Giraffes that people are translocating for conservation purposes should be moved in groups of at least 30 females and 3 males to ensure long-term population success, researchers say.
In two new studies, researchers identify the ideal composition of a group to be moved and offer guidelines for all aspects of the translocation process. That includes decision-making and planning, transportation, monitoring of animals, and evaluation of success.
Giraffe populations declined 40% between 1985 and 2015, according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, leading the group to classify giraffes as vulnerable—likely to become endangered unless circumstances change—and some subspecies as endangered—likely to become extinct in the immediate future.
“Translocations have been used as a conservation strategy to establish new populations, augment small or declining populations, or re-introduce the species to previously occupied areas,” says Derek E. Lee, associate research professor of biology at Penn State and leader of the research team.
“Translocations could be an important conservation tool for giraffes, but until now, there has been little guidance about how best to plan, implement, or report them.”
Long-term giraffe success
As reported in Endangered Species Research , researchers used a modeling technique called a population viability analysis to determine the ideal size and sex distribution of a newly established population.
They simulated a variety of scenarios to project long-term viability and genetic diversity—which can buffer a population against disease and environmental change—of founding populations.
The researchers deemed a translocation scenario a success if there was a 95% probability that the population continued for 100 years while maintaining most of the original genetic diversity.
A founding population of 30 females and 3 males results in long-term population viability, but to maintain more than 95% of the genetic diversity of the source population, researchers recommend groups of 50 females and 5 males.
More females are required than males, because females, unlike males, provide care to young and are an important element of giraffe social structure.
“Small numbers of founders with fewer than 10 females can appear to be successful in the first decades due to short-term population growth, but are not successful in the long-term,” says Lee.
“Small groups can suffer from inbreeding depression, and they are more likely to lose genetic diversity due to random events in the first years after translocation.”
Because giraffes are physically difficult to move, experts usually translocate them as juveniles, which have higher rates of mortality than adults. A larger founding population can also buffer against the loss of young individuals.
“Most giraffe translocations in the past have moved too few animals to ensure the successful establishment of new population,” Lee says. “Our recommendation of 30 to 50 females should greatly increase the success rate of future translocations that adhere to these rules.”
A second paper in the African Journal of Ecology offers additional guidelines about the translocation process.
Researchers reviewed documented cases of giraffe translocation and considered published accounts of giraffe biology and ecology as well as their personal experience.
The researchers describe how to set translocation goals and assess risk, including to the moved giraffes, the source population, and to other species—including humans—in the area of introduction.
“Ongoing monitoring of the translocated population, adaptive management of the population, and documentation of the entire translocation process are also crucial, both for long-term success of the population and to improve future efforts,” Lee says.
Additional coauthors are from the European Association of Zoos and Aquaria, the University of East Anglia, the University of Bristol, the Wild Nature Institute, Elephant Connection in Zambia, and the University of the Free State in South Africa.
Source: Penn State