Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The foraging mode of the Cape grass lizard, Chamaesaura anguina, was determined by
using three criteria: 1) the number of movements per minute (MPM) and the percentage
of time spent moving (PTM) during periods of activity; 2) the amount of tongueflicking
directed at cotton applicators labelled with prey chemicals as a measure of prey
chemical discrimination; 3) the stomach contents of the lizards as an indication of the
natural diet. Observations were made by means of binoculars from an observation
tower using a seminatural outdoor enclosure, and through a one-way glass panel using a
seminatural indoor enclosure. Each lizard was observed for aIO minute period during
peak activity and the times it was moving and the times it was stationary were recorded.
Data obtained in the indoor- and outdoor enclosures did not differ significantly and
were pooled. "MPM(0.37 ± 0.21 SD) and PTM (1.92 % ± 0.93 SD) values recorded for
C. anguina (N = 10) fall within the range given as characteristic for sit-and-wait
foragers. Nine C. anguina individuals were habituated in glass terraria to accept
mealworms offered to them. When all lizards accepted food without hesitation, they
were tested for their ability to discriminate among three different odours presented to
them in a randomized block design: prey odours consisting of mealworm surface
odours, distilled water as an odourless control stimulus, and cologne as a pungency
control. The number of tongue-flicks directed at the cotton applicator containing the
stimulus odour during 60 s was recorded. No statistically significant differences were
found among the responses to the three treatment odours (Kruskal-Wallis, H = 2.41, dj
= 2, P = 0.30). An analysis of the stomach contents of21 C. anguina specimens
revealed a diet of mostly diurnally active arthropod prey species. The preferred body temperatures selected by 12 grass lizards in a thermal
gradient were measured six times during a 48 hour period, using a copper-constantan
thermocouple inserted into the cloaca. The measured body temperatures (N = 72)
ranged from 22.62 oe - 27.07 oe with a mean of24.82 oe ± 2.27 SD. The low
preferred body temperature exhibited by C. anguina as compared to other cordylids may
be attributed to the combined influence of vegetative cover, high altitude, and high
surface-volume ratio. To determine movement patterns and microhabitat use, six
lizards were observed in a seminatural outdoor enclosure (4 x 4 m). The location of the
grass tufts in the enclosure was mapped, and the position of each lizard within the
enclosure was noted on 17 mornings. Observations of lizard behaviour during periods
of activity were made by means of binoculars from an observation tower. Although C.
anguina did not show reliance on a specific shelter site, the taller, broader tufts were
generally preferred as refuges during inactivity. There were significant differences
between the heights (student's z-test; P < 0.001) and the diameters (Mann-Whitney; P <
O.00 1) of the preferred grass tufts, and those grass tufts that were not preferred as
refuges, respectively. The lizards usually sheltered in a coiled-up position in the middle
of the grass tufts close to the ground. During active periods, the lizards perched in an
elevated position in the vegetation by entangling their elongated bodies and tails in the
grass for efficient weight distribution. Locomotion was mainly restricted to the strike
action when attacking prey.
Fynbos and grassland, which are the main habitat of grass lizards of the genus
Chamaesaura, are fire-prone. With their serpentiform morphology, grass lizards differ
markedly from other cordylids, the majority of which are rock-dwelling. One aim of
this study was to determine whether grass lizards make use of refuges like burrows or
crevices within their grasslrestioid habitat during periods of inactivity or when threatened by fire. Refuge selection during inactivity was determined experimentally.
Twelve lizards were offered different refuge options, namely grass tufts, crevices,
burrows and loose sand. All twelve lizards preferred to shelter in the grass tufts. When
the grass tufts were removed, only two lizards made use of the burrows and crevices
provided, the other 10 not sheltering at all. Refuge selection when threatened by fire
was tested by placing the 12 lizards in an enclosure provided with grass tufts and two
types of refuges, burrows and crevices. The grass was set alight at one end of the
enclosure and the fire was fanned on towards the other end with the aid of a high-speed
fan. Precautions were taken to ensure the safety of all the lizards and to intervene when
they were in direct danger. Only two of the 12 lizards sought shelter in the refuges
provided. Of the remaining 10, six fled and four were trapped by the flames, requiring
intervention. The results of these experiments, as well as field observations, suggest
that C. anguina seldom makes use of shelter options other than grass and restio tufts,
even when threatened by fire. In the case of fire, it flees by 'grass-swimming'. Field
observations also suggest that mortality during and after a fire is considerably higher
than in the case of rock-dwelling cordylids.
The reproductive status of adult females (N = 85) were determined on the basis of
the developmental stage of ovarian follicles and the presence or absence of oviductal
eggs. Females were grouped into four reproductive categories: pre-vitellogenic, early
vitellogenic, pre-ovulatory and gravid. To determine the reproductive cycle exhibited
by the males (N = 46), testicular volume and seminiferous tube diameter were
measured, as well as the spermatogenic activity assessed qualitatively. Spermatogenic
activity was assessed by using Licht's (1967) classification system. The snout-vent
length (SVL) of 144 specimens was measured. Sexual size dimorphism (SSD) recorded
for C. anguina was quantified by a size dimorphism index (SDI). Reproductive activity was asynchronous among females, differing from the normal cordylid cycle of
autumn/winter vitello genic activity, followed by winter/spring ovulation and gestation
in late summer to autumn. The significant seasonal variation that existed in testes
volume (ANOVA; F (7,22) = 3.70; P < 0.05) and seminiferous tubule diameter (ANOVA;
F (10,25) = 4.90; P < 0.05), as well as sermatogenic activity as observed by histological
examination, indicated that C. anguina males follow an annual spermatogenic cycle that
can be described as post-nuptial. The cycle is characterized by summer/autumn
spermiogenesis, associated with sperm storage throughout winter. Chamaesaura
anguina males differ from other cordylids following a post-nuptial cycle, by starting
with spermatogenesis in spring. The mean SVL of female grass lizards (109.51 mm ±
20.60 SD) was significantly larger (Mann-Whitney; P < 0.001) than that of males (84.77
mm ± 9.39 SD). A positive SDI of 1.29 and a SDImax of lAO were determined.
Female-biased dimorphism in SVL recorded for C. anguina corresponds with the
general pattern recorded for terrestrial cordylids, but contrasts with male-biased
dimorphism in rupicolous forms. The longer SVL of C. anguina females facilitates
higher fecundity. This, in turn, might be an adaptive survival strategy for this lizard
species in the fire-prone environment where it occurs, because successful recruitment is
facilitated by high fecundity.
KEYWORDS: Chamaesaura anguina; serpentiform body; cryptic colouration;
grass/restio habitats; undulatory locomotion; foraging mode; preferred body
temperature; movement patterns; microhabitat use; fire susceptibility; refuge
selection; reproductive cycle; sexual size dimorphism.
4 / AFRIKAANSE OPSOMMING: Die voedingswyse van Chamaesaura anguina is bepaal deur drie kriteria: 1) die getal
bewegings per minuut (BPM) en die persentasie tyd wat aan beweging bestee word
(PTB) tydens aktiewe periodes; 2) die hoeveelheid tongskiete wat gerig word na
wattepluisies bedek met prooi chemikalieë as 'n maatstaf van prooi chemiese
diskriminasie; 3) die maaginhoud van die akkedisse as 'n indikasie van hul natuurlike
diëet. Waarnemings is met 'n verkyker vanaf 'n waarnemingstoring langs 'n
buitemuurse kampie gemaak, terwyl dit deur 'n eenrigting glaspaneel in die geval van 'n
binnemuurse opstelling gemaak is. Elke akkedis is vir 'n periode van 10 minute tydens
piek-aktiwiteit dopgehou, en die tye wat dit beweeg het en nie beweeg het nie, is
aangeteken. Data verkry in die binnemuurse - en buitemuurse opstellings het nie
statisties van mekaar verskil nie en is saamgevoeg. BPM (0.37 ± 0.21 SD) en PTB
(1.92 % ± 0.93 SD) waardes aangeteken vir C. anguina (N = 10) val binne die reeks
waardes wat as kenmerkend vir sit-en-wag voeders beskou word. Nege C. anguina
individue is in glas terraria gewoond gemaak om meelwurms te aanvaar wat hul
aangebied is. Toe al die akkedisse die kos sonder huiwering aanvaar het, is hul vermoë
getoets om tussen drie verskillende geure wat hul aangebied is in 'n ewekansige
blokontwerp, te diskrimineer: prooigeur bestaande uit die reuk van meelwurms,
gedistilleerde water as 'n geurlose kontrole stimulus, en reukwater as 'n skerp kontrole.
Die hoeveelheid tongskiete gerig na die gegeurde wattepluisie gedurende 'n 60 s
periode, is aangeteken. Geen statisties-beduidende verskille is gevind tussen die
reaksies tot die drie geure nie (Kruskal-Wallis, H = 2.41, df= 2, P = 0.30). 'n Analise
van die maaginhoude van 21 C. anguina individue het meestal dag-aktiewe arthropoda
prooispesies onthul. Die voorkeur liggaamstemperature wat deur 12 akkedisse in 'n termiese gradiënt
geselekteer is, is ses maal gemeet gedurende 'n 48 uur periode, deur van 'n termo-koppel
wat in die kloaka geplaas is, gebruik te maak. Die bepaalde liggaamstemperature (N =
72) het gevariëer van 22.62 oe - 27.07 oe met 'n gemiddeld van 24.82 oe ± 2.27 SA.
Die lae voorkeur liggaamstemperatuur van C. anguina mag dalk toegeskryf word aan
die gekombineerde invloed van plantbedekkingskadu, hoë hoogte bo seevlak, en hoë
oppervlakte-volume verhouding. Die bewegingspatrone en mikrohabitat-gebruik van C.
anguina is bestudeer deur ses akkedisse in 'n buitemuurse kampie aan te hou. Die
ligging van die graspolle binne die kampie is op 'n kaart aangeteken, en die posisie van
elke akkedis binne in die kampie is op 17 oggende aangeteken. Verdere waarnemings is
gemaak met 'n verkyker vanaf 'n waarnemingstoring terwyl die akkedisse aktief was.
Alhoewel die C. anguina individue nie herhaaldelik 'n spesifieke skuilplek gebruik het
nie, het hul die langer, breër graspolle as skuilplek gedurende onaktiwiteit verkies. Daar
was 'n hoogs beduidende verskil tussen onderskeidelik die hoogtes (studente z-toets; P <
0.001) en die deursnitte (studente I-toets; P < 0.001) van die verkose graspolle, en die
graspolle wat nie gekies is as skuilplekke nie. Hulle het gewoonlik in 'n opgerolde
wyse, in die middel en na aan die bodem van die graspolle, geskuil. Daar is gevind dat
C. anguina vanaf 'n verhewe posisie voed deur sy verlengde liggaam en stert in die
grass te vervleg om doeltreffende gewigsverspreiding te verseker. Beweging was
hoofsaaklik tot die vangaksie van prooi beperk.
Vuur is 'n algemene verskynsel in fynbos en graslande, wat die hoof habitat van
grasakkedisse van die genus Chamaesaura uitmaak. Met hulle slangagtige morfologie,
verskil grasakkedisse drasties van ander lede van die Cordylidae, waarvan meeste
rotsbewonend is. Die doelwit van hierdie studie was om te bepaal of die grasakkedisse
gebruik sal maak van skuilplekke, soos gate en klipskeure binne die grashabitat, gedurende periodes van onaktiwiteit of wanneer bedreig word deur vuur. Twaalf
akkedisse is verskillende skuilopsies aangebied, naamlik graspolle, klipskeure, gate en
los sand. Al twaalf het verkies om in die graspolle te skuil. Toe die graspolle verwyder
is, het slegs twee akkdisse die klipskeure en die gate benut, terwyl die ander 10 nie
geskuil het nie. Skuilplek-seleksie wanneer bedreig word deur vuur, is getoets deur 12
akkedisse in In afskorting te plaas wat met graspolle en twee tipes skuilplekke, gate en
klipskeure, voorsien is. Die gras aan die een kant van die afskorting is aan die brand
gesteek en is aangehelp m.b.v. 'n hoë-spoed waaier. Voorsorgmaatreëls om die
veiligheid van al die akkedisse te verseker en om in te gryp as hulle in direkte gevaar
sou verkeer, is getref. In twee van die 12 gevalle het die akkedisse skuiling gesoek in
die beskikbare skuilings. In die oorblywende 10 gevalle het ses akkedisse gevlug,
terwyl vier deur die vlamme vasgevang was en daar ingegryp moes word. Die resultate
van hierdie eksperimente, sowel as waarnemings wat in die veld gemaak is, dui daarop
dat C. anguina selde van skuilopsies, anders as graspolle en restio's, gebruik maak as
hulle deur vuur bedreig word. In die geval van vuur, vlug hulle deur te "swem" deur die
gras. Veldwaarnemings dui ook daarop dat mortaliteit gedurende en na die vuur
heelwat hoër is as in die geval van rotsbewonende gordelakkedisse.
Die reproduktiewe status van volwasse wyfies (N = 85) is bepaal deur die
ontwikkelingsfase van ovarium follikels te ondersoek en deur die teenwoordigheid of
afwesigheid van eiers in die oviduk. Wyfies is in vier reproduktiewe kategorieë
gegroepeer: pre-vitellogenies, vroeg vitellogenies, pre-ovulatories en dragtig.
Testikulêre volume en saadbuisdeursnit is gemeet, en spermatogeniese aktiwiteite soos
histologies vasgestel, is gebruik om die reproduktiewe siklus van die mannetjies (N =
46) te bepaal. Spermatogeniese aktiwiteit is bepaal deur van Licht (1976) se
klassifikasie sisteem gebruik te maak. Die snoet-kloaak lengte (SKL) van 144 individue is gemeet en die seksuele grootte-dimorfisme (SGD) soos bepaal vir C. anguina, is
gekwantifiseer deur middel van In grootte-dimorfisme-indeks (GDI).
Voortplantingsaktiwiteit in die wyfies was nie gesinchroniseerd nie, en verskil dus van
die normale gordelakkedissiklus met herfs/winter vitellogeniese aktiwiteit, winter/lente
ovulasie en swangerskap in die volgende laat somer tot herfs. Die beduidende
seisoenale verskil wat bestaan het in die testesvolume (ANOV A; F (7.22) = 3.70; P <
0.05) en die saadbuisdeursnit (ANOVA; F (10,25) = 4.90; P < 0.05), asook testis
histologie, het aangedui dat C. anguina mannetjies 'n jaarlikse spermatogeniese siklus
volg, beskryf as "post-nuptial". Hierdie siklus word gekenmerk deur somer/herfs
spermiogenese, geassosieer met spermstoring gedurende die winter. In teenstelling met
ander gordelakkedisse wat hierdie siklus volg, begin spermatogenese in C. anguina
alreeds in die lente. Die gemiddelde SVL van die wyfies (109.51 mm ± 20.60 SA) was
beduidend groter (Mann-Whitney; P < 0.001) as dié van die mannetjies (84.77 mm ±
9.39 SA). In Positiewe GDI van 1.29 en In GDImax van 1.40 is gemeet. Wyfie-plus
dimorfisme in SKL bepaal vir C. anguina, stem ooreen met die algemene patroon
waargeneem by terrestriële gordelakkedisse, maar is in kontras met mannetjie-plus
dimorfisme by rotsbewonende vorme. Die langer SKL by wyfies van C. anguina kan In
hoër fekunditeit fasiliteer. Dit mag dalk In oorlewingstrategie vir die species wees wat
in In vuurgeteisterde omgewing voorkom, omdat suksesvolle rekolonisering deur In hoë
fekunditeit aangehelp word.
TREFWOORDE: Chamaesaura anguina, slangagtige liggaam; kriptiese kleuring;
graslrestio habitatte; kronkel beweging; voedingsrnetode; voorkeurtemperatuur;
bewegingspatrone; mikrohabitat-gebruik; vatbaarheid vir vuur; skuilplekseleksie;
voortplantingsiklus; seksuele dimorfisme.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52515 |
| Date | 03 1900 |
| Creators | Du Toit, Annemarie |
| Contributors | Mouton, P. Le F. N., Flemming, A. F., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 109 p. : ill. |
| Rights | Stellenbosch University |
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