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Hoplomys gymnurusarmored rat

By Patrick Cusick

Geographic Range

Hoplomys gymnurus is a Neotropical rodent found in Central and South America. It ranges from southern Honduras to northwestern Ecuador and is never found east of the Andes Mountains. (Grzimek, 2003)

Habitat

Throughout its geographic range, Hoplomys gymnurus is found in primary forests, disturbed forests, deserted farmlands, palm swamps, and lowland tropical evergreen forests. However, H. gymnurus is considered a habitat specialist because it is usualy found near wet habitats, such as wet lowland rainforests and stream sides. In fact it lives in the wettest forest habitat in the world, the pluvial rainforests of western Columbia. It prefers stream sides with steep slopes, rocky banks, plenty of fallen logs and a tall canopy. Hoplomys gymnurus limits competition with a closely related, sympatric species, Proechimys semispinosus, by being a habitat specialist living in wet microhabitats. (Eisenberg and Redford, 1999; Emmons, 1997; Grzimek, 2003; Reid, 1997; Tomblin and Adler, 1998)

Hoplomys gymnurus experiences two distinct seasons throughout its geographic range, a four month dry season from the middle or end of December to April and an eight month rainy season from May to December. The average rainfall is around 2,600 mm and 90% of the average precipitation falls during the rainy season. (Tomblin and Adler, 1998)

  • Range elevation
    30 to 800 m
    98.43 to 2624.67 ft

Physical Description

Hoplomys gymnurus has a long, narrow head with naked, erect ears. The hair on the dorsal part of the body is cinnamon-brown to dark brown. The anterior part of the body is covered with backward pointing spines. The spines are white at the base and black at the tip. The spines can be as long as 3 cm and as thick as 2 mm in diameter. The underside of the body and the inner parts of the legs and feet are white and there is usually a dark collar across the throat. The tail is naked and bicolored (dark on top and light colored below), but the tail is frequently lost in this species. Hoplomys is sometimes considered a subgenus of Proechimys, but H. gymnurus is much spinier than Proechimys. (Emmons, 1997; Grzimek, 2003)

Males are on average 38% larger than females. (Adler, et al., 1998; Grzimek, 2003; Adler, et al., 1998; Grzimek, 2003)

  • Sexual Dimorphism
  • male larger
  • Range mass
    0.220 to 0.820 kg
    0.48 to 1.81 lb
  • Range length
    22 to 32 cm
    8.66 to 12.60 in

Reproduction

Hoplomys gymnurus is considered to be monogamous because of its habitat specialization and small home range. A mating pair usually shares a burrow and territory. The mating system may be more promiscuous, however, in areas of abundant suitable habitat. (Adler, et al., 1998; Grzimek, 2003; Nowak, 1997; Reid, 1997)

In some parts of its geographic range, Hoplomys gymnurus breeds year round. It has a gestation period of 64 days and gives birth to one to three precocial young. Additional information on reproductive behavior for H. gymnurus is not available, but time of weaning is three to four weeks, and sexual maturity is reached at five months in the closely related species Proechimys semispinosus. In other parts of its range, H. gymnurus breeds seasonally. Pregnant females were found from February to July. This corresponds to the end of the dry season and beginning of the wet season. This also happens to be when food supply is at its peak. (Grzimek, 2003; Mendez, 1993; Nowak, 1997; Reid, 1997)

  • Breeding interval
    Armored rats breed year round if conditions allow, or if not, seasonally.
  • Breeding season
    If breeding is seasonal it is from February to July.
  • Range number of offspring
    1 to 3
  • Average number of offspring
    2.1
  • Average number of offspring
    2.1
    AnAge
  • Average gestation period
    64 days
  • Range weaning age
    21 to 28 days
  • Average age at sexual or reproductive maturity (female)
    5 months
  • Average age at sexual or reproductive maturity (male)
    5 months

Hoplomys gymnurus gives birth to precocial young. The only parental investment is providing shelter and protection in the burrow and supplying food. Weaning happens three to four weeks after birth and the young start to develop spines at four weeks old to defend themselves. (Grzimek, 2003)

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

Lifespan/Longevity

Little is known about the lifespan of Hoplomys gymnurus. Recaptures of wild individuals have occurred more than two years apart, but one researcher observed that H. gymnurus does not live more than 72 hours in captivity. (Adler, et al., 1998; Buchanan and Howell, 1965)

  • Average lifespan
    Status: wild
    2 years
  • Range lifespan
    Status: captivity
    7 (high) years
    AnAge

Behavior

Hoplomys gymnurus is nocturnal and terrestrial. It builds simple horizontal burrows in the sides of streams or uses abandoned burrows from other animals. The burrow consists of a 1.5 to 2 meter long tunnel with an enlarged chamber at the end for nesting. The nest chamber is kept dry and is covered with vegetative matter. There is also a separate chamber for defecating. Members of this species spend most of the day in their burrows and come out at night to find food. They build elaborate pathways in the vegetation on the forest floor which they travel through. Individual H. gymnurus is reclusive and runs to its burrow when disturbed. It has a rabbit-like gait when running and can jump 22 cm in the air from a standing position. (Buchanan and Howell, 1965; Reid, 1997)

Home Range

The home range of Hoplomys gymnurus is usually small and centered around its burrow. Its home range size also depends on the amount of microhabitat available. Haplomys gymnurus cannot tolerate dry areas and will not wander far from a stream or other wet environment. (Grzimek, 2003; Reid, 1997)

Communication and Perception

Hoplomys gymnurus can emit a loud “whee-unk” sound with considerable force when confronted by another animal. The function of this vocalization is not known. (Buchanan and Howell, 1965; Eisenberg and Redford, 1999)

Food Habits

Hoplomys gymnurus is primarily a frugivore, but it also includes some insects in its diet. Most insects consumed are of the orders Coleoptera and Orthoptera, and soft seeds, bananas, wild figs, avocadoes, mangoes, and other fruits make up the majority of its diet. Fruit is most abundant at the end of the dry season and the beginning of the wet season. Haplomys gymnurus caches some foods in its burrow. (Eisenberg and Redford, 1999; Mendez, 1993; Reid, 1997; Tomblin and Adler, 1998)

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit

Predation

Some key predators of Hoplomys gymnurus are ocelots, jaguarundis, bushmasters, and other snakes. (Grzimek, 2003)

The spines of H. gymnurus are a great defense mechanism against predators. In addition to the spines H. gymnurus can drop its tail to confuse or escape a predator. (Grzimek, 2003)

Ecosystem Roles

Hoplomys gymnurus is an important disperser of seeds of the palm Attalea butyraceae. It is also a reservoir for equine encephalitis and cutaneous leishmaniasis and is an intermediate host of Echinococcus oligarthrus. Equine encephalitis and cutaneous leishmaniansis are vectored by mosquitoes and sand flies, respectively. (Mendez, 1993; Wright and Duber, 2001)

Haplomys gymnurus also affects the ecosystem by changing habitats with its burrows and pathways. These actions can create microhabitats for smaller organisms. They also affect animals that they may steal burrows from. One excavation of a burrow that H. gymnurus was inhabiting revealed an extra cavity that was full of the eggs of an iguanid lizard. (Buchanan and Howell, 1965)

  • Ecosystem Impact
  • disperses seeds
  • creates habitat
Commensal/Parasitic Species
  • Echinococcus oligarthrus

Economic Importance for Humans: Positive

Some native people of Panama eat Hoplomys gymnurus. (Mendez, 1993)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

Hoplomys gymnurus is involved in the transmission of some human and animal diseases. Equine encephalitis has a mortality rate as high as 20% in humans and 80% in horses. Cutaneous leishmaniansis causes sores to develop on the skin of the infected person. Some of the sores can be very large and painful. Echinococcus oligarthrus is an extremely rare cause of human echinococcosis, but can be very dangerous to humans. Echinococcosis in humans causes cysts to form on internal organs like the liver and lungs. ("Parasitic Disease Information Factsheet: Leishmania Infection", 2000; "Parasites and Health: Echinococcosis", 2002; Derlet, 2002; Mendez, 1993)

Conservation Status

Hoplomys gymnurus is uncommon, but not rare throughout its geographic range. Conservation may become important because it is a habitat specialist. ("InfoNatura: Birds, mammals, and amphibians of Latin America", 2003)

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Patrick Cusick (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

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

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.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

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

food

A substance that provides both nutrients and energy to a living thing.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

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).

monogamous

Having one mate at a time.

motile

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.

nocturnal

active during the night

polygynous

having more than one female as a mate at one time

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

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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.

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born

References

NatureServe. 2003. "InfoNatura: Birds, mammals, and amphibians of Latin America" (On-line). Accessed March 30, 2004 at http://www.natureserve.org/infonatura/servlet/InfoNatura?searchName=Hoplomys+gymnurus.

CDC. 2002. "Parasites and Health: Echinococcosis" (On-line). Accessed March 31, 2004 at http://www.dpd.cdc.gov/dpdx/html/Echinococcosis.htm.

CDC. 2000. "Parasitic Disease Information Factsheet: Leishmania Infection" (On-line). Accessed April 01, 2004 at http://www.cdc.gov/ncidod/dpd/parasites/leishmania/factsht_leishmania.htm.

Adler, G., D. Tomblin, T. Lambert. 1998. Ecology of two species of echimyid rodents (Hoplomys gymnurus and Proechimys semispinosus) in central Panama.. Journal of Tropical Ecology, 14: 711-717.

Buchanan, O., T. Howell. 1965. Observations on the natural history of the thick-spined rat, Hoplomys gymnurus, in Nicaragua.. Annals and Magazine of Natural History, 13: 549-559.

Derlet, R. 2002. "CBRNE - Venezuelan Equine Encephalitis" (On-line). eMedicine. Accessed March 30, 2004 at http://www.emedicine.com/emerg/topic886.htm.

Eisenberg, J., K. Redford. 1999. Mammals of the Neotropics: The Central Neotropics, Vol. 3. Chicago: University of Chicago Press.

Emmons, L. 1997. Neotropical Rainforest Mammals: A Field Guide 2nd ed.. Chicago: University of Chicago Press.

Grzimek, B. 2003. Armored Rat. Pp. 453-454 in M Hutchins, N Schlager, D Olendorf, M McDade, eds. Grzimek's Animal Life Encyclopedia, Vol. Vol. 16, 2nd Ed. Edition. Farmington Hills, MI: Gale Group.

Mendez, E. 1993. Los Roedores De Panama. Panama City, Panama: Impresora Pacifico, S.A..

Nowak, R. 1997. "Armored rat, or thick-spined rat" (On-line). Walker's mammals of the world online 5.1. Accessed March 24, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/rodentia/rodentia.echimyidae.hoplomys.html.

Reid, F. 1997. Field Guide to Mammals of Central America and Southeast Mexico. UK: Oxford University Press.

Tomblin, D., G. Adler. 1998. Differences in habitat use between two morphologically similar tropical forest rodents.. Journal of Mammalogy, 79(3): 953-961.

Wright, S., H. Duber. 2001. Poachers and forest fragmentation alter seed dispersal, seed survival, and seedling recruitment in the palm Attalea butyraceae, with implications for tropical tree diversity.. Biotropica, 33(4): 583-595.

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