Gerp’s Mouse Lemur, Microcebus gerpi
GERP'S MOUSE LEMUR
Microcebus gerpi
Geographic Distribution and Habitat
The Gerp’s mouse lemur is found only in the Sahafina forest and surrounding “savoka” (fallow farmland with cultivated trees) in eastern Madagascar. The Sahafina forest is a mix of dense evergreen lowland forest and formerly logged woodland currently in the process of recovering. The latter type of forest is also known as a secondary forest. The Sahafina forest is located 0.018-0.14 miles (29-230 m) above sea level and is particularly humid due to being sandwiched between the Central Highlands of Central Madagascar and the Indian Ocean. These two natural barriers have also led to the evolution of numerous unique species within the area, including the Gerp’s mouse lemur.
Size, Weight, and Lifespan
There are 25 mouse lemur species, and they are the smallest primates in the world! The Gerp’s mouse lemur is one of the biggest species within the genus, weighing in at a whopping mean weight of 2.4 ounces (68 g). From head to tail, females come in at a mean length of 4.8 inches (122 mm), while males reach 4.7 inches (120 mm). Females have been measured to be slightly larger than males, but this is likely due to a small sample size.
Mouse lemurs tend to live to six or seven years in the wild.
Appearance
Besides their small size, mouse lemurs can be generally characterized by their long, furry tails, big eyes, long fingers, and round bodies and heads. All mouse lemurs have a white strip between their eyes. They are physically adapted to nocturnal life with their big eyes and protruding, flexible ears.
Gerp’s mouse lemurs can be differentiated from their relatives through their larger overall size, small ears, and long snouts and tails. Their tails are covered in long, dense, brownish-gray fur, and can store fat. The Gerp’s mouse lemur has dark brownish-gray fur on the back, with a broad, reddish line down the middle. The fur along their belly varies from a light gray to creamy white and extends from the throat to the genitals. The legs and outer arms are dark, contrasting with the rest of the body, while pinkish-brown skin is visible on their hands, feet, and snout. The head is reddish in color, with darker brown surrounding the large, light copper eyes. Finally, the ears are edged with dark brown.
All lemuriforms, the suborder which includes galagos, lemurs, and lorises, have a toothcomb. A toothcomb is a set of lower-front teeth which are used for grooming.
Diet
The Gerp’s mouse lemur is primarily insectivorous, eating a variety of insects, spiders, and small invertebrates. They supplement their diet with fruit, nectar, and tree gums.
Behavior and Lifestyle
The Gerp’s mouse lemur is nocturnal (active at night) and arboreal (tree-dwelling). From dawn to dusk, they sleep in tree hollows, nests made of leaves, or in dense vegetation. Along with their fur camouflaging them amongst the trees, these sleeping sites provide them with protection from predators, such as snakes, owls, and fossas. Speaking of sleeping, during the day, the Gerp’s mouse lemur enters a state known as torpor, which is similar to hibernation. Torpor involves a significant reduction in their metabolic rate and body temperature, allowing them to conserve energy and survive periods when food may be scarce.
Upon waking at night, they use their long, delicate limbs to leap from tree to tree, their long tails to balance among the branches, and specialized digits on their hands and feet to securely grip branches. Nights are spent searching for food and occasionally engaging in social behaviors, such as grooming and mating.
What’s in a name?: The Gerp’s mouse lemur is named after the Malagasy organization GERP (Groupe d’Etude et de Recherche sur les Primates de Madagascar), which unites primatologists working on Madagascar and is dedicated to research and the conservation of lemurs.
The Sahafina forest in which the Gerp’s mouse lemur is found was not studied in depth until 2008. This is also why the species was not officially described until 2012.
The tiniest brains of any primate: Weighing in at just 2 grams, mouse lemurs have the smallest brains of any primate in the world.
The Gerp’s mouse lemur is primarily solitary, with males occupying larger home ranges compared with females. They mark their territories using scent glands, ensuring that there is little overlap between neighboring individuals. Besides these facts, there is not much else available regarding the social activity of the Gerp’s mouse lemur. More research is needed.
Despite the lack of data, it is known even the most solitary of mouse lemurs commonly gather in communal sleeping sites. With what we know of the Gerp’s mouse lemur’s closest relatives, we can assume that closely related females gather in sleeping dens of 2-5 individuals daily, while males sleep alone. It is also possible that males and females sleep together, especially during the breeding season. There is a subtle dominance hierarchy in most species of mouse lemurs, with females often having dominance over males. This social organization becomes more evident in captive populations.
There is no data on whether or not the Gerp’s mouse lemur engages with other species, including other lemur species.
Once again, data is lacking specifically on the Gerp’s mouse lemur and must be inferred from closely related species.
From what we know of mouse lemurs as a whole, they are capable of making several different vocalizations, mostly made up of trills and whistles. These calls include mating calls, predator warnings, trills for their morning reunion at their sleeping sites, and calls potentially meant to signal territorial dominance. Babies have their own repertoire of calls to enable staying in contact with their mothers. Some species of mouse lemurs also make ultrasonic calls that cannot be heard by humans without special equipment.
Mouse lemurs use their urine for scent-marking, not only to mark their territory and alert others to their presence but to advertise their reproductive receptivity.
The Gerp’s mouse lemur experiences seasonal reproduction, with breeding occurring between September and November. There are no other data available regarding the reproduction specifically of Gerp’s mouse lemurs, but much can be inferred from other mouse lemur species.
If we look at the Gray mouse lemur (M. murinus), after a gestation (pregnancy) period of around 60 days, females typically give birth to one to three offspring, known as pups. Born undeveloped, with closed eyes and weighing only a few grams, and highly dependent on Mom for food and protection, they cling to her fur, camouflaging themselves with their surroundings to avoid predation. For the first few weeks in the big wide world, the pups will remain in their mother’s nest, receiving a constant supply of milk and grooming sessions. As they grow older, the pups become more active and curious about their surroundings, exploring under the watchful eyes of Mom.
Around the age of two to three months, pups begin to gain more independence, venturing out on their own, but still rely on their mother for guidance and protection. She’ll continue to nurse and care for her young until four to five months of age when the pups are fully weaned. As the months go by, Mom teaches vital survival skills to her young, such as establishing territory, foraging for food, and identifying potential threats.
Sexual maturity, and thus, full-fledged independence, is reached at one year of age. However, it may take a bit longer for males to fully develop. From that point on, the newly crowned adults disperse to establish territories of their own.
As insectivores, Gerp’s mouse lemurs serve as pest controllers through their consumption of insects. As part of their diet may also consist of fruit, they aid in the regeneration of their forest habitat by dispersing seeds through their feces during their nightly travels. They additionally play a role in pollination. Like bees and butterflies, they collect pollen from flowers while drinking nectar. They then deposit the pollen on each flower they visit, thereby pollinating the plants. Finally, as a prey species, they also play a role in feeding local predators within their habitat.
The International Union for Conservation of Nature lists the Gerp’s mouse lemur as Critically Endangered (IUCN, 2014), appearing on the IUCN Red List of Threatened Species.
Like nearly all lemurs of Madagascar, the Gerp’s mouse lemur is threatened by very high rates of habitat loss and degradation. The eastern lowland rainforests in which the mouse lemur live are threatened in particular by unsustainable farming practices and logging. The Gerp’s mouse lemur is also hunted by humans, possibly for bushmeat.
The Gerp’s mouse lemur is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.
The Gerp’s mouse lemur does not occur in any protected areas within their tiny range. The work of GERP has certainly been nothing but helpful with regard to their namesake mouse lemur by enforcing environmental protection laws, re-foresting degraded areas, educating locals, and providing opportunities to Malagasy college students.
All-in-all, conservation actions needed to ensure the survival of this tiny, adorable, and unique species include proper land and water protection, site/area protection, and additional research as a whole on the species, along with further monitoring of their population trends, harvest level trends, and trends in their habitat.
- https://www.alltheworldsprimates.org/Members/Home/MasterPrimate.aspx?tid=1144
- https://animalia.bio/gerps-mouse-lemur
- https://animalinformation.com/animal/gerps-mouse-lemur/
- https://www.crittersquad.com/fact-sheets/mouse-lemur-fact-sheet/
- https://en.wikipedia.org/wiki/Gray_mouse_lemur
- https://en.wikipedia.org/wiki/Gerp%27s_mouse_lemur
- https://en.wikipedia.org/wiki/Mouse_lemur
- https://www.lemurconservationnetwork.org/organization/gerp/
- https://lemur.duke.edu/wordpress/wp-content/uploads/2022/08/VT-11-transcript-2022.pdf
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-mouse-lemur/
Written by Sienna Weinstein, August 2024