average they are longer and heavier than any other
known population to date, genuine six-footers are
uncommon and snakes longer than that are rare.
It was with all this in the background that I dared to
dream of producing a giant with Mick’s outsize
babies. I believe the formula for success is genetics
plus first clutch of young virgin female plus food plus
time. The Mick Thow clutch of young possessed a
good genetic mix for large size. The mother was a
young, second-generation, captive-bred Chappell
Island Tiger Snake and the
father was a large wild-caught
specimen from Boat Harbour,
north-west Tasmania, with a
big head. Genetic research
(Keogh et al., 2005) clearly
indicates that all the disjunct
Tiger Snake populations
(including many offshore
islands) created when sea
levels stabilised after the last
ice age a few thousand years
ago are very closely related
and constitute a single taxon - Notechis scutatus.
Localised conditions of climate but especially prey
type and seasonality have resulted in rapid and
repeated selection for different body sizes across
these populations. While not being separated for
long enough to warrant specific or sub-specific
status, some of these populations appear to have
diverged sufficiently from the parent populations on
the mainland and the main island of Tasmania to
display some apparent 'intergrade vigour' when
crossed. I discussed this phenomenon in relation to
Tiger Snakes at greater length in a previous article
(Fearn, 2014a) and given the frequency of reports
of Tiger Snakes being seen in the sea between
islands, rare but natural interbreeding probably
occurs between islands in close proximity with
favourable wind and current conditions for migrating
snakes. It would seem obvious that if you want to
grow out really big Tiger
Snakes, you would simply
breed and raise pure
Chappell Island specimens.
However, this strategy often
appears to result in disap-
pointment because many
people simply don’t under-
stand how the ecology of the
island works. The selection for
size is laser-like in its intensity
and results in a near 100%
death rate among the 20,000
or so neonates born on the island each year. Only a
tiny fraction of the biggest and fastest-growing
neonates survive to adulthood. Bridging the gap
from skinks to a 60g Mutton Bird chick is simply
beyond the capacity of the vast majority of young
snakes. If you breed Chappell Island tigers in
captivity and raise the young it is a statistical
‘ Only a ti ny fraction
of the biggest and
fastest
fastest-
-growing
neonates survive.... ’
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