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Page 12 Kokako 12 (1) 2005, Issue 25
Kokako 12 (1) 12-15, 2005 Discussion Paper
Euthanasia of Reptiles in New Zealand: Current Issues and Methods
B.D. (Brett) Gartrell1§ and E.J. (Ted) Kirk2
1Senior Lecturer in Avian and Wildlife Health, New Zealand Wildlife Health Centre,Massey University,
Private Bag 11-222, Palmerston North
2Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11-222, Palmerston North
§Author for correspondence. Email: B.Gartrell@massey.ac.nz
Abstract
Current best practice for euthanasia of reptiles in New
Zealand involves overdosage with either an inhalation
anaesthetic agent (e.g., halothane) or appropriately diluted
sodium pentobarbitone solution. Particular care is needed
to ensure that a “euthanised” reptile actually is dead.
Key Words: euthanasia, gecko, halothane, humane,
pentobarbitone, skink, tuatara, turtle.
Introduction
In addition to the tuatara, Sphenodon spp., New Zealand
has both geckos (Hoplodactylus spp.; Naultinus spp.) and
skinks (Cyclodina spp.; Oligosoma spp.) as native terrestrial
reptiles. Using Frye’s (1991) classification of chelonians as
tortoises if they live on land, terrapins if they live both on
land and in freshwater, and turtles if they live in the sea,
New Zealand has no native tortoises or terrapins and no
endemic turtles. (In New Zealand and Australia, terrapins
are often called turtles.) However, a number of exotic
chelonian species, and to a lesser extent some exotic
lizard species, are bred as pets in New Zealand, having
been introduced (often from Australia) before the current
bans on their importation. These and other species
(including terrestrial snakes) may be encountered as a
result of illicit or unintentional introductions into New
Zealand. Crocodilians and some other exotic reptiles may
be held as exhibits in zoos in New Zealand. New Zealand
has no endemic terrestrial snakes and the importation of
snakes into this country is prohibited.
Euthanasia (i.e., humane killing) of reptiles may be
necessary to relieve what we assess to be intractable
suffering in diseased or injured native species, for collection
of type specimens for museum collections, or for the
destruction of exotic species. The aim should be to
achieve euthanasia as rapidly and effectively as possible,
given the practicalities of the particular circumstances.
Euthanasia of reptiles is complicated by their varying ability
to breath-hold and to tolerate anaerobic conditions and
extremes of cold (Beaver and others, 2001). It can be
extremely difficult to determine whether a reptile is dead,
and recovery of apparently dead animals can occur (Mader,
1996). The particular technique chosen will also depend
on the size and type of reptile and on the intended later use
of the body.
Some techniques previously used for the euthanasia of
reptiles are no longer considered acceptable. These
include freezing, drowning in fixative solutions, intra-
coelomic (i.e., body cavity) injections of some undiluted
commercial euthanasia solutions (or of other chemicals),
and decapitation. In particular, the assumption that
decapitation results in rapid unconsciousness is disputed,
for it seems that the brain of a reptile can remain viable for
up to an hour after decapitation (Cooper and others, 1984;
Cooper, 2003). [In mammals, electrical waves have been
recorded from the brain for short periods after decapitation
and there has been debate as to whether these waves
were indicative of sensibility (Reilly, 1993).]
Recommended Procedures
The techniques recommended are grouped below; first
according to types of agents, and then according to sizes
and types of reptiles. The recommendations are believed
to reflect current best practice. Advances in our knowledge
of the neurophysiology of reptiles are required to confirm
the efficacy of the techniques; meanwhile, comments on
the recommendations will be welcomed by the present
authors.
Euthanasia of a reptile should not be initiated without first
ensuring that any necessary consultation with the
Department of Conservation (DoC) and/or the Ministry of
Agriculture & Forestry (MAF) has occurred, and that all
possible practicable subsequent good use of the reptile’s
body will be made.
A. Techniques Grouped by Types of Agents
1. Overdose with inhalation anaesthetic agents
Volatile anaesthetic agents such as halothane (“Halothane
BP VCA”, Vetpharm, New Zealand) or isoflurane (“Aerrane”,
Baxter Healthcare Ltd, Auckland) can be administered to
reptiles via chambers or sealed masks. In small reptiles
this method will induce unconsciousness quickly (i.e.,
within five minutes) and death should follow relatively
quickly (15-20 minutes in most species). In reptiles with a
strong ability to breath-hold (especially terrapins, tortoises
and turtles) “masking down” can take up to several hours
and is therefore not practicable. In all cases, care must be
taken to ensure that the dosed animals actually are dead,
and not simply deeply anaesthetised.
The above agents are only available under the direct
supervision of a veterinary surgeon. Operators should
take care to avoid exposure of human personnel to these
agents, and proper venting of gas chambers should be
carried out after the euthanasia.
Other inhalation agents, such as chloroform (which is
carcinogenic) or ether (which is highly flammable) are not
recommended. It is important to avoid direct contact with
solutions of either chloroform or ether.
2. Injection of sodium pentobarbitone solution
Injection of sodium pentobarbitone at a dose of 100 mg/kg
into the body cavity, or intravenously, or by intracardiac
injection will result in anaesthesia followed by death. The
simplest technique is to inject the pentobarbitone solution
into the heart or body cavity and then keep the reptile at
room temperature until death is confirmed. Use a small
diameter hypodermic needle to minimise any possible
Kokako 12 (1) 2005, Issue 25 Page 13
distress to the animal. Other barbiturates and undiluted
commercial solutions for euthanasia are likely to cause
pain at the injection site and are not recommended unless
given intravenously.
Pentobarbitone is effective but relatively slow (often up to
30 minutes) to take full effect. If the reptile is cold or is
moribund with poor circulation, the drug will take even
longer to take effect.
Injected barbiturates will cause histological tissue damage
after death and are not recommended in small reptiles
when tissues for microscopic examination will likely be
taken at a subsequent post mortem examination of the
reptile.
Pentobarbitone is now only available in New Zealand as
commercial euthanasia solutions (“Pentobarb 300” and
“Pentobarb 500”, National Veterinary Supplies, Auckland)
of 300 mg/ml and 500 mg/ml, respectively. The 300 mg/
ml solution should be diluted, using water-for-injection or
normal saline solution, to no more than 75 mg/ml prior to
use in reptiles. This dilution of the commercial product is
recommended to alleviate peritoneal irritation. These
drugs are only available for use by or under the direct
supervision of a veterinarian.
3. Combined sedation and euthanasia
This approach is useful with the larger reptiles, and is
especially useful when the reptile is dangerous or difficult
to handle, or when an owner is present. Sedation can be
achieved by intramuscular injection of either ketamine
(“Ketamine Injection”, Parnell Laboratories New Zealand
Ltd, Auckland) at 100 mg/kg, or zolazepam/tiletamine
(“Zoletil”, Virbac Laboratories (NZ) Ltd, Auckland) at 25
mg/kg of each component. Either drug should be injected
20-30 minutes before attempting euthanasia, and the
animals should be kept at room temperatures to facilitate
drug uptake and distribution.
The sedative used will immobilise the animals and allow
euthanasia to be performed using either inhaled
anaesthetics or injections of pentobarbitone solutions. All
of these drugs are only available for use by or under the
direct supervision of a veterinarian.
4. Decapitation followed by immediate pithing of the brain
This technique provides the most rapid mechanical means
of euthanasia, but it should be used on a conscious reptile
only when no alternative is available and the animal needs
to be killed immediately. It is an acceptable technique for
ensuring death after an animal has been deeply
anaesthetised.
The decapitation procedure must be performed quickly
and completely. Pithing of the brain within the severed
head is difficult in small reptiles and terrapins and needs to
be extensive. Alternatively, the brain of a small chelonian
may be pithed by passing a probe rapidly through the roof
of the animal’s mouth (McArthur, 2004). The possibility
exists that a conscious reptile might experience severe
pain before loss of consciousness supervenes. The
decapitation may spoil a body for museum purposes and
pithing renders the brain unsuitable for post mortem
examination.
5. Massive head trauma
The use of concussive head trauma is another mechanical
means of euthanasia reported as being feasible for reptiles
of less than one kilogram body weight (Anonymous, 2003).
For this technique to be effective, the reptile’s head must
impact against an unyielding surface with sufficient force to
produce immediate unconsciousness. The brain of the
reptile should then be destroyed immediately by pithing or
by crushing the skull. This method should only be used
when the use of other methods is not possible. Decapitation
following concussion is not considered suitable as reptiles
may recover consciousness, but can be used in combination
with immediate extensive pithing of the brain.
Shooting, by captive bolt or bullet, can also be used to
produce sudden, massive destruction of brain tissue.
However, in most instances the small size of the reptile’s
brain makes accurate aiming difficult. In addition, free
bullets are likely to be hazardous to humans and any other
nearby animals and to cause damage within the
surroundings.
B. Techniques Grouped by Size and Type of Reptile
1. Skinks, geckoes and tuatara
The two techniques recommended for use in these species
are the use of inhalation agents and the injection of
pentobarbitone solution. Either can be used with or without
prior sedation of the reptile.
These smaller reptiles have a limited ability to breath-hold
and they can be reliably euthanised by inhaled anaesthetic
agents. To protect the operator, the procedure should be
undertaken under a fume hood or in some other well
ventilated area.
The most reliable technique for a single animal is to pack
an appropriate hypodermic syringe barrel (5 ml, 10ml, or 20
ml), or an anaesthetic mask, with cotton swabs soaked in
an inhalation anaesthetic agent (usually halothane) and
place the reptile’s head and shoulders inside. Concentrated
halothane can damage plastics, so do not allow it to
contact the plastic of a good anaesthetic mask. Manual
restraint of the reptile is required and continued until
anaesthesia develops. The reptile should then be left in
place for at least 5 minutes after its respiratory movements
cease.
Alternatively, anaesthetic-soaked cotton swabs and several
reptiles together can be placed inside a small, gas proof,
sealed container. Multiple animals can be euthanised
safely in this way, provided that overcrowding and mixing
of species is avoided, to minimise stress to the animals.
The container should be vented carefully to avoid operator
exposure to the gas when the container is opened after the
animals are dead.
2. Marine reptiles
Marine reptiles which may be found in New Zealand’s
coastal waters are generally limited to five species of turtle
(the leathery turtle, Dermochelys coriacea; the loggerhead
turtle, Caretta caretta; the green turtle, Chelonia mydas;
the hawksbill turtle, Eretmochelys imbricata; and the Olive
Ridley turtle, Lepidochelys olivacea) and two species of
sea snake (the banded sea snake, Laticauda colubrina,
and the yellow-bellied sea snake, Pelamis platurus).
Page 14 Kokako 12 (1) 2005, Issue 25
The turtles have a capacity to breath-hold for prolonged
periods (Westera, 2004). Intra-coelomic injections of
pentobarbitone solution, with or without prior sedation, are
recommended for euthanasia. The brains of turtles are
small, and euthanasia by gunshot is not recommended.
Both species of sea snakes found in New Zealand waters
are venomous and extreme caution should be used when
handling these animals. Euthanasia is best achieved by
injecting pentobarbitone solution.
3. Non-native reptiles
(a) Terrapins and tortoises
These animals are possibly the most difficult reptiles to
euthanise by using gaseous agents, given their prolonged
breath-holding. Intra-coelomic injections of barbiturates
are effective, and are best combined with a sedative. (The
exotic red-eared terrapin, Trachemys scripta elegans, is
often kept as a household pet in New Zealand.)
(b) Snakes
Live snakes are found occasionally in New Zealand,
associated with materials unloaded at wharves: MAF
should be notified immediately. Venomous snakes (e.g.,
death adder, Acanthopis antarticus) are best euthanised
by intra-coelomic injections of sodium pentobarbitone
solution. Prior sedation is advisable when there is danger
to humans in giving an intra-coelomic injection. Never
handle or inject a venomous snake without the snake’s
head being adequately controlled by a competent assistant.
Non-venomous snakes, such as pythons (e.g., Calabar
python, Calabar reihhardtii) can be euthanised by inhalation
anaesthesia or sodium pentobarbitone injection, with or
without prior sedation, depending on their size and ease of
handling.
(c) Large lizards
A small number of collections of large exotic lizards (e.g.,
including, variously, green iguanas, Iguana iguana; bearded
dragons, Pogona spp.; Australian dragons, Ctenophorus
spp.; and Australian dragon lizards, Amphibolurus spp.)
are maintained in New Zealand.
Injections of sodium pentobarbitone solution, or combined
sedation and inhalation anaesthesia are recommended,
particularly with larger and more dangerous lizards (if
brought into New Zealand), such as the Australian monitor
lizard, Varanus brevicaudatus, which can exceed 2 m in
length.
(d) Crocodilians
Australia has two species of crocodiles: a freshwater
crocodile, Crocodylus johnstoni, and a saltwater crocodile,
Crocodylus porous. Small specimens can be sedated with
ketamine or zoletil and then euthanised by injection of
sodium pentobarbitone solution. Larger specimens should
be approached with caution, and a captive bolt gun or a
regular rifle may be required, with careful attention to the
safety of operators and observers: the weapon should be
aimed just caudal to the animal’s eyes, close to the dorsal
midline, and the bolt or bullet should be directed toward the
underside of the head, just caudal to the jaw on the
opposite side.
Confirmation of Death
A conservative approach to declaring death in reptiles is
advisable. Cessation of respiration is the most obvious
sign of deep anaesthesia or death. When hypothermic or
deeply anaesthetised, reptiles can have a respiration rate
which is measured in “minutes per breath” rather then
breaths per minute. Respirations are most easily seen by
opening the (anaesthetised) animal’s mouth and observing
the glottis for some minutes.
Cessation of cardiac function is more difficult to establish.
Commonly, no heartbeat is audible even in normal,
unanaesthetised reptiles. Electrocardiograph tracings are
unreliable, because reptiles can survive episodes in which
their heart rates drop to “several minutes per beat (Mader,
1996; Westera, 2004). In larger reptiles, doppler blood
flow analysis may be useful. The absence of deep pain
responses to stimuli such as toe clamping with forceps
may help to determine that an animal is at least deeply
anaesthetised but, again, is not a reliable indicator of death
(Close and others, 1997). Thus, there is no completely
reliable technique currently available for confirming that an
intact, overdosed reptile has died shortly before
examination.
If the reptile is to be preserved in a fixative solution for
museum or diagnostic purposes, it is advisable to check
the deeply anaesthetised animal for lack of visible respiratory
movements and absence of deep pain responses, and
then perfuse the animal with the preservative solution
(while there is no doubt that the anaesthesia remains
deep). If the reptile’s body is not to be fixed, it is best to
place the animal in a sealed container, refrigerate and
check again 24 hours later for the absence of respiration
and deep pain responses, before disposing of the body.
Disposal of Cadavers
The bodies of native reptiles which have been euthanised,
if they are not being sent for post mortem examination or
being used directly for museum purposes, should
nevertheless still be treated with respect, and incinerated
or buried. The bodies of exotic reptiles should be referred
to MAF. (MAF is likely to have been already consulted.)
When barbiturate solutions have been used in the
euthanasia, it is important to ensure that the now-toxic
body of the reptile cannot be eaten by another animal.
There are, for example, recorded fatalities in dogs which
have eaten pentobarbitone-loaded tissues which operators
have discarded from other animals. There may also be the
wishes of local iwi to respect in regards to disposal of the
body.
In all cases which do not already involve MAF or DoC, it is
worth checking with the local DoC office, or the DoC wildlife
health co-ordinator before disposing of the body. It should
be remembered that the body of an uncommon species
may be worth archiving in a museum or the New Zealand
Wildlife Health Centre. The method of euthanasia used will
often depend on the ultimate use of the body, so it is
preferable to clarify this use before beginning the euthanasia.
Kokako 12 (1) 2005, Issue 25 Page 15
Discussion
The word “euthanasia” is composed of the Greek terms
“eu”, indicating good, and “thanatos”, meaning death: a
“good, gentle death” is thus our overriding objective and
depends on the efficient use of a rapid and dignified
procedure, with the safety of the operators also important
(Morton, 2004).
The recommended use of sodium pentobarbitone solution
is consistent with observations within the Massey University
Veterinary School that red-eared terrapins overdosed intra-
coelomically with a 60 mg/ml solution became progressively
sedated, without any signs of distress or excitement, and
then quietly died.
Williams (2004) has outlined the limitations of using carbon
dioxide for euthanasia in several groups of animals. The
present authors have no experience of using this technique
in reptiles, but the use of carbon dioxide in these animals
would be subject to the same breath-holding limitations as
apply with other inhalation agents (Close and others,
1997).
The use of adequate procedures for euthanasia under field
conditions (especially on off-shore islands with difficult
access) may present some problems. In instances in
which it is necessary to euthanise a sentinel animal and/or
an animal with an irreversible chronic disease, it may be
feasible (because native reptiles are of small size) to
transport the live animal to the mainland and then, preferably,
to a veterinary hospital for sampling and euthanasia. Many
of the protozoal and metabolic diseases of reptiles are only
able to be diagnosed by examining fresh faecal smears
and other samples from a live animal (McInnes and others,
2004).
This approach can involve some conflicts for people who
may desire to treat the sick reptile. Treatment will be likely
to kill infective organisms, alter antibiotic sensitivities and
cause histological changes within the animal’s body - all of
which could impede a precise diagnosis which might be
needed in order to help other reptiles in the group from
which the individual was taken.
In the field, tissue samples are usually placed in 70%
alcohol solution, because the transport and use of 10%
formalin solutions is generally regarded as hazardous to
humans, even although formalin is a better fixative than
alcohol. Regardless of the location and technique used for
euthanasia of a reptile, the possibility of an infection being
zoonotic (i.e., transmissible from the reptile to human
beings) should be always kept in mind.
Conclusions
Methods of killing previously advocated for reptiles have
included techniques which are now regarded as possibly
producing significant pain and suffering before
unconsciousness occurs, and these should be avoided.
The techniques outlined above may, in their turn, be
superseded as our knowledge of reptilian neurophysiology
improves. Meanwhile, the present recommended best
practice is to use inhaled anaesthetic agents and/or injection
of sodium pentobarbitone solution.
Acknowledgements
The authors thank Nicola Smith, Paul Chambers, Katja
Geschke, Kate McInnes and Craig Johnson for their
comments on this manuscript.
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Comments/criticisms/suggestions relating to the above
summary will be welcomed and should be sent to the
senior author (E-mail: B.Gartrell@massey.ac.nz).
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