Nesting Ecology of West African Dwarf Crocodiles in a Heavily Disturbed Landscape in Chirehin, Ghana

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.

Temperature variation in nests of Paleosuchus palpebrosus (Crocodylia: Alligatoridae) near the southern edge of the species´ range, Brazil

“…Temperatures in nests of P. trigonatus in central Amazonia were significantly related to rainfall, but not air temperature (Magnusson et al, 1990). Amoah et al (2021) also found only a weak relationship between nest and air temperatures in Osteolaemus sp. Nov. cf.…”

“…nov. cf. tetraspis, in Africa (Amoah et al, 2021). In captive situations, P. palpebrosus eggs are incubated at a temperature between 28 o C to 32 o C for an incubation period of 96 to 130 days (Medem, 1971(Medem, , 1972Rugeles, 2001).…”

Giant dwarf crocodiles from the Miocene of Kenya and crocodylid faunal dynamics in the late Cenozoic of East Africa

“…The depositional systems at sites preserving Kinyang and Brochuchus all reflect mixed riparian woodlands and mixed open habitats that formed under comparatively dry conditions (Butts et al, 2018; Driese et al, 2016; Liutkus‐Pierce et al, 2019; Lukens et al, 2017; Michel et al, 2020; Retallack et al, 2002). But living dwarf crocodiles are not restricted to closed‐canopy rain forests; they can be found in riparian woodlands and seasonal wetlands (e.g., Eaton, 2010; Ceríaco & de Sá, 2018; Amoah et al, 2021). Thus, the kinds of biomes that dominated Early to Middle Miocene sites preserving generalized osteolaemines might not reflect different ecological preferences from modern Osteolaemus .…”

“…These, in turn, are thought to have led to diminishing woodlands and expansion of C 4 plants (e.g., Feakins et al, 2013; Jacobs et al, 2010; Linder, 2017; Saarinen et al, 2020). This prompted Cossette et al (2020) to suggest that changes in crocodylian faunas might have reflected changes in vegetation; modern African dwarf crocodiles ( Osteolaemus Cope, 1861; Figure 1b) are generally limited to forested wetlands (Amoah et al, 2021; Eaton, 2010; Kofron, 1992; Leaché et al, 2006; Riley & Huchzermeyer, 1999; Smolensky, 2015; Waitkuwait, 1986).…”

The Vulnerable West African Dwarf Crocodile (Osteolaemus Sp. Aff. Tetraspis) is Worth Conserving in Urban Ecosystems: Evidence from Ghana

“…obs. ; Amoah et al 2021). Also, the current studies on crocodiles do not show a clear representation of urban ecosystems which are unique habitats that required targeted research and data for fuelling targeted urban crocodile conservation actions (Gross 2002).…”