H U S B A N D R Y A N D RESEARCH

Notes on Indo-Australian varanids in captivity J A M E S M U R P H Y Supervisor of Reptiles, Dallas Zoo, Texas, USA

During the past few years a large number of Indo- Australian varanids have been maintained at Dallas Zoo. As a group, monitor lizards prove to be an active and attractive exhibit and appear to adjust well to captivity. In fact, the mortality figures for these varanids have been remarkably low as long as a few basic requirements are met. Since 18 March 1966, the only death has been a Varanus acanthurus brachyurus which died from a prolapsed hemipenis.

Members of the family Varanidae, especially the smaller forms seem to be sensitive to temperature and unless this is at an optimum level they fed only diffidently. We based our exhibits on the varanid activity temperatures of 35.5"~ (96-98.6"~) given by Dawson (1966). A technique which has worked well uses a heat lamp (Ken-Rad 250 W/IIO V infra-red or incandescent bulbs) to produce a 'hot spot' slightly warmer than the lizard's preferred temperature. In fact, the 'hot spot' temperature ranged from 37"~-39"c (98.6-102.2'~). The monitors maintained their body temperature throughout the day by basking intermittently. When the body temperature exceeded 38"c (100.4'~) small sequential contractions gave way to large gular pumping motions (Bartholomew & Tucker, 1964).

With some of the larger varanids, especially those in the process of maturation, a Ken-Rad 275 W/IIO V sun lamp was used for supple- mentary ultra-violet radiation. The bulbs were suspended 1-5 m ( 5 ft) from the substratum. At 0800 hours, the lights were turned on and kept burning until 1700 hours. There was a significant heat drop at night when the cage temperature gradually fell to 27"c (80.6"~). Relative humidity remained a rather constant 40%.

Most of the larger monitors were fed freshly killed rodents. Occasionally, in the case of in- dividuals feeding reluctantly, small chicks were offered. The smaller varanids were fed domestic grey crickets Gryllus domestica and newborn laboratory rats and mice. When a monitor refused all other varieties of food, a mixture of raw egg and finely chopped horse meat was presented. Strips of beef heart were also offered. Fresh water

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was available daily, either in small sterilised glass bowls or in a continuously running pool.

For some of the smaller varanids it was neces- sary to design cages that would allow the lizards to wedge themselves firmly in crevices, and these were formed by embedding pieces of rock in con- crete to form shelves. Various types of substratum were used. Thus, for the smaller semi-arid dwellers, fine sand was used which was sifted daily. For the semi-aquatic species, smooth river rock was used as it was easily washed. Plastic plants were used for additional security and ease of cleaning. The cages were completely dis- mantled each month and were washed thoroughly with Roccal disinfectant. The plastic plants, gravel and rocks were also cleaned and disinfected. To avoid cross-contamination between cages, all tools were disinfected immediately after they were used with the lizards.

When the lizards were received, they were soaked in a prophylactic solution of oxytetracycline hydrochloride (Cosa-terramycin) for 24 hours. Newly acquired monitors were then quarantined in fibreglass holding cages for a minimum of 30 days.

SPECIES IN C A P T I V I T Y Varanus acanthurus brachyurus Date of acquisition: One pair was received in October 1965 and another pair was acquired on 20 September 1967. Heat source: IOO W/I 10 V incandescent bulb. Enclosure : A glass-fronted fibreglass cage measuring 70 x 37.5 x 37-5 cm (274 x 142 x 142. in). Pieces of flat stone were embedded in concrete to provide shelves. The substratum was fine sand. Diet: Domestic grey crickets were given three times a week and newborn mice once a week.

Breeding: The monitors have attempted to breed on numerous occasions. The male was able to hold the female firmly and with a series of con- vulsive movements, impregnate the female. Although a pan of damp sand was placed in the cage, the female laid the eggs randomly through the cage. Unfortunately, the eggs were infertile. On 21 June 1968, the female was again observed

200 H U S B A N D R Y A N D RESEARCH

to be carrying eggs and was placed in an aquarium measuring60x 30x 30 c r n ( q x I Z X 12 in).Damp sand was placed in the aquarium to depth of 3 cm (1% in) and a flat rock was placed in the corner. The female excavated a burrow beneath the rock on 10 July 1968 and deposited four eggs on 11

July 1968. One of the eggs was destroyed. The remaining eggs were carefully removed, covered with damp paper towels and placed in a small crockery container. On 25 July 1968 the second egg spoiled and contained an embryo which had died a t an early stage of development. On 11

October 1968, the eggs were opened as a yellowish exudation was observed and were found to con- tdin two dead fully formed monitors.

Varantrs d. dutnerili Date of acquisition: An adult specimen was received on 17 March 1969 and adjusted well to captivit) . Heat source: IOO W/I 10 V incandescent bulb. Enclosure : A glass-fronted fibreglass cage measuring 70x 50x 37.5 cm (27+x zox 14% in). Diet: Freshly killed mice were fed three times a week.

Varanus giguntesis Date of acquisition: ,4 young specimen was received on 2 December 1969. Heat source: Ken-Rad 250 W/IIO V infra-red heat lamp; Ken-Rad 250 W/I 10 V sun lamp. Enclosure: The lizard was originally kept in a large cage measuring 2.7 x I 4 x I 4 m (9 x 6 x 6 ft) but was later moxied to a smaller cage measuring I 17.5 x 7ox 120 cm ( 4 6 ~ 2 7 6 ~ 47 in). Diet: Freshly killed mice and rats were fed three times a weck.

Vuranus grllenr Date of acquisition: Two adults were received on 18 January 1970 and were exceedingly nervous and flighty upon arrival. Heat source: IOO W-/I 10 V incandescent bulb. Enclosure : A glass-fronted fibreglass cage measuring 70 37.5 x 37.5 cm (27: x 142 x 143 in). The substratum was fine sand. Layered rock shelves \\ere u x d for security. Diet: Domestic grey crickets were fed thrice weekly and ne\\ born mice were fed once a week.

Va ranus gouldii jauirufus Date of acquisition: A young specimen measuring 30 cm (12 in) was received on 17 June

Heat source: IOO W/rro V incandescent bulb. Enclosure: A glass-fronted fibreglass cage measuring 7 0 x 5 0 x 37.5 cm (2712~ zox 142 in). The substratum was fine sand and there were a few scattered rocks. Diet: Since the lizard's small size was a factor limiting food size, grey crickets were used initially for food. As the monitor grew, the diet was changed to newborn mice. On 15 December 1970 the monitor measured 75 cm (296 in) and was feeding on adult mice.

1969.

17aranus niertensi Date of acquisition: An adult specimen was received on 22 March 1969 and immediately responded well to captivity. Heat source: IOO W/IIO V incandescent light bulb. Enclosure : A glass-fronted fibreglass cage measuring 7 0 x 50x 37.5 cm ( 2 7 4 ~ zox 149 in) with a few scattered rocks and a sand substratum. Diet: The monitor was given a freshly killed mouse twice a week but as the lizard's weight gain was rapid, this was changed to a weekly basis.

Varanus mitchelli Date of acquisition: Two adult specimens were received on 22 March 1969. Heat source: IOO W/I 10 V incandescent bulb. Enclosure: They were originally placed in an aquarium measuring 90 x 45 x 45 cm (36 x 18 x 18 in) but they were nervous and insecure. Finely sifted sand was used for the substratum and numerous rocks were used to provide a feeling of security. Since defaecation occurred frequently and was nearly always performed in the water dish, it was necessary to modify the cage arrange- ment. As the lizards' anal region was becoming inflamed with adhering sand, a larger, glass- fronted fibreglass cage measuring 7 0 x 50x 37.5 cm ( 2 7 3 ~ 20x 142 in) was substituted, and the substratum was changed to large smooth pebbles. A pool with running water was used to maintain a higher degree of cleanliness. Diet: Newborn mice were fed weekly.

HUSBANDRY AND RESEARCH 201

Varanus p. prasinus Date of acquisition: Two adult males were received on 2 December 1969 and were extremely nervous upon arrival. Heat source: Ken-Rad 250 W/IIO V infra-red heat lamp. Enclosure: A glass-fronted fibreglass cage measuring 70 x 70 x 120 cm (27+ x 278 x 47 in). Branches and plastic plants were used liberally to provide dense cover and ensure both horizontal and vertical flight distance. The monitors ap- peared to have some difficulty finding a water dish so it was necessary to design a small waterfall with constantly running water. Diet: One of the monitors began to feed im- mediately on small freshly killed mice. The other monitor was extremely emaciated and dehydrated and it was decided to feed and water it forcibly. A raw egg - chopped beef heart mixture was administered through a 10 ml syringe and catheter three times weekly. After two weeks, the lizard began to feed occasionally on the mixture from a low dish but it was still declining slowly. During this period, small rodents, crickets, lizards (Anolis carolinensis, Uta stansburiana and Sceloporus sp.) were offered but were invariably refused. A small chicken thigh was placed in the cage and was accepted during the night. Thereafter chicken thighs were eaten at regular intervals. Gradually, the diet was altered to small freshly killed laboratory mice offered on forceps.

Varanus salvadorii Date of acquisition: An adult specimen was received on 15 August 1970. Heat source: Ken-Rad 275 W/IIO V sun lamp; Ken-Rad 250 W/IIO V infra-red heat lamp. Enclosure: A large display cage measuring 2 . 7 ~ I ~ X 1.8 m ( 9 x 6 x 6 ft). The walls were covered with rock, and vines were placed through- out the cage. Diet: The monitor was nervous initially and refused to feed on freshly killed rodents. A small chick was taken on 21 August 1970 and it then began to feed regularly. On 22 September 1970, a freshly killed laboratory rat was taken and the monitor continued to feed on rats.

Varanus timorensis ssp. Date of acquisition: Two adult Varanus timorensis samilis were received on 22 March 1969, and 22 December 1968. An adult Varanus t. titnorensis was received 9 March 1970.

Heat source: IOO W/IIO V incandescent bulb. Enclosure: A glass-fronted fibreglass cage measuring 7 0 x 5 0 ~ 3 7 ’ 5 cm ( 2 7 4 x 2 0 ~ 14% in). The substratum was crushed rock which could be washed easily. Large limestone rocks were placed in the cage for the lizards’ security. Diet: Although there was no actual fighting, it was necessary to remove Varanus t. tinzorensis as it was unable to compete successfully for food. Grey crickets and newborn laboratory mice were given weekly.

Varanus tristis orientalis Date of acquisition: An adult specimen was received on 1 1 July 1967. Heat source: IOO W/IIO V incandescent bulb. Enclosure: A glass-fronted fibreglass cage measuring 7 0 x 3 7 . 5 ~ 37.5 cm (27 ix 1 4 % ~ 144 in). Flat sandstone rock shelves were fashioned in order to provide security for the lizard. The sub- stratum was sand. Diet: When received, the lizard was rather nervous and refused to accept crickets or newborn mice. Uta stansburiana and other small lizards were offered and accepted. Gradually, newborn mice were substituted for the lizards.

Varanus varius Date of acquisition: An adult pair was received on 18 March 1966 and began to feed well immediately. Heat source: Ken-Rad 250 W-IIO V infra-red heat lamp. Enclosure: Since the male was extremely aggressive toward the female, it was necessary to separate them. They were kept in individual glass- fronted fibreglass cages measuring I 17.5 x 70 x 120cm ( 4 6 ~ 2 7 8 ~ 4 7 i n ) . On 13 July 1970, the female was introduced into the male’s cage for breeding purposes. Attempts at copulation were observed on 15 July 1970 and 18 August 1970, but it could not be ascertained whether they were successful. The male raked his foreclaws upon the dorsum of the female and the male’s mandible was rubbed upon the female. The female was not held by the nape of the neck. Diet: Freshly killed laboratory rats for the male and mice for the female were fed weekly.

PRODUCTS MENTIONED I N THE TEXT

Heat lamp and Sun lamp: Manufactured by Ken- Rad, Owensboro, Kentucky, USA.

202 HUSBANDRY AND R E S E A R C H

Cosa-terramycin : Manufactured by Charles Pfizer body temperature, thermal conductance, oxygen and Company, Inc, New York, USA. consumption and heart rate in Australian varanid Roccal: Manufactured by Winthrop Laboratories, lizards. Physiol. Zuul. 37: 341 -354. New York, USA. DAWSON, w. R. (1966). Interspecific variation in

physiological responses of lizards to temperature. In REFERENCES Lizard ecology: 230-257. Millstead, W. W. (ed.) BARTHOLOMEW, G . A. & T L C K E R . u. A. (1964). Size, Columbia: University of Missouri Press.

Observations on Central American river turtles

at Fort Worth Zoo Dermatemys maivi

J 0 N A T H A N C A M P BELL Assistant Herpetarium Supervisor, Zoological Park, Fort Worth, Texas, USA The Central American river turtle Derinatemys mawi, the sole surviving species of an entire family of turtles, has remained comparatively rare in zoological collections throughout the world. It has a fairly restricted range extending from southern Veracruz south-eastward through Guate- mala; it is large and therefore requires a large cage; and it has a reputation for being difficult to maintain in captivity.

In April I 970, an adult pair was purchased from a native who captured them near Alvarado, Mexico. The male and female had carapace lengths of 45 cm (17% in) and weighed 11.8 and 10.4 kg (26 and 23 lb) respectively.

These turtles exhibit a striking degree of sexual dimorphism. Although both are of comparable size, their tail lengths are quite different. Viewed dorsally, the tip of the male's tail extends 14 cm (53 in) from the edge of the postcentrals, 5 cm ( 2 in) from anus to tail tip. On the other hand the female's tail barely extends to the outer edge of the postcentrals, and is only 1.7 cm (4 in) from anus to tip. Their sex is also easily determined by colour differences. The carapace of the male is a drab olive-yellow and all other parts are a light grey, except the top of the head which is yellow. The female is a uniform dark slate grey including the head. The plastron of both is a pale yellow.

Upon their deposition at the Fort Worth Zoo in April they were placed together in a large aquatic community exhibit measuring 5 . 2 ~ 2.1 m ( 1 7 x 7 ft) and having a maximum depth of 91'5 cm (3 ft). It soon became apparent that they were incompatible as they engaged in vicious biting, mainly on the posterior edge of the cara-

pace, but also on the legs, tail and neck. The female was subsequently moved to another tank measuring approximately 2' I x I '5 m (7 x 5 ft) and having a depth of 71 cm ( 2 8 in) that she shared peacefully with a Malayan water monitor Yaranus salvator. It was decided to allow the male to re- main in the larger community exhibit and he was carefully watched for evidence of aggression against any of the other animals in the tank. Turtles of the genera Podocnemis, Pseudemys, Chelydra and Staurotypus remained completely unmolested and only minor instances of biting occurred between Dermatemys and a single large specimen of Phrynops geoffroanus. This was per- haps because the latter was, after the Dermatemys, the largest turtle in the exhibit and possessed a shape vaguely resembling its own. The only other specimens in the tank, six 1.5 m (5 ft) caimans Caiman crocodilus showed none of the murderous attacks that they occasionally direct towards the smaller turtles.

In both tanks the year-round water temperature is maintained between 28 and 3ooc ( 8 2 " - 8 6 " ~ ) . The exhibits are lit by 40 watt 'Vita-lite' (Duro- test) fluorescent tubes, supplemented with 150 watt incandescent bulbs for better viewing. Dermatemys generalIy seems to shun light, show- ing a marked preference for the dark corners of the tanks.

I believe that Dermatemys should be classed among the most aquatic turtles. When placed out of the water our adults seem to be totally helpless and can move a few yards only, apparently under great strain. They never leave the water to bask, but have been noted lying motionless at the