Abstract
The dwarf crocodile Osteolaemus tetraspis is globally listed as Vulnerable, yet remains heavily harvested across West and Central Africa particularly in the Niger Delta, Nigeria. This study assessed the spatio-temporal variation in the relative abundance of O. tetraspis across three major bushmeat markets: Uwa (Edo State), Edumanon (Bayelsa State), and Ogbe-Ijaw (Delta State) to inform conservation and management interventions. Bushmeat market surveys were conducted fortnightly between October 2021 and April 2022. All crocodiles encountered were counted and measured across three size classes (60, 90, and ≥ 120 cm). A negative-binomial generalized linear mixed model (GLMM) was fitted to monthly counts of Osteolaemus tetraspis to account for overdispersion in the abundance data. Temporal (Month) and spatial (Market location) effects, as well as their interaction, were treated as fixed effects. A total of 158 O. tetraspis individuals were recorded, dominated by medium-sized (39.24%) and large-sized (39.24%) individuals. Uwa accounted for the highest proportion of individuals (60.76%), followed by Edumanon (25.32%) and Ogbe-Ijaw (13.92%). The negative-binomial GLMM model indicated significant effects of Month (χ²₆ = 19.82, p < 0.01) and Market Location (χ²₂ = 10.46, p = 0.005), as well as a significant Month × Market interaction (χ²₁₂ = 23.17, p = 0.018), demonstrating that temporal patterns in abundance differed among markets. The marginal R² value (R²ₘ = 0.48) indicated that fixed effects accounted for a substantial variation in monthly abundance. Temporal declines were pronounced in April across all markets. Trade pressure on O. tetraspis is greatest during the dry-season months of October–February, with Uwa and Edumanon emerged as the principal markets contributing to the observed trade. The dominance of medium- and large-bodied crocodiles in the trade raises concerns about depletion of reproductive adults and long-term population collapse. These findings highlight the need for market-specific regulatory strategies, dry-season harvest restrictions, enhanced monitoring in high-pressure markets, and livelihood support programs. Integrating these actions with community-based conservation are critical for sustaining remaining O. tetraspis populations in the Niger Delta.
Supplementary Information
The online version contains supplementary material available at 10.1186/s40850-026-00281-3.
Keywords: Dwarf crocodile, Osteolaemus tetraspis, Relative abundance, Bushmeat trade, Socio-demographics, Conservation, Niger Delta, Market ecology
Article impact statement
The dwarf crocodile, a highly valued species, is under threat due to unsustainable trade practices in Nigeria's Niger Delta Region. Our research exposes the alarming rate of exploitation and highlights the urgent need for conservation action. To safeguard the future of this iconic species, we advocate for community-led conservation initiatives, education, and policy reforms that promote sustainable wildlife management.
Supplementary Information
The online version contains supplementary material available at 10.1186/s40850-026-00281-3.
Introduction
The African dwarf crocodile (Osteolaemus tetraspis) is the smallest extant member of the crocodilian family, distinguished by its short blunt snout, bony dorsal scutes, and cryptic, nocturnal lifestyle. It occurs in tropical lowland forests, swampy wetlands, mangrove ecosystems, and slow-flowing rivers across West and Central Africa ([17]; IUCN, [25]). Adults typically measure between 1.5 and 1.9 m, though exceptional males may exceed 2 m in length, weighing up to 80 kg, while females average around 40 kg [26, 37]. The diet is opportunistic, consisting mainly of crustaceans, mollusks, fish, amphibians, and occasionally small mammals, making the species a key mid-level predator in aquatic forest ecosystems [17, 41].
Reproductive biology is poorly studied but available evidence indicates clutch sizes of 10–20 eggs, with nests often constructed from vegetation mounds close to water bodies [15]. Unlike larger crocodilians such as Crocodylus niloticus, dwarf crocodiles show slower growth rates and longer generational intervals, traits that make them highly vulnerable to overexploitation [10]. Despite these ecological adaptations, there remain significant gaps in population data across most of its range, making effective conservation strategies challenging (IUCN, [25]).
Although widely distributed, O. tetraspis is classified as Vulnerable by the IUCN due to population declines driven by habitat degradation and hunting (IUCN, [25]). In the Niger Delta, one of Nigeria’s biodiversity hotspots, anthropogenic activities such as deforestation, oil exploration, agricultural expansion, and wetland reclamation have caused rapid habitat loss [12]. Wetland fragmentation reduces suitable breeding sites and increases human–crocodile encounters, further intensifying exploitation risks. A major driver of decline is the bushmeat trade, which remains a culturally and economically important livelihood strategy in West and Central Africa [13]. Dwarf crocodiles are particularly vulnerable because they are easily captured at night using torches and nets, and their small size makes them manageable to transport compared to larger crocodilian species [33]. Bushmeat hunting pressure has already caused local declines in populations of saltwater crocodiles in Asia [42], and similar patterns are increasingly evident for O. tetraspis in Nigeria and Cameroon [3, 35]. The expanding human population and its associated activities, such as hunting, deforestation, habitat destruction, and habitat fragmentation, pose substantial threats to many species (IUCN, [25]). The unsustainable exploitation of species for commercial gain has also led to drastic population declines, as seen in the case of saltwater crocodiles [42–44]. Climate change also poses emerging risks, as rising temperatures and altered rainfall patterns affect wetland hydrology and nesting ecology [21, 39]. With juveniles dependent on aquatic habitats for survival, any shift in seasonal flooding could exacerbate recruitment bottlenecks in the wild.
The taxonomic status of African dwarf crocodiles remains contentious. Initially described as Osteoblepharon osborni by Schmidt in 1919, later revisions grouped specimens under Osteolaemus tetraspis with two putative subspecies: O. tetraspis tetraspis and O. tetraspis osborni. However, recent molecular and phylogenomic analyses have revealed substantial cryptic diversity, suggesting at least three distinct evolutionary lineages across Africa [16, 39]. One of these lineages is thought to occur in West Africa, possibly representing an undescribed species that includes populations from Nigeria and Ghana [11, 16].
This taxonomic uncertainty has direct implications for conservation. If distinct lineages exist, local extirpation in Nigeria may equate to the global extinction of a unique species. Conservation policies have historically treated Osteolaemus as a single taxon, but accurate species delimitation is critical for setting priorities under both IUCN and CITES frameworks [39]. Without urgent taxonomic resolution, conservation management may fail to recognize distinct evolutionary units at risk.
Osteolaemus tetraspis is widely distributed across the coast of West Africa. In Nigeria, particularly in the Niger Delta region, the trade in O. tetraspis is both widespread and persistent [13, 35]. Despite its persistence, the bushmeat trade in O. tetraspis has received limited scientific attention in Nigeria. Most conservation efforts have focused on charismatic megafauna such as elephants and primates, while reptiles remain under-represented [3, 23]. Yet reptiles constitute a significant proportion of bushmeat in rural markets, and their overexploitation may undermine ecological stability in aquatic ecosystems [12].
Given these challenges, there is an urgent need to assess the patterns of exploitation and the demographic drivers of trade in O. tetraspis populations. This study therefore investigates (i) the demographic characteristics of traders, (ii) the relative abundance of dwarf crocodiles across three key markets, and (iii) the seasonal and size-class variations in market availability. These insights are critical for developing community-led conservation initiatives, designing effective education and outreach programs, and informing policy reforms to reduce pressure on wild populations of Osteolaemus tetraspis in the Niger Delta.
Materials and methods
Description of study locations
Uwa bushmeat market
The Uwa market is a well-known Bushmeat market situated at the hub of Benin City, Edo State. It has a coordinate of 6.3642472 0N 5.6089668 0E. The market is filled with different forms of wildlife such land mollusks, Porcupines, Pangolins, antelopes, among others.
Edumanom bushmeat market
The Edumanom bushmeat market is situated close to Edumanom forest reserve which is a few kilometers away from Okoroba in Ogbia axis located between Nembe and Brass Local Government Areas of Bayelsa State [2]. The market area has a coordinate of 4.41500°N and 6.45028°E.
Ogbe-Ijaw bushmeat market
The Ogbe-Ijaw is a town located near the city of Warri, Delta State. It has a coordinate of 5.602691 0N and 5.458779 0E. Alagoa, [4]. The coordinate map of the study locations is shown in Fig. 1.
Fig. 1.
Map of Niger-Delta showing the Physiography and Location of Uwa, Ogbe-Ijaw and Edumanon Study Communities
Data collection and sampling techniques
Permission to conduct the research was obtained from community leaders responsible for the market areas. Within each market, bushmeat sellers were located and sellers who handled crocodiles were identified. Thirty (30) sellers in each market were randomly approached for socio-demographic interviews. The sellers comprise of Edo, Isoko/Urhobo, Ijaws and other languages within the Niger Delta. For the abundance analysis, each monitored seller stall constituted the observational unit and each seller was assigned a unique identifier nested within market. All 90 interviewed sellers from the three markets (30 seller per market) were included in the longitudinal monitoring of O. tetrapis. Stock of O. tetrapis were identified, counted and ink-marked to prevent double counting. Market surveys were conducted at fortnightly intervals between October 2021 and April 2022. At each visit, the number of O. tetraspis displayed at each monitored seller’s stall was recorded independently. The fortnightly counts for each seller were aggregated within each month to obtain a monthly seller-level count, which constituted the response variable for subsequent statistical analyses. The final analytical dataset contained 90 unique sellers and 630 seller-month observations. Crocodiles were measured to the nearest 30 cm using a tape measure. This was possible because many of the crocodiles were tied with rope and some were near to death [12]. The selected size categories of 60 cm, 90 cm, and 120 cm for dwarf crocodiles are reasonable and justified given the species’ total length range of 102–180 cm and maximum length of 200 cm as recorded by San Diego [38]. These categories represent different stages of development, with the 60, 90 and 120 ≥ size category corresponding to a young/juvenile, young adult stage, and full-grown adult stages respectively. This is in accordance with methods used by San Diego, [38].
Statistical analysis and model equation
Descriptive statistics were used to summarize trader characteristics, monthly market-recorded counts, and size-class composition across the three markets [22]. Market-level relative abundance was calculated as:
 |
where Nⱼ is the total number recorded in market j and Nₜ is the total number recorded across all markets during the study period.
Monthly relative abundance within market j was calculated as:
 |
where Niⱼ is the number recorded in month i and market j. Size-class composition within each market-month was calculated as:
 |
where Nₕiⱼ is the number recorded in size class h, month i, and market j. These percentages describe the composition of the market records and should not be interpreted as estimates of wild population abundance.
Model description
Monthly records of Osteolaemus tetraspis obtained from individual sellers across the three bushmeat markets were analysed using a negative-binomial generalized linear mixed model (GLMM) to evaluate spatio-temporal variation in market abundance. The negative-binomial distribution was selected because preliminary analyses indicated overdispersion in the count data, making it more appropriate than a Poisson model.
Month and Market Location were included as fixed effects to assess temporal and spatial variation in abundance, while their interaction (Month × Market Location) was included to determine whether seasonal patterns differed among markets. Seller Identity was incorporated as a random intercept to account for repeated observations and unexplained heterogeneity among traders sampled within markets.
Market Location was treated as a fixed effect because only three markets were investigated and the objective was to compare these specific markets rather than infer variation from a larger population of markets. Statistical significance of fixed effects was evaluated using likelihood-ratio tests (χ² tests) based on nested model comparisons. The marginal coefficient of determination (R²m) was calculated to quantify the proportion of variance explained by the fixed effects. Although the GLMM was fitted to seller-level observations, the values presented represent monthly counts aggregated across all sellers within each market for descriptive purposes.
Model equation
Let Yijk denote the number of O. tetraspis recorded by seller k in market j during monthi. i = sampling month (October 2021–April 2022); j = market location (Uwa, Edumanon, Ogbe-Ijaw) and
k = seller within each market.
 |
where:
Yijk = observed count
μijk = expected mean abundance
θ = dispersion parameter
 |
where:
β0 = intercept
β1 = Month effect
β2 = Market effect
β3 = Month × Market interaction
bk = seller-specific random intercept
bk ~ N(0, σ²Seller)
where σ²Seller represents unexplained variation among sellers.
All analyses were conducted in R version 4.5.0 using the glmmTMB package [6, 7, 27, 31].
Results
Some of the dwarf crocodiles displayed for sales at Uwa bushmeat Market are shown in Fig. 2 while that of Ogbe-Ijaw Bushmeat Market was housed in cave in captivity where buyers are allowed to access them as shown in Fig. 2.
Fig. 2.
Crocodile at the cave in Ogbe-Ijaw market
Socio-demographic status of O. tetraspis traders in Niger-Delta bushmeat markets
The socio-demographic profile of O. tetraspis traders across Uwa, Edumanom, and Ogbe-Ijaw bushmeat markets in the Niger Delta regions are presented in Fig. 3a-d. The study revealedthat trading in O. tetraspis is highly gendered, age-structured, and shaped by cultural andeducational backgrounds. Across all three markets, trading was exclusively female-dominated. Allrespondents (100%) from Uwa (n = 30), Edumanom (n = 30), and Ogbe-Ijaw (n = 30) were women,with no male participation reported.
Fig. 3.
Age distribution of O. tetraspis traders across markets
The majority of traders were in the 30–50 years age bracket, indicating that middle-aged women constitute the core of this trade. At Uwa, 40.0% of respondents were aged 30–40 years, 33.3% were 40–50 years, and 26.7% were above 50 years. In Edumanom, 50.0% were 30–40 years, 30.0% were 40–50 years, and 20.0% were over 50 years. At Ogbe-Ijaw, half of the respondents (50.0%) were 40–50 years, while 40.0% were 30–40 years, and only 10.0% were above 50 years (Fig. 3a).
Marital status varied across the study sites. Married women with children constituted the largest proportion of traders: 60.0% in Uwa, 53.3% in Edumanom, and 46.7% in Ogbe-Ijaw. Single parents were also well represented, accounting for 20.0% in Uwa, 33.3% in Edumanom, and 40.0% in Ogbe-Ijaw. Widows made up 20.0% in Uwa, 6.7% in Edumanom, and 13.3% in Ogbe-Ijaw. Notably, a small fraction of unmarried traders (6.7%) was recorded only in Edumanom (Fig. 4b).
Fig. 4.
Marital status of O. tetraspis traders across markets
Educational background differed significantly among markets. In Uwa, 50.0% of traders had only primary education, 27.8% had secondary, and 22.2% tertiary education. In Edumanom, half of respondents (50.0%) had secondary education, while 33.3% had primary and 16.7% tertiary education. In contrast, the Ogbe-Ijaw market was dominated by respondents with lower educational levels: 77.7% had only primary school education, while just 11.1% each had secondary or tertiary education (Fig. 5c).
Fig. 5.
Educational attainment of O. tetraspis traders across markets
Ethnic affiliation of traders showed marked variation across markets. At Uwa, Edo women dominated (60.0%), followed by Urhobo/Isoko (24.0%) and others (16.0%). At Edumanom, Ijaw traders were most numerous (68.0%), followed by Urhobo/Isoko (28.0%) and Edo (absent). In Ogbe-Ijaw, Urhobo/Isoko traders comprised nearly half (48.0%), followed by Ijaw (40.0%) and Edo (12.0%) (Fig. 6d).
Fig. 6.
Ethnic composition of O. tetraspis traders across markets
Relative percentage abundance of crocodile sizes across the three markets
Size-class analysis revealed that medium-sized and large-sized O. tetraspis dominated the market trade, each accounting for 39.24% of the total individuals recorded, whereas small-sized individuals contributed only 21.52% of the total harvest (Table 1). Uwa market recorded its highest abundance among MSDC and LSDC, contributing 38 medium-sized individuals (39.58%) and 36 large-sized individuals (37.50%) of its total market records. In Edumanon, large-sized individuals constituted the highest proportion of captures (47.50%), followed by medium-sized (40.00%) and small-sized crocodiles (12.50%). Similarly, medium-sized individuals were most abundant in Ogbe-Ijaw (36.36%), while small-sized and large-sized individuals each accounted for 31.82% of the records.
Table 1.
Monthly and size variation in the relative abundance of O. tetraspis in bushmeat markets during the study period (October 2021- April 2022)
| Months | Market locations | Total No. of occurrence (% Abundance) | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Uwa (%) | Edumanon (%) | Ogbe-Ijaw (%) | ||||||||
| SSDC | MSDC | LSDC | SSDC | MSDC | LSDC | SSDC | MSDC | LSDC | ||
| October | 5(20.00) | 8(32.00) | 12(48.00) | 2(20.00) | 4(40.00) | 4(40.00) | 1(25.00) | 2(50.00) | 1(25.00) | 39(24.68) |
| November | 2(20.00) | 5(50.00) | 3(30.00) | 0(0.00) | 0(0.00) | 0(0.00) | 1(20.00) | 2(40.00) | 2(40.00) | 15(9.49) |
| December | 4(25.00) | 7(43.75) | 5(31.25) | 0(0.00) | 2(40.00) | 3(60.00) | 1(33.33) | 1(33.33) | 1(33.33) | 24(15.19) |
| January | 3(20.00) | 7(46.67) | 5(33.33) | 0(0.00) | 0(0.00) | 0(0.00) | 0(0.00) | 0(0.00) | 0(0.00) | 15(9.49) |
| February | 2(13.33) | 6(40.00) | 7(46.67) | 1(10.00) | 4(40.00) | 5(50.00) | 2(40.00) | 2(40.00) | 1(20.00) | 30(18.99) |
| March | 6(40.00) | 5(33.33) | 4(26.67) | 2(20.00) | 4(40.00) | 4(40.00) | 1(33.33) | 1(33.33) | 1(33.33) | 28(17.72) |
| April | 0(0.00) | 0(0.00) | 0(0.00) | 0(0.00) | 2(40.00) | 3(60.00) | 1(50.00) | 0(0.00) | 1(50.00) | 7(4.43) |
| Total | 22(22.92) | 38(39.58) | 36(37.50) | 5(12.50) | 16(40.00) | 19(47.50) | 7(31.82) | 8(36.36) | 7(31.82) | 158(100.00) |
Legend: SSDC = Small Sized Dwarf Crocodiles; MSDC = Medium Sized Dwarf Crocodiles; LSDC= Large Sized Dwarf Crocodiles
The monthly and size-class distribution of O. tetraspis across Uwa, Edumanon, and Ogbe-Ijaw bushmeat markets from October 2021 to April 2022 is presented in Table 1. A total of 158 individuals were recorded during the study period, with Uwa accounting for 96 specimens (60.76%), Edumanon 40 specimens (25.32%), and Ogbe-Ijaw 22 specimens (13.92%). Relative abundance varied across months, with peaks in October (24.68%) and February (18.99%), and marked declines in April (4.43%).
Monthly and market variation in the relative abundance ofO. tetraspis
A total of 158 individuals of O. tetraspis were recorded across the three bushmeat markets during the study period (October 2021–April 2022) (Table 2). The Uwa market accounted for the majority of occurrences (60.76%), followed by Edumanon (25.32%) and Ogbe-Ijaw (13.92%). Temporal patterns revealed that abundance peaked in October (24.68%) and February (18.99%), while April recorded the lowest value (4.43%). Uwa exhibited relatively consistent monthly occurrences, whereas Edumanon showed intermittent records with absence in November and January, but higher abundance of 25.00% in February, March and October respectively. Ogbe-Ijaw had the lowest and most irregular records, never exceeding five individuals per month (Table 2).
Table 2.
Monthly and market variation in the relative abundance of O. tetraspis in bushmeat market during the study period (October 2021- April 2022)
| Months | Study locations (Markets) | Total No. of occurrence (% Abundance) | ||
|---|---|---|---|---|
| Uwa | Edumanon | Ogbe-Ijaw | ||
| October | 25(26.04) | 10(25.00) | 4(18.18) | 39(24.68) |
| November | 10(10.42) | 0(0.00) | 5(22.73) | 15(9.49) |
| December | 16(16.67) | 5(12.50) | 3(13.64) | 24(15.19) |
| January | 15(15.63) | 0(0.00) | 0(0.00) | 15(9.49) |
| February | 15(15.63) | 10(25.00) | 5(22.73) | 30(18.99) |
| March | 15(15.63) | 10(25.00) | 3(13.64) | 28(17.72) |
| April | 0(0.00) | 5(12.50) | 2(9.09) | 7(4.43) |
| Total | 96(60.76) | 40(25.32) | 22(13.92) | 158(100.00) |
Note: Data presented in parathesis are relative abundance of O. tetraspis
Model-derived spatio-temporal patterns in osteolaemus tetraspis abundance
The negative-binomial GLMM was fitted to 630 seller-month observations from 90 unique sellers. Month and market location were included as fixed effects together with their interaction, while seller identity was incorporated as a random intercept to account for heterogeneity among traders within markets. The model revealed significant effects of Month (χ²₆ = 19.82, p < 0.01) and Market Location (χ²₂ = 10.46, p = 0.005), as well as a significant Month × Market interaction (χ²₁₂ = 23.17, p = 0.018), indicating that seasonal variation in abundance differed among markets. The marginal coefficient of determination (R²m = 0.48) indicated that fixed effects contributed substantially to variation in monthly abundance. These findings demonstrate significant spatio-temporal heterogeneity in market abundance of O. tetraspis across the Niger Delta.
Discussion
The trade in Osteolaemus tetraspis was exclusively dominated by women, with 100% of respondents across all three markets being female. This mirrors wider observations across West and Central Africa, where women typically control the retail segment of the bushmeat supply chain, while men are more engaged in hunting and transport [1, 30]. This gendered division of labor underscores the central role of women in sustaining household economies through wildlife commerce. However, it also highlights a conservation dilemma: restrictive interventions targeting bushmeat markets may disproportionately affect women, who often already occupy vulnerable socio-economic positions [13].
Age distribution revealed that most traders were middle-aged (30–50 years), with relatively few above 50 and none below 30. This suggests that bushmeat trading is sustained by economically active women in their productive years. The absence of younger traders may indicate generational shifts away from traditional wildlife-based livelihoods, possibly influenced by urban migration and alternative opportunities [36].
Marital status further illustrates the socio-economic dependence on bushmeat commerce. Married women with children constituted the largest group, while single parents and widows also represented significant proportions. This demonstrates that the trade serves as a safety net for vulnerable households, especially female-headed families lacking other income sources [32, 34].
Educational attainment was generally low, with most traders possessing only primary education. Secondary education was more common in Edumanom, while tertiary education was rare. Limited formal education restricts access to alternative livelihoods, reinforcing reliance on the bushmeat trade [20]. It also poses challenges for conservation outreach, which must therefore adopt culturally sensitive and low-literacy communication strategies such as oral campaigns, radio, and local theater [29].
Ethnicity shaped market participation. Uwa was dominated by Edo traders, Edumanom by Ijaw, and Ogbe-Ijaw by Urhobo/Isoko, reflecting the cultural geography of the Niger Delta. Such ethnic structuring influences supply chains and market access, highlighting the need for conservation interventions that are attentive to cultural identities and local leadership [1, 14].
The monthly variation in O. tetraspis abundance suggests strong seasonal influences. Higher records in October and February likely coincide with post-rainfall accessibility to wetlands and riverine habitats, where crocodiles are more vulnerable to hunting [30]. The decline in April may reflect reduced hunting effort due to competing livelihood activities, or seasonal depletion of stocks or environmental pollution [23]. The marked seasonal fluctuation in crocodile abundance suggests that hunting and trade are tightly coupled with ecological and socio-economic rhythms possibly resource availability, hunting accessibility, and cultural norms. The overrepresentation of medium and large size-classes signals selective harvesting pressure that may compromise population structure and reproduction if unchecked. Given the conservation status of O. tetraspis (Vulnerable, CITES I), these patterns underscore the urgency for seasonally informed and size-specific regulation to mitigate unsustainable exploitation. This aligns with regional conservation recommendations for crocodilian management in West and Central Africa. Abundance Patterns at Edumanon showed a significant difference in monthly abundance. October, December, February, March, and April recorded higher abundance, while November and January showed complete absence of individuals. Such fluctuations likely reflect seasonal ecological cycles, including rainfall patterns, flooding, and river water levels, which influence the accessibility of crocodiles to hunters [29]. Moreover, seasonal variations in bushmeat hunting activities have been linked to agricultural calendars and local socio-economic drivers [20]. The absence of O. tetraspis in some months may also be tied to reproductive cycles, as hunters may avoid or be restricted from harvesting nesting females during sensitive breeding periods [18]. Overall, the data suggest that O. tetraspis availability in markets is shaped by seasonal hunting pressure, with higher occurrences during the dry season months (October–February) when crocodiles are more accessible in shrinking aquatic habitats, and markedly reduced supply towards the onset of the rainy season (April). This pattern is consistent with the hydrological regime of the Niger Delta, where lower water levels during the dry season may increase crocodile vulnerability to hunting and improve access to wetland habitats. In contrast, flooding during the onset of the rainy season may reduce hunting success by dispersing individuals across a larger area (Luiselli et al., 2021; Eaton et al., 2023). Market-specific variation further indicates differences in sourcing intensity and trade dynamics among the three locations.
Size-class composition was strongly skewed towards medium- and large-sized individuals, which together accounted for 78.48% of all Osteolaemus tetraspis recorded, while small-sized individuals constituted only 21.52% of the total harvest. Specifically, medium-sized dwarf crocodiles (MSDC) and large-sized dwarf crocodiles (LSDC) each represented 39.24% of the total individuals recorded, indicating a clear dominance of larger size classes in the bushmeat trade across the three markets. Such a pattern suggests selective harvesting of larger crocodiles, likely driven by their greater meat yield and higher market value (Mboh et al., 2020; [28]). However, this exploitation disproportionately targets reproductively mature individuals, which can severely impair population recruitment, population resilience, and long-term breeding potential [18, 39]. The relatively low representation of small-sized individuals (21.52%) may reflect lower hunting preference for juveniles, deliberate avoidance due to lower economic returns, reduced recruitment into the exploited population, localized overharvesting, or differential detectability within the trade network [5]. Collectively, these findings suggest that harvesting pressure is concentrated on medium- and large-bodied crocodiles, a trend that may ultimately lead to population structure imbalances and compromise the sustainability of wild O. tetraspis populations coupled with gas flaring if left unmanaged [23].
Spatial variation also reflected market-specific dynamics. Uwa recorded the highest occurrences, confirming its role as a major bushmeat hub, while Edumanom and Ogbe-Ijaw showed lower but more size-selective patterns. This may indicate localized depletion of smaller size classes or differences in consumer preferences. Importantly, the absence of crocodile supply in some months, particularly in Edumanom, could signify local population declines rather than seasonal absence. The observed variation likely reflects differences in harvest intensity, habitat connectivity, and market accessibility across sites [12].
Promotion of regulated crocodile farming presents a viable alternative that could reduce hunting pressure on wild populations while providing communities with income and meat/skin products. Evidence from other African regions demonstrates that community-based farming, when supported by training, market access, and appropriate legal frameworks, effectively integrates conservation with sustainable development [19]. For example, regulated crocodile ranching and farming programs in Zimbabwe, Zambia, and South Africa have successfully combined biodiversity conservation with rural economic incentives [8, 40]. Incorporating conservation-informed, community-based economic options, particularly targeting hunters could lessen dependence on the crocodilian trade. Additionally, insights from bushmeat studies in Ibadan emphasize the importance of empowering women traders, who dominate specific aspects of the trade, with sustainable alternatives to balance ecological and social justice [1, 14].
Conservation implications
The spatiotemporal dynamics revealed by the model have clear implications for the conservation and sustainable management of O. tetraspis. Given the species’ Vulnerable status on the IUCN Red List, with overexploitation and habitat loss identified as principal threats (IUCN [24], [25]), these findings underscore the need for adaptive, evidence-based management. Continued removal of large adults during critical aggregation periods may exacerbate local declines, particularly considering the species’ low fecundity, cryptic behaviour, and reliance on forested wetlands for nesting ([39]; Luiselli et al., 2021). Integrating geospatial monitoring, community-based reporting, and market surveillance could inform sustainable harvest frameworks that safeguard populations while maintaining local livelihoods.
The socio-demographic composition of traders further highlights the need to embed social equity within conservation interventions. Women especially single parents and widows with limited formal education are disproportionately reliant on bushmeat commerce for subsistence. Blanket enforcement or trade prohibitions without viable economic alternatives risk exacerbating poverty and undermining compliance [32]. Hence, effective conservation should adopt participatory, livelihood-sensitive approaches that harmonise species protection with socio-economic resilience. Such integrative strategies align with regional recommendations for crocodilian conservation and sustainable use across West and Central Africa [9], providing a robust, quantitative basis for the long-term persistence of O. tetraspis within the Niger Delta. However, conservation efforts should pursue:
-
i.
Alternative livelihoods: Fish farming, small-scale agriculture, and micro-credit initiatives targeted at women traders.
-
ii.
Culturally sensitive awareness programs: Oral, visual, and community-based approaches tailored to low-literacy audiences.
-
iii.
Ethnic engagement: Collaboration with community and ethnic leaders to ensure legitimacy and compliance.
-
iv.
Market-specific interventions: Policies tailored to the distinct socio-demographic and ecological dynamics of each market rather than uniform approaches.
-
v.
Temporal and spatial protections: Limiting hunting during dry-season peaks and prioritizing high-pressure markets such as Uwa for monitoring and enforcement.
Recommendations for sustainable management
Based on the findings of this research, the following are therefore recommended:
-
i.
Temporal Harvest Regulation: Limiting hunting during mid-dry season peaks (e.g., October–February) could reduce pressure during critical moisture-related aggregation periods.
-
ii.
Spatial Monitoring: Geographic targeting of conservation efforts around Uwa and Edumanon would help address high-intensity supply zones.
-
iii.
Alternative Livelihood: Promotion of regulated crocodile farming could reduce hunting pressure on wild populations while providing communities with income and meat/skin products. Community-based farming, when supported by training, market access, and appropriate legal frameworks, effectively integrates conservation with sustainable development.
-
iv.
Behavioral Surveillance: Monitoring the timing of reproductive nesting (May–June) affords opportunities for protecting nesting sites and allowing recruitment.
-
v.
Awareness and Enforcement: Strengthened law enforcement in collaboration with communities particularly given that some hunting techniques (e.g., snares and shooting) vary regionally and seasonally can help deter unsustainable capture.
Limitations and future directions
This study relied primarily on market-based monitoring, and thus harvest rates could not be directly linked to wild population resilience. Future research should integrate systematic field surveys with market assessments to estimate sustainable offtake thresholds. Moreover, investigations into consumer demand cycles, price fluctuations, and cultural drivers would further enrich conservation planning.
Conclusion
The trade in O. tetraspis across Uwa, Edumanom, and Ogbe-Ijaw markets reflects a highly gendered, middle-aged, and ethnically structured economy that sustains vulnerable households but exerts unsustainable pressure on a threatened species. The predominance of medium- and large-bodied crocodiles in the trade underscores the risk of reproductive collapse under continued exploitation. Effective conservation will require a multi-pronged approach—balancing ecological protection with social equity, through alternative livelihoods, culturally adapted education, and market-specific interventions. The study demonstrates that O. tetraspis abundance in bushmeat markets is significantly influenced by both temporal availability and size-class selectivity. These results align with broader evidence of unsustainable exploitation of African crocodile populations and underscore the necessity of targeted conservation strategies.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
We are grateful to the Departments of Animal and Environmental Biology of the University of Port Harcourt, Choba Rivers State, Nigeria, for providing the field and laboratory materials for this research work. More so, we appreciate the bushmeat Market traders for giving us audience for observation of the dwarf crocodiles species and answering specific questions pose to them.
Author contributions
A…….Data Collection, Research Writing. Ogorode, I.OB…….Computing, Conceptualization, Statistical Analysis E.E. ItoC……… Conceptualization, Corrections. Oriakpono, O.ED ……… Conceptualization, Corrections. Vincent-Akpu Ijeoma E………. Conceptualization. Babatunde Bolaji F……….Funding of field work. Francis.
Funding
The authors do hereby declare that no external funding from any organization was used in the process of the research.
Data availability
No datasets were generated or analysed during the current study.
Declarations
Ethical approval
This study and field work was approved (Institution not applicable) by the Elder of Chief Council in charge of Uwa, Edumanom and Ogbe-Ijaw Bushmeat Market in various locations as no formal document was officially given. Informed consent was obtained from all participants. Permission were taken from the market women before they were interviewed while taking the records of the crocodile sighted and market survey. The ethics declaration was conducted in accordance with the Declaration of Helsinki.
Author declaration
All authors declared that the field work was carried out, Conceptualization, writing, funding were done and laboratory consent were taken from the department of Animal and Environmental Biology, University of Port Harcourt, Choba Rivers State, Nigeria.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Israel O. Ogorode, Email: israelogorode@gmail.com, Email: Israel.ogorode@uat.edu.ng
Edore E. Ito, Email: eeito@delsu.edu.ng
References
- 1.Akani GC, Petrozzi F, Ebere N, Dendi D, Luiselli L. Correlates of bushmeat trade in the Niger Delta, Nigeria. Afr J Ecol. 2015;53(2):240–8. [Google Scholar]
- 2.Akani GC, Aifesehi PEE, Petrozzi F, Amadi N, & Luiselli L. Preliminary surveys of the terrestrial vertebrate fauna (mammals, reptiles, and amphibians) of the Edumanon Forest Reserve, Nigeria. Tropical Zoology. 2014;27(3):63–72. 10.1080/03946975.2014.944376.
- 3.Akani GC, Eniang EA, Luiselli L. Bushmeat consumption among urban and rural communities in Nigeria: Patterns and implications for reptile conservation. Herpetological Conserv Biology. 2019;14(3):567–78. [Google Scholar]
- 4.Alagoa EJ. A history of the Niger Delta: an historical interpretation of Ijo oral tradition. Port Harcourt (NG): Onyoma Research Publications; 2005. ISBN: 978-37314-5-9.
- 5.Amadi N, Ogbonna J, Uka J. Bushmeat exploitation and sustainability challenges in West Africa. Biodivers Conserv. 2022;31(7):1883–901. 10.1007/s10531-022-02389-5. [Google Scholar]
- 6.Bates D, Mächler M, Bolker B, Walker S. Fitting linear mixed-effects models using lme4. J Stat Softw. 2015;67(1):1–48. 10.18637/jss.v067.i01. [Google Scholar]
- 7.Brooks ME, Kristensen K, van Benthem KJ, Magnusson A, Berg CW, Nielsen A, Skaug HJ, Mächler M, Bolker BM. glmmTMB balances speed and flexibility among packages for zero-inflated generalized linear mixed modeling. R J. 2017;9(2):378–400. 10.32614/RJ-2017-066. [Google Scholar]
- 8.Chihona S. (2014). The impact of Nile crocodile (Crocodylus niloticus) on the communal livelihoods: a case study of areas surrounding Ruti Dam in Gutu and Buhera districts in Zimbabwe (Master’s thesis). University of South Africa, Pretoria, South Africa. http://hdl.handle.net/10500/18582.
- 9.Eaton MJ, Martin A, Thorbjarnarson J, Amato G. Species-level diversification of African dwarf crocodiles (Genus Osteolaemus): A geographic and phylogenetic perspective. Mol Phylogenet Evol. 2009;50(3):496–506. 10.1016/j.ympev.2008.11.009. [DOI] [PubMed] [Google Scholar]
- 10.Eaton MJ. Systematics, population structure and demography of the African dwarf crocodile (Osteolaemus spp.): a perspective from multiple scales [dissertation]. Boulder (CO): University of Colorado; 2009.
- 11.Eaton MJ. Ecology, conservation and management of the Central African dwarf crocodile (Osteolaemus tetraspis): a progress report. In: Crocodiles: Proceedings of the 18th Working Meeting of the IUCN-SSC Crocodile Specialist Group. Gland (CH): IUCN; 2006. p. 84-95.
- 12.Eniang A, Godfrey C, Akani D, Dendi J, Lucas L. People’s perception of crocodile in Nigeria. Herpetological J. 2020;30:112–6. [Google Scholar]
- 13.Fa JE, Olivero J, Real R. Bushmeat trade and consumption in West and Central Africa: Drivers, scale, and conservation implications. Biol Conserv. 2022;268:109515. [Google Scholar]
- 14.Fa JE, Olivero J, Real R, Farfán MÁ, Márquez AL, Vargas JM, Nasi R. Disentangling the relative effects of bushmeat availability on human nutrition in Central Africa. Sci Rep. 2019;9:7856. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Franke FA, Schmidt F, Borgwardt C, Bernhard D, Bleidorn C, Engelmann W-E, Schlegel M. Genetic differentiation of the African dwarf crocodile Osteolaemus tetraspis Cope, 1861 (Crocodylia: Crocodylidae) and consequences for European zoos. Organisms Divers Evol. 2013;13(2):255–66. 10.1007/s13127-012-0107-1. S2CID 14636510. [Google Scholar]
- 16.Gvoždík V, Gonwouo LN, Wilkinson M, Kouete MT, Loader SP. Phylogenomics of African dwarf crocodiles (Osteolaemus) reveals cryptic diversity and evolutionary distinctiveness. Sci Rep. 2024;14:5125. 10.1038/s41598-025-08789-3.38429361 [Google Scholar]
- 17.Heather R. Dwarf crocodile (Osteolaemus tetraspis) [Internet]. 2023. https://animaldiversity.org.
- 18.Hekkala E, Shirley MH, Amato G, Austin JD, Charter S, Thorbjarnarson J, Vliet KA, Houck ML, Desalle R, Blum MJ. An ancient icon reveals new mysteries: Comparative phylogeography of African dwarf crocodiles. Mol Ecol. 2020;29(3):491–504. [DOI] [PubMed] [Google Scholar]
- 19.Hughes A, Auliya M, Altherr S, Scheffers B, Janssen J, Nijman V, Shepherd CR, D’Cruze N, Sy E, Edwards DP. Determining the sustainability of legal wildlife trade. J Environ Manage. 2023;341:117987. 10.1016/j.jenvman.2023.117987. [DOI] [PubMed] [Google Scholar]
- 20.Ingram DJ, Coad L, Abernethy KA, Maisels F, Stokes EJ, Bobo KS, Scharlemann JPW. Wild meat is still on the menu: Progress in wild meat research, policy, and practice from 2002 to 2020. Annu Rev Environ Resour. 2021;46:221–54. [Google Scholar]
- 21.Ito EE, Agbure PA, Egwunyenga AO. Soil-Transmitted Helminths Co-Infected with Schistosoma in Flood-Plain Communities, Southern. Nigeria Journal Egypt Soc Parasitology. 2023a;53(3):593–8. [Google Scholar]
- 22.Ito EE, Eze CN, Nduka FO. Geospatial Seasonal Environmental Impacts on the Distribution and Abundance of Schistosoma haematobium Vectors in Two Districts of the Ase River Catchment, Delta State. Nigeria Tropical Freshw Biology. 2023b;32:19–36. [Google Scholar]
- 23.Ito EE, Ugbome IL. Impact of gas flaring on biodiversity in Niger Delta, Nigeria. Nigerian J Sci Environ. 2017;15(1):147–54. [Google Scholar]
- 24.IUCN. Osteolaemus tetraspis. The IUCN Red List of Threatened Species 2022. https://www.iucnredlist.org/.
- 25.IUCN. Osteolaemus tetraspis. The IUCN Red List of Threatened Species 2024. https://www.iucnredlist.org.
- 26.Kofron CP, Steiner T. Observations on the African dwarf crocodile (Osteolaemus tetraspis). Copeia. 1994;1994(2):533–5. 10.2307/1447004. [Google Scholar]
- 27.Lenth RV. Emmeans: estimated marginal means, aka least-squares means 2024. (R package version 1.10). https://cran.r-project.org/web/packages/emmeans/index.html.
- 28.Luiselli L, Akani GC. Crocodile population ecology and conservation in sub-Saharan Africa: Insights from long-term studies. Herpetological Conserv Biology. 2019;14(2):281–94. [Google Scholar]
- 29.Luiselli L, Akani GC, Petrozzi F, Pacini N. Socioeconomic drivers of the bushmeat trade in sub-Saharan Africa. People Nat. 2023;5(1):120–34. [Google Scholar]
- 30.Luiselli L, Hema EM, Segniagbeto GH, Ouattara V, Eniang EA, Vittorio MD, Amadi N, Parfait G, Pacini N, Akani GC, Sirima D, Guenda W, Fakae BB, Dendi D, Fa JE. Understanding the influence of non-wealth factors in determining bushmeat consumption: Results from four West African countries. Acta Oecol. 2019;94:47–56. [Google Scholar]
- 31.Nakagawa S, Schielzeth H. A general and simple method for obtaining R² from generalized linear mixed-effects models. Methods Ecol Evol. 2013;4(2):133–42. 10.1111/j.2041-210X.2012.00261.x. [Google Scholar]
- 32.Nasi R, Taber A, van Vliet N. Empty forests, empty stomachs? Bushmeat and livelihoods in the Congo and beyond. Front Ecol Evol. 2022;10:842559. [Google Scholar]
- 33.Nathaniel I, Nathaniel A. The effects of poverty in conservation of biodiversity: the Nigeria experience [Internet]. 2010.
- 34.Njiforti HL, Tchamba MN. The bushmeat trade in northern Cameroon. J Ethnobiol. 1999;19(1):27–44. [Google Scholar]
- 35.Ogorode IO, Vincent-Akpu IF, Babatunde BB, Ijeoma MH, Ogbeibu EA, Olaleru F. Illegal wildlife trade and Osteolaemus tetraspis: a case study of activities in bushmeat markets (Uwa and Edumanom) in Niger Delta, Nigeria. Int J Eng Sci. 2023;6(4):1–10.
- 36.Okello MM, Kiringe JW, Warinwa F. Conservation and livelihood implications of the bushmeat trade in African savannah ecosystems. Biodivers Conserv. 2017;26(2):451–71. [Google Scholar]
- 37.Rio JP, Mannion PD. Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem. Peer J. 2021;9:e12094. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.San Diego Zoo Wildlife Alliance. Dwarf crocodile (Osteolaemus tetraspis) fact sheet [Internet]. San Diego (CA): San Diego Zoo Wildlife Alliance; c2015 [cited 2025 Aug 21]. http://ielc.libguides.com/sdzg/factsheets/dwarf_crocodile.
- 39.Shirley MH, Villanova VL, Vliet KA, Austin JD. Genetic barcoding facilitates captive and wild management of three cryptic African crocodile species complexes. Anim Conserv. 2015;18(4):322–30. 10.1111/acv.12176. S2CID 82155811. [Google Scholar]
- 40.Utete B. A review of the conservation status of the Nile crocodile (Crocodylus niloticus Laurenti, 1768) in aquatic systems of Zimbabwe. Global Ecol Conserv. 2021;29:e01743. [Google Scholar]
- 41.Villiers A. Tortues et crocodiles de l’Afrique noire française. Initiations Africaines. Vol. 15. Dakar (SN): Institut Français d’Afrique Noire; 1958. p. 1-354.
- 42.Webb GJW, Britton ARC, Manolis SC, Ottley B. a. Decline and recovery of crocodile populations: Lessons learned from the management of crocodilians in Australia. Wildl Res. 2010;37(5):357–65. [Google Scholar]
- 43.Webb GJW, Manolis SC, Brien ML. Saltwater crocodile Crocodylus porosus. In S. C. Manolis & C. Stevenson (Eds.), Crocodiles: Status survey and conservation action plan (3rd ed., pp. 99–113). Darwin, Australia: Crocodile Specialist Group. 2010.
- 44.Webb G, Manolis SC. Crocodiles of Australia. Sydney, Australia: Reed Books Pty. Ltd. 1989. ISBN 6-7301-0254-8.
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Supplementary Materials
Data Availability Statement
No datasets were generated or analysed during the current study.