NORTHERN GIANT MOUSE LEMUR
Geographic Distribution and Habitat
The northern giant mouse lemur is endemic to Madagascar. They are found primarily in the dry forests of the northwest region of the Ampasindava Peninsula, specifically in Ambato and Pasandava. They also inhabit secondary forests, old banana plantations, gallery forests, and abandoned cashew orchards.
Madagascar is well known for being a biodiversity hotspot, and it is not uncommon for new species to be discovered hiding in plain sight. Despite the differences in their geographic distribution and physical size, prior to 2005 all giant mouse lemurs had been considered to be one species under the genus Mirza. In 2005, however, morphometric, genetic, and behavioral data resulted in the distinction of a second species, the northern giant mouse lemur (Mirza zaza). The northern giant mouse lemur is smaller than its counterpart, the Coquerel’s giant mouse lemur (Mirza coquereli), and lives further north on the island.
Size, Weight, and Lifespan
Despite their name, northern giant mouse lemurs are relatively small, weighing .33 pounds (150 g) as juveniles and growing to .66 pounds (300 g) as a fully matured adult. Females and males can both measure up to 8.6 inches (22 cm) long.
Not much is known about their longevity, though it is likely they can live between 20–25 years, similar to the lifespan of the Coquerel’s giant mouse lemur.
Like most nocturnal primates, northern giant mouse lemurs have large, round, reflective eyes that take in every bit of available light in the dark nighttime forest. Their cryptic coat coloring ranges from cream on their bellies to a tan or brown on their backs to help them to hide from predators. They have unusually long, fluffy tails, often rusty orange in color, that help them to balance as they nimbly maneuver through the trees. Their large ears are so thin, they’re partially transparent.
Their most distinctive physical feature is unique to the males of the species—they have the largest testes-to-body ratio of all mammals. This trait is strongly linked to their highly promiscuous year-round mating behavior, which, in turn, is attributed to the year-round availability of nutrient-rich foods in their region.
Northern giant mouse lemurs have a wide menu to choose from, primarily consuming fruits, flowers, and plant exudates. During the dry season, they feed on the sugary secretions of larvae from insects, specifically those in the Flatidae family of fulgoroid planthoppers.
Nutrition-rich food availability may be the factor that allows the northern giant mouse lemur to reproduce year-round, unlike other lemur species that mate seasonally. Their habitat is located between evergreen rainforests to the north and dry deciduous forests in the south. Many trees in the region, therefore, retain their leaves throughout the year. In addition, they have the added benefit of feeding on the sugary secretions of the larvae of planthoppers in the dry season. This means that food availability, or lack thereof, does not limit reproduction, as it might in other regions that experience more dramatic fluctuations in climate and food sources.
Behavior and Lifestyle
Like other mouse lemurs, the northern giant mouse lemur is nocturnal and arboreal. They spend most of the day in leaf nests, tree holes, and vegetation tangles. These play a crucial role in their daily life. Many of the nests lie high in the trees at about 52 feet (16 m) or higher, keeping them far from most predators and protecting them from any harsh environmental conditions. Nests are often used for long periods of time, up to 44 days or more.
Between 2 to 8 individuals of either gender and any age share nests. Even multiple adult males share sleeping sites. This is rather unusual for nocturnal strepsirrhines, especially lemurs, who usually sleep in small groups consisting of a mother and her offspring, and with males leading a more solitary lifestyle.
Northern giant mouse lemurs build nests high in the trees to not only protect themselves from predators, but also from harsh environmental conditions such as strong winds and monsoons!
Northern giant mouse lemurs are very hard to find in the wild, due to being nocturnal and living high in the trees.
Male northern giant mouse lemurs have the largest testes to body ratio of all mammals.
Due to their nocturnal lifestyle and relatively recent discovery, northern giant mouse lemurs are understudied, thus detailed information pertaining to their daily life and group dynamics is scant. What is known is that they live in dispersed multi-male/multi-female groups that leave their sleeping sites during the evening and return to their nests just before dawn. There have been rare instances of them leaving their nests during daylight hours based on the availability of resources.
During the first half of the night, northern giant mouse lemurs are most active foraging and feeding. By the second half of the night, when their bellies are full, they relax and groom one another.
Group home range sizes are estimated to measure from .004 to .009 square miles (1 ha to 2.4 ha). Northern giant mouse lemur groups often overlap, though they tend to be rather passive with one another and rarely display aggressive behaviors.
Northern giant mouse lemurs use a variety of calls and communication methods. One of the most common calls is the “hn” call, which is typically rather quiet and is emitted during locomotion and meetings with familiar individuals. Other vocalizations, such as alarm calls, territorial calls, and mating calls, are emitted frequently.
Another form of communication is scent-marking, which is used to advertise territory, and to communicate with mates and other individuals.
Visual cues are also an important form of communication for giant mouse lemurs. When they are frightened or feel threatened, they stay very still so predators cannot spot them. This behavior also acts as a warning to other group members that may see their fellow group member frozen in their tracks.
Northern giant mouse lemurs breed at any time throughout the year. They have what is referred to as a “scramble” form of mating, in which their sex ratios are roughly equivalent and males and females are evenly distributed throughout the habitat. This is in contrast to a “contest model,” in which there are many females that tend to stay congregated, and males that compete for mating opportunities.
Males use specific mating calls to attract females and roam widely to find mates. In preparation for mating, males’ testicles fill with sperm cells and grow significantly—up to 5 times their initial size! Once this occurs, the size of their testicles do not decrease, as they do in species who mate seasonally. Somewhat comically, the size of their testes create some locomotive challenges as they navigate tree branches and vine tangles! Bruised testicles are not unusual.
When females are ready to mate, they emit estrous calls to attract males. After mating, they give birth to one offspring after about three months. Because they mate year-round, within a year they give birth to 2 or 3 infants. Mothers are the sole care providers for the young, nursing and carrying them. Little is known about how long infants stay with the mother, however they reach maturity around one year of age.
Northern giant mouse lemurs play a significant role in dispersing seeds from the fruit they eat throughout their range. They also serve as prey to other animals such as large hawks, owls, and snakes.
The northern giant mouse lemur is considered Vulnerable by the International Union for Conservation of Nature (IUCN, 2018), appearing on the IUCN’s Red List of Threatened Species. They are constantly at risk from forest destruction due to slash-and-burn agriculture.
The northern giant mouse lemurs’ enthusiastic year-round mating and reproduction cannot keep pace with habitat loss, a threat which supersedes their ability to repopulate. Although they can adapt well to secondary and degraded forests, the forests they live in are among the fastest declining habitats in Madagascar, with over a 40% decrease in forest cover from 1975 to 2000.
Northern giant mouse lemurs are listed on Appendix I of the Convention on International Trade in Endangered Species (CITES). They are known to occur in the Sahamalaza-Iles Radama National Park and may be present in the Manongarivo Special Reserve as well as in a few forests that lie within their distribution range (Antafondro, Andranomatavy, Anjanazanombandrany, and Antsakay Kalobenono).
Much more information is needed to determine the distribution and abundance of northern giant mouse lemurs. Some activities that can help gain more knowledge and improve the well-being of giant mouse lemurs and their habitats includes forest patrol and control, animal monitoring, animal behavior and population density studies, effective environmental conservation education and environmental awareness, and including local communities in conservation programs and activities.
- Hending, D., Randrianarison,H., Cotton, S., Holderied, M., and McCabe, G. 2021. Observations of daytime activity in the nocturnal northern giant mouse lemur (Mirza zaza). Behaviour. (58)69-76.
- Rabemananjara, N., et al. (2018). A survival blueprint for the Northern giant mouse lemur, Mirza zaza.in Madagascar and an EDGE of Existence Fellowship, Zoological Society of London, London, UK.
- Rode-Margono, E., Anne-Isola Nekaris, K., Markolf, M., Schliehe-Diecks, S., Seiler, M., Radespiel, U., & Schwitzer, C. 2013. Social organisation of the northern giant mouse lemur Mirza zaza in Sahamalaza, north western Madagascar, inferred from nest group composition and genetic relatedness, Contributions to Zoology, 82(2), 71-83.
- Seiler M, Hending D, Stanger-Hall KF. 2019. Spacing and Mate Attraction: Sex-Specific Function of Advertisement Calls in the Northern Giant Mouse Lemur (Mirza zaza). Folia Primatol (Basel). 90(5):361-378.
Written by Tara Covert, June 2021