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Madame Berthe's mouse lemur (''Microcebus berthae'') or Berthe's mouse lemur is the smallest of the
mouse lemur The mouse lemurs are nocturnal lemurs of the genus ''Microcebus''. Like all lemurs, mouse lemurs are native to Madagascar. Mouse lemurs have a combined head, body and tail length of and weigh , making them the smallest primates (the smallest sp ...
s and the smallest
primate Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
in the world; the average body length is and seasonal weight is around . ''Microcebus berthae'' is one of many species of Malagasy lemurs that came about through extensive
speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...
, caused by unknown environmental mechanisms and conditions. This primate is found chiefly in the Kirindy Forest in western
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
. After its discovery in 1992 in the dry deciduous forest of western Madagascar, it was initially thought to represent a rediscovery of '' M. myoxinus'', but comparative morphometric and genetic studies revealed its status as a new species, ''M. berthae''. This lemur is named after the conservationist and primatologist Berthe Rakotosamimanana of Madagascar, who was the Secretary General of the ''Groupe d'Etudes et de Recherche des Primates'' (GERP) from its founding until her death in 2005.


Physical description

''Microcebus berthae'' has short, dense dorsal pelage that is bicolored cinnamon and yellow
ochre Ochre ( ; , ), iron ochre, or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colou ...
. The middorsal stripe is tawny in color. The midventral area of this species is chamois in color while the flanks are a mixture of pale chamois and light pale neutral gray. The dorsal and ventral underfur is neutral blackish neutral gray in color. The tail has short hair that is tawny. The crown and ears are also tawny in color. The
orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...
are surrounded by a narrow dark band. The area between the eyes is cinnamon in color. The hands and feet are dull beige.


Distribution and habitat

Madame Berthe's mouse lemur is known to live in Kirindy Forest in
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
. It is now likely
extirpated Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions. Local extinctions mark a chan ...
from the Andranomena Special Reserve and the Analabe private reserve. Madame Berthe's mouse lemurs use the tangles of tree vines to sleep in. Because of its limited spread, it is thought that they are specialist creatures that will live only in that one specific environment. Another idea suggests that they most likely compete with the gray mouse lemur (''M. murinus)'', chiefly for resources. Because of the high rate of deforestation in the surrounding Menabe forests (52%) between 1985 and 2000, less than of inhabitable forests remained between Kirindy Park, the Tsiribihina River, and the Reserve. Given that this lemur occurs at 0.36 lemurs per ha, it is estimated that about 7,920 mouse lemurs were left in the area in the year 2000. With
deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
continuing to occur on the island nation, the species is listed as
critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
, at best.


Behavior

''Microcebus berthae'' are typically solitary foragers, but are not without social interaction with other members of their species. About half the time, they sleep alone. Otherwise, they can be found sleeping next to one or more lemurs, with no preference or prejudice to close relatives or members of the opposite sex. Be it alone or in a group, ''Microcebus berthae'' tend to sleep in leaf nests in trees, or without a nest, in hole-like structures. On occasion, the paths of two members of the species may cross, leading to different kinds of social encounters. Some encounters involve bouts of mutual grooming, sex, or huddling (an activity which can last up to 23 minutes). Other meet-ups between lemurs might include chasing, biting and grabbing. Overall, male-male and female-female interactions do not differ qualitatively. Unlike other species of lemur, ''Microcebus berthae'' do not
hibernate Hibernation is a state of minimal activity and metabolic reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is most ...
during the cold-dry season, instead compensating for food scarcity with a larger than average home range. In a population of ''Microcebus berthae'', males significantly outnumber females. Despite there being no
sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
in skull length, canine height, or tail length, the average female is larger than the average male in head-body length and head width. Average body mass, while relatively equal during mating season, becomes smaller for males in the duration of time excluding mating season. Males have a home range of about , while females have a home range of about . Females tend to remain in a home range that is close to, or includes their place of birth. This is the opposite of males, who tend to disperse from their place of birth. The home ranges of individual lemurs tend to overlap with each other, with female home ranges overlapping with that of one or two other females, and male home ranges overlapping with that of up to nine other males. Social systems of ''M. berthae'' are more similar to the gray mouse lemur (''Microcebus murinus'') than the fat-tailed dwarf lemur (''Cheirogaleus medius''), i.e. Madame Berthe's mouse lemur is sexually promiscuous rather than
monogamous Monogamy ( ) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g. ...
. The range in distance of males is larger than that of the females in both Microcebus species, both before and after mating seasons. Research has also been conducted on the distribution of sleeping sites, as well as on testes size and the presence of vaginal plugs. Study of capture rates and physiological proof reveals no evidence that ''M. berthae'' has a hibernation season, which increases the chances of sexual activity within the species.


Ecology

Mouse lemurs are considered to be a
cryptic species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
. The species-rich mouse lemur genus ''Microcebus'' is distributed over nearly all remaining forest areas of
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
with a high variability in species distribution patterns and are very similar morphologically. They are so similar that the gray mouse lemur was considered the only mouse lemur until recent studies proved it to be otherwise. Along with other morphological similarities, the Madame Berthe's mouse lemur and the gray mouse lemur share a similar diet (both containing the same food groups but in different proportions) and live in the same region of western Madagascar. Both of these ''Microcebus'' species have an
omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...
diet, and used the same food sources, including sugary
homoptera Hemiptera (; ) is an order of insects, commonly called true bugs, comprising more than 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, assassin bugs, bed bugs, and shield bugs. They range in size from to ...
n secretions, fruit, flowers, gum,
arthropods Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
and small vertebrates (e.g. geckos, chameleons). Because of their recent common ancestry, closely related species ought to exhibit high similarities in their use of biotic and
abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them und ...
resources, susceptibility to predators and responses to disturbances and stress. However, despite the overlapping niches, studies have shown that the territories of the two mouse lemur species have very little to no overlap. The Madame Berthe's mouse lemur population is sparse and spread out over a more widespread area; while the gray mouse lemurs had a much denser population in a smaller area. The reason for the mouse lemur species' mutual avoidance is not yet clearly known. The gray mouse lemur has several competitive advantages over Madame Berthe's mouse lemur. It is about twice as large as Madame Berthe's mouse lemur. It also has the advantages of being a generalist, and having fewer deaths by predation, with 70% predation mortality for Madame Berthe's mouse lemur, vs. 50% predation mortality for the gray mouse lemur. The areas used exclusively by each species share structural characteristics and food sources. Gray mouse lemurs are able to live in more types of vegetation than Madame Berthe's mouse lemur yet have smaller, denser territories. This suggests that their avoidance does not stem from environmental differences, but rather by competitive coexistence.


Diet

Madame Berthe's mouse lemur shares its niche with the sympatric gray mouse lemur (''Microcebus murinus''). Both lemurs feeding ecology suggests that there is a coexistence behavior between the two lemur species. Both species are found in western Madagascar's highly seasonal dry
deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...
forest. Madame Berthe's mouse lemur has a very narrow feeding niche unlike the sympatric gray mouse lemur which has a much broader niche. The feeding ecology and the types of food available depend on the type of season in the niche of ''Microcebus berthae'' and ''Microcebus murinus''. During the wet,
rainy season The rainy season is the time of year when most of a region's average annual rainfall occurs. Rainy Season may also refer to: * ''Rainy Season'' (short story), a 1989 short horror story by Stephen King * "Rainy Season", a 2018 song by Monni * '' ...
, more unripe fruit is available which decreases its abundance in the dry season. However, ripe fruit are available all year round with maximum abundance in the
dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The t ...
. As a food source, flying insects are available in both seasons, but are abundant in the wet season. Madame Berthe's mouse lemur is an omnivore and mainly feeds on fruits and flowers of different tree and shrub species, insect secretions, gum, arthropods and small
vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
like
geckos Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates. They range from . Geckos are unique among lizards f ...
and chameleons. Compared to the dry and the wet season of Madame Berthe's mouse lemur's niche, it spends more time feeding in the dry season while the wet season is used for mating. Compared to the sympatric gray mouse lemur, Madame Berthe's mouse lemur eats mainly insects, and fruit only occasionally. Similar to the sympatric gray mouse lemur, Madame Berthe's mouse lemur is able to adapt to the fluctuation of resources. There is a high overlap in the feeding niche of both lemurs suggesting that they avoid competition by mutually excluding each other on a small scale.


Status

As of December 2019, Madame Berthe's mouse lemur is rated
critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
by the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
. The main threat to this species is
deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
and habitat degradation from
Slash-and-burn Slash-and-burn agriculture is a form of shifting cultivation that involves the cutting and burning of plants in a forest or woodland to create a Field (agriculture), field called a swidden. The method begins by cutting down the trees and woody p ...
agriculture,
illegal logging Illegal logging is the harvest, transportation, purchase, or sale of timber in violation of laws. The harvesting procedure itself may be illegal, including using corrupt means to gain access to forests; extraction without permission, or from a p ...
and charcoal production. The Menabe-Antimena Protected Area has been established to protect the Kirindy Forest and the surrounding areas. However, this has been poorly enforced and deforestation proceeds unhindered. If the deforestation continues at the current rate, it is estimated that Madame Berthe's mouse lemur will become
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
within 10 years. As of 2019, there are no Madame Berthe's mouse lemurs being kept in captivity.


See also

*
Smallest organisms The smallest organisms found on Earth can be determined according to various aspects of organism size, including volume, mass, height, length, or genome size. Given the incomplete nature of scientific knowledge, it is possible that the smallest or ...


References


External links

* * New England Primate Conservatory https://neprimateconservancy.org/madame-berthes-mouse-lemur/ {{Taxonbar, from=Q827793 Mammals described in 2000 Mouse lemurs Mammals of Madagascar Species that are or were threatened by deforestation