PhD (Zoology) / Department of Zoology / An ever growing human population and accelerating land use change is associated with the
loss of species and their ecosystem services. Agricultural intensification has led to a
worldwide threat of extinction to about one quarter of all bat species, despite the valuable
ecosystem service of pest control provided by bats. The decline in bat populations is
mainly attributed to the loss or fragmentation of habitats, roost sites and feeding
opportunities related to agricultural intensification and land use change. Therefore, proactive
management of bat communities in agricultural landscapes is essential. South Africa is the
world’s largest producer of macadamias and the industry continues to grow.
This study gains insight into the habitat use and foraging behaviour of insectivorous bat
species on a temporal and spatial scale, in and around macadamia orchards in order to
advise management strategies on how to increase bat activity and, possibly, pest control. It
also focuses on the preferences of artificial roost sites used by insectivorous bats in
macadamia orchards. The diet of insectivorous bat species is especially difficult to study and
the least invasive tool to gain information is the study of bat faecal pellets. In order to
provide evidence for the consumption of pest insect species by bats and thus incentive to
farmers for a more integrated pest management approach (IPM), this study explored
molecular approach to insectivorous bat diet analyses using fragment analysis of bat faecal
pellets with fluorescent-labelled species-specific primers (designed for the CO I gene).
This study was conducted in the subtropical fruit growing area of Levubu, Limpopo province,
South Africa between the towns Thohoyandou (22°59'03.7 S, 30°27'12.8 E) and
Makhado/Louis Trichardt (23°03'03.6 S, 29°55'12.7 E). Levubu also accounts for the second
highest production of macadamia in South Africa.
An introduction to the order Chiroptera and into the relevance of insectivorous bat species to
agriculture as well as the importance of a more integrated pest management approach (IPM)
focusing on bats is provided in Chapter One.
Bats were acoustically monitored and light traps were used to catch arthropods during one
annual cycle. I sampled five macadamia orchards once a month from September 2015 to
August 2016 and used GIS and R to analyse both the general bat activity and foraging bat
activity of the two main foraging guilds (open-air/clutter edge guild) in different land use
types as well as total bat activity with respect to arthropod abundances. As reported in
Chapter Two, results show that the overall clutter edge guild activity (number of passes)
decreased with macadamia and orchard (all other fruit) cover in the macadamia high season
(December to end of May) and increased with bush cover and distance to settlements
(potential roosts) in the macadamia low season (June to end of November). Open-air guild
activity increased with fallow cover (uncultivated grassland with scattered trees and shrubs)
in the high season. Foraging activity (feeding buzzes) of the clutter edge guild increased with
bush cover over the whole year. Total activity (both guilds) increased with abundance of true
bugs (Hemiptera), including the main macadamia pests, and bush cover. Macadamia cover
has a negative effect on the activity of the clutter edge guild in the high season, with low
activity in the orchard center (high cover), and activity increasing in a linear way with
decreasing orchard cover at the orchard edge (low cover).
These results suggest that the clutter edge guild prefers foraging close to the edges of the
orchards rather than in the center, while the open-air guild prefers semi-natural habitats
(fallow). When numbers of pest arthropods drop in the macadamia orchards, the natural
land use type, bush, becomes a more important foraging habitat and thereby increased the
activity of the clutter edge guild.
From June 2016 to July 2017, I scanned 31 bat houses, mounted on poles on six macadamia
orchards, for bats or any other occupants such as wasps, birds and bees. Twenty-one multichambered
bat houses of three slightly different chamber designs were erected on poles, in
sets of three. Additionally, five bat houses of the type ‘Rocket box’, four bat houses in sets of
two (black and white) and one colony bat house were erected. Bats were counted and visually
identified to family or species level. From December 2016 to end of March 2017, three IButtons
were installed to record temperature variation between one set of three bat houses. As reported in
Chapter Three, results show that the central bat house in the set of three and the black bat
house in the set of two had a significantly positive effect on bat house occupancy. There was
a significant difference in the mean temperature between the houses in the set of three,
with a significant difference in temperature of 0.46°C between the central and the first bat
house. The three bat houses erected in sets varied slightly in their chamber design, with the
central bathouse having the most chambers (six), while the bat houses to either side had less
chambers (four), set at an angle or straight. This and the insulation to either side by the
other bat houses is assumingly what caused the central bat house to be on average warmer.
The Yellow-bellied house bat (Scotophilus dinganii) was by far the most recorded and the
only species observed to co-habitat a bat house with another animal species, in particular
honeybees. The study might confirm assumptions in that the microclimate of bat houses,
respectively their insulation, sun exposure and color appear to be important factors
influencing bat house occupancy. The two preferred bat houses in our study were the black,
in the set of black and white, as well as the central, and on average warmest bat house, in the
set of three.
I collected bat faecal pellets with two different methods between July 2015 and April 2017
to determine the prevalence of pest insects in faecal pellets. Eighteen of the bat houses (in
sets of three) on three different farms and two Egyptian slit-faced bat (Nycteris thebaica)
roosts were fitted with trays in order to collect pellets from those occupied by bats. I noted
occupancy of bat houses to species or family level to keep disturbance minimal. Additionally,
I collected pellets from individuals captured by means of mist nets and harp traps. Four of
the main pest-insects; the two-spotted stinkbug (Pentatomidae: Bathycoelia distincta), the
green vegetable bug (Pentatomidae: Nezara viridula), the macadamia nut borer (Tortricidae:
Thaumatotibia batrachopa) and the litchi moth (Tortricidae: Cryptophlebia peltastica), were
collected from pheromone traps or after scouting for primer development and optimisation.
After extracting DNA from the bat faecal samples the target regions were amplified in a
multiplex PCR and fluorescently labelled PCR amplicons were analysed and interpreted. In
order to verify multiplex analyses results, all samples were amplified with all four sets of
primers in plates and those that produced amplicons were purified and sequenced. As
reported in Chapter Four, results show that fragment analyses yielded a total of 63 out of
103 samples tested positive for pest insect species (61%) with a total of 92 positive
fragments. Primer specificity could be confirmed to 100% for the sequences obtained for
Bathycoelia distincta (26/26) and Nezara viridula (12/12) primers but not for all sequences
obtained fot Cryptophlebia peltastica (18/30) and Thaumatotibia batrachopa (1/14) primers.
One sample showed no positive fragments but contained a positive sequence for N. viridula.
Three samples tested positive for one pest-species fragment but contained a positive
sequence for a second pest-species (B. distincta, T. batrachopa and C. peltastica). Adding
four positive fragments and one additional positive sequence to the data. This means that
sequences of pest insect species were obtained from 54 out of the 103 samples (55.6%) with
a total of 73 pest insect sequences. For the high season (December to end of May) a total of
37 positive fragments for the four pest insect species and 24 negative samples were yielded
and for the a low season (June to end of November) a total of 36 positive fragments and 15
negative samples. Looking at the pest consumption of the different bat species or families,
our results show that all of them foraged on pest insect species. Whereas, all species and
families except Myotis bocagii and Rhinolophus simulator (for which N<2) foraged on both
the Lepidopteran and Hemipteran pest species. Therefore, all families of bats of which faecal
pellets were analysed for this study (Molossidae, Nycteridae, Rhinolophidae and
Vespertilionidae) foraged on one or more of the four pest insect species.
In summary, Chapter Five concludes that natural and semi-natural vegetation promote bat
activity in macadamia orchards, and potentially bats' provision of the ecosystem service of
pest control. In times of accelerating land use change, remnants of natural vegetation are
important refuges and need to be maintained or restored to conserve bat species and
promote their ecosystem services. The study also shows that bat activity might be improved
by adding roosting opportunities to orchards. Warm and well-insulated bat houses mounted
freestanding on poles and in sets appeared to work best in northern South Africa. Further
research on co-habitation of bat houses and displacement behaviour as well as the potential
importance of altitude and distance to water is needed.
All of the species or families of bats from which faecal pellets were collected have been
confirmed to forage on at least one of the four pest insects and the bat species have shown
to be much more generalist and presumably opportunistic feeders than previously assumed.
Thus, this study provides incentive and advice to farmers for a more integrated pest
management approach (IPM). / NRF
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:univen/oai:univendspace.univen.ac.za:11602/1315 |
| Date | 18 May 2019 |
| Creators | Weier, Sina Monika |
| Contributors | Taylor, Peter J., Tscharntke, Teja, Grass, Ingo |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 1 online resource (107 leaves : color illustrations, color maps) |
| Rights | University of Venda |
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