Red List of South African Species

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Vulnerable (VU)
Assessors: Andrew Turner Johan Marais
Facilitators: Graham Alexander Krystal Tolley
Reviewers: Michael Bates Juan-Jacques Forgus Krystal Tolley Luke Verburgt

Rationale (Changed due to Same category and criteria)

The Nile crocodile was regionally listed as Vulnerable (A2ac) in South Africa due to declines in estimated total population size of more than 30 % over three generations (estimated at 144 years) (Marais and Bates 2013). Although there is no comprehensive population estimate available for the entire South African Nile crocodile population as of 2017, counts of two of the major subpopulations have been conducted since the last assessment in 2014. Summing recent figures for the Kruger National Park (S. Ferreira, SANParks pers. comm. 2017) and KwaZulu-Natal (Warner et al. 2016) yields an estimate of at least 5,389 non-hatchling Nile crocodiles. This figure is roughly 1,000 individuals less than the 2013 estimate but excludes numerous smaller populations. It is inferred that the total population number for South Africa in 2017 is not significantly reduced from the 2013 estimate although some Protected Areas have seen ongoing declines others have stabilized or increased slightly. This indicates that the 30 % decline over three generations still holds although the population is stable at this point in time. The environmental and ecological conditions that gave rise to the outbreak of pansteatitis in the Kruger National Park may be exacerbated by an invasion of silver carp (Huchzermeyer 2012, Huchzermeyer et al. 2013, but also see Huchzermeyer et al. 2017) and although mitigated by good rains (D. Pienaar, SANParks pers. comm. 2017) are an ongoing threat regardless of causal mechanism. Due to this and reports of persecution (V. Egan, Limpopo Economic Development, Environment and Tourism pers. comm. 2017) the decline in habitat quality is also considered to be a current threat. Thus the assessment of the regional population of Nile crocodile as Vulnerable A2ac is still applicable.

Distribution

Widespread throughout southern, eastern and northern Africa. In South Africa and Eswatini (Swaziland) it is distributed from the Zinkwazi River south of the Tugela River in KwaZulu-Natal (Combrink et al. 2011) northwards into Eswatini (Swaziland), Mpumalanga, Limpopo, northern Gauteng and adjacent parts of North-West Province (Bates et al. 2014). There are a number of commercial crocodile farms in the region from which there are occasional escapes. None of these accidental introductions have led to the establishment of new breeding populations although an intentional introduction has been successful (Combrink et al. 2011).

Population trend

Trend

Blake and Jacobsen (1992) estimated the total population in South Africa at 9,500 individuals. Recent population estimates of two areas within South Africa ( S. Ferreira, SANParks pers. comm. 2017 and KwaZulu-Natal (Warner et al. 2016) indicate at least 5,389 non-hatchling Nile crocodiles as of 2017.

Threats

The main threat is loss and degradation of habitat. This includes loss of the large natural terrestrial habitats required to support a sufficient prey base and degradation of lakes, wetlands, dams, rivers and estuaries, construction of dams in rivers and the attendant deterioration of water quality due to upstream contamination (Woodborne et al. 2012).  Other threats include human persecution (killing of adults and destruction of nests), negative effects of invasive vegetation, fire, over-fishing with gill nets, harvesting for the medicine market.

Uses and trade

No legal commercial offtake of wild populations permitted in the region. The species is in commercial use (crocodile ranching) in the region with 771 reported trade events reported on CITES (CITES Trade Database, UNEP World Conservation Monitoring Centre, Cambridge, UK) from 2014 to 2016 including 187,769 exported skins.

Conservation

Improve effectiveness of protective legislation and Protected Areas management. Educate local communities about how to avoid conflict with this species. Improve water quality management in rivers where the Nile crocodile occurs including all upstream stretches. Develop a management response for invasive carp where they may cause pansteatitis in Nile crocodiles. This should include ensuring release of environmental reserve flows. An updated, country-wide census of the Nile crocodile should be conducted within the next five years.

References 

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 publisher = {Suricata 1. South African National Biodiversity Institute},
 title = {Atlas and Red List of the Reptiles of South Africa, Lesotho and Swaziland},
 year = {2014}
}
,@book{2817,
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,@article{46590,
 author = {Combrink, X., Korrubel, J.L., Kyle, R., Taylor, R. and Ross, P.},
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 pages = {145--157},
 title = {Evidence of a Declining Nile Crocodile (<i>Crocodylus niloticus</i>) Population at Lake Sibaya, South Africa},
 volume = {41},
 year = {2011}
}
,@article{46590,
 author = {Schmitz, A., Mausfeld, P., Hekkala, E., Shine, T., Nickel, H., Amato, G. and Böhme, W.},
 journal = {Comptes Rendus Palevol.},
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 title = {Molecular evidence for species level divergence in African Nile Crocodiles <i>Crocodylus niloticus</i>},
 volume = {2},
 year = {2003}
}
,@inbook{46590,
 address = {Pretoria, South Africa},
 author = {},
 booktitle = {The conservation status of the Nile Crocodile (<i>Crocodylus niloticus</i>) in South Africa},
 editor = {Blake, D.K. and Jacobsen, N.H.G.},
 pages = {11--21},
 publisher = {Crocodilian Study Group of Southern Africa},
 title = {Conservation and Utilization of the Nile Crocodile in South Africa: Handbook on Crocodile Farming},
 year = {1992}
}
,@article{46590,
 author = {Hekkala, E.R., Amato, G., Desalle, R. and Blum M.J.},
 journal = {Conservation Genetics},
 pages = {1435--1443},
 title = {Molecular assessment of population differentiation and individual assignment potential of Nile crocodile (<i>Crocodylus niloticus</i>) populations.},
 volume = {11},
 year = {2010}
}
,@article{46590,
 author = {Ferreira, S.M. and Pienaar, D.},
 journal = {Aquatic Conservation: Marine and Freshwater Ecosystems},
 pages = {155--164},
 title = {The degradation of the crocodile population in the Olifants River Gorge of Kruger National Park, South Africa.},
 volume = {21},
 year = {2011}
}
,@article{46590,
 author = {Huchzermeyer, K.D.A. },
 journal = {Journal of the South African Veterinary Association },
 number = {1},
 pages = {9 pp},
 title = {Prevalence of pansteatitis in African sharptooth catfish, <i>Clarias gariepinus</i> (Burchell), in the Kruger National Park, South Africa},
 volume = {83},
 year = {2012}
}
,@article{46590,
 author = {Huchzermeyer, K.D.A., Woodborne, S., Osthoff, G., Hugo, A., Hoffman, A.C., Kaiser, H., Steyl, J.C.A. and Myburgh, J.G. },
 journal = {Journal of Fish Diseases},
 pages = {1665–1680},
 title = {Pansteatitis in polluted Olifants River impoundments: nutritional perspectives on fish in a eutrophic lake, Lake Loskop, South Africa.},
 volume = {40},
 year = {2017}
}
,@article{46590,
 author = {Huchzermeyer, K.D.A., Osthoff, G., Hugo, A. and Govender, D. },
 journal = {Journal of Fish Diseases},
 pages = {897–909},
 title = {Comparison of the lipid properties of healthy and pansteatitis-affected African sharptooth catfish, <i>Clarias gariepinus</i> (Burchell), and the role of diet in pansteatitis outbreaks in the Olifants River in the Kruger National Park, South Africa},
 volume = {36},
 year = {2013}
}
,@article{46590,
 author = {Warner, J.K., Combrink, X., Calverley, P., Champion, G and Downs, C.T.},
 journal = {Zoomorphology},
 number = {4},
 pages = {511–521},
 title = {Morphometrics, sex ratio, sexual size dimorphism, biomass, and population size of the Nile crocodile (<i>Crocodylus niloticus</i>) at its southern range limit in KwaZulu-Natal, South Africa},
 volume = {135},
 year = {2016}
}
,@techreport{46590,
 author = {Downs, C.T., Calverley, P., Champion, G., Combrink, X., Myburgh, J., Summers, M. and Warner, J.},
 institution = {Water Research Commission},
 title = {Status of Nile Crocodile in north eastern KwaZulu-Natal and conservation management recommendations},
 year = {2015}
}
,@article{46590,
 author = {Woodborne, S., K. D. A. Huchzermeyer, D. Govender, D. J. Pienaar, G. Hall, J. G. Myburgh, A. R. Deacon, J. Venter, and N. Lubcker.},
 journal = {Ecosphere},
 number = {10},
 pages = {17},
 title = {Ecosystem change and the Olifants River crocodile mass mortality events},
 volume = {3},
 year = {2012}
}
,@article{46590,
 author = {Hekkala, E., Shirley, M.H., Amato, G., Austin, J.D., Charter, S., Thorbjarnarson, J., Vliet, K.A., Houck, M.L., DeSalle, R. and Blum, M.J.},
 journal = {Molecular Ecology},
 number = {20},
 pages = {4199--4215. doi: 10.1111/j.1365--294X.2011.05245.x},
 title = {An ancient icon reveals new mysteries: mummy DNA resurrects a cryptic species within the Nile crocodile},
 volume = {20},
 year = {2011}
}
,]
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