Variation in abundance and habitat use of the critically endangered Microcebus gerpi across its fragmented range

Romule Rakotondravony; Dominik Schüßler; Valisoa S T Rovanirina; Jonah Ratsimbazafy; Ute Radespiel

doi:10.1002/ajp.23553

Variation in abundance and habitat use of the critically endangered Microcebus gerpi across its fragmented range

Am J Primatol. 2023 Nov;85(11):e23553. doi: 10.1002/ajp.23553. Epub 2023 Sep 26.

Authors

Romule Rakotondravony^{1

2}, Dominik Schüßler³, Valisoa S T Rovanirina¹, Jonah Ratsimbazafy⁴, Ute Radespiel⁵

Affiliations

¹ Faculté des Sciences, de Technologies et de l'Environnement, University of Mahajanga, Mahajanga, Madagascar.
² Ecole Doctorale Ecosystèmes Naturels (EDEN), University of Mahajanga, Mahajanga, Madagascar.
³ Institute of Biology and Chemistry, University of Hildesheim, Hildesheim, Germany.
⁴ Groupe d'étude et de recherche sur les primates de Madagascar (GERP), Antananarivo, Madagascar.
⁵ Institute of Zoology, University of Veterinary Medicine Hannover Foundation, Hannover, Germany.

PMID: 37750250
DOI: 10.1002/ajp.23553

Abstract

A link between the abundance of species and their degree of ecological specialization has previously been suggested within the primate order. Many species of lemurs were only recently described and even basic ecological data are not yet available for them. We investigated the habitat use, abundance, and habitat characteristics of the critically endangered Microcebus gerpi and evaluated potential impacts of vegetation structure and human disturbances on variations in its abundance. We determined abundance by systematic nocturnal surveys along 13 transects that were also used for characterizing the vegetation structure in seven study sites that were widely distributed within its range. Although M. gerpi occurred in all studied lowland rainforest and littoral forest fragments in central eastern Madagascar and therefore has a higher ecological plasticity and wider distribution than previously thought, its actual Area of Occupancy is very small (339.78 km² ) due to an extreme degree of habitat fragmentation throughout its range. M. gerpi occurred with a mean encounter rate of 3.04 individuals/km but abundance varied substantially between sites (0.75-4.5 individuals/km). Statistical modeling revealed that the cover of small- to medium-sized trees had a positive impact on the abundance of M. gerpi, whereas a composite disturbance score (CDS), formed on the basis of information on the prominence of fires, cattle, charcoal production and wood extraction inside and around the forest, had a negative impact on abundance. These results suggest that M. gerpi is slightly less threatened than expected because of its larger geographic range, but also that it responds negatively to human disturbances. These findings raise strong conservation concerns and question the long-term viability of the remaining small and isolated populations of this arboreal solitary forager.

Keywords: Area of Occupancy; Extent of Occurrence; anthropogenic activity; mouse lemur; vegetation structure.

Abstract

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