The distinction between the sexes is not dramatic (Fig. 1) and there is often little difference even in size (Obst, 1988). Males may have longer thicker tails, a more posterior vent and a bulge on the anterior fifth vertebral scute (Morgan and Schaffer, 2001). Old males and some females may have a slightly concave plastron with little size dimorphism. Vocalization, primarily related to mating, occurs in both sexes. Males vocalize during courtship, mounting and copulation. Females limit calls to early stages of mating.
Figure 1 a. Female Manouria emys phayrei.
Figure 1. b. Male Manouria emys pharei.
Manouria emys is divided into 2 subspecies: M. e. phayrei (Burmese black mountain tortoise) and M. e. emys (Burmese brown mountain tortoise). The key difference between the two subspecies is found in the pectoral scutes. In M. e. phayrei the pectoral scutes normally meet at or near the midline (Wirot 1979; Ernst & Barbour 1989; Cox et al., 1998), while they are widely separated in M. e. emys.
Manouria emys phayrei, the northern subspecies, ranges from central and northern Thailand, Myanmar, Assam, and Bangladesh to India (Pritchard, 1979; Wirot, 1979; Das, 1985; Obst, 1983; Tikader & Sharma, 1985; Ernst & Barbour, 1989; Das, 1991; Iverson, 1992; Cox et al., 1998; Liat & Das, 1999; Iverson et al., 2001) (Fig. 2). In addition to a more northern range, it is larger (60 cm), has larger clutches (51), and is generally darker, with a dark brown, olive or black domed carapace.
Manouria e. emys has a more southerly range in southern Thailand, Malaysia, Sumatra, Borneo and some of the Indonesian Islands (Fig. 2). It is also (questionably) reported from Australia, China, Cambodia, Lao PDR and Vietnam (Gunther, 1864, Gray, 1870; Bourret 1941; Wu, 1943; Das, 1991; Jenkins 1995). Of these, the Australian “Murray River” specimen (Gunther, 1864) was acquired by the British Museum from Gould “with a series of skins of Kangaroos and other Australian mammalia and reptiles... (Gray, 1870)”. It was obviously mislabeled by the Museum or Gould. Wu (1943) described the species from a zooarchaeological specimen from in a Shang Dynasty site, a group that practiced plastromancy (divination by chelonian plastron). Bourret (1941) noted the origin of the specimen was Cholon (Chinatown in the former Saigon). Manouria e. emys is smaller (50 cm), has smaller clutches (30), and generally has a lighter yellowish brown flattened carapace. Sometimes the seams may be darker.
Hatchlings of both subspecies appear similar, differing primarily in color (Fig. 3 a&b) and pectoral scute arrangement (Fig. 3 c&d).
Figure 3. a. Hatchling Manouria emys phayrei.
Figure 3. b. Hatchling Manouria emys emys.
Figure 3. c. Plastron of a hatchling Manouria emys phayrei.
Figure 3. d. Plastron of a hatchling Manouria emys emys.
Differences become more pronounced during subsequent years when the carapace of M. e. phayrei develops a pronounced scute dimpling (Fig. 3 e), while those of M. e. emys remain unchanged. Pectoral scutes remain unchanged from hatching (Fig. 3 f).
Figure 3. e. A yearling Manouria emys phayrei.
Figure 3. f. Plastron of a hatchling Manouria emys phayrei.
Examinations of numerous possible intergrade specimens reveal M. e. phayrei-like dimpling (Fig. 3 g) with pectoral scute arrangement intermediate to both subspecies but sometimes closer to what would be expected in M. e. phayrei (Fig. 3 h). The majority of M. e. emys show no dimpling (Fig. 3 i) and have the more typical pectoral scute configuration (Fig. 3 j).
Figure 3. g. Carapace of a possible intergrade.
Figure 3. h. Plastron of a possible intergrade.
Figure 3. i. Carapace of a Manouria emys emys.
Figure 3. j. Plastron of a hatchling Manouria emys emys.
Only one published paper dealing with natural in-situ behavior was found (Lambert & Howes, 1994). During that study, the activity period of one female M. e. phayrei was examined using radiotelemetry for six months. During this time, she traveled less than 200 m through a series of clustered locations with sporadic longer movements through a 0.6 km2 area (Lambert & Howes, 1994; Liat & Das, 1999). Very little else has been recorded regarding activity periods and thermoregulation.
Materials and methods
The objective of this ongoing two-year study is to observe a group of juvenile M. e. phayrei under near natural conditions to study activity and behavior. Of particular interest was the response in activity level to temperature and humidity. These captive observations, while unable to completely approximate studies in their native range, serve to provide an analogous view until such studies can be conducted. At the study site in Jacksonville, Florida, temperature and precipitation were comparable to areas within the range of M. e. phayrei. Study habitat ranged from 1.5 m2 for hatchlings to 3 m2 for three year olds with two to three animals in each enclosure. Enclosures were provided with multiple hiding areas/shelters, piles of loose leaf-debris and a shallow drinking/soaking container. Study animals, ranging from one to three years of age, were acquired from captive breeding of wild caught stock. The diet was regularly varied and included a diverse mix of fruits, vegetables and fungi.
Activity levels appear to be directly correlated to time of day, precipitation and temperature. Typical M. e. phayrei bimodal activity periods (Fig. 4a) in morning and evening are clear with the morning activity period previously unreported. Cooler temperatures extend and warmer temperatures contract the activity cycles.
Within the temperature range of 13-32oC, maximum activity occurred more often during high humidity or precipitation (Fig. 4b). Below 13oC and above 32oC, activity decreased. Low humidity also induced inactivity.
A second very significant discovery was the use of thermostrategy - predetermined thermoregulatory behavior (Morgan & Schaffer, 2001). Manouria. e. phayrei spends cold evenings outside and consistently wakes up in a pool of warming sun. The method of location of this spot of early sun must somehow be based on thermoexperience – knowing where the warm area will appear.
The primitive nature and morphological traits of M. e. phayrei may account for, at least in part, some of the behaviors, particularly those of mesic habitat preference, as well as humidity dependent and bimodal activity patterns. Other problematic characters include complex activities, such as nest building and defense that are anything but primitive.
Although previous in-situ studies of adults have been conducted (McKeown et al., 1982), the published data forms no consensus. Some suggest activity in evening and night (Obst, 1988) while others indicate it in early afternoon (Lambert & Howes, 1994). Our observations indicate two activity periods: dawn and dusk.
Differing from normal chelonian thermoregulation, and previously unreported in the literature, M. e. phayrei utilizes thermostrategies during the colder months. Instead of burrowing or retreating to shelter, M. e. phayrei remains outside, and utilizing thermoexperience, awakens in a pool of sunshine. This is an advantageous strategy allowing animals outside to warm up faster and become active far earlier than those in the shelter, thus permitting a much longer period of daily activity.
The Asian turtle crisis has lent urgency to an adequate understanding of this species. With no reliable population density estimates and a drop in abundance, there has been no change in its listed status and conservation, despite growing concern. Failure of current land-use planning, and conservation practices, coupled with inconsistent protective legislation contribute to the decline of this species, to which protection, often simply means limited trade.
Behavioral observations presented here and elsewhere may facilitate understanding of M. e. phayrei’s natural history. This baseline knowledge may supplement conservation programs, arresting the downward trend of this species. Captive observations and breeding alone will not save them, but may provide, not only breeding stock for future repatriation, but the knowledge necessary to keep in-situ populations viable. This study has also revealed new data including: an anterior fifth vertebral scute bulge in males, bimodal activity periods, and thermostrategies/thermoexperience. In order to ensure the survival of Manouria emys in the wild, we need new and more complete in- and ex-situ studies. Land use planning, conservation practices and protective legislation needs to be re-examined more thoroughly in light of last year’s Asian Turtle Trade Proceedings (van Dijk et al., 2000).
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