Southern ground hornbills (Bucorvus leadbeateri) (SGH) are co-operative breeders that occur
in groups of 2-9 individuals. Long life spans, large territory sizes (100km²), and low
reproductive rates render these birds vulnerable to threats such as loss of habitat, persecution
for their habit of breaking windows through territorial aggression, poisoning and loss of
suitable nesting sites. As a result, SGH are listed as vulnerable in the red data book of South
Africa as well as globally.
The main objective of this study was to contribute to our overall understanding of the ecology
and biology of the SGH for conservation planning. Data collection was completed in the nonprotected,
semi-arid landscape of the Limpopo Valley from June 2008 - September 2009. The
seasonal habitat use by a group of SGH, seasonal abundance (numbers) and biomass
(volume) of invertebrates using pitfall and sweep net methods was investigated. Furthermore,
a total of eight groups and 23 birds were captured in the Limpopo Valley and different
statistical analysis were performed to investigate levels of inbreeding, relatedness, sex-biased
dispersal and the effects the recent re-colonisation has had on the genetic structure of SGH in
the Limpopo Valley. Finally the genetic variation of the species in the rest of Africa was
determined using samples from Kenya, Tanzania and three populations in South Africa
namely the Limpopo Valley, Kruger National Park (KNP) and Kwa Zulu-Natal (KZN).
Genetic analysis revealed SGH have retained comparatively high levels of genetic diversity,
even though there are indications of genetic bottlenecks in the Limpopo, KNP and Kenyan
populations. The SGH populations studied were grouped into two clusters corresponding to
the geographic origin of samples. The birds from Tanzania and Kenya clustered together
while the KNP and KZN birds clustered together with the Limpopo population grouping
more or less equally between the Kenyan/Tanzanian and South African populations. A large
percentage of genetic variation was found within populations while among population
variation was low, indicating there is little molecular evidence for the presence of SGH subspecies.
The overall home range of one group was approximately 20 000 ha while seasonal home
ranges varied between 5000 ha in winter to 13 500 ha in summer. The response of organisms to environmental variables in this extremely seasonal habitat was further revealed by the
positive correlations found between the number of invertebrates with mean monthly
maximum and minimum temperatures, and the volume of invertebrates with mean monthly
rainfall. No significant differences were found between numbers and volume of invertebrates
per order, between sites, which was expected in this homogenous vegetation type dominated
by mopani shrub and trees (Colophospermum mopane).
The re-colonisation of the Limpopo Valley was shown to have occurred by a number of
unrelated individuals. This was demonstrable by very low levels of inbreeding and average
relatedness of the population, as well as the favourable levels of heterozygosity across age
and sex categories. Within group relatedness was high with juveniles related to at least one
parent from their natal group. Insights were also gained into the breeding behaviour of SGH,
providing evidence for the first time that SGH are not as monogamous as previously thought,
with two instances of extra pair copulations recorded between four groups.
This study shows that a holistic approach combining genetic techniques, radio telemetry
studies and ecological principles has great potential to further investigate SGH, thereby
contributing to the preservation of this enigmatic species of the savannah biome.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08162012-110102 |
| Date | 16 August 2012 |
| Creators | Theron, Nicholas Terence |
| Contributors | Prof R Jansen, Prof JP Grobler, Prof A Kotze |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08162012-110102/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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