Giraffe translocation population viability analysis

Most populations of giraffes have declined in recent decades, leading to the recent IUCN decision to upgrade the species to Vulnerable status, and some subspecies to Endangered. Translocations have been used as a conservation tool to re-introduce giraffes to previously occupied areas or establish new populations, but guidelines for founding populations are lacking. To provide general guidelines for translocation projects regarding feasibility, we simulated various scenarios of translocated giraffe populations to identify viable age and sex distributions of founding populations using population viability analysis (PVA) implemented in Vortex software. We explored the parameter space for demography and the genetic load, examining how variation in founding numbers and sex ratios affected 100 yr probability of population extinction and genetic diversity. We found that even very small numbers of founders (N ≤ 10 females) can appear to be successful in the first decades due to transient positive population growth, but with moderate population growth rate and moderate genetic load, long-term population viability (probability of extinction 95% genetic diversity of the source population in an isolated population, 50 females and 5 males are recommended to compose the founding population. Sensitivity analyses revealed first-year survival and reproductive rate were the simulation parameters with the greatest proportional influence on probability of extinction and genetic diversity. These simulations highlight important considerations for translocation success and data gaps including true genetic load in wild giraffe populations

Relationships between male giraffes’ colour, age and sociability

In species in which males signal competitive ability through secondary sexual traits, males with different levels of trait expression may adopt different reproductive tactics to maximize their reproductive success. In fission–fusion social systems, the most dominant males often roam widely in search of females in oestrus, and thus exhibit different patterns of sociability from subordinate males that utilize alternative reproductive tactics. Giraffes, Giraffa camelopardalis, are rare among mammals in that they are sexually dimorphic in colour, and colour is hypothesized to function as a signal of males’ social status by displaying their competitive ability. Here we analysed the coat colour and sociability of 66 wild male giraffes over 12 years at Etosha National Park in Namibia to test two premises underlying this hypothesis. First, we found that males did not all darken at the same rate or to the same degree, and colour variation increased with age. This suggests that colour is not solely an age-based trait but could be a secondary sexual trait. We then showed a distinct difference in the sociability of both young and pale males compared to darker males. Both younger and paler old males tended to be more gregarious while darker males were more solitary. This is consistent with a system where darker, more dominant males roam looking for females in oestrus. Younger or subordinate males may delay roaming or use an alternative tactic, such as remaining in groups with females to gain copulations when a more dominant male is not present. Our results are consistent with the hypothesis that male giraffe coat colour functions as a signal of social status through competitive ability, but deeper study into movement patterns and the costs and benefits associated with darker colours is required

Development of 11 microsatellite markers for Giraffa camelopardalis through 454 pyrosequencing, with primer options for an additional 458 microsatellites

Many wild giraffe populations are declining across Africa, with two subspecies listed by the IUCN as Endangered in the past 4 years. We developed 11 microsatellite markers from Giraffa camelopardalis angolensis in Etosha National Park, Namibia using 454 sequencing. In 70 individuals, the loci showed 2-4 alleles per locus and expected heterozygosities of 0. 082-0. 711. There were no significant deviations from Hardy-Weinberg equilibrium for any of the loci. Null allele frequencies were low