Detectability and impact of repetitive surveys on threatened West African crocodylians

Abstract West African crocodylians are among the most threatened and least studied crocodylian species globally. Assessing population status and establishing a basis for population monitoring is the highest priority action for this region. Monitoring of crocodiles is influenced by many factors that...

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Autores principales:	Michel N. Ahizi, Christine Y. Kouman, Allassane Ouattara, N’Dri Pascal Kouamé, Azani Dede, Emilie Fairet, Matthew H. Shirley
Formato:	article
Lenguaje:	EN
Publicado:	Wiley 2021
Materias:	cataphractus Côte d’Ivoire Crocodylus detection probability Mecistops niloticus Ecology QH540-549.5
Acceso en línea:	https://doaj.org/article/15dc090bf64a428ea12950998391e79f
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spelling	oai:doaj.org-article:15dc090bf64a428ea12950998391e79f2021-11-08T17:10:41ZDetectability and impact of repetitive surveys on threatened West African crocodylians2045-775810.1002/ece3.8188https://doaj.org/article/15dc090bf64a428ea12950998391e79f2021-11-01T00:00:00Zhttps://doi.org/10.1002/ece3.8188https://doaj.org/toc/2045-7758Abstract West African crocodylians are among the most threatened and least studied crocodylian species globally. Assessing population status and establishing a basis for population monitoring is the highest priority action for this region. Monitoring of crocodiles is influenced by many factors that affect detectability, including environmental variables and individual‐ or population‐level wariness. We investigated how these factors affect detectability and counts of the critically endangered Mecistops cataphractus and the newly recognized Crocodylus suchus. We implemented 195 repetitive surveys at 38 sites across Côte d’Ivoire between 2014 and 2019. We used an occupancy‐based approach and a count‐based GLMM analysis to determine the effect of environmental and anthropogenic variables on detection and modeled crocodile wariness over repetitive surveys. Despite their rarity and level of threat, detection probability of both species was relatively high (0.75 for M. cataphractus and 0.81 for C. suchus), but a minimum of two surveys were required to infer absence of either species with 90% confidence. We found that detection of M. cataphractus was significantly negatively influenced by fishing net encounter rate, while high temperature for the previous 48 h of the day of the survey increased C. suchus detection. Precipitation and aquatic vegetation had significant negative and positive influence, respectively, on M. cataphractus counts and showed the opposite effect for C. suchus counts. We also found that fishing encounter rate had a significant negative effect on C. suchus counts. Interestingly, survey repetition did not generally affect wariness for either species, though there was some indication that at least M. cataphractus was more wary by the fourth replicate. These results are informative for designing future survey and monitoring protocols for these threatened crocodylians in West Africa and for other endangered crocodylians globally.Michel N. AhiziChristine Y. KoumanAllassane OuattaraN’Dri Pascal KouaméAzani DedeEmilie FairetMatthew H. ShirleyWileyarticlecataphractusCôte d’IvoireCrocodylusdetection probabilityMecistopsniloticusEcologyQH540-549.5ENEcology and Evolution, Vol 11, Iss 21, Pp 15062-15076 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	cataphractus Côte d’Ivoire Crocodylus detection probability Mecistops niloticus Ecology QH540-549.5
spellingShingle	cataphractus Côte d’Ivoire Crocodylus detection probability Mecistops niloticus Ecology QH540-549.5 Michel N. Ahizi Christine Y. Kouman Allassane Ouattara N’Dri Pascal Kouamé Azani Dede Emilie Fairet Matthew H. Shirley Detectability and impact of repetitive surveys on threatened West African crocodylians
description	Abstract West African crocodylians are among the most threatened and least studied crocodylian species globally. Assessing population status and establishing a basis for population monitoring is the highest priority action for this region. Monitoring of crocodiles is influenced by many factors that affect detectability, including environmental variables and individual‐ or population‐level wariness. We investigated how these factors affect detectability and counts of the critically endangered Mecistops cataphractus and the newly recognized Crocodylus suchus. We implemented 195 repetitive surveys at 38 sites across Côte d’Ivoire between 2014 and 2019. We used an occupancy‐based approach and a count‐based GLMM analysis to determine the effect of environmental and anthropogenic variables on detection and modeled crocodile wariness over repetitive surveys. Despite their rarity and level of threat, detection probability of both species was relatively high (0.75 for M. cataphractus and 0.81 for C. suchus), but a minimum of two surveys were required to infer absence of either species with 90% confidence. We found that detection of M. cataphractus was significantly negatively influenced by fishing net encounter rate, while high temperature for the previous 48 h of the day of the survey increased C. suchus detection. Precipitation and aquatic vegetation had significant negative and positive influence, respectively, on M. cataphractus counts and showed the opposite effect for C. suchus counts. We also found that fishing encounter rate had a significant negative effect on C. suchus counts. Interestingly, survey repetition did not generally affect wariness for either species, though there was some indication that at least M. cataphractus was more wary by the fourth replicate. These results are informative for designing future survey and monitoring protocols for these threatened crocodylians in West Africa and for other endangered crocodylians globally.
format	article
author	Michel N. Ahizi Christine Y. Kouman Allassane Ouattara N’Dri Pascal Kouamé Azani Dede Emilie Fairet Matthew H. Shirley
author_facet	Michel N. Ahizi Christine Y. Kouman Allassane Ouattara N’Dri Pascal Kouamé Azani Dede Emilie Fairet Matthew H. Shirley
author_sort	Michel N. Ahizi
title	Detectability and impact of repetitive surveys on threatened West African crocodylians
title_short	Detectability and impact of repetitive surveys on threatened West African crocodylians
title_full	Detectability and impact of repetitive surveys on threatened West African crocodylians
title_fullStr	Detectability and impact of repetitive surveys on threatened West African crocodylians
title_full_unstemmed	Detectability and impact of repetitive surveys on threatened West African crocodylians
title_sort	detectability and impact of repetitive surveys on threatened west african crocodylians
publisher	Wiley
publishDate	2021
url	https://doaj.org/article/15dc090bf64a428ea12950998391e79f
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Detectability and impact of repetitive surveys on threatened West African crocodylians

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