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As someone who has spent several months over several years looking at mouse lemur faces (and genitalia), at
two eastern rainforest sites (Ranomafana and Tsinjoarivo forests), I felt confident enough to embark on a new chal-
lenge, to capture and identify mouse lemurs from
northeastern Madagascar, specifically at Marojejy
National Park and at Anjanaharibe Sud Special Re-
serve. Truth be told, however, no expert eye can
easily tell rainforest mouse lemur species apart.
Descriptions usually include details such as:
“brownish-reddish dorsal coat, yellowish-creamy
ventral coat, interocular white stripe…body mass
of 40 or 50 g”. There are several problems with
these descriptions: color coat may differ between
juveniles and adults, even among adults in the
same population. Also, some characteristics are
too general and shared among species. Body mass
varies among age/sex groups, but also between
seasons. For instance, adults may put on some ex-
tra weight and store fat in their tails and body prior
to the winter season; moreover, male body masses
differ significantly depending on whether their tes-
tes are developed or not prior to/during the reproductive season (note: testes are regressed most of the year but
can “grow” as large as their brain, for reproductive purposes).
The cryptic morphological nature of mouse lemurs contrasts with their great genetic variability, which makes
them a difficult, yet interesting case for evolutionary studies. The story of mouse lemurs is one of relatively recent
and rapid adaptive radiation. In fact, mouse lemurs (Microcebus) are unique in that they are present in basically all
forest types, including degraded environments and close to villages, where no other lemurs may exist. Yet, geo-
graphic isolation, partly due to recent forest fragmentation and habitat loss, has “precipitated” genetic diversifica-
tion among small populations, many of which are cornered to the brinks of extinction. Thus, whereas as a group
mouse lemurs are almost omnipresent, some of them (species) may be condemned to disappearance soon after
their scientific discovery. Why would we care about species then?
As “evolutionary units”, species perpetuate heritable traits (by virtue of reproductive members passing on those
traits), many of which are a reflection of environmental “fine tuning” –called adaptations when those traits are a
result of selection. Or also by chance, as only a subset of individuals survive and mate and there is a probabilistic
tag to traits passing on due to sampling error. Thus, some mouse lemurs may be able to tolerate dry winters (using
stored fat to produce metabolic water), cold nights (reducing metabolism and energy demands by using torpor),
reproduce earlier and faster (differential response to photoperiod and expression of polyestry), rely more on sugars
than lipids (diet changes across sites and seasons), live longer (some aged individuals showing Alzheimer’s-like
symptoms and other neurodegenerative conditions similar to those in humans). A comprehensive sampling pro-
gram including genetic, ecological, and environmental data will be needed to understand how much of the mouse
lemur genetic repertoire will be lost as a result of local extinction. Ultimately, examining the genetic structure and
diversification across populations will help us tell the tale of mouse lemur biogeographic history, using paleocli-
Whose Mouse Lemur Is It?
Goodman’s or MacArthur’s? It May Be Mittermeier’s…
by Dr. Marina Blanco
Marina’s field assistant, Chantal Hanitriniaina, from the Biology Depart-
ment at the University of Antananarivo (DEA recipient), with one of the
trapped mouse lemurs.
