3
iii. very experienced with most Tasmanian animals 5
B. Credibility Within Community
i. unknown or poor credibility according to one source (may be interviewer) 0
ii. fair to good according to one source 3
i. good or excellent according to two or more sources 5
A. Distance Between Observer And Animal
i. greater than 500 metres 0
ii. 100 to 500 metres 1
iii. 50 to 99 metres 2
iv. less than 50 metres 3
B. Duration of Observation
i. less than 1 second 0
ii. 1 to 5 seconds 1
iii. 5.1 to 10 seconds 2
iv. more than 10 seconds 3
C. Visibility
i. poor visibility due to weather (rain, fog, snow, dark);
obscured (dense undergrowth, landscape feature)
ii. good visibility (line of vision not interrupted or obscured) 2
D. Number of Observers
i. one 0
ii. more than one 2
A. General Body Colour
A. General Body Colour 0
ii. dark brown 3
iii. sandy yellow; grey; light brown 5
B. Height from Shoulder
i. no description; less than 300 mms; greater than 750 mms 0
ii. large dog; 600 to 750 mms 3
iii. medium dog; 300 to 600 mms 5
C. Body Markings
i. no description; spots 0
ii. dark vertical stripes on torso 5
D. Distribution of Stripes
i. no description 0
ii. stripes extended from behind shoulders to base of tail and from backbone nearly to belly 2
E. Head
i. no description 0
ii. dog or wolf-like with small erect rounded ears 3
F. Tail
i. no description; thin; bushy; long-haired 0
ii. smooth; tapering; pole-like; very thick at butt 5
A. Geographic Correlation
i. no reports recorded within radius of 40 km 0
ii. reports recorded within radius of 10 - 40 km 1
iii. reports recorded within radius of 0 - 10 km 2
B. Time Correlation (if other sightings recorded within radius of 40 km)
i. no reports recorded within 30 years 0
ii. reports recorded in the previous 5 - 10 years 2
iii. reports recorded in the previous 5 years 3
    The maximum score that any sighting can obtain is 50 points within 4 rated levels from questionable to very good:
38 - 50 very good
25 - 37 good
15 - 24 fair
0 - 14 questionable

    Smith's scale is still used to this day as a reliable guide with which to rate sightings.

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