The influence of artificial light on the foraging efficiency and diet of insect eating bats
- Authors: Bailey, Lauren
- Date: 2019
- Subjects: Predation (Biology) , Bats -- Effect of light on , Bats -- Nutrition , Moths
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/76376 , vital:30555
- Description: Artificial light may be altering the interactions between bats and moth prey. Unable to make use of bat evasion strategies around artificial light, eared moths are susceptible to exploitation by syntonic bats (using echolocation frequencies between 20-50 kHz within the hearing range of eared moths). Using a handheld plasma metabolite analyzer, I evaluated the foraging success of syntonic bats and rarer allotonic bats (using echolocation frequencies outside the hearing range of eared moths), in areas with artificial light and in areas of natural darkness. I used microscope diet analysis to determine whether bats were consuming more or fewer moths in areas with artificial light and in areas of natural darkness. Syntonic bats were more selective for moth prey under lit conditions, likely owing to a reduction in the ability of tympanate moths to evade bats. Moths increased in the diets of generalist syntonic bats (Pipistrellus hesperidus) foraging around artificial light sources. Some P. hesperidus individuals showed high β-hydroxybutyrate levels around lights, but there was no difference in β-hydroxybutyrate levels between lit and unlit conditions. There is insufficient evidence to reject the null hypothesis that the foraging success of syntonic bats is equivalent in lit vs unlit conditions. The foraging success and diets of allotonic bats, Rhinolophus capensis, appear to be negligibly impacted by artificial light on a small scale. My study emphasizes the need for a mechanistic understanding of the influence of artificial light on the foraging success of bat species. Bat-moth interactions may be influenced by other factors apart from the common assumption that increased refuelling rates will occur in syntonic species foraging on moths around artificial light.
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- Date Issued: 2019
The biological control of Hakea sericea Schrader by the Hakea seed-moth, Carposina autologa Meyrick, in South Africa
- Authors: Gordon, Antony John
- Date: 1993
- Subjects: Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5648 , http://hdl.handle.net/10962/d1005330 , Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Description: Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to be healthy at the two study sites, respectively. One seed crop will always be available for regeneration, since recruitment is linked to fires, and wild-fires occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.
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- Date Issued: 1993