dc.description.abstract | Except for Harris' (1964) detailed
investigation, on a single species of agamid
lizard, Agama agama, studies on other agamids
of the genus Agama in Africa have been confined
either to taxonomic descriptions or to restricted
features of the animals life history and
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physiology. These studies, have also tended to
concentrate on one or other of the geographical
races of Agama agama.
This study reports on the ecological and
reproductive requirements of Agama atricollis, a
species widely distributed in Eastern and Southern
Africa, and confined to the tropical grassland -
scattered woodland vegetational belts.
The taxonomic position of this species
has led to considerable controversy, leading to
the creation of a number of sub-species on one
hand, and the lumping together, on the other
hand fall these sub-species sin into single species ,
Agama cyanogaster. For the purpose of this study,
the species has been identified as Agama atricollis,
by the British Museum (Natural History).
The controversy in the identification of
this species, and its suggested phylogeny has been
examined.Climatic and geological changes in the
Horn of Africa are believed to have resulted in a
savanna.- forest form migrating southwards and
restricted the more terrestrial forms to the arid
areas of N. Eastern Africa: Hence the similarity
between these two forms and the controversy
associated with it.
Agama atr1coLLL~ L~ a u~~~~ _
night territorial lizards sleep above ground
level, usually on trees. After emergence from
its sleeping site, the lizard basks, before
initiating daily activity. Thermoregulatory
activity forms an important category in the
daily life of this lizard, and is considered
in detail in this study. Other maintainance
activities like feeding and resting, and the
social reproductive activities involving
intra-specific interactions, like Aggression,
Courtship, Display and Nesting, are also
considered The third category included the
less frequented activities and locomotory
activity. When analysed on an hourly basis,
basking forms the most important early morning
and late evening activity. Feeding occurred,
soon after basking, and could occur at any time
of the day. Resting was prominent between
12.00 hours and 14.00 hours. Social reproductive
activity forms only 16.8% of the daily activity,
maintainance activity accounting for most of the
rest.
~..
" Between the sexes there are differences
1n the choice of habitat used for daily activity.
Also the amount of time spent by each sex for
each of the activities differs.
;Activities like feeding occur on the. ground,
while~r~stin, is an aboveground activity. The
habitat chosen.,~y Agama atricollis is therefore ~
e~harrced by those structures of the habitat that
.~rovide cover, sleeping sites and facilities for
dail~ activity. Tr~es, h~dges and other raised
structures like fence posts,' provide basking and
resting sites, facilities for observation of
prey items and for displays of various kinds.
Some of these sites are much more preferred as
activity sites than others, and as such are
defended by adult conspecifics against members of
the same sex. This has led to the acquisition
and defence of suitable activity sites, resulting
in a home range and territory.
An important element of the lizard's
daily activity is thermoregulation. The Critical
Maximum Temperature for this species is 44.SoC.
Between this lethal range and the temperature of
emergence after overnight rest, the lizard
maintains its body temperature at characteristic
levels, by using suitable thermoregulatory
behavioural postures.
The competition resulting from the acquisition
and retention of activity sites and territories,
involves the use of social behavioural elements
ln communication between individuals in the
po vlation. Agama atricollis males have a mean
~ +
home range size of O.OS - 0.02 acres. For the
period 1970-72, the mean maximal average and
territorial densities were 22 and 17 lizards per
acre respectively. Both sexes possessed territories,
the males having a larger territory than the
females.
~
Colour a,nA colour change form an important
Ln gred i'e n t in -t h e animals daily life. It is used
for concealment, possibly for thermo regulation,
and most often in social situations for asserting
territoriality. In females, ·changes in body
colouration reflect the pattern of ovarian
development. Social postures act as cues ~n
courtship and mating The aggressive intentions
of the lizards. and the sequence of postures used
~n fighting, convey to other con specifics their
territorial dominance.
Male lizards attain maturity from the
90-99 mm (snout-vent) size class, while female
mature from a size class of 80-89 mm The
reproductive condition of 271 males and 174
females were examined between the years 1972-73.
Male testes weights showed the highest increase
during the drier seasons of the year. Fecund
females with ovarian eggs were also found at the
peak of the dry seasons, and coincided with the
maximal testes weight increase in the male. Egg
laying occurred during the rains.
Nest construction, egg laying and the
packing and camouflage of the nest show a high
degree of parental concern The role of
pseudonests during nesting, is debatable Soil
moi/&ture is important for .egg development.
Between 0.75% and 4.0% moisture in the soil ~s
considered suitable for egg development. When
eggs are laid in the field, embryos are in an
advanced stage of development. It is not clear
what the stimulus is for initiating hatching. In
the field, rain seems to be strongly implicated.
The incubation time for eggs ~n the field .
was l14~.5 -15'.6 days. Predication pressure on
gatchlings in the field was particularly high | en |