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Manouria emysBrown Tortoise

By Vijay Virupannavar

Geographic Range

Manouria emys is native to southern and southeastern Asia, ranging from extreme eastern India (Assam) through, Bangladesh, and south and east through Myanmar, Thailand, Malaysia, and onto the islands of Sumatra and Borneo. Imported specimens have been found in Vietnam. (Moll, 1989)

Habitat

Brown tortoises are found in temperate, moist habitats that are influenced by monsoon rains. Moderate temperatures of 55 F to 85 F (13 to 29 degrees Celsius) are preferred. To survive, young Manouria emys need the temperature to be above 65 F (18 degrees Celsius). This species also prefers a humidity of around 60% to 100%. In addition, these tortoises never wander far from a water source, such as a pond. M. emys are typically found in highland tropical forests, and prefers cooler and moister conditions than other tortoise species. (McKeown, et al., 1991; Jacobsen and Tabaka, 2004)

Physical Description

Manouria emys is the largest tortoise inhabiting Asia. Several characteristics of its shell distinguish it from other species. The cervical scute in the shell of the brown tortoise is shorter and wider when compared to other south Asian tortoises. The brown tortoise also has divided supracaudal scutes, whereas other tortoises do not. It has many scales on its hind thighs, a domed carapace, slightly serrated posterior marginals, and varies in color from brown to black, depending upon the subspecies. There are two recognized subspecies: Manouria emys emys is commonly called the Asian brown tortoise, while M. e. phayrei is called the Burmese brown tortoise. The Burmese brown tortoise is larger (it can grow to 60 centimeters and weigh 37 kilograms) and is darker. The brown tortoise can grow to 50 centimeters and weigh 20 kilograms. Like all tortoises, Males tend to have longer, thicker tails than those of females and also have concave plastra (which functions to facilitate mating). (Moll, 1989)

  • Sexual Dimorphism
  • sexes shaped differently
  • Range mass
    20 to 37 kg
    44.05 to 81.50 lb
  • Range length
    50 to 60 cm
    19.69 to 23.62 in

Development

We have no information on development in this species.

Reproduction

Courtship in this species is more elaborate than in other tortoises, During courtship, males head-bob to communicate with prospective mates. The female typically does not bob her head in response during courting, though females do bob heads to communicate with each other and with males when not breeding. The two types of head bobbing are horizontal and elevated bobbing. Fixation is another courting behavior performed by males. Males fully extend their head and neck and keep it pointed towards the female as the female moves about. As in head-bobbing, the female does not fixate on the male. Trailing is a maneuver in which the male follows the female very closely behind. If the female slows down or stops, the male usually attempts to mount her. If she does not slow or stop, he resorts to biting her to get her to hold still as he mounts her. Both males and females vocalize while courting. The sounds are low, resembling groans and moans, and most often occur during the head-bobbing phase of courtship. Male vocalizations are typically longer in duration than female vocalizations. As with other tortoises, males vocalized during mating is well.

We don't have information on whether males or females in this species mate more than once per season, but it's likely that as with other tortoises, both males and females may have multiple mates, with males more frequently mating multiply. (McKeown, et al., 1991)

Reported clutch sizes range from 21 to 53 eggs, but these are all from captive females. Incubation time ranges from 63-84 days, also in captive situations with artificial incubation. We have no information on reproduction in this species in the wild. (McKeown, et al., 1991)

  • Range number of offspring
    23 to 51
  • Average number of offspring
    39
  • Range gestation period
    63 to 84 days

Unlike most tortoises, females of Manouria emys do invest in their offspring after they lay their eggs. For a week prior to laying her eggs, the female gathers up leaves and ground debris to make a mound into which she will deposit her clutch. Brown tortoises use their forelimbs to gather debris while other tortoises use the hind limbs to excavate nest sites. After she finishes laying, the mother tortoise covers her eggs with vegetation and litter, and remains at the next site, guarding her eggs and frequently piling more vegetation on them. If a potential predator approaches her nest, she first attempts to drive it away by pushing and even biting. If the predator is too quick or persistent, she will passively defend the eggs by crouching over them. This behavior is unique among chelonians, no other turtle or tortoise exhibits this high a level of parental care. (Alderton, 1988; McKeown, et al., 1991; Moll, 1989)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

The biggest limiting factor in lifespan seems to be predation, either by humans or from habitat destruction. (Moll, 1989)

  • Average lifespan
    Status: wild
    150 years
  • Average lifespan
    Status: captivity
    19.9 years
    AnAge

Behavior

Manouria emys moves very slowly, even when threatened. The species is most active during twilight, or during the day if the temperature is not too high. If the climate is too warm, brown tortoises may burrow into damp soil and leaf litter. They also are found soaking in pools and small streams.

Brown tortoises seem to have more complex vocalizations and other communications within their species than other tortoises do, but they are not known to be particularly social. Males engage in vocal disputes and shoving matches to discourage rivals from courting nearby females, and females defend their nest sites from other tortoises, but we have no additional information about sociality in this species. (McKeown, et al., 1991; Moll, 1989)

Communication and Perception

This species has more elaborate communication behaviors than other tortoises.

Head-bobbing seems to be a form of social and courtship communication. The two types of bobbing are horizontal bobbing and elevated bobbing. Bobbing is not specific to one sex or the other and can be used by an individual towards either sex. However, during courting by the male, the female does not normally reciprocate head bobbing. At other times, however, head bobbing was reciprocated. Head-bobbing is often accompanied with vocalization. (McKeown, et al., 1991)

"Fixation" is a sexually oriented behavior in which a male fully extends his head and neck and keeps it pointed towards the female as they move about. The female does not ever "fixate" on the male. Fixation seems to be an early part of courtship, whether or not the male is successful in courting her. (McKeown, et al., 1991)

Trailing is another courting maneuver in which the male follows the female from behind. When the female slows down or stops, the male attempts to mount her. However, if she does not slow or stop, the male resorts to biting her. He bites her nose or legs in an effort to get the female to hold still for mounting. (McKeown, et al., 1991)

Another manner of communication is vocalization. Males tend to have rhythmic grunts or bellows. Both males and females have mating calls that they use while head bobbing occurs. Typically the male has longer and more frequent calls when compared to the female. Other purposes of vocalization are not entirely known at this point. (McKeown, et al., 1991)

Food Habits

Brown tortoises are herbivores for the most part. Their diet typically consists of grasses, vegetables, leaves, and fruits. They have been known to eat other animals on occasion, most of which were small invertebrates and amphibians. (McKeown, et al., 1991; Moll, 1989; Jacobsen and Tabaka, 2004)

  • Animal Foods
  • amphibians
  • terrestrial worms
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit
  • Other Foods
  • fungus

Predation

This species relies on its strong shell for protection from predators. It's preference for twilight hours for activity, and its brownish color of it may also help avoid predators. Female protection and maintenance of the nest may help protect her offspring during their most vulnerable time of life. Though she cannot deter a vigorous egg-eater, simply by distracting predators and creating a disturbance she may discourage or confuse them. Her frequent nest-building may also help hide the scent of the eggs.

Currently humans are by far the most dangerous predator to this species. We have no specific information on the predators of M. emys, but it is likely that large predators, like tigers, canids, or bears, might attack tortoises. Many smaller predators like foxes and monitor lizards eat tortoise eggs, and predator birds will attack juvenile tortoises. (Alderton, 1988)

Ecosystem Roles

As an herbivore, M. emys helps in cleaning up leaves, fungi, and fruit that are on the forest floor. They do not have any commensal or mutual relationships that are known, and specific predators of the tortoise were not available for study. Fruit seeds are dispersed through the tortoise's feces. (Alderton, 1988; ; McKeown, et al., 1991; Moll, 1989)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Some people of Southeast Asia use M. emys as a food source and in medications. In addition, M. emys is a profitable animal in the international pet trade. (Moll, 1989)

Economic Importance for Humans: Negative

There are no known adverse affects of Manouria emys on humans.

Conservation Status

In several parts of Asia, brown are exploited for food and medicine. Habitat destruction is also a factor in their 'vulnerable' status. The pet trade is also a problem, as Brown tortoises are fairly valuable and sought-after animals. Over-consumption and habitat destruction have caused populations of this species to rapidly decline in many parts of its range. The species is considered Endangered by the International Union for the Conservation of Nature is listed in Appendix II of CITES. This is one of many species terrestrial and freshwater turtles and tortoises in Asia that it threatened by commerical over-consumption. (Moll, 1989)

Other Comments

Many tortoise experts believe that this species resembles the ancestors of tortoises more than other tortois species, and may be the oldest tortoise species that exists. They base this idea on details of its anatomy, its ecological preference for a humid climate, and other aspects of its behavior.

Contributors

David Armitage (editor), Animal Diversity Web, George Hammond (editor), Animal Diversity Web.

Vijay Virupannavar (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

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.

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

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

forest

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

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

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.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

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.

sedentary

remains in the same area

sexual

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

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Alderton, D. 1988. Turtles & Tortoises of the World. New York, New York: Facts on File Publications.

Jacobsen, G., C. Tabaka. 2004. "Burmese Mountain Tortoise - Manouria emys " (On-line). World Chelonian Trust: Conservation and Care. Accessed September 23, 2004 at http://www.chelonia.org/Articles/burmmtortoise.htm.

McKeown, S. 1990. Asian Brown Tortoise, Manouria emys . Tortuga Gazette, 33/6: 3-5. Accessed September 23, 2004 at http://www.tortoise.org/archives/manemys2.html.

McKeown, S., D. Meier, J. Juvik. 1991. The Management and Breeding of the Asian Forest Tortoise (Manouria emys) in Captivity. Proceedings of the First International Symposium on Turtles & Tortoises: Conservation and Captive Husbandry: 138-159. Accessed September 23, 2004 at http://www.tortoise.org/archives/manouria.html.

Moll, E. 1989. Conservation Biology of Tortoises. IUCN - The World Conservation Unit.

Shaffer, C., V. Morgan. 2000. Behavioral observations of captive juvenile Manouria emys phayrei with notes on degrees of intergradation with Manouria emys emys . Turtle and Tortoise Newsletter, 5: 2-6. Accessed September 23, 2004 at http://www.chelonian.org/ttn/archives/ttn5/pp2-6.shtml.

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