The Masai giraffe, found only in Tanzania and Kenya, may be more endangered than previously thought.Credit: Royalty-Free/Corbis
The Masai giraffe, found only in Tanzania and Kenya, may be more endangered than previously thought, according to new research in the journal Ecology and Evolution.
The International Union for Conservation of Nature (IUCN) declared Masai giraffes an endangered species in 2015 after their number fell by 50% to 35,000 in a period of just 30 years. Populations of Masai giraffe, separated by the steep cliffs of the Great Rift Valley and by human settlements blocking their migration corridors, have not interbred in more than 1000 years.
This has split the giraffe into two populations, one west and another east of the Great Rift Escarpment (GRE). The few remaining natural corridors through the GRE are occupied by humans, limiting east-west animal dispersal and gene flow, explains lead author Douglas Cavener, Dorothy Foehr Huck and J.Lloyd Chair in Evolutionary Genetics at Pennsylvania State University.
To assess the impact of the GRE on Masai giraffe gene flow, the team sequenced the nuclear and mitochondrial DNA (mtDNA) to show evidence of gene variations across the two populations. They established that females have not migrated across the GRE between populations in the Serengeti and Tangier ecosystems in the past 289,000 years.Further DNA analysis showed that male gene flow across the GRE occurred more recently, but stopped a few thousand years ago.
“Each population has less genetic diversity than if they were one larger interconnected population,” Cavener observes.“There are very few prospects of giraffes crossing over the GRE on their own, because they’re naturally poor climbers and translocating giraffes would be impractical—making the Masai giraffe more endangered than previously thought,” the researchers note.
“Masai giraffes appear to have rarely traversed the GRE over their evolutionary history, and it is impractical to develop wildlife corridors across the escarpment that could be used by giraffes to genetically reconnect western and eastern populations,” Cavener explains.
“Conservation efforts should be focused on maintaining and developing corridors within the separate populations,” he adds.The researchers also found a disturbing inbreeding trend within the distinct giraffe populations in both east and west side of the rift which could exacerbate lack of genetic diversity and compromise overall fitness of the entire population.
“There’s need for further research into the giraffe populations on both sides of the rift, especially the more isolated ones to further establish risks posed by the inbreeding trends,” the researchers say. Peter Kasinigi, wildlife conservationist from Shompole Conservancy in Kajiado, Kenya, at the southern border with Tanzania, says giraffe populations are also threatened by other factors. “The threat of climate change cannot be taken lightly,�� he says, adding that recent episodes of drought have killed hundreds of giraffes in his area, while illegal hunting and poaching of wildlife must also be addressed.
