Dromiciops gliroides

Geographic Range

Monitos del monte ( Dromiciops gliroides ) are found in southern South America, specifically the northern portions of Patagonia, between 36 and 43 degrees south latitude. In addition to mainland South America, they are also found on Chiloe Island.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Monitos del monte are found in temperate forests and rainforests. They are mainly found in old-growth Nothofagus forests, but can be found in a variety of habitats ranging from dense thickets of bamboo ( Chusquea ) to open, secondary forests. A study of small mammals at elevations from 425 to 1,135 m above sea level in Chile found that monitos del monte were captured more often at higher elevations (820 to 1,135 m) than at lower elevations (425 to 715 m).

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

Physical Description

Monitos del monte are small, superficially mouse-like marsupials, with a short rostrum and small, rounded ears. Their pelage is short and dense. While the majority of their body is brownish gray, their shoulders and rump may have white patches. Their ventral pelage is a lighter color, ranging from yellowish white to pale gray. Although a whorling pattern is sometimes visible, their most distinct pelage characteristic is their pronounced black eye rings. Their head to body length is between 83 and 130 mm excluding their tail, which is between 90 and 132 mm long. Their tail is moderately prehensile and well-furred, except for a 25 to 30 mm naked underside portion, which may improve traction when the animal grasps tree branches. Monitos del monte weighs between 16 and 42 g. They resemble members of genus Marmosa , however, monitos del monte possess shorter limbs, more robust hands and feet, more semicircular upper incisors and smaller, furrier ears.

Seasonal variation and sexual dimorphism has been observed. A study of monitos del monte in Patagonia found that by the end of summer, females are significantly heavier and longer than males. Although both sexes use their tails as storage organs, females tend to have thicker tails; this suggests that females have higher energy needs during times of hibernation or torpor. While variation in tail thickness is seasonal, it is unclear if females are larger than males year-round. Geographic variation has also been reported in this species. Previously, two subspecies were recognized based on geography. Mainland monitos del monte were referred to Dromiciops australis australis and those from Chiloe Island were referred to Dromiciops australis gliroides . However, the only noticeable difference in appearance between these groups is the darker pelage of island monitos del monte. Due to insufficient distinguishing characters between mainland and island populations, separate subspecies are no longer recognized as distinct.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Reproduction

Monitos del monte become sexually mature after their second year and breed in the austral spring (August to September), breeding pairs form shortly beforehand. It is not known whether these pairs persist after mating.

• Mating System
• monogamous monogamous

Monitos del monte typically reach sexual maturity at age 2 and breed once yearly. Males and females form pairs and mate in August or September. Before parturition occurs, females construct small, rounded nests (about 200 mm in diameter) from sticks and water-repellent bamboo. These nests are located 1 to 2 m above the ground. Young are born approximately 3 to 4 weeks after conception and climb into the well-developed, anteroventral opening of the marsupium, where they remain attached to 1 of the 4 teats for approximately 2 months. Litters of up to 5 young have been reported, but females are unable to feed more than 4 offspring at a time. Although the young begin to exit the marsupium for short durations beginning in December, they do not become completely independent until March.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

Female monitos del monte suckle their altricial young for approximately 5 months (from early November to late March). Prior to their independence, females carry offspring in their marsupium or on their backs during "nocturnal family excursions".

• Parental Investment
• altricial altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Although the lifespan of monitos del monte is unknown in the wild, the longest recorded lifespan in captivity is 26 months.

Behavior

Monitos del monte are marsupials with nocturnal habits. They are arboreal or scansorial and use their prehensile tails, large hands and feet, and opposable halluces to climb trees. Although typically regarded as rare, they may be underrepresented in capture studies due to their avoidance of closed, box-type traps. Changes in ambient temperatures and food availability can induce spontaneous torpor in monitos del monte. They can exhibit daily fluctuations in body temperature and metabolic rate and are capable of shallow, short term torpor. Decreased ambient temperatures, coupled with decreased food cause deep, prolonged torpor (hibernation); this typically occurs during the winter and spring. This helps these animals survive in extreme environments. It also enables monitos del monte to conserve energy and avoid costly foraging when resources are limited.

• Key Behaviors
• arboreal arboreal
• scansorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• daily torpor
• solitary solitary

Home Range

The home range and territory size of monitos del monte is not known. A study in Patagonia estimated a summer population size of 54 individuals based on capture-mark-recapture methods.

Communication and Perception

Monitos del monte communicate via sound. At night they produce trilling calls that end in a coughing noise, as well as buzzing noises. Other modes of communication are not known. Similarly, although males and females form pairs during the breeding season, populations and social structures are not known during other times of the year.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Monitos del monte are primarily insectivorous, eating insects, larvae and pupae found on tree branches and in crevices in bark. Moths and butterflies also make up a large part of their diet. During the austral summer, monitos del monte consume large quantities of fleshy fruits, including mistletoe fruits. In captivity, monitos del monte eat a wide variety of food, including fruits, vegetables, potatoes, oats, invertebrates, vertebrates, meat, fish, eggs and cheese.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

• Plant Foods
• fruit

Predation

Predators of monitos del monte include native and introduced birds and mammals, particularly domestic cats . Monitos del monte are important prey items for several predators, they make-up the following percentages of their predator's diets: 10% for gray foxes , 3.6% for Darwin's foxes and a small portion for barn owls . Monitos del monte produce strong smelling secretions from cutaneous glands, which may deter predators. They also exhibit a threat posture with teeth exposed, particularly if aroused from torpor.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

In the temperate forests of Patagonia, monitos del monte are the sole seed dispersal agent of the mistletoe species Tristerix corymbosus . The seeds pass undamaged through their digestive tract and are deposited directly onto the bark of host trees. In fact, passage though their gut is necessary for the seeds to germinate and important for seedling recruitment. This mutualism may have evolved over the last 70 million years, and remains important for biodiversity today. Unlike other small mammals that may destroy consumed plant seeds, monitos del monte can disperse seeds from the majority of fleshy fruit-producing plant species in their region, including Aristotelia chilensis and Azara microphylla . Mistletoe, a parasitic climbing plant species, is important for maintaining understory plant diversity and facilitating ecosystem processes such as nutrient cycling. Additionally, nearly 100 families of birds and mammals rely on mistletoe for fruit, nectar and nesting material. Disruption of the mistletoe-monito del monte mutualism could cause extinctions, decreased biodiversity and increased susceptibility to drought. Monitos del monte are also hosts to blood parasites ( Hepatozoon ) and ticks ( Ixodes neuquenensis ).

• Ecosystem Impact
• disperses seeds
• keystone species keystone species

Economic Importance for Humans: Positive

Monitos del monte play a key role in seed dispersal for fleshy fruit-producing plants in temperate forests; this mutualism is important for the maintenance of biodiversity. Monitos del monte may also be important for reducing insect pests.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

In Chile, there are several superstitions about monitos del monte. For example, they have been erroneously described as bad luck, venomous and progenitors of disease. In extreme cases, people have burned their houses down after seeing monitos del monte in their places of residence. However, monitos del monte have no actual negative effects on humans.

Conservation Status

Although currently classified as near threatened on the IUCN Red List, monitos del monte are threatened by an increasing number of anthropogenic activities. The introduction of species such as domestic cats , deforestation and cattle grazing are associated with decreased abundances of monitos del monte and habitat fragmentation. A study of forest fragmentation found that human activity can reduce preferred tree types and increase susceptibility to predation. Monitos del monte, like many small mammals, are unable to cross even small deforested areas. They are also hosts to blood parasites ( Hepatozoon ) and ticks ( Ixodes neuquenensis ), which can further reduce the numbers of these important marsupials.

Other Comments

Monitos del monte belong to the most geographically restricted order of extant mammals. They are called a "living fossil" because they are the single extant representative of the microbiothere lineage. The oldest microbiothere may be a Khasia species, a fossil from Bolivia between 60.4 and 59.2 million years old.

Monitos del monte are more closely related to Australian marsupials than those from American. Two recent phylogenetic studies concluded that monitos del monte are a sister group to all other australidelphians (members of the orders Peramelemorphia , Notoryctemorphia , Dasyuromorphia , and Diprotodontia ). Microbiotheria likely diverged from this Australasian clade approximately 67.4 million years ago. Although morphological studies nest Dromiciops within the Australasian clade as well, many of the morphological characters are believed to be homoplasious or plesiomorphic.

Additional Links

Encyclopedia of Life

Contributors

Leila Siciliano Martina (editor), Texas State University.

Jennifer Chick (author), Case Western Reserve University, Darin Croft (editor, instructor), Case Western Reserve University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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