Harpij 4 2007
The
breeding of the Hahnelli dart-poison frog Epipedobates
hahneli
at
Antwerp Zoo
Ben van Dijck
Zoo Antwerpen
Traditionally
most zoos have not shown
much interest in keeping amphibians, although this is now
changing with the “Amphibian Crisis”. The dart-poison
frogs are an interesting group of amphibians with a variety
of means for sexual reproduction. In all cases though
females respond to male calls, and fertilization occurs
externally. Antwerp Zoo received a group of
captive-bred Hahnelli dart-poison frogs from a
private breeder in September 2006. The frogs are kept at 26°C during the day, and 21 to 22°C
during the night, with a humidity around 80 to 90%. The lighting cycle is 12 hour
day:12 hour night, additionally a small window also provides
some natural daylight. The enclosure contains various
climbing plants and different potential sites for egg
deposition. The enclosure received only 30 seconds of
misting the first two months after the frogs arrived, and
thereafter 1 minute three times a day. The males immediately
began calling once misting was increased, and 13 eggs laid
in a film roll container were found within a week.
The
eggs were left in the enclosure for 24 hours to allow time
for fertilization, and then were moved to a covered petri
dish containing a layer of water that did not entirely
inundate the eggs. The tadpoles emerged after 14 days, and
were transferred to individual butter containers filled with
water that was changed every two days. Spirulina was fed.
Once the “froglets” had all four legs but also still had
a tail, dry land was made available and feeding them ceased.
Eleven of the 13 grew well and were reared successfully,
becoming frogs at 65 days of age. A second clutch laid
thereafter was reared in the traditional group method. The
tadpoles within this clutch differed greatly in growth and
only one survived to become a frog, dying a few days later.
Although tadpoles in the genus Epipedobates are not known to
be cannibalistic (as Dendrobates are) or to otherwise
interfere with each other’s growth, it may be advisable to
rear at least this species individually.
The husbandry and breeding of the Gila monster at Rotterdam Zoo
Henk Zwartepoorte
Diergaarde
Blijdorp - Rotterdam Zoo
The
author first describes taxonomy, distribution and the venom
of the Gila monster. The current breeding group of Gila
monsters held at Rotterdam Zoo consists of a male received
from Wassenaar Zoo in 1987,
two males from Dallas Zoo in 1999, and a female from
a Dutch private breeder in 1999.
The
Gila monsters moved to a
600x350x250 cm enclosure in the Sonora Desert area of
the just constructed “Oceanium” in 2001, where they are
held together with other lizards, i.e. Sauromalus hispidus,
Sceloporus magister, and Crotaphytus collaris. The Gila
monsters spend the night and entire winter hibernation in 2
to 3 m long PVC pipes that can be inspected and serviced by
keepers from the back side of the exhibit. The water is
changed daily in the 80x70x20 cm pool that provides drinking
water and bathing opportunities. Lighting is provided by
two 1000 watt HQI
lamps. The lights are on between 7:30 and 22:00 in the
summer and 7:30 to 19:00 in the winter (approximately
November to March). An Osram Ultravitalux lamp is also used
8 hours per day during the summer months. The enclosure is
kept around 25°C in the summer, but can reach 50°C under
the four 175 watt heat lamps that provide “sunning”
opportunities. The enclosure temperature is influenced by
outside temperatures in the winter, and can decrease to
ca.15°C. The
floor is warmed by a cable below the 30 cm deep layer of
river sand. The hibernation area is kept at 10°C during the
winter.
The
Gila monsters at Rotterdam Zoo primarily eat already-killed
adult mice and “pinky” rats,
and occasionally a day-old-chick. The adults receive
3 to 5 prey items per week; consumption is well monitored as
these lizards can easily become overweight. The winter
hibernation from November to March is essential for good
reproductive condition. The males begin challenging each
other when they come out of hibernation. The female is given
extra food between the copulation period and egg laying. She
is moved to a separate enclosure when she becomes visibly
rounder; this has always occurred in May. The female makes
good use of the 100 watt
UV lamp in her temporary enclosure. The eggs are
laid in June, specifically between 11 en 28 June
during the last five years. Clutch size varied from 7 to 9 eggs between 2002 and 2007.
The
eggs are incubated at 27.5 °C with a relative humidity of
95 and 100% in
a Jaeger incubator in open containers lined with dry
vermiculate. The incubation period varies from
120 to 144 days under these conditions. The
hatchlings are held as a group in a glass terrarium. A
100x50x40 cm terrarium is sufficient for four to six young.
The ambient temperature is ca. 25°C, reaching 45°C
under the heat lamp. After one week, the young
lizards are
each fed one pinky mouse ca. two weeks of age. The number of
prey given is increased according to appetite and growth,
but again it is important to ensure that these lizards do
not become too fat.