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 newspaper clipping from the North West Post of the 5th May 1888 (p. 2).