Rufous Mouse Lemur, Microcebus rufus
RUFOUS MOUSE LEMUR
Microcebus rufus
Geographic Distribution and Habitat
The rufous mouse lemur, Microcebus rufus, also called the brown mouse lemur or russet mouse lemur, is native to just 2,000 square miles (5,200 square km) in southeastern Madagascar. That’s an area slightly bigger than Rhode Island and slightly smaller than Delaware, the two smallest US states. Rufous mouse lemurs live in rainforests, bamboo forests, abandoned agricultural fields, and eucalyptus groves.
Rufous mouse lemurs are often found at forest edges, but this may not be due strictly to preference. Forests in this region have become highly fragmented due to human activity. This means that instead of a wide expanse of forest, remaining habitat largely exists in small patches that are separated by roads, farms, villages, and other forms of human development. As a result, many species, including rufous mouse lemurs, are forced to occupy small areas of habitat and to live near forest edges, leaving them vulnerable to predators and to impacts from humans, such as vehicle strikes.
Rufous mouse lemurs were previously thought to extend farther in range than what is now believed. However, scientists believe the mouse lemurs occupying those areas are actually distinct species, and Goodman’s (M. lehilahytsara), Mittermeier’s (M. mittermeieri), Simmons’ (M. simmonsi), and Jolly’s (M. jollyae) mouse lemurs have all since been described and joined the genus.
Size, Weight, and Lifespan
Rufous mouse lemurs are among the smallest primates in the world. From the top of their head to the tip of their tail, they measure less than 10.6 inches (27 cm). Rufous mouse lemurs average just 3.4 inches (8.6 cm) without their tail. Their body weight varies considerably with the seasons, but on average, they weigh a diminutive 1.5 ounces (44 g) — about the weight of a golf ball. Males and females are about the same size. Mouse lemurs have lived over 18 years in captivity.
Appearance
Mouse lemur species are notoriously difficult to tell apart, but all species fall into one of two groups. At a glance, one can usually determine whether it falls into the “grayish” group of mouse lemurs or the “reddish” group. Rufous mouse lemurs fall into the latter, with their reddish-orange coat. Their coat pattern resembles that of a red and white corgi (dog) — in addition to their red coat, they have a white underbelly and a white stripe down the bridge of their nose. They have extremely large eyes that face forward on their heads, which allow them to collect as much light as possible in the pitch-black nighttime forest. Their hands are alien-like, with bulging fingertips that give them a sturdy grip on branches and tree trunks. Males and females look alike — which is to say that they do not exhibit sexual dimorphism, and babies are miniature (or, more accurately, extra-miniature) versions of their parents.
Diet
Rufous mouse lemurs are usually considered frugivorous — fruit eaters. However, their diet is very adaptable and varies considerably with the seasons. In addition to fruit, they also eat insects, flowers, tree gum, pollen, and nectar. One study of rufous mouse lemurs found that they consume 64 kinds of fruit and nine different orders of insects.
Behavior and Lifestyle
Like all mouse lemurs, rufous mouse lemurs are strictly nocturnal, which means they are awake at night. They move about quadrupedally, on all fours. They sometimes leap between branches and may occasionally walk on the ground. However, they spend almost all their time in trees, which makes them arboreal. They are known to travel up to 0.6 miles (1 km) in a night — a sizable distance for a creature that’s only a few inches long.
The activity levels, metabolism, and even body size of rufous mouse lemurs vary significantly with the seasons, driven by changes in daylight and food availability. From May to June — winter in the southern hemisphere — rufous mouse lemurs prepare for the coming period of food scarcity by fattening themselves. After this period, typically through September, they may enter a state of torpor. This is a hibernation-like state that allows them to drop their body temperature and slow their metabolism. During torpor, they lose 0.2 to 0.9 ounces (5 to 35 g) of weight, and their tail — an important reserve of fat during torpor —gets significantly thinner. Their metabolism drops by up to 90% and their body temperature falls to nearly the temperature of the environment around them. Torpor can occur daily, lasting hours to several days, or seasonal, which goes on for up to 24 weeks — almost half the year. Females are usually in torpor for a bit longer than males. Torpor is an important tool that helps the mouse lemurs to survive periods of low food availability by decreasing their calorie needs dramatically.
Mistletoe (yes, like the kind you kiss under) is a favorite fruit of rufous mouse lemurs and is often consumed to get them through times of food scarcity.
Curiously, not all mouse lemurs enter torpor. In fact, some individuals in the same population enter torpor while others do not. Some only enter torpor on a daily basis for several hours, while others enter a hibernation-like state for weeks. Scientists have not found any clear pattern to determine why some mouse lemurs enter torpor and others do not.
Rufous mouse lemurs sleep during the day in tree holes, leaf nests, or sometimes even in abandoned bird nests. They are mostly solitary, except during the breeding season. Normally, adult males live alone and adult females live with their offspring, if they have any. Sometimes, multiple mothers will sleep together with their babies during the day and help each other care for the young. Males have larger territories than females, around 650 feet (200 m) in diameter, which overlap two or more female territories. Less dominant males live on the outskirts of more dominant males’ territories.
Mouse lemurs are highly reliant on vocal communication. They have a very adept sense of hearing due to their large, bat-like ears, so they can pick up on quiet or distant sounds. Not only does this help them to stay safe from predators, but it also allows them to easily communicate with one another. This ability is particularly helpful around mating season, as it helps males and females to find each other. Females also use vocal communication to find each other to form sleeping groups.
Rufous mouse lemurs have a polygynous mating system, which means that each male mates with multiple females. Their courtship involves the male making soft squeaks and lashing out his tail to signal to a female that he is ready to mate. Mating occurs in September and October, and babies are born two months later. They give birth to one to three offspring at a time, creating leaf nests to keep their babies safe. Mothers nurse their babies for two months. Mothers sometimes form groups with each other to help raise their young communally, and they even nurse one another’s babies. Mouse lemurs use a tactic called “infant parking”, in which a mother “parks” her baby in a safe location at night while she forages. The baby is safe and hidden away from predators until the mother comes back after foraging to care for the baby. As they get older, young mouse lemurs begin to play with their mother by chasing her and jumping on her, which develops their locomotion skills. After a year, the offspring are sexually mature and the male offspring leave to form their own territories.
Rufous mouse lemurs live sympatrically — that is, they share the same habitat — with many other lemur species. These include eastern woolly lemurs (Avahi laniger), greater dwarf lemurs (Cheirogaleus major), aye-ayes (Daubentonia madagascariensis), common brown lemurs (Eulemur fulvus), greater bamboo lemurs (Prolemur simus), and diademed sifakas (Propithecus diadem).
Predators of rufous mouse lemurs include mongooses, predatory birds, snakes, and fossas, which are cat-like nocturnal predators. They are especially reliant on their keen sense of smell to detect predators, particularly fossas, which are extremely quiet hunters. Rufous mouse lemurs mainly rely on hiding to keep safe from predators.
The International Union for Conservation of Nature lists the rufous mouse lemur as Vulnerable (IUCN, 2017) appearing on the IUCN’s Red List of Threatened Species. The small area of extant that rufous mouse lemurs occupy is subject to slash-and-burn agriculture and other forms of habitat loss that has resulted in a severely disjointed and fragmented network of habitat patches.
Madagascar’s forests are being lost at an alarming rate. Between 2000 to 2023, the island lost 11.98 million acres (4.85 million ha) of forest cover — about a quarter of what had remained, which was already significantly reduced from its natural cover. Now, nearly half of its forest land is located less than 330 feet (100 m) from the forest edge, a result of widespread fragmentation. Slash-and-burn agriculture, which is called “tavy” in Madagascar, is a practice in which large swaths of forest are cut down and burned. The resulting ash fertilizes the soil, but only for a few growing seasons. The farmer is usually then forced to move to a new plot and start the process over, destroying even more habitat.
Rufous mouse lemurs are listed in Appendix I 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. Rufous mouse lemurs are protected by several protected areas, such as Ranomafana National Park, Andringitra National Park, and the Fandriana Vondrozo Midongy forest corridor (often referred to as the COFAV corridor, an abbreviation of its Malagasy name). The COFAV corridor protects 1,740 square miles (4,500 square km) of habitat that comprise 10% of Madagascar’s remaining rainforest and, as a result, it is an oasis for the many unique animal species that call this region home. It has been called the “lungs and water tower” of southeastern Madagascar, as it protects thirty different rivers and streams that empty into the ocean and reforestation efforts within its boundaries have resulted in the planting of 1.2 million trees. As a direct result of these restoration efforts, dried-up water sources have reappeared and new natural springs have emerged.
Experts have also called for conservation solutions that work with and support the Malagasy people alongside their ecosystem. For example, providing better support for employment and sustainable agriculture practices could help to curb slash-and-burn agriculture, which, in addition to causing widespread habitat loss, also perpetuates a cycle of poverty as farmers are forced to abandon their fields regularly. Other proposed solutions include better monitoring of parks and better enforcement of companies that profit off of unsustainable practices in Madagascar.
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- Deppe A., G. Kushnick. 2020. Olfactory predator recognition in the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar. Am J Primatol. 82.
- Ramananjato, V., O. Razafindratsima. 2021. Structure of microhabitats used by Microcebus rufus across a heterogeneous landscape. Int J Primatol 42:682–700.
- Suzzi-Simmons, A. 2023. Status of deforestation of Madagascar. Global Ecology and Conservation 42.
- Zimmermann, E. 2010. Vocal expression of emotion in a nocturnal prosimian primate group, mouse lemurs. In Handbook of Mammalian Vocalization. Handbook of Behavioral Neuroscience 19:215-225.
- https://www.iucnredlist.org/species/59544947/115588845
- https://wwf.panda.org/wwf_news/?319379/COFAV2DTo2Dthe2Dtwenty2Dyears2Dto2Dcome
- https://www.pbs.org/wgbh/rare/animals/rufous-mouse-lemur/index.html
- https://primate.wisc.edu/primate-info-net/pin-factsheets/pin-factsheet-mouse-lemur/
- https://animalia.bio/brown-mouse-lemur?taxonomy=316
- https://www.lemurconservationnetwork.org/learn/conservation-threats-and-solutions-for-lemurs/habitat-change-and-loss-in-madagascar/
Written by K. Clare Quinlan, August 2024