Update of distribution, habitats, population size, and threat factors for the West African crocodile in Mauritania

Abstract

The West African crocodile (Crocodylus suchus) is an emblematic species from the Sahara-Sahel with scarce knowledge on distribution and conservation status. This study updated the knowledge on distribution, occupied habitats, population size, and factors that threaten C. suchus and its habitats in Mauritania. Five field expeditions to Mauritania (2011-2016), allowed the detection of 26 new localities, increasing by 27% the current number of all known locations (adding up to ). In most localities less than five individuals were observed, and in all visiting sites the number of observed individuals ranged from one to 23. Eleven threat factors were identified, being droughts and temperature extremes (100% localities affected) and water abstraction for domestic use and nomadic grazing (94%) the most frequent. These findings suggest that crocodiles are apparently vulnerable in Mauritania and that future local conservation strategies are needed to assure the continuity of its fragile populations and preserve their habitats.

Promoting connectivity between priority freshwater sites for conservation in intermittent hydrological systems

“…Selecting degraded planning units compromises the effectiveness of conservation efforts and the probability of persistence of conservation features (Linke et al, 2012), so their selection was prevented by considering two measures of threats: (i) local threats to gueltas were obtained from Campos et al (2016) and Vale, Pimm & Brito (2015), which were classified following the International Union for Conservation of Nature (IUCN) Threats Classification Scheme (Salafsky et al, 2008) (Figure 4b), and (ii) upstream threats that might propagate into gueltas were obtained from the global human footprint. This approach has already been used in freshwater conservation to characterize the propagation of threats along the river network (Linke et al, 2012; Reis et al, 2019).…”

“…Graphical representation of the cost penalties: (a) for each sub-catchment derived by the global human footprint index (top-left inset) (Venter et al, 2018); and (b) for each guelta with information retrieved from Vale, Pimm & Brito (2015) and Campos et al (2016), following the International Union for Conservation of Nature (IUCN) Threats Classification Scheme (Salafsky et al, 2008). The human footprint comprises nine layers: human population density, built-up areas, night-time lights, land use, land cover, coastlines, roads, railroads, and navigable rivers connectivity penalties between sub-catchments as calculated in Equation 2 (Figure 5b).…”

Using multivariate statistics to assess ecotourism potential of water-bodies: A case-study in Mauritania

“…The sampling effort was on average 0.273 man/hours in each water-body. Estimations of crocodile numbers followed standard sampling protocols (Brito et al, 2011;Campos, Martínez-Freiría, Sousa, Santarém, & Brito, 2016). In water-bodies where crocodiles were not detected in January 2016, but were known to occur, the number of estimates were based in previous reports (Brito et al, 2011).…”

“…Anthropogenic impacts on environment are global drivers of ecological processes that influence biodiversity as a whole (Sanderson et al, 2002) and affect biodiversity availability for tourism experiences in the field. The number of threats affecting the water-bodies was quantified following the IUCN Threats Classification Scheme Version 3.2 (www.iucnredlist.org/technicaldocuments/classification-schemes/threatsclassificationscheme) and was available from Campos et al (2016). The Human Influence Index (HII) was extracted in a 1x1km window around each water-body.…”

Atlas of the distribution of amphibians and reptiles in the Diawling National Park, Mauritania

“…Surveys were performed in November 2012, November 2014, August 2015, January 2016, and April 2017. All surveys were standardised and followed baseline methodology for crocodile counting previously used in Mauritania (Brito et al, 2011;Campos et al, 2016): an observer installed over the rooftop of a four-wheel drive vehicle moving along the transect line, holding a highpower lamp, counted the number of pairs of eyes (from yellowish to goldish) that reflected the light emitted by the lamp within a distance of up to 100 m. Surveys started at around 23:00 h and lasted about 15 min (average vehicle speed 12.7 km / h), which allows the direct comparison of the total number of crocodiles observed in each survey.…”