Editor, Earth News
A bit special: A lone adult male
Fleeting sightings of the world's rarest antelope, the hirola, in a new safe haven are cases of mistaken identity, a survey has found.
That has dashed hopes that some of the last hirola have managed to colonise a new territory where they would be less vulnerable to flooding and hunting.
Fewer than 600 wild hirola remain, confined to a small area in Kenya.
It is sometimes called a 'living fossil', being the sole survivor of a once diverse group of antelope species.
Prior to 1970, an estimated 14,000 hirola existed in the wild.
But the antelope soon came under a host of pressures which led to a dramatic decline in its population over the next 30 years.
Hunting and predation killed many, while the animals' range became restricted by habitat loss and an increase in human settlements and farms rearing livestock.
That left few animals surviving in a small area along the border between the River Tana in Kenya and the River Juba in Somalia.
The Somalia population is already thought to be extinct, while in Kenya the antelope survives in pockets within the Ijara, Garissa, Tana River and Lamu districts, while two small groups of animals translocated to the Tsavo East National park and are struggling to establish there.
However, in the 1990s two new threats emerged.
The collapse of the Republic of Somalia in 1991 precipitated a massive influx of refugees into Kenya.
"The majority of the Somali refugees were resettled in Garissa district which is part of the hirola's natural range," says Yakub Dahiye of the National Museums of Kenya in Nairobi. "The presence of large numbers of refugees increased poaching activities and general insecurity of the area."
In 1997 significant flooding caused by the El Nino weather phenomenon covered the region.
In response to both, many large mammals including the hirola migrated either to higher or quieter areas.
An emancipated group of hirola in the Ijara district of Kenya
Then conservationists started receiving exciting reports of hirola in northern Garissa, an area outside of the antelope's known historical range, suggesting that the antelope was migrating to safer territory. Previously, the antelope was confined to the southern part of the district.
So to check the authenticity of the reports, Dahiye performed an extensive survey of the region.
For six days, he travelled more than 1100km criss-crossing the northern Garissa, observing and recording from the top of a moving vehicle the identity and locations of wildlife in the area. He also showed pictures of hirola to local people, asking if any had seen the elusive antelope in recent years.
None had, and despite spotting giraffe, Grant's gazelles, gerenuk, lesser kudu and oryx, Dahiye did not see a single hirola, he reports in the African Journal of Ecology.
"That confirms that the species is endemic to a small area between the lower River Tana in Kenya and the lower River Juba in Somalia," he says.
"If this small natural habitat is destroyed, then we will not have an in situ hirola population."
Effective management plans for the species are still lacking, says Dahiye.
Back in 1974, the Arawale National Reserve was set up mainly to conserve the hirola, but the reserve was later abandoned.
Local communities in Ijara district have now responded by establishing a Community Conservation Area to help protect those animals living there, but wider, strategic plans have yet to be put in place to conserve the species, Dahiye says.
The hirola is special because of both its rarity and evolutionary uniqueness.
Scientifically named (Beatragus hunteri), the hirola belongs to the family Bovidae, the group that includes all antelopes, cattle, bison, buffalo, goats and sheep.
Within that group, it belong to the subfamily Alcelaphinae, meaning it is most closely related to topi, wildebeests and hartbeest antelopes.
But what makes the hirola stand out is that it is the last living representative of the genus Beatragus.
A female hirola killed by a leopard
The International Union for the Conservation of Nature considers it to be the most at risk antelope species, listing it as Critically Endangered, while the Zoological Society of London includes the hirola within its EDGE programme, which seeks to conserve the most evolutionary distinct and globally endangered of all animals.
Dahiye thinks that the unconfirmed sightings of the hirola in northern Garrisa, which sparked much excitement among conservationists, were cases of mistaken identity.
Local people call both hirola and impala antelopes by the same name in Somali, while the two species also look similar, he says.