Giraffe and okapi: Africa's forgotten megafauna

Le résumé fourni par la source

The Giraffidae family includes only two living species of ungulates: the giraffe (Giraffa camelopardalis) and the okapi (Okapia johnstoni), both restricted to the African continent. Taxonomically, the Giraffa and Okapia genera separated from each other approximately 16 million years ago (Hassanin et al., 2012), and they now exhibit as many differences as similarities. Today Okapia is represented by one species (Okapia johnstoni; Hart, 2013), though with surprisingly high genetic variation (Stanton et al., 2014), whereas nine subspecies of giraffe are currently recognized (although ongoing research is underway): Giraffa camelopardalis angolensis, G. c. antiquorum, G. c. camelopardalis, G. c. giraffa, G. c. peralta, G. c. reticulata, G. c. rothschildi, G. c. thornicrofti and G. c. tippelskirchi; Giraffe Conservation Foundation, 2013; Bock et al., 2014). At first sight, these two species look quite different, but they share a number of common features, including elongated necks and long, dark-coloured tongues (both adaptations for feeding on tree leaves), lobed canine teeth and skin-covered horns called ossicones (Bodmer & Rabb, 1992). With their unique coat pattern – squares for giraffe and stripes for okapi – both species are also individually identifiable, a very useful characteristic in ecological studies (see Halloran, Murdoch & Becker, 2015; for an example). While okapi are restricted to the dense, lowland rainforests of central and north-eastern Democratic Republic of Congo (DRC; although there have been historic and current reports of okapi in western Uganda, e.g. Kingdon, 1979), giraffe historically roamed the open savannahs encircling this region, across much of the rest of Africa. Giraffe now occur patchily in 21 countries, from Niger to Central and East Africa and down to southern Africa (Giraffe Conservation Foundation, 2013). Large herbivores, such as giraffe and okapi, play a central role in ecosystems, standing between plants and predators (Danell et al., 2006). Both species are vulnerable to predators, especially leopards for the okapi (Hart & Hart, 1988b) and lions for the giraffe (Hayward & Kerley, 2005). Like other large African ungulates, the giraffe is an agent of change in habitats and landscapes. It opens up areas and stimulates the growth of browsing forage for other species (Giraffe Conservation Foundation, 2013). The okapi is unique among the large mammals of the Ituri forest in having a diet composed solely of understory foliage (Hart & Hart, 1988a). Their role in the functioning of African ecosystems is one key reason to conserve giraffid populations in the wild, although dedicated studies are still needed for okapi. While the giraffe can boast more global fame, both giraffid species are internationally popular in zoos and are also emblematic of the ecosystems and countries in which they live. The giraffe is the national animal of Tanzania and may not be hunted in countries such as Botswana, Niger and Zambia as it is considered to be ‘royal’ (Giraffe Conservation Foundation, 2013). The okapi is a source of national pride for DRC, appearing on the banknotes of the Congolese franc and the logo of the national conservation agency, and has a World Heritage Site named after it, the Okapi Wildlife Reserve. Despite their iconic status, the giraffe and the okapi are relatively poorly studied and there is a general lack of knowledge on the key factors affecting their demographic rates. Until recently, neither species was considered threatened and relatively few studies had been conducted on their population dynamics and ecology (Quinn, Queslin & Kümpel, 2013; Bercovitch & Deacon, 2015). However, recent surveys and reviews have highlighted notable reductions in their geographical ranges and declines in their populations (Giraffe Conservation Foundation, 2013; Kümpel, Quinn & Grange, 2015). According to the Giraffe Conservation Foundation (2013), the number of giraffe in Africa has decreased by >43% since 1998, with less than 80,000 giraffes remaining today. Similarly, the okapi has probably experienced a 50% population decline over the last two decades (Kümpel, Quinn & Grange, 2015; Mallon et al., 2013). The main threats facing both giraffid species, to varying extents across their ranges, include habitat loss and degradation, human encroachment and settlement, poaching, war and civil unrest (Giraffe Conservation Foundation, 2013; Hart, 2013; Quinn et al., in press). Subpopulations of both species are becoming increasingly fragmented. In 2013, an IUCN Red List reassessment of the okapi was conducted, reclassifying it as ‘Endangered’ from ‘Near Threatened’ (Mallon et al., 2013). The giraffe as a species is currently only listed as ‘Least Concern’ on the IUCN Red List. However, two subspecies have been recently classified as ‘Endangered’: the West African giraffe (G. c. peralta; Fennessy & Brown, 2008) and the Rothschild's giraffe (G. c. rothschildi; Fennessy & Brenneman, 2010), and Red List reassessment of the remaining subspecies is underway and planned to be completed in 2015. In this special issue, recent ecological studies are presented, as well as updated information on the conservation status of giraffe and okapi in Africa. The paucity of information highlights the urgent need for additional ecological surveys, population monitoring and conservation of both these emblematic species to ensure their long-term persistence. Regarding this, a number of key issues relate both to the ecological characteristics of each species and to the political context within their range countries. For these individually recognizable species, remotely triggered camera traps can be used to monitor the elusive okapi (Nixon & Lusenge, 2008), which is otherwise hard to directly observe and uses unreliable dung-based survey methods, and photographic surveys can provide useful information on giraffe population size and demography (Suraud et al., 2012). Noninvasive genetic approaches have already demonstrated potential to study the distribution and reproductive behaviour of the okapi (Stanton et al., 2014, 2015) and giraffe (Fennessy et al., 2013; Bock et al., 2014), and could be explored further. Accepting that the popularity and profile of other flagship taxa such as elephant, rhino, big cats and great apes will continue to attract a disproportionate amount of conservation attention and funding, we should also collaborate for example to adapt monitoring of these other taxa to include giraffids as well. The socio-political situation is a major concern in many countries across these species' ranges, necessitating law enforcement on the ground in addition to locally supported, innovative conservation efforts. Given the relative security across much of their respective ranges and the accessibility and visibility of their respective habitats, the potential for tourism-based income and citizen science initiatives is clearly greater for giraffe than okapi. Critically, raising global awareness about the widespread threats to both giraffe and okapi is essential to generate funds and political support for projects on the ground. To this end, the IUCN SSC Giraffe and Okapi Specialist Group was established in March 2013 (www.giraffidsg.org). Its main objective is to increase understanding of giraffe and okapi, the threats they face, and how such threats can be mitigated to facilitate their long-term conservation and to play its part in ensuring the survival of these irreplaceable giraffid cousins.

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