Hyladelphys kalinowskiiKalinowski's mouse opossum

Geographic Range

Kalinowski’s mouse opossums (Hyladelphys kalinowskii) are known from a very limited number of specimens. These animals have been found in 13 locations in northern South America including those located in Peru, Guyana, French Guiana and Brazil. Their documented range is patchy, but this can likely be attributed to the difficulty associated with trapping and may not be reflective of their actual distribution. These animals can likely be found throughout the northern portions of the Amazon region. (Astua, 2006; Gardner, 2008; Oliveira, et al., 2011; Pires Costa and Patterson, 2008)


Kalinowski’s mouse opossums have been trapped very few times. The first individual was found near Cuzco, Peru at 890 meters in elevation, however, they have been found at elevations up to 1,000 m. They are found in lowland tropical, subtropical and montane evergreen forests of the Andes and the foothills of Peru. These animals have been trapped on palm fronds in swampy and well-drained primary forests and may be found near streams. (Gardner, 2008; Hershkovitz, 1992; Pires Costa and Patterson, 2008; Voss, et al., 2001)

  • Range elevation
    1,000 (high) m

Physical Description

Kalinowski’s mouse opossums are a recently described species. These animals were originally grouped with genus Gracilinanus, but were moved into their own monotypic genus in 2001. Currently, their placement within the family Didelphidae is under question. Certain morphological traits shown in this species, such as deciduous premolars and an even number of mammae are not typically seen in didelphids. Furthermore, what is currently described as Kalinowski’s mouse opossums may actually be several different species. Due to these factors, there is currently limited information available regarding Kalinowski’s mouse opossums and it may not be safe to assume that this species shares any behavioral traits with related species because its family affiliation is under question. (Astua, 2006; Gardner, 2008; Jansa and Voss, 2005; Pires Costa and Patterson, 2008; Voss, et al., 2001)

Kalinowski’s mouse opossums are small mouse-like marsupials, averaging 16.33 grams (ranging from 13 to 18 g). These animals have unpatterned gray to cinnamon brown dorsal pelage, including their sides and the outer portions of their legs. Their fur is smooth in texture, with short guard hairs. Ventrally, Kalinowski’s mouse opossums have cream to white pelage. Likewise, their ankles, wrists and throat are whitish to orange. Their head to body length averages 82.67 mm (ranging from 76 to 91 mm), excluding their tail, which averages 110.17 mm (ranging from 102 to 117 mm). Their largely naked, scaly tail is pale brown and does not have a furry base. Their faces are characterized by a very short rostrum and a wide skull. The fur on their cheeks is white and they have a large black mask that travels across their face to each ear. The fur between their large eyes is pale orange. These animals have whiskers on their chin and throat, as well as primarily black whiskers on their face. Their mostly naked ears are very large, they average 18 mm (ranging 15 to 19 mm) and are large enough to fully cover their eyes if placed on their face. Their hindfeet average 14.67 mm (ranging from 13 to 16 mm) and have long recurved claws. Kalinowski’s mouse opossums have a weakly dilambdodont tooth cusp pattern, with small molars. These animals differ from other didelphids due to their premolar milk teeth. Likewise, Kalinowski’s mouse opossums have 4 mammae, unlike other didelphids, which have an odd number of mammae. (Astua, 2006; Gardner, 2008; Hershkovitz, 1992; Jansa and Voss, 2005; Voss, et al., 2001)

  • Range mass
    13 to 18 g
    0.46 to 0.63 oz
  • Average mass
    16.33 g
    0.58 oz
  • Range length
    178 to 208 mm
    7.01 to 8.19 in


There is currently no information available regarding the mating systems of Kalinowski’s mouse opossums; however, most other didelphids maintain a polygynous mating system. (Fernandes, et al., 2010)

There is currently no information available regarding the reproductive behavior of Kalinowski’s mouse opossums; however, most didelphids have extremely short gestation periods with exceptionally small, altricial young. (O'Connell, 2006)

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

There is currently very little information available regarding the parental investment of Kalinowski’s mouse opossums. These animals do not have pouches and possess 4 mammae. Young of this species have deciduous premolar milk teeth. (Jansa and Voss, 2005; Voss, et al., 2001)


There is currently no information available regarding the lifespan of Kalinowski’s mouse opossums specifically, however, most didelphids are short-lived, typically surviving 1 to 2 years maximum. (Cooper, et al., 2009; Martins, et al., 2006; Pires Costa and Patterson, 2008)


Very little is known about the behavior of Kalinowski’s mouse opossums. Their elusive nature is facilitated by their arboreal and nocturnal habits, as well as their small body size. They are believed to have a large and stable population, but they are extremely difficult to locate and study. (Astua, 2006; Pires Costa and Patterson, 2008; Voss, et al., 2001)

Home Range

There is currently no information regarding the home range size of Kalinowski’s mouse opossums.

Communication and Perception

There is currently very little information available regarding the communication and perception of Kalinowski’s mouse opossums. These animals have vibrissae on their faces, chins and throats, which likely helps them navigate in the dark due to their nocturnal habits. They also possess very large eyes and ears. (Gardner, 2008; Pires Costa and Patterson, 2008; Voss, et al., 2001)

Food Habits

There is currently no information available regarding the feeding habits of Kalinowski’s mouse opossums.


There is currently no information available regarding the predation of Kalinowski’s mouse opossums. However, members of genus Gracilinanus, the genus that Kalinowski’s mouse opossums were once included in, have a number of documented predators. Members of genus Gracilinanus are found in much of the same range as Kalinowski’s mouse opossums and are arboreal. These animals are known to be preyed upon by owls, lizards and snakes. They are also eaten by coatis and white-tailed hawks. (Astua, 2006; Ferreira, et al., 2013; Granzinolli and Motta-Junior, 2006; Hershkovitz, 1992)

Ecosystem Roles

There is currently no information available about the ecosystem roles played by Kalinowski’s mouse opossums.

Economic Importance for Humans: Positive

There is currently no information available regarding any positive impacts of Kalinowski’s mouse opossum on human populations.

Economic Importance for Humans: Negative

There is currently no information available regarding any negative impacts of Kalinowski’s mouse opossum on human populations.

Conservation Status

Kalinowski’s mouse opossums are currently listed as a species of least concern according to the IUCN Red List of Threatened Species. Although these animals are very rarely seen, their population is believed to be rather large and they are thought to be very widespread. (Pires Costa and Patterson, 2008; Voss, et al., 2001)

Other Comments

Kalinowski’s mouse opossums were named for the man who found their holotype, Celestino Kalinowski. (Hershkovitz, 1992)


Leila Siciliano Martina (author), Animal Diversity Web Staff.



living in the southern part of the New World. In other words, Central and South America.

World Map


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.


uses touch to communicate


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.


Astua, D. 2006. Range extension and first Brazilian record of the rare Hyladelphys kalinowski (Hershkovitz, 1992) (Didelphimorphia, Didelphidae). Mammalia, 70: 174-176.

Cooper, C., P. Withers, A. Cruz-Neto. 2009. Metabolic ventilatory, and hygric physiology of the gracile mouse opossum (Gracilinanus agilis). Physiological and Biochemical Zoology, 82:2: 153-162.

Fernandes, F., L. Cruz, E. Martins, S. dos Reis. 2010. Growth and home range size of the gracile mouse opossum Gracilinanus microtarsus (Marsupialia: Didelphidae) in Brazilian cerrado. Journal of Tropical Ecology, 26: 185-192.

Ferreira, G., E. Nakano-Oliveira, G. Genaro, A. Lacerada-Caves. 2013. Diet of the coati: Nasua nasua (Carnivora: Procyonidae) in an area of woodland inserted in an urban environment in Brazil. Revista Chilena de Historia Natural, 86: 95-102.

Gardner, A. 2008. Genus Hyladelphys. Pp. 50 in A Gardner, ed. Mammals of South America: Marsupials, Xenarthrans, Shrews, and Bats, Vol. 1. Chicago: University of Chicago Press.

Granzinolli, M., J. Motta-Junior. 2006. Small mammal selection by the white-tailed hawk in southeastern Brazil. The Wilson Journal of Ornithology, 118:1: 91-98.

Hershkovitz, P. 1992. The South American gracile mouse opossums, genus Gracilinanus Gardner and Creighton, 1989 (Marmosidae, Marsupialia): A taxonomic review with notes on general morphology and relationships. Fieldiana: Zoology, 39: 1-56.

Jansa, S., R. Voss. 2005. Phylogenetic relationships of the marsupial genus Hyladelphys based on nuclear gene sequences and morphology. Journal of Mammalogy, 86: 853-865.

Martins, E., V. Bonato, C. da Silva, S. dos Reis. 2006. Partial semelparity in the Neotropical didelphidmarsupialGracilinanus microtarsus. Journal of Mammalogy, 87:5: 915-920.

O'Connell, M. 2006. American Opossums. Pp. 808-813 in D MacDonald, S Norris, eds. The Encyclopedia of Mammals, Vol. 1. London: The Brown Reference Group.

Oliveira, E., P. Villa Nova, F. Goin, L. Avilla. 2011. A new hyladelphinemarsupial (Didelphimorphia, Didelphidae) from cave deposits of northern Brazil. Zootaxa, 3041: 51-62.

Pires Costa, A., B. Patterson. 2008. "Hyladelphys kalinowskii" (On-line). IUCN Red List of Threatened Species. Accessed June 01, 2013 at www.iucnredlist.org.

Voss, R., D. Lunde, N. Simmons. 2001. The mammals of Paracou, French Guiana: A Neotropical lowland rainforest fauna. Part 2: Non-volant species. Bulletin of the American Museum of Natural History, 263: 1-236.