The monito del monte or colocolo opossum, ''Dromiciops gliroides'', also called ''chumaihuén'' in
Mapudungun
Mapuche (, Mapuche & Spanish: , or Mapudungun; from ' 'land' and ' 'speak, speech') is an Araucanian language related to Huilliche spoken in south-central Chile and west-central Argentina by the Mapuche people (from ''mapu'' 'land' and ''che ...
, is a diminutive
marsupial
Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...
native only to southwestern
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
(
Argentina
Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...
and
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
). It is the only extant species in the ancient order
Microbiotheria
Microbiotheria is an australidelphian marsupial order that encompasses two families, Microbiotheriidae and Woodburnodontidae, and is represented by only one extant species, the monito del monte, and a number of extinct species known from fossi ...
, and the sole New World representative of the superorder
Australidelphia (all other New World marsupials are members of the
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
Ameridelphia
Ameridelphia is traditionally a superorder that includes all marsupials living in the Americas except for the Monito del monte (''Dromiciops''). It is now regarded as a paraphyletic group.
Orders
The orders within this group are listed below:
* ...
). The species is
nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
and
arboreal
Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...
, and lives in thickets of
South American mountain bamboo in the
Valdivian temperate rain forests
The Valdivian temperate forests (NT0404) is an ecoregion on the west coast of southern South America, in Chile and Argentina. It is part of the Neotropical realm. The forests are named after the city of Valdivia. The Valdivian temperate rainforest ...
of the southern
Andes
The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...
, aided by its partially
prehensile tail
A prehensile tail is the tail of an animal that has adapted to grasp or hold objects. Fully prehensile tails can be used to hold and manipulate objects, and in particular to aid arboreal creatures in finding and eating food in the trees. If the ta ...
. It eats primarily
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...
s and other small invertebrates, supplemented with
fruit
In botany, a fruit is the seed-bearing structure in flowering plants that is formed from the ovary after flowering.
Fruits are the means by which flowering plants (also known as angiosperms) disseminate their seeds. Edible fruits in particu ...
.
Taxonomy and etymology
''Dromiciops gliroides'' is the sole extant member of the order
Microbiotheria
Microbiotheria is an australidelphian marsupial order that encompasses two families, Microbiotheriidae and Woodburnodontidae, and is represented by only one extant species, the monito del monte, and a number of extinct species known from fossi ...
.
It was first
described by British zoologist
Oldfield Thomas
Michael Rogers Oldfield Thomas (21 February 1858 – 16 June 1929) was a British zoologist.
Career
Thomas worked at the Natural History Museum on mammals, describing about 2,000 new species and subspecies for the first time. He was appoin ...
in 1894. The
generic name ''Dromiciops'' is based on the resemblance of the monito del monte to the
eastern pygmy possum
The eastern pygmy possum (''Cercartetus nanus'') is a diprotodont marsupial of south-eastern Australia. Occurring from southern Queensland to eastern South Australia and also Tasmania, it is found in a range of habitats, including rainforest, s ...
(''Cercartetus nanus''), one of the synonyms of which is ''Dromicia nana''. The specific name ''gliroides'' is a combination of the Latin ''glis, gliris'' ("dormouse", more generally "rodent") and Greek ''oides'' ("similar to"). The name ''australis'' in a synonym (''D. australis'') refers to the southern distribution of the animal.
The common name monito del monte is Spanish for "mountain monkey", or "monkey of the mountains".
In his 1943 ''Mammals of Chile'', American zoologist
Wilfred Hudson Osgood
Wilfred Hudson Osgood (December 8, 1875 – June 20, 1947) was an American zoologist.
Biography
Osgood was born in Rochester, New Hampshire, the oldest child of a family of watchmakers. The family moved to California in 1888 and he went to study ...
identified two
subspecies
In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...
of the monito del monte:
*''Dromiciops gliroides australis''
F. Philippi, 1893: It occurs in the
Valdivian temperate rain forest
The Valdivian temperate forests (NT0404) is an ecoregion on the west coast of southern South America, in Chile and Argentina. It is part of the Neotropical realm. The forests are named after the city of Valdivia. The Valdivian temperate rainfore ...
in southcentral
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
.
*''Dromiciops gliroides gliroides''
Thomas, 1894: It occurs in the northeastern
Chiloé Island
Chiloé Island ( es, Isla de Chiloé, , ) also known as Greater Island of Chiloé (''Isla Grande de Chiloé''), is the largest island of the Chiloé Archipelago off the west coast of Chile, in the Pacific Ocean. The island is located in southern ...
.
Phylogeny and biogeography
![Phylogenetic tree of marsupials derived from retroposon data - journal](https://upload.wikimedia.org/wikipedia/commons/e/e9/Phylogenetic_tree_of_marsupials_derived_from_retroposon_data_-_journal.pbio.1000436.g002.png)
South American marsupials have long been suspected to be ancestral to those of
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, consistent with the fact that the two continents were connected via
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
in the early
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
. Australia's earliest known marsupial is ''
Djarthia
''Djarthia'' is an extinct monotypic genus of marsupial. It is the oldest marsupial found in Australia, discovered at the Murgon fossil site in south-eastern Queensland.
''D.'' ''murgonensis'' was described from material identified as Early ...
'', a primitive
mouse
A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
-like animal that lived in the early
Eocene
The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...
about 55 million years ago (mya). ''Djarthia'' had been identified as the earliest known australidelphian, and this research suggested that the monito del monte was the last of a
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
that included ''Djarthia''. This relationship suggests that the ancestors of the monito del monte might have reached South America by back-migration from Australia. The time of divergence between the monito del monte and Australian marsupials was estimated to have been 46 mya.
However, in 2010, analysis of
retrotransposon
Retrotransposons (also called Class I transposable elements or transposons via RNA intermediates) are a type of genetic component that copy and paste themselves into different genomic locations (transposon) by converting RNA back into DNA through ...
insertion sites in the
nuclear DNA
Nuclear DNA (nDNA), or nuclear deoxyribonucleic acid, is the DNA contained within each cell nucleus of a eukaryotic organism. It encodes for the majority of the genome in eukaryotes, with mitochondrial DNA and plastid DNA coding for the rest. It ...
of a variety of marsupials, while confirming the placement of the monito del monte in Australidelphia, also clarified that its
lineage
Lineage may refer to:
Science
* Lineage (anthropology), a group that can demonstrate its common descent from an apical ancestor or a direct line of descent from an ancestor
* Lineage (evolution), a temporal sequence of individuals, populati ...
is the most
basal of that superorder. The study further confirmed that the most basal of all marsupial orders are the other two South American lineages (
Didelphimorphia and
Paucituberculata
Paucituberculata is an order of South American marsupials. Although currently represented only by the seven living species of shrew opossums, this order was formerly much more diverse, with more than 60 extinct species named from the fossil rec ...
, with the former probably branching first). This conclusion indicates that Australidelphia arose in South America (along with the ancestors of all other living marsupials), and probably reached Australia in a single
dispersal event after
Microbiotheria
Microbiotheria is an australidelphian marsupial order that encompasses two families, Microbiotheriidae and Woodburnodontidae, and is represented by only one extant species, the monito del monte, and a number of extinct species known from fossi ...
split off. Fossils of another Eocene australidelphian, the microbiotherian ''
Woodburnodon casei'', have been described from the
Antarctic peninsula
The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...
,
and fossils of a related early Eocene woodburnodontid have been found in
Patagonia
Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...
.
Habitat
Monitos del monte live in the dense forests of highland Argentina and Chile, mainly in trees, where they construct spherical nests of water-resistant
colihue leaves. These leaves are then lined with moss or grass, and placed in well-protected areas of the tree, such as underbrush, tree cavities, or fallen timber. The nests are sometimes covered with gray moss as a form of
camouflage
Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the ...
. These nests provide the monito del monte with some protection from cold, both when it is active and when it
hibernates.
Fragmentation of
Valdivian temperate rainforest
The Valdivian temperate forests (NT0404) is an ecoregion on the west coast of southern South America, in Chile and Argentina. It is part of the Neotropical realm. The forests are named after the city of Valdivia. The Valdivian temperate rainforest ...
s into non-contiguous areas is known to reduce the abundance of monitos del monte in a given area, but has little or no impact on whether it occurs in an area or not.
Morphology
Monitos del monte are small marsupials that look like mice. ''Dromiciops'' have the same dental formula as
''Didelphids'': , a total of 50 teeth. Their size ranges from . They have short and dense fur that is primarily brown-gray with patches of white at their shoulders and back, and their underside is more of a cream or light gray color. Monitos del monte also have distinct black rings around their eyes. Their small furred ears are well-rounded and their rostrums are short. The head to body length is around , and their tail length is between . Their tails are somewhat prehensile and mostly furred with the exception of of the underside. The naked underside of their tails may contribute to increasing friction when the mammal is on a tree. The base of their tails also functions as a fat storage organ which they use during winter
hibernation
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
. In a week, Monitos del monte can store enough fat to double their body size.
;Sexual dimorphism
At the end of the summer, female Monitos del monte tend to be larger and heavier than males. The tails of the sexes also vary in size during this time; females have a thicker tail, which is where they store fat; the difference suggests that females need more energy than males during hibernation. The sexual dimorphism is only seen during this time and not year-round.
Reproduction
Monitos del monte have a monogamous mating system. The females have well-formed, fur-lined
pouch containing four teats. They normally reproduce in the spring once a year and can have a litter size varying from one to five. They can feed a maximum of four offspring, so if there are five young, one will not survive. When the young are mature enough to leave the pouch, approximately five months, they are nursed in a distinctive
nest
A nest is a structure built for certain animals to hold eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of organic materia ...
. They are then carried on the mother's back. The young remain in association with the mother after weaning. Males and females both reach sexual maturity after two years.
[
]
Habits
The monito del monte is adapted to arboreal
Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...
life; its tail and paws are prehensile
Prehensility is the quality of an appendage or organ (anatomy), organ that has Adaptation (biology), adapted for grasping or holding. The word is derived from the Latin term ''prehendere'', meaning "to grasp". The ability to grasp is likely der ...
. It is largely nocturnal
Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite.
Nocturnal creatures generally have highly developed sens ...
and, depending on the ambient and internal temperature, and on the availability of food, it spends much of the day in a state of torpor
Torpor is a state of decreased physiological activity in an animal, usually marked by a reduced body temperature and metabolic rate. Torpor enables animals to survive periods of reduced food availability. The term "torpor" can refer to the time ...
. Such behaviour enables it to survive periods of extreme weather and food shortage, conserving energy instead of foraging to no effect.
The animal covers its nest with moss for concealment, and for insulation and protection from bad weather.
Diet
Monitos del monte are primarily insectivores. They eat insects and other invertebrates they find on the branches of trees and cracks in bark, but during the summer they eat large quantities of fruit, especially mistletoe fruit.
;Seed-dispersing role
A study performed in the temperate forests of southern Argentina showed a mutualistic seed dispersal relationship between ''D. gliroides'' and ''Tristerix
''Tristerix'' is a genus of mistletoe in the family Loranthaceae, native to the Andes, ranging from Colombia and Ecuador to Chile and Argentina. They are woody perennials usually occurring as aerial parasites, are pollinated by hummingbirds and ...
corymbosus'', also known as the loranthacous mistletoe
Mistletoe is the common name for obligate hemiparasitic plants in the order Santalales. They are attached to their host tree or shrub by a structure called the haustorium, through which they extract water and nutrients from the host plant.
...
. The monito del monte is the sole dispersal agent for this plant, and without it the plant would likely become extinct. The monito del monte eats the fruit of ''T. corymbosus'', and germination takes place in the gut. Scientists speculate that the coevolution of these two species could have begun 60–70 million years ago.
Conservation
For the past few years the number of ''Dromiciops'' has declined, and the species is now classified as "near threatened". Many factors contribute to the decline:
The monito del monte is not the only organism which will be affected if it becomes endangered. ''Dromiciops'' illustrate parasite-host specificity with the tick '' Ixodes neuquenensis''. This tick can only be found on the monito del monte, so it depends on the survival of this nearly endangered mammal. '' T. corymbosus'' also depends on the survival of this species, because without the seed dispersal agency of the monito del monte, it would not be able to reproduce.
Currently, there are minimal conservation efforts. Ecological studies are being conducted in the Chiloé Island
Chiloé Island ( es, Isla de Chiloé, , ) also known as Greater Island of Chiloé (''Isla Grande de Chiloé''), is the largest island of the Chiloé Archipelago off the west coast of Chile, in the Pacific Ocean. The island is located in southern ...
that might help future conservation efforts. ''Dromiciops'' has been found in the Los Ruiles National Reserve and the Valdivian Coastal Reserve, which are protected areas in Chile and the Nothofagus forest of Parque Nacional Los Alerces, Chubut, Southern Argentina.
References
Sources
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{{Taxonbar, from=Q691991
Microbiotheriidae
Mammals described in 1894
EDGE species
Marsupials of South America
Marsupials of Argentina
Mammals of Patagonia
Mammals of the Andes
Marsupials of Chile
Taxa named by Oldfield Thomas