Literaturdatenbank
Literaturdatenbank |
|
 |
|
Blanco, S., Behler, J. L., & Kostel, F. , Propagation of the batagurine turtles batagur baska and callagur borneoensis at the bronx zoo. Paper presented at Proc. 1st Int. Symp. Turtles & Tortoises: Conservation and captive husbandry. Orange, California.
Added by: Admin (23 Aug 2008 19:57:42 UTC) |
| Resource type: Proceedings Article BibTeX citation key: Blanco1990 View all bibliographic details  |
Categories: General Keywords: Batagur, Batagur baska, Batagur borneoensis, Carettochelyidae, Carettochelys, Carettochelys insculpta, Chelonia, Cheloniidae, Geoemydidae, Haltung = husbandry, Orlitia, Schildkröten = turtles + tortoises Creators: Behler, Blanco, Kostel Collection: Proc. 1st Int. Symp. Turtles & Tortoises: Conservation and captive husbandry. Orange, California |
Views: 8/1138
Views index: 19% Popularity index: 4.75% |
| Abstract |
|
The giant Asian river terrapin, or batagur (Batagur baska), and the closely related painted batagur (Callagur borneoensis) inhabit estuaries and tidal reaches of medium to large rivers throughout Southeast Asia. Both belong to monotypic genera and represent the largest emydid turtles, reaching a carapace length that may exceed 60 cm. Exploitation of adults, collection of highly prized eggs, and habitat destruction have greatly reduced the numbers of these turtles (IUCN Red Data Book, 1982). Batagur baska is listed on Appendix I (Endangered) of CITES. Ernst and Barbour (1989) summarize the characteristics, taxonomy, distribution, and life histories of these taxa, and Moll (1978, 1980) provides an excellent overview of their natural history. No captive breeding schemes of significance exist for these giant batagurines, and such activities have generally been viewed as impractical. The captive-breeding successes for Batagur and Callagur reported here, however, may influence that thinking, as it appears that this practice could play a vital role in recovery programs for these turtles. Breeding Groups. The Bronx Zoo's living turtle collection includes 9 (7 males, 2 females) B. baska and 8 (4 males, 4 females) C. borneoensis. Eight 4-year-old B. baska and 2 C. borneoensis of the same approximate age were acquired in May 1985. These juveniles were hatched from eggs collected in the wild and were received as a gift from the Department of Wildlife and National Parks, Peninsular Malaysia. An additional B. baska, a 30 kg female that has been in captivity for at least 30 years, was received from the Columbus Zoo in April 1987. Six wild-caught adult C. borneoensis subsequently joined the group. In November 1988, one male and 2 females were received from Dr. William McCord, a Hopewell Junction, New York, veterinarian, and another male and two females were rescued from a food market in Borneo by a turtle dealer and came to the zoo in July 1989. The sexes of individuals obtained as adults were readily determined by published morphological criteria and described sexual dichromatic characters (Moll, Matson, and Krehbiel, 1981). In July 1989, the 8 B. baska and 2 C. borneoensis obtained in 1985 (retrospectively judged to be 2-4 years old at acquisition, based on observed growth rates) had reached sexual maturity based on size and color-change observations during the previous breeding season. Pre-anal tail length was not an accurate sexing technique for these young adults. Sex was confirmed by finger-probing each turtle's cloaca for absence or presence of a penis. Most males quickly responded to the initial stimulation by extruding their penis, but some males required coaxing. Parenthetically, 9 out of 10 of the Batagur and Callagur juveniles received from Malaysia were males. The eggs from which they hatched had been incubated in captivity as part of a conservation program to return headstarted animals to nature. While temperature-determined sex has not yet been reported for these taxa, the authors speculate that incubation temperatures may be too low and causing a strongly biased male-to-female hatching ratio. Housing and Environment. Both batagur species are quartered in the multi-species Gharial River Exhibit in the Bronx Zoo's JungleWorld facility. The spacious (350 m²) enclosure is shared with 8 Indian gharial (Gavialis gangeticus), a pair of Bornean pond turtles (Orlitia borneoensis), 6 Fly River turtles (Carettochelys insculpta), and several fish species. The irregularly-shaped facility is approximately 42 m long and ranges from 6 m to 10.6 m in width. Three pools, each at a different elevation, occupy 70+ percent of the exhibit surface area. The top pool is the largest and holds about 100,000 l of water; collectively they contain 200,000 l of water. Pool 1 (top) is 1.2 m deep; pool 2, 1.5 m deep; and pool 3, 2 m deep. The top pool's elevation is about 2 m higher than the lowest pool. It receives recirculated 28° C water at 250-400 gpm. Water passes through a Stark Aquarium Systems sand filter which completely eliminates unicellular algae, which otherwise would seriously compromise water quality. Makeup water (overflow loss) at 5-10 gpm and 30° C cascades over a 5 m rock face into the upper pool. Water from pool 1 empties into pool 2 over a 1 m-high, 5 m wide-falls; pool 2 empties into pool 3 over a similar structure. Temperature of pool 2 and 3 water runs 0.5 to 1.0° C lower than the pool above it, depending on time-of-year and ambient air temperature which ranges from 23 to 31° C. After filtration, water passes through a heat exchange unit where lost calories are added and returned to the top pool. Pools are gently sloped and their surfaces are smooth concrete. Each has an 8" drain so the pools can be independently and very quickly dropped for cleaning with a pressure cleaner. Beach areas are bordered by a 1.5 m artificial mudbank barrier. Substrate is clay with a pulverized shale overburden. Heating pads are buried under the substrate of the largest beach adjacent to the upper pool to encourage nesting activity. The exhibit is naturally lighted via a glass-panelled roof. High-energy sodium vapor floodlights provide supplemental lighting if needed. Except for occasional evening use, they are not used to extend photoperiod. A fogging system, along with JungleWorld's lush tropical vegetation, serves to keep ambient humidity levels high. The exhibit is easily accessible to reptile keepers by a hidden door behind the rock face at the head of the top pool. Both the gharials and the turtles favor this pool, presumably because it holds the warmest water, is the largest body of water, and has a large submerged log and artificial grass beds which serve as shelters. If turtles need to be handled, the exhibit waters can be easily waded and turtles captured by hand or long-handled nets. The ominous-looking 3 m gharials are easily discouraged from conditioned feeding response advances by turning snouts away with a net handle. Diet. The batagurs are fed ad lib several times weekly and are offered a wide variety of greens, including kale, spinach, bok choy, and dandelion. Purina Turtle Chow and earthworms are broadcast on the water for the turtles and the fish. These items are very eagerly and rapidly consumed. Gharial are fed live trout several times weekly. Both batagur species will take warm-water stunned fish without hesitation; and they consume virtually all leaves that fall into the pools from surrounding planters. No vitamin or mineral additives are offered. Breeding Season and Reproduction. Wild Batagur and Callagur exhibit sexual and seasonal dichromatism, characteristics not exhibited by many chelonians (Moll, Matson, and Krehbiel, 1981). These dramatic events were witnessed in the Bronx Zoo's captive population of batagurs during a two-year study on the breeding behavior and activity patterns of these species in JungleWorld (Kostel, 1990). Change to breeding coloration occurred between October and February and extended into early spring for some individuals. During the course of the study, many courtship sequences were recorded. Some components witnessed (i.e., "head swaying" and "throat pumping") appear to be novel. These are elaborated upon in the study cited above. Despite numerous courtship observations, intromission was not witnessed. Nevertheless, on 2 February 1990, the Columbus Zoo B. baska began laying eggs in the top pool. She was quickly removed from the exhibit and placed in a large tub with water so that eggs could easily be salvaged. On exhibit, she had deposited 4 eggs. At 0845 hr, 150 units of oxytocin (Product manufacturer: Henry Shein, Anthony Products, Arcadia, CA 92006) were administered IM. By 1200 hr, she had laid 20 additional eggs. Nineteen of these were in good condition and were incubated. On 16 February, this female was radiographed and found to have 9 additional eggs. Oxytocin, given at the previous dose rate (5 IU/kg), stimulated depostion of the remaining eggs within two hours. Eggs were incubated in damp vermiculite (with a modest portion of peat moss) with a moisture content of 1:1 by weight. Two plastic boxes (approximately 40 l capacity) with tight-fitting lids were 1/3 filled with the incubation medium and eggs were placed without rotation in slight depressions in the substrate. Temperature in the room where incubation took place ranged from 26-30° C. The air was changed several times weekly at the beginning of incubation and daily during the later stages of development. After 80 days of incubation, on 21 April, the first captive-bred B. baska pipped its shell. By 28 April, five others had hatched. Unfortunately, 3 were deformed; two of these died shortly after hatching. Hatchling Care. The three normal individuals hatched at an average weight of 57.5 g with a carapace length of 62.2 mm. They remained in the incubator for 2 days to facilitate the absorbtion of their yolk sacs and accelerate body functions. The neonates were set up in a 114 l aquarium with 15 cm of water. It was decorated with plastic plants for hiding places, a gravel bottom, and large smooth rocks for basking. A 75-watt spot bulb was positioned over the basking rocks and provided heat. To satisfy unknown ultraviolet light requirements, a 20-watt blacklight fluorescent tube rested atop the aquarium. Ambient air in the Reptile House Nursery, where the animals were maintained, averaged 27° C. Water temperature ranged to 30° C during midday. A submersible filter was used to reduce detritus buildup. The hatchlings received a diet of mixed greens similar to the adult diet. Additionally, crickets, waxworms, mealworms, macerated newborn mice, chopped clams, and prawns were offered. One or more of these items were fed to them 4-5 times a week. Growth rates have been excellent. At 3 months of age, the young turtles' average weight was very nearly twice the hatching weight and average carapace length gain was 28 mm. Discussion. Pitifully little is known of the habits of Batagur and Callagur in the wild. The silt-laden rivers of Southeast Asia obscure movements and do not permit observations of breeding behavior or social interaction. The semi-natural setting of JungleWorld and clear waters of Gharial River have offered us a rare opportunity to view these taxa in an underwater setting, as they have never before been seen. This place too has been to their liking. They have prospered and they have reproduced. We've recorded the first captive breeding for Batagur and have found (albeit too late) a nest that contained fertile Callagur eggs. Although the current picture for these batagurines is not bright, the successes we've experienced have given us the spirit to continue our work. Very likely, JungleWorld bred animals will be the source of stock for other zoos and institutions concerned and eager to educate people about the plight of these turtles. And behavior studies may well provide further insight into the intricacies of their breeding biology and offer direction as to how they can best be maintained in captivity. Literature Cited Ernst, C.H. and Barbour, R.W. 1989. Turtles of the World. Smithsonian Institution Press, Washington, D.C. International Union for Conservation of Nature and Natural Resources. 1982. The (IUCN) Amphibia-Reptilia Red Data Book, Part I: Testudines, Crocodylia, Rhynchocephalia. (Compiled by B. Groombridge). IUCN, Gland, Switzerland. pp. 21-25; 2729. Kostel, F. 1990. Breeding behavior and activity patterns of the Asian freshwater terrapins Batagur baska and Callagur borneoensis. Unpubl. M.S. Thesis. Fordham University, Bronx, New York. Moll, E.O. 1978. Drumming along the Perak. Nat. Hist. 87(5):36-43. Moll, E.O. 1980. Natural history of the river terrapin, Batagur baska (Gray) in Malaysia. Malaysian J. Sci. 6(A):23-62. Moll, E.O., Matson, K.E. and Krehbiel, E.B. 1981. Sexual and seasonal dichromatism in the Asian river turtle, Callagur borneoensis. Herpetologica 37(4):181-194.
Added by: Admin |