Australian Death Adders in Drag.
Why being a he/she may help in the race to reproduce.
Raymond Hoser
488 Park Road
Park Orchards, Victoria,
3114, Australia.
E-mail: adder@smuggled.com
Originally published in The Herptile 30(4):139-143.
ABSTRACT
For the first
time ever, this paper reports on an observed behavioral trait of male Death
Adders (Acanthophis antarcticus, Acanthophis bottomi, Acanthophis pyrrhus and Acanthophis woolfi) and Tiger Snakes (Notechis scutatus) that may have evolved
as a counter or an addition to male/male combat in terms of sexual selection in
male snakes.
In numerous
observed cases, two captive male Death Adders have been placed in a cage with a
female Death Adder and instead of one or other mating the female, one male is
observed mating the other male.
In the first
instances this was suspected as aberrant or homosexual behaviour, but based on
the frequency of the observation it appears to be common and not genuine
homosexual behaviour as interpreted for humans. Furthermore it appears that the smaller (sub-dominant males) are
the ones that usually mimic females (called he/she's in this paper) and allow
themselves to be mounted by males. The
evolution of this trait may have conferred some kind of advantage on smaller
males over larger ones and hence aided the evolutionary push towards the
smaller size of males versus females in some elapids including all Acanthophis species (as listed by Hoser
2002). Further explanation follows in the paper.
INTRODUCTION
- THE FIRST OBSERVATIONS
Over many
years of keeping Death Adders it was noted that in some cases if two or more
reproductively active males were placed with a female, sometimes one male would
be observed trying to copulate with the other male instead of the female.
The initial
interpretation of this was that it was aberrant homosexual behavior in terms of
the males.
However in
cases where just one male was placed with a female (either male), the result
would be a normal male/female mating.
The situation
just described was notable for other reasons as well.
Almost without
exception, if a given pair of Death Adders known to engage in such behaviour
were introduced together with a female, the same male/male mating response
seemed to ensue and in no case would either the roles between the males be reversed
or would the subdominant male ever be seen resisting or moving away from the
other male trying to mate with it.
In almost all
cases, it was the smaller male that allowed itself to be mounted by the larger
male.
In my own
situation, I had observed this in Acanthophis
antarcticus from Sydney, New South Wales, Acanthophis bottomi from Kunnanurra, Western Australia and Acanthophis pyrrhus from north of Port
Hedland, Western Australia.
Another
keeper, Roy Pails of Ballarat, Victoria, reported the same behavior when he
introduced a pair of male Acanthophis
woolfi to a female, all from Dajarra, Queensland.
Later when he
introduced the males to the female, one at a time, both mounted and mated the
female.
In other
words, he/she snakes are probably a feature of all Acanthophis species and the lack of observations for the other
described species is almost certainly a result of less people keeping them
rather than that those species don't engage in such behavior.
At first the
trait was thought to be an aberrance related primarily to the captive
situation, but this theory took a tumble when it was noted that the same
occurred in very large cages where males had the opportunity to get well away
from one another.
In other words
it appeared to be a deliberate move by one male to fool the other male into
mating with it and may have had a parallel in the wild state.
The problem of
opportunistically finding a pair of male Death Adders attempting to have sex is
huge. From a practical point of view,
finding a single Dearth Adder in the wild isn't easy and to find two in the
wild trying to have sex would be nearly impossible.
A
CASE IN THE WILD
This didn't
involve Death Adders, but rather Tiger Snakes (Notechis scutatus) and is reported here as it indicates that he/she
snakes may be far more common than is generally realized among herpetologists.
On 7 February
2003 at 2.30 PM I received a phone call at "Snakebusters" (äâ)
from the administration office at the Diamond Creek East Primary School,
Diamond Creek, Victoria.
The call was
to remove a dangerously venomous Tiger Snake that had been seen going under a
large concrete slab adjacent to a playground.
I was able to
lift the slab and underneath found a large and very thick-set four foot Tiger
Snake (Notechis scutatus) on top of and
obviously trying to mate a smaller and much thinner three foot one.
Both Tiger
Snakes were males.
In other
words, male snakes taking on the role of female snakes is not just something
restricted to the captive situation.
WHY
DO "HE" SNAKES BECOME "SHE" SNAKES?
The smaller
Tiger Snake could have easily fled from the male if he did not want to partake
in the sexual overtures from the male.
That he did
not is significant and indicated that he/she behavior is a phenomena that
occurs in Australian elapids. Tiger
Snakes are also known to be a species to engage in male/male combat, which is
generally in relation to breeding activity.
However in
terms of my own captive observations of this species and other Australian
elapids that engage in male/male combat (including of the genera Cannia, Notechis, Pseudechis and Pseudonaja) the following points are
noted.
Combat most
often occurs in snakes of similar size.
When there is a strong size disparity, the two snakes will engage in
obvious mutual tongue-flicker, with what then appears to be a sort of
"stand-off" occurring and the smaller snake ceding right of way to
the larger one.
The result is
that the smaller snake will move away quickly and only rarely will the larger
one bother to pursue it.
In species
where male combat is a means to decide who gets to mate, extra size is an
evident advantage.
Hence the push
for these species to have larger males and males that are generally larger than
females. This is evident in species in
the genera Cannia, Notechis, Pseudechis and Pseudonaja.
Acanthophis is
relatively unusual among Australian genera of larger elapids in that male/male
combat is effectively unknown (Hoser 1995).
Notwithstanding this, it is evident from observations, that larger
snakes do as a matter of course get priority of way over smaller ones, even if
by virtue of their inherent bulk. In
the rarely observed situations of more than one Death Adder trying to mate with
a given female, the larger one will obviously be able to push the smaller one
off the female.
As for all
snakes, Death Adders are very conscious of one another and in confined spaces
(as seen in captivity) will be aware of issues such as size and dominance and
will form a sort of social hierarchy generally based on size and gender.
Assuming that
size is an advantage in males, even for species that do not engage in male-male
combat, then until now, there has been no reasonable explanation for an
advantage to be had by smaller males in the mating situation, or at least one
that can be used as an explanation for the evolutionary push towards males
being smaller in size and smaller than females, save for the general theory
that reproductive effort is made proportionately easier in proportionately
larger snakes.
Mating in
captive (and presumably wild) elapids tends to run a similar course. Once the male has passed his semen, he will
tend to rest for a period ranging from hours to days.
If in a
competitive captive situation a subdominant male can fool a dominant one into
passing semen either in or on itself, rather than on a female, the subdominant
male may then be able to mate with the female himself and hence have an
evolutionary advantage.
Hence a
potential push towards snakes that become he/she's or perhaps even smaller
snakes.
This is
particularly so, if it is evident that all (or most) male snakes of a given
species such as Death Adders (Acanthophis)
have the ability to become he/she's as needed.
My own
observations indicate this to be so.
In cages with
multiple males, it is relatively uncommon to see two or more males trying to
mate a female, but it is not uncommon to see one male trying to mate another.
Hence it seems
that males will become he/she's more readily than they will attempt to
competitively mount the female snake.
The
observation alone indicates that the he/she state is a common one and perhaps
far more common in the wild state than has been previously guessed.
Hence we have
an explanation for why subdominant (smaller) snakes may be able to have a
selection advantage over larger ones and why the evolutionary trend has been
towards smaller males in species such as Death Adders.
HE/SHE
TIGER SNAKES AND IT'S WIDER MEANING
The
observation of a male Tiger Snake allowing itself to take on the role of a
female snake is even more significant and not just because it was in the wild
state.
Tiger Snakes
are known to engage in male/male combat.
Based on the
size disparity of the two snakes observed, it appears that the smaller one took
on the guise of being a female rather than to engage in a hopeless (losing)
combat with a far larger snake.
Generally
mature Tiger Snakes are of closer size class, with the two specimens observed
being at the upper and lower limits of size in mature snakes. Hence the observation at Diamond Creek may
well have been the exception rather than the norm for the species.
However it
does indicate that the ability of snakes to become he/she's may be common to
many Australian elapids, but only commonly manifests in species which do not
engage in male/male combat.
The fact that
the ability of males to mimic females appears to be pre-evolved in most elapids
also means that relative size reduction in males of given taxa may have been
able to evolve more than once and been dependent on the relative importance of
male combat in taxa over long periods, or perhaps vice-versa.
This also
makes it possible to infer which species are also most likely to engage in
he/she behavior.
Snakes in the
genus Pailsus where the females are
also the larger sex (like in Acanthophis),
are generally known not to engage in male/male combat and hence in the captive
situation, it is likely that he/she behavior in males would be seen.
How common
he/she behavior is in other groups of snakes is also not known, but it may be
far more common than has been suspected so far.
I am aware of
cases of several male snakes being found in a cluster trying to copulate
another male in the following widely different species: Diamond Pythons (Morelia spilota) and Australian File
Snake (Achrochordus arafurae), with
no females being found.
Cases where
two or more overwintering and male only Yellow-faced Whipsnakes (Demansia psammophis) or Small-eyed
Snakes (Rhinoplocephalus nigrescens)
have been found sheltering under the same rock by myself in the Sydney region,
or similar cases involving Little-whip Snakes (Unechis flagellum) around Melbourne's north and west may also
represent cases where at least one male of the pair or group has adopted the
guise of a female in order to waste the reproductive effort of the other/s.
In the case of
the first and third species male combat is known, while the non-observation of
male combat in Rhinoplocephalus
nigrescens could well stem from it's cryptic habits and a lack of specimens
in captivity, rather than that the behavior doesn't occur in the species.
SUMMARY
Male elapid
snakes (and snakes of other families) masquerading as females and enticing
other males to mate with them, may not be homosexual as is the context of such
behavior as seen in humans. He/she snakes are acting in such a manner in
order to aid their own chances of mating with a female, including in cases
where based on size, the he/she snakes would otherwise be subdominant and
perhaps unable to mate with a female if competing by combat or size.
He/she
behavior in male snakes is probably quite common both in captivity and in the
wild for many species.
ACKNOWLEDGMENTS
Several
herpetologists, including those named in this paper who freely shared their
observations with me.
REFERENCES
CITED
Hoser, R. T.
1995. Australia’s Death Adders, Genus Acanthophis,
The Reptilian 3 (4) pp. 7-21 and
cover, 3 (5):27-34.
Hoser, R. T.
2002 Death Adders (Genus Acanthophis):
An Updated overview, including descriptions of 3 New Island species and 2 New
Australian subspecies. Crocodilian:Journal
of the Victorian Association of Amateur Herpetologists 4(1) September,
pages 5-11,16-22,24-30, front and back covers.
© Australia's Snake Man Raymond Hoser.
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