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By Guy Van Heygen & Emmanuel Van Heygen
Several years of studying the
behaviour of Calumma tigris on Mahé and Silhouette on the
Seychelles Islands resulted in remarkable conclusions.
Introduction
Calumma tigris (Kuhl 1820) is endemic and the only chameleon occurring on the
Seychelles. The Seychelles are an archipelago in the Indian Ocean 4°
South of the Equator, 1600 km East of Kenya and about 1100 km North East
of Madagascar. It is an archipelago of mainly granite islands but
politically it covers 1.500.000 km² including coral islands like the
Amirantes and Coëtivy, and the far-away Alphone-, Farquhar- and Aldabra-group.
Calumma tigris only occurs on the three largest islands; Mahe,
Praslin and Silhouette.
Habitat
Its
habitat reaches from the coast towards the higher mountain regions. Due
to human impact in the coastal areas, the animals are now restricted to
the higher regions and undeveloped areas. The temperature in its habitat
varies from April to October between 22°C and 25°C during the daytime
and between 21°C and 23°C at night. From November to March these
temperatures fluctuate between 24°C and 28°C during daytime and between
22°C and 24°C at night. The humidity varies between 85%, on average
above 90% at noon and 99% at night all year round. These observations
were made at Jardin Marron on Silhouette Island at an altitude of 410
meters, about the same height as La Misère on Mahe. C. tigris
prefers the vicinity of water, like small brooklets and water parts, and
lives in the surrounding bushes and small trees,
often on the non-endemic cinnamon plants
Cinnamomum zeylanicum
dominating their biotope.
The most dense populations were registered on Mahe at La Misère and Le
Niol and on Praslin in Vallée de Mai and Fond Azore.
Description
 With a total length of only
16 cm Calumma tigris belongs to the smaller species of chameleons. It is
a shy animal, well camouflaged and hard to spot due to its colour and
capability to immobilize completely. On the chin there is a scaled
dewlap from about 2 to 3 mm long present. The flat helmet is less
developed. The primary colour of the body varies from light grey to
yellow and even bright green, and can change into dark brown or black.
The back is covered with small black dots, sometimes with several dark
or light grey saddle-shaped spots. The underpart and certainly the
throat are lighter than the rest of the body. The lips can be completely
white, even blueish. Both the chin and the back are serrated.
Reproduction
There are only a few records
on egg laying behaviour, and only in captivity. All chameleon species
are oviparous (egg laying) or ovoviviparous (giving live birth). All
oviparous chameleons have approximately the same egg laying habits; the
female digging a hole in the ground or forest litter to deposit the
eggs. In terrarium the C. tigris female digs a hole from only 2
to 3 cm deep (Markus and Anita Grimm, 2000).
Observations made during June
and July 2003 at La Misère on Mahe revealed that C. tigris
differs from all other chameleons in the way they reproduce, more
specific in the way they lay eggs. In the wild C. tigris does not
dig a hole to deposit the eggs, but the eggs are laid in the leaf funnel
of the wild pineapple, occurring frequently in his habitat. First
regarded with the normal scepticism, but finding eggs in more than 20
plants proved that C. tigris is an exception in the world of
chameleons. The wild pineapple in the Seychelles, an Ananas comosus
variety with small but very sharp pines along the leaf edge, was
introduced more than 200 years ago, at the end of the 18th
century. Laying eggs in such a small and difficult to reach spot, asks a
lot of adroitness and prudence. Seen it is impossible for this chameleon
population to change their egg-laying behaviour in such a short period,
they must have laid their eggs in the past in a plant with the same
properties, endemic to the Seychelles. It must be a plant, with leaves
collecting the rainwater, but like the wild pineapple not keeping it in
the funnel. A possibility are the native palm trees, there are six of
them in the Seychelles.
The most suitable plant seems to be the
endemic pandanus. Local people reported me to have found eggs in a
leaf-pit of a padanus in the South of Mahe in the neighbourhood of
Quatre Bornes. These people thought it were the eggs from the wolf snake
Lycognatophis seychellensis and destroyed them. Showing the
difference between the wolf snake eggs and the chameleon eggs, they
recognized them as Calumma tigris eggs. These screw pines
have more or less the same characteristics as the wild pineapple. In
these plants the eggs are also well protected and kept humid. The
cutting from the endemic palm trees and pandanus by men, and the
introduction of the pineapple, maybe more appropriate for the
requirements of Calumma tigris drove them to change plant to lay
their eggs. It is not impossible that some females in certain regions
were the appropriate plants are missing due to human impact returned to
there ancestor’s habit and lay their eggs back in the ground. In general
we can adopt that this behaviour counts for the whole of the Mahe
population. The records of Anita and Markus Grimm mention that C.
tigris in captivity digs a hole from only 2 to 3 cm, what is
extremely shallow for a chameleon from the Calumma group. This
can be an indication that Grimm’s animals in the wild were used to lay
their eggs in bromeliads, but due to the absence of a suitable plant in
their terrarium, returned to the habit of their ancestors and started
digging, and this explains the primitive structure of their nest. It was
generally accepted that C. tigris reproduced once a year during
the rainy season. But observations, made in 2003 during June and July,
proved that the reproduction of C. tigris does not depend from
the time of the year, but only by the amount of rain and the humidity.
2003 was extremely wet. After a short period of sunshine in March, a lot
of rain was recorded in April and May, respectively 15 and 19 rainy
days, more than normal for that time of the year. June and July were
exceptionally wet with 22 and 28 days of rain. These weather conditions
inspired the animals, and could be the reason why so many clutches were
found in these wild pineapples during this period. Observations made in
October and November ’03 revealed that egg laying continued at the same
level. During these rainy periods the soil turns into mud what makes it
very difficult for these animals to dig and the eggs would probably
suffocate. The leaves of the wild pineapple collect the water, but the
funnel is not watertight. A lot of debris lands in the funnel and
consists of putrefying leaves, twigs and older eggshells which keep the
eggs at the necessary humidity. In one wild pineapple several clutches
can be found. In one funnel I found 4 clutches, together 24eggs, on top
of a lot of empty egg-shells. In November when these wild pineapples
start flowering, it happens that the eggs are pushed up, out of the
funnel.
During October and November
hundreds of wild pineapples were examined at an altitude between 100 and
450m in the forests of Silhouette, but no trace of any chameleon egg,
fresh or hatched. The idea that the Silhouette chameleon never changed
its habit from digging to dropping them in a plant started growing. It
would not have been that surprising seen these two populations are
already separated for 18000 years since the last ice-age. But an
experiment with a female chameleon from Silhouette proved the contrary.
Soil with a perfect humidity and a few bromeliads were provided, so this
pregnant female had the choice to lay her eggs in 25 cm of soil or a
wild pineapple-like bromeliad. When her behaviour betrayed her need to
lay, she started to examine the different bromeliads, but she was never
seen on the ground. She was only interested in the 3 bromeliads which
were provided. After about one hour she started laying eggs in the leaf
funnel from one of the bromeliads. Carefully she descended backwards in
the funnel, and within 20 minutes she dropped her 5 eggs in the centre
of the plant. Afterwards she came out of the plant and turned round and
returned into the funnel upside down and started covering the eggs with
the putrefying leaves and mud she found in the leaf funnel.
Some more observations
The Calumma tigris juveniles
adapt their colour very quickly to the environment, they can turn
from white towards black in seconds.
All the eggs hatch during the daytime, and this only between 2
and 5 hours after sunrise.
Also amazing is to
see how very young animals climb onto very clean glass, nearly like
geckos do, but when they fall, they stay on the ground immobile for
about half a minute like dead, before moving again.
The adults are not
aggressive towards the juveniles. I have seen young chameleons
sleeping on the back, tail or legs from an adult. Also when they
cross each other, most of the time the young one walks over the back
of the adult.
Contrary to what mentioned in earlier
articles; never any aggression was seen between adults, certainly
not between males. Only a few times I observed a male chameleon
taking a defensive position when a female came too close (less than
10 cm). Its colour changes in seconds into brown till black. Just
holding himself with his hindlimbs and tail he starts swinging with
his body, in the meantime blowing with his mouth wide open to
impress the female, but the female ignored this and continued her
way, without any further contact. Sometimes just walking over the
back of the male. Never a male has been seen biting a female.
All Mahe chameleons I observed until
now were varying between grey and greenish yellow, with a much
clearer underpart. Depending from their mood or their surroundings
they can change into brown or nearly black. On the other hand all
Silhouette chameleons I have seen were really green, anyway much
greener than the members of the same specie on the main island. The
underpart differred hardly from the back.
As the change of
colour from most of the chameleon species is a result of temper
and condition, the change of colour from Calumma tigris mostly
depends from their environment. In their normal habitat, in trees
and foliage, they have their normal colouring as mentionned in the
description. Walking in a darker surrounding, like the forest floor,
they turn dark brown sometimes completely black. This change of
colour I never noticed with chameleons from Silhouette. These
animals I have never seen turning brown or black.
The tongue of
Calumma tigris is more than twice his body length or more than
his total length, which is extremely long for a chameleon. The
bigger the prey the stronger the retraction muscle has to be.
Chameleons are sit-and-wait foragers, which normally feed on
relatively large prey. As the offer on prey in Seychelles mostly
consists of smaller insects, the tiger chameleon was able to develop
a longer tongue than other chameleons normally do, but can no longer
catch preys bigger than 1 cm. A house-fly is the biggest he can
handle.
When humidity
drops under 60%, they look for a more humid spot, I have seen a
female putting her head into a leaf funnel, and staying there until
the humidity rised.
References
BOURQUIN, O. 1999.
Chamaeleo tigris; Seychelles Chamaeleon. Size and breeding. African
Herp News. (30):29. [P.O. Box 1083, Hilton 3245, KwaZulu-Natal, South
Africa]
GRIMM, A. & M. GRIMM (1999):
Das Tigerchamäleon (Calumma tigris). – Elaphe N.F., Rheinbach,
7(3): 11-15
GRIMM, A. & M. GRIMM (2000):
Weitere Beobachtungen zum Tigerchamäleon (Calumma tigris, [Khul
1820]). – Elaphe N.F.,
Rheinbach, 8(4): 73-75.
VAN HEYGEN, G & VAN HEYGEN, E
(2004) Eerste waarnemingen in de vrije natuur van het
voortplantingsgedrag bij de tijgerkameleon Calumma tigris (Kuhl 1820).
TERRA -Antwerpen 40 (2) :
p.49-51 |
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