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The regional population of Cape Vulture Gyps coprotheres is classified as Endangered, having satisfied criterion A2: an observed, estimated, inferred or suspected population size reduction of ≥50% over the last 48 years (three-generation period) where the reduction or its causes may not have ceased and may not be reversible.
The Cape Vulture has one of the most limited distributions of any Old World vulture species, being restricted to southern Africa and predominantly South Africa and Lesotho (Mundy et al. 1992). The regional population is divided into three primary ‘nodes', one each in the north-east (Limpopo, Mpumalanga, North West and Gauteng provinces), south-east (mainly in Lesotho and the KwaZulu-Natal and Eastern Cape provinces, extending marginally into adjacent parts of Free State Province and Swaziland) and south-west (Western Cape Province) of the region.
In the north-eastern node, there are breeding colonies in Limpopo, North West and Gauteng provinces (Benson et al. 1990, Benson 2004, Whittington-Jones et al. 2011), which are characteristically relatively few in number but are large in size, i.e. up to 1 000 pairs (Benson et al. 1990, Mundy et al. 1992). The species apparently no longer breeds in Mpumalanga Province (Herholdt et al. 1997).
Relevant to the south-eastern node, in Lesotho the species now breeds only in the highlands (Jilbert 1983, Donnay 1990, Maphisa 1997). In KwaZulu-Natal, breeding occurs mainly along the Drakensberg Escarpment and adjacent parts of the ‘Little Berg', although breeding is now largely restricted to the northern parts of this region (Brown and Piper 1988). Away from this area, the only remaining breeding localities in KwaZulu-Natal are a colony at Oribi Flats near Port Shepstone (Piper and Neethling 2002) and a site in the Greytown District that may only support a single remnant pair (SC Krüger, Ezemvelo KwaZulu-Natal Wildlife, unpubl. data). In Eastern Cape Province, the breeding range of the Cape Vulture has contracted to the eastern half of the province, largely within or adjacent to the former Transkei region (Boshoff and Vernon 1980, Boshoff et al. 2009). In contrast to the position in the north-eastern node, the breeding colonies in the south-eastern node are characteristically relatively many in number but are small in size, i.e. typically far fewer than 200 pairs (Mundy et al. 1992). The species no longer breeds in Free State Province and the single possible remnant colony mentioned by Colahan (2004) as present in 1983 is no longer active (DG Allan unpubl. data).
The south-western node in Western Cape Province now encompasses only a single, fairly small and highly isolated breeding colony: Potberg , which supported 69 pairs in 2012 (Boshoff and Vernon 1980, Shaw 2004).
Outside the region, the species also occurs in Mozambique, Zimbabwe, Botswana and Namibia, and is a vagrant to Angola and Zambia (Mundy et al. 1997, Parker 1999, Bamford et al. 2007). Outside the region, it only breeds in Botswana (Borello and Borello 2002) and Mozambique, although the most recent published account of breeding at the single (and small) colony in the latter country dates to July 2002, when six incubating adults were observed (Monadjem 2003). The Cape Vulture is now extinct as a breeding species in Namibia (Simmons 2002) and does not currently breed at the single locality where they have bred in the past in Zimbabwe (Mundy 1997, Mundy et al. 1997).
The most comprehensive estimate of the Cape Vulture's population size is that contained in the unpublished PhD thesis of Piper (1994) who estimated the global population at about 12 000 birds and 4 400 breeding pairs (i.e. 8 800 mature individuals). Of these, about 11 000 birds and 4 050 pairs (8 100 mature individuals) were claimed for the region (South Africa, Lesotho and Swaziland). Piper (2004a, 2004b, 2005), however, presented revised global population estimates, for the years 2000 (in the first instance) and 2003 (in the second and third instances), of 8 000, 10 000 and 8 000 birds, and 3 000+ (in the first two instances) and 3 000 breeding pairs, respectively, but without presenting supporting details. Piper (2004a) suggested that the breeding population had decreased by about 15% between 1980 and 2000, i.e. -0.79% per year, but again without providing supporting details. A 2013 update of the global estimate of the current number of breeding pairs provides very similar, but marginally larger, numbers to those of Piper: 4 700 pairs (9 400 mature individuals) of which 4 400 pairs (8 800 mature individuals) occur in the region (BirdLife South Africa in prep.). The north-eastern node supports c. 56% of the regional breeding pairs, the south-eastern node 42% and the south-western node 2%. The regional population is estimated at 8 800 mature individuals. Confidence in this population estimate is high.
Comprehensive, regular, long-term monitoring of the total number of breeding pairs (i.e. mature individuals) at each and every Cape Vulture breeding colony in the region has not been achieved so far and would be logistically challenging. Therefore the most feasible way to estimate the trend in Cape Vulture numbers would be to examine information from the relatively few breeding colonies monitored on a regular basis over an adequate time period (i.e. over three generations or 48 years; see below).
Unfortunately, only three Cape Vulture colonies have accurate count information extending this far back in time, i.e. to about the mid-1960's, and all three are small to medium-sized colonies. Potberg (Western Cape) supported 32 pairs in 1965 and 69 in 2012, Aasvoelberg (near Zastron, Free State) had 41 pairs in 1965 but is now extinct as a breeding site, and Wilge River (Mpumalanga) had 12 pairs in 1962 but breeding also no longer occurs there (BirdLife South Africa in prep.).
A much larger sample of breeding colonies, 32 in total, was known in the 1960s, but accurate count information from this early time period is not available for these (BirdLife South Africa in prep.). The provinces in which these additional sites are located are as follows (from north to south): Limpopo - 2 (extant), Mpumalanga - 1 (extinct), North West - 2 (one extant), Gauteng - 1 (extant), Free State - 2 (extinct), KwaZulu-Natal - 1 (extinct) and Eastern Cape - 23 (seven extant). Of these 32 localities, only 11 still support breeding pairs today.
Taken together, this information from the total of 35 Cape Vulture breeding colonies known in the 1960's, suggests a 66% decrease in the number of colonies between that time period and currently, i.e. over three generations, and may infer a similar reduction in the total number of mature individuals. It should also be noted that Colahan and Esterhuizen (1997) document at least 32 breeding colonies as present in the Free State ‘around 1960', all now extinct. If this information is integrated with that above, the total regional number of known colonies in the 1960's rises to 64 of which 12 are extant (none in the Free State), i.e. an 81% reduction in colonies, and, by inference, the total number of mature individuals. This estimate is heavily biased towards colonies in Free State, where the species has undergone a particularly severe decrease and likely not representative of the entire regional range as a whole. However in the absence of suitable baseline data, it is suspected from the available data that the decrease in the regional population has been greater than 50% over a 48 year period. Confidence in this regional population trend estimate is medium.
The primary threats to the Cape Vulture are from contamination (and perhaps shortage) of their food supply, negative interactions with human infrastructure and their demand for use in the traditional health industry. Threats reducing adult survival, as is the case relevant to many of the dangers discussed below, are of particular concern, as the population stability of this species, which evidences a naturally low reproductive rate, likely depends on high adult survival rates.
Poisoning as a major threat to the Cape Vulture has been recognised for decades (Boshoff and Vernon 1980, Benson 2000, Verdoorn 2004). Documented instances and discussion of the problem in the literature is legion as is the list of poisons used and, despite exhaustive efforts to publicise and counteract this, Cape Vultures continue to be poisoned in large numbers and on a regular basis (McKean 2004). The wide-ranging and communal foraging behaviour of Cape Vultures means that a tiny minority of humans employing poisons, operating at only a local scale, have the potential to significantly impact a large proportion of the regional vulture population (Boshoff and Vernon 1980).
Poisoning appears mainly incidental and a byproduct of targeting mammalian predators. The use of most of these poisons is illegal, as is the lacing of large carcasses with any poison. Some of these poisons have now been outlawed and removed from the marketplace but extensive stockpiles likely exist in some quarters (Boshoff and Currie 1981, Scott 1994, Wysoke et al. 1994, Scott 1997a, Verdoorn 1997b, Scott 1997c, Shaw 2004, Naidoo et al. 2011). Sub-lethal doses of poisoning can cause mortality through birds perched on cliffs suffering seizures and falling from the ledges (Benson 2000). Nestlings are known to have been poisoned by their parents feeding them poisoned meat (Benson 2000).
Poisoning can also be intentional and targeted specifically at vultures if the birds are perceived as a threat to livestock, purveyors of disease and plagues, or related to some nuisance factor (Boshoff and Vernon 1979, 1980, Mundy 1983, Boshoff 1989, Pringle 1990, Mundy et al. 1992, Snyman and Snyman 1997, Scott 1997a, Anderson 2000f). Lead poisoning through ingesting lead bullets and bullet fragments in carcasses is a further potential threat (Boshoff et al. 2009) and one that has been confirmed in other vulture species (Adaudi et al. 1990, Mateo et al. 1997, Platt et al. 1999, Miller et al. 2000, Clark and Scheuhammer 2003, Mateo et al. 2003, Garcia-Fernandez et al. 2005, Pattee et al. 2006).
Electrocution by electrical infrastructure is another major source of mortality and this threat dates back to at least 1948 (Markus 1972, Ledger and Annegarn 1981, van Rooyen 2000, Kruger et al. 2004). An additional major threat emanating from electrical infrastructure is collisions with overhead lines by flying vultures (Naidoo et al. 2011). Collisions with other types of overhead lines are another problem (Benson and Dobbs 1984, Benson 2000, 2004). Cape Vultures also sporadically collide with fences, including at supplementary feeding sites (Benson and Dobbs 1984; Piper 2004a). Alongside nonsteroidal anti-inflammatory drugs (NSAIs), wind farms rank prominently among potentially major threats to the Cape Vulture (Rushworth and Krüger 2013). The harvesting of vultures for the traditional medicine is a widespread practice and could materially contribute to hastening extinction (Mundy 1983, Beilis and Esterhuizen 2006, Mander et al. 2007, McKean et al. 2013).
Food shortage is widely cited as a major threat (Boshoff and Vernon 1980, Benson 1997, Maphisa 1997, Benson 2000, Benson et al. 2004) but direct evidence on this point is sparse. Past decreases in the numbers of Cape Vultures have also been related to the eradication of the ancestral game herds in the region (Boshoff and Vernon 1980). It has been demonstrated that dense tree cover can retard the location and access of carcasses by Cape Vultures and that bush encroachment therefore could potentially pose an indirect threat to the species (Schultz 2007, Bamford et al. 2009).
Another cause of mortality in Cape Vultures is drowning in circular, concrete farm reservoirs, particularly in the drier western parts of the region (Anderson et al. 1999). Disturbance of Cape Vultures at their cliff nesting colonies can potentially result in lower breeding success and even complete desertion of such sites (Benson and Dobbs 1985, Verdoorn 1992, Borello and Borello 2002). Aircraft flying in close proximity to colonies; including micro-light aircraft and hang-gliders, constitutes another potential source of disturbance (Robertson 1989, Verdoorn 1997a, Scott 1997b) but the significance of this requires confirmation.
Fires at breeding colonies may (Ledger and Mundy 1975) or may not (Verdoorn and Becker 1992, Scott 1997b) present a danger to breeding birds but is likely to be a fairly minor threat as these rarely (if ever) reach actual nest sites. Anthropogenically driven climate change, essentially increased ambient temperatures, has been proposed as a potential threat to the Cape Vulture (Simmons and Jenkins 2007).
The Vulture Study Group, established in 1977 and with an African, and mainly southern Africa, focus, was largely formed on the basis of concern for the survival of the Cape Vulture (Mundy et al. 1992). This group is now essentially subsumed into the broader Bird of Prey Programme of the Endangered Wildlife Trust with the work on this species synchronised by a Cape Vulture Task Force formed in 2006. VulPro is involved directly in several vulture conservation initiatives, with the Cape Vulture as the organisation's primary focal species. Ezemvelo KwaZulu-Natal Wildlife, the provincial nature conservation authority in that province, initiated a Cliff-nesting Vulture Survey project in 2000.
A recently established global organisation is the IUCN Vulture Specialist Group formed in 2011. Vulture News, a journal dedicated to publishing information on vulture research and conservation efforts and which was initiated in 1979 by the Vulture Study Group, is now the journal of the IUCN Vulture Specialist Group.
Ezemvelo KwaZulu-Natal Wildlife initiated annual Vulture Count Days on International Vulture Awareness Day from 2003. A workshop in 2006 resulted in a formal conservation plan for the Cape Vulture (Boshoff and Anderson 2006) with goal of stabilising the Cape Vulture population. Reviews to this plan were made in 2010 and 2012. Conservation plans for the species have also been produced for the Western Cape Province, essentially covering the Potberg colony (Boshoff and Robertson 1985; Scott 1997). A vulture conservation strategy for KwaZulu-Natal covering the 5-year period 2008-2012 and including the Cape Vulture has been produced (Rushworth 2008).
A ‘Poison Working Group' of the Endangered Wildlife Trust, established in 1991 and subsequently subsumed into a Wildlife Conflict Prevention Programme, worked to combat poisoning in the Cape Vulture (Verdoorn 1997). Unfortunately this group became defunct in 2012 due to funding shortages. The Wildlife and Energy Programme of the Endangered Wildlife Trust is targeted at minimising the risk to wildlife posed by energy and communications infrastructure, including the dangers to large birds such as the Cape Vulture stemming from electrocution by, and collisions with, such infrastructure (van Rooyen and Piper 1997, Jenkins et al. 2010). Both BirdLife South Africa and the Endangered Wildlife Trust are active in bird conservation issues related to the fledgling wind-energy industry in the region, largely co-ordinated through a Bird and Wind Energy Specialist Group which the two organisations co-chair. The rescue, rehabilitation and release by recognised rehabilitation facilities of vultures temporarily incapacitated by the various threats faced by the species is an increasingly important conservation measure (Snyman and Snyman 1997, Verdoorn et al. 1997, Verrynne 1997, Naidoo et al. 2011, Monadjem et al. 2013). Key facilities recently involved in such rehabilitation work include VulPro (North West Province), De Wildt Cheetah and Wildlife Trust (Gauteng), National Zoological Gardens of South Africa (Gauteng) and the African Bird of Prey Sanctuary (KwaZulu-Natal).
Similar to the position relevant to research questions, the proceedings of the vulture research and conservation workshop held in 1997 (Boshoff et al. 1997) also identify a wide range of direct conservation actions and priorities pertaining to vultures, including the Cape Vulture, many of which remain equally relevant. These include addressing the threats stemming from poisoning, energy-related infrastructure, the traditional health industry, food shortages, drowning, disturbance, and negative perceptions and ignorance. The proceedings also call for intensified monitoring of Cape Vulture breeding colonies and roosts.
The proceedings from a follow-up workshop in 2004 (Monadjem et al. 2004) contain a concluding paper (Boshoff 2004) reviewing progress on conservation research and action since the 1997 workshop. This paper, as well as Boshoff and Anderson (2006) laments the lack of overarching and strategic planning, and the absence of priority setting, relevant to vulture conservation and research initiatives, including those applying to the Cape Vulture. The ‘Site Register', initiated by the Vulture Study Group, is currently curated by the Birds of Prey Programme and this information, especially that related to breeding sites, should be integrated with other similar unpublished and published data, and be published as a comprehensive monograph as a matter of high priority.
The scourge of poisoning needs to be combatted by the rigorous investigation and prosecution of all such instances, as well as the maintenance of ongoing and high-profile education and publicity campaigns emphasising the causes and consequences of such incidents. The legal penalties need to be severe enough to act as material deterrents. A move to lead-free ammunition should be considered where relevant. Careful monitoring of the potential use of diclofenac, and other non-steroidal anti-inflammatory drugs (NSAIs) lethal to Gyps vultures, is required.
Additional effort is required to reduce electrocutions and collisions of Cape Vultures with power-line infrastructure (Boshoff and Michael 2009, Boshoff et al. 2011). Existing pylons and overhead lines need to be replaced or retro-fitted, on a carefully prioritised basis, and new infrastructure needs to designed and routed, to minimise the risks from electrocution and collisions. Particular care will be required in the immediate future, as wind farms spread across the region's landscapes, to ensure that this industry does not pose a significant threat to the Cape Vulture.
Relevant to the trade in Cape Vulture body parts in the traditional health industry, Mander et al. (2007) call for an intervention strategy to be developed that addresses the following primary areas of action: a) reduce consumption/demand for vultures through an awareness-building campaign targeting public consumers and current roleplayers in the trade; b) change/create policy to improve regulation of the vulture trade; c) improve policing and enforcement for better regulation of the vulture trade; d) improve understanding of the vulture trade to allow more focused interventions, including research and monitoring of the use and trade of vultures.
Firm steps must be maintained to confirm that the food provided at ‘vulture restaurants' is free from toxins harmful to the birds. Similar ongoing action is required to control the dangers from human disturbance at colonies. Finally, the compilation of a Biodiversity Management Plan covering the species, as envisioned by the National Environmental Management: Biodiversity Act, 2004 (Act No. 10 of 2004), is an urgent priority (Webster 2012).
* Regular, accurate, ongoing censuses of all large breeding colonies, and as many of the smaller ones as feasible, is a high priority. A Cape Vulture breeding colony conservation and monitoring protocol document exists outlining colony-census methodology (Wolter et al. 2011).
* Ringing, wing-tagging and tracking using satellite- and GSM-tracking devices can greatly facilitate the gathering of information on vulture mortalities. Information on live vultures found incapacitated, especially those taken to rehabilitation centres, is also invaluable with respect to factors involved in mortalities (Monadjem et al. 2013).
* In-depth knowledge of the movement patterns of Cape Vultures is indispensable for the conservation of the species. Following on from early radio-tracking investigations (Boshoff et al. 1984, Benson 2004), recent advances in tracking technologies, i.e. satellite and GSM tracking, are revolutionising this sphere of investigation (Diekmann et al. 2004, Bamford et al. 2007, Bartels et al. 2007).
* New studies are urgently required examining the spatial and temporal patterns and trends in the availability of carrion within the core range of the Cape Vulture.
* The issue of potential lead poisoning through bullets lodged in carcasses requires urgent investigation.
* Further investigation of the potential toxicity of non-steroidal anti-inflammatory drugs, and other pharmaceutical drugs used in the veterinary industry, is necessary.
* Relevant to collisions, additional research is required to understand factors associated with the highest risks in the regard and the efficacy of line-marking devices.
* The issue of potential food shortage requires investigation, especially as relevant to the necessity for the establishment of supplementary feeding stations.