Distribution and relative abundance of forest duikers in Dassioko Sud Forest Reserve (coastal Côte d'Ivoire)

Abstract

Context Duikers play a vital role in maintaining forest ecosystems, as both seed dispersers and prey. In West Africa, duikers are also an important source of food and income; however, it is likely that some species are now being hunted at unsustainable levels. So as to contribute to duiker conservation, we used line-transect data and additional information on dung and track counts to estimate relative abundance and establish distribution patterns of forest duikers in Côte d’Ivoire’s Dassioko Sud Forest Reserve (DSFR), a poorly known, remnant coastal rainforest. We also collected basic information on hunting pressure. Methods Forest duiker counts were made twice per month from July 2013 to March 2014 on six line transects of varying lengths (5.6–6.7km) and in different regions of the DSFR, representing different habitat types. The number of sightings per kilometre walked, defined as ‘encounter rate’, was used to compute an index of relative abundance. We recorded all evidence of poachers and used these data to generate a poaching index (# poaching signs per kilometre) for different habitat types. Key results The DSFR has lost three of seven total forest duiker species and populations of the four remaining species are declining. Encounter rates were greatest for Philantomba maxwellii (0.46 indices km–1) and accounted for 68% of total encounters. Cephalophus niger, C. dorsalis and C. silvicultor were encountered at similar (0.07 indices km–1) but much lower rates. For all species, mean encounter rates were highest in degraded forest (0.38–0.73 indices km–1), followed by secondary (0.2–0.44 indices km–1) and primary (0.19–0.44 indices km–1) forest. Conclusions Of the four forest duiker species still present in the DSFR, the black, bay and yellow-backed duikers are the most affected by anthropogenic pressures. Duiker abundance in the DSFR varies with habitat type. This variation is apparently influenced by differences in forest structure, poaching pressure and proximity to villages. Implications The study provides baseline data for future managing of ungulate populations in the DSFR. We recommend that a biomonitoring study of duiker populations be initiated immediately to help determine population trends, investigate habitat preferences, and help curb illegal hunting activities in this important forest reserve.

État des Lieux de la Faune Sauvage Mammalienne dans le Département de Sipilou, Ouest de la Côte d’Ivoire

“…Cette richesse spécifique observée sur le terrain est relativement faible comparativement aux 27 espèces de mammifères obtenues au Parc National du Mont Sangbé (Kouakou et al, 2021), situé dans la même zone géographique. La faible richesse spécifique des mammifères dans la zone d'étude pourrait être liée d'une part à la courte période de l'étude et d'autre part à la pression humaine qui a dû rendre de nombreuses espèces cryptiques (Gonedelé et Yao, 2016). Les modifications des caractéristiques des habitats naturels dues aux activités humaines impactent non seulement la diversité, l'abondance et la distribution des espèces de mammifères mais, peuvent entrainer leur extinction au niveau local (Andrade-Núñez et Aide, 2010 ; Legese et al, 2019).…”

“…De ce fait, plusieurs études ont été conduites sur la faune mammalienne en Côte d'Ivoire. La plupart de ces études a été réalisée dans des aires protégées telles que les parcs nationaux du Banco (Bitty et al, 2013), de la Marahoué (Kadjo et al, 2014), de Taï (Diarrassouba et al, 2019b ;Monket et al, 2022), d'Azagny (Koffi et al, 2022) et les forêts classées de Mabi et Yaya (Akpatou et al, 2018), de Dassioko (Yao et al, 2016). Le constat est le même dans la région du Tonkpi où la majorité des travaux scientifiques sur la faune mammalienne de la région est également focalisée sur le parc national du Mont Sangbé (Kouakou et al, 2021 ;N'guessan et al, 2021).…”

Update the survey of the Populations of Artiodactyls and threats in the Dassioko Sud Forest Reserve, Côte d’Ivoire

“…The climate of the region is equatorial, characterised by heavy rainfall and annual temperatures that range between 20°C and 33°C. The vegetation of the reserve is evergreen rainforest, typical of that within the Guinean forest block (Yao et al, 2018;Kouamé and Zoro Bi, 2010).…”

“…In Côte d'Ivoire forest reserves also called classified forests are considered as protected areas which are supposed to be the refugee of the wildlife, are partly or totally occupied by people that convert the natural habitat of the wildlife into farms since the politic and military crisis of 2010 (Bitty et al, 2015). We previously conducted survey in several forests of Côte d'Ivoire in order to evaluate the conservation state of the wild (Bitty et al, 2015;Yao et al, 2018). These surveys highlighted the importance of the Dassioko Sud Forest Reserve in terms of biodiversity (Gonédélé et al, 2014;Yao et al, 2018).…”

“…We previously conducted survey in several forests of Côte d'Ivoire in order to evaluate the conservation state of the wild (Bitty et al, 2015;Yao et al, 2018). These surveys highlighted the importance of the Dassioko Sud Forest Reserve in terms of biodiversity (Gonédélé et al, 2014;Yao et al, 2018). Furthermore, the Dassioko Forest harbours several threatened species that include the West African Elephant, Loxodonta africana the white-napped Mangabey, Cercocebus lunulatus, the white breast Guineafowl (Agelastes meleagrides).…”