COS 185-5 - No calm after the storm: Immediate effects of Cyclones Batsirai and Emnati on lemur presence and vegetation structure

Background/Question/Methods

Cyclones are known to pose significant threats to the survival of primate species worldwide. These stochastic weather events can severely affect primates’ survival by damaging habitats and disrupting phenological processes. In February 2022, Cyclones Batsirai and Emnati hit the East coast of Madagascar less than three weeks apart, causing extensive damage to lemur habitats in the area. Batsirai, the strongest of these cyclones, recorded wind speeds of 165km/h and wind gusts of up to 230km/h. In this study, we investigate the immediate impacts of cyclones Batsirai and Emnati on the presence of two lemur species and vegetation structure. We collected data from January to March 2022 in three forest fragments in the Kianajavato commune, Madagascar. To determine the presence of lemur species, we installed camera traps before the cyclones at ten sampling points. Each point contained one arboreal (average height = 10m) and one ground (average height = 30cm) camera. The cameras were installed within a grid with a density of one camera per 0.5km² and ran for 32 days. Vegetation surveys were conducted pre- and post-cyclones using a 20m radius circle-plot centred at the camera points. The canopy cover was estimated using a densiometer.

Results/Conclusions

Following cyclones Batsirai and Emnati, 77.44% of the trees suffered substantial damages (e.g., defoliation, uprooting, trunk splitting and breakage), and there was a 62.16% loss in canopy cover. We observed an increase in ground use by greater bamboo lemurs (Prolemur simus) and red-fronted brown lemurs (Eulemur rufifrons). Pre-cyclone, these species were only recorded by the arboreal cameras (14 independent events). In comparison, post-cyclone E. rufifrons was observed both by ground (1 independent event), and arboreal cameras (14 independent events), while P. simus was only recorded on the ground (8 independent events). The increase in ground use by these species results from 1) the lack of connectivity between trees, hindering the use of branches for travelling, and 2) the lack of food resources in the canopy due to defoliation and defruiting caused by heavy rain and high-speed winds. By spending more time on the ground, lemurs are increasing their chances of predation and disease transmission. Further lemur monitoring in the Kianjavato forests is required to properly assess the long-term impacts of these cyclones on these threatened species.