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Nesting biology and ecology have been investigated for Nile crocodiles ( Crocodylus niloticus ), but information on behaviour and movement patterns of nesting females during nest guarding is scant. Consequently, we investigated the home ranges, nest-site selection strategies, movement patterns, activity levels and nest fidelity of four nesting females using telemetry. Gravid females selected winter basking/breeding areas close (351 ± 2 m) to nest-sites. Mean home range and core-use areas of nesting females were 8539 ± 4752 m 2 , and 4949 ± 3302 m 2 respectively. Mean home range (0.85 ha) was significantly smaller than those of non-nesting females (108.4 ha) during nesting season. Activity levels and mean daily movements while nesting were 8.1 ± 2.5% and 213 ± 64 m, respectively, and increased to 47.9 ± 11.7% and 2176 ± 708 m post-nesting. Overall levels of nest fidelity were 82.8 ± 11.7%, (day 78.1 ± 15.9%; night 87.3 ± 7.8%). Highest nest fidelity recorded during incubation was 99.7% over 96 days. Telemetry data from nesting females were helpful for elucidating spatial and behavioural patterns during the nest guarding period, and provided novel insights into this biologically important event. [ABSTRACT FROM AUTHOR]

Animal body size and sex are requisite data for understanding population structure and demography. Little information exists regarding Nile crocodile, Crocodylus niloticus, morphometrics, sex ratios of wild populations, sexual size dimorphism and standing crop biomass. We captured 322 C. niloticus at Lake St Lucia and Ndumo Game Reserve, South Africa, the two largest crocodile populations at the southern extent of the species' range in Africa, and measured a suite of physical characteristics to create predictive models of body length from other morphological attributes and body mass. Our sample included 118 hatchlings, 91 subadults and 113 adults. Strong positive allometric relationships were found between body length metrics (total length and snout-vent length) and other morphometrics. All morphometric regressions were linear, with the exception of the relationship of body length to body mass, which was logarithmic. Among relationships of cranial morphology and body length, we found considerable individual variation among all size classes. The mean head width-to-head length ratio was 1.9 ± 1.6, and mean head length-to-total length ratio was 0.14 ± 0.005. The sex ratios for non-hatchling individuals at both populations were essentially 1:1, but adult sex ratios were male biased. We calculated a total standing crop biomass of 96,867.18 kg (161.45 kg/km) and 52,640.40 kg (1504.01 kg/km) for C. niloticus at Lake St Lucia and Ndumo Game Reserve, respectively, and an estimated 3650 non-hatchling individuals for the province of KwaZulu-Natal. The data presented here will help inform crocodile management and population surveys in South Africa, where C. niloticus is an important apex predator that partitions aquatic resources and occasionally comes into conflict with human beings. [ABSTRACT FROM AUTHOR]

Information regarding nest predation, nest abandonment, and maternal care in the Nile crocodile ( Crocodylus niloticus ) is largely restricted to anecdotal observations, and has not been studied quantitatively. Consequently, we investigated their nesting biology using camera-traps over four years at Lake St Lucia, South Africa. We obtained 4305 photographs (daylight captures = 90.1%, nocturnal = 9.9%) of 19 nest-guarding females. Of 19 monitored nests, 37% were raided by predators (mean = 12.1 ± 6.2 days subsequent to camera placement). All females returned to their nests following first predation, and on average returned three times between predator raids before nest abandonment. Water monitors ( Varanus niloticus ) and marsh mongoose ( Atilax paludinosus ) were the main egg predators. Nesting raids lasted 5.9 ± 1.6 days. Diurnally females were seldom on the nest, except during cool/cloudy weather or rain, preferring to guard from nearby shade. Females defended nests aggressively against non-human intruders. Five Nile crocodile females were observed liberating their hatchlings from nests. A detailed sequence of a mother excavating and transporting hatchlings revealed 13 excursions between nest and water over 32.5 h. This, after months of continual nest attendance and defence, is illustrative of the high level of maternal care in Nile crocodiles. Camera-trapping is an effective, non-invasive method for further crocodile nesting behaviour research. [ABSTRACT FROM AUTHOR]

Formerly widespread throughout the water bodies of eastern South Africa, viable Nile crocodile (Crocodylus niloticus) populations are now restricted to three disjunct protected areas in KwaZulu-Natal (KZN), Mpumalanga and Limpopo. Growing evidence suggests that protected populations are declining, including the breeding C. niloticus population at Lake Sibaya in KZN. Aerial surveys were conducted at Lake Sibaya from 2003-2004 and 2007-2009, spotlight counts in 2003 and intensive nesting surveys in 2003 and 2004. Seven adults were counted during the 2009 aerial survey; an 89% decrease from the 1985 count (62 adults) and a decline of 95-98% of the estimated 1970 adult population. Likewise, in 1970 30 nests were recorded, compared to three nests in 2003 and no recorded nests in 2004. The non-hatchling population in 2003 was estimated at 48 individuals and decreased to an estimated eight in 2009. The neighbouring community perceives crocodiles as a threat to their lives and livestock, and increasing human pressures on C. niloticus in the area will probably ensure that the population will not recover naturally. Unless crocodiles are perceived as a useful or somehow beneficial natural resource by the surrounding community, the species faces possible extirpation from Lake Sibaya in the future. [ABSTRACT FROM AUTHOR]

Conflicts with wildlife are a major challenge for conservation across Africa, and Nile crocodiles Crocodylus niloticus are allegedly responsible for more attacks on people than any other species; however, there is a lack of data regarding such attacks. We analysed reported attacks on people by Nile crocodiles in South Africa and eSwatini (Swaziland) during 1949–2016, identifying spatial and temporal patterns in attack incidence, as well as victim demographics. Through a literature review and archival searches we identified records of 214 attacks. Most attacks occurred in natural water bodies, with attacks in dams increasing since 2000. Most victims were attacked while swimming or bathing, others while fishing, doing domestic chores, and crossing waterways. There was a significant relationship between gender and activity when attacked. Children (< 16 years old) accounted for 51% of all attacks, with a higher fatality rate compared to adults. Most victims were male (65%), with teenage boys being the largest individual category. We make recommendations for conservation policy and management to mitigate attacks by Nile crocodiles. [ABSTRACT FROM AUTHOR]

The article offers information on Pleistocene large reptile tracks and probable swim traces on South Africa's Cape south coast. Topics include implications for the understanding of Pleistocene palaeo environment and palaeoclimate; and demonstrate the potential for ichnology to complement the traditional body fossil record.

The proliferation in mesoherbivore numbers and their associated impact on the detrital ground cover were deemed responsible for the decline in fossorial herpetofaunal densities in Ndumo Game Reserve during the early 2000s. Subsequent increased poaching pressure and wildlife declines allowed the reassessment of the sand forest fossorial herpetofaunal community to test this assumption. We found no significant increase in the two most abundant soil‐living reptiles despite significant mesoherbivore declines. This may indicate that either fossorial herpetofaunal numbers increase very slowly, or that the initial two survey methodologies were incomparable. Alternatively, some unknown environmental factor may be suppressing populations or the survey results are not representative of the fossorial herpetofaunal community. [ABSTRACT FROM AUTHOR]

Nile crocodiles ( Crocodylus niloticus ) are important apex predators in many tropical and subtropical aquatic habitats throughout much of sub-Saharan Africa. In South Africa, large crocodile populations inhabit lakes and wetlands that are impacted by organochlorine pesticides (OCPs). Despite the continued use of these compounds and their potential adverse effects on key wildlife populations in southern Africa, limited ecotoxicoloigcal data exist. In this study, we examined the accumulation of OCPs in fat tissues of live, wild Nile crocodiles from iSimangaliso Wetland Park, a region of significant biological importance. All samples (n = 15) contained multiple contaminants in highly elevated concentrations, with total residue burdens varying between 3600 and 8000 ng g −1 ww. DDT and its metabolites were the dominant compounds detected in most samples, with ∑DDT concentrations ranging between 520 and 3100 ng g −1 ww. Elevated levels of other OCPs were also detected, including lindane (67–410 ng g −1 ww), aldrin (150–620 ng g −1 ww) and heptachlor (170–860 ng g −1 ww). Our findings show that crocodiles are exposed to OCPs throughout their range within iSimangaliso Wetland Park and contain some of the highest concentrations ever recorded in crocodilian tissue. Results indicate the need for a greater understanding of the impacts of OCP exposure and toxicological responses in crocodiles from iSimangaliso, and in Nile crocodile populations in general. The novel surgical technique described in this study provides an effective method for assessing relationships between contaminant body burdens and their potential reproductive and developmental consequences in crocodilians. [ABSTRACT FROM AUTHOR]

Large‐bodied predators are well represented among the world's threatened and endangered species. A significant body of literature shows that in terrestrial and marine ecosystems large predators can play important roles in ecosystem structure and functioning. By contrast, the ecological roles and importance of large predators within freshwater ecosystems are poorly understood, constraining the design and implementation of optimal conservation strategies for freshwater ecosystems. Conservationists and environmentalists frequently promulgate ecological roles that crocodylians are assumed to fulfil, but often with limited evidence supporting those claims. Here, we review the available information on the ecological importance of crocodylians, a widely distributed group of predominantly freshwater‐dwelling, large‐bodied predators. We synthesise information regarding the role of crocodylians under five criteria within the context of modern ecological concepts: as indicators of ecological health, as ecosystem engineers, apex predators, keystone species, and as contributors to nutrient and energy translocation across ecosystems. Some crocodylians play a role as indicators of ecosystem health, but this is largely untested across the order Crocodylia. By contrast, the role of crocodylian activities in ecosystem engineering is largely anecdotal, and information supporting their assumed role as apex predators is currently limited to only a few species. Whether crocodylians contribute significantly to nutrient and energy translocation through cross‐ecosystem movements is unknown. We conclude that most claims regarding the importance of crocodylians as apex predators, keystone species, ecosystem engineers, and as contributors to nutrient and energy translocation across ecosystems are mostly unsubstantiated speculation, drawn from anecdotal observations made during research carried out primarily for other purposes. There is a paucity of biological research targeted directly at: understanding population dynamics; trophic interactions within their ecological communities; and quantifying the short‐ and long‐term ecological impacts of crocodylian population declines, extirpations, and recoveries. Conservation practices ideally need evidence‐based planning, decision making and justification. Addressing the knowledge gaps identified here will be important for achieving effective conservation of crocodylians. [ABSTRACT FROM AUTHOR]

Lead (Pb) exposure is a widespread wildlife conservation threat, but impacts on reptile populations remain poorly documented. In this study, we examined Pb exposure and accumulation in a wild population of Nile crocodiles (Crocodylus niloticus) at Lake St Lucia, South Africa. Recreational angling has occurred in the area since the 1930s and incidental ingestion of Pb fishing weights has previously been identified as a major source of Pb poisoning in the local crocodile population. In 2019, we sampled blood and tail fat tissues from wild (n = 22) and captive (n = 3) crocodiles at Lake St Lucia to investigate potential impacts of chronic Pb exposure on crocodilian health. Lead was detected in blood samples of all wild crocodiles, although concentrations varied widely between individuals (86–13,100 ng ml−1). The incidence of Pb poisoning was higher in male crocodiles, with mean blood lead (BPb) concentrations in males (3780 ± 4690 ng ml−1) significantly (p < 0.001) higher compared to females (266 ± 230 ng ml−1). Blood Pb concentrations were correlated with concentrations measured in tail fat tissue (n.d – 4175 ng g−1 wet wt.). Although most of the crocodiles sampled appeared to be in good physical condition, highly elevated BPb concentrations (>6000 ng ml−1) were associated with markedly suppressed packed cell volumes (4.6–10.8%) and severe deterioration in tooth condition. These findings suggest that anaemia and tooth loss may be clinical signs of long-term environmental exposure to Pb. Although previously undocumented in crocodilians, these symptoms are consistent with Pb poisoning observed in birds and mammals, and suggest that crocodilians may be more susceptible to the long-term toxic effects of Pb than previously thought. In light of these findings, we suggest that the impact of accumulated Pb on crocodilian fitness, reproduction and mortality requires urgent attention. [Display omitted] • We examine Pb concentrations in blood and fat tissues of free-ranging Nile crocodiles. • Highly elevated Pb levels attributed to incidental ingestion of Pb fishing weights. • Clinical signs of Pb toxicosis observed in individuals with blood Pb > 6000 ng ml−1 • Long-term Pb exposure associated with anaemia and severe tooth loss in individuals. [ABSTRACT FROM AUTHOR]

Biologically significant concentrations of organochlorine pesticides (OCPs) continue to be reported in wildlife populations and are of particular concern in species that occupy the highest trophic levels. Nile crocodiles (Crocodylus niloticus) are important apex predators occurring throughout much of tropical and subtropical sub-Saharan Africa, where they inhabit estuarine and freshwater habitats often impacted by contamination. In this study we examined pesticide residue accumulation in fat tissue from Nile crocodiles at Lake St Lucia, South Africa, where historically large quantities of OCPs have been used for agriculture and disease control. During 2019, we collected tail fat samples from wild (n = 21) and captive (n = 3) individuals to examine the influence of habitat, body size and sex on variations in bioaccumulation. The principal contaminant found was p , p ′-DDE, a major persistent metabolite of DDT, which continues to be used in the region for combating malaria. Tissue p , p ′-DDE concentrations in wild crocodiles (95–1200 ng g−1 ww) were significantly (p < 0.05) higher compared to captive individuals (23–68 ng g−1 ww) and strongly correlated (R2 > 0.70) to body length. Male (n = 14) and female (n = 7) wild crocodiles exhibited similar contaminant body burdens, however, total concentrations were substantially lower than those measured in the same population during 2016/2017. Marked differences in residue levels and profiles appear to reflect changes in food availability and dietary exposure associated with a shift in environmental conditions. These findings suggest that periods of environmental stress may be associated with enhanced toxicological risk in crocodiles. Additional work is needed to better understand contaminant accumulation and elimination mechanisms in crocodiles, and their potential effects on reproductive health. Unlabelled Image • Investigated OCP bioaccumulation patterns in wild and captive Nile crocodiles • DDT metabolites found to be the principle contaminant in wild animals • Concentrations between males and females were similar and correlated with body size. • Significant difference in concentration burdens and profiles between sampling years • Temporal variations likely linked to environmental stress and dietary exposure [ABSTRACT FROM AUTHOR]