Abstract
There is substantial evidence for the global decline in biodiversity due to habitat
fragmentation resulting from urbanisation. Bats, which are the second most
specious mammal order worldwide, are sensitive to anthropogenic alteration and
are among the mammals greatly affected by urbanisation. Insects – which also
serve as food to some bat species – are no exception to this dilemma. The
conservation of insects and other arthropods remains a relatively untouched topic
among the conservation community resulting in a relentless decline in their
biodiversity. Despite their ecological and economic value, bats and insects
remain poorly studied and misunderstood in most parts of the world. In the rural
areas and townships of South Africa, myths and misconceptions surrounding bats
persist which often result in the bats being driven out or exterminated. Likewise,
the interaction between bats and their arthropod prey is not well addressed
particularly in South Africa.
Gauteng forms part of the grassland biome which is rich in biodiversity. Being an
economic hub of South Africa and Southern Africa, this grassland is threatened
by the increasing economic development thus an increased rate of habitat loss
and fragmentation.
The effect of increased urbanisation on bat species richness and activity - as well
as the corresponding arthropod prey - was studied at three sites exposed to
different degrees of anthropogenic impact. All the study sites are within Gauteng
province, South Africa. Bat activities were monitored by means of a bat call
detector during new moon on a monthly basis. A survey of the available flying
insect was done simultaneously in the same localities where bat calls were
monitored by means of a light trap. Temperature and precipitation data were
recorded for the time and date of the surveys to see if there is a correlation
between temperature and precipitation and bat diversity and activity. Sampling
took place over a period of a year at each site from 2015 to 2017.
The ‘least impacted’ Krugersdorp Game Reserve lies in a peri-urban area in the
outskirts of Krugersdorp. The ‘moderately impacted’ Walter Sisulu National
Botanical Gardens lies within an underdeveloped nature strip flanked by highly
urbanised residential and commercial areas. The ‘most impacted’ site, Mofolo is
a locality in Soweto, a densely urbanised area in the South of Gauteng. No study
of bat diversity and activity nor of nocturnal flying insects have been done in
Mofolo, Soweto before this study. The diversity of bats was found to be influence
by the intensity of urbanisation while bat activity was not. The species richness,
and not abundance, of nocturnal aerial insects was found to be negatively
influenced by higher urbanisation intensities.
A significant positive correlation was found between bats data and temperature
as well as between insect data and temperature, the association was stronger for
insects and temperature. Some bat species were recorded in June and July (the
coldest months in South Africa) despite the popular belief that all bats hibernate...
M.Sc.