WildLife Group
of the SAVA
Personal experience in
immobilisation of
spiral-horned antelope
HO Reuter
When immobilizing any antelope species, I generally
aim to achieve an immobilized state safe for the animal
and the human handlers with minimal stress, and little
risk of over-exertion and overheating of the animal.
If darted from helicopter, I prefer to get any antelope
species to show good induction signs within 1-2
minutes, and go down in sternal recumbency in 3-5
(maximum 7) minutes after darting and remain in a
good immobilized state without too much reaction
to stimuli, e.g. fighting, horn stabbing, kicking, no
trembling, good steady respiration and normal
mucous membrane colour and vital signs. For most
antelope species this is achieved with combinations of
opioids – (usually I combine Thianil to Etorphine (2:1),
with azaperone (not in impala), (or midazolam) plus
ketamine in the dart at various dose rates for various
species.
In my experience spiral horned antelope seem to
be more difficult to get down with similar drug
combinations, than most other antelope. They seem
to show a more pronounced excitement phase from
opioids, and if under-dosed will run very far, and
often are not very responsive to being herded by
helicopter, which in mountainous, rocky or thick bushy
terrain (their preferred habitiat) may result in difficult
recovery. When they do go down, they seldom stay
in sternal recumbency, often salivate profusely, and
may regurgitate rumen fluid or bloat more readily than
other antelope. This means that ground team must get
to them quite quickly, or the vet be off-loaded from the
chopper to keep the animal upright, keep the mouth
down to prevent chocking on saliva, etc.
10
In spiral horned antelope a higher than “normal” dose
of opioid is required per bodyweight. Whereas in most
other species I prefer mixing thianil and etorphine, in
the spiral horned species, I sometimes only use thianil.
Adding hyalase at 1500 to 2500 IU per dart does seem
to reduce down time sometimes (less beneficial than
in giraffe, rhino and elephant in my opinion, and
requires 3ml darts then). Good dart placement and a
high enough opioid dose is the most important factor
effecting quick downtime.
Using alpha 2 agonists certainly helps to reduce
down time in spiral horned antelope. (These drugs I
generally don’t use often on most other antelope, as
satisfactory immobilization is achieved with other drug
combinations, with less respiratory depression). I have
found, however, that the animals are even less likely
to remain sternally recumbent, they salivate more, and
bloat more easily if alpha 2 agonists is added to the
opioid, rather than azaperone (azaperone also used
at a higher dose than for most other species). The
quicker down time achieved by using medetomidine
is often the most desirable if darting from helicopter,
especially with mature, large kudu or eland bulls. In
nyala I don’t like using medetomidine or xylazine in
the dart, especially not if darted from the ground, in a
boma, or small camp, as these can normally easily be
handled, or even kept in standing / walking state with
other tranquilisers.
Even kudu and eland cows and sub-adults respond
well enough to high dose opioid and azaperone
cocktails by becoming recumbent, without kicking or