Instrumental Conditioning and Learning in Poroderma Pantherinum
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UNIVERSITY OF CAPE TOWN Applied Marine Science INSTRUMENTAL CONDITIONING AND LEARNING IN PORODERMA PANTHERINUM Town Cape of University IMKE MEYER Supervisors: Dr Cecile Reed Meaghen McCord December 2016 1 The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town Contents 1. Plagiarism declaration…………………………………………………………...………….. 3 2. Abstract…………………………………………………………………………...………….. 4 3. Introduction………………………………………………………...…………….……...…... 5 3.1 Shark Sensory systems.............................................................................................................................. 6 3.2 Types of learning...................................................................................................................................... 7 3.3 An overview of research illustrating learning in elasmobranchs............................................................ 8 3.4 Anthropogenic impacts on benthic sharks.............................................................................................. 11 3.5 Leopard catsharks as experimental species........................................................................................... 12 3.6 Aim and hypotheses................................................................................................................................ 14 4. Materials and Methods............................................................................................................ 15 4.1 Study location and experimental sharks.................................................................................................. 15 4.2 Experimental set up.................................................................................................................................. 16 4.3 Experimental protocol.............................................................................................................................. 18 4.4 Data collection......................................................................................................................................... 20 4.5 Data analysis............................................................................................................................................ 21 5. Results........................................................................................................................................ 24 5.1 Observations of stress-related behaviours of Leopard catsharks........................................................... 24 5.2 Efficiency of Leopard catsharks completing a food-reward task in a captive environment................... 26 5.3 Behavioural observations and interactions of Leopard catsharks with the target between trials......... 28 5.4 Comparative analysis of individual Leopard catsharks......................................................................... 30 6. Discussion.................................................................................................................................. 32 6.1 Stress-related behaviours......................................................................................................................... 32 6.2 Efficiency in completing food-reward tasks............................................................................................. 33 6.3 Behavioural observations and interactions with the target..................................................................... 34 6.4 Assessment of individual shark behaviour............................................................................................... 35 6.5 Limitations and recommendations for further studies............................................................................. 36 6.6 Conclusion................................................................................................................................................ 36 7. References................................................................................................................................. 37 8. Acknowledgements................................................................................................................... 41 9. Appendix................................................................................................................................... 42 2 1. Plagiarism declaration Declaration 1. I know that plagiarism is wrong. Plagiarism is to use another’s work and pretend that it is one’s own. 2. I have used the Harvard convention for citation and referencing. Each contribution to, and quotation in this project from the work(s) of other people has been attributed, and has been cited and referenced. 3. This project is my own work. 4. I have not allowed, and will not allow, anyone to copy my work with the intention of passing it off as his or her own work. Signature Removed Signature ______________________________ Date _________21/11/2016________ 3 2. Abstract Recent research has shown that higher cognitive functions and learning occur in teleosts and elasmobranchs. Very little is known about the cognitive abilities of benthic sharks and no research has been published on the learning ability of the endemic Leopard catshark (Poroderma pantherinum) species of South Africa. This species is listed as data deficient on the IUCN red list and known threats due to anthropogenic impacts include fatalities because of bycatch and depredation in the small-scale commercial fishing industry. It has been suggested that sharks can be attracted to fishing boats through the sound of outboard motors and an association can be formed between the sound and easy prey on the hooks of fisherman. This pilot study examined the learning capacity of Leopard catsharks in Hermanus, South Africa, by using a series of food-reward tests based on instrumental conditioning. A target with black and white stripes was used as the discriminative stimulus, while an auditory cue acted as a bridging stimulus for the food-reward task. Sharks were collected by hand whilst diving and shore-angling in Hermanus from August 2015 to November 2015 and acclimatised before the onset of experiments. Four juvenile sharks were trained through operant conditioning using visual and auditory stimuli for ten days each, consisting of six trials per day. A fifth juvenile shark, acting as the control, was trained through the same method without the auditory stimulus to test the influence thereof on the learning rates of Leopard catsharks. This study showed that Leopard catsharks have the ability to associate a visual stimulus with a food reward through the aid of an auditory cue. The auditory cue was also shown to increase learning rates significantly as an association was formed between the presence of food in front of the target and the auditory signal. The individual sharks in this study displayed differing levels of stress and learning rates. It is suggested that even though Leopard catsharks show high diversity in learning rates and adaptation to stress, they possess the ability to learn and adapt rapidly to changing environments. The results possibly have important implications for the understanding of learning and conditioning in Leopard catsharks and the likely anthropogenic threats caused through learned behaviour in benthic sharks. 4 3. Introduction For many years it was believed that only land vertebrates such as mammals and birds are capable of learning associations between different stimuli (Schluessel, 2015). These animals have a neocortex which plays a role in the control of higher perceptual processes, cognitive functions and intelligent behaviour (Bayer & Altman, 1991), and includes processes such as perception, recognition, judging and reasoning (Guttridge et al., 2009). Over the last 60 years, research has shown that higher cognitive functions and learning, occurs not only in terrestrial vertebrates, but also in teleosts and elasmobranchs (Brown & Laland, 2003). The majority of studies on the learning ability of aquatic vertebrates are centred around fish with commercial importance such as salmon (Salmonidae) and cod (Gadidae) (Brown & Laland, 2003). Little research has focused on the learning abilities of elasmobranchs and the understanding of the basic principles of learning is therefore lacking (Kimber et al., 2014). Elasmobranchs evolved independently of bony fishes (Osteichthyes) to form a diverse group known as the cartilaginous fishes (Chondrichthyes) (Pough et al., 1999). They occur in highly dynamic environments and have evolved different levels of phenotypic plasticity which can accommodate adaptations in morphology and behaviour (Guttridge et al., 2009). Coastal environments are particularly dynamic due to freshwater influxes, atmospheric influences and anthropogenic impacts (Dill, 1983). Recent studies show that relative brain size is linked to the ability to adapt and survive in changing environments (Reader & MacDonald, 2003; Sol et al., 2008). Elasmobranchs living in highly dynamic coastal regions would therefore require significant cognitive functions to optimise behaviours such as navigating, locating food, avoiding predators and acquiring appropriate mates for reproduction (Kimber et al., 2014). The ability to learn a specific reactive behaviour