Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

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Publication Details

Contributor list: Warner JK, Combrink X, Myburgh JG, Downs CT

Publisher: Springer Verlag (Germany)


Publication year: 2016

Journal: Ecotoxicology (ISSN:0963-9292) (eISSN:1573-3017) PubCount Year: 2018, 2019, 2020

Journal acronym: ECOTOXICOLOGY

Volume number: 25

Issue number: 5

Start page: 950

End page: 958

Number of pages: 9

ISSN: 0963-9292

eISSN: 1573-3017

Languages: English-Great Britain (EN-GB)

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Generally crocodilians have received little attention with regard to the effects of lead toxicity despite their trophic status as apex, generalist predators that utilize both aquatic and terrestrial habitats, thereby exposing them to a potentially wide range of environmental contaminants. During July-October 2010 we collected whole blood from 34 sub-adult and adult free-ranging Nile crocodiles (Crocodylus niloticus) from three separate populations in northeastern South Africa in order to analyze their blood lead concentrations (BPb). Concentrations ranged from below detectability (< 3 mu g/dL, n = 8) to 960 mu g/dL for an adult male at the Lake St Lucia Estuary. Blood lead concentrations averaged 8.15 mu g/dL (SD = 7.47) for females and 98.10 mu g/dL (SD = 217.42) for males. Eighteen individuals (53 %) had elevated BPbs (a parts per thousand yen10 mu g/dL). We assessed 12 general linear models using Akaike's Information Criterion (AIC) and found no significant statistical effects among the parameters of sex, crocodile size and population sampled. On average, crocodiles had higher BPbs at Lake St Lucia than at Ndumo Game Reserve or Kosi Bay, which we attribute to lead sinker ingestion during normal gastrolith acquisition. No clinical effects of lead toxicosis were observed in these crocodiles, even though the highest concentration (960 mu g/dL) we report represents the most elevated BPb recorded to date for a free-ranging vertebrate. Although we suggest adult Nile crocodiles are likely tolerant of elevated Pb body burdens, experimental studies on other crocodilian species suggest the BPb levels reported here may have harmful or fatal effects to egg development and hatchling health. In light of recent Nile crocodile nesting declines in South Africa we urge further BPb monitoring and ecotoxicology research on reproductive females and embryos.


Crocodile, Crocodylus, Ecotoxicology, Heavy metal, LEAD, South Africa


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Last updated on 2020-20-04 at 05:12