Kannabateomys amblyonyx

Geographic Range

Atlantic bamboo rats, Kannabateomys amblyonyx , are native to the southeastern and southern Atlantic Forest, in Brazil, eastern Paraguay and northeastern Argentina.

• Biogeographic Regions
• neotropical neotropical
  • native native

Habitat

Atlantic bamboo rats are found in moist tropical forests, particularly bamboo thickets located near water. They build arboreal nests in native giant climbing bamboo ( Guadua angustifoila ), as well as in introduced species of bamboo, such as several Phyllostachys spp. and Chinese bamboo ( Bambusa tuldoides ). Native Guadua stands are rare in southeastern and southern Brazil due to deforestation practices. However, with the introduction of Phyllostachys spp. and B. tuldoides , Atlantic bamboo rats are able to re-inhabit parts of their native range.

• Habitat Regions
• tropical tropical

• Terrestrial Biomes
• rainforest rainforest

Physical Description

Atlantic bamboo rats are large rodents, ranging in size from 230 to 347 cm long, with a long tail of 300 to 420 cm long. They weigh between 350 to 600 g. Their dorsal pelage is olive-green to brown-orange with orange ventral pelage and white patches on their throat and chest. They have a square-like snout, gray cheeks, long whiskers and white lips. Thick fur covers the base of their tail, which tapers to a small tuft of dark-brown distal hairs. They have four long digits, an elongated and broadened third and forth digit separated by a gap, and flat nails, which allow them to have a firm grip on bamboo culms. The dental formula for members of the family Echimayidae is 1/1 0/0 1/1 3/3 for a total of 20 teeth. Atlantic bamboo rats have flat-crowned cheek teeth and differ from other Dactylomys spp. by having narrow enamel ridges present on their upper cheek teeth, as well as an absence of a constricted palate. Atlantic bamboo rats are sexually dimorphic. Although coloration is similar between sexes, males are generally larger than females. However, a monogamous population inhabiting Itapuã State Park in southern Brazil showed no sexual dimorphism.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Direct confirmation of polygny in Atlantic bamboo rats has not been documented in the wild nor have any genetic analyses on allelic contribution from either parent been conducted in order to determine polygyny or polyandry. However, physical characteristics and social patterns associated with polygyny have been reported in Atlantic bamboo rats. For example, males are larger than females and have larger home ranges, which may overlap the home ranges of several females. Stallings et al. (1994) found that when numerous bamboo patches were located close together, males were able to obtain access to multiple females, suggesting polygyny. However, in areas with low population densities, females are restricted to small, widely-spaced home ranges, which decreases the probability of males to acquire more than one mate. Under these situations, Atlantic bamboo rats are observed to be monogamous, living in mating pairs, with no co-occurrences of same-sex adults in the same bamboo patch.

• Mating System
• monogamous monogamous
• polygynous polygynous

Very little is known on the general behavior of the Atlantic bamboo rat during reproduction. They breed year round, yielding between 1 and 3 young per liter, with an average of 1.7 young per litter. Olmos et al (1993) found a deceased 600 g female with two near-term fetuses, both weighing approximately 20% of the mother’s weight. This suggests that neonate Atlantic bamboo rats require large demands of food and energy from their mother.

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

In Itapuã State Park, Brazil, monogamous mated males showed direct parental behavior similar to that of females, including grooming, huddling, and food provisioning. Furthermore, both males and females performed indirect parental behavior, such as alarm calls and nest building. In the event of a death or disappearance to one of the parents, the surviving parent (male or female) remains with the young, indicating prolonged parental care. In patchy arboreal habitats, biparental care is advantageous for Atlantic bamboo rats, as it reduces the risks of young falling from trees and depredation when moving amongst exposed branches.

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

Lifespan/Longevity

The average lifespan of Atlantic bamboo rats has not been documented.

Behavior

Atlantic bamboo rates leave their resting sites just before sunset and return just before sunrise. However, they are not strictly nocturnal, as they have been observed feeding during the day. They construct large arboreal nests and are territorial. Atlantic bamboo rats are solitarily or may live in pairs.

• Key Behaviors
• arboreal arboreal
• scansorial
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• territorial territorial

Home Range

Atlantic bamboo rats are territorial, with home ranges extending up to 1000 m^2, with densities reaching 1.47 individuals per km2. Within these ranges, they use one or two sleeping sites that are situated along the perimeter and at opposite ends of their ranges. Home ranges are limited by neighboring territories of conspecifics; however, they may expand their territory opportunistically into ranges adjacent to their own. In high density bamboo clumps, male Atlantic bamboo rats have larger home ranges than females. In Poco das Antas Biological Reserve, Rio de Janeiro, Brazil, female Atlantic bamboo rats have an average home range size of 647.5 m^2, and males have an average home range size of 900.7 m^2. In addition, male home ranges may overlap with those of one or two females.

Communication and Perception

Atlantic bamboo rats use vocalizations to defend resources and warn conspecifics of potential threats. Often performing vocalizations after dark, they sit on bamboo culms and thrust their head forward with each call. They remain secluded amongst the bamboo leaves, rarely exposing their position. During alarm calls, they call once and run to an area of greater cover, and continue calling for several minutes. When conspecifics hear a call, they escape to areas with greater cover and counter-call.

• Communication Channels
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Atlantic bamboo rats are specialized herbivores, feeding on bamboo shoots, stems, and leaves. They are arboreal browsers and feed predominately at night. They also feed on the shoots of young Phyllostachys species, but appear to avoid feeding on Bambusa tuldoides .

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• wood, bark, or stems

Predation

Brown capuchins are thought to be potential predators of Atlantic bamboo rats. They have been observed foraging among bamboo stands and are known to eat rodents. When capuchins forage in thickets inhabited by Atlantic bamboo rats, rats quickly find shelter amongst the bases of bamboo clumps. After capuchins leave, rat carcasses with the head and thorax missing are often found at the base of bamboo stands. However, actual capture and feeding by brown capuchins on Atlantic bamboo rats has not been documented.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Atlantic bamboo rats are important seed dispersers of various bamboo species. In addition, the manner by which they feed on bamboo is thought to be beneficial to the overall health of bamboo stands in which they reside. They may also be an important food source for brown capuchins , and although it has not been documented, Atlantic bamboo rats are likely host to a number of endo- and ectoparasites as well.

• Ecosystem Impact
• disperses seeds

Economic Importance for Humans: Positive

Information regarding potential economic impacts of Atlantic bamboo rats on humans has not been documented.

Economic Importance for Humans: Negative

Information regarding potential negative economic impacts of Atlantic bamboo rats on humans has not been documented. However, bamboo rats and mole rats in the subamily Rhizomyinae are known to affect tapioca and sugarcane crops in Thailand.

Conservation Status

Atlantic bamboo rats are naturally rare; a study in Rio Grande do Sul State reports a density of 4.28 individuals per km^2. However, due to their wide distribution and large population, Atlantic bamboo rats are listed as "least concern" on IUCN Red List of Threatened Species. Atlantic bamboo rats are locally threatened in Minas Gerais State, Brazil due to habitat destruction largely due to logging.

Additional Links

Encyclopedia of Life

Contributors

Melissa cruz (author), University of Manitoba, Jane Waterman (editor), University of Manitoba, John Berini (editor), Animal Diversity Web Staff.

References

Catzeflis, F., J. Patton, A. Percequillo, C. Bonvicino, M. Weksler. 2008. "IUCN 2010. IUCN Red List of Threatened Species" (On-line). Kannabateomys amblyonyx. Accessed November 09, 2010 at http://www.iucnredlist.org .

Emmons, L. 1981. Morphological, ecological and behavioral adaptations for arboreal browsing in Dactylomys dactylinus. Journal of Mammology , 62(1): 183-189.

Emmons, L., F. Feer. 1990. Neotropical Rainforest Mammals, a field guide . Chicago: The University of Chicago Press.

Ims, R. 1987. Male spacing systems in microtine rodents. American Naturalise , 130: 475-484.

Lekagul, B., J. McNeely. 1977. Mammals of Thailand . Bangkok, Thailand: Association for the Conservation of Wildlife.

Nowak, R. 1991. Walker's mammals of the world, 5th ed, vol: II . Baltimore and London: The Johns Hopkins University Press.

Olmos, F., M. Galetti, M. Paschoal, S. Mendes. 1993. Habits of the Southern Bamboo Rat, Kannabateomys amblyonyx (Rodentia, Echimyidae) in Southeastern Brazil. Mammalia , 57: 325-355.

Silva, R., E. Vieira, P. Izar. 2008. Social monogamy and biparental care of the neotrpical Southern Bamboo Rat (Kannabateomys amblyonyx). Journal of Mammology , 89(6): 1464-1472.

Silva, R. 2005. Ecologia da Rato-da-Taquara (Kannabateomys amblyonyx) no Parque Estadual de Itapua.. Mastozoologia Neotropical , 12(1): 98-99.

Stallings, J., M. Cecilia, M. Kierulff, L. Silva. 1994. Use of space, and activity patterns of Brazilian Bamboo Rats (Kannabateomys amblyonyx) in exotic habitat. Journal of Tropical Ecology , 10: 431-438.