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Neusticomys monticolusmontane fish-eating rat

By Adam Glanzman

Geographic Range

Neusticomys monticolus is found in the Andes mountains of west Columbia and northern Ecuador, in particular in the Cordillera Central and Occidental mountain ranges of Columbia. (Gómez-Laverde and Delgado, 2010; Packer and Lee, Jr., 2007; Voss, 1988)

Habitat

Neusticomys monticolus is often found in heavily wooded areas along streams and small rivulets. These streams often run through constricted ravines that are tributaries to bigger watercourses and eventual rivers. Neusticomys monticolus is often found near small waterfalls around 2m in height and prefers riverine habitat covered by roots, cobbles, moss-covered rocks, gravel, and coarse sand. It has also been found in marsh-like areas surrounded by shrubs and shrub-like plants. This species commonly occupies elevations ranging from 1,800 to 2,777 m. High elevation populations tend to live along fast-flowing streams compared to low-elevation populations. Neusticomys monticolus lives sympatrically with other ichthyomyine species. (E. Lee, Jr., et al., 2006; Packer and Lee, Jr., 2007; Voss, 1988)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    1,800 to 3,754 m
    to ft
  • Average elevation
    2,777 m
    ft

Physical Description

Neusticomys monticolus has thick, blackish-gray pelage on its dorsum and slightly paler pelage on its venter. Subtle black guard hairs sporadically occur along the dorsum. Neusticomys monticolus has relatively large ears, ranging from 9 to 10 mm in length. Its tail ranges from 82 to 111 mm and is covered in gray-black fur. Their vibrissae range in color from black to white. Silvery white hairs occur on the digits of both the forefoot and hindfoot, which are used to distinguish N. monticolus from other ichthyomyines. Slight webbing is present between the 1st interphalangeal joints on the hindfeet. Interphalangeal webbing and thick pelage, are specializations for swimming. The pelage does not change in color or texture as the species matures in age. Sexual dimorphism has not been documented in this species. (Anthony, 1921; E. Lee, Jr., et al., 2006; Ochoa G. and Pascual, 1991; Packer and Lee, Jr., 2007; Voss, 1988)

  • Average mass
    40 g
    1.41 oz
  • Range length
    192 to 223 mm
    7.56 to 8.78 in
  • Average length
    208.3 mm
    8.20 in

Reproduction

The mating system of Neusticomys monticolus or its ichthyomyine relatives has not been documented.

Little information is available regarding the reproductive behavior of Neusticomys monticolus. It is suspected that individuals breed during the end of the dry season and beginning of the wet season, which roughly spans the months of May and June. Females give birth 1 to 2 offspring per litter. (Packer and Lee, Jr., 2007; Voss, 1988)

  • Breeding season
    May through June.
  • Range number of offspring
    1 to 2

There is no information available regarding parental care in Neusticomys monticolus. As mammals, however, females gestate babies internally and nurse newborn young until weaning.

  • Parental Investment
  • altricial
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female

Lifespan/Longevity

There is no information available regarding the life span of Neusticomys monticolus.

Behavior

There is little information available regarding the general behavior of Neusticomys monticolus. They are nocturnal and crepuscular, feeding from dusk to dawn. Neusticomys monticolus is primarily terrestrial and semi-natorial. Of all ichthyomyine species, N. monticolus is one of the least specialized for swimming. This species is solitary and is only social during breeding season. (Gómez-Laverde and Delgado, 2010; Packer and Lee, Jr., 2007; Voss, 1988)

Home Range

There is no information available regarding the home range of Neusticomys monticolus. (Voss, 1988)

Communication and Perception

The optic nerve of ichthyomyine species is comparably smaller than that of other muroid tribes. Thus, it is likely that Neusticomys monticolus greatly depends on senses other than sight. It has relatively large ears, suggesting well-developed hearing, and long vibrissae suggest a dependence on haptic perception. Neusticomys monticolus has a set of well-developed planter pads on the hind and fore feet, which may be important in haptic perception. (Voss, 1988)

Food Habits

Neusticomys monticolus is an opportunistic feeder and forages on that which is immediately and readily available. Neusticomys monticolus is primarily insectivorous, feeding on insects and arachnids including beetles, flies, mayflies, stoneflies, caddisflies, moths and butterflies, and spiders. Although stomach content analysis in N. monticolus shows evidence for folivory, ingestion of plant material in this species is probably rare. (Gómez-Laverde and Delgado, 2010; Packer and Lee, Jr., 2007; Percequillo, et al., 2005; Voss, 1988)

  • Animal Foods
  • insects
  • terrestrial non-insect arthropods
  • aquatic or marine worms
  • aquatic crustaceans
  • Plant Foods
  • leaves

Predation

There is limited information regarding major predators of Neusticomys monticolus. Remains of N. monticolus have been discovered in the scat of crab-eating foxes. Their coloration likely helps camouflage them from potential predators. (Delgado-V, 2009)

Ecosystem Roles

Neusticomys monticolus is primarily insectivorous and may help control insect pest populations throughout their geographic range. They are also prey for crab-eating foxes and probably a number of other carnivorous mammals, birds, and snakes. Neusticomys monticolus is generally uncommon and likely has little impact on its local environment. (Gómez-Laverde and Delgado, 2010; Packer and Lee, Jr., 2007; Voss, 1988)

Economic Importance for Humans: Positive

There are no known positive effects of Neusticomys monticolus on humans.

Economic Importance for Humans: Negative

There are no known adverse effects of Neusticomys monticolus on humans.

Conservation Status

Neusticomys monticolus is widely distributed and abundant throughout its geographic range and is classified as a species of "least concern" on the IUCN's Red List of Threatened Species. In addition, much of the geographic range of N. monticolus is located throughout protected national forestland in Ecuador and Columbia. Deforestation is a potential threat, however this has not yet become a major cause for concern. (Gómez-Laverde and Delgado, 2010)

Contributors

Adam Glanzman (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff.

Glossary

Neotropical

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

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

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.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

endothermic

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.

female parental care

parental care is carried out by females

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

natatorial

specialized for swimming

native range

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

nocturnal

active during the night

rainforest

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.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

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

visual

uses sight to communicate

viviparous

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

References

Anthony, 1999. Fish Eating-Rats, or Aquatic Rats. Pp. 1414 in R Nowak, ed. Walker's Mammals of the World, Vol. Volume 2, 6th Edition. Baltimore and London: The Johns Hopkins University Press.

Anthony, H. 1921. Preliminary Reports on Ecuadorian Mammals. No. 1. American Museum Novitates, 59.9(86.6): 1-6.

Delgado-V, C. 2009. Non-volant mammals, Reserva San Sebastián-La Castellana, Valle de Aburrá, Antioquia, Colombia. Instituto de Biología, Universidad de Antioquia., 1: 1-4.

E. Lee, Jr., T., J. Packer, D. Alvarado-Serrano. 2006. Results of a Mammal Survey of the Tandayapa Valley, Ecuador. Occasional Papers, Number 250: 1-8.

Gómez-Laverde, M., C. Delgado. 2010. "Neusticomys monticolus" (On-line). Home Page The IUCN Red List of Threatened Species. Accessed April 07, 2011 at http://www.iucnredlist.org/apps/redlist/details/14740/0.

Ochoa G., J., S. Pascual. 1991. A New Species of Water Rat, Genus Neusticomys Anthony, from the Andes of Venezuela. Journal of Mammalogy, Vol. 72, No. 1: 97-103.

Packer, J., T. Lee, Jr.. 2007. Neusticomys monticolus. Mammalian Species, No. 805: 1-3.

Percequillo, A., A. Carmignotto,, M. Silva. 2005. A New Species of Neusticomys (Ichthyomyini, Sigmodontinae) from Central Brazilian Amazonia. Journal of Mammalogy, Vol. 86, No. 5: 873-880.

Voss, R. 1988. SYSTEMATICS AND ECOLOGY OF ICHTHYOMYINE RODENTS (MUROIDEA): PATTERNS OF MORPHOLOGICAL EVOLUTION IN A SMALL ADAPTIVE RADIATION. BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY, Volume 188, Article 2: 262-482.

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