Seasonal shifts in sociosexual behaviour and reproductive phenology in giraffe

First rangewide density estimate of the endemic and isolated Luangwa giraffe in Zambia

The Luangwa giraffe (Giraffa tippelskirchi thornicrofti), a subspecies of the Masai giraffe endemic to the Luangwa Valley of northeastern Zambia, inhabits an increasingly human-modified landscape. Accurate and current population estimates are critical to evaluating their status and identifying effective conservation strategies. However, sparse monitoring since the early 1900s has limited inferences about population size, structure, and range. To address this, we conducted the most spatially extensive and systematic survey to date of Luangwa giraffe across its distribution, extending survey effort 120 km south of their officially recognized extent. Using spatial capture recapture modeling, we estimated 651-890 giraffe and an overall density of 0.04-0.05 giraffe/km2. Density decreased to nought beyond 7.5 km from permanent rivers, consistent with preferred forage concentrated in riparian areas. Increasing giraffe density estimates up to a threshold of the Human Footprint Index suggested that limited human presence may have negligible consequences on movement and resource selection. This was likely due to suitable habitat and minimal conflict despite human presence. However, without mitigating land-use planning, rapid land conversion threatens human-giraffe coexistence. An even sex ratio and small proportion of subadults implied a stable population, but sex-biased and temporal dynamics in space use, impacts of predation, and stochastic risks necessitate continued monitoring. This study highlights the value of systematic large-scale monitoring and opportunities for data integration across long-term monitoring programs to evaluate factors driving Luangwa giraffe dynamics and to inform science-based conservation of this unique and isolated population.

Population genomics of the southern giraffe

Studying wildlife taxonomic diversity and identifying distinct populations has traditionally been largely based on morphology and geographic origin. More recently, this method has been supplemented by genetic data from the mitochondrial genome. However, this is limited as only maternally inherited and may not reflect the true nature of a population's genetics. Within the giraffe (Giraffa spp.), subspecies and unique populations were successfully characterized using both mitochondrial and genomic DNA studies, which led to new insights and, in some cases, unexpected results that required further verification. Here, we sequenced the genomes of 85 southern giraffe (G. giraffa) individuals from ten populations across southern Africa for a detailed investigation into the genetic diversity and history of its two subspecies, the Angolan (G. g. angolensis) and the South African (G. g. giraffa) giraffe. While the overall genotypes show low levels of runs of homozygosity compared to other mammals, the degree of heterozygosity is limited despite the large population size of South African giraffe. The nuclear genotype is largely congruent with the mitochondrial genotype. However, we have identified that the distribution of the Angolan giraffe is not as far east as indicated in an earlier mitochondrial DNA study. Botswana's Central Kalahari Game Reserve giraffe are unique, with a clear admixture of Angolan and South African giraffe populations. However, the enigmatic desert-dwelling giraffe of northwest Namibia is locally distinct from other Angolan giraffe yet exhibits intra-subspecies signs of admixture resulting from a recent introduction of individuals from Namibia's Etosha National Park. Whole genome sequencing is an invaluable and nearly indispensable tool for wildlife management to uncover genetic diversity that is undetectable through mitogenomic, geographical, and morphological means.