610022681
Anti-predator behaviour in the European chameleon Chamaeleo chamaeleon
Abstract
Anti predatory behaviour is a major part of every ecosystem, it keep prey alive and keeps natural
selection thriving. In this study I have studied anti predator behaviour in the European chameleon, i
found no significance in my results, however there were a large number of confounding variables
taking affect on my data.
Introduction
Almost all animal species encounter predation throughout their lives and therefore display anti
predator behaviour in order to minimise their risk of predation; optimal anti predator behaviour is
the result of weighing the risk of predation against the benefits from other activities (Diaz-Uriarte,
1999). Anti predator behaviour varies greatly across different species, but the most effective way of
avoiding predation is to avoid encounters with predators in the first place, the most common forms
of this behaviour involve escape, camouflage, polymorphism or mimicry of noxious species
(Baranard, 1982). The ability to rapidly change colour for the affect of camouflage has evolved
independently in numerous invertebrate and vertebrate groups (Stuart-Fox et. al, 2008). One
example of a species which displays such a behavioural trait is the European chameleon, Chamaeleo
chamaeleon; however when waking from roosting, camouflage is a secondary anti predator
behaviour, the primary behaviour at this time is to exit the roost (a tree branch or other sufficient
vegetation) in order to avoid avian predators. The European chameleon is the subject of this
investigation.
Previous work into chameleon anti predator behaviour (Stuart-Fox et. al, 2006; Stuart-Fox et. al,
2008) investigated whether chameleons alter their anti predator behaviour when faced with
different predator species. They found that chameleons alter their colouration depending on the
colour perception of the predator species they are faced with.
Through this study aim to investigate whether variations in size, roost height and exposure affect
the time at which European chameleons make their first movement and become absent from their
roosts.
Methods
We undertook the study in small meadows in the surrounding area around the golden beach in the
Karpaz peninsula in northern Cyprus. After waiting for nightfall we split into two groups in order to
survey a larger area for chameleons roosting, the majority of chameleons were juveniles roosting on
branches or small plants. We were able to find 53 chameleons in total, at 5 separate patches. Upon
finding each chameleon we gave it a number, in the order in which we found them, and measured
its length from snout to vent using a 30 centimetre ruler, trying to cause minimum disturbance as to
not wake each individual. We then marked the branch it was roosting on with yellow tape in order to
find it the next morning. The following day we woke up before dawn in order to find all of the
chameleons before they woke up, a separate person surveyed each patch and two people went to
patch 1 and patch 5 as those patches had a large number of individuals roosting at them. First of all
the height at which each chameleon was roosting was measured, using a length of string and a ruler.
The level of exposure of each individual was also observed and categorised as either exposed (easily
visible from the ground or from above) or unexposed (enough cover to make it hard to be seen from
the ground or from above). Each person then travelled a transect along their patch every 5 minutes,
watching each individual for ten seconds to observe any movement. The time at which each
chameleon made its first movement was noted down (movement), then the time at which each
individual left its roost and could no longer be seen was noted down (absent); these times were then
quantified into minutes after 6 am. Each person left when every chameleon in their patch was
absent. After waiting an hour or so for full daylight we returned to each patch as a group and
identified the various plant species that the chameleons were roosting on.
Results
Absence in both roost height and length
200
12
180
10
140
8
120
100
6
80
4
60
40
Length (cm)
Roost height (cm)
160
Roost height
Length
Linear (Roost height)
Linear (Length)
2
20
0
0
0
20
40
60
Absent (minutes after 6 am)
Figure 1
As figure 1 shows, there is no significant difference between individuals of varying roost height or
length and the time at which they were absent. I performed a statistical test in the form of a twoway ANOVA to analyse the variance between this data, which confirmed that there is no significant
difference between the variance of roost height or length and absence (F=0.838, F crit=1.585,
P=0.737).
200
180
160
140
120
100
80
60
40
20
0
12
10
8
6
Roost height
Length (cm)
Roost height (9cm)
Movement in both roost height and length
4
Length
Linear (Roost height)
Linear (Length)
2
0
0
10 20 30 40 50 60 70 80 90
Movement (minutes after 6 am)
Figure 2
Figure 2 illustrates that there is no significant difference between varying levels of chameleon length
or roost height and the time that they made their first movement. I carried out a two-way ANOVA in
order to test for any significant differences in variance between the datasets; the ANOVA verified
that there are no significant differences between the variances of length or roost height and the
time of first movement (F=1.181, F crit=1.682, P=0.298).
Absence (minutes after 6 am)
Absence at high exposure and low exposure sites
65
60
55
50
45
40
35
30
25
20
15
10
5
0
High exposure
Low exposure
Figure 3
As figure 3 shows, there is very little difference in the mean absence for chameleons in high
exposure and low exposure roost sites; therefore there is no significant relationship between
exposure and time of absence. To test this relationship I performed a T-Test, the result of the T-Test
confirmed that there is no significant difference between high and low exposure sites (P=0.829).
Discussion
My results show that there was no significant difference between individuals at varying roost height,
length or exposure and the time at which they started moving or the time at which they became
absent. This may have been due to our sample size; with more samples we may have seen a
relationship. The fact that we performed the study over just one day may have also caused there to
be no significant differences, as there may have been certain environmental or behavioural
conditions associated with that day.
The lack of a significant difference in the results also may have been due to several confounding
variables. One such variable is our presence at the roost sight of the chameleons, as the presence of
a human does have a definite effect on both the chameleons and the predators foraging on them.
Although humans are not true lizard predators, they can act as a threatening stimulus, and hence
produce a continuous stress to the lizards (Labra and Leonard, 1999). Therefore the presence of
humans while observing the chameleons may have caused them to alter their behaviour, such as
choosing to stay camouflaged and delaying their movement to the ground; or it may have caused
the opposite and made the chameleons exit their roost earlier in order to get to the safety of the
dense undergrowth. Humans at the site may have also reduced the possibility of natural predators
approaching (Labra and Leonard, 1999). This would also have caused changes in the anti predator
behaviour of the chameleons, as if there were less predators approaching them then they may have
chosen to move from their roosts to the ground later, as there was less risk of being preyed on by
birds.
Another variable which may have affected the behaviour of the chameleons is the weather, more so
on the occasion that we made our study, as there was a storm the day beforehand with high wind
speeds and high precipitation, such weather is a rarity in Cyprus. High wind speeds, precipitation and
low insolation are likely to increase thermoregulatory costs (Hilton et. al, 1999), therefore as the
chameleons had lost higher levels of energy the day before due to increased thermoregulatory costs,
they may have travelled to the ground earlier in order to forage to regain the energy they lost. Also,
the frequency of predator attacks may be affected by climatic variables, as their food requirements
are also likely to increase in severe weather (Hilton et. al, 1999), due to the same reason; therefore if
predators are more likely to attack the chameleons may leave their roosts earlier to avoid predation.
If I was to undergo further work into this topic I would experiment into chameleon anti predatory
behaviour, by manipulating predator sounds, I would do so by playing different predatory bird calls
at varying volumes in order to see if there was any difference in reaction to separate species and
distance of predators. I would also like to investigate into how geographic location effects anti
predatory behaviour in chameleons, to do so I would travel to various locations around Cyprus,
making sure to find areas of varying plant species, then repeat this study at each location.
References






Antonieta Labra and Rafael Leonard – Intraspecific variation in anti predator responses in
three species of lizards (Liolaemus): Possible effects of human presence – Journal of
herpetology – 1999
C. J. Barnard – Anti predator behaviour – Animal behaviour – 1982
Devi Stuart-Fox, Martin J. Whiting and Adnan Moussalli – Camouflage and colour change:
anti predator responses to bird and snake predators across multiple populations in a dwarf
chameleon – Biological journal of the Linnean society
Devi Stuart-Fox, Martin J. Whiting and Adnan Moussalli – Predator specific camouflage in
chameleons – Biology letters – 2008
Geoff M. Hilton, Graeme D. Ruxton and Will Cresswell – Choice of foraging area with respect
to predation risk in Redshanks: The effects of weather and predator activity – Nordic society
oikos - 1999
Ramon Diaz-Uriarte – Anti-predator behaviour following an aggressive encounter in the
lizard Tropidurus hispidus – Proceedings: Biological Science – 1999