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dc.contributor.authorMendes, Archie Joseph
dc.date.accessioned2013-09-27T06:37:19Z
dc.date.available2013-09-27T06:37:19Z
dc.date.issued1976
dc.identifier.urihttp://erepository.uonbi.ac.ke:8080/xmlui/handle/123456789/56989
dc.description.abstractExcept 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 -- 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 highen
dc.language.isoenen
dc.publisherUniversity of Nairobi,en
dc.titleThe Ecology And Reproductive Biology Of The Lizard, Agama Atrico11is Smith 1849en
dc.typeArticleen


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