Estrategia vital y distribución ecológica de camaleones (Reptilia, Chamaeleonidae) de los bosques húmedos de Nígeria: implicaciones en la conservación

Five species of chameleons were observed in the continuous forest zone of southern Nigeria: Chamaeleo gracilis gracilis Hallowell, 1842, Chamaeleo owenii Gray, 1831, Chamaeleo cristatus Stutchbury, 1837, Chamaeleo wiedersheimi Nieden, 1910, and Rhampholeon spectrum (Bucholz 1874). Many original locality records are presented for each species. One species is apparently rare and confined to montane habitats (C. wiedersheimi), another species is relatively common and its habitat is generalist (C. gracilis), and the other three species are vulnerable and limited to specific micro–habitats. Female R. spectrum had clutch sizes of two eggs each and exhibited a prolonged reproductive season with oviposition likely occurring during the late phase of the dry season. Females of both C. cristatus (clutch sizes: 11–14 eggs) and C. owenii (clutch sizes: 15–19 eggs) have a shorter reproductive season with oviposition occurring most probably at the interphase between the end of the wet season and the onset of the dry season, and female C. gracilis (clutch sizes: 14–23 eggs) appeared to exhibit two distinct oviposition periods (one at the interphase between the end of the wet season and the onset of the dry season, and one at the peak phase of the dry season). Diets of four sympatric species of chameleons consisted almost exclusively of arthropods. There were significant inter–group differences at either intra–specific level (with the females of the two best studied species, i.e. R. spectrum and C. gracilis, having a wider food niche breadth than males) or inter–specific level (with a continuum of dietary specialization from the less generalist (C. cristatus) to the more generalist (C. gracilis). However, “thread–trailing” experiments indicated that activity patterns of Nigerian chameleons were relatively similar among species. The overall abundance of chameleons (as estimated from the number of specimens observed in the time unit of field effort) was relatively similar in three contrasted habitat types, but lizards were more abundant in the mature secondary forest. When greatly altered by massive logging activity, the overall abundance of chameleons in the mature secondary forest habitat declined only slightly, whereas the species diversity declined drastically. This was an effect of (i) the simultaneous extinction of three of the four species originally present in the forest plot, and of (ii) the rapid increase in abundance of a single species (C. gracilis) as a response to habitat alteration. The conservation implications of all these data are also discussed.Se observaron cinco especies de camaleones en la zona de bosque ininterrumpido del sur de Nigeria: Chamaeleo gracilis gracilis Hallowell, 1842, Chamaeleo owenii Gray, 1831, Chamaeleo cristatus Stutchbury, 1837, Chamaeleo wiedersheimi Nieden, 1910 y Rhampholeon spectrum (Bucholz 1874). Se presentan muchos registros de localidad originales para todas las especies. Una especie es aparentemente rara y está confinada a los hábitats montañosos (C. wiedersheimi), otra especie es relativamente común y generalista en cuanto al hábitat (C. gracilis), y las otras tres especies son vulnerables y están limitadas a microhábitats específicos. El tamaño de cada puesta de la hembra de R. spectrum fue de dos huevos, mostrando una prolongada estación reproductora con oviposición durante la última fase de la estación húmeda. Las hembras de C. cristatus (tamaño de puesta: 11–14 huevos) y C. owenii (tamaño de puesta: 15–19 huevos) tienen una estación reproductora más corta y la oviposición se da con mayor probabilidad en la interfase entre el final de la estación húmeda y el inicio de la estación seca, y la hembra de C. gracilis (tamaño de puesta: 14–23 huevos) presenta dos periodos distintos de oviposición (uno en la interfase entre el final de la estación húmeda y el inicio de la estación seca y el otro durante el período más seco de la estación seca). Las dietas de cuatro especies simpátricas de camaleones consistían prácticamente de forma exclusiva en artrópodos. Había diferencias significativas dentro del grupo tanto a nivel intraespecífico (con las hembras de las dos especies mejor estudiadas, es decir R. spectrum y C. gracilis, con un extenso nicho alimentario más amplio que los machos) o interespecíficas (con una continua especialización alimentaria desde los menos generalistas (C. cristatus) a los más generalistas (C. gracilis). Sin embargo los experimentos “thread–trailing” indican que los patrones de actividad de los camaleones de Nigeria eran relativamente similares entre especies. La abundancia de camaleones (estimada a partir de el número de especímenes observado en la unidad de tiempo de esfuerzo de campo) era relativamente similar en tres tipos de hábitats contrastados, pero el bosque secundario maduro fue el hábitat donde los lagartos fueron más abundantes. En cuanto al hábitat del bosque secundario, cuando estaba fuertemente alterado por una fuerte explotación forestal, la abundancia de camaleones disminuía sólo ligeramente, mientras que la diversidad de especies disminuía de forma drástica. Esto era debido a: (i) la extinción simultánea de tres de las cuatro especies originalmente presentadas en el bosque, y (ii) el rápido incremento en abundancia de una única especie (C. gracilis) como respuesta a una alteración del hábitat. Se discuten las implicaciones de estos datos sobre la conservación

Helminth community structure and diet of three Afrotropical anuran species: a test of the interactive-versus-isolationist parasite communities hypothesis

The interactive-versus-isolationist hypothesis predicts that parasite communities should be depauperated and weakly structured by interspecific competition in amphibians. A parasitological survey was carried out to test this hypothesis using three anuran species from Nigeria, tropical Africa (one Bufonidae; two Ranidae). High values of parasite infection parameters were found in all three species, which were infected by nematodes, cestodes and trematodes. Nonetheless, the parasite communities of the three anurans were very depauperated in terms of number of species (4 to 6). Interspecific competition was irrelevant in all species, as revealed by null models and Monte Carlo permutations. Cluster analyses revealed that, in terms of parasite community composition, the two Ranidae were similar, whereas the Bufonidae was more different. However, when prevalence, intensity, and abundance of parasites are combined into a multivariate analysis, each anuran species was clearly spaced apart from the others, thus revealing considerable species-specific differences in terms of their parasite communities. All anurans were generalists and probably opportunistic in terms of dietary habits, and showed no evidence of interspecific competition for food. Overall, our data are widely consistent with expectations driven from the interactive-versus-isolationist parasite communities hypothesis

Macro-habitat preferences by the African manatee and crocodiles – ecological and conservation implications

African manatees (<i>Trichechus senegalensis</i>) and crocodiles are threatened species in parts of their range. In West Africa, crocodiles may constitute the main predators for manatees apart from humans. Here, we explore the macro-habitat selection of manatees and two species of crocodiles (West African crocodiles <i>Crocodylus suchus</i> and dwarf crocodile <i>Osteolaemus tetraspis</i>) in the Niger Delta (Nigeria), testing the hypotheses that (i) manatees may avoid crocodiles in order to minimize risks of predation, and (ii) the two crocodile species do compete. The study was carried out between 1994 and 2010 with a suite of different field techniques. We observed that the main macro-habitat types were freshwater rivers and coastal lagoons for manatees, mangroves for West African crocodiles, and rivers and creeks for dwarf crocodiles, with (i) the three species differing significantly in terms of their macro-habitat type selection, and (ii) significant seasonal influence on habitat selection of each species. Null models for niche overlap showed a significantly lower overlap in macro-habitat type use between manatee and crocodiles, whereas the two crocodiles were relatively similar. Null model analyses did not indicate any competitive interactions between crocodiles. On the other hand, manatees avoided macro-habitats where crocodiles, and especially West African crocodiles, are abundant

Macro-habitat preferences by the African manatee and crocodiles – ecological and conservation implications

Abstract. African manatees (Trichechus senegalensis) and crocodiles are threatened species in parts of their range. In West Africa, crocodiles may constitute the main predators for manatees apart from humans. Here, we explore the macro-habitat selection of manatees and two species of crocodiles (West African crocodiles Crocodylus suchus and dwarf crocodile Osteolaemus tetraspis) in the Niger Delta (Nigeria), testing the hypotheses that (i) manatees may avoid crocodiles in order to minimize risks of predation, and (ii) the two crocodile species do compete. The study was carried out between 1994 and 2010 with a suite of different field techniques. We observed that the main macro-habitat types were freshwater rivers and coastal lagoons for manatees, mangroves for West African crocodiles, and rivers and creeks for dwarf crocodiles, with (i) the three species differing significantly in terms of their macro-habitat type selection, and (ii) significant seasonal influence on habitat selection of each species. Null models for niche overlap showed a significantly lower overlap in macro-habitat type use between manatee and crocodiles, whereas the two crocodiles were relatively similar. Null model analyses did not indicate any competitive interactions between crocodiles. On the other hand, manatees avoided macro-habitats where crocodiles, and especially West African crocodiles, are abundant

The conservation status of West African vultures: an updated review and a strategy for conservation

The vulture populations in West Africa are undergoing dramatic decline over the last 30 years. Their particular ecology and sociality makes them vulnerable to various risks, including environmental changes, poisoning and bioaccumulation of toxic substances from agricultural products, pesticides, and veterinary drugs used in cattle livestock. In addition, these birds are subject to direct persecution for the trade of products used in traditional medicine. This manuscript analyzes the conservation status of eight vulture species in West Africa and the threats affecting their survival. In order to assess the conservation status of vultures in West Africa, this paper analyzes all the available literature that has been published in scientific peerreviewed journals, including also technical reports and unpublished reports related to the whole West African region. Overall, and despite the high risk of extinction facing several vulture species all throughout the world, our literature surveys revealed that the scientific papers on the conservation of West African vultures are relatively few. Therefore, due to limited available literature, the main causes of vulture declines in West Africa remain relatively unclear. Apparently, all African vultures suffer from similar threats, especially poisoning, habitat alteration and conversion to agro-pastoral systems, loss of wild ungulates leading to a reduced availability of carrion, hunting for trade, for use in traditional medicine and bushmeat, persecution and human disturbance. Our review also addresses future steps that are needed for reversing the negative population trend of their free-ranging populations, including some specific conservation measures that are proposed to mitigate their decline

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

Understanding the influence of non-wealth factors in determining bushmeat consumption: results from four West African countries

The meat of wild animals (bushmeat) is consumed extensively in many tropical regions. Over the past few decades bushmeat consumption has greatly increased, threatening the survival of some hunted species and the supply of animal protein to countless numbers of people. Understanding patterns of bushmeat consumption is thus vital to ensure the sustainable use of this resource. Although the economic drivers of bushmeat consumption has been well studied, non-wealth correlates have been poorly considered. Here, we analyse how factors such as age and gender influence bushmeat consumption in four West African countries, within the Guinean forests (Togo and Nigeria) and Sahel (Burkina Faso and Niger). We interviewed a total of 2,453 persons (1,253 urban, 1,200 in rural areas) to determine frequency of consumption of bushmeat as well as main species eaten. We found significant differences in bushmeat consumption between rural and urban areas in all four countries. In particular, the proportion of persons not consuming any bushmeat was highest in urban areas. Gender differences in bushmeat consumption was not generally important but young people consistently avoided eating bushmeat, especially in Togo and Nigeria, and in urban areas. The complicated interplay between tradition and evolution of social systems (especially the trends towards westernization) may explain the different perceptions that people may have towards consuming bushmeat in the four studied countries. In addition, we found considerable variation in types of bushmeat eaten, with antelopes and large rodents eaten by the great majority of interviewees, but bats, monkeys, and snakes being avoided, especially in urban settlements

The environmental impacts of palm oil in context

Delivering the Sustainable Development Goals (SDGs) requires balancing demands on land between agriculture (SDG 2) and biodiversity (SDG 15). The production of vegetable oils, and in particular palm oil, illustrates these competing demands and trade-offs. Palm oil accounts for 40% of the current global annual demand for vegetable oil as food, animal feed, and fuel (210 million tons (Mt)), but planted oil palm covers less than 5-5.5% of total global oil crop area (ca. 425 Mha), due to oil palm’s relatively high yields5. Recent oil palm expansion in forested regions of Borneo, Sumatra, and the Malay Peninsula, where >90% of global palm oil is produced, has led to substantial concern around oil palm’s role in deforestation. Oil palm expansion’s direct contribution to regional tropical deforestation varies widely, ranging from 3% in West Africa to 47% in Malaysia. Oil palm is also implicated in peatland draining and burning in Southeast Asia. Documented negative environmental impacts from such expansion include biodiversity declines, greenhouse gas emissions, and air pollution. However, oil palm generally produces more oil per area than other oil crops, is often economically viable in sites unsuitable for most other crops, and generates considerable wealth for at least some actors. Global demand for vegetable oils is projected to increase by 46% by 20509. Meeting this demand through additional expansion of oil palm versus other vegetable oil crops will lead to substantial differential effects on biodiversity, food security, climate change, land degradation, and livelihoods. Our review highlights that, although substantial gaps remain in our understanding of the relationship between the environmental, socio-cultural and economic impacts of oil palm, and the scope, stringency and effectiveness of initiatives to address these, there has been little research into the impacts and trade-offs of other vegetable oil crops. 65 Greater research attention needs to be given to investigating the impacts of palm oil production 66 compared to alternatives for the trade-offs to be assessed at a global scale

An indirect assessment of the effects of oil pollution on the diversity and functioning of turtle communities in the Niger Delta, Nigeria

There are many documented cases of oil spillage in the Niger Delta region, southern Nigeria (West Africa). Due to both habitat characteristics and omnivorous habits, the freshwater turtles are important vertebrates species in the trophic chain. They are therefore considered to play a significant role as ecological indicators for areas subjected to oil spillage events. The aim of this study was to evaluate the effects of oil spillage and consequent pollution on the abundance, complexity and functioning of freshwater turtle communities of the Niger Delta, by comparing the turtle fauna found in two areas with similar environmental characteristics, one unpolluted and the other polluted by a case of oil spillage in 1988. A total of 510 turtle specimens belonging to four different species (Trionyx triunguis, Pelusios castaneus, Pelusios niger, and Pelomedusa subrufa) were captured in the unpolluted area, whereas 88 specimens, from two different species (P. castaneus and P. niger) were captured in the polluted area. The dominant species was P. castaneus followed by P. niger in the unpolluted area, and P. niger in the polluted area. A marked shift in habitat use was observed in one species (P. niger) after the oil spillage event. This study revealed both direct and indirect effects of oil pollution on the complexity and habitat use of Nigerian freshwater communities of turtles. The main direct effect was a considerable reduction in the specific diversity of the turtles; 50% of species were lost after oil spillage and there was a very strong decline in the numbers of turtle specimens also for those species which were able to survive the catastrophic pollution event. The shift in habitat use after oil spillage by P. niger may have a significant effect on the long-term persistence of this species, independently of the pollution effects of the oil spillage event, because it considerably reduced habitat niche separation between this species and the closely related P. castaneus, a potential competitor. It is therefore stressed that eco-ethological modifications in populations of animals subjected to catastrophic events such as oil pollution should be taken into account when evaluating the long-term effects of these devastating phenomen