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The ghost of a recent invasion in the reduced feeding rates of spitting cobras during the dry season in a rainforest region of tropical Africa?
Abstract
Two species of cobras (Naja melanoleuca and Naja nigricollis) are known to occur in south eastern Nigeria, where much of the pristine rainforest surface has been felled in the last thirty years, and where the actual landscape is generally constituted by a mosaic of farmlands, plantations, suburban areas, with a few remnant forest fragments. In this region, Naja nigricollis is currently extending its range, especially by exploiting recently deforested areas. Based on the known general distribution range of this species and on the available literature data, it appears that Naja nigricollis has been colonizing the forested region of south eastern Nigeria, starting from the relatively arid savannas of central Nigeria, where this species aestivates during the driest months. In the forest region, however, snakes do not need to aestivate during the dry season. Nevertheless, whereas Naja melanoleuca has a foraging activity extended all-the-year round, Naja nigricollis reduces feeding rates during the dry months, although it does not suspend above-ground activity in these months. I suggest that rainforest spitting cobras suspend feeding during the dry months because their behaviour is just a ‘ghost’ of their recent past, when they were ‘normal’ spitting cobras of dry savana regions, which were thus constrained to aestivate during the dry season as it is the rule in this species in central and northern Nigeria. The ‘gost-of-the-past hypothesis’ seems to fit well with the ‘invading’ presence of Naja nigricollis in Nigerian areas where they were reported as rare or, even, absent, up to a few decades ago. Other hypotheses are discussed, and rejected.
... Cobras are known to be prey generalists feeding on a range of different taxa [33][34][35][36][37]. Amphibians, reptiles (particularly snakes), and mammals are common prey types of most Naja species [33,34,[36][37][38]. ...
... Cobras are known to be prey generalists feeding on a range of different taxa [33][34][35][36][37]. Amphibians, reptiles (particularly snakes), and mammals are common prey types of most Naja species [33,34,[36][37][38]. This broad diet across Naja species highlights their ecological plasticity and in part might explain their successful diversification across Africa and Asia. ...
... Further, these results indicate that the selectivity of a particular toxin class may vary from that of the overall diet, thus suggesting that some taxa are more vulnerable to a particular toxin type and thus this component of the venom may be used for a particular function. Consistent with this, the data on cobra crude venom and alpha-cobratoxin binding (Figures 1 and 2) highlight some significant preference to specific mimotopes that correlate with a major prey items but do not account for the full range of known prey items of Naja species [33][34][35][36][37]. Therefore, other toxins with different functions within the venom (e.g., coagulotoxic and myotoxic PLA2s) [42,43] may play an equally important role in biochemically immobilising different taxa types. ...
Prey-selective venoms and toxins have been documented across only a few species of snakes. The lack of research in this area has been due to the absence of suitably flexible testing platforms. In order to test more species for prey specificity of their venom, we used an innovative taxonomically flexible, high-throughput biolayer interferometry approach to ascertain the relative binding of 29 α-neurotoxic venoms from African and Asian elapid representatives (26 Naja spp., Aspidelaps scutatus, Elapsoidea boulengeri, and four locales of Ophiophagus hannah) to the alpha-1 nicotinic acetylcholine receptor orthosteric (active) site for amphibian, lizard, snake, bird, and rodent targets. Our results detected prey-selective, intraspecific, and geographical differences of α-neurotoxic binding. The results also suggest that crude venom that shows prey selectivity is likely driven by the proportions of prey-specific α-neurotoxins with differential selectivity within the crude venom. Our results also suggest that since the α-neurotoxic prey targeting does not always account for the full dietary breadth of a species, other toxin classes with a different pathophysiological function likely play an equally important role in prey immobilisation of the crude venom depending on the prey type envenomated. The use of this innovative and taxonomically flexible diverse assay in functional venom testing can be key in attempting to understanding the evolution and ecology of α-neurotoxic snake venoms, as well as opening up biochemical and pharmacological avenues to explore other venom effects. Key Contribution: Our results reveal the occurrence of prey-selective α-neurotoxicity in Afro-Asian elapids and that intraspecific and geographical differences of α-neurotoxic binding can be detected using this assay, making it well suited for future functional studies of α-neurotoxins.
... Two species of cobras are found in the forested regions of southern Nigeria: the forest cobra (Naja melanoleuca) and the spitting cobra (Naja nigricollis) (Politano, 1998;Luiselli et al. , 1998;Eniang & Luiselli, 2002). These two species are parapatric or even sympatric over a very wide area in southern Nigeria (in a belt of approximately 800 x 300 km), especially in those sites which have been just recently deforested Luiselli, 2001; and see Menzies, 1962Menzies, , 1966, for similar observations in Sierra Leone). However, the width of the overlap belt observed in Nigeria is certainly much surprising, as these two species are clearly different in terms of habitat requirements: the forest cobra is mainly linked to mature forests and swamp-forests and rarely enters into very altered habitats, whereas the spitting cobra is often found in highly disturbed habitats (including suburbs, plantations, farmlands), and is typical of savannas and open bushes (Spawls & Branch, 1997;. ...
... To examine these three points, 1 use the by far largest dataset avaïlable on the ecology of free-ranging afrotropical cobras avaïlable in the literature (see also Luiselli et al. , 1998Luiselli et al. , , 2002Luiselli, 2001). ...
... Methods used to survey the study area, capture cobras, and analyse their food items, are fully detailed in , and here 1 just present a brief sumrnary of it. Data presented here were partially published in Luiselli (2001) and in Luiselli et al. (2002), but much original new information is added in the present paper. ...
The region of continuous rainforest in southern Nigeria is inhabited by two species of cobras (Naja melanoleuca and N. nigricollis), and is nowadays subjected to devastating deforestation due to human activity (mainly oil extraction and exploration projects) and overpopulation. Evidence is presented that the forest species (N. melanoleuca) was much more common than the savanna species (N. nigricollis) in the recent past when rates of deforestation were much smaller than today. Nowadays, the savanna species is very common and widespread, not only in suburban and altered habitats, but also in mature secondary forests. Moreover, contrary to the forest species, it is peculiar in that it greatly reduces its feeding rates during the peak of the dry season. These reduced feeding rates were observed in both adults and juveniles, in both males and females, and in three different habitat types (forest, suburbs, and forest-plantation mosaic). No links with reproductive biology can be advocated to explain such a pattern. It is hypothesized that this ecological pattern reflects suboptimal adaptation of the savanna species to rainforest biota, and is a "ghost" of this species' recent invasion of the rainforest region.
... Earlier data of presence (collected in 1996-2009) were not considered, given that the general habitat features may change very quickly in the Niger Delta region, thus producing local extirpation of several species (also because of intense hunting; see Eniang et al. 2008;. In Niger Delta reptiles, local extirpations or changes in abundance of forest specialists may be followed by replacement of the emptied niches by other vicariants, more generalists or potential competitor species (Luiselli 2001(Luiselli , 2002. The same mechanism might also occur in mammals (Blench 2007), but no such evidence has been reported to date. ...
... However, concerning the Niger Delta region, we are aware of some intriguing patterns that may allow at least some tentative hypotheses to be tested in future studies. Field studies on cobras (Reptilia: Elapidae: Naja Laurenti, 1768) have clearly demonstrated that, following the expansion of oil pipelines throughout the forest blocks and rapid human development programs, one Guinea savannah species (Naja nigricollis Reinhardt, 1843) has greatly expanded its range within the Niger Delta region by challenging the niche of the forest cobra (Naja melanoleuca (Hallowell, 1857)) (Luiselli 2001(Luiselli , 2002, despite still showing some life history characteristics typical of savannah snakes Luiselli 2001;Luiselli et al. 2002). Thus, N. nigricollis is currently the dominant species all over the region , including also inside forest patches , whereas it was very rare and just occasionally found before the oil industry blooming in the 1960s (Luiselli 2002). ...
... However, concerning the Niger Delta region, we are aware of some intriguing patterns that may allow at least some tentative hypotheses to be tested in future studies. Field studies on cobras (Reptilia: Elapidae: Naja Laurenti, 1768) have clearly demonstrated that, following the expansion of oil pipelines throughout the forest blocks and rapid human development programs, one Guinea savannah species (Naja nigricollis Reinhardt, 1843) has greatly expanded its range within the Niger Delta region by challenging the niche of the forest cobra (Naja melanoleuca (Hallowell, 1857)) (Luiselli 2001(Luiselli , 2002, despite still showing some life history characteristics typical of savannah snakes Luiselli 2001;Luiselli et al. 2002). Thus, N. nigricollis is currently the dominant species all over the region , including also inside forest patches , whereas it was very rare and just occasionally found before the oil industry blooming in the 1960s (Luiselli 2002). ...
Community composition and an index of relative abundance were analyzed for
mammals (excluding most rodents, shrews and bats) of five forest reserves in the Niger
Delta (Southern Nigeria). Twenty-nine species were recorded, 86.2% of them being
found in all protected areas. Although most of the species were already known from the
study area, there were unexpected patterns concerning the duikers. Indeed, the presence
of only one species (Philantomba walteri) (CH Smith, 1827) was confirmed, whereas at
least five additional duiker species were reported for the study area by earlier authorities.
Another duiker species (Cephalophus niger Gray, 1846) was recorded once during the
present surveys and is not known whether it represents a stabilized presence in the Niger
Delta. The empirical Abundance Index suggested that only three species were very rare
(Trichechus senegalensis (Link, 1795), C. niger, and Pan troglodytes (Blumenbach,
1775)). Diversity-dominance diagrams showed that the evenness profiles were similar
across study areas. Linear distance (Km) between the barycenters of forest reserves was
significantly positively correlated with relative community composition dissimilarity.
Overall, a biotic homogenization process for the mammal communities of the five forest
reserves was observed, likely as an outcome of the high deforestation of the last 50 years.
... G.C. Akani 1 , F.M. Angelici 2 , L. Luiselli 2 Over the last few years, a series of field studies have been published by scientific journals worldwide on the ecology and natural history of highly venomous African elapids (e.g., for studies on Dendroaspis see Angilletta, 1994;Branch et al., 1995;Phelps, 2002; for studies on Naja see Luiselli, 2001Luiselli, , 2002, thus indicating a renewed interest in the behavioural ecology of these impressive animals after many years in which most studies related to their venoms and clinical outcomes of their bites or taxonomy. However, the tree cobras (genus Pseudohaje), despite being highly venomous and impressive in size, have just been subjected to a few brief notes during recent years (e.g., see Pauwels and Ohler, 1999;. ...
... Although we were unable to get data as detailed and informative as those we collected from other species including e.g. cobras and green mambas Luiselli, 2001Luiselli, , 2002, nonetheless we feel that our data are still important to improve the knowledge of the tree cobras biology, given that nearly to nothing is known of the field ecology of these elapids. Therefore, in this paper we collate all our field data on the tree cobras in southern Nigeria, although we realize that the data presented in this paper may have some limitations due to a relatively small sample size. ...
... The same was also observed in Gabon (Pauwels and Toham, 2002). Certainly, the presence of tree cobras in Nigerian suburbs is much more occasional than that of other elapids, including the spitting cobra Naja nigricollis (Butler and Reid, 1986;Luiselli, 2001Luiselli, , 2002 and the Jameson's green mamba Dendroaspis jamesoni . ...
Over the last few years, a series of field stud-ies have been published by scientific journals worldwide on the ecology and natural history of highly venomous African elapids (e.g., for stud-ies on Dendroaspis see Angilletta, 1994; Branch et al., 1995; Luiselli et al., 2000; Phelps, 2002; for studies on Naja see Luiselli and Angelici, 2000; Luiselli, 2001, 2002; Luiselli et al., 2002), thus indicating a renewed interest in the behav-ioural ecology of these impressive animals af-ter many years in which most studies related to their venoms and clinical outcomes of their bites or taxonomy. However, the tree cobras (genus Pseudohaje), despite being highly venomous and impressive in size, have just been subjected to a few brief notes during recent years (e.g., see Pauwels and Ohler, 1999; Pauwels et al., 1999). The relative scarcity of tree cobra stud-ies is likely due to the highly elusive habits of these arboreal elapids compared to mambas and cobras, as well as on their apparent rarity in por-tions of their ranges in west and central Africa (e.g., see the field notes reported in Cansdale, 1961, and in later literature). During the long-term field works we have been devoting to study the ecology of forest snakes in Nigeria (1994 up to now, with at least 100 days in the field on each year), we have encountered Goldie's tree cobras (Pseudohaje goldii) on several occasions, and obtained data on their field biology. Although we were unable to get data as detailed and informative as those we collected from other species including e.g. cobras and green mambas (Luiselli et al., 2000, 2002; Luiselli, 2001, 2002), nonetheless we feel that our data are still important to improve the knowledge of the tree cobras biology, given that nearly to nothing is known of the field ecology of these elapids. Therefore, in this paper we collate all our field data on the tree cobras in southern Nigeria, although we realize that the data presented in this paper may have some limitations due to a relatively small sample size.
... The local expansion of C. durissus was noticed in hospital admissions with higher numbers of bites. Likewise, the spitting cobra (Naja nigricollis) is gradually replacing the black forest cobra (Naja melanoleuca) following deforestation in Nigeria (Luiselli, 2001). ...
... The above cases illustrate some of the environmental change effects on snakes that alter snakebite epidemiology: 1) climate change makes snake populations physiologically unable to cope with higher temperatures and decline (C. willardi; Davis et al., 2015); 2) climate change interacts with land use change to decrease connectivity resulting in genetic bottlenecks and facilitate detrimental biological interactions (e. g., water-borne infectious diseases in C. horridus; Clark et al., 2011); 3) land use change can create hospitable conditions for species that might not be able to adapt in the absence of those anthropogenic habitat perturbations (Naja nigricollis in Nigeria (Bastos et al., 2005;Luiselli, 2001); and further create habitat corridors that allow dispersal of distant snake species (C. durissus invasion in Brazil; Sazima, 1992). ...
Snakebite envenoming is a set of intoxication diseases that disproportionately affect people of poor socioeconomic backgrounds in tropical countries. As it is highly dependent on the environment its burden is expected to shift spatially with global anthropogenic environmental (climate, land use) and demographic change. The mechanisms underlying the changes to snakebite epidemiology are related to factors of snakes and humans. The distribution and abundance of snakes are expected to change with global warming via their thermal tolerance, while rainfall may affect the timing of key activities like feeding and reproduction. Human population growth is the primary cause of land-use change, which may impact snakes at smaller spatial scales than climate via habitat and biodiversity loss (e.g. prey availability). Human populations, on the other hand, could experience novel patterns and morbidity of snakebite envenoming, both as a result of snake responses to environmental change and due to the development of agricultural adaptations to climate change, socioeconomic and cultural changes, development and availability of better antivenoms, personal protective equipment, and mechanization of agriculture that mediate risk of encounters with snakes and their outcomes. The likely global effects of environmental and demographic change are thus context-dependent and could encompass both increasing and or snakebite burden (incidence, number of cases or morbidity), exposing new populations to snakes in temperate areas due to “tropicalization”, or by land use change-induced snake biodiversity loss, respectively. Tackling global change requires drastic measures to ensure large-scale ecosystem functionality. However, as ecosystems represent the main source of venomous snakes their conservation should be accompanied by comprehensive public health campaigns. The challenges associated with the joint efforts of biodiversity conservation and public health professionals should be considered in the global sustainability agenda in a wider context that applies to neglected tropical and zoonotic and emerging diseases.
... In addition, inspections of hunters' traps (with permission) were performed. In each plot category, a total of seven field days were conducted, during the wet season in order to enhance the chance of encounters with reptile individuals (Akani et al., 2013;Luiselli, 2001Luiselli, , 2002. In each field day, the number of surveyors was constant (n = 4), and the field effort was standardized as much as possible. ...
... These patterns were mainly due to the reduction in the snake fauna richness (for instance, the forest-linked species such as Bitis spp. (Luiselli, 2006) and Naja melanoleuca (Luiselli, 2001(Luiselli, , 2002) disappeared from burnt plots), but also with extirpation of some lizard species (e.g., chameleons) and tortoises (Kinixys spp.) that are also typical forest dwellers (Chirio & LeBreton, 2007). Considering the values of the community metrics during the postfire succession, the gradual increase in the number of species, number of individuals and diversity from plot A to C may show that Afrotropical reptile communities can recover from small-scale fires effects on their habitat. ...
... In the present study, we probably detected relatively more individuals of the largest, diurnal or most conspicuous species, and failed to detect many individuals of the smallest, arboreal, burrowing or elusive species, especially during the dry season (when reptile activity is depressed; e.g. Luiselli, 2001Luiselli, , 2002. For instance, whereas all the four singletons recorded in the wet season were never captured by dry season, the two singletons recorded during the dry season were instead captured multiple times in wet season, as was also the case of all doubletons. ...
... Other evidences of this alteration process were given, during the present surveys, by the following: (i) the relative prevalence of the spitting cobra (Naja nigricollis) over the forest cobra (Naja melanoleuca) and (ii) the apparent extirpation of the forest tortoise Kinixys homeana. As regards point (i), it has been demonstrated that the savannah cobra species (Naja nigricollis) has recently spread over the whole forested region of Nigeria challenging the niche of the forest species (Naja melanoleuca) (Luiselli, 2001(Luiselli, , 2002. Therefore, forest sites with preponderance of the former species over the latter do indicate that the pristine forest ecosystem has been substantially altered. ...
The study of community composition shifts due to increased habitat modifications and deforestation is a primary issue in contemporary tropical community ecology theory. As the forest habitat conversion process has been very short in Africa relative to the evolutionary temporal scale, it is likely that animal communities are not at an equilibrium. The Upper Orashi Forest Reserve (Niger Delta region of Southern Nigeria) is a valuable case study as it is one of the few remnant deltaic swamp forest patches inside a highly developed and deforested region. In this paper, we investigated some aspects of the community ecology of reptiles of this forest area based on standardized field surveys across 26 study plots. Overall, we recorded 34 species, with the detected number of both species (34 versus 27) and individuals (562 versus 381) being higher during the wet season. Diversity/dominance diagrams showed similar trends in both seasons, but diversity measures showed that evenness was remarkably higher by wet season. Analysis of similarities (ANOSIM) confirmed that the species-richness estimate generated by Chao's index was significantly higher for the wet season. However, the profiles of the diversity curves were comparable in the two seasons. The proportion of forest-specialist species decreased compared to that observed at the same study area 15+ years ago, with a gradual process of biotic homogenization being apparent.
... Studies on African tropical snakes have shown a strong relationship between rainfall and activity, with peaks occurring at the onset of the wet seasons and continuing to increase throughout wet months (e.g., Akani et al., 2002). This general pattern has been confirmed in both mainly savannah species, for instance Naja nigricollis (Luiselli, 2001) and Crotaphopeltis hotamboeia , and mainly forest-dwelling species such as Naja melanoleuca (Luiselli, 2001), Bitis gabonica and Bitis nasicornis (Luiselli, 2006;Akani et al., 2013). Moreover, the seasonal incidence of humans getting bitten by snakes (a proxy of snake activity intensity) showed that in agricultural landscapes in Bangladesh and African savannah, snake bites occur more frequently in the wet season (pattern observed in Bangladesh, Mali, Burkina Faso, Nigeria, Ivory Coast, Cameroon, Ghana and Benin; see Chippaux, 2006;Rahman et al., 2010). ...
... Studies on African tropical snakes have shown a strong relationship between rainfall and activity, with peaks occurring at the onset of the wet seasons and continuing to increase throughout wet months (e.g., Akani et al., 2002). This general pattern has been confirmed in both mainly savannah species, for instance Naja nigricollis (Luiselli, 2001) and Crotaphopeltis hotamboeia , and mainly forest-dwelling species such as Naja melanoleuca (Luiselli, 2001), Bitis gabonica and Bitis nasicornis (Luiselli, 2006;Akani et al., 2013). Moreover, the seasonal incidence of humans getting bitten by snakes (a proxy of snake activity intensity) showed that in agricultural landscapes in Bangladesh and African savannah, snake bites occur more frequently in the wet season (pattern observed in Bangladesh, Mali, Burkina Faso, Nigeria, Ivory Coast, Cameroon, Ghana and Benin; see Chippaux, 2006;Rahman et al., 2010). ...
During the last decades annual activity patterns of temperate snake species have received considerably more attention than those of tropical snakes. In this study, we document the monthly activity patterns of a species-rich assemblage of snakes from a tropical forest-plantation mosaic in Bangladesh based on specimens collected by a systematic road kill survey for 14 months, and relate them to the climatic characteristics of the study area with special reference to monsoon regimes. We recorded 503 Dead-On-Road (DOR) snakes, belonging to 30 different species, with a mean DOR/km rate of 0.247. Overall, snake activity was uneven throughout the year, being particularly intense during July, August and October, and significantly reduced in December, January and February. Five out of nine species with considerably robust sample sizes showed consistently uneven monthly activity patterns. Monsoon seasonality deeply influenced the phenology of several Asian-tropical snakes, with some species being active especially at the middle or end of the monsoon period while others are active throughout the monsoon period.
... In previous studies we have documented that some savannah species of snakes (notably the spitting cobra, Naja nigricollis) are now invading formerly forested areas and exploiting the niches of their relatives who are more closely adapted to the rainforest habitats (i.e. the forest cobra, Naja melanoleuca). The spitting cobra is suboptimally adapted to the life in mature rainforest (Luiselli, 2001), yet each year it is more common in every habitat type. Conversely, the forest cobra is becoming increasingly rare and is clearly succumbing to this strong interspecific competition with the savannah invader (Luiselli, 2002). ...
... This is because the pattern of species succession in both lowland and montane anuran assemblages in Southern Nigeria mirrors that found in cobras from the same study region. That is to say, there is again an ongoing shift in species dominance from the forest specialists (dominant until the 1980's) to the generalists, which are now dominant almost everywhere (Luiselli, 2001(Luiselli, , 2002. And, exactly as in the case of the cobras, a particularly interesting question would be to explore the costs and benefits to generalist species of invading recently deforested or secondarily forested areas. ...
Tropical forests worldwide undergo severe anthropogenic habitat alteration. We report here on various long-term studies in Nigerian rainforests and show that there appears to be a trend of change in herpetofaunal communities that follows this habitat change. Specifically, as rainforest environments become degraded there is a shift from a predominance of forest specialists to a predominance of generalists that are able to utilize a wide range of habitats (although overall species diversity may remain stable or even locally increase). The same shift is seen regardless of the type of habitat (e.g. seasonally flooded lowland forest or montane forest) or the taxa (e.g. anura or serpentes). An amphibian survey was conducted in 2002 in the Obudu plateau, Nigeria, which is an area of major conservation importance, containing many endemic and threatened species. The environment has been severely degraded and suffered heavy deforestation in recent years, and expanding leisure tourism threatens to have an even greater environmental impact. We compare the results from our current survey to other studies by previous authors conducted in the 1960’s and 1980’s to provide an insight into changes in community species composition after many years of anthropogenic disturbance. We discuss the reasons for the success and failure of particular specialist and generalist species.
... Area B, the Rumuosi marshes, Rivers State, was a secondary freshwater swamp forest situated about 20 km north of the metropolitan centre of Port Harcourt, the capital of Rivers State. This area was also used by the writer and associates for long-term snake studies (e.g., Luiselli 2001). Area C, farmbush off Atimbo Road, was a remnant patch of secondary freshwater swamp forest completely surrounded by subsistence farms and suburbia situated inside the metropolitan territory of Calabar, the capital of Cross River State. ...
... Area C, farmbush off Atimbo Road, was a remnant patch of secondary freshwater swamp forest completely surrounded by subsistence farms and suburbia situated inside the metropolitan territory of Calabar, the capital of Cross River State. This area was also used for long-term surveys of snake ecology , and is therefore well explored (e.g., Luiselli 2001). Area D, the AGIP oilfield at Oguta on the eastern side of the Niger Delta, Anambra State, was a patchy mosaic of freshwater swamp forest, plantations (oil palms, coconuts, cassava, yams), and oilfields. ...
Two species of rain-forest snakes, the colubrids Natriciteres fuliginoides and Natriciteres variegata, are potential competitors, because they attain, on average, the same body size (2030 cm long), have similar habits and ecological requirements (they are both diurnal and nocturnal, often semi-aquatic), and have similar dietary spectra ( including both small vertebrates and invertebrates). I studied prey type and predator size prey size relationships of these snakes in four swamp-forest areas of southeastern Nigeria (West Africa): only N. fuliginoides was found in two of these areas, whereas both species were common in the other two areas. The feeding ecology of N. fuliginoides shifted greatly in the presence of its potential competitor, N. variegata, in terms of prey-type preferences and predatory behaviour as well as in terms of predator size prey size relationships. In particular, the effects of the potential competitor on the feeding ecology of N. fuliginoides were (i) a shift toward eating many invertebrates from a diet based on many small vertebrates, (ii) a shift toward eating many terrestrial organisms from a diet based on many aquatic organisms, and (iii) a shift in mean prey size for females toward relatively larger prey from a diet based on smaller prey. The resulting effect was a clear partitioning of food resources between the two predator species in both the areas where they are sympatric, whereas N. fuliginoides had a wider dietary spectrum (covering that of the two species together) in the areas where its competitor is not found. The role of intraspecific competition seems less strong, as no apparent resource partitioning in prey type or prey size was observed between males and females of either species or in any study area. However, mean prey size was significantly greater for females than for males of both species and in all study areas, but depended on the significant reverse sexual size dimorphism observed in both species.
... Using data collected during a long-term study on the ecology of snake communities in southern Nigeria, West Africa (e.g. see Luiselli, Akani & Capizzi, 1998;Akani et al., 1999;Luiselli, 2001Luiselli, , 2003Luiselli, Angelici & Akani, 2002;Luiselli & Akani, 2002a,b), we tested the following key questions: ...
... It is probable that the weak statistical significance of these relationships may depend on reduced statistical power owing to the relatively low abundance of most of the species of snakes in African forest habitats (see Scott, 1982;Andreone & Luiselli, 2000). The positive trends of these relationships may depend especially on the effects of a large-sized invader species (the spitting cobra, Naja nigricollis), which is now widespread and abundant in these habitats in southern Nigeria, whereas it was much less common in these areas 30-40 years ago (Luiselli, 2001(Luiselli, , 2002. This species has successfully invaded the forest and mangrove areas, taking advantage of the massive deforestation consequent to the expansion of the oil industry and human overpopulation that has occurred in southern Nigeria in the last decades (De Montclos, 1994), and which has probably changed the ecological equilibrium (Luiselli & Angelici, 2000;Luiselli, 2002;Luiselli, Angelici & Akani, 2002). ...
The relationships between population abundance, body size, food habits and ecological guild (aquatic, terrestrial, arboreal, and fossorial) of snake communities are studied in three different habitats (swamp-rainforest, mangrove forest and derived savanna) of southern Nigeria, West Africa. There were slightly positive relationships between body size and population abundance of snakes in the three study habitats of tropical Nigeria, but statistical significance was reached only in the swamp-rainforest habitat. The population abundance of the various species was not related to either their food habits or their ecological guild in any of the three study areas. The possible reasons explaining these patterns are discussed. In general, there is little congruence between our data and the popular ‘energetic equivalence rule’ hypothesis.
... The venom enzyme may attack DNA, RNA or any nucleotide chain. The differences in the type of sugar or bases have no effect on the reaction rate (Luiselli, 2001). ...
... Moreover, the invasion of a competitor species can push the more specialized one to extinction [7]. Endemic species, which are normally narrowly distributed, may be affected negatively by the invasion of more widespread and generalist species challenging their niche [7,8]. ...
Organisms that are similar in size, morphological characteristics, and adaptations, including vertebrates, often coexist by partitioning the available resources (food, space, and time). So, studies of the dynamics of these cases of coexistence are scientifically interesting. Here, we study a coexistence case of two species of freshwater turtles inhabiting the forest waterbodies of West Africa, focusing on the dietary habits of the two species. We found that both turtle species are omnivorous generalists, eating both vegetal and animal matter abundantly. However, there were clear interspecific differences, with the larger of the two species (P. cupulatta) eating more vertebrates (mainly fish but occasionally other vertebrates), whereas P. castaneus consumed more invertebrates. These patterns appeared consistently within the species and across sites, highlighting that the same patterns were likely in other conspecific populations from the Upper Guinean forest streams (Côte d'Ivoire and Liberia). Our study also showed that interspecific competition for food does not occur between these two species; instead, previous studies uncovered that a clear partitioning of the habitat niche occurs. We conclude that the food resource is likely unlimited in the study areas, as it is not the case in more arid environments (since food shortages may occur during the dry season). We anticipate that, within the Pelomedusidae communities throughout Africa, intense competition for food probably occurs in the Sahel and Sudanian vegetation zones, particularly during the dry months, but is unlikely within the Guinea and wet savannah region and even less likely in the Guineo-Congolian rainforest region.
... Naja nigricollis nigricollis (NNN), belonging to Elapidae family, is one of most dangerous snakes responsible for serious medical emergencies in Nigeria [2,3]. Naja n. nigricollis snake dominates the rainforest of South-eastern Nigeria, probably because of its unique adaptive features and defensive behavior [4,5]. ...
Objectives
To investigate the effect of kolaviron against haematological abnormalities and hepato-renal damage in Naja n. nigricollis (NNN) venom-treated rats.
Methods
Twenty-four male rats were grouped into four (n=6). A single intravenous dose of NNN venom (≈½LD50) was given to group B–D (excluding A). All the groups were immediately treated intraperitoneally as follows: A (Normal control) and B (Envenom) received 0.40 mL/kg of 0.1% Tween 80, while C and D (test groups), received 200 and 400 mg/kg of kolaviron respectively. After 6 h, they were anaesthetized, and sacrificed.
Results
NNN-venom LD50 was estimated at 1.14 mg/kg. Injected half LD50, after 6 h, caused significant (p<0.05) decreases in RBC, HGB and PCV, with increases in WBC and NEUT. Significantly (p<0.05) increased AST, ALT, GGT, TB, CRE, URE, UA and K with concomitant decreases in Na and HCO3. Oxidant/antioxidant markers (MDA, CAT and SOD) were significantly (p<0.05) increased in liver and kidney homogenates. Histological analysis confirmed liver and kidney injuries. All these alterations were alleviated dose-dependently, when cotreated with kolaviron at 200 and 400 mg/kg.
Conclusions
Our study suggests that kolaviron could alleviates haematological abnormalities and hepato-renal damage in NNN venom-treated rats by depleting ROS and/or boasting the antioxidant system.
... To begin with, it is well known that interspecific competition tend to be intensified in tropical than in non-tropical communities of species (Pianka, 1966;Luiselli, 2008), thus potentially leading to extirpations of threatened species from potentially good (suitable) sites because of the sympatry with strong competitors (e.g., Petrozzi et al., 2021). For example, in West Africa the opening of new roads within once mature forested areas, has led to the niche expansion with consequent invasion of the secondary forest habitat by a savannah snake (Naja nigricollis) (Luiselli, 2001(Luiselli, , 2002. This natural expansion has increased the interspecific competition with, and has challenged the niche of, the previously widespread rainforest species (Naja melanoleuca), thus causing its generalized rarefaction and local extirpation within a few decades (Luiselli, 2002). ...
Conservation strategies are mainly decided, also for tropical species and habitats, on the basis of studies and examples made in the temperate regions, especially in North America and Europe. Conservation strategies for tropical species are often thought to fail due to a plethora of « human dimension » reasons. These reasons are external to the natural history and ecology of the target species, being due shortage of funds, education and awareness limits, and institutional corruption in several countries, particularly in the developing countries of Africa and Asia. Although these reasons are certainly important in determining the outcome of the conservation projects, herein we stress that there is a scientific ecological reason behind such failures in tropical ecosystems. Indeed, the ecological « entropy » of the species-rich and niche-packed tropical ecosystems is so much higher than that of North America and Europe that adopting a decision-making process based on relatively simplified (temperate) ecosystems, where a given species typically interacts with a few others, makes the eventual solution very simplistic or even « naive », thus enhancing its chances of failure. We urge that, for the future, conservation policies for tropical regions should be based on experiences designed from more realistic « highly-entropic » species-rich systems, also in the case of those species apparently sharing similar ecological roles as in the temperate regions.
... Naja nigricollis nigricollis (Elapidae family) is one among the major three poisonous snakes (Naja n. nigricollis, Echis ocellatus and Bitis arietans) responsible for high morbidity and mortality in Nigeria [4,5]. The burden of Naja n. nigricollis fatalities is more prominent in South eastern Nigeria than any other snake largely due to its wide distribution, adaptation, venom potency and their frequent encounter with humans [2,6]. ...
Objectives
Snakebite envenoming is an important public health problem that threatens the lives of healthy individuals especially in many tropical countries like Nigeria. Antivenins, the only efficient approach for snakebite envenoming, are limited in their efficacy in the neutralization of local tissue damage. Snake venom phospholipase A 2 (PLA 2 ), protease, hyaluronidase and l -amino acid oxidase (LAAO) are the major hydrolytic enzymes involve in local tissue damage. Therefore, this study evaluates the inhibitory effect of kolaviron (KV) against Naja n. nigricollis (NNN) snake venom hydrolytic enzymes involved in local tissue damage.
Methods
Kolaviron was evaluated for its ability to inhibit the hydrolytic enzyme activities of NNN venom phospholipase A 2 (PLA 2 ), protease, hyaluronidase and l -amino acid oxidase (LAAO). Present study also deals with the neutralization of NNN venom enzyme(s) induced complications such as myotoxic, edemic, hemolytic and procoagulant effects.
Results
Kolaviron inhibited the PLA 2 , protease, hyaluronidase and LAAO enzyme activities of NNN venom in a dose-dependent manner. Furthermore, myotoxic, edemic, hemolytic and procoagulant effects induced by NNN venom enzyme were neutralized significantly (p<0.05) when different doses of KV were pre-incubated with venom before assays.
Conclusions
These findings clearly present kolaviron as a potent inhibitor against NNN venom hydrolytic enzymes involved in local tissue damage and may act by either forming an inhibitor-enzyme complex that restricts the substrate availability to the enzyme or direct binding to the enzyme active site that affects the enzyme activity thereby mitigating venom-induced toxicity.
... We found out that the snakes encountered in this study were reported from almost all parts of Nigeria. This indicates that the geographical distribution of snakes was all over Nigeria (Luiselli 2001;Molesworth et al. 2003;Akani et al. 2013). Therefore, comprehensive conservational interventions need to be carried out all over the country to protect snakes in their natural habitats. ...
The internet is a useful tool for obtaining
data needed to study factors that hinder snake conservation especially in resource-limited settings. There is a paucity of peer-reviewed
research on the use of online communities in the study of factors contributing to undesirable human-snake conflicts in Nigeria. A 12-
month dataset (August 2016-July 2017) on human-snake encounters shared on Nairaland®- a popular online community forum in
Nigeria - was retrieved and analyzed. Morphological characteristics observed in the snake photographs posted on the platform were used
for species identification. A total of 203 human-snake encounters were recorded from 32/37 States of Nigeria. Men (n=133) reported
more human-snake encounters than women (n =11) while “reporters of unspecified gender (n =59) accounted for the rest. Most postings
were from the southern part of Nigeria with the highest number of postings from Lagos State (n =34). Of the 24 snake species reported
in the study, the African Rock Python was the most encountered. The months of May to July recorded the highest number of snake
species reported by the respondents. ‘Fear’ and ‘food’ were the major perceptions elicited by people during snake encounters. The
outcome of human-snake conflicts resulted in snake deaths (n =182) irrespective of snake venomosity. Only 1.0% (n=2) of the snakes
were protected from harm. This study revealed that data from online community forums are useful for retrospective studies of the
perceptions and outcomes of human-snake encounters; the output of which policymakers and conservationists may find useful.
... Ongoing homogenisation process has already been shown for snakes and chelonians (Luiselli, 2001(Luiselli, , 2002. Similarly, we demonstrate in our study that there is evidence of impoverishment of the small carnivore community in the Rivers State agro-forestry systems from comparisons between our study area and more heavily forested areas in the central Niger Delta and in Benin (Djagoun & Gaubert, 2009; Table S3). ...
... The alternance of dry and wet periods in tropical regions (Griffiths, 1972) is well known to influence activity patterns and the ecology of several vertebrates (e.g., Marques, Eterovic, & Whaldener, 2001;Moreira & Lima, 1991). For instance, the above-ground activity of ectotherm reptiles is much depressed during the peaks of the dry season even in the rainforest regions (e.g., Akani et al., 2013;Rahman, Faiz, Selim, Rahman, & Basher, 2010), and the foraging activity is also reduced, in at least some species (e.g., Luiselli, 2001Luiselli, , 2002. Because of these seasonal variations in general activity and foraging, it can be hypothesized that even the diet composition of the tropical reptiles can change considerably from month to month due to the rainfall variations also influencing the activity and productivity of prey types. ...
... Several publications shows foraging period is regulated by humidity and most of the reptiles will adjust daily and seasonal activity to minimize water loss and they will seek humid or enclosed retreats such as crevices or borrows (Zug, 2001). Luiselli (2001Luiselli ( , 2002) demonstrated that tropical reptiles shows peak activity in rainy season or when the humidity is high. In the present study, particularly this sanctuary, we observed the activity of S. ponticeriana throughout the year and this is possible due to high humidity due to Bay of Bengal. ...
Microhabitat use and activity patterns of Sitana ponticeriana were observed in their natural habitat over two consecutive
years at Balukhand-KonarkWildlife Sanctuary, Orissa, India. Lizards perched above the ground, mainly
on herbaceous vegetation, sandy areas, cracks and crevices and small shrubs�bushes of the canopy. During the
morning and late afternoon, the lizards favored herbaceous vegetation, and during early afternoon used a variety
of microhabitats including shrubs�bushes, cracks and crevices, and root of the trees. Lizards were sighted in
large numbers during morning and late afternoon. Sightings declined in the early afternoon with rise in ambient
temperature. Daily activity patterns of all lizard size classes typically involved basking in the morning hours followed
by foraging, moving and other activities. S. ponticeriana was found to be active foragers with frequent
wandering movement. Foraging behavior did not vary significantly between males and females, whereas juveniles
foraged near their retreats.
... Several publications shows foraging period is regulated by humidity and most of the reptiles will adjust daily and seasonal activity to minimize water loss and they will seek humid or enclosed retreats such as crevices or borrows (Zug, 2001). Luiselli (2001Luiselli ( , 2002) demonstrated that tropical reptiles shows peak activity in rainy season or when the humidity is high. In the present study, particularly this sanctuary, we observed the activity of S. ponticeriana throughout the year and this is possible due to high humidity due to Bay of Bengal. ...
... The alternance of dry and wet periods in tropical regions (Griffiths, 1972) is well known to influence activity patterns and the ecology of several vertebrates (e.g., Marques, Eterovic, & Whaldener, 2001;Moreira & Lima, 1991). For instance, the above-ground activity of ectotherm reptiles is much depressed during the peaks of the dry season even in the rainforest regions (e.g., Akani et al., 2013;Rahman, Faiz, Selim, Rahman, & Basher, 2010), and the foraging activity is also reduced, in at least some species (e.g., Luiselli, 2001Luiselli, , 2002. Because of these seasonal variations in general activity and foraging, it can be hypothesized that even the diet composition of the tropical reptiles can change considerably from month to month due to the rainfall variations also influencing the activity and productivity of prey types. ...
... A similar penetration process from savannah to forests has been demonstrated for at least one other reptile species, i.e., the savannah cobra, Naja nigricollis, that has recently spread over the whole forested region of Nigeria, challenging the niche of the forest species, Naja melanoleuca (Luiselli 2001(Luiselli , 2002. A same pattern of forest colonization and niche expansion in Niger Delta is also likely occurring in two other sympatric chelonian species, i.e. ...
The West African Mud Turtle, Pelusios castaneus (Family Pelomedusidae), is an aquatic turtle of moderate size (carapace length to ca. 250–285 mm) indigenous primarily to savannah environments, but widely tolerant in terms of habitat requirements, and also able to penetrate into some forest and mangrove zones. It has rather variable coloration, but is recognizable by the pattern of fine, sinuous vermiculations on the head and the light plastron, unmarked except for angular figures around its periphery that may be either distinct or contiguous. In addition, the narrow, elliptical intergular scute and the very short pectorals are characteristic. Its field ecology has been studied extensively and quantitatively only in southern Nigeria, with such disparate features as home range, habitat selection, and food habits being analyzed. The species is omnivorous (but primarily carnivorous), with dietary composition shifting by season and by site, and also in relation to site pollution. The adult sex ratio is even. The species may potentially be a competitor of P. niger in the forest water bodies of southern Nigeria, and especially in the oil-polluted areas, due to an increased niche similarity between these species along the spatial and food niche axes. Pelusios castaneus is locally abundant, and its populations appear to be stable.
... producing range depressions or new colonizations, shifts in behaviour, changes in some eco-physiological attributes, etc (e.g. see Pimm 1991, Brandon 1995, Williamson 1996, Luiselli 2001, 2002. It is also possible that specific cultural traditions may produce alterations to the behaviour and life-history traits of specific target animals as a direct response to that cultural tradition, or as an indirect response to the changes in proxi-mate external conditions originated by that cultural tradition (Luiselli 2003). ...
A mountainous site in central Italy (Cocullo, Abruzzi region) offers an exceptional opportunity to test whether the effects of several centuries of "manipulations" on snakes by humans (for traditional religion-linked cultural events) may have altered the reproductive phenology of free-living snakes, which is strongly seasonal in these regions. The Saint Domenico's procession ritual takes place at Cocullo village on the first Thursday of May of each year, and has done for well over 300 years. For this ritual, local snake-hunters search for snakes throughout the woodlands around the village during April, and capture many snake specimens just before the onset of their spring mating season. The hunters set them free by mid May, after the end of the procession rituals. The species used are mainly Elaphe quatuorlineata, E. longissima, and Coluber viridiflavus. Due to the large number of specimens captured, it is likely that the pressure of the snake-hunters is very high on the local population of snakes, and that most of the adults are indeed captured each year for the procession. Reproductive seasonality of the three species targeted for the procession and of a non-target sympatric species (Vipera aspis) was studied in both the woodlands around Cocullo and in the woodland around another village, with similar eco-climatic characteristics, where no such snake hunting occurs. There was a remarkable delay in the reproductive seasonality of target species, especially of the two Elaphe (E. quatuorlineata and E. longissima), whereas no such effect was observed in the species which is not used for the procession (V. aspis). These effects (delaying of oviposition period of 20-40 days on average) were so evident, that they probably may have important consequences for other aspects of the reproductive biology of these animals (e.g., length of the reproductive cycle, reproductive frequency, etc). On the other hand, clutch size was not influenced by hunting in any species.
... Swimming speed in snakes is related to species and sex but not to body weight (Shine et al., 2003) -a fact that is exploited by the large Boidae which are far more at ease while moving in water than on land. The threatened Python sebae, the largest snake in Africa continent, forages along large water courses hunting for riparian vertebrates including water birds and cattle (Luiselli, 2001). In Nigeria, they use rivers as dispersal corridors to penetrate towns where they feed on dogs, poultry and other domestic animals . ...
Aquatic, semi. -aquatic and terrestrial vertebrates play a very important role in energy flow, nutrient cycling, and riparian landscape engineering. The current geographic distribution of aquatic, semi-aquatic, and riparian species is a reflection of the abundance and variability of water supply in different regions. They are vulnerable to habitat degradation or alteration associated with flow regulation, irrigation schemes, and the conversion of floodplains to agriculture. Freshwater habitats provide food and shelter to a large number of vertebrates besides fish, but only a few are wholly adapted to inland waters. Semi. -aquatic reptiles are represented by some of the most ancient living vertebrate species, which include the 23 species of crocodilians, two thirds of the 250 species of modern testudinids, and a small number of freshwater snakes. Semi. -aquatic mammals such as otters and hippopotamuses display remarkable anatomical and physiological adaptations. And riparian species exhibit characteristic behavioral traits. Rivers serve as bio. -corridors for aquatic and semi. -aquatic vertebrates. The riparian mammals include some rodents and shrews, monkeys, buffaloes, antelopes, etc.
... (3) Are monthly activity patterns uneven in subterranean tropical snakes and is there any temporal niche separation among cooccurring species? Uneven monthly activity patterns, with peaks in wet season, are expectable because this type of pattern has already been demonstrated for Nigerian forest snakes (e.g., Luiselli, 2001;Akani et al., 2013), as well as for other tropical snake species (e.g., Rahman et al., 2013). Nonetheless, it is predictable that the subterranean 'environment' is seasonally more stable than above-ground 'environments', and hence it may be plausible that subterranean snakes may be least prone than aboveground active species to seasonal variations in activity patterns. ...
Niche partititioning patterns have not been studied so far in burrowing tropical snakes of the families Typhlopidae and Leptotyphlopidae. In this study, we analyze temporal (= monthly activity) and spatial (= habitat use) niche dimensions in three species of burrowing snakes from the Niger Delta, Nigeria. Null model analyses, using two randomization algorithms and 30 000 Monte Carlo permutations, showed that there was random resource partitioning patterns as for the spatial niche dimension. One species (Rhinotyphlops punctatus) clearly dominated in the sample, and appeared to be more habitat generalist than the others. All three species showed an uneven monthly activity, with peaks occurring by wet season, and statistically significant positive correlations between mean monthly rainfall and number of captured snakes. However, there were significantly negative correlations between mean monthly temperature and number of captured snakes in two of the three species (Rhinotyphlops congestus; Leptotyphlops cfr. sundewalli).
... In the long-term, it is therefore possible that the species most adapted to large, permanent water bodies, would become increasingly more common than the other, perhaps forcing the other competitor to unsuited niches. A similar phenomenon, although caused by entirely different reasons (i.e., deforestation of terrestrial habitats), was observed in Nigerian cobras, with a generalist savannah species (Naja nigricollis) which challenges a specialist forest species (Naja melanoleuca) in its niche, and increasingly forces the forest specialist to live into spatially reduced niches which are unsuited to the invader species Luiselli 2001;Luiselli et al. 2002). ...
The large-scale effects of habitat alteration produced by oil-industry related pollution on the habitat use of four species
of freshwater turtles (Pelusios castaneus, Pelusios niger, Pelomedusa subrufa, Trionyx triunguis) were studied in the River Niger Delta, southern Nigeria (West Africa) between 1996 and 2004. The numbers of turtle specimens
observed during our study declined drastically in polluted sites, despite a nearly identical field effort. The number of specimens
of all turtle species declined considerably at all habitat types, but complete disappearance in polluted areas was found only
with regard to one habitat type for Trionyx triunguis and two habitat types for Pelomedusa subrufa. The mean values of species dominance and diversity indexes were not statistically significant between pristine and altered
areas. Based on the interspecific similarity in proportional frequencies of turtle specimens found in each habitat type, a
multivariate set of analyses (UPGMA) showed that the turtles were arranged in three ‘ecological’ clusters: a group formed
by Pelomedusa subrufa at both polluted and unpolluted areas and Trionyx triunguis at polluted areas; (ii) a group formed by Pelusios castaneus in polluted areas and Pelusios niger in polluted areas; (iii) a group formed by Pelusios castaneus in unpolluted areas and Pelusios niger in unpolluted areas; however, this latter cluster was not very close, as the linkage distance was close to 80% of Euclidean
distance. Habitat use similarity among turtles in both polluted and unpolluted study areas was evaluated by the use of two
types of overlap formulas (Pianka and Czechanowski) and the use of Monte Carlo randomisations in order to control for the
eventual role of chance in the actual data matrix. These data indicated that, for a pair of species (Pelusios niger vs. Pelusios castaneus), there was a statistically significant increase in the similarity of habitat use in the polluted areas vs. the unpolluted
areas, and that this pattern was not dependent on the chance. Considering that these two species are ecologically and morphologically
similar, we conclude that the most likely consequence at the community level is an increase in the intensity of interspecific
competition for space between Pelusios niger and Pelusios castaneus in the polluted areas. Although the direction of the intensification of this competition process could not be easily predicted,
it is likely that the species which is least adapted to life in main rivers and creeks may be disadvantaged over the other
competitor. The general implications for habitat preservation are also discussed.
... In any case, it is evident that cobras may be very useful models to study the ecological attributes of sexual dimorphism, as well as many other aspects of snake ecology (e.g. see Luiselli & Angelici, 2000;Luiselli, 2001Luiselli, , 2002. ...
Sex-biased differences in dietary habits of snakes are often linked to pronounced sexual size dimorphism in absolute body size or in relative head size. We studied the food habits of free-ranging forest cobras (Naja melanoleuca) in southern Nigeria to find whether any intersexual dietary divergence is present in this species, and measured both museum vouchers and free-ranging specimens to find whether any intersexual divergence in relative head size is present. We demonstrated that: (1) head sizes increases more rapidly with SVL in females than in males, with a result that, at the same body length, the females tended to have significantly larger heads; (2) males and females were nearly identical in dietary habits, both if we consider prey size or prey type; (3) both sexes tended to prey upon relatively little sized preys. It is concluded that traditional evolutionary scenarios for explaining sexual dimorphism and food niche divergence are hardly valid in this case, and we need to look for entirely different hypotheses (e.g. linked to the sexual preference of males for females with larger heads).
... Most commonly, snakebite envenoming in Nigeria results from carpet viper (Echis ocellatus) attacks, which accounts for at least 66% of all snakebites. However its range is primarily limited to the savannah regions of Nigeria [1,6,7,8,9]. Carpet viper envenoming presents with swelling of the bitten limb and a clotting disorder (incoagulable blood in the 20 minutes Whole Blood Clotting Test, 20WBCT) that manifests as local and/or systemic bleeding. ...
Background:
Snakebite envenoming is a major public health problem throughout the rural tropics. Antivenom is effective in reducing mortality and remains the mainstay of therapy. This study aimed to determine the cost-effectiveness of using effective antivenoms for Snakebite envenoming in Nigeria.
Methodology:
Economic analysis was conducted from a public healthcare system perspective. Estimates of model inputs were obtained from the literature. Incremental Cost Effectiveness Ratios (ICERs) were quantified as deaths and Disability-Adjusted-Life-Years (DALY) averted from antivenom therapy. A decision analytic model was developed and analyzed with the following model base-case parameter estimates: type of snakes causing bites, antivenom effectiveness to prevent death, untreated mortality, risk of Early Adverse Reactions (EAR), mortality risk from EAR, mean age at bite and remaining life expectancy, and disability risk (amputation). End-user costs applied included: costs of diagnosing and monitoring envenoming, antivenom drug cost, supportive care, shipping/freezing antivenom, transportation to-and-from hospital and feeding costs while on admission, management of antivenom EAR and free alternative snakebite care for ineffective antivenom.
Principal findings:
We calculated a cost/death averted of ($2330.16) and cost/DALY averted of $99.61 discounted and $56.88 undiscounted. Varying antivenom effectiveness through the 95% confidence interval from 55% to 86% yield a cost/DALY averted of $137.02 to $86.61 respectively. Similarly, varying the prevalence of envenoming caused by carpet viper from 0% to 96% yield a cost/DALY averted of $254.18 to $78.25 respectively. More effective antivenoms and carpet viper envenoming rather than non-carpet viper envenoming were associated with lower cost/DALY averted.
Conclusions/significance:
Treatment of snakebite envenoming in Nigeria is cost-effective with a cost/death averted of $2330.16 and cost/DALY averted of $99.61 discounted, lower than the country's gross domestic product per capita of $1555 (2013). Expanding access to effective antivenoms to larger segments of the Nigerian population should be a considered a priority.
... Movement (displacement from one location to another) has important implications for organisms and is necessary for most aspects of their biology (Nathan, 2008). As a result, studies of the timing of bouts of movement help elucidate the ecological pressures experienced by organisms (Bonnet et al., 1999) and the evolutionary history of the species (Luiselli, 2001). This information is also essential for understanding the life-history and ecology of organisms, and thus developing adequate conservation and management plans (Dodd et al., 2004). ...
... The selective pressure provided by such costs and benefits means that movement is often at least partly synchronized within a population, resulting in predicable patterns (Alexander and Marshall, 1998). Investigating activity patterns of organisms can help elucidate the ecological pressures experienced by organisms (Bonnet et al., 1999) and the evolutionary history of those species (Luiselli, 2001). Studies of activity patterns can also provide estimates of the variation in detection probability of individuals within a population (Sun et al., 2001). ...
Moving from one location to another provides animals with obvious benefits, but also incurs costs. When and how far an animal chooses to move is thus of fundamental importance to all aspects of its biology. We investigated movement patterns in a population of Namaqua Dwarf Adders (Bitis schneidert) in southern Africa through the use of radio telemetry. We measured how many individuals moved at different times of the day, at different times of the year, and differences in displacement frequency between sexes. We also assessed the influence of environmental variables (air temperature, relative humidity, atmospheric pressure, and wind speed) on activity levels. Snakes moved almost exclusively during the day-light hours, despite our expectations from the literature. Namaqua Dwarf Adders show limited seasonal variation in activity levels, with males moving more frequently during spring months than in other seasons. Our analysis indicated that movement was linked most closely to environmental conditions during the winter season, when conditions were generally less suitable for movement. We hypothesize that the observed variation in movement patterns at all temporal scales is the result of the selective pressure imposed by the costs of activity during sub-optimal environmental conditions.
... 'phillipsii', it should be noted that: (1) GR females continue feeding during their pregnancy (Akani et al. 2003) and thus continue to conduct above-ground activity during a phase in which their movement speed is reduced, (2) their annual reproductive cycle is a monoestrous dry season cycle (sensu Saint Girons 1982; Saint Girons & Pfeffer 1971), with vitel-logenesis by the end of the rainy season, oviposition by mid-dry season, and egg hatching at the onset of the rainy season (Butler 1993;Akani et al. 2002a), and (3) many natural predators of Psammophis (e.g., cobras and other snakes) are most active during the interphase between the end of the dry season and the onset of the wet season (e.g., Luiselli 2001;Akani et al. 2002b). The period in which gravid individuals lay their eggs and are thus relatively slow-moving and emaciated coincides with the activity peaks of many natural predators, increasing their risk of being injured (resulting in tail autotomy). ...
... rainforest and for-est^plantation mosaic) (e.g. see Luiselli & Angelici, 2000;Luiselli, 2001). ...
The structure of the snake community was studied between 1996 and 2000 on a transect in the mangrove ecological zone of southern Nigeria, West Africa. In three major habitats, both taxonomical diversity and frequency of observations in relation to sampling effort were investigated. In general terms, the complexity of the snake community appeared less than in other habitats of the same geographic region (i.e. swamp forest and forest–plantation mosaics). In fact, only eighteen species were recorded, whereas 43 species are known to inhabit neighbouring habitats. A Principal Component Analysis allowed arrangement of the various species into two main groups in relation to the habitats of capture: (1) a group of species of rainforest biota (i.e. Toxicodryas blandingii, Thelotornis kirtlandii, Thrasops flavigularis, Rhamnophis aethiopissa, Gastropyxis smaragdina, Grayia smythii, Pseudohaje goldii, Python sebae), and (2) a group of species that, at least in Niger Delta, are typically linked to altered habitats, including derived savannas, plantations and suburbia (i.e. Psammophis cf. phillipsi, Philothamnus cf. nitidus, Hapsidophrys lineatus, Crotaphopeltis hotamboeia, Boaedon lineatus, Naja nigricollis, Python regius). The community structure in terms of food habits and body sizes appeared similar to those of other snake assemblages from different habitats of southern Nigeria. The conservation implications of our results are also discussed.
... Finally, the forest specialising snakes have generally disappeared and the snake fauna of 2002 is again dominated by species that are well known to inhabit deforested areas (see Luiselli and Akani, 2002): Psammophis phillipsii, Philothamnus heterodermus, Crotaphopeltis hotamboeia, and Naja nigricollis. With regard to N. nigricollis, there is good evidence that the colonisation of southern Nigeria by this species has been a relatively recent phenomenon following extensive deforestation during the "oil industry boom" of the sixties and seventies (Luiselli, 2001(Luiselli, , 2002. It seems likely that this rapid expansion will continue and the species will become even more common in this area, posing a serious public health threat for the towns' people because of its highly dangerous venom. ...
Surveys of the herpetofauna of a fresh water river in Southern Nigeria were conducted in 1982 and 2002.
Riparian forest in the area has diminished tenfold between the surveys and the environment nowadays resembles a bushland mosaic. This study therefore provides insight into species succession of an area undergoing major habitat disturbance. Accumulation curves for both years indicated that most amphibian species were captured but there were probably reptile species remaining undiscovered. In 1982, 11 amphibian and 17 reptile species were caught compared to 17 amphibian and 10 reptile species in 2002. The change in available habitat type is mirrored by the successional change in amphibian and reptilian species composition. Forest specialists (e.g., Ptychadena aequiplicata, Chiromantis rufescens, Acanthixalus spinosus, Hyperolius sylvaticus nigeriensis, Kinixys homeana, and Chamaeleo spp.) are no longer present in 2002, whereas more generalist species or those preferring disturbed habitats now dominate (e.g., Hoplobatrachus occipitalis, Ptychadena mascareniensis, P. bibroni, Phrynobatrachus latifrons, Bufo maculatus, Psammophis phillipsii, Philothamnus heterodermus, Crotaphopeltis hotamboeia, and Naja nigricollis). The greater diversity of amphibian species in 2002 maybe a reflection of an increased diversity of microenvironments in the bushland mosaic compared to the forest. The most successful species (Ranidae, esp. Ptychadena) are those that are able to take advantage of multiple habitat types depending on prevailing environmental conditions.
... Lea et al. 2005) and species turnover based on the modifications of the strength and direction of the competitive relationships that occurred under the pristine conditions (e.g. Luiselli 2001Luiselli , 2002Luiselli et al. 2006). ...
We examined the guild structure of geckos at a farmbush–rainforest mosaic area in southern Nigeria, during three independent
survey periods (i.e. dry season of 1997, 2001, and 2005). We used several simulation descriptors (C value, V ratio, number of checkerboard species pairs, number of species combinations), generated by Monte Carlo methods, to contrast
the actual data matrix with the randomly generated data matrix. We calculated the relative availability and use by species
of habitat types and microhabitat types at each of these survey periods and also studied temporal niche aspects. We found
that our gecko guild was composed of six species, including native forest specialists as well as native habitat generalists
and exotic species linked to human-made habitats. Monte Carlo simulations revealed the occurrence of a structure in the guild
under study with regard to habitat type but not with regard to (a) two types of microhabitat uses (i.e. perch height and size
of trees) and (b) daily time. The use of simulation analyses also demonstrated that the various species that were similar
in terms of habitat use partitioned their microhabitat niche, reducing potential interspecific competition. On the other hand,
those species that were clearly separated with regard to habitat type readily frequented the same microhabitats within different
habitat types.
... Our data confirm and further extend the above-mentioned hypothesis, especially with regard to cobras from suburbia and plantation-forest mosaics. In addition, N. nigricollis reduced feeding rates during the peak of the dry season, whereas the same pattern was not found in N. melanoleuca (Luiselli 2001). ...
Two cobra species are found in the forest block of southern Nigeria (West Africa). However, whereas the one species, the spitting cobra (Naja nigricollis), is often found in strongly altered habitats (including suburban areas), the other, the black forest cobra (Naja melanoleuca), is a typical forest species that is currently subject to a rapid de - crease in population abundance because of intensive forest alteration and landscape modification in this part of Africa. We studied whether the body sizes, diets, and feeding strategies of these two species changed in relation to habitat type, and whether the ecological success of the one species versus the other in altered habitats depends upon greater dietary flexibility in prey type or prey size. Therefore, we divided our cobra records into three habitat categories: (1) suburbia, (2) plantation-forest mosaic, and (3) mature forest. We observed that sexual size dimorphism was minor in both species and in all habitat types, and that intersexual differences in prey composition and prey size were also minor. Nevertheless, there was a remarkable ontogenetic change in taxonomic composition of the diet for one species (N. nigricollis, with juveniles taking almost exclusively lizards and adults taking small mammals, birds, and lizards) but not the other. Remarkably, the species that is less adapted to life in suburban areas showed a reduction in mean body size from the forest to suburbia, which may also indicate suboptimal adaptation to strongly altered habitats. Prey size was similar for the two species and in the three habitat types, and the relationships between prey size and predator size were similar. Thus, it seems unlikely that flexibility in prey-size patterns explains the greater colonizing success of N. nigricollis. Nevertheless, and although both species exhibited remarkable dietary flexibility, leading them to prey upon homeotherms as well as heterotherms and upon terrestrial as well as arboreal and even aquatic prey, there were important interspecific differences in prey composition that may explain the ecological success of N. nigricollis. The success of N. nigricollis likely lies not in dietary flexibility but in the consistency with which its juveniles prey upon a single prey type (lizards, mainly Agama agama) that is so abundant in nearly every altered habitat in Nigeria and is a virtually unlimited food resource for young N. nigricollis. However, adults of this species also forage frequently upon commensal rodents and poultry, which may also help it to colonize man-made habitats.
... The absence of a dry season diapause is consistent with data available for other sympatric snake species. Snakes do not aestivate in the dry months in southern Nigeria, including also those species which are typical savannah inhabitants (e.g., the spitting cobra Naja nigricollis, see Luiselli, 2001; 2002). Our habitat and dietary data clearly showed that C. hotamboeia is a highly adaptable species with a wide range of habitats inhabited and a variety of different prey types being eaten. ...
We present field ecological data for the snake Crotaphopeltis hotamboeia (Colubridae) from southern Nigeria. Adult sex-ratio was close to equal, and females attained significantly larger body size than males (on average 470 mm versus 400 mm SVL). Annual above-ground activity peaked during the wet months. A preponderance of snakes were captured in agricultural lands (plantations and farmlands), whereas few snakes were captured in both mangroves and mature forests. Anurans accounted for over 70% of the total prey items; lizards (Scincidae and Agamidae) were also frequently preyed upon. The food niche breadth and diet composition was similar between sexes. There was no apparent ontogenetic dietary change in this species.
... In the present paper, by taking advantage of the most prolonged longitudinal field study (16 years) on the ecology of tropical snake communities available in the world [4,5], we analyze the correlation between the monthly activity patterns of eight species of venomous snakes (belonging to the families Elapidae and Viperidae) and people in rural areas of the Niger Delta, in southern Nigeria. This study region is particularly interesting from the venomous-snake point of view because, having been extensively deforested in the last 50 years, it has been invaded by the spitting cobra (Naja nigricollis), which otherwise tends to inhabit the savannah, to the detriment of the once dominant cobra species (the forest cobra Naja melanoleuca), typically adapted to life in the rainforest [3,67891011. As to Nigeria, the only detailed data on the epidemiology and occurrence of venomous snakebites came from the savannah region in the north of the country [12,13]. ...
Background
Venomous snakes are among the most serious health hazards for rural people in tropical regions of the world. Herein we compare the monthly activity patterns of eight venomous snake species (Elapidae and Viperidae) with those of rural people in the Niger Delta area of southern Nigeria, in order to identify the periods of highest potential risk for persons, and the human group actually at greater risk of snakebite.
Results
We documented that above-ground activity of all venomous snakes peaked in the wet season, and that high snake activity and high human activity were most highly correlated between April and August. In addition, we documented that women and teenagers were at relatively higher risk of encountering a venomous snake than adult males, despite they are less often in the field than men.
Conclusions
Our results suggest that future programs devoted to mitigate the social and health effects of snakebites in the Niger Delta region should involve especially women and teenagers, with ad-hoc education projects if appropriate. We urge that international organizations working on social and health problems in the developing world, such as IRD, DFID, UNDP, should provide advice through specific programs targeted at especially these categories which have been highlighted in comparatively potential higher threat from snakebites than adult men.
Keywords:
Monthly activity; Venomous snakes; Rural people; Nigeria
... It is thus possible that species richness is reduced in oil polluted sites, and is somewhat increased (via succession) in deforested sites without pollutants. Successional changes have also been observed in amphibians in a montane area of south-eastern Nigeria (Lea et al., in press), and in other vertebrates of the Niger Delta (among the cobras Naja nigricollis and Naja melanoleuca; Luiselli, 2001Luiselli, , 2002. This working hypothesis may be important in the development of management strategies for amphibians in tropical forest areas. ...
The Niger Delta (Southern Nigeria) is the main oil-producing region in sub-Saharan Africa. Its biodiversity is very important for the concomitant presence of rainforests and mangroves, and many endemic flora and fauna. Six sites in southern Nigeria, four currently affected by oil industry development but formerly inside the rainforest belt and two in pristine protected areas, were surveyed for amphibians during 1996-2002, in both dry and rainy seasons. Amphibian species diversity was reliably assessed at all study sites, as shown by species accumulation curves. The total number of species found in the two pristine sites was much higher than that found in the four developed sites. Nevertheless, a total of over 6300 amphibian specimens belonging to 28 species were captured at these four sites. Species included three Bufonidae (genera Bufo and Nectophryne), two Pipidae (Silurana and Hymenochirus), nine Ranidae (Hylarana, Ptychadena, Aubria, Conraua, Hoplobatrachus, and Phrynobatrachus), one Arthroleptidae (Arthroleptis), one Rhacophoridae (Chiromantis), one Microhylidae (Phrynomantis), and eleven Hyperoliidae (Hyperolius, Afrixalus, Leptopelis, Phlyctimantis, and Opisthothylax). The four developed study sites were similar in terms of species composition; the most common species were Silurana tropicalis (accounting for about 74% of the total number of specimens captured), Bufo maculatus, Ptychadena spp., Hylarana albolabris, Hoplobatrachus occipitalis, Hyperolius cf. concolor and Afrixalus dorsalis. Greater numbers of species and individuals were captured in the rainy season than in the dry season. In terms of chemo-physical properties of the water at their breeding sites, both adult and larval anurans of several species (e. g., Silurana, Bufo and Ptychadena) were highly adaptable, being able to thrive in anoxic and slightly acidic water with dissolved oxygen from 0.50-1.50 mg l-1 and pH from 5.9-7.2.
... In particular, humidity conditions activity intensity in other tropical reptiles (peaks of activity in rainy periods or when humidity is high, e.g. see Luiselli, 2001 Luiselli, , 2002). Insect abundance at the study site varied throughout the study period. ...
The foraging behavior of Gekko gecko was observed at the visitor complex of the Khao Khiao Open Zoo at the Khao Khiao-Khao Chomphu Wildlife Sanctuary in Chon Buri Province, Thailand. Foraging parameters of G. gecko (foraging period, time spent moving, foraging attempts, foraging success, prey size consumed, and foraging distance) did not vary significantly between males, females, and juveniles. Individuals foraged between 18:01 and 09:00 hrs. Peak emergence time was between 18:01 and 20:00 hrs. Peak retreat time was between 04:01 and 07:00 hrs. Major food items included insects of the orders Lepidoptera, Orthoptera, and Coleoptera. Prey sizes of males, females, and juveniles were not significantly different, indicating no prey size selection. This may have been due to low insect availability in the habitat. Gekko gecko tended to be a sit-and-wait forager spending most of the time waiting for active prey. However, it sometimes foraged more actively when insect abundance was relatively high. Foraging behavior of males tended to be more variable than females and juveniles. In addition, variation in foraging parameters among individuals was noted. Foraging strategies of G. gecko observed in this study are interpreted in the context of optimal foraging theory.
... Indeed, the territory of Nigeria has been widely devastated for industrial expansion, due to the oil exploration activities since the 'oil industry boom' in the 1960s, and massively deforested due to human overpopulation (De Móntelos, 1994). Recent investigations, using the herpetofauna as study model, have shown that the fauna composition in Nigerian areas, which has seen a massive (ten-fold) reduction in forest habitat over the past 20 to 40 years, has changed considerably, with forest specialists having been replaced by more generalist species (Luiselli, 2001(Luiselli, , 2002Lea et al, 2003). Consequently, it is nearly impossible to consider the historical records of the Nigerian herpetofauna as indicative of the current distribution trends (Lea et al., 2005). ...
We report new data on the distribution and habitat of two otter species, Aonyx capensis and Lutra maculicollis, from southern Nigeria. Although preliminary, our investigations suggest that these two species may use the available habitat differently. Lutra maculicollis appears more linked to freshwater streams and Aonyx capensis is mainly restricted to brackish water streams (with mangrove vegetation along the banks) and, more occasionally, to transitional habitats between freshwater and brackish‐water environments. The possible reasons explaining habitat partitioning are discussed.
... Snakes were collected opportunistically, especially during surveys conducted in order to study the ecology of other snake species, notably vipers ( Luiselli 2006bLuiselli , 2006c), cobras ( Luiselli & Angelici 2000;Luiselli 2001;Luiselli et al. 2002), and pythons ( Luiselli et al. 2001). In total, research for house snakes was conducted well over 1000 field days, although obviously Lamprophis individuals were found in only a fraction of these field days. ...
The food niche partitioning of four species of house snakes (Lamprophis fuliginosus, L. olivaceus, L. lineatus, and L. virgatus) was studied in suburban areas of south‐eastern Nigeria, West Africa. Snakes were captured in the field, and their stomach contents were obtained by forced‐squeezing of the ingested bolus. Pseudo‐community analysis and Monte Carlo simulations, by two different algorithms, were used to investigate whether the community under study was randomly assembled along the trophic niche axis. Four hundred and thirty snake individuals were captured: 52 out of 133 L. fuliginosus (32.1%), 31 of 126 (24.6%) L. lineatus, 30 of 108 (27.8%) L. virgatus, and 20 of 63 (31.7%) L. olivaceus had identifiable food contents in the stomach. Lamprophis fuliginosus appeared as the more generalist species, L. lineatus showed some preference for lizards and frogs, L. virgatus for small mammals (rodents and shrews), and L. olivaceus for nestling birds and small mammals. However, null models showed that the community organization was random along the food niche axis by both the randomization algorithms used in this paper. Thus, we concluded that these four snake species do not partition either the quality or the number of the available resources.
... Although basically similar in terms of their ecological traits, they have diverged considerably in terms of habitat use; N. melanoleuca is linked to mature and stable forest and N. nigricollis to variable environments like grassy forest edges, plantations and derived savannas (Luiselli and Angelici 2000). Although still sub-optimally adapted to life in the rainforest, N. nigricollis appears to have extended its range in the last thirty years in response to deforestation (Butler and Reid 1990, Luiselli 2001, thereby challenging other species with a similar niche. As a result of this apparently increased competition, N. melanoleuca has been extirpated from many forested areas where it was common just a few decades ago, whereas the invading N. nigricollis is nowadays abundant and widespread in both deforested areas and mature secondary forests (Luiselli 2003). ...
The role of interspecific competition as a key factor in the ecology of natural communities where species exploit limited resources is well established, and the study of competition dynamics in snake communities has received much attention in recent years. Twenty years ago, an acclaimed review (Toft 1985) suggested that snakes were atypical among vertebrates because sympatric species usually partition the food niche. Here, I review the articles published in the last two decades with the aim of finding any general geographical or guild patterns and assessing if Toft's main conclusion is still supported by new evidence. Where appropriate, I use Monte Carlo simulations to establish whether observed patterns of niche overlap are real, or if they have occurred by chance. My study shows clear congruence in the patterns of coexistence exhibited by snake communities in different regions of the world, i.e.: (1) cold regions of the northern hemisphere (high latitudes and altitudes) exhibit low species richness and a very low, or even absent, potential for interspecific competition; (2) aquatic snakes that form communities in temperate regions generally partition the food type available and exhibit a broad similarity in habitat use with subtle differences in microhabitat use; (3) terrestrial snake communities in temperate regions are very variable in terms of their coexistence dynamics and show no evidence of generalised patterns; (4) sympatric viperids in Europe, North America and, most interestingly, tropical Asia partition the available habitat but not the prey resource; (5) competition is much stronger in tropical snake communities, and the intensity of this process fluctuates throughout the year being most intense during periods of low food availability; (6) in general, tropical snakes partition the food resource (prey type and/or prey size), but when this resource is not partitioned competitive exclusion can occur.
... It is also interesting to note that snake activity on oil palm trees peaked during the dry season, clearly in coincidence with the fruits being ripe. This is relevant because snake activity is conversely much less intense during the dry season than during the wet season in other habitats inside the rainforest area of Nigeria (and in the whole tropical Africa as well) because of the dry general conditions (Luiselli, 2001(Luiselli, , 2006b. Thus, oil palms may furnish ideal microhabitats for snakes and their preys also during the climatically suboptimal dry season. ...
Abstract Aspects of community structure and ecology of snakes were studied in the years 2004–2006 in fields of oil palm trees (Elaeis guineensis) of three study areas in Southern Nigeria. A total of 284 individual snakes, belonging to twelve species of three families (seven Colubridae, four Elapidae, one Viperidae), were recorded, including both sighted and captured individuals (not including in this count the individuals that escaped before identification to species level could be made). All the study areas were nearly identical in terms of species composition. Most snakes (about 67%) were recorded during the dry season months, when the fruits of the oil palm ripe, thus attracting lots of organisms that are potential prey for snakes. The most important food items for oil palm snakes were Agama lizards, birds and rodents, but they also fed on skinks, geckos, fruit bats and tree frogs. Snakes were spotted climbing with peak frequencies occurring in the range of 16–18 m above the ground level. In general, oil palm trees within the range of 16–27 m high harboured higher number of snakes. Climbing snakes were nonrandomly positioned on the trees: the highest percentage of snakes (68%) was lodged between the leaf bases and oil palm fruit bunches. The general implications of the given data are discussed.
... Several publications shows foraging period is regulated by humidity and most of the reptiles will adjust daily and seasonal activity to minimize water loss and they will seek humid or enclosed retreats such as crevices or borrows (Zug, 2001). Luiselli (2001Luiselli ( , 2002) demonstrated that tropical reptiles shows peak activity in rainy season or when the humidity is high. In the present study, particularly this sanctuary, we observed the activity of S. ponticeriana throughout the year and this is possible due to high humidity due to Bay of Bengal. ...
Microhabitat use and activity patterns of Sitana ponticeriana were observed in their natural habitat over two con-secutive years at Balukhand-Konark Wildlife Sanctuary, Orissa, India. Lizards perched above the ground, mainly on herbaceous vegetation, sandy areas, cracks and crevices and small shrubs/bushes of the canopy. During the morning and late afternoon, the lizards favored herbaceous vegetation, and during early afternoon used a variety of microhabitats including shrubs/bushes, cracks and crevices, and root of the trees. Lizards were sighted in large numbers during morning and late afternoon. Sightings declined in the early afternoon with rise in ambient temperature. Daily activity patterns of all lizard size classes typically involved basking in the morning hours fol-lowed by foraging, moving and other activities. S. ponticeriana was found to be active foragers with frequent wandering movement. Foraging behavior did not vary significantly between males and females, whereas juve-niles foraged near their retreats.
The purpose of this chapter is to examine the evidence of a relationship between climatic changes and snake species distribution in relation with the snakebites risk increment against human populations. The global climatic change is a key factor leading to snake species behavioral changes mainly because of the rise of temperature. The variety of venomous snakes and their related potency toward human being have been well documented. Thus, this may serve as a basic knowledge for any preventive act in the face of snake toxins and their caused physiopathological and clinical effects. In addition, several studies have shown that global warming have caused a change in snake habitat and distribution, thus leading to an increase of overlapped human and snake populations living territories which raise up the risk of envenomation. Globally, more than 20,000 deaths occur every year with a high tendency to increase. Thus, consideration of human risk of envenomation may be fundamental to the effective intervention in epidemiological and clinical scales.
Three snake species carpet viper (Echis ocellatus
), black-necked spitting cobra (Naja nigricollis), and puff adder (Bitis arietans) belonging to the Viperidae and Elapidae families are the most important snakes associated with envenoming in Nigeria. The incidence of bites has been reported as 497 per 100,000 population per year with a 12 % natural mortality, with Echis ocellatus accounting for at least 66 % in certain foci. Bites occur more often while victims are farming, herding, or walking mostly among agricultural workers, the economically productive members of society. Carpet viper venom contains a prothrombin-activating procoagulant, hemorrhagin, and cytolytic fractions which cause hemorrhage, incoagulable blood, shock, and local reactions/necrosis. The spitting cobra bite manifests with local tissue reaction and occasionally with bleeding from the site of bite. Classic neurotoxic feature has been observed following Egyptian cobra (N. haje) bites. Cardiotoxicity and renal failure may occasionally occur following bites by the carpet viper and the puff adder. In the laboratory, hematological features are noted, while immunodiagnosis has a role in species identification and monitoring of therapy. Immobilization of the bitten limb is the single most important first aid measure. Effective antivenom remains the only proven remedy for snakebite envenomation, but they are prohibitive, scarce, and often inappropriate and ineffective. Antivenom should be used cautiously when indicated, and use of boots among workers should be the main preventive measures. However, availability, distribution, and utilization of antivenom remain challenging although two new antivenoms (monospecific EchiTAb G and tri-specific EchiTAb-Plus-ICP) raised from Nigerian snake venoms proved very effective and safe in clinical trials. Strategies for broadening antivenom access to endemic rural areas together with instituting quality assurance, standardization, community, and healthcare workers’ education should be implemented. With the advent of antivenomics, health authorities must be helped to select and purchase antivenoms appropriate to their national needs, while manufacturers should be helped in practical ways to improve the safety, efficacy, and potential coverage of their products.
Comparisons of sympatric reptile species were used to assess the variation in niche overlap for food between potential competitors at different trophic levels. Omnivorous tortoises and carnivorous vipers inhabiting the rain-forest region of West Africa were used as study models. Food niche overlap between species increased with habitat alteration in both the independent study systems: tortoises (Kinixys
homeana and Kinixys
erosa) and vipers (Bitis
gabonica and Bitis
nasicornis) showed lower values of Pianka's niche overlap index in the pristine habitat than in the altered habitat, and these differences in overlap values did not depend on chance after Monte Carlo simulations. There were higher inter-habitat food niche overlaps within-species than between-species. Permutation tests (assessed after 5000 iterations) revealed that, for both study systems, the P-values became significantly smaller with fewer resource states, thus showing the niche overlap between species really increases after habitat alteration. The observed increases in food niche overlap between species accomplished with rain-forest habitat degradation in turn may be predicted to have cumulative effects on reducing the level of forest biodiversity.
In this paper, the ecological relationships and the resource partitioning patterns in a two-species system of sympatric aquatic snakes (Grayia
smythii and Afronatrix
anoscopus) from a riverine forest area in southern Nigeria, West Africa, were tested. The monthly availability of their food resources in the field, and the monthly variation in the feeding relationships between these snakes and their preys, were also studied. Food items of 1245 snakes, i.e. 554 Grayia
smythii, and 691 Afronatrix
anoscopus, were examined. The mean body length of Grayia
smythii was significantly larger than that of Afronatrix
anoscopus in any interspecific comparison, i.e. males versus males, females versus females, and females versus males; however, in both species the females attained significantly larger body sizes than the males. 676 prey items were obtained from the stomachs of Afronatrix
anoscopus, and 390 from those of Grayia
smythii. Both species of snake exhibited an increased activity in the open during the wet months, and this increased activity was positively correlated to the higher abundance of prey during the wet season. In both species the diet consisted of a great variety of different amphibian and fish species. Direct interference competition was not observed. The month-by-month dietary patterns exhibited by the two snake species were similar. Mean prey size was significantly larger in the larger species, and the difference in prey size between the two snake species increased during the dry season, i.e. during the period of reduced prey availability. The monthly availability of the three main food types for these snakes varied, and were significantly more abundant during the wet season (April–September). A positive relationship between prey availability and prey use by snakes strongly suggests that the two snake species are predatory generalists, utilizing prey in relation to their abundance in the field.
The food habits of a freshwater pelomedusid turtle (Pelomedusa subrufa) were studied by fecal analysis and stomach flushing in 2 study areas in Nigeria. Males and females were predominantly carnivorous; they fed mainly on fish, tadpoles, and aquatic invertebrates but also on terrestrial vertebrates. Sexes overlapped highly in dietary habits during both wet and dry season. Body size clearly affected diet composition of turtles but did so only during the dry season (with smaller individuals feeding primarily on invertebrates and small vertebrates, and larger individuals on homeotherm vertebrates). There was a strong effect of season on diet composition, and turtles responded to increasing dryness with a shift from a diet based on aquatic organisms during the wet season to a diet based on terrestrial organisms, including small vertebrates, during the dry season.
Distribution and ecology of freshwater and terrestrial Chelonians were studied in eastern Niger Delta of Nigeria. Fifty-two study areas, sparsely distributed along the hydrographic basins of the main rivers and in the main environmental types available in the region, were carefully surveyed over more than two years. Seven Chelonian species were found; four of them (Pelomedusa subrufa olivacea, Pelusios c. castaneus, Kinixys belliana nogueyi, Kinixys erosa) were recorded for the first time inside the Niger Delta region. P. castaneus, P. niger, and K. homeana appeared to be common, whereas K. belliana was extremely rare. In general, species were recorded mainly from the areas characterized by dominant deltaic swamp forest, but the distribution of P. castaneus exceeded by far the distribution of this habitat in the study region. A statistical model (based on logistic regression method) was applied to evaluate the effects of the macro-environmental variables on the local distribution of the various species. It resulted that a determinant factor for the presence of the species was: (i) the presence of Primary Dry Forest for P. castaneus and P. niger; (ii) the presence of Secondary Dry Forest for K. homeana, but the presence of both Shrubland and Farmland/Plantation was not determinant for the presence of any species; (iii) the presence of Primary Swamp Forest for P. niger; (iv) the presence of Secondary Swamp Forest for P. subrufa, K. erosa, and K. homeana; (v) the presence of Mangrove Formations for P. niger and K. homeana; (vi) the presence of Permanent Big Water-Bodies (rivers, creeks) for P. subrufa. The combination of Primary Dry Forest and Secondary Swamp Forest would be determinant for the presence of five of seven species, thus demonstrating to be a crucial combination of habitats from the conservationistic point of view. Principal Component Factor Analysis classified the seven Chelonian species and the eight macro-environmental parameters into five groups: (1) a group formed by P. subrufa and K. belliana; (2) a group formed by the macro-environmental parameters 'Shrubland' and 'Farmland/Plantation'; (3) a group, relatively close to the group (2), formed by the macro-environmental parameters 'Secondary Dry Forest' and 'Secondary Swamp Forest', and by the species K. erosa and K. homeana; (4) a group formed by the macro-environmental parameters 'Primary Dry Forest', 'Primary Swamp Forest', and 'Permanent big Water Body', and by the species P. castaneus, P. niger, and Trionyx triunguis; (5) a group formed by the macro-environmental parameter 'Mangrove' alone. Phenology data suggested that only one of seven, if any, species could aestivate during the dry season: P. subrufa.
Alteration of the natural vegetation of Sierra Leone, largely degradation of the forests by farming within the forest zone, has had an effect on the snake fauna in that many savanna species have been able to penetrate the forest zone to a considerable extent. Other savanna species have been unable to take advantage of man-made derived savanna and remain within the natural savanna zone, while many of the true forest species are rare or of local occurrence only.
Two cobra species are found in the forest block of southern Nigeria (West Africa). However, whereas the one species, the spitting cobra (Naja nigricollis), is often found in strongly altered habitats (including suburban areas), the other, the black forest cobra (Naja melanoleuca), is a typical forest species that is currently subject to a rapid de - crease in population abundance because of intensive forest alteration and landscape modification in this part of Africa. We studied whether the body sizes, diets, and feeding strategies of these two species changed in relation to habitat type, and whether the ecological success of the one species versus the other in altered habitats depends upon greater dietary flexibility in prey type or prey size. Therefore, we divided our cobra records into three habitat categories: (1) suburbia, (2) plantation-forest mosaic, and (3) mature forest. We observed that sexual size dimorphism was minor in both species and in all habitat types, and that intersexual differences in prey composition and prey size were also minor. Nevertheless, there was a remarkable ontogenetic change in taxonomic composition of the diet for one species (N. nigricollis, with juveniles taking almost exclusively lizards and adults taking small mammals, birds, and lizards) but not the other. Remarkably, the species that is less adapted to life in suburban areas showed a reduction in mean body size from the forest to suburbia, which may also indicate suboptimal adaptation to strongly altered habitats. Prey size was similar for the two species and in the three habitat types, and the relationships between prey size and predator size were similar. Thus, it seems unlikely that flexibility in prey-size patterns explains the greater colonizing success of N. nigricollis. Nevertheless, and although both species exhibited remarkable dietary flexibility, leading them to prey upon homeotherms as well as heterotherms and upon terrestrial as well as arboreal and even aquatic prey, there were important interspecific differences in prey composition that may explain the ecological success of N. nigricollis. The success of N. nigricollis likely lies not in dietary flexibility but in the consistency with which its juveniles prey upon a single prey type (lizards, mainly Agama agama) that is so abundant in nearly every altered habitat in Nigeria and is a virtually unlimited food resource for young N. nigricollis. However, adults of this species also forage frequently upon commensal rodents and poultry, which may also help it to colonize man-made habitats.
Aspects of comparative ecology were studied in the spitting cobra, Naja nigricollis, and the black forest cobra, Naja melanoleuca, from southeastern Nigeria. Both species were common and widely distributed in the study region. Naja melanoleuca inhabited mainly primary and secondary forest patches, but also plantations and suburbia. The two species differed significantly in terms of habitat types frequented. A logistic regression model showed that the presence of N. melanoleuca was significantly influenced by the presence of a unique macrohabitat category (primary swamp-forest), whereas the presence or absence of N. nigricollis did not correlate with any macrohabitat categories. Aboveground activity of both species was lowest during the hottest months of the dry season (December to February) and peaked during the wettest months of the wet season (June and July). Sexual size dimorphism was minor in both species, but N. melanoleuca attained a significantly greater body size than N. nigricollis. The adult sex ratio was approximately 1:1 in both species. Both species preyed on a wide variety of small to medium-sized vertebrates; adult N. melanoleuca fed with similar frequency upon mammals, frogs, and fish, whereas the young fed mainly upon fish. Adult N. nigricollis preyed mainly on lizards and to a lesser degree on mammals and frogs, whereas the young preyed with similar frequency upon lizards, frogs, and fish. Many of the prey of both these cobra species were terrestrial (rodents and shrews), but semiaquatic (frogs) and aquatic (fish) prey were also frequently taken. In both N. melanoleuca and N. nigricollis, egg laying probably occurred over a broad time-span, there was a positive relationship between maternal size and litter size, and reproduction first occurred when individuals attained a low proportion of their maximum size.
The food resource partitioning in a community of snakes from a moist rainforest of south-eastern Nigeria (Eket, Akwa-Ibom State) is studied in the present paper. The community consisted of 24 different species, belonging to different families and ecological guilds: some species were terrestrial, some were semi-aquatic, and others were arboreal. Six species were primarily mammal-eating, two were bird-eating, four were lizard-eating, three were frog-eating, one species fed on both mammals and birds, and one species fed on both fish and frogs. A UPGMA tree diagram showed that three clusters of snakes are formed on the basis of their diet composition: a cluster formed by the two large arboreal species (Dendroaspis jamesoni and Boiga blandingi), another formed by the group of the terrestrial mammal-eating Calabaria reinhardti, Bitis gabonica, and Bitis nasicornis, and the third cluster formed by the lizard-eating Psammophis phillipsi, Thelotornis kirtlandii, and Gastropyxis smaragdina. The relationships between these and the other taxa remain unclear. In terms of both frequency of occurrence of the various prey types and biomass contribution of each prey type, the semi-aquatic snakes showed the narrowest niche breadth values and the terrestrial snakes showed the widest niche breadth values. The overlap values were not significantly correlated with the rank of phylogenetic distance. The mean overlap values calculated between species belonging to a same guild were significantly higher than those calculated between species belonging to different guilds, but the mean overlap values between species belonging to a same guild did not differ significantly among guilds. Prey size and predator size (total length) were positively correlated. There was no statistically significant difference between snake guilds as far as mean prey size is concerned, but the various species within each guild differed significantly in terms of mean prey size.
Contains 3 folded maps (scale 1:5.000.000), and a legend Map(s) inclu.
A study of the fauna (Amphibia, Reptilia, Aves, Mammalia) of the Niger Delta region of Nigeria and evaluation of the impacts caused by the working of two natural gas tracing pipelines, Ecosystem s.r.l
- E Politano
Politano E. (Ed.), A study of the fauna (Amphibia, Reptilia,
Aves, Mammalia) of the Niger Delta region of Nigeria and
evaluation of the impacts caused by the working of two natural
gas tracing pipelines, Ecosystem s.r.l., Bari, 1997.
Ecosystem s.r.l. (Bari), Amertex Oil and Gas Ltd. (Lagos), Italian Foundation of Vertebrate Zoology (Rome) Additional funding came from the Rivers State University of Science and Technology Tooze spent much pleasant time with us in the field, and gave some helpful observations
- L Bikikoro
- B Bolton
- C Effah
- M A Inyang
- S Kalio
- A Sigismondi
Acknowledgments. I am indebted with several companies which supported our continued research in Nigeria. In particular, we extend our thanks to Agip-Petroli S.p.A. (Milano), Aquater S.p.A. (S. Lorenzo in Campo), Technip, Kellogg Brown & Root, Japan Gas Company Corporation (T.S.K.J.) Nigeria Ltd. (Port Harcourt), Ni-gerian Agip Oil Company Ltd. (Port Harcourt), Nigerian Agip Exploration Ltd. (Lagos), Ecosystem s.r.l. (Bari), Amertex Oil and Gas Ltd. (Lagos), Italian Foundation of Vertebrate Zoology (Rome), Chelonian Research Foundation (Lunenburg), and Demetra S.p.A. (Fano and Rome). Additional funding came from the Rivers State University of Science and Technology (Port Harcourt). E. Politano, I.F. Barieenee, B. Ekeke, L.D. Otonye, D. Capizzi, A. Pazienti, G. Paoloni, L. Rugiero, J.S. Ekanem, B. Egbide, L. Ude, L. Bikikoro, B. Bolton, C. Effah, M.A. Inyang, S. Kalio, A. Sigismondi, and Z. Tooze spent much pleasant time with us in the field, and gave some helpful observations. G.C. Akani and F.M. Angelici kindly permitted me to use our common cobra data-set. A. van Noordwijk, G.C. Akani, F.M. Angelici, M. Capula and S. Akele offered helpful critical comments on a previous version of the manuscript. REFERENCES
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