Dromiciops gliroides, Thomas, 1894

Russell A. Mittermeier & Don E. Wilson, 2015, Microbiotheriidae, Handbook of the Mammals of the World – Volume 5 Monotremes and Marsupials, Barcelona: Lynx Edicions, pp. 207-208 : 207-208

Monito del Monte

Dromiciops gliroides

French: Monito / German: Chiloe-Beutelratte / Spanish: Monito del monte

Other common names: Chilean Opossum, Colocolo Opossum

Taxonomy. Dromiciops gliroides Thomas, 1894 ,

“ Huite, N.E. Chiloe Island ,” Region de Biobio, Chile.

Two subspecies, australis from the mainland and gliroides from Chiloé Island, had been traditionally recognized, but subspecific differentiation is not reliably established. Monotypic.

Distribution. Mainland Chile (Maule, Bio Bio, LLa Araucania, Los Rios, Los Lagos) and adjacent Argentina (Neuquén, Rio Negro, Chubut), and on Chiloé I.

Descriptive notes. Head—body 8:3-13 cm, tail 9-13.2 cm; weight 16-32 g. Ears of the Monito del Monte are small, rounded, and covered with short hair. Body fur is silky, short, and very dense. Brown pigments dominate dorsal coloration. Hair on flanks and ventral side looks lighter with a yellow-brownish color. Tail is semi-prehensile and thicker proximally; it is covered with hair on dorsal and ventral sides. Conspicuous black hairs form a mask around eyes. A female Monito del Monte has a small pouch, with four nipples symmetrically located. Limb bones are proportionally shorter and more robust than Chilean species of Didelphidae , allowing slow, intense, and powerful movements.

Habitat. Mainly old-growth temperate rainforests of Nothofagus (southern beech) and Chusquea (evergreen bamboos) but occasionally selectively logged forest and shrubland. There is no evidence of Monitos del Monte in pastures, prairies, or agriculture habitats. They have been observed from coastal areas on Chiloé Island and in the Andes up to elevations of between 1400 m and 1800 m.

Food and Feeding. The Monito del Monte is omnivorous. Insects are the most common items in its diet, including larvae, pupae, and adult forms. Nesting birds and small rodents are sometimes part of its diet. A great variety of fleshy fruits are consumed, particularly in old-growth forests where the Monito del Monte disperses seeds of several epiphytes and vines. Dietary items change with the season and habitat. For example, Monitos del Monte have higher proportions of insects in their diets during spring, probably because of the need for additional protein during the breeding season. Frugivory of the Monito del Monte increases in summer, probably related to the need for higher sugar and fat accumulation in preparation for winter torpor. Fleshy fruits and arthropods are consumed most in old-growth forests and selectively logged forests, respectively, probably as a function of the abundance of these items in those habitats. Together, the buccal apparatus and the mucilaginous tongue of the Monito del Monte represent an effective alimentary mechanism to catch small invertebrates.

Breeding. The Monito del Monte has tipically one reproductive event per year in the spring, with 2—4 offspring carried in a pouch during early development, but a recent study suggests that a second reproductive period is possible in summer. In 2005, A. Munoz-Pedreros and colleagues described the reproductive cycle of the Monito del Monte from observations near La Picada, Chile. Mating occurred in late winter to early spring, and the intrauterine development period probably lasted for 3-4 weeks until the end of October. Female Monitos del Monte built spherical nests with leaves, mosses, and twigs that were located 1-2 m above ground in branches of dense vegetation; parturition probably occurred in early November; young seemed to remain within the pouch, firmly attached to nipples, for c.2 months (November-December); and young left the pouch for short exploratory excursions. This exploratory period from late December to January was marked by short rides on their mothers’ backs, increasing in frequency and duration as young acquired autonomy. Juveniles continued to suckle during this period, occupying the nest as a center of home range activities; eventually, maturingjuveniles accompanied their mothers during nightly rides by clinging to their backs for foraging and exploratory excursions while remaining in close proximity to each other. By the end of March, juvenile Monitos del Monte were autonomously free-ranging even though females’ pouches were still well developed with functional nipples, suggesting that juveniles were not totally independent of their mothers until the end of April.

Activity patterns. The Monito del Monte is an arboreal and nocturnal marsupial. Individuals have been captured in the wild mainly at 1-2-5 m above ground in tree branches and dense understories of forests and shrubland, rarely on ground. Daily and seasonal torpor are characteristics of the Monito del Monte. Laboratory studies show that daily fluctuations in body temperature are significantly higher during the night. The Monito del Monte can enter torpor and arouse spontaneously. Duration of torpor increases with decreasing ambient temperature. Seasonal torpor of the Monito del Monte is characterized by a reduction in all activities and by a decrease of cardiac rhythm from 230 beats/minute to less than 30 beats/minute. Torpor allows the Monito del Monte to use large amounts of stored energy when food availability is low, or when activity is difficult because of cold weather. Ambient temperatures probably are the most immediate determinant of torpor, followed by food (energy) availability.

Movements, Home range and Social organization. Monitos del Monte principally explore their surroundings with taste and smell. Home range can vary according to season and sex. Monitos del Monte principally move through primary and secondary forests and shrublands with dense understory. In forests on Chiloé Island, home ranges of Monitos del Monte are 0-12-0-35 ha, with those of males larger than those of females In contrast, home ranges of Monitos del Monte in Chilean mainland forests are 0-69-22 ha, but no differences have been observed between sexes. Social organization of the Monito del Monte is poorly known, but social behavior has been described related to communal nesting and nocturnal exploration of mothers and young.

Status and Conservation. Classified as Near Threatened on The IUCN Red List. Recent studies have demonstrated that the Monito del Monte is more abundant that it was thought to be. Moreover, mitochondrial genetic analyses have shown a moderate level of genetic diversity among populations across its distribution. Studies indicate that the Monito del Monte in the Chiloé Island does not form a genetically distinct population from those of the mainland, suggesting a recent history of geographical separation. These findings could be taken as an encouraging scenario for conservation of the Monito del Monte. Nevertheless, habitat fragmentation is a serious threat to populations of Monitos del Monte, and without attention to loss of suitable habitat, populations may reach critically low levels. It has been demonstrated that habitat fragmentation can produce negative effects on arboreal marsupials in relation to their parasite loads, and “patch crossing” by the Monito del Monte can be compromised. Negative effects of habitat fragmentation can involve boundary effects, increased number of small areas, and isolation of populations. Arboreal species of marsupials can be particularly affected because they need a tridimensional matrix in which to move. Temperate rainforests of South America have suffered drastic reductions in the last 500 years since the arrival of European conquerors/settlers. Some estimates for Chile suggest that the original area offorests have been reduced to less than one-third since then, principally affecting forests of southern beeches. Therefore, it is critical to allocate resources to analyze and understand effects of habitat fragmentation on demographic and genetic patterns in populations of Monitos del Monte. It is also crucial to conserve remnants of temperate rainforest and appropriately plan for future land use.

Bibliography. Amico & Aizen (2000), Amico & Nickrent (2009), Amico et al. (2009), Amrine-Madsen et al. (2003), Armesto, Manuschevich et al. (2010), Armesto, Villagran & Donoso (1994), Asher et al. (2004), Baker et al. (2004), Beck (2008), Bozinovic et al. (2004), Campos (1996), Celis-Diez et al. (2012), Chornogubsky & Kramarz (2012), Diaz & Teta (2008), Fonturbel (2010), Fonturbel, Candia et al. (2014), Fonturbel, Silva-Rodriguez et al. (2011), Franco, Contreras, Cortés et al. (2012), Franco, Contreras & Nespolo (2013), Garcia et al. (2009), Goin & Carlini (1995), Goin, Case et al. (1999), Goin, Tejedor et al. (2010), Goin, Zimicz et al. (2007), Greer (1989), Hershkovitz (1992b, 1999), Himes et al. (2008), Horovitz & Sanchez-Villagra (2003), Kelt & Martinez (1989), Kirsch, Dickerman et al. (1991), Kirsch, Lapointe & Springer (1997), Lobos et al. (2005), Mann (1955, 1978), Marshall (1978b, 1982), Martin (2007, 2010), Meserve et al. (1982), Munoz-Pedreros & Palma (2009), Munoz-Pedreros et al. (2005), Nespolo et al. (2010), Nilsson, Arnason et al. (2004), Nilsson, Churakov et al. (2010), Oliver (1946), Osgood (1943), Palma & Spotorno (1999), Patterson & Rogers (2007), Patterson et al. (1989), Phillips et al. (2006), Reig (1955), Rodriguez-Cabal, Aizen & Novaro (2007), Rodriguez-Cabal, Amico et al. (2008), Sanchez-Villagra et al. (2007), Simpson (1935), Spotorno et al. (1997), Springer et al. (1994), Szalay (1982a, 1982b).

Figures

Monito del Monte

Distribution. Mainland Chile (Maule, Bio Bio, LLa Araucania, Los Rios, Los Lagos) and adjacent Argentina (Neuquén, Rio Negro, Chubut), and on Chiloé I.