Reproductive endocrinology, morphological traits, and sexual selection in a population of wild South African giraffes.

Sex steroids are pervasive in mammals and evolutionarily conserved, but differences in the nuances of endocrine profiles characterize distinct species. Two sex steroids, testosterone and progesterone, feature prominently in the life history of mammalian taxa, but neither one has been analyzed from wild giraffes. Our study was designed to address this gap in knowledge by examining how these sex steroids are related to biological features and giraffe life history. We conducted the research at Rooipoort Nature Reserve a 44,000 ha private nature reserve in South Africa on a population of South African giraffes (Giraffa camelopardalis giraffa). Eleven adult giraffe cows and seven adult bulls were immobilized and various biological samples and morphological measurements were obtained. We analyzed both testosterone and progesterone using Ultra High Performance Liquid Chromotography - Tandem Mass Spectrometry (UHPLC-MS/MS). We found that non-pregnant females had lower progesterone concentrations than pregnant females and that those in the last trimester of pregnancy showed a slight drop in progesterone, as well as an increase in testosterone. Among males, chronological age was correlated with testicle size, testosterone concentrations, and ossicone volume. We propose that the progesterone decline functions partly to accelerate resumption of ovulation because giraffes become pregnant while lactating, and that the testosterone elevation provides an endocrine mileu for female defense of neonatal calves, given that lion predation is a major threat to calf survival. We suggest that male reproductive strategies are mediated by the age-related impacts of testosterone on growth in both body mass and ossicone volume as a consequence of sexual selection. We conclude by noting that the robust and solid ossicones of male giraffes function in mate competition as wedges that are used to topple opponents by raising their legs and placing them in an off-balanced position that can seriously injure them when falling to the ground.

A Preliminary Study on the Siphon Mechanism in Giraffe (Giraffa camelopardalis).

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.

Effective Field Immobilisation and Capture of Giraffe (Giraffa camelopardalis).

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.

Testicular disorder of sexual development with cryptorchidism, penile hypoplasia and hypospadias in a giraffe (Giraffa camelopardalis giraffa).

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.