Abstract
West African dwarf crocodiles (Osteolaemus sp. nov. cf. tetraspis) are among the most threatened crocodilians in the world due to unregulated hunting and habitat loss-related population decline. Despite this, many questions about their basic ecology remain unanswered and this inadequate data hampers effective dwarf crocodile management. We describe incubation temperature, nesting success, hatching rate, and clutch size of West African dwarf crocodiles. We monitored 18 nests from the 2017 and 2018 nesting seasons in the Chirehin Community Land—a highly disturbed agricultural matrix in the climatic transition zone of Ghana. We used Hobo tidbit® data loggers to monitor egg chamber temperature and the effect of ambient temperature on nest temperature. The daily mean incubation temperature recorded during the study was 30.7°C (±SD = 0.8°C, n = 240, range = 28–33°C) and it is congruent with the reported value for the species. The findings from this study suggest a weak positive to no correlation between dwarf crocodile incubation temperature and ambient temperature indicating nest temperature is almost independent of ambient temperature. We found a mean clutch size of 8 eggs per nest (SD = ±2; range = 5–13; n = 17) supporting previous reports that this genus has a low clutch size. The mean nesting success and hatching success across the two seasons were 77.8% and 75.3% (SD = ±41.9, n = 18), respectively. Three nests were destroyed by flood and one by an unknown predator suspected to be a West African Nile monitor lizard. Generally, dwarf crocodiles selected forest patches within the highly disturbed landscape for nesting indicating the need to protect the remaining forest patches. Efforts should be made to repeat the study across this species’ range for an improved understanding of its nesting ecology.
Highlights
African dwarf crocodiles are relatively small, secretive, and docile crocodilians that are endemic to western Africa from the Democratic Republic of Congo to e Gambia [1, 2]
An update of the Red List status may be necessary following the taxonomy revision by Eaton et al [8] that recognized three lineages in the genus Osteolaemus, namely, Osteolaemus osborni restricted to the Congo Basin, Osteolaemus tetraspis found in the Lower Guinea bioregion of west Central Africa and yet to be named Osteolaemus sp. nov. cf. tetraspis distributed in the Upper Guinea bioregion of West Africa
3.2. e Relationship between Nest Temperature and Ambient Temperature. e ambient and incubation temperatures of nest 2 and nest 4 were measured concurrently to assess the influence of ambient temperature on West African dwarf crocodile incubation temperatures
Summary
African dwarf crocodiles (genus Osteolaemus) are relatively small, secretive, and docile crocodilians that are endemic to western Africa from the Democratic Republic of Congo to e Gambia [1, 2]. Dwarf crocodiles are categorized as vulnerable on the IUCN Red List [10] and all populations are on Appendix I of the Convention on International Trade in Endangered Species (CITES) checklist [11]. For the International Journal of Ecology past three decades, there have been a handful of studies on the basic ecology of wild populations of dwarf crocodiles in West Africa [3, 6, 7, 9]. Among the key reasons given for this paucity of research are secluded habitats of the species which severely affects field observations, low population densities, the low interest of the skin industry [7], and lack of local expertise in most parts of West Africa. is dearth of knowledge coupled with increasing anthropogenic related threats warrants research on all aspects of dwarf crocodile ecology to aid evidence-based management decisions
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