World's rarest giraffe species clinging on in West Africa.03/04/2007 00:00:00
February 2007. The giraffe of Niger are the last in all West Africa, and they are highly threatened. They are both genetically and ecologically distinct from other giraffe and are therefore an important biodiversity remnant. Limited research has provided a snapshot of what has happened to the population’s numbers and distribution over the past decade.
Currently, the population is increasing and genetically healthy, however, its range has been significantly reduced and habitat loss and fragmentation continues to be a major threat. The carrying capacity of giraffe within its current range is unknown, although naturally the population does require seasonal habitats and forage across habitat types.
Standardised yearly monitoring has been established and the programs ongoing success is imperative. Ecological research on the giraffe and their habitat is critically important, however, greater collaboration and integration of efforts between government and non-government organizations, coupled with appropriate community based natural resource management, is the key to the survival of these last giraffe in West Africa.
The Niger giraffes are unique. The population is critical as the last representative of giraffes evolutionary heritage west of Cameroon, which historically ranged over vast areas in the region. The giraffe population of Niger are an important incubator of giraffe history and as a distinct subspecies that is genetically healthy, represent a unique biological resource. They form a distinct branch (evolutionary lineage) from other giraffe populations, having split from a common ancestral population approximately 350,000 years ago (based on mitochondrial and nuclear DNA research). The Rothschild’s giraffe G. c. rothschildi, whose current range lies within Uganda and Kenya, are identified as their closest relative.
Reduction in giraffe range and habitat availability has occurred throughout Africa, and the West African population has suffered considerably from these direct and other indirect actions. The current extant range of the giraffe population in Niger is restricted, with few exceptions to the south-east of Niger.
The most recent assessment of the giraffe population in Niger identified 135 individuals (2005 survey; 142 in 2006 unpublished). The population has increased markedly since first surveyed in 1994 (67 individuals). Over the past decade the population has undergone considerable change, with an initial decline attributed to poaching and capture/translocation, and a subsequent increase stemming from targeted on ground conservation programs, as well as immigration of individuals from isolated or small meta-populations.
The population is currently not stable, and the carrying capacity of their current range is unknown. Population growth over the past decade equates to 7.7% per annum (this is highly variable), and since 2002, <6%. The high rate of increase for giraffe in Niger can possibly be attributed to the lack of natural predators; however, it is highly variable.
The population is currently female dominated [male:female (1:1.41)], although this has varied greatly over the past decade, enabling a potentially positive reproductive capacity (at least in the short- to medium term) with respect to population growth.
The population continues to show good reproductive capacity, despite historical and current risks and threats. In some areas of their extant range, only one fifth of all giraffe reach sexual maturity, a result of a combination of factors, including predators.
The density of the giraffe population in Niger is extremely low (0.01 km2), one of the lowest in Africa. The low densities are directly correlated with the population’s low numbers and the extensive range required fulfilling their biological requirements. This low density does not highlight the importance of key areas, i.e. Kouré, Fandou and the Dallol Bosso, as supporting markedly higher densities of giraffe, and the reliance on these areas year round for the majority of the population. Arid conditions, ‘competition’ for habitat with an expanding human population, large seasonal rainfall variability, shifts in surface water availability and core forage resources contribute to the low giraffe densities and potentially a lower population carrying capacity in Niger.
There are three major areas in the giraffe’s range (commonly referred to as the zone): Fakara Plateau (Kouré, Fandou), Harikanassou (Dallol Bosso) and Intermediate zone. Giraffe appear to range, and increasingly so, between all three areas, predominantly associated with seasonal availability of forage. The seasonal movements of giraffe correspond with local human activities, which have led some to describe this as a form of synchronisation; aggregating in the rainy season on the Kouré Plateau, and expanding more into the Fandou Plateau, attributed to the relatively dense forage availability and increased primary productivity of the ‘Tiger Bush’. New leaves and shoots are available, correlating with more favourable chemical quality of preferred species i.e. increased protein and water content, and reduced fibre. During the dry season giraffe return to the Dallol’s where the vegetation is sparser but species such as Faidherbia albida (formerly Acacia albida) provides essential seasonal forage in the form of new leaves and pods. As mentioned above, an intermediate zone, the area between the rainy and dry season habitats, is an important zone of transition for the giraffe as they seasonally migrate.
A parallel between environmental conditions, densities and range of giraffe is evident. In arid Niger, giraffe have lower densities, larger home range sizes, less stable herds and increased mobility. The average home ranges of giraffe in Niger was the largest for any population in Africa, males 842 km2 and females 367 km2; maximum home range up to 1564 km2 and 1378 km2, respectively (late 1990s). The need for such a large home range often correlates with the population’s increased biological and ecological requirements e.g. forage, mates, space, competition, conflict, etc., and thus a need to range further a field.
An array of threats faces the conservation and survival of the giraffe in Niger. These threats range in both size and complexity, however, habitat loss, degradation and fragmentation are the major threat critical to the giraffe’s to the long-term conservation of the species in Niger. As an example, the significant loss of available tiger bush over the past 30 years, coupled with an increase in human agriculture and pastoralist activities in these areas. Epidemiological risks are not considered high in comparison to human pressures.
The majority of threats arise from conflict and competition (direct, indirect or perceived) for resources with humans and their domestic stock. Ongoing monitoring and management from government and non-government organisations alike is required to both better understand the current or potential threats, and mechanisms to abate or remove them.
Courtesy of the Dr Julian Fennessy, International Giraffe Working Group (IGWG). Click here to email Dr Fennessy.