Herpetofauna survey, community structure, and ecological patterns in the Niger Delta (Rivers State, Southern Nigeria)

Urbanization rapidly alters wildlife habitats leading to population declines. However, certain species are able to adapt to the landscape changes. This research investigated the ecological use by small vertebrates of an un- completed building in an urban area of Rivers State, Nigeria. Sampling lasted from January 2016 to December 2018. As a routine, we carefully moved round the building dislodging stones, panels and checking for concealed small vertebrates within the multiple holes of the walls. The species relative abundance data was generated by combining the number of individuals preyed on by predators as well as those captured, counted and tagged. This research revealed the presence of 173 individuals of 16 species belonging to 11 vertebrate families (Accipitridae, Agamidae, Bufonidae, Colubridae, Columbidae, Gekkonidae, Lamprophiidae, Muridae, Ptychadenidae, Sciuridae and Scincidae). Reptilians constituted 71.10% of the observations; the rainbow lizard (Agama agama) with a percentage frequency of 25.43% was the most common and abundant species from the community. The Olive house snake (Lamprophis olivaceus) with a 0.58% frequency of occurrence was the least encountered species from the building. The existence of these animals within the confines of the studied structure is largely based on the economic condition of the owners of the building; the improvement in the financial condition of such owners would negatively trigger the unfortunate extirpation of the non-flying species from the area. We therefore, recommend the capture and transfer of such disturbed animals to forested zones before the completion of the building. More so, city planners and urban dwellers should also make concise efforts to create zones of habitation for displaced urban wildlife.

Suitable habitats for anurans can be found in the ever-growing tropical urban environments but anurans’ adaptations to urban conditions, including their trophic ecology remain largely unknown. We studied the food habits of two generalist, widespread West African Sclerophrys adult toads: African common (S. regularis) and Hallowell's toad (S. maculata). The first was studied in Lomé (Togo), Cotonou (Benin) and Ikeja (Nigeria), and the second in Port Harcourt and Ikeja (both Nigeria); the latter city represents the only studied sympatric occurrence. Mean dietary overlap between population pairs was relatively high, and diet composition of the two species when sympatric did not differ significantly. Food niche width was significantly positively correlated with local rainfall in both species, and diet composition changed significantly between the dry and wet seasons. Diversity metrics revealed that females had a more diversified diet, with higher evenness and lower dominance index values than males. The diet of both species was not correlated to prey type availability, in both the wet and dry season. Both toad species targeted specific food items rather than opportunistically consume prey as observed in most anurans which may be a response to high anuran diversity typically found in the tropics or an adjustment to urban habitats.

Most species of lizard are either diurnal or nocturnal, and it is extremely rare to find species that operate both diurnally and nocturnally, or that may shift from diurnality to partial nocturnality when conditions allow. However, niche expansion from diurnal to nocturnal habits (often referred to as the night-light niche) has rarely been reported in lizards (mainly in Anoles), and mostly through anecdotal reports. In West Africa, the rainbow lizard Agama agama is a conspicuous species across the region but also lives in suburban areas of towns and villages. It is a diurnal sun-basker operating at relatively high body temperatures of 36o C and higher. In this paper we describe a night-light niche expansion, i.e. nocturnal foraging and thermoregulation, in a small number of A. agama populations living in suburban areas. These lizards utilised radiant heat from incandescent light bulbs situated on the walls of buildings to mostly achieve target body temperatures and forage for and fed on 5 different groups of invertebrates. Foraging lizards had significantly higher body temperatures than inactive lizards. However variance in body temperature was significantly greater in foraging lizards than in inactive lizards probably due to the necessity to shuttle between the incandescent night lights and cooler foraging areas during activity, a known cost of thermoregulation. Regression analysis of body temperatures against time of night in foraging lizards supported the notion that the lizards were maintaining body temperatures by actively thermoregulating whilst in inactive non-basking resting lizards during the same time period body temperatures declined. Although our results indicate a potential thermoregulatory benefit from using the night-light shift, we cannot be certain that this benefit is the direct cause of the shift, rather than an additional advantage when foraging.

1. The spatial and trophic ecology of Afrotropical gecko populations are poorly known. Here, we report ecological observations on Brook’s House Gecko (Hemidactylus angulatus), a widespread gekkonid species, in the Rivers State University of Science and Technology campus, Port Harcourt, Nigeria. 2. A total of 488 gecko individuals were recorded during the present study, in two surveyed habitat types: (i) plantation trees (PTH) and (ii) buildings (BDH). In PTH, they were observed in 13 out of 15 species of trees present in the study area, with their (log) frequency of sightings being positively correlated to the (log) frequency of surveyed trees per species. 3. The geckos used substantially the non-native ornamental trees of the PTH habitat. Pinus ponderosa and Elaeis guineensis were significantly preferred by geckos over all the other tree species. 4. Geckos also used frequently the buildings (BDH habitat) at the university campus. There was no correlation between (log) area of each building and (log) number of observed lizards. 5. We collected faeces from 51 gecko individuals in dry season and 66 in wet season. There were no significant dietary differences between seasons, with Diptera and adult Lepidoptera dominating in the diet. 6. Dietary habits of geckos differed significantly between habitat types, with Araneae and Lepidoptera (larvae) being eaten much more frequently in BDH, and in Coleoptera and Isopoda that were eaten much more frequently in PTH The diversity dietary metrics (Shannon and Dominance indices) were very similar either between seasons or between habitats. 7. Our independent set of analyses (diet diversity metrics; contingency tables on taxonomic dietary composition and rank-abundance diagrams) showed that lizards exhibited a same feeding strategy in both wet and dry seasons as well as in the two habitat types, although the diet composition differed significantly between habitats. 8. A “mixed” foraging strategy was apparently used by Hemidactylus angulatus at the study area, as also observed in other gekkonid species from elsewhere.

Throughout Africa, feelings towards crocodiles vary according to the danger or fear experienced by communities living alongside them. Crocodile conservation programs must therefore be based on reliable assessments of cultural attitudes towards these reptiles. In this study, we interviewed a random sample of 300 persons in six states in southern Nigeria to determine their perception of crocodiles. Our results revealed that most respondents were very familiar with crocodiles, animals being regularly sighted but only in small numbers. Most interviewees were aware of just two crocodile types, consistently describing the dwarf crocodile (Osteolaemus tetraspis) and the West African Nile crocodile (Crocodylus [niloticus] suchus); only a minority of respondents reporting they were aware of the West African slender-snouted crocodile (Mecistops cataphractus).

Actuarial senescence appears to be a common process, and senescence patterns are highly variable across the tree of life. To date, studies on animal senescence have largely focused on model species, such as as fruit flies, humans and a few other endotherms. In contrast, our knowledge about ageing remains fragmentary in ectotherm vertebrates, such as reptiles. Here, we examined life history and age-dependent mortality patterns in three tropical tortoises (Kinixys erosa, Kinixys homeana and Kinixys nogueyi) and snakes (Bitis gabonica, Bitis nasicornis and Causus maculatus). Our study revealed that tortoises of the genus Kinixys had a higher survival and a lower recruitment than snakes of the genera Bitis and Causus, indicating a slower life history. Furthermore, we confirmed that survival decreased more slowly with age in tortoises than in snakes. In addition, we highlighted contrasting patterns of age-dependent mortality among the three genera. In Kinixys, the relationship between mortality rate and age was positive and linear, suggesting gradual senescence over tortoise lifetime. In contrast, the relationship between mortality rate and age was negative and sharp in Bitis and Causus, possibly owing to a ‘negative senescence’. Our study is one of the few to have examined and compared the demography and age-dependent mortality patterns of tropical reptiles. Among other things, our results suggest that although negative senescence has never been reported in endotherm vertebrates, it could be a common phenomenon in ectotherms.

The concentrations of some heavy metals (copper, chromium, lead and cadmium) were determined in soil and organs (liver, lungs, gastro intestinal tract – GIT) and muscle) from the frog Hoplobatrachus occipitalis from the vicinity of an oilfield flowsation in Agbada field (Agbada FS), and a suburban area (Rumuesara) in Rivers State, Nigeria. Monthly samples were collectd and analysed over a period of eighteen months and analysed by Atomic Absorption Spectrophotometry. Mean Cr concentrations were significantly higher in soil samples from Agbada FS. The highest value for Cu was observed in the sample from Agbada FS. Presumably, the activities at the Agbada flowstation represent a veritable source of contaamination with Cr and Cu. However, marginally higher but non-sginificant mean values for Pb adn Cd were obtained from Rumesara probably due to contamination from petroleum products and other materials commonly in use at Rumuesara. In the organs, similar patterns of accumulation were observed for lead and chromium whereby lung>GIT> muscle>liver. For cadmium the order was lungs>liver>GIT>muscle while the sequence for copper was liver>lungs>GIT:>muscle. Generally, higher concentrations of the heavy metals were found in anuran tissues than in the soil samples. There was significant correlation between copper/chromium in soil and liver (p<0.05); but no significant correlation between lead and cadmium in soil and that of any of the organs (p>0.05). The mean concentrations recorded for all the metals in the organs examined, exceeded the world health organization permissible limits, so the consumption of the frog from the study area by humans is discouraged.

Urbanization has been reported to adversely affect the health status of amphibians. We examined the health status of four amphibian species (Ptychadena spp., Hoplobatrachus occipitalis, Sclerophys spp. and Hylarana galamensis) from an urban settlement (Rumuesara) and a forested location (Agbada), using the condition factor, CF. Higher condition factor values of Ptychadena spp. were obtained in specimens from Agbada while the CF of H. occipitalis was higher in specimens from Rumuesara, although the differences were not statistically significant. Generally, CF was higher in male specimens from both locations. No significant differences were found between sexes except in Ptychadena species from Agbada where it was significantly higher in the females. Condition factor of all species investigated was greater than one. Pearson correlation between snout-vent length and body mass was statistically significant (P<0.01), indicating good health status of the amphibians from both locations. Urbanization did not significantly affect the CF of amphibians from Rumuesara when compared with that of specimens from the forested location, Agbada.

Understanding age-dependent mortality processes is a critical challenge for population biologists. Actuarial senescence appears to be a common process across the tree of life. Senescence patterns are highly variable in pluricellular organisms: senescence can be gradual or sharp and its onset may be early or delayed. By contrast, studies revealed that organisms may also not experience senescence at all while others display a negative senescence; i.e. a decrease of mortality rate with age. To date, studies on senescence have largely focused on human and other endotherm vertebrates, limiting our understanding of senescence in amniotes as a whole. By contrast, few have examined the diversity of senescence patterns in ectotherm vertebrates as reptiles. Here, we examined population dynamics and age-dependent mortality patterns in three tropical tortoises (Kinixys erosa, Kinixys homeana, Kinixys nogueyi) and snakes (Bitis gabonica, Bitis nasicornis, Causus maculatus). Our study revealed that tortoises of Kinixys genus had a higher survival and a lower recruitment than snakes of the genera Bitis and Causus, indicating that they have a slower life history. Furthermore, we showed that survival more slowly decreased with age in tortoises than in snakes. In addition, we highlighted contrasted patterns of age-dependent mortality in the three genera. In Kinixys, the relationship between mortality rate and age was positive and linear, suggesting gradual senescence over tortoise lifetime. By contrast, the relationship between mortality rate and age was negative and sharp in Bitis and Causus, possibly due to a negative senescence starting early in life. Our study highlighted various age-dependent mortality patterns in tropical reptiles. It also contributed to extend our knowledge of senescence in ectotherm vertebrates whose the demography is still poorly understood. In addition, while negative senescence has never been reported in endotherm vertebrates, our results showed that it can be common phenomenon in ectotherms.

We report the first known occurrence of the Foulassi Screeching Frog, Arthroleptis adelphus (Perret, 1966), from Nigeria. A specimen of A. adelphus was collected during herpetological survey work conducted in Cross River National Park, south-eastern Nigeria. Morphometrics and mitochondrial 16S rRNA gene confirm identity of the specimen. Matrilineal genealogy reveals a sister relationship of A. adelphus from Nigeria with individuals from south-western Cameroon. Genetic analysis further shows geographic structuring and divergence among populations of A. adelphus from the Guineo–Congolian forest region. We offer updates to the IUCN geographic range of A. adelphus .

A collection of rigorously peer-reviewed articles of broad coverage on the ecology and conservation of West and Central African forests, with authors from an international suite of countries, including Germany, UK, Togo, Nigeria, Cameroun, Italy, Burkina Faso, and many other countries

No field studies have been conducted characterizing the habitat characteristics and eventual spatial resource partitioning between softshell turtles (family Trionychidae) in West and Central Africa. Here, we analyze the macrohabitat, microhabitat (along four variables), and apparent population abundance of Nile Soft-shelled Terrapin (Trionyx triunguis) and Senegal Flap-shelled Terrapin (Cyclanorbis senegalensis) by collating 22 y of data (1995–2017) from 11 countries in West and Central Africa. We found that the carapace length of T. triunguis was significantly larger than C. senegalensis. Qualitative observations on the apparent population abundance suggests that the smaller species was relatively common in most of the sampled sites, whereas the larger species was often rare or even very rare. We found the two species in a variety of macrohabitats, and a clear difference between them was not apparent in our data. Instead, at the microhabitat scale, the two species differed significantly in all the four microhabitat variables considered in this study. Overall, the data we present are consistent with a general pattern of resource partitioning previously highlighted for freshwater turtle communities worldwide, where sympatric species tend to partition the microhabitat resources and not the available macrohabitats. Because T. triunguis seemed rare in most of the surveyed sites, we suggest that more field investigations should be undertaken to understand whether the current status of Vulnerable is suited for this species, or if a more highly threatened category on the Red List should be adopted.

The West African Black Mud Turtle, Pelusios niger (Family Pelomedusidae), is a freshwater turtle of medium size (carapace length to 35.5 cm) endemic to permanent wetlands in forested areas of West Africa, and is recognizable within the genus by its hooked maxillary beak. A median keel on the posterior vertebral scutes persists throughout life. The wide, blackish plastron is either uniformly dark or bears a lighter streak along the midline seam. Its field ecology has been studied extensively and quantitatively only in southern Nigeria, with home range, habitat selection, and food habits having been analyzed. The species is omnivorous (but predominantly carnivorous), with dietary composition shifting by season and by site, and also in relation to the extent of pollution of its habitat. Adult sex-ratio is even (1:1). Pelusios niger may potentially be a competitor of P. castaneus in forest water bodies of southern Nigeria, and especially in oil-polluted areas, due to an increased niche similarity between these species along the spatial and food niche axes. The species is locally abundant (especially in Nigeria and in Gabon), and its populations appear to be relatively stable. Nonetheless, its main habitats (i.e., forest streams and rivers inside the continuous forest zone) are under threat, and loss of habitat may cause a decline of the populations of this species in the years to come.

The ecology of gekkonids occurring in African forests is poorly known. In this paper, we analyse the feeding habits of a guild of sympatric geckos at a forest‐plantation mosaic area in south‐eastern Nigeria. Faeces were collected on handling from Hemidactylus brookii, H. fasciatus, H. intestinalis, H. mabouia, H. echinus, and Lygodactylus conraui. All species proved to be dietary generalists, with diets based almost entirely on arthropods. However, food niche overlap values between pairs of species were relatively low and Monte Carlo simulations (with RA2 and RA3 algorithms) showed that the overlap values between H. fasciatus and H. intestinalis were significantly higher than those observed for other pairs of species. Monte‐Carlo simulations on co‐occurrence estimators (C‐score, V‐ratio, and number of species combinations) revealed that the gecko guild was not competitively structured along the trophic niche dimension.

The ecology of gekkonids occurring in African forests is poorly known. In this paper, we analyse the feeding habits of a guild of sympatric geckos at a forest-plantation mosaic area in south-eastern Nigeria. Faeces were collected on handling from Hemidactylus brookii, H. fasciatus, H. intestinalis, H. mabouia, H. echinus, and Lygodactylus conraui. All species proved to be dietary generalists, with diets based almost entirely on arthropods. However, food niche overlap values between pairs of species were relatively low and Monte Carlo simulations (with RA2 and RA3 algorithms) showed that the overlap values between H. fasciatus and H. intestinalis were significantly higher than those observed for outer pairs of species. Monte-Carlo simulations on co-occurrence estimators (C-score, V-ratio, and number of species combinations) revealed that the gecko guild was not competitively structured along the trophic niche dimension.

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.

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.

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.

The ecology of the blindsnake, Typhlops punctatus punctatus in five selected study plots in the River Niger Delta (Port Harcourt, Nigeria) was investigated. A total of 207 specimens were collected, 43% occurring under stones, 30% under leaf litter and 15% under logs. The number of snakes found under cover objects was significantly influenced by the number of cover objects lifted up. GLM analysis revealed that there was no difference in terms of number of snakes observed, once the relative effect of the different number of cover objects lifted up was taken into account, either among study plots or among types of cover objects. These snakes appeared to have a strong affinity for loamy soils, with moisture content of 8–18%, high organic matter (1–6%) and slightly acid pH of 5.4–6.9. Stomach content analysis revealed that these snakes fed mainly upon ants and termites. A case of predation by the toad Bufo maculatus on a juvenile blindsnake was also reported.

The African fire skink, Lygosoma fernandi, is a poorly known, large scincid species inhabiting the rainforests of central and western Africa. Aspects of its field ecology (daily and seasonal activity patterns and habitat selection) were studied at a coastal site in southeastern Nigeria. Skinks were studied by both pitfall traps and visual encounter survey techniques for a total of 40 field days (20 in the dry and 20 in the wet season) by nine researchers. Over 98% of skinks (n=106) were active between 1715 and 1830, while only 2% were found out of their burrow earlier in the day. Above-ground activity was significantly more intense during the wet season. Lygosoma fernandi selected habitat types regardless of their relative availability in the field, and showed a clear preference for swamp forest and lowland forest patches. Mangrove swamps were, on the other hand, actively avoided.

Lygodactylus conraui is the only green gecko species occurring in West Africa, and is also one of the smallest gecko species of the African continent. Here, some aspects of the natural history of this species are documented for Rivers State, southern Nigeria. In total, 108 L. conraui individuals were observed in 1996-2016 in southern Nigeria. Individuals of this species were mainly observed at originally forested sites that were heavily altered by human inclusion. In southern Nigeria, L. conraui may be a pioneer species that quickly colonises microhabitats at ecotonal sites of recently deforested or rapidly re-growing forest areas. In each site, the number of observed lizards was significantly positively influenced by the percent of available shade within each habitat type. These geckos were found most commonly at 0.8-3.2 m height. Their activity was especially concentrated during the wet season months. Mean distance between individuals in each demes was 1.35 m (range 0.70-3.2 m).