Variation in the Demographic Structure of the Viviparous Toad Nimbaphrynoides occidentalis (Anura: Bufonidae) before and after a Fire in the Altimontane Grasslands of the Mount Nimba Integral Nature Reserve, Westen Côte d’Ivoire
Kouassi Philippe KANGA *
Biological Sciences Teaching and Research Unit, Department of Animal Biology, Laboratory of Environment, Climate, Health, Engineering and Sustainable Development, Peleforo Gon Coulibaly University, PO Box 1328 Korhogo, Côte d’Ivoire.
Jean-Christophe Béhibro Yao N’Gatta KONAN
Environmental Training and Research Unit, Laboratory of Biodiversity and Tropical Ecology (BioEcoTrop), Jean Lorougnon Guédé University, BP 150 Daloa, Ivory Coast.
Atta Léonard KOUADIO
Science and Technology Training and Research Unit, Department of Biosciences, Alassane Ouattara University, PO Box 18 Bouaké 01, Côte d’Ivoire.
Kouassi Brahiman KIEN
Biological Sciences Teaching and Research Unit, Department of Animal Biology, Laboratory of Environment, Climate, Health, Engineering and Sustainable Development, Peleforo Gon Coulibaly University, PO Box 1328 Korhogo, Côte d’Ivoire.
*Author to whom correspondence should be addressed.
Abstract
The viviparous western toad (Nimbaphrynoides occidentalis), an endemic and critically endangered species of the Mount Nimba Integral Nature Reserve, is highly dependent on high-altitude grasslands, ecosystems particularly vulnerable to fire. This study assesses the effects of a high-intensity fire on the abundance, spatial distribution, and population structure of the species in two habitat types (grassland and rocky). Standardised surveys were conducted before and after the fire along transects, representing a total effort of 640 person-hours. A total of 9,600 individuals were recorded before the fire, compared with only 2,501 after the event, representing a 74% population decline. Before the fire, the species primarily inhabited grassland habitats (75% of observations) and exhibited a relatively balanced population structure. After the fire, survivors concentrated more heavily in these habitats (91%), while rocky habitats became sparsely occupied. The post-fire population structure was characterised by a strong dominance of juveniles (>80%) and a marked decrease in breeding adults. The results suggest that a severe fire leads to significant mortality, particularly among the most exposed age classes, causing a spatial redistribution of survivors and a pronounced rejuvenation of the population. Grasslands appear to be essential refuge habitats that promote the species' persistence after disturbance. This study highlights the sensitivity of Nimbaphrynoides occidentalis to fire and emphasises the importance of appropriate fire management strategies to ensure the long-term conservation of this unique species in the Mount Nimba Strict Nature Reserve.
Keywords: Biodiversity, conservation, fire disturbance, population dynamics