.
| Joey
/ pup development (continued):
Boardman noted that
the Museum Victoria pups with a head to rump measurement of 75mm were hairless
and devoid of any stripe pattern, their eyes were closed and the lips sealed
at the margins. The older Australian Museum pup with a head to rump
measurement of 288 mm was furred with evidence of stripes, its eyes were
open, and the lips fully formed. Without doubt, the single most important
discovery made during the compilation of the 5th revision of the ITSD was
the location in November 2011 of a litter of four pouch young in the collection
of the Department of Zoology (Faculty of Science) at Charles University
in Prague. The pouch young (DZCU 8021 [1-4]) were described for the
first time in a paper by Sleightholme, Robovský & Vohralík
published in the Australian Zoologist in December 2012. They
are the only known wet specimens of pouch young outside of Australia, and
with a mean crown-to-rump measurement of 26mm, the earliest in terms of
their morphology, with an estimated age of less than 2 weeks. The
discovery of the Charles |
| University specimens
provides researchers with a valuable insight into the early development
of the thylacine. Thylacine joeys first venture
from their mother's pouch at around 3 months of age, and are dependent
on their mother's milk to around 9 months. This dependency on their
mother's milk is noted in an article printed in the Mercury newspaper of
the 12th February 1924 (p. 6):
"A highly interesting
addition, in the shape of a family of Tasmanian tigers been made to the
Beaumaris Zoo this week. This comprises a female adult and three
young ones, about seven months old, who come from the rough and heavily
timbered country in the Tyenna Valley. When captured the young were
found in their mother's pouch, |
.
| Comparative
CRL of the Charles University [DZCU], National Museum of Victoria [NMV],
and Australian Museum [AMS] thylacine pouch young (arranged to scale).
Illustration: Nicholas Ayliffe (after Moeller). Source: Sleightholme,
S. R., Robovský, J. & Vohralík, V. 2012. Description
of four newly discovered thylacine pouch young and a comparison with Boardman
(1945), Australian Zoologist, 36(2): p. 237, Fig. 13. |
. |
being then only a few weeks old, and have
been successfully reared in captivity for some six months, when they were
handed over to the City Council entirely devoid of ferocity, but playful
and sufficiently tame to feed from their keeper's hand, as well as handsomely
marked with brown and black, the little ones are sure to attract considerable
attention by visitors to the zoo for the next few weeks. Although
given a supply of chopped up meat, they are not altogether at a stage when
they are independent of their maternal diet".
|
Ontogeny
(development) sequence a thylacine over a period of approximately three
years, by Arnfinn Holderer (2016), with technical contributions from C.
Campbell and Dr. S. Sleightholme. Click gear button in lower right
corner and select "?" to view control options for changing viewing angle
and distance. The counter in the top right corner denotes development
time in weeks. This animation is copyright and unauthorized use strictly
prohibited.
|
.
|
Little if anything is known about joey mortality within thylacine litters.
Adult thylacines have no natural predators within their island home, but
historically, the Tasmanian devil (Sarcophilus harrisii) and the
Wedge-tailed eagle (Aquila audax) are known to have preyed on their
young (Bailey, pers. comm.). Disease is another factor that would
diminish litter size. |
.
.
|
Tasmanian devil (Sarcophilus
harrisii).
|
|
.
|
Wedge-tailed eagle (Aquila
audax).
|
|
.
| The following graph
illustrating thylacine pup growth and development from birth to adulthood
is based on a series of biometric measurements from a limited number of
specimens for which the age or approximate age is known. Unfortunately,
body mass as a determinant could not be used, as virtually no data exists
for comparison. |
.
Thylacine Growth
& Development
.
.
Graph illustrating thylacine
pup growth and development from birth to adulthood. Red
measurements refer to nose to base of tail, and blue
measurements to tail length in 4 to 12. Orange
measurements in 1 to 3 refer to total body length. All measurements
are in millimetres. Source: Dr. Stephen Sleightholme.
.
| Click
graph icon to view source specimen measurements: |
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