Tortuga Gazette 30(5): 1-5, May 1994

Manouria impressa (Günther 1882): A Summary of Known & Anecdotal Information

by William H. Espenshade and James Buskirk

Manouria impressa Photograph by William Rainey

This article was inspired by McMorris and Burns' 1975 paper on the impressed tortoise. They focused on the problem of "impressa disease", setting forth the frustrations and difficulties which continue to plague attempts to maintain the impressed tortoise in captivity. The goal of this paper is to share what is known of this species' natural history and to help assure the survival of impressed tortoises in captivity. Recent limited achievements in captive husbandry are summarized, as are observations made by Peter Paul van Dijk and local colleagues on M. impressa habitat in Thailand. As many works as possible dealing with M. impressa published since 1975 have been consulted in this synopsis.

The impressed tortoise, Manouria impressa, was first described as "Geoemyda impressa" by Günther in 1882. The type locality was given simply as "Siam" (Thailand). Research by Obst (1983) traces the origin of the type specimen (CL 225 mm) no further than the Bangkok pet trade. Gray, recognizing the uniqueness of the earlier described Asian brown tortoise M. emys (the closest relative of the impressed tortoise), erected the genus Manouria in 1852. For more detailed accounts of the nomenclatural history of modern tortoise species, see Bour (1980) and Crumly (1988).

Although similar in appearance to a half-grown specimen of Manouria emys, M. impressa is clearly distinct from either subspecies of Asian brown tortoise. Wirot (1979) states that this species does not exceed a carapace length of 28 cm, though Moll (1989) records 31 cm as a maximum. The impressed tortoise is more flattened than the Asian brown tortoise, with characteristically concave carapace scutes from which the common and scientific names are derived. Manouria e. emys has less pronounced carapacial scute concavity. The strongly serrated marginal scutes, and contiguous pectoral plates which always meet at midline are further important characteristics. A single, large conical spur is present on each thigh, in contrast to the cluster of such spurs in M. emys. One colloquial Vietnamese name for the impressed tortoise, rúa sen, translates literally as "three [tailed] tortoise." Males have a distinctive caudal spur clearly visible in Boulenger's 1903 illustration. The caudal spur is absent in M. emys.

The carapace of M. impressa is horn colored to dull orange, with dark, often confluent flecks near the edges of the carapacial scutes. The limbs, clad in large overlapping scales, and other extremities are very dark although the snout is pale, particularly in females. The pale yellow plastron also bears peripheral radiating dark markings in each plate. These contrasting markings fade with age, and large adults may be of a nearly uniform horn color. There are reports that impressed tortoises of any size from Malaysia, on the other hand, are rather drab and of a uniform brownish-yellow. Taylor (1970) considered this species the most handsome of all chelonians indigenous to Thailand, though his figure of a data-less Chulalongkorn Museum specimen showed a young tortoise with an unmarked carapace. Males are distinguished from females not only by the caudal spur and by their darker as opposed to yellowish head and neck, but also by a longer tail.

The geographical distribution of the impressed tortoise was known about as well sixty years ago as it is today. Smith (1931), using now dated geographical terminology, gives the range of this species as 'Burma (Myanmar) (Karenni Hills); Siam (Thailand); Annam (Langbian Plateau); Tonkin; the Malay Peninsula." M. impressa was first recorded from China in 1974 based on a specimen purchased from an animal dealer on Hainan Island. A specimen, almost certainly introduced, was found on the outskirts of Shaoyang in Hunan Province in 1986, and Ermi Zhao reported this species from extreme southern Yunnan Province (Buskirk, 1989). Moll (1989) shows 12 localities in Myanmar, Thailand, Vietnam, and Malaysia, whereas Iverson (1992) includes the Hainan specimen by showing a dot for Haikou--the largest city on the island--but omits other mainland Chinese localities. He does show question marks for western Yunnan and eastern Thailand, and provides an additional locality in extreme southeastern Myanmar.

The natural history of this tortoise is poorly known, but there is some consensus that it is an upland form. Smith (1931) says only that the species occurs "in the hills at considerable altitudes." Boulenger (1903) cites two specimens collected at "1000 feet to 2000 feet" from what is now Perak Province, Malaysia, and two others collected in Myanmar at 3200' and 4000' elevations. He quotes a field observation by Annandale and Robinson as follows: "The two specimens of Testudo pseudemys were taken on a jungle path at dusk, within a few yards of one another. When alarmed they drew in their heads, but when lifted from the ground became very vicious, hissing, stretching out their necks and attempting vigorously to bite, their whole demeanor differing from that of specimens of T. emys I have seen in captivity in the Malay Peninsula."

McMorris and Burns (1975) surmise from exporters' accounts that the "natural habitat for impressa seems to be fairly dry." Wirot (1979) claimed that this species inhabits "forests and mountainous areas," and feeds on "plants and bamboo shoots, and forages in dense undergrowths at an altitude of 700 to 2,000 feet. During the rainy season, it wanders around eating grass shoots and looking for a mate." As "grass" and "bamboo" are the same word in Thai, the exact foodstuff in question is uncertain; perhaps impressed tortoises consume both. Bourret (1939) reports the species as fairly common in a mountainous region of northern Vietnam. Weissinger (1987) reported the impressed tortoise in "inaccessible mountain forests and bamboo thickets" where it is active "only during the rainy season," a period generally not exceeding four months (Pearce and Smith, 1990).

More detailed habitat information is supplied by Nabhitabhata (1991). He concurs with McMorris and Burns (1975) in declaring the habitat to be "fairly dry and generally away from the water bodies, so this tortoise relies instead on dew or rain-drenched vegetation." The same author cites the altitude parameters as 700-2,000 meters, both considerably higher than those figures as reported in feet by Wirot (1979). In an area of broad-leaf evergreen forest in northern-northeastern Thailand visited by van Dijk (personal communication), the leaf litter substrate consisted of a complex mosaic of both wet but mostly dry areas on a flat-topped limestone mountain complex, with no running water available during the dry season (February). This area is reported as typical M. impressa habitat, and is far from "inaccessible" despite Weissinger's (1987) assertion. Montane broad-leaved evergreen forest, sometimes called hill evergreen, occurs between 1,500 and 2,000 m elevation in Thailand. It includes temperate zone trees such as laurels, oaks, and chestnuts, as well as moss, ferns, rhododendrons, and numerous epiphytes (Gray et al., 1991). The exact preferred microhabitat of M. impressa is not yet documented.

Detailed gross climatic information for Chiang Mai (sometimes written Chiengmai or Chingmai) is provided in table 1. This rapidly growing city at an elevation of approximately 2000 feet lies within the historical range of M. impressa and is the site for one locality record. Chiang Mai receives an average of 42" (105 cm) of annual rainfall. Other areas at higher elevation probably inhabited by M. impressa may receive nearly twice as much annual rainfall (Gray et al, 1991). Monthly precipitation in Chiang Mai reaches a maximum of nearly 25 cm (9.8") in September, a month preceded by three of limited sunshine owing to cloud cover and rain. Twelve to 20 days of rain (less than .04"/day) per month are recorded between May and September. Early morning average humidity, higher in other months, is not known to fall below 88% in the late dry season (March and April). Average daily high temperatures of 97°F (36°C) coincide with this same season. Midday relative humidity is highly variable. Overnight drops in temperature by as much as 15°C result in heavy pre-dawn condensation. The mildest weather, with greatest number of hours of sunshine, occurs as the rainy season tapers off in October and November. The lowest daily temperatures (56-59°F, 14-15°C) occur between December and February, following a sharp drop during November. Other species of land tortoise in the region (M. emys, Indotestudo elongata) occur at lower altitudes than those reported for M. impressa.

Weissinger (1987) echoes McMorris and Burns (1975) in documenting the delicate nature of the single specimen that he kept as a captive, and refers to a fellow German, M. Reimann, who also kept M. impressa. Their tortoises paced restlessly, indoors or out, and initially refused to eat. Weissinger's male tortoise developed severe stomatitis successfully treated with debridement and a topical antibiotic. Eventually, after a period of being force-fed, the tortoise consumed "three bananas per week." The ultimate captive longevity of this specimen is not known. McMorris and Burns (1975) list bananas, purple grapes, dates, pineapple-guavas, cucumber, romaine lettuce, wandering Jew, ivy, grass, and "fleshy green plants" as having been consumed by an unspecified number of captive impressed tortoises, all but a few of which died within a few months of having been purchased in Bangkok. Most of the impressed tortoises refused food entirely during their captivity.

Other reports of captive feeding experiences are varied. Reportedly, a specimen imported to the Midwest in the 1970s fed selectively, and only at daybreak, beneath a drizzle of simulated rain from an outdoor faucet. A 20-cm male which survived for ten months (1987-88) in the second author's care was observed feeding on only three occasions: once, exactly a month after acquisition, it took several bites from a growing Dracena plant, and the following day consumed about three leaves from a young spinach plant also growing in the outdoor enclosure. Months later it also consumed part of a growing Dracena leaf. This Thai specimen, an unexpected legal gift from a traveler to that country, appeared vigorous upon arrival in the United States and weighed 1402 g. It frequently drank, especially during real or simulated rain, and even attempted to copulate with a slightly smaller juvenile Manouria emys phayrei, the only other tortoise in the enclosure. The tortoise was treated empirically with both Flagyl and Tramizol, and its occasional stool was found to be free of parasites six months after this treatment. Despite prolonged fasting, the tortoise lost only about 100 g of mass before expiring in late April 1988.

In March or April of 1986, a Russian naturalist collected an adult female M. impressa in a driving rain as it walked along a mountain river-bank in central Vietnam, near the junction of Vietnam, Laos and Cambodia. The tortoise was taken to Russia and details of its maintenance there are sketchy. However, after refusing to feed for an unspecified period, this tortoise's feeding response was initially "turned on" by cabbage leaves scented with vanilla extract. Subsequently this tortoise, presently in the care of Ron Tremper in Texas, has become accustomed to a diet of tomatoes, cantaloupe, papaya, and bananas, supplemented with vitamins and minerals. Greens are refused. This tortoise has been in captivity with a variety of other tortoise species, mostly of larger size. It has had the run of a large, humid warehouse provided with numerous feeding, watering, and rest stations. Ambient temperatures in winter vary from 50-75°F and from 75-95°F in summer. This tortoise may represent the captive longevity record for the species, about seven years. Reports of "successful" captives indicate their discomfort with ambient temperatures in excess of 25°C (78°F) and their avoidance of strong light (Weissinger, 1987).

At Chulalongkorn University in Bangkok, a juvenile M. impressa (CL 15 cm) is maintained in good health on an exclusive diet of oyster mushrooms, which it consumes voraciously (van Dijk, personal communication). No other captive impressed tortoises in Thailand known to van Dijk have thrived. However, this tortoise had seemed heat-stressed during a failure of the air conditioning unit in the room in which it was housed, burying itself beneath the water dish for the duration of the 32°C heat wave and has since died when there was a prolonged interruption in air conditioning. Van Dijk advocates offering captives "hard" and seedy fruits such as berries, figs, and a variety of raisins and currants, rather than soft fruits (e.g., bananas, papaya) which are absent from their natural habitat. He further suggests placing fresh or canned bamboo sprouts upright, as if growing, rather than expecting the tortoise to consume vegetation lying on the ground. Van Dijk speculates that impressed tortoises may be partially carnivorous, and may even consume feces of other animals, but does not advocate this practice for captives.

There is a reliable report of a private individual in San Francisco, California with a healthy adult pair of M. impressa which have survived several years, but this man has not communicated with fellow tortoise keepers since initial contact, years ago. Of five impressed tortoises recently (7/93) imported into northern California, two adults are faring poorly and one died after a quick decline, but both juveniles "will eat anything put in front of them" (Roper, personal communication). These tortoises initially had been subjected to unpredictable environmental changes; that two are doing well, and all in the company of other tortoise species, is all the more impressive. Less fortunate was the fate of two female impressed tortoises recently kept by a herpetologist elsewhere in Fresno, California. Both refused all foods offered and were force-fed every few days. The tortoises received expert veterinary care. The deaths of both specimens after a few weeks were attributed to pre-existing conditions: in one case, to a lower respiratory tract infection, while in the other the caecum had been perforated by a large hardwood thorn. Both tortoises contained mature eggs which were surgically removed at the time of death for artificial incubation. None of these eggs are reported to have hatched.

In light of the near-consensus on the difficulties of these tortoises in adjusting to captivity, first spelled out by McMorris and Burns, it seems tragic that their importation as pet trade animals is on the rise. Between 1986 and 1990, 1,634 M. impressa were legally exported, mostly from Malaysia and Thailand, according to CITES documents. The "Russian" specimen appears in the 1989 column of the CITES table, as do, curiously, 20 specimens exported from Tanzania in 1986. In 1990, the latest year for which statistics are available, the number of legally exported impressed tortoises (706) was more than double the previous high figure of 312 for 1988. Thailand banned the legal export of M. impressa in February 1992. Within their range, impressed tortoises are consumed by local inhabitants as authenticated by a PBS videotaped documentary, narrated by George Schaller, on wildlife exploitation in southern China (ca. 1990), a private videotape from 1992 showing 2 live adult tortoises offered for sale in a Hanoi food market, and extensive documentation by van Dijk in protected areas of western Thailand. This species is so heavily exploited in and exported from Myanmar, which is not a CITES signatory, that in northern Thailand it is popularly referred to as the "Burmese tortoise." Wherever impressed tortoises are consumed, the plastron is generally used for Chinese traditional medicine, and is often the only portion of these tortoises seen by biologists. Even protected habitats in Thailand may be subject to poaching, and the rapidity of habitat destruction and impact of war elsewhere in the region lend little optimism for the long-term survival of this delicate species. The impressed tortoise may vanish before its life cycle and ecological importance are known.

References

Boulenger, G. A. 1889. Catalogue of the Chelonians, Rhynchocephalians, and Crocodiles in the British Museum (Natural History). Taylor and Francis, London.
Boulenger, G. A. 1903. Report on the batrachians and reptiles. pp. 131-176. In: N. Annandale & H. C. Robinson (eds.). Fasciculii Malayensis, anthropological and zoological results of an expedition to Perak and the Siamese Malay States, 1901-1902, Undertaken by Annandale, N. & H. C. Robinson. Vol. 1, Zoology. Univ. Press, Liverpool.
Bour, R. 1980. Essai sur la taxinomie des Testudinidae actuels (Reptilia, Chelonii). Bull. Mus. Natl. Hist. Natur. Paris (4)A(2):541-546.
Bourret, R. 1939. Notes herpétologiques sur l'Indochine française, XVIII. Reptiles et batraciens reçus au Laboratoire des Sciences Naturelles de l'Université au cours de l'année 1939. Descriptions de quatre espèces et d'une variété nouvelles. Bull. Gen. Instr. Publ. Hanoi 1939(4):5-39.
Buskirk, J. 1989. New locality records for Chinese non-marine chelonians. Chinese Herpetol. Res. 2:65-68.
Crumly, C.R. 1988. A nomenclatural history of tortoises (Family Testudinidae). Smithsonian Herpetological Information Service No. 75.
Gray, D., C. Piprell & M. Graham. 1991. National Parks of Thailand. Pp. 14, 46. Thai Wattana Panich, Bangkok.
Günther, A. 1882. Description of a new species of tortoise (Geoemyda impressa) from Siam. Proc. Zool. Soc. London, 343-346.
Iverson, J. 1992. A Revised Checklist with Distribution Maps of the Turtles of the World. Privately printed, Richmond, IN.
McMorris, J. R. & D. M. Burns. 1975. Notes on Geochelone impressa. Chelonia 2:5-7.
Moll, E. 1989. Manouria impressa Impressed tortoise. In: Swingland, I. & M.W. Klemens, eds. The Conservation Biology of Tortoises. IUCN SSC #5, Gland, Switzerland.
Nabhitabhata, J. 1991. "Impressed Tortoise Manouria impressa" pp. 200-201 In Endangered Species and Habitats of Thailand. Ecological Research Dept., Thai. Inst. Sci. Tech. Res., Bangkok.
Obst, F.-J. 1983. Beitrag zur Kenntnis der Landschildkroeten-Gattung Manouria GRAY, 1852. Zool. Abh. Staatl. Mus. Tierk. Dresden 38(15):247-256.
Obst, F.-J. 1986. Turtles, Tortoises and Terrapins. Druckerei Fortschritt Erfurt, Leipzig.
Pearce, E. A. & C. G. Smith. 1990. World Weather Guide. Random House.
Pritchard, P. C. H. 1979. Encyclopedia of Turtles. T.F.H. Publications, Neptune, NJ.
Smith, M. A. 1931. Fauna of British India. Vol 1, p 146. Taylor & Francis Ltd., London.
Taylor, E. H. 1970. The turtles and crocodiles of Thailand and adjacent waters. Univ. Kansas Sci. Bull. 49:87-179.
Weissinger, H. 1987. Haltung von Manouria impressa, Günter 1882 (Testudinidae) (Maintenance of Manouria impressa, Günter 1882). Elaphe 9:9-10.
Wirot, N. 1979. The Turtles of Thailand. Mitbhadung Press, Bangkok.

Acknowledgements

This work could not have been accomplished without the skilled assistance of Peter Paul van Dijk of Chulalongkorn University, Bangkok and University College Galway (Ireland). One of the very few western biologists to have gathered field data on tortoise species in Southeast Asia since the 1940s, van Dijk was assisted by the field observations of Mr. Thunya Chan-Ard and Mr. Niphone Sornakorn of the Wildlife Conservation Division, Royal Thai Forest Department. He is warmly thanked for his review of this manuscript and for his translations of the Obst paper (1983) as well as the 1987 work by the late Heinz Weissinger. Ron Roper (California), Ron Tremper (Texas), and Sean McKeown (California) were very helpful in providing details of their recent or ongoing captive husbandry of Manouria impressa. Ms. Amie Bräutigam of the IUCN Trade Specialist Group, Cambridge, U.K., provided very useful statistical data from CITES on the international trade in Testudinidae. Trinh Ly translated relevant dialogue between turtle vendors and customers recorded in the Hanoi video.

Questions on this article can be directed to the co-author William H. Espenshade.