Java mouse-deer: Difference between revisions

Revision as of 11:28, 20 March 2015

Revision as of 16:00, 30 June 2015

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==Appearance and biology==

Mouse-deer possess a triangular-shaped head, arched back, and round body with elevated rear quarters. The thin, short legs which support the mouse-deer are about the diameter of a pencil. Although Java mouse-deer do not possess antlers or horns like regular deer, male Java mouse-deer have elongated, tusk-like upper canines which protrude downward from the upper jaw along the sides of their mouth. Males use these “tusks” to defend themselves and their mates against rivals.<ref name=superhero8>Nowak, R., J. Paradiso. 1983. Walker's Mammals of the World. Chicago: Johns Hopkins University Press.</ref> Females can be distinguished from males because they lack these prominent canines, and they are slightly smaller than the males.<ref name=eof5/> The average size of a Java mouse-deer ranges from 1–2&nbsp;{{Convert|1|-|2|kg}}, with females falling on the smaller end of this spectrum. Java mouse-deer can furthermore be distinguished by their lack of upper incisors. The coat coloration of the Java mouse-deer is reddish-brown with a white underside. Pale white spots or vertical markings are also present on the animal’s neck.<ref name=eof5/>

The height of the Java mouse-deer is {{Convert|30 centimeters (12 inches)|cm}} on average. With average lengths of {{Convert|45|cm|abbr centimeters= (18 inches)on}} and an average tail length of {{Convert|5|cm|abbr centimeters= (2 inches)on}}, the Java mouse-deer is the smallest extant [[artiodactyl]] (even-toed hoofed mammal).<ref name=eof5/> Java mouse-deer are [[endothermic]] and [[homoeothermic]], with an average basal metabolic rate of 4.883 W.<ref name=eof5/> Tragulus javanicus also possess the smallest [[erythrocytes]] of the mammalian species, and their erythrocytes are unique in that 12.8% of their erythrocytes have pits in them.<ref name=erythrocytes9>Fukuta, K., Kudo, H., & Jalaludin, S. (1996). Unique pits on the erythrocytes of the lesser mouse-deer, Tragulus javanicus. Journal of Anatomy, 189(1), 211-213. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1167845/</ref> Pitted erythrocytes are unique and have never been seen before physiologically or pathologically. Java mouse-deer are also considered the most primitive [[ruminants]], thus they provide the living link between non-ruminants and ruminant species.<ref name=animalrecs10>Carwardine, M., & London, E. (2007). Animal records. New York: Sterling</ref>

==Ecology==

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===Habitat===

The Java mouse-deer prefers habitats of higher elevations and the tropical forest regions of Java, although it does appear at lower elevations between 400–700 meters{{Convert|400|-|700|m}} above sea level.<ref name=eof5/><ref name=adw12>Strawder, N. (2000). ADW: Tragulus javanicus. ADW: Home. Retrieved from http://animaldiversity.ummz.umich.edu/accounts/Tragulus_javanicus/</ref> During the day, Java mouse-deer can be seen roaming in crown-gap areas with dense undergrowth of creeping bamboo, through which they make tunnels through the thick vegetation which lead to resting places and feeding areas.<ref name=superhero8/> At night, the Java mouse-deer moves to higher and drier ridge areas.<ref name=eof5/> It has been argued that Java mouse-deer are an “edge” species, favoring areas of dense vegetation along riverbanks.<ref name=eof5/> Additionally, Java mouse-deer have been found to be more prevalent in logged areas than in the more mature forests, and their densities tended to decrease proportionately as the logged forests matured.

==Behavior==

===Diet===

Java mouse-deer are primarily [[herbivores]], although in captivity they have been observed to eat insects as well as foliage. Their diet consists primarily of that which they find on the ground in the dense vegetation they inhabit, and they prefer the plants of the faster-growing gap species over the closed forest understory species, likely due to the increased richness of secondary protective compounds which the gap species provide.<ref name=eof5/> They are often classified as [[folivores]], eating primarily leaves, shrubs, shoots, buds, and fungi, in addition to fruits which have fallen from trees.<ref name=eof5/><ref name=superhero8/> The fruits which Java mouse-deer commonly consume range from {{Convert|1|-|5 grams|g}}, while the seeds range from {{Convert|0.01|-|0.5|g|abbr = gramson}}.<ref name=eof5/>

===Social behavior===

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Male Java mouse-deer are territorial, marking their territory and their mates with secretions from an intermandibular scent gland under their chin.<ref name=superhero8/> This territorial marking usually includes urinating or defecating to mark their area. To protect themselves and their mates or to defend their territory, mouse-deer slash rivals with their sharp, protruding canine “tusks.” It has also been observed that, when threatened, the Java mouse-deer will beat its hooves quickly against the ground, reaching speeds of up to 7 beats per second, creating a “drum roll” sound.<ref name=prothero14>Prothero, D. R., & Foss, S. E. (2007). The evolution of artiodactyls. Baltimore: Johns Hopkins University Press</ref>

The territories of ''Tragulus javanicus'' males and females have been observed to overlap considerably, yet individuals of the same sex do not share their territories.<ref name=eof5/> When giving birth, however, females tend to establish a new home range. Female Java mouse-deer have an estimated home range of {{Convert|4.3|ha|lk [[hectares]]= in}}, while males inhabit, on average, {{Convert|5.9 hectares|ha}}. Additionally, male Java mouse-deer, in nature, were observed to travel distances of {{Convert|519 meters|m}} daily on average, while females average {{Convert|574 meters|m}} daily.<ref name=eof5/>

==Reproduction==

Java mouse-deer are capable of breeding at any time during the year, and this has been observed during captivity.<ref name=eof5/><ref name=adw12 /> However, some sources have observed that the breeding season for the Java mouse-deer in nature occurs from November to December.<ref name=hayssen15>Hayssen, V., & Tienhoven, A. v. (1993). Asdell's patterns of mammalian reproduction: a compendium of species-specific data. Ithaca: Cornell University Press</ref> Additionally, female mouse-deer have the potential to be pregnant throughout most of their adult life, and they are capable of conceiving 85–155 minutes after giving birth.<ref name=adw12/> The Java mouse-deer’s gestation period usually lasts 4.5 months, or 144 days.<ref name=eof5/><ref name=adw12 /> Typical litters consist of a single fawn, which resembles a miniature adult, although the tusk-like incisors prevalent in males are not visible in the young mouse-deer.<ref name=eof5/> The average mass of a newborn fawn is {{Convert|370 grams|g}}, and these precocial young are capable of standing within 30 minutes after birth. Fawns are capable of eating solid food within two weeks, yet it takes around 12 weeks to completely wean the fawns.<ref name=superhero8/> On average, it takes the young, both male and female, 167 days (~5 months) to reach sexual maturity.<ref name=kingdon16>Kingdon, J. (1989). East African mammals : an atlas of evolution in Africa. London: Academic Press</ref> Mouse-deer have been observed to live up to 14 years in captivity, but their lifespan in nature is still an open question.<ref name=eof5/>

==Predators==

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==Conservation status==

Java mouse-deer is currently categorized as “Data Deficient” on the International Union for Conservation of Nature’s [[Red List]].<ref name=iucn /> This data deficiency is due to the inconclusiveness regarding the distinct separation of ''Tragulus'' species, in addition to the lack of information on ''Tragulus javanicus''. Even comparison of past observed numbers of Java mouse-deer with those presently observed does not greatly aid researchers because of the high likelihood of inaccuracy in past observations. Although listed as “Data Deficient,” it is highly probable that a decline in the numbers of Java mouse-deer is occurring, and upon further investigation of this issue, the Red List status of ''Tragulus javanicus'' could easily change to “Vulnerable”.<ref name=iucn /> Some conservation actions which have been implemented include legally protecting the species, which, although it has been in effect since 1931, makes no significant difference since hunting of Java mouse-deer still occurs.{{Citation needed|date = June 2015}} Additionally, some areas of Java which the Java mouse-deer frequents have been protected, yet enforcement of these regulations is still needed. One of the greatest conservation efforts needed is simply more information about the species: a more complete definition of its taxonomy, as well as more information on its habitat and behavior.

==Indonesian folklore==