Africa has been inhabited by humans for over 300 000 years (Fisher et al. 2013; Sheehan & Sanderson 2012). Within that time, communal grazing of livestock, human-induced fires, depletion of indigenous forests and urbanisation have altered many landscapes (Lawes, Griffiths & Boudreau 2007; Sheehan & Sanderson 2012; Skead 1987; Vetter & Bond 2012). Although heavily human-altered landscapes are often degraded, endangered species can persist in these environments (McKee et al. 2004; Phipps et al. 2013b).

One opportunistic animal guild that has coexisted with humans for centuries is the vulture (Haas & Mundy 2013; Moleón et al. 2014). Vultures perform an important ecosystem service by consuming carcasses. Vultures recycle nutrients, reduce the potential for the spread of infectious diseases, and provide a carbon-neutral waste removal service (Dupont et al. 2012; Prakash et al. 2003; Ogada et al. 2012b). In some cultures, vultures are highly revered and, for example, are used to ritually dispose of human corpses (Haas & Mundy 2013). However, 61% of vulture species worldwide are vulnerable to extinction from a variety of threats (Ogada et al. 2012a). Understanding how vultures persist in human-altered landscapes will provide information on where and how to focus conservation efforts on a regional and global scale.

The Cape Vulture (Gyps coprotheres), a colonial nesting scavenger, is endemic to southern Africa. It is listed as ‘vulnerable’ on the Red List of Threatened Species of the International Union for Conservation of Nature and Natural Resources (IUCN) and as ‘endangered’ in the Eskom Red Data Book of Birds of South Africa, Lesotho and Swaziland (BirdLife International 2013).

At least 20% of the global population breeds in the former Bantustan homeland of the Transkei in the Eastern Cape province of South Africa (BirdLife International 2013; Boshoff, Piper & Michael 2009; Piper 1994). This area was created under segregation laws of the former apartheid government of South Africa and is characterised by high human densities and subsistence farmland (Kepe 1997; Shackleton et al. 1991; Statistics South Africa 2011). In this area, every resident has access to communal grazing land and livestock numbers are not restricted (Vetter & Bond 2012).

Most of the Cape Vulture breeding colonies in the former Transkei are located in formal protected areas or Important Bird Areas (IBAs) (BirdLife South Africa 2013). Two of the three protected areas, namely Collywobbles Vulture Colony (IBA SA088) and Pondoland Cape Vulture Colonies (IBA SA126), were designated as IBAs specifically to promote the conservation of this threatened species (BirdLife International 2014a; BirdLife International 2014b). However, foraging vultures are rarely confined to protected areas and are thus exposed to numerous threats elsewhere (Bamford et al. 2007; Phipps et al. 2013a). For example, Cape Vultures are illegally killed for the traditional medicine market and are negatively impacted by power line infrastructure in the Eastern Cape (Boshoff et al. 2011; Mander et al. 2007). Poisoned carcasses, resulting in mass vulture mortalities, appear to be an infrequent occurrence in subsistence farmland areas, but do occur on commercial farms (Brown & Piper 1988).

A possible benefit to vultures in the former Transkei is the relatively high livestock mortality rates compared to commercial farming areas, which results in an abundance of carrion (Boshoff et al. 2009; Vernon 1998). Furthermore, the landscape in the former Transkei contains numerous suitable cliffs on which Cape Vultures roost and breed (Mundy et al. 1992; Piper & Ruddle 1986). Despite having knowledge of the potential threats and perceived benefits for Cape Vultures, knowledge of the movement ecology and detailed demographic information of Cape Vultures in this area is lacking.

BirdLife South Africa, the Endangered Wildlife Trust (EWT) and a number of bird specialists recommend 40 km buffers around Cape Vulture breeding colonies as conservation priority areas to prevent mortalities from wind turbines and hazardous power infrastructure development (Boshoff & Minnie 2011; Retief et al. 2013). Breeding Cape Vultures of the southern node population are known to forage and move extensively within this range (Boshoff & Minnie 2011; Boshoff, Robertson & Norton 1984; Brown & Piper 1988; Robertson & Boshoff 1986).

Breeding vultures that forage within 40 km of the colony are better able to relieve their partner of parenting duties so that both can forage on the same day (Ruxton & Houston 2002). Vultures that forage in this manner are thought to have higher breeding success because of a higher food delivery rate to the chick (Ruxton & Houston 2002). However, telemetry-based Cape Vulture studies in other regions have indicated that both breeding and non-breeding Cape Vultures forage considerably farther than 40 km from the breeding colony, which may weaken the conservation goals of the colony buffers (Bamford et al. 2007; Phipps et al. 2013b).

Foraging ranges of vultures may be influenced by the surrounding land uses or presence of vulture feeding sites. Vulture feeding sites (vulture restaurants) provide an uncontaminated, regular supply of carrion for vultures, which aims to prevent mortalities from food shortages and poisonings (Piper, Boshoff & Scott 1999). Most operate on commercial farms in South Africa (EWT and Ezemvelo KwaZulu-Natal [KZN] Wildlife unpublished data). In the Eastern Cape, all active Cape Vulture breeding colonies are in or near subsistence farmland with few vulture feeding sites, but the degree of subsistence farmland use by Cape Vultures remains unknown.

The aim of this study was to document the foraging range and habitat use of adult Cape Vultures in the former Transkei from a colony in the Mkambati Nature Reserve. One intention of the study was to test if 40 km buffers around southern Cape Vulture breeding colonies are adequate for their intended conservation purposes. The size, shape and habitat use in the overall foraging and core areas were investigated and possible seasonal differences quantified. Seasons were separated into either breeding or non-breeding season.

Adult vultures were expected to conduct fewer foraging trips during the early breeding season and incubation (Kendall et al. 2014; Spiegel et al. 2013). Breeding behaviour may concentrate Cape Vulture movements to areas that maximise the success of foraging trips. These areas would be ideal to identify for conservation planning. Additionally, a small proportion of Cape Vultures may migrate from the eastern part of the Eastern Cape to the west in the non-breeding season (Boshoff et al. 2009). If this migration occurs, it would be important to isolate any corridors or flight paths. Vulture movements may be influenced by the availability of resources across the landscape. Therefore, resource selection by the vultures was thought to differ with land use and season (Murn & Anderson 2008; Vernon 1998). The location of the study vulture colony provides a unique opportunity to investigate the vultures’ use of subsistence and commercial farmland, as both land uses are present within 100 km of the colony.

Nine transmitters recorded location data for 277 ± 72 days. Of the vultures fitted with transmitters, five reached an MCP asymptote during the breeding season and four during the non-breeding season (Figure A2). The average number of GPS locations for the breeding and non-breeding seasons were 717 ± 122 (n = 5) and 820 ± 123 (n = 4) respectively. The number of fixes required for MCPs to become constant varied, but generally, transmitters with fewer than 300 GPS locations were found to be insufficient. Some vultures were tracked for both seasons, while other transmitters were deployed later in the season, or failed. Three transmitters stopped working for unknown reasons (birds were resighted alive) before 300 GPS locations were collected; these data were excluded from the analyses. Two transmitters only collected data for one season (X023 and X022). Of the vultures used for analysis, two (X027 and X023) were confirmed to have successfully raised chicks in 2013. One vulture (X022) was observed at a nesting site arranging nesting material with its partner, but did not breed.

This study highlights the importance of subsistence farmland, rather than commercial farmland, as foraging habitat for Cape Vultures from the Msikaba colony. Although the results presented here are from a small and restructured sample size (n = 9), they illustrate the seasonal foraging and habitat selection patterns of the Cape Vulture in the southern node population.

Adult vultures from the Msikaba colony exhibited a well-defined foraging range. The tagged vultures did not participate in westerly migratory behaviour as previously reported by Boshoff et al. (2009). Foraging ranges calculated as MCPs were found to overlap considerably in the breeding and non-breeding seasons. Other studies have also observed that the distance covered by vultures during the breeding season is similar to the non-breeding season, but foraging trips occurred less frequently in the early breeding season and during incubation (Bamford, Monadjem & Hardy 2007; Kendall et al. 2014; Spiegel et al. 2013). The 50% core area around the breeding colony was oval shaped and extended towards KwaZulu-Natal with a radius ranging 17 km – 46 km during the breeding season. During the non-breeding season the 50% KDE around the colony increased to a maximum radius of 52 km. The size of the core area around the colony was therefore larger than the proposed 40 km buffer (Boshoff & Minnie 2011).

As the home range represents an area ‘traversed by the individual in its normal activities of food gathering, mating and caring for young’ (Burt 1943), a smaller range may be explained by the abundance of food or suitable roosts in the environment. Formal protected areas were used more than expected during the breeding season, possibly because breeding sites were located in protected areas, not because there was more carrion available. As adult Cape Vultures were captured in the Mkambati Nature Reserve and two vultures were confirmed successful breeders, more time was spent at this locale.

Cape Vultures used formal protected areas less during the non-breeding season, while natural woody vegetation and subsistence farmlands were preferred. Use of natural woody vegetation by the vultures may have been misinterpreted because of the scale of the habitat classifications, as cliffs were not distinguished in the habitat classifications. Vultures did not necessarily use the woody vegetation, but the steep cliffs located above them, as roosting sites. Roost sites in the study area were typically located on isolated cliff faces with indigenous forest at the base (Boshoff & Minnie 2011; pers. obs.).

The two 50% KDEs created during the non-breeding season were both located in subsistence farmland that contains only one formal (registered with EWT or Ezemvelo KZN Wildlife) vulture feeding site, which was located in the Mkambati Nature Reserve. Other studies have found that African vultures use subsistence farmland less (Bamford et al. 2007; Bamford et al. 2009). This could be explained by different livestock carcass management (burning or burying) or over-harvesting of forest resources, which prevent tree-nesting vulture species from inhabiting these areas (Monadjem & Garcelon 2005). In the former Transkei, carrion may be more readily available because of inadequate animal husbandry and abundant tick-borne diseases (Shackleton et al. 2013). Strong cultural traditions may provide another scavenging opportunity for vultures: during traditional ceremonies, local amaXhosa people slaughter and butcher animals, the leftovers of which are discarded for vultures and other scavengers (Pfeiffer pers. obs.).

Commercial farmland areas were used less than expected during both seasons, despite the presence of formal vulture feeding sites. However, the northernmost 50% KDE in the breeding season was located near multiple vulture feeding sites. (One feeding site was located inside the northernmost 50% KDE.) The number of fixes a day in the current study (six a day including roosting locations) may have been insufficient to identify feeding events, which may have resulted in underestimating the use of vulture feeding sites. Furthermore, Cape Vultures can be grounded at roost sites for long periods of time because of adverse soaring conditions. Accordingly, these results may overestimate roosting locations and underestimate feeding events (Monsarrat et al. 2013; Spiegel et al. 2013). Future research should use higher resolution GPS data in order to identify feeding events and then calculate habitat use.

Although vultures are far-ranging foragers that will never be fully secure within protected areas, it is essential to identify and proclaim conservation buffers. Tracking of a small sample of adult Cape Vultures from one colony has successfully identified the main foraging areas of vultures from that colony, and perhaps in the region. These areas can be targeted in focused strategic action plans aimed at avoiding or reducing the mortality of vultures. It will only be with the collaboration of communities, policy makers, conservation organisations and provincial governments that this regionally endangered vulture species will survive.