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Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania.

Brito JC, Martínez-Freiría F, Sierra P, Sillero N, Tarroso P - PLoS ONE (2011)

Bottom Line: Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal.Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow.Classification of Mauritanian mountains as protected areas should be prioritised.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, Instituto de Ciências Agrárias de Vairão, Vairão, Portugal. jcbrito@mail.icav.up.pt

ABSTRACT

Background: Relict populations of Crocodylus niloticus persist in Chad, Egypt and Mauritania. Although crocodiles were widespread throughout the Sahara until the early 20(th) century, increased aridity combined with human persecution led to local extinction. Knowledge on distribution, occupied habitats, population size and prey availability is scarce in most populations. This study evaluates the status of Saharan crocodiles and provides new data for Mauritania to assist conservation planning.

Methodology/principal findings: A series of surveys in Mauritania detected crocodile presence in 78 localities dispersed across 10 river basins and most tended to be isolated within river basins. Permanent gueltas and seasonal tâmoûrts were the most common occupied habitats. Crocodile encounters ranged from one to more than 20 individuals, but in most localities less than five crocodiles were observed. Larger numbers were observed after the rainy season and during night sampling. Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal.

Conclusion/significance: Research priorities in Chad and Egypt should focus on quantifying population size and pressures exerted on habitats. The present study increased in by 35% the number of known crocodile localities in Mauritania. Gueltas are crucial for the persistence of mountain populations. Oscillations in water availability throughout the year and the small dimensions of gueltas affect biological traits, including activity and body size. Studies are needed to understand adaptation traits of desert populations. Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow. Monitoring is needed to detect demographical and genetical trends in completely isolated populations. Crocodiles are apparently vulnerable during dispersal events. Awareness campaigns focusing on the vulnerability and relict value of crocodiles should be implemented. Classification of Mauritanian mountains as protected areas should be prioritised.

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Examples of oueds, lakes and tâmoûrts with presence of Nile crocodiles in Mauritania.A. oued Foum Goussas; B. lake Boû blei'îne; C. tâmoûrt Taghtâfet; D. tâmoûrt Bougâri.
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pone-0014734-g005: Examples of oueds, lakes and tâmoûrts with presence of Nile crocodiles in Mauritania.A. oued Foum Goussas; B. lake Boû blei'îne; C. tâmoûrt Taghtâfet; D. tâmoûrt Bougâri.

Mentions: Excluding localities where crocodiles were not confirmed or extinct, gueltas and tâmoûrts were the most common habitats where individuals were found (40.8% and 26.8%, respectively), but presence was detected also in oueds (9.9%), sources (8.5%), lakes (8.5%) and dams (5.6%) (Figures 4 and 5). Crocodiles were observed in 19 permanent gueltas (73% of gueltas surveyed) and 17 seasonal tâmoûrts (90% of tâmoûrts surveyed).


Crocodiles in the Sahara desert: an update of distribution, habitats and population status for conservation planning in Mauritania.

Brito JC, Martínez-Freiría F, Sierra P, Sillero N, Tarroso P - PLoS ONE (2011)

Examples of oueds, lakes and tâmoûrts with presence of Nile crocodiles in Mauritania.A. oued Foum Goussas; B. lake Boû blei'îne; C. tâmoûrt Taghtâfet; D. tâmoûrt Bougâri.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3045445&req=5

pone-0014734-g005: Examples of oueds, lakes and tâmoûrts with presence of Nile crocodiles in Mauritania.A. oued Foum Goussas; B. lake Boû blei'îne; C. tâmoûrt Taghtâfet; D. tâmoûrt Bougâri.
Mentions: Excluding localities where crocodiles were not confirmed or extinct, gueltas and tâmoûrts were the most common habitats where individuals were found (40.8% and 26.8%, respectively), but presence was detected also in oueds (9.9%), sources (8.5%), lakes (8.5%) and dams (5.6%) (Figures 4 and 5). Crocodiles were observed in 19 permanent gueltas (73% of gueltas surveyed) and 17 seasonal tâmoûrts (90% of tâmoûrts surveyed).

Bottom Line: Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal.Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow.Classification of Mauritanian mountains as protected areas should be prioritised.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigação em Biodiversidade e Recursos Genéticos da Universidade do Porto, Instituto de Ciências Agrárias de Vairão, Vairão, Portugal. jcbrito@mail.icav.up.pt

ABSTRACT

Background: Relict populations of Crocodylus niloticus persist in Chad, Egypt and Mauritania. Although crocodiles were widespread throughout the Sahara until the early 20(th) century, increased aridity combined with human persecution led to local extinction. Knowledge on distribution, occupied habitats, population size and prey availability is scarce in most populations. This study evaluates the status of Saharan crocodiles and provides new data for Mauritania to assist conservation planning.

Methodology/principal findings: A series of surveys in Mauritania detected crocodile presence in 78 localities dispersed across 10 river basins and most tended to be isolated within river basins. Permanent gueltas and seasonal tâmoûrts were the most common occupied habitats. Crocodile encounters ranged from one to more than 20 individuals, but in most localities less than five crocodiles were observed. Larger numbers were observed after the rainy season and during night sampling. Crocodiles were found dead in between water points along dry river-beds suggesting the occurrence of dispersal.

Conclusion/significance: Research priorities in Chad and Egypt should focus on quantifying population size and pressures exerted on habitats. The present study increased in by 35% the number of known crocodile localities in Mauritania. Gueltas are crucial for the persistence of mountain populations. Oscillations in water availability throughout the year and the small dimensions of gueltas affect biological traits, including activity and body size. Studies are needed to understand adaptation traits of desert populations. Molecular analyses are needed to quantify genetic variability, population sub-structuring and effective population size, and detect the occurrence of gene flow. Monitoring is needed to detect demographical and genetical trends in completely isolated populations. Crocodiles are apparently vulnerable during dispersal events. Awareness campaigns focusing on the vulnerability and relict value of crocodiles should be implemented. Classification of Mauritanian mountains as protected areas should be prioritised.

Show MeSH