Damaliscus pygargus ssp. phillipsi
|Scientific Name:||Damaliscus pygargus ssp. phillipsi Harper, 1939|
Damaliscus dorcas ssp. phillipsi Harper, 1939
|Taxonomic Notes:||Appeared in the 1996 IUCN Red List as Damaliscus dorcas phillipsi, but it is generally agreed that D. pygargus phillipsi is the correct name (see Grubb in Wilson and Reeder 1993).|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Dalton, D., Parrini, F., Viljoen, P., Gaylard, A. & Peinke, D.|
|Reviewer(s):||Mallon, D. & Child, M.F.|
|Contributor(s):||Relton, C., Selier, J. & Page-Nicholson, S.|
Listed as Least Concern, as Blesbok are abundant on both formally and privately protected land. We estimate a minimum mature population size of 54,426 individuals (using a 70% mature population structure) across 678 protected areas and wildlife ranches (counts between 2010 and 2016). There are at least an estimated 17,235 animals (counts between 2013 and 2016) on formally protected areas across the country, with the largest subpopulation occurring on Golden Gate Highlands National Park. The population has increased significantly over three generations (1990-2015) in formally protected areas across its range and is similarly suspected to have increased on private lands. Apart from hybridisation with Bontebok, there are currently no major threats to its long-term survival. Approximately 69% of Blesbok can be considered genetically pure (A. van Wyk and D. Dalton unpubl. data), and stricter translocation policies should be established to prevent the mixing of subspecies. Overall, this subspecies could become a keystone in the sustainable wildlife economy.
|Previously published Red List assessments:|
|Range Description:||Historically, the Blesbok ranged across the Highveld grasslands of the Free State and Gauteng provinces, extending into northwestern KwaZulu-Natal, and through parts of the Karoo in the Eastern and Northern Cape. Over 300 km separated the Blesbok from the historical range of the closely-related Bontebok (previously restricted to the Western Cape) (Skinner and Chimimba 2005). Despite large populations in the Highveld, the Blesbok was heavily exploited for meat, and by the late 19th century, Blesbok were extinct from KwaZulu-Natal and only about 2,000 individuals remained in South Africa (Skinner and Chimimba 2005).|
More recently, Blesbok populations have recovered remarkably, especially on private land, and have been relocated across South Africa to regions both within and outside of its native range (for example, Power 2014). Although formerly present in western Lesotho, Blesbok were hunted to extinction in the country before 1900 (Lynch 1994). Swaziland is outside of the native historical range of Blesbok, however, extralimital introductions have occurred in Malolotja Nature Reserve and Mlilwane Wildlife Sanctuary (Monadjem 1998). Similarly, this species has been introduced to private game farms outside of its range in Zimbabwe, Botswana and Namibia (East 1999).
Introduced:Botswana; Mozambique; Namibia; Swaziland; Zimbabwe
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Subpopulations are thriving in the various provinces where the species occurs and the total population is estimated to be at least 77,751 animals (2010–2016 counts) on both formally protected areas and wildlife ranches across the country (678 reserves or ranches). This would equate to 54,426 mature individuals using a 70% mature population structure. On formally protected areas alone, there were at least 17,235 animals counted between 2013 and 2016 (EWT unpubl. data). Thus, there are well over 10,000 mature individuals in the assessment region with no expectations of major declines in the near future. However, subpopulations have declined sharply in areas outside of their distributional range (Mkhambithi, Nduli and Luchaba Nature Reserves) due to the removal of extra-limital species from these reserves. The total population estimate is lower than what East (1999) estimated: 235,000–240,000 animals, of which 97% were thought to be on private farms and 3% in protected areas (East 1999). While the latter is likely an overestimate, the true population size probably falls between the two estimates. There are certainly greater numbers on private land than formally protected areas. For example, in North West Province, there were an estimated 1,483 Blesbok in provincial parks, while around 9,874 occurred on private farms in 2010 (Power 2014). However, more field surveys are needed to determine which private subpopulations can be considered wild and free-roaming.|
Generation length has been calculated as 8.4 years, yielding a three-generation window of 25 years (1990–2015). Over three generations, the population is estimated to have increased. For example: in Camdeboo National Park (Eastern Cape) the subpopulation increased from 67 in 1990 to 189 in 2015 (Gaylard unpubl. data); in Golden Gate Highlands National Park (Free State) the subpopulation increased from 451 in 1994 to 8,785 in 2016 (including the incorporation of QwaQwa National Park) (Bissett et al. 2016); and in Bloemhof Dam Nature Reserve (North West) the subpopulation increased from 91 in 1999 to 919 in 2015 (Nel 2015). Other subpopulations on formally protected areas are mostly increasing or stable. For example, Suikerbosrand Nature Reserve in Gauteng has sustained a subpopulation of around 500 since 2004 (521 and 466 individuals in 2004 and 2014 respectively) and over the past recent decade, subpopulations of Blesbok in provincial nature reserves in the Eastern Cape have been increasing (D. Peinke unpubl. data). In Free State Province, the population in provincial protected areas increased by an average annual rate of 28.2% between 2004 and 2014 (E. Schulze unpubl. data).
|Current Population Trend:||Increasing|
|Habitat and Ecology:||Grasslands are considered prime habitat for Blesbok, especially open plateau grasslands, characteristic of the South African Highveld, extending to altitudes of up to 2,000 m asl (East 1999). Blesbok have a preference for short grass, and depend largely on the availability of drinking water (David and Lloyd 2013). In Mountain Zebra National Park, they occur on grazing lawns where they help to maintain their preferred dietary short grass species. Blesbok feed nearly entirely on graminoids, and have a strong preference for burnt areas, often moving into burnt areas even before new grass growth is obvious (Skinner and Chimimba 2005). Blesbok feed selectively, often choosing contrasting grass species in burnt and unburnt habitats, and during different seasons. Blesbok showed a preference for Themeda triandra, Eragrostis curvula, Chloromelas spp. and Setaria nigrirostris within burnt habitats at Rietvlei Nature Reserve (du Plessis 1968).|
Blesbok are diurnal, with activity peaking during the early mornings, late evenings and during cool, overcast conditions (Skinner and Chimimba 2005). They are gregarious, exhibit characteristic behaviour similar to Bontebok, whereby they will frequently stand in orientated groups with their heads directed towards the sun and their faces low to the ground (Skinner and Chimimba 2005). Similar to Bontebok, Blesbok form large bachelor herds, which peak in size during the autumn rut period, and will inhabit home ranges away from those of territorial males and their associated harem herd (consisting of up to 25 females) (Novellie 1975, Skinner and Chimimba 2005). Blesbok and Bontebok differ not only in colouration, but also in social structure, whereby Bontebok maintain the same herd structure throughout the year, while Blesbok exhibit clear seasonal variation in herd structure. Large aggregations of Blesbok form during cold, dry conditions between June and August, when herds of all ages and sexes come together. These aggregations will split up from September onwards, and male territoriality becomes apparent from November, peaking in April (Skinner and Chimimba 2005).
Blesbok generally mate in autumn, and young are typically born between November and January (Skinner et al. 1974). Territorial males herd females into their territories, occasionally circling them in an attempt to retain them, however, females will sporadically move from territory to territory (Skinner and Chimimba 2005). Young are born following the first summer rainfall events, when forage is adequate to maintain females during lactation (Marais 1988). Females have been recorded as sexually mature by about 2.5 years old (du Plessis 1968), and experience a gestation period of approximately 240 days (Skinner et al. 1974). Usually Blesbok give birth to a single calf, weighing 6-7 kg (Skinner and Chimimba 2005).
Ecosystem and cultural services: Blesbok are a flagship, endemic species for South Africa’s Highveld grasslands, and are a valuable component of South Africa’s commercial hunting industry.
|Continuing decline in area, extent and/or quality of habitat:||No|
|Use and Trade:||
Blesbok are used for commercial trophy hunting on a national and international scale and by subsistence hunters for meat. They are also sold as live animals at game auctions. Blesbok are culled (for management purposes) commercially for meat, which is often more lucrative than live game sales. However, this is not predicted to have any negative effects on the population. The species has also recently been bred intensively for colour variants.
Wildlife ranching has greatly increased the population numbers and area of occupancy for this subspecies, which makes this a conservation success story, similar to the Bontebok. However, there are concerns that private landowners are mixing Bontebok and Blesbok on their properties and thereby facilitating hybridisation between the two subspecies. This threat should be monitored and translocation policies that prevent such mixing should be enforced.
Colour morphs occur naturally, however, these events are considered rare (Hetem et al. 2009). The evolutionary importance of the phenotypic trait “colouration” is well documented for many functions, including camouflage, mate selection, communication, regulation of physiological processes, ultra-violet protection and defence against parasites. However, in addition to environmental adaptation, artificial selection has altered the coat colour design of species due to human interference (Cieslak et al. 2011), and colour morphs are currently being bred by private landowners for the purpose of financial gain. Thus far, several thousand alleles have been described from approximately 150 identified coat colour-associated genes (Cieslak et al. 2011). Coat colour-associated mutations connected to several serious disorders has been reported (Reissmann and Ludwig 2013). Most of these disorders have been identified in humans, laboratory animals and domestic animals. Additional research into the effect of colour variants in wild subpopulations is thus needed. Additionally, the selective breeding of colour morphs could result in decreased genetic diversity and inbreeding in Blesbok populations. Lastly, the effect of releasing colour morphs and carriers of colour morph genes into the wild population would have to be determined, which may occur if the colour morph market crashes in the future.
Although hybridisation is currently a priority in the rarer subspecies, Bontebok, and is likely to affect Bontebok more than it does Blesbok, the proportion of hybridisation in the Blesbok population is currently unknown and further research is required to identify hybrid Blesbok.
Breeding of colour variants that may be associated with deleterious mutations may, if released in large numbers, reduce effective population size and can affect wild populations if carriers are released into formally protected areas. Additionally, selective breeding may result in reduced heterozygosity, inbreeding and bottlenecks. Inbreeding contributes to the decline and eventual extinction of small and isolated subpopulations. There is also ample evidence of fitness reduction due to inbreeding (inbreeding depression) and a decrease in reproductive performance (Amos and Balmford 2001). Populations that have passed through a severe bottleneck can show a markedly reduced ability to respond to change, particularly in the face of novel challenges.
This species occurs within a number of formally and privately protected areas across a number of provinces in South Africa. The economic value and popularity of the Blesbok on private farms has enabled this subspecies to re-occupy large areas of its original range; although substantial extra-limital subpopulations of the Blesbok have also been established on private land outside its natural range in South Africa and elsewhere. The identification of current hybrid populations and the restriction of movement of hybrids are suggested as key actions to conserve the subspecies.
Recommendations for land managers and practitioners:
|Citation:||Dalton, D., Parrini, F., Viljoen, P., Gaylard, A. & Peinke, D. 2017. Damaliscus pygargus ssp. phillipsi. The IUCN Red List of Threatened Species 2017: e.T30209A50197495.Downloaded on 26 April 2018.|
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