Diversité et distribution des tortues marines dans le delta du Niger, Nigeria

Diversité et distribution des tortues marines dans le delta du Niger, Nigeria. - Des recherches ont été conduites en 2007 et 2008 le long de la côte du delta du Niger (Nigeria) sur la diversité et la distribution des tortues marines. Cinq espèces ont été identifiées comme visitant les côtes nigérianes, en particulier les plages sableuses d'Akassa, Brass, Bonny et Andoni. Chelonia mydas fut l'espèce la plus communément rencontrée; Lepidochelys olivacea et Dermochelys coriacea se sont avérées répandues dans toutes les stations inventoriées. En revanche Eretmochelys imbricata et Caretta caretta n'ont que très occasionnellement été rencontrées. Les eaux nigérianes peuvent constituer des zones importantes pour la conservation des tortues marines, plus particulièrement pour Dermochelys coriacea, mais des études plus détaillées sont nécessaires pour mieux évaluer l'abondance de ces espèces

Variation de la composition des communautés de reptiles dans divers types de plantations dans le Sud-Est du Nigéria

Despite many studies of reptile community composition in Africa, no studies document the variation of reptile assemblages across different plantation types. Here, we document the community composition (richness, taxonomic composition, dominance, evenness) in relation to seasonality in eight different plantation types (from cassava-yam to banana-plantain, and from cacao to mixed orchards), and at three distinct study areas in the River Niger Delta of southern Nigeria. Our study showed that the community composition of reptiles did not differ significantly across plantation types in terms of species diversity and richness during the wet season, but it did so during the dry season (possibly as a consequence of survey effects). A few highly dominant lizard species (Agama agama and Trachylepis affinis) constituted the great majority of the specimens encountered during field work. Some snake species, although usually not very abundant (in terms of relative number) were observed in nearly all sites. Typical forest specialists may enter plantations, but they were never abundant there. Tortoises did not occur in any plantations. Diversity indices and multivariate sets of analyses revealed minor differences among study areas and across plantation types in terms of community composition patterns. However, some types of monoculture plantations had higher dominance and lower evenness values than mixed orchards (= poly-culture farms), showing that monocultures provided least quality habitats for reptile communities than poly-culture farms, favoring few species due to the relatively homogeneous niche availability. Overall, a clear process of biotic homogenization, with increases in dominance, was clearly observed at all sitesEn dépit de leur nombre élevé aucune des études de la composition des communautés de reptiles africains ne renseigne de manière comparative sur les peuplements de reptiles dans divers types de plantations. Nous présentons ici la composition (richesse, composition taxinomique, dominance, équitabilité) de ces communautés en fonction de la saison dans huit types de plantations (de manioc-yam à banane plantain et de la cacaoyère aux vergers mixtes) et trois zones d’étude distinctes dans le delta du Niger dans le sud du Nigéria. Notre étude a montré que la composition des peuplements de reptiles ne diffèrerait pas de manière significative selon le type de plantation en termes de richesse et de diversité spécifiques durant la saison des pluies mais le ferait en saison sèche (peut-être une conséquence des effets de l’échantillonnage). Un petit nombre d’espèces dominantes de lézards (Agama agama et Trachylepis affinis) ont fourni la grande majorité des spécimens rencontrés durant la période d’étude. Quelques espèces de serpents, quoique en général pas très abondantes (en termes d’abondances relatives), furent observées dans presque tous les sites. Des espèces typiquement forestières peuvent se montrer dans les plantations mais sans jamais y être abondantes. Des tortues n’ont été trouvées dans aucune plantation. Des indices de diversité et des analyses multivariées n’ont révélé que de petites différences entre les zones d’étude et entre les types de plantations en termes de patrons de composition du peuplement. Toutefois, quelques types de monocultures présentaient une plus grande dominance et une plus faible équitabilité que les vergers mixtes (polycultures), suggérant que les monocultures offriraient aux reptiles des habitats de moindre qualité que les polycultures, favorisant moins d’espèces en raison d’une disponibilité de niches relativement homogène. D’une manière générale un processus d’homogénéisation biotique, avec des accroissements de dominance, a été clairement observé sur tous les site

Seasonal incidence, sex-ratio, and population cohorts of hinge-back tortoises (genus Kinixys) in the wild and in bush-meat markets of the Niger delta, southern Nigeria: Are human predation effects random ?

Three species of hinge-back tortoises (Kinixys belliana nogueyi, Kinixys erosa, and Kinixys homeana) are found in the forest-plantation mosaics of the Niger Delta region, in south-eastern Nigeria, where they are actively hunted by local people communities for subsistence and traditional medicine. In this paper, the numbers of tortoises traded in bush-meat markets is contrasted to the numbers of tortoises found in the wild, to test whether the pressure of human hunters is random, or if it is biased towards a specifie sex, population cohort (adults or juveniles), or monthly period. We concluded that: (1) the relative monthly intensity of above-ground activity of tortoises strongly influenced the relative monthly numbers of traded specimens in the bush-meat markets ; (2) the pressure of local people on free-ranging tortoises is similar to that of a generalist predator, without apparent differences between species or sexes; (3) the juveniles of both K. homeana and K. erosa were the only category of animais which were not preyed upon by humans depending on their local availabilityTrois espèces de tortues (Kinixys belliana nogueyi, Kinixys erosa et Kinixys homeana) se rencontrent dans les mosaïques forêt-plantations du delta du Niger, dans le sud-est du Nigéria où elles sont activement chassées par les populations humaines locales qui les utilisent pour leur subsistance et leur médecine traditionnelle. Dans cet article, nous confrontons les effectifs de tortues vendues sur les marchés de viande de brousse à ceux observés dans la nature, pour voir si la pression de chasse est aléatoire ou orientée vers un sexe ou une cohorte (adultes ou jeunes) particulière ou effectuée durant une période donnée. Il apparaît que (1) l'intensité relative de l'activité mensuelle terrestre des tortues influence fortement le nombre relatif de spécimens mensuellement vendus sur les marchés ; (2) la pression de chasse exercée par les populations humaines locales correspond à celle d'un prédateur généraliste, sans différence apparente entre les espèces et les sexes des tortues capturées ; (3) les juvéniles de K. homeana et de K. erosa sont les seules catégories d'animaux que les humains ne chassent pas en fonction de leur disponibilité locale

Structure and diversity of fish communities in man-made ponds of the Niger Delta (southern Nigeria)

1. A survey of eight local earthen hand-dug ponds located within the freshwater swamps of a Niger Delta area (southern Nigeria) was conducted over a period of 3 months. A total of 4,313 fishes representing 19 species from 12 families were recorded.2. The most abundant species was Xenomystus nigri (905 individuals), whereas the least common was Protopterus annectens (13). Cichlidae and Clariidae counted three species each, whereas Anabantidae, Hepsetidae, Mochokidae, Protopteridae, Phractolaemidae, Malapteruridae and Gymnarchidae were represented by a single species each.3. A lotic species, Synodontis sp., was recorded possibly as a result of the episodic flood of 2012.4. The Engenni swamps harbour a moderately diverse ichthyofauna. Regulations should be put in place to further enhance the fisheries potential of these local ponds

Exploring the main threats to the threatened African spurred tortoise Centrochelys sulcata in the West African Sahel

AbstractThe African spurred tortoiseCentrochelys sulcatais the second largest terrestrial turtle, with a scattered distribution across the West African Sahel. This species is threatened and declining consistently throughout its range, but little is known about the causes of its decline. It has been hypothesized that the decline is attributable to (1) competition with domestic cattle, (2) wildfire, and (3) the international pet trade. We conducted a series of analyses to investigate these three causes. Hypotheses 1 and 2 were analysed using a spatially explicit approach, using a database of the Food and Agriculture Organization of the United Nations and logistic regression modelling; hypothesis 3 was tested by analysing the CITES trade database for 1990–2010. We found a significant negative correlation between intensity of grazing (expressed as density of cattle, km−2) and the presence of spurred tortoises, and this negative effect increased when coupled with high fire intensity, whereas wildfires alone did not have a significant influence on the species' distribution at the global scale. There was a decrease in the annual export of wild individuals for the pet trade after the introduction of export quotas by country and by year, but trade data must be considered with caution

La viande de brousse : des enquêtes révèlent des points de controverse sur la dynamique de son commerce au Nigéria

Sur la base d’enquêtes dans le sud du Nigéria, cet article examine (i) si la viande de brousse est toujours une source cruciale de protéines pour les communautés locales, (ii) si elle est toujours culturellement bien justifiée et (iii) si, selon les préférences des consommateurs, des valeurs différentes sont attribuées aux divers types d’espèces constituant cette viande de brousse. De plus, cet article fournit des informations sur la question de savoir (iv) si le commerce de la viande de brousse épuise localement les populations des espèces ciblées, et (v) si la disparition sur les marchés de grands animaux est signe de leur extermination locale. Une combinaison d’entretiens avec des hommes et des femmes de différentes classes d’âge, incluant des chasseurs, consommateurs et vendeurs, a été conduite dans divers localités nigérianes correspondant à différentes conditions d’habitat et de caractéristiques socio-économiques et ethniques. Les résultats suggèrent que la consommation de viande de brousse, en particulier dans les zones urbaines, n’a pas une grande valeur de subsistance, sauf pour une petite sous-section de la communauté. De fait, même dans les zones rurales, moins de 30 % des personnes de moins de 50 ans interrogées ont répondu consommer fréquemment de la viande de brousse. L’importance culturelle de la viande de brousse a substantiellement diminué dans les années récentes, comme en témoigne le fait que (i) cette source de nourriture a été rapidement abandonnée durant la crise d’Ebola en 2014 et (ii) la plupart des personnes interrogées ont affirmé n’en manger que rarement voire pas du tout. Les données recueillies vont dans le sens de ce que le prix d’une carcasse serait principalement déterminé par la taille de l’animal et non pas par la préférence des consommateurs. L’utilisation et le commerce de la viande de brousse peuvent certainement épuiser localement les populations des espèces animales ciblées. Néanmoins, il n’y a toujours pas suffisamment de preuves empiriques de la notion selon laquelle quand les grands animaux disparaissent des marchés cela signifierait que leurs populations auraient été considérablement épuisées voire exterminées. De fait, sur la base d’éléments culturels exposés par les chasseurs interrogés, il semblerait que cette notion soit erronée, du moins en ce qui concerne les régions ouest-africaines les plus riches et les plus économiquement dynamiques. Il est conseillé à ceux qui étudient la viande de brousse d’explorer plus en profondeur la flexibilité culturelle des communautés humaines avant de généraliser des conclusions, évitant ainsi d’extrapoler à grande échelle des conclusions insuffisamment fondées car basées sur des données collectées à très petite échelle spatiale et durant de courtes périodes de temps.Using questionnaire surveys in southern Nigeria, this paper explores whether: (i) bushmeat is still a crucial source of animal protein for local communities; (ii) is still culturally very relevant; and (iii) if people value differently the various kinds of bushmeat species because of customer preferences. In addition, this paper provides information on whether (iv) the bushmeat trade locally depletes target game species; and (v) whether the disappearance of large animals from the markets would indicate their local extirpation from the wild. A combination of interviews was carried out with both men and women of different age classes including hunters, consumers and sellers, from different Nigerian locations with different habitat conditions, socio-economic and ethnic characteristics. Results of these interviews suggest that the consumption of bushmeat has little subsistence value, especially in urban areas, except for a small sub-section of the community. Indeed, even in rural areas less than 30 % of the interviewees of less than 50 years age answered that they frequently eat bushmeat. Cultural importance of bushmeat decreased substantially in recent years, as shown by that (i) this food source was quickly abandoned by people during the 2014 Ebola crisis, and (ii) most of questionnaire respondents affirmed that they would have eaten bushmeat only rarely or even not at all. There was support for the notion that the price of a carcass was mainly determined by the animal size and not by the consumer preference. Bushmeat utilization and trade may certainly deplete target animal species at the local scale. Nonetheless, there is still no sufficient empirical evidence for the notion that, when large animals disappeared from the markets, it meant that their populations were heavily depleted or even extinct. Indeed, based on cultural elements highlighted by interviewed hunters, there is evidence that this notion may be wrong, at least in the richest and economically more dynamic regions of West Africa. It is advised that bushmeat studies should explore more in depth the cultural flexibility of human communities before drawing generalized conclusions, thus avoiding unsupported large-scale conclusions based on data collected at a very small spatial scale and during short time periods

Bushmeat consumption in large urban centres in West Africa

Bushmeat consumption in large Sub-Saharan African cities is perceived as a major threat to the conservation of many species because their considerable population sizes can generate a significant demand for bushmeat. The study of the effect of age, sex and geographic location in bushmeat eating in African cities may offer valuable insights on which population groups to target in behaviour change campaigns. Using 2,040 interviews in six West African cities from four countries, in forest and savannah settings, we analysed the differences between age and sex in people’s frequency of bushmeat consumption. Overall, we found similar patterns in all sampled cities. As many as 62.2 % males and 72.1% females replied that they ‘would not eat bushmeat at all’, though only 12.8% males and 8.8% females mentioned they regularly ate bushmeat. Younger generations of both sexes answered that they ‘would never eat bushmeat’ more often than older age groups, independently of their city of origin. These trends are encouraging though further research needs to be undertaken to find out whether bushmeat volumes consumed in cities are unsustainable and having a serious impact of prey populations

Bushmeat consumption in large urban centres in West Africa

Bushmeat consumption in large Sub-Saharan African cities is perceived as a major threat to the conservation of many species because their considerable population sizes can generate a significant demand for bushmeat. The study of the effect of age, sex and geographic location in bushmeat eating in African cities may offer valuable insights on which population groups to target in behaviour change campaigns. Using 2,040 interviews in six West African cities from four countries, in forest and savannah settings, we analysed the differences between age and sex in people’s frequency of bushmeat consumption. Overall, we found similar patterns in all sampled cities. As many as 62.2 % males and 72.1% females replied that they ‘would not eat bushmeat at all’, though only 12.8% males and 8.8% females mentioned they regularly ate bushmeat. Younger generations of both sexes answered that they ‘would never eat bushmeat’ more often than older age groups, independently of their city of origin. These trends are encouraging though further research needs to be undertaken to find out whether bushmeat volumes consumed in cities are unsustainable and having a serious impact of prey populations

Impact of COVID-19 on wild meat trade in Nigerian markets

Wild meat plays a crucial role in the food security and cash income of subsistence hunters in the tropics and subtropics in Africa, South America, and SE Asia (Coad et al., 2019; Fa et al., 2022). This meat is regularly traded in markets in many towns and cities (see Fa et al., 2019). In Nigeria, the amount of meat sold from most species crashed dramatically after the Ebola virus outbreak in 2014, highlighting the awareness of the general public of a link between disease risk and wild meat (Akani et al., 2015; Funk et al., 2021). The opportunities for zoonotic spill-over have increased in parallel with the increase of the intensity and extent of bushmeat trade over the last decades (Karesh & Noble, 2009). The report by UNEP, International Livestock Research Institute (2020) on preventing the next pandemic lists increasing human demand for animal protein among seven human-mediated factors as the most likely driving the emergence of zoonotic diseases, which includes wild meat hunting

Nesting trees used by a pest bird (Village Weaver, Ploceus cucullatus): a large field survey suggests further human conflicts with local stakeholders in Southern Nigeria

The village weaver (Ploceus cucullatus) is a common colonial nesting bird widespread throughout Sub-Saharan Africa. It is known to weave its nests from leaf strips from a variety of tree species (mainly coconuts trees, oil palm trees) associated with human settlement areas, grasses, and other available plants. In this regard, this bird was considered a pest for its impact on different economic activities. Although extensive literature is already available on the parasitic role of village weavers, there is still a lack of analytical data that outlines which tree species are used for nesting and in what proportion, as well as the related implications in terms of economic impacts. Here, we carried out the first comprehensive arrangement of trees used by this species for nesting in Southern Nigeria (West Africa), checking for possible different impacts on stakeholders. In April 2021, we searched for village weaver nesting in 95 sites in 77 communities from 24 local government areas in Southern Nigeria, during 14 field surveys. Within each site, we collected GPS coordinates and counted the number of active nests, nesting birds and occupied trees. We recorded a total of 5,776 nests and 2,140 birds in 94 plants belonging to 23 tree species selected for nesting. Oil palm (Elaeis guineensis; n = 45) was the most used tree species, as 2,990 (51.77%) nests and 873 (40.79%) birds were recorded. Our results indicate the preference for nesting on trees used by stakeholders belonging to agricultural (palm farmers), touristic (operators) and energy (gas flare stations) sectors with economic implications about the conflict with this pest species