Primates in Peril

Ambatotsirongorongo Mountains and the forestless
plain. Most of this forest has disappeared and only small
fragments remain on the southern flanks of the three
main summits. Their floristic composition has been
characterized as a predominantly humid, transitional
mixture (Andrianarimisa et al. 2009; Ramanamanjato
et al. 2002).
Until recently, three of these forest fragments were the
only known habitat of Cheirogaleus lavasoensis (Thiele
et al. 2013). The three forest fragments had sizes of 50 ha,
30 ha, and 25 ha in 2009 (Andrianarimisa et al. 2009).
Extensive fieldwork in nearby transitional, humid, and
littoral forest yielded no evidence for the occurrence
of the species (Hapke et al. 2005; Hapke, Gligor, and
Andrianjaka pers. obs). Lei et al. (2014) reported the
occurrence of Cheirogaleus lavasoensis at Kalambatritra,
170 km north of the Lavasoa-Ambatotsirongorongo
Mountains at an altitude of approximately 1200 m.
The Kalambatritra forest is Madagascar’s westernmost
rainforest and situated on the islands west-eastern
drainage divide in an elevation range of 1200-1680 m
(Irwin et al. 2001). It is separated from the eastern humid
forest by 16 km of open grassland and extends over an
area with a north-southern diameter of approximately
60 km.
Thiele et al. (2013) reported data from 17 individuals
of Cheirogaleus lavasoensis that had been captured
and released between 2001 and 2006. The habitat of
the species in the Lavasoa-Ambatotsirongorongo
Mountains is biogeographically isolated, small,
and fragmented. A survey in 2015 confirmed the
persistence of Cheirogaleus lavasoensis in this area but
also a further decline of forest cover (Andrianjaka and
Hapke unpublished). The forest of Kalambatritra could
potentially harbor a considerably greater population of
Cheirogaleus lavasoensis. At present, it is not possible
to estimate its size because Lei et al. (2014) report
data from a single individual that they could assign to
the species. With respect to the differences in latitude
and elevation, it is probable that there are strong
ecological differences between Kalambatritra and the
Lavasoa-Ambatotsirongorongo Mountains. Further
research is necessary to gather information about the
population size at Kalambatritra and about possible
local adaptations of Cheirogaleus lavasoensis in the
two areas. The population at Ambatotsirongorongo
thus deserves high conservation priority, at least until
more data become available about the population at
Kalambatritra.
The entire remaining forest in the Lavasoa-
Ambatotsirongorongo Mountains is situated within
the Nouvelle Aire Protégée Ambatotsirongorongo.
The greatest threats for the survival of Cheirogaleus
lavasoensis in this area are further habitat loss and
degradation. The main pressures are wood extraction,
slash and burn cultivation, and accidental fires, which
are frequent due to the practice of regular grassland
burning. The forest fragments inhabited by Cheirogaleus
lavasoensis are apparently remnants of the most humid
patches within a formerly larger, continuous forest.
Until recently, the local population relied on dryer
forest remnants as main sources of construction timber
and firewood. These fragments have now mostly
disappeared, which generates the risk of increasing
pressure onto the remaining habitat of Cheirogaleus
lavasoensis. At least two forest fragments inhabited by
Cheirogaleus lavasoensis harbor sources that are used by
the local population for paddy irrigation and drinking
water supply. A successful conservation program
should thus integrate water management, reforestation
and habitat restoration.
References
Andrianarimisa, A., V. Andrianjakarivelo, Z.
Rakotomalala, Z. and M. Anjeriniaina 2009. Vertébrés
terrestres des fragments forestiers de la Montagne
d’Ambatotsirongorongo, site dans le Système des Aires
Protégées de Madagascar de la Région Anosy, Tolagnaro.
Malagasy Nature 2: 30-51.
Foiben-Taosarintanin’i Madagasikara. 1979. Ranopiso,
Feuille M-62, Carte Topographique au 100000. Institut
National de Géodésie et Cartographie, Antananarivo,
Madagascar.
Groeneveld, L.F., D. W. Weisrock, R. M. Rasoloarison, A.
D. Yoder and P.M. Kappeler. 2009. Species delimitations
in lemurs: multiple genetic loci reveal low levels of
species diversity in the genus Cheirogaleus. BMC
Evolutionary Biology 9: 30.
Groeneveld, L.F., M. B. Blanco, J. L. Raharison, V.
Rahalinarivo, R. M. Rasoloarison, P. M. Kappeler,
P.M., L. R. Godfrey and M.T. Irwin. 2010. MtDNA and
nDNA corroborate existence of sympatric dwarf lemur
species at Tsinjoarivo, eastern Madagascar. Molecular
Phylogenetics and Evolution 55: 833-845.
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