One of the highest occurrences of mortalities among giraffes (Giraffa camelopardalis) takes place during immobilisations, captures and translocations. Common mistakes, human error, unforeseen risks, the awkward anatomy and the sheer size of the animal are leading factors for giraffes’ mortalities during these operations. Many risks can be circumvented but some risks are unpreventable, often due to terrain characteristics (rivers, deep ditches, holes and rocky terrain). From 2011 to 2021, seventy-five giraffes were successfully immobilised and captured to collect biological and physiological data from eight different study areas across South Africa. A 0% mortality and injury rate was achieved and, therefore, the techniques described in this paper are testimony to the advances and improvements of capture techniques and drugs. Biological information and capture experiences were noted for 75 immobilised giraffes, of which, knockdown time data were recorded for 43 individuals. Effective and safe immobilisation requires a competent team, proper planning, skill and knowledge. In this manuscript, we address procedures, techniques, ethical compliance, welfare and safety of the study animals. General experiences and lessons learned are also shared and should benefit future captures and immobilisations by limiting the risks involved. The sharing of experiences and information could influence and improve critical assessments of different capture techniques and can likely contribute to the success rate of immobilisation and translocation success for giraffes in the future.

Adult giraffes reach heights of 4.5 m with a heart-to-head distance of over 2 m, making cranial blood supply challenging. Ultrasound confirmed that the giraffe jugular vein collapses during head movement from ground level to fully erect, negating the possibility of a siphon mechanism in the neck. We showed that a short-length siphon structure over a simulated head-to-heart distance for a giraffe significantly influences flow in a collapsible tube. The siphon structure is determined according to brain case measurements. The short-length siphon structure in a shorter-necked ostrich showed no significant increase in flow. The shorter head-to-heart distance might be the reason for the lack of effect in ostriches. A siphon mechanism situated in the cranium is certainly possible, with a significant effect exerted on the amount of pressure the heart must generate to allow adequate cranial blood perfusion in a long-necked giraffe. The study validated that a cranial-bound siphon structure can operate and will be of significant value for adequate cranial blood perfusion in long-necked species such as giraffes and might also have existed in extinct species of long-necked dinosaurs.

Disorders of sexual development (DSD) in wild mammals are rarely described. A male South African giraffe (Giraffa camelopardalis giraffa) was identified with bilateral cryptorchidism. The testes were intra-abdominal, smaller and less ovoid than in normal male giraffes. The right testis was situated more cranially than the left and connected to a longer deferent duct with normal ampullae. One distended vesicular gland filled with mucoid material was identified. A short penis, situated in the perineal area, was directed caudally and presented hypospadias. Histologically, testicular hypoplasia was present; the epididymis tubules contained no spermatozoa and the deferent duct and vesicular gland were inflamed. The blood testosterone concentration was 16.27 nmol/L and oestrone sulphate concentration was 0.03 ng/mL. The aetiology of the abnormalities is unknown.

The distinctive long neck of the giraffe (Giraffa camelopardalis) entails functional difficulties brought about by the extended distance between the heart and the head. Blood must be circulated over 2 m from the heart to the brain against gravitational force. The natural movement of the head to ground level would result in a large volume of blood moving toward the brain with the force of gravity. Large blood volumes also rush to the brain during bulls’ fighting (necking), rendering the giraffe susceptible to possible brain damage. The natural movement of the head from ground level to fully erect would result in blood moving away from the brain with gravitational force. The lack of blood perfusing the brain can cause fainting. The giraffe, however, suffers neither brain damage nor fainting. What adaptations do giraffes have to counteract these challenges? The aim of this study was to investigate the functionality of the rostral epidural rete mirabile situated just beneath the brain and its possible contribution to successful circulation in long-necked giraffes. The unique rostral epidural rete mirabile structure significantly contributes to counteract physiological challenges. Turns and bends characterize this structural arterial meshwork and subsequently an increased artery length through which blood flow must proceed before entrance into the brain, exerting resistance to blood racing to the brain when the head is lowered to the ground. The brain is supplied mainly by the maxillary artery through the carotid rete, with a rudimentary basilar artery not contributing to the brain’s blood supply. The resistance to blood flow due to the structure and position of the rostral epidural rete mirabile when the head is in the upright position is counteracted by the unique carotid-vertebral anastomosis allowing immediate cerebral blood supply. The rostral epidural rete mirabile structure in giraffes is an essential feature balancing physiological difficulties arising due to the extensive heart-to-head distance and might fulfill the same function in other long-necked artiodactyls.

Postural change intermittently between upright and head down in giraffes standing at a height of 4.5 meters is of physiological significance. The length of a giraffe’s neck denotes the flow of blood against the force of gravity, to supply the brain over a 2 m distance. The force of gravity also affects the flow of blood toward the brain, with a posture change from erect to ground level. How do these changes in stance not result in fainting when the head is raised and brain damage when the head is lowered? Giraffe has an advanced interconnection of the common carotid artery and the vertebral artery. The connection is located at the midpoint of the atlas, as indicated by means of computerized tomography and dissection. Duplex ultrasound with Doppler waveform examination showed the unidirectional movement of blood with movement from the vertebral artery into the common carotid artery when the head is erect. The direction of flow allows the provision of blood to the maxillary artery that feeds the rostral epidural rete that supplies to the brain. The flow direction in the carotid-vertebral connection changes when blood moves in the direction of the head along with the force of gravity, when the head is lowered. The rerouting of blood to move from the common carotid into the vertebral artery prevents brain damage. We have confirmed, by utilizing a CT scan, Doppler sonar, and dissection of latex-filled arteries, the existence and blood flow direction within the anastomotic artery associated with variation in posture in the giraffe.