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    Little is known of the reproductive behaviour of the thylacine.  Most of what we do know is based on the fortuitous observations of a small number of naturalists, the detailed dissections of reproductive organs by anatomists, and the historical field observations of bushmen.  Comparisons have also been made with the reproductive behaviour of the thylacine's nearest living relatives, the quolls (Dasyurus spp.), and the Tasmanian devil (Sarcophilus harrisii).

    Marsupial reproductive strategies are focused largely on the lactation phase, in contrast with placental mammals, where intrauterine development of the young is the primary reproductive investment.

female thylacine with visibly distended pouch - Beaumaris Zoo (QD), 1928
A female thylacine with visibly distended pouch.
This image is from a film taken at the Beaumaris Zoo (QD) in early 1928.
Breeding season:

    The first study on the breeding season of the thylacine was that undertaken by Dr. Eric Guiler (1961) of the University of Tasmania.  Guiler states:

    "It is assumed from all accounts that thylacines breed once a year and this is in line with the general pattern of reproduction in the Dasyures".

    Guiler investigated the surrender dates for sub-adult thylacines submitted for government bounty in the 21-year period between 1888 and 1909.  His study comprised 152 thylacines, made up of 52 pups, 45 young and 55 half-grown specimens.  Guiler's analysis showed that sub-adult thylacines were taken throughout the year. He records a peak submission for pups between May and August, and concludes that an extended breeding season of four months existed, with a degree of out-of-phase breeding.  This, Guiler states, "is commensurate with the present concept of dasyure breeding activity".

Monthly distribution of the catch of young thylacines submitted for government bounty
monthly distribution of the catch of young thylacines submitted for government bounty
Source: GUILER, E. R., 1961. Breeding season of the Thylacine. J. Mammal.42: 396-7.
    Sleightholme & Campbell (2014), in their recently published reassessment of the thylacine's breeding season, contend that the bounty records contain inherent anomalies that undermine Guiler's findings, and argued that historical newspaper reports, together with museum and zoo records, provide better data to determine the natural boundaries of the breeding season of the thylacine. 

    Sleightholme & Campbell assert that the seasonal nature of snaring, the practice of hawking, and the incorrect grading of skins for bounty payment would have distorted Guiler's breeding season parameters:

    Snaring was predominantly a seasonal activity, and trappers would often spend several weeks (or even months) in the field before returning home to submit their skins for bounty.  These skins would have been recorded in the bounty records for the month of submission, and not necessarily the month of kill.  What Guiler identified as out-of-phase breeding may be the result of the distortive effect of bulk submissions. 

    Hawking of skins by bushmen was common practice, with several weeks (or possibly months) elapsing between kill and bounty submission.  The naturalist Michael Sharland (1962), in his book "Tasmanian Wild Life", notes: 

    "Over the years many of the animals fell victim to gun and snare, and it was only a man with a deficient sense of business who would be content with the government bounty.  With a scalp hanging from the saddle, the hunter rode to homesteads over a wide area and proudly exhibited his catch to each farmer in turn, declaring it had been taken on or adjacent to his farm and thus collecting tribute, the farmer being only too happy to help towards the eradication of any animal that menaced his sheep.  Finally, when the odorous relic had reached a condition in which no further hawking for rewards was possible, it was deposited at the nearest police station where the government bounty was handed out.  Over the years, therefore, the business of catching the Tiger yielded good returns".

    The arbitrary nature of bounty grading often led to the incorrect attribution of older offspring as "cubs" or "pups", and this would undoubtedly have skewed Guiler's findings.  Guiler (1985) states: "The clerks differentiated between pups and half-grown young in about two-thirds of the claims".  One would assume that most clerks adopted a "small", "medium" and "large" approach to this type of work, rather than follow any scientific guidelines.

    In addition to bounty record irregularities, the effects of disease, as well as animals being remotely situated for sexual encounter, may have resulted in some out-of-phase breeding, further distorting Guiler's findings.  This certainly must have been the case as the species became rare and remotely dispersed at the beginning of the twentieth century.

    Recently, Devil Facial Tumour Disease (DFTD) has led to the reproductive season for Tasmanian devils being less well-defined, with births spread out throughout the year.  During the early years of the twentieth century, an illness described as being mange or distemper-like decimated thylacine numbers.  It is probable, just like the effects of DFTD in devil populations, that disease may have resulted in a degree of out-of-phase breeding in thylacine populations.

    Sleightholme & Campbell state that the bounty records upon which Guiler based his breeding season parameters were essentially dates for the payment of bounty.  Submission peaks in the records would, by virtue of the distortions caused through bulk submission of skins, hawking, and incorrect grading, not necessarily reflect the true breeding pattern of the thylacine.  This, they argued, justified a revision of Guiler's findings.

    As the government bounty excluded pouch-dependent young, and the somewhat amorphous appellations "young" or "pup" were essentially terms applied to young at heel, they looked to other sources for evidence as to when breeding historically took place.  One reliable source was the Tasmanian press.  Thylacine captures or kills were regularly featured in local newspaper reports.  Other sources include zoo and museum records.
A Native Tigress
A newspaper clipping from the North West Post of the 5th May 1888 (p. 2).
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