488 Park Road, Park Orchards, Victoria, 3114, Australia
Originally published in Herpetofauna 35(2):118-119, December 2006.
A case of a captive male lowlands Copperhead (Austrelaps superbus) biting and killing a sibling is documented.
Immunity of snakes to their own venom is regarded as normal, with this immunity extending to others of the same species (see Hoser 1985). Cases not fitting this profile are so rare as to warrant reporting which is why the following case is documented here.
While Hoser (1985) found that immunity of snakes to their own venom was normal, there was one case that broke this profile.
The text from that paper is repeated below:
"In early 1980 Mr. Gary Stephenson reported an adult captive highlands Copperhead (Austrelaps superba) biting and envenomating an adult lowlands Copperhead (Austrelaps superba). The lowlands Copperhead died shortly afterwards, apparently due to the effects of the bite, exhibiting according to Mr. Stephenson, typical snakebite symptoms. The highlands Copperhead was still alive and in perfect health at the time of writing this article."
Stephenson was regarded as very reliable and hence the reporting of that unusual case in the paper. Had such an account been rendered by another less competent reptile keeper, the death may have been written off by myself as a case of bad husbandry, as an erroneous explanation of death and not reported in a paper.
At the time the paper was published I later noted in the same paper that the result (death) may have been due to differences between the two types of Copperhead. The Highland Copperhead has since been (generally) reclassified as a different but similar species (namely A. ramsayi), the lowlands form generally being known now as A. superbus (see for example Hoser 1989).
Notwithstanding this reclassification of the two snakes, it is known that similar species in other genera do appear to be immune to the venom from one another (e.g. Acanthophis). With reference to the case involving Stephenson as documented by Hoser (1985), this latest case, while unexpected, was not from the realms of impossibility.
THE 2004 CASES
On 5 March 2004, eight young Copperheads (Austrelaps superbus) were born in the collection of Federico Rossignolli. The female was from Apollo Bay, Victoria.
I immediately obtained two males from the litter which were housed together.
At birth both snakes had a total length of 20.5 cm, with the six other siblings measuring 19.5, 19, 19, 18.5, 18.5 and 18 cm in total length.
The snakes were force or assist fed a diet of fish and mouse legs and grew rapidly.
By 25 May 2004, the two snakes each had a total length of 32 cm.
At 7 PM on 16 May 2004, the plastic container housing the two snakes was being watched when one snake was seen biting another on the mid-neck. Notable is that the snakes or their housing (cage) had not been moved or disturbed in any way prior. The cage had not been opened or touched.
The bitten snake died well within 15 minutes and ended up dead in the cage in an upside down position. It made some agonizing twists and turns prior to finally resting upside down. These appeared to be typical venomous snake-bite symptoms.
Both snakes were immediately pre-slough, (cleared eyes) and the reason for the bite is unknown, but presumably related to feeding or perhaps a "fear" or "anger" bite.
Noting that cannibalism was a possibility, it did not occur in this case. Other than one snake biting another on the neck, at no stage did one try to eat another. Nor did the bitten snake attempt to retaliate by biting it's sibling brother.
Two other snakes from the same litter while in the care of another keeper allegedly bit one another and also died rapidly.
These cases imply quite clearly that not only are Copperhead species not immune to one another's venom, but in some cases at least, they are not immune to the venom of siblings fed on identical diet and of the same sex (in one case both males).
From a husbandry and breeding perspective this could raise problems in terms of this species and it emphases the need as a rule to keep specimens apart unless breeding or the snakes have been rendered "venomoid" (venom glands removed).
Perhaps a more important question is whether or not the cases involving Austrelaps as documented here and in Hoser (1985) are relatively unusual, or in fact typical of the species.
That lack of immunity to venom in this species may in fact be typical for it is indicated in part by field observations of male combat in Austrelaps (Jenner 2004). As per the cover photo on Herpetofauna 34(1) by John Dallwitz (treated here as part of Jenner 2004) and sources for the combat in the genus as cited by Jenner 2004, all three described species of this genus of snakes are unusual among Australian elapids in that males hold their heads and necks away from one another and no biting is observed.
This is in stark contrast to species such as Blue-bellied Black ("Pseudechis colletti" as per classification of Cogger 2000) and Collett's ("Pseudechis colletti" as per classification of Cogger 2000), in which males aggressively bite and envenomate one another (see photos by Hoser in Eipper 2002 for an example of this).
Assuming non-immunity to be the case in Austrelaps, it'd be reasonable to infer that this is a recently evolved trait in terms of the evolutionary time frame. One would assume that it may be a result of one or a small number of mutations, which must presumably confer some other significant advantage to the species.
What this may be is uncertain.
Based on the above reported observations, it also appears that further research into the exact means of immunity of snakes to venom should be undertaken as well as the reason that this immunity does not appear to extend to the genus Austrelaps.
The following people are thanked or acknowledged.
Gary Stephenson for providing the information used in the relevant part of the 1985 paper. All Australian reptiles referred to in this paper were held or moved pursuant to licences and permits issued by the authorities in NSW and Victoria and they are thanked accordingly for these.
Cogger, H. G. 2000. Reptiles and Amphibians of Australia (Sixth edition), Reed/New Holland Publishers, Sydney, Australia:808 pp.
Eipper, S. C. 2002. Male combat in venomous snakes. Crocodilian - Journal of the Victorian Association of Amateur Herpetologists 4(1):34-35.
Hoser, R. T. 1985. On the question of immunity of snakes. Litt. Serp. 5 (6): 219-232.
Hoser, R. T. 1989. Australian Reptiles and Frogs. Pierson Publishing, Mosman, NSW, Australia. 238 pp.
Hoser, R. T. 1996. Interspecific immunity to venom in snakes. Herpetofauna 26 (1):26-27.
Jenner, W. 2004. Male ritual combat in the Pygmy Copperhead Snake (Austrelaps labialis:Elapidae). Herpetofauna 34(1):17-18.
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