A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in
fulfilment of the requirements for the degree of Master of Science.
Johannesburg, 1997. / Numerous studies have shown that reptiles are able to assess their environment and select
retreat sites based upon this assessment. Two main reasons proposed to explain retreat
choice are predator avoidance and thermoregulation. In my study, I conducted laboratory
experiments ,)0 16 Platysaurus intermedius in all attempt to elucidate what cues are used in
retreat site selection in these lizards ..Platysaurus intermedius use rock crevices as retreats
and I tested whether crevice height, depth and the thickness of the roof were important cues.
I also measured selected body temperature in a thermal gradient Field measurements of
lizard body temperature as well as crevice temperature of retreats not used by the lizards
were recorded and compared. Platysattrus intermedius show a significant preference for
narrow and deep retreats. This would appear to reflect an efficient anti-predatory tactic with
minor potential thermoregulatory consequences ..Potential predators observed in the field
would be unable to gain access to these lizards during the period that they are sequestered.
No significant differences in retreat or temperature selection (in the laboratory experiments)
by different age groups or different sexes were observed. However, temperatures selected
in the laboratory were considerably higher than those available in the field. This observation
possibly reflects an environmentally imposed limitation to thermoregulation to lizards in the
field. Field recordings of lizard body temperature (when inside retreats) and the temperature
of retreats not used by p. intermedius revealed that occupied crevices had significantly
higher temperatures than unoccupied crevices ..This indicates that P. intermedius may use
temperature as an environmental cue by which to select a suitable retreat. It would thus
appear that predation risks as well as thermoregulation are considerations for P. intermedius
when selecting a retreat site, however it is difficult to say with any confidence whether
predator avoidance or thermoregulation is of more importance. / MT2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/22178 |
| Date | January 1997 |
| Creators | Egan, Lorraine |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (65 leaves), application/pdf |
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