2004

Asiatic Herpetological ResearchVol. 10, pp. 236-240

Some Aspects of Breeding Biology of the Bengal Lizard(Varanus bengalensis) in Bangladesh
M. FARID AHSAN1 AND M. ABU SAEED2
1Department of Zoology, University of Chittagong, Chittagong 4331, Bangladesh; E-mail: mfahsan@ctgu.edu
2AGROCARE, Golden Plaza (1st Floor), 58 Shaheed Tajuddin Ahmed Sharani, Mohakhali, Dhaka 1212,

Bangladesh
Abstract. - Some aspects of breeding biology of the Bengal, or Gray, Monitor Lizard (Varanus bengalensis) werestudied in the farm area of Azra Produces Impex (a private enterprise) at Bhaluka, Mymensingh from 1995 to 1997.
The feeding success, caring, egg-laying, clutch-size, incubation of neonate care were observed. The eggs were laid
between August and October with a mean clutch-size of 21.1 (range 10-32, n=25). The mean incubation period was
192.7 days (range 189-216 days, n=678) with a hatching success of 3.3% which was very low due to many reasons.
Some problems regarding farming of the species are discussed.
Key words. - Varanus bengalensis, Bengal lizard, breeding, farming, Bangladesh.

Introduction
The Bengal, or Gray, Monitor Lizard (Varanus bengalensis) is one of the three varanid species found in
Bangladesh. It is most widely distributed throughout thecountry, including many islands, in both forested andnon-forested open wooded areas. It is economicallyimportant for its valuable skin and its role in the ecosystem, especially in controlling some pests. In
Bangladesh, some tribes like the Shawtal, Kulee, Kukis,etc., also eat its meat.
The few research works that have been done on
varanids in Bangladesh mainly deal with their distribution. However, Whitaker and Hikida (1981) and Akond
et al. (1982) briefly worked on the ecology and stomach
contents of varanids. There is no published report on thecaptive breeding of varanids of Bangladesh. Azra
Produces Impex, a private enterprise, started a project inBangladesh on the farming of V. bengalensis. As advisor(MFA) and consultant (MAS) we looked into the biological aspects of the project. This paper deals with thepreliminary observations on feeding, caring, egg-laying,clutch-size, incubation of eggs, and caring of hatchlings.
Some problems regarding farming of the species havealso been discussed.

Study Area and Study Animals
The Varanus breeding farm of Azra Produces Impex issituated at Habirbari of Bhaluka Thana (MymensignDistrict, Bangladesh, 24° 21' N and 90° 21' E). It is 71
km north of Dhaka City and located adjacent to theDhaka-Mymensign Highway. The farm was inauguratedin June, 1995 within a concrete boundary wall (about 3© 2004 by Asiatic Herpetological ResearchFigure 1. Adult Varanus bengalensis eating suppliedfood.

m high including wire rope) enclosure with an entrance(gate) on the western side along the said Highway. The
total area of the farm is 37.74 acres (16.77 ha). There are
50 ponds inside the farm and a lake excavated aroundthe periphery of the farm. One open wire-net enclosure(37 m x 61 m x 1 m) with a concrete base (of 25.4 cm)
has also been made inside the farm area for some of thelizards (about 200 individuals).
A total of 2,112 Bengal lizards (685 [32.4%] males
and 1427 [67.6%] females) were released inside thefarm area. These lizards were captured by professional
hunters from wild stock (with the permission of the concerned authority, Ministry of Environment and Forests,Government of the People's Republic of Bangladesh) of
Greater Mymensign and Tangail districts between 4
June and 9 September, 1995. Before releasing, eachlizard was physically checked and sex recorded. Injuredand immature lizards were rejected.

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2004

Figure 2. Eggs of Varanus bengalensis in a natural nest (left) and being prepared for artificial incubation (right).

Methods
Food. Cleaned pieces of stomach (omasum part only) ofbovines, collected from different slaughter houses ofDhaka city, were supplied to the lizards as food. Food
was supplied only inside the wire-net enclosure in trays(25.4 cm x 25.4 cm x 5 cm, made up of tin sheet). In
other parts of the farm, food was thrown near the roosting places (close to bushes) of the lizards. Usually foods
were supplied to the lizards every alternate day (exceptfor Sunday) - half of the farm area was covered in one
day and the rest half in the next day. About 100-150 suchstomachs were offered to the lizards on every feedingday (Fig. 1).
Eggs. Eggs (Fig. 2, Table 1) were collected from holes
in the soil (dug obliquely) and holes of termite mounds(either natural or made by lizards) and placed inside artificial holes made in the incubation cages. Special precautions were taken during handling of eggs to avoid
shaking or turing upside down, so that, embryos do not
get loose or shift from the original position.
Incubation. An incubation area was selected inside thefarm where two cages were built (Fig. 3), each one having a small entrance. Cage-I was closed cart-shaped(12.5 m x 4.6 m x 2.6 m), made of wire-net (mesh size
5 mm x 5 mm) with a concrete base and supported byrods. Inside the cage three artificial incubation beds
were built - western (1240 cm x 116 cm x 55 cm), middle (1240 cm x 110 cm x 48 cm) and eastern bed (1240cm x 95 cm x 32 cm). Spaces between western and middle beds were 53 cm, and between middle and eastern
were 43 cm. In each bed, two storied oblique holes wereexcavated - the western bed had holes only in the eastern side, the eastern only in the western side, and themiddle bed had holes on both sides. Sandy, granular, anddry soils were placed on the floor of each hole and dry

sands on the hole mouth. The roof of each hole wasmade by moist sandy loam. The top of each bed wascovered with grasses. Each hole (length 30 cm anddiameter 10 cm) was marked by numbered stick plate.
Altogether there were 190 holes in cage-I and 30 eggs
were placed in each hole. When all holes of cage-I werefilled with eggs (totalling 5,700), the second cage (cageII) was built in the eastern periphery of the cage-I. CageII was closed rectangular-shaped (12.5 m x 7.9 m x 2.5m) formed of wire-net (mesh size 5 mm x 5 mm) andsupported by rods and poles. Here, only pits were dug,and 30 eggs were placed in each pit. There were 500
such pits (containing 14,499 eggs in total) in this cageand each one was marked with numbered stick plate.
These pits were filled with loose soils in such a way thata 5-7 cm thick soil layer was on the eggs. The pits werecovered with broad (palm) leaves during hot days toretain moisture in the soil. When topsoil of cage-II was
too dry, water was added. Later on, some grasses grewnaturally.
Hatching and Hatchability. After two months of incubation, several nests were excavated weekly to check forhatching and 2-5 eggs were opened to see the development of embryos (Fig. 4). Those hatched (Fig. 5) wereimmediately transferred into baby nursery. When sufficient number of hatchlings were obtained in cage-I, all
the remaining eggs which seemed to be still alive weretransferred into 7 big trays (0.5 m x 2.5 m x 0.25 m) in
the nursery, these trays were kept separate from thehatched lizards by a wall of 1 m within the nursery. The
earlier mentioned precautions were taken during thistransfer. Eggs were placed half-buried in the tray soil
with the usual cover. Each tray was checked twice a day(morning and late afternoon) and the number of hatchlings was recorded. Then hatchlings were released
immediately in the nursery after careful noting of theirmeasurements (Table 2).

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Asiatic Herpetological ResearchVol. 10, p. 238

Figure 3. Incubation cages for Varanus bengalensis. Cage I (left), Cage II (right). See text for description.
Table 1. Varanus bengalensis egg sizes (n=24).
Size
Length (cm)Width (cm)Weight (gm)Mean ± SD
5.71 ± 0.41
2.92 ± 0.06
26.93 ± 5.45

Range
4.92 - 6.18
2.80 - 3.04
25.2 - 31.5

Baby Nursery. The concrete floor of the nursery (9.5 mx 3.6 m x 3 m) was covered with sandy loam soil. Tinsheets (40 cm high) were fitted against the nursery walls
to prevent the escape of the baby lizards. Lumps of termite mounds containing termites (adults, mostly eggsand larvae) were placed in the periphery of the nursery
as food for the hatchlings. Other foods offered to thebabies were crushed boiled poultry eggs, minced beef
and minced clean stomach of bovine. Two artificial
small water reservoirs (25.4 cm x 25.4 cm x 5 cm) weremade in the nursery.
All non-hatched eggs were piled and randomly 100
eggs from incubation cage-I and 150 from incubation
cage-II were opened to determine the percentage of
undeveloped eggs and dead embryos (Fig. 4).

Observations, Results, andDiscussion
Food. Besides the supplied food, lizards were also seen
to eat arthropods especially beetles and grubs from cowdung, and small fish (mainly Tilapia, which wereTable 2. Size of hatchling Varanus bengalensis (n=39).
Size*
Total length (cm)Body length (cm)
Tail length (cm)Mean ± SD
19.72 ± 1.31
9.24 ± 0.59
10.52 ± 1.02

Range
17.2 - 22.2
8.3 - 10.4
7.5 - 12.5

Total weight (gm)13.61 ± 3.73

8.3 - 22.1

* Total length (snout to tail tip), body length (snoutto anus), and tail length (anus to tail tip).

released in the lake for propagation).
Caring. Sick lizards were provided with food closer tothem. Medical treatment was not given.
Eggs. Eggs were white, oval, with soft leathery skin andcontained a large yolk supply. The farm staff collected a
total of 20,499 eggs from the holes of termite mounds
during 11 September to 30 October, 1995. Although thefirst clutch of eggs (18) were found on 10 August, 1995
inside a termite mound on the embankment of a pond
inside the farm, this was not recorded by the farm staff(so it is excluded from the total count). The average collection of eggs was 512.67 + 134.49 (range 160-1210,n=38 days) per day.
Whitaker and Hikida (1981) and Akond et al.
(1982) stated that the egg-laying period of Bengal lizard
in Bangladesh is November and December. Daniel(1983), however, reported that eggs were collected frommid April to October in India. In Sri Lanka, the peakbreeding period of Bengal lizard is January to April, buteggs also occur during June to December in ground logs
or termite mounds (Deraniyagala, 1958). In the present
study the egg-laying period was much earlier than thatrecorded by Whitaker and Hikida (1981) and Akond etal. (1982).
The mean size of egg was 5.71 cm in length, 2.92
cm in width and 26.93 gm in weight (Table 1). FromIndia, Daniel (1983) reported that the average egg sizeof gray lizard was 4.9 x 3.8 cm (range 4.7 x 3.6 to 5.5 x
4.4 cm, n=50) and weighed 11.4 gm (range 8.3-14.3 gm,n=25). The size of eggs in this study (Table 1) is close tothat reported by Daniel (1983), but the weight data arevery different.
Clutch size. Clutch size varies according to the size andage of the females, larger and older females lay moreeggs than younger and smaller ones. The average clutch
size was 21.1 + 7.4 (range 10 - 32, n=25). The clutch
size of Bengal lizard was 8-32 (Whitaker and Hikida,Vol. 10, p. 239

Asiatic Herpetological Research2004Table 3. Minimum and maximum air temperatures and soil temperature (°C) during study period.
AirMonthNovember 1995
December 1995
January 1996
February
MarchApril
May
June

Soil

Minimum

MaximumMorning

Late afternoon

20.4
18.0
16.7
19.8
22.7
NR
27.3
25.4

25.6
22.4
20.8
20.8
26.7
NR
35.0
32.8

22.4
18.0
16.5
19.6
22.3
NR
29.8
27.7

24.8
22.1
22.5
25.1
28.1
NR
30.4
29.6

NR- Not recorded.

1981; Akond et al., 1982) and 20-30 (Khan, 1987) in
Bangladesh, while 8-30 in India (Daniel, 1983). The
range of present observation is close to the mentioned
works except for Khan (1987).
Incubation period. On average, the incubation periodof egg was 192.72 + 4.59 days (range 189-216 days,n=678 eggs). The first lizard hatched on 18 March andthe last on 4 June, 1996. Most of the lizards hatched late
at night or early in the morning; some also hatched during the day.
Previously recorded incubation periods for theBengal Monitor Lizards of Bangladesh were 7-8 months(i.e., 210-240 days) (Whitaker and Hikida, 1981); 6-8months (i.e. 180-240 days) (Akond et al., 1982) and 7-8months (i.e. 210-240 days) (Khan, 1987). Daniel (1983)
mentioned that the incubation period of Bengal lizard inIndia was 8-9 months (i.e. 240-270 days). The present
incubation period is closer to that recorded by Whitakerand Hikida (1981) and Akond et al. (1982), but smaller
than that reported by Daniel (1983). The egg-hatchingmonth has been mentioned as July (Whitaker andHikida, 1981) and June-July (Akond et al., 1982) whilein the present observation it spreads over mid March toearly June.
The variation in the incubation period of the present
work and those of the above mentioned works could be
due to the effect of some ecological factors like temperature, moisture, rainfall, etc. We recorded air temperature in the farm and soil temperature of nest of the incubation cage-I (and later baby nursery) which give anindication of these conditions (Table 3).
Hatchlings and hatching success. The average total
length and weight of the hatchlings were 19.72 cm and13.61 gm, respectively (Table 2). Out of 20,499 eggs,
only 678 babies hatched. The hatching success, in thiscase, was 3.3%. (All the hatched eggs [678] were fromcage-I only and the hatching success was 11.9%, but theeggs from cage-II resulted the poor hatching success i.e.,3.3%). After hatching out, a baby lizard did not eat for
the next 2-3 days due to a continued absorbance of its
yolk reserve. Neonate lizards ate termite eggs and larvae
from the supplied lumps of termite mounds inside theFigure 4. Varanus bengalensis in two stages of development: embryo (left), newly hatched (right).

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Asiatic Herpetological ResearchVol. 10, p. 240

5. Needs incubation chamber, or at least a place(s)where temperature and moisture fluctuaions are notdrastic.
6. Needs separate “nursery” cages for neonates andjuveniles.
7. Above all, instructions and suggestions proposed
jointly by the advisor and consultant should be considered in all activities.

Acknowledgments
Figure 5. Varanus bengalensis neonates.

nursery and crushed boiled poultry eggs from the feeding trays. They showed less interest to eat minced beef
and minced bovine stomach. Babies also drank waterand preferred to roost in cold, damp areas inside grasses
or water hyacinths, which were kept in a few placesinside the nursery.
The poor hatching success of eggs in this study wasmost probably due to: (1) soil in the incubation cage-II
became compact due to rain and killed embryos; (2)mis-handling of eggs by the staff during egg transplantation; (3) unregulated temperature and moisture in theincubation cages. Of these reasons, the first one wasmost important because only 12 eggs hatched from theincubation cage-II (where 14,799 eggs were transplanted) and dead embryos or babies were found in 70% of
the eggs (n=140). On the other hand, we were not surewhether all the unhatched eggs were fertilized or not.
The additional reason for this huge damage of eggs was
the negligence of the Managing Director of the projectto implement our suggestions in constructing incubation
cage-II.
Problems regarding farming
The following problems were faced during the study
period:1. The set up of the project is not well designed andscientific.
2. Lack of electricity.
3. Instructions/suggestions given (jointly by theadvisor and consultant) to the Managing Director(MD) of the project were not properly followed.
4. Research facilities provided by the farm are poor.
Recommendations
1. Lizards should be caged rather than distributing
them throughout the farm. A few small cages should
be built for research.
2. Needs devoted staff.
3. Needs electricity.
4. Incubation cages should be constructed like cage-I.

Dr. M. A. G. Khan, Department of Zoology, Universityof Chittagong has kindly reviewed this manuscript. The
proprietor and farm staff of Azra Produces Impex helpedus in various ways. We thank them all.

Literature Cited
Akond, A. W., F. Ahsan, and M. Rahman. 1982. Monitorlizards of Bangladesh. Proceedings of the Second
National Conference on Forestry held in 21-26
January 1982:540-545.
Daniel, J. C. 1983. The book of Indian reptiles. Bombay
Natural History Society, Bombay. 141 pp.
Deraniyagala, P. E. P. 1958. Reproduction in the monitor lizard, Varanus bengalensis (Daudin). Spolia
Zeylanica. 28:161-166.
Khan, M. A. R. 1987. Bangladesh er banayaprani, part I(Wildlife of Bangladesh, vol. I). Bangla AcademyPress, Dhaka. 175 pp. (In Bengali).
Whitaker, R. and T. Hikida, 1981. Report of project formation mission to Bangladesh (monitor lizards).
FAO, Rome.