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Predator cognition: the role of chemicals in prey choice and warning signal evolution

ReferenceBB/D003245/1
Principal Investigator / Supervisor Professor Candy Rowe
Co-Investigators /
Co-Supervisors
Institution Newcastle University
DepartmentSch of Biology
Funding typeResearch
Value (£) 124,753
StatusCompleted
TypeResearch Grant
Start date 01/10/2005
End date 31/12/2007
Duration27 months

Abstract

Perception and cognition are crucial processes in the evolution of animal communication. This is particularly evident in insect warning signals, where toxic prey indicate their unpalatability to predators using conspicuous signals. These can be vivid colour patterns, pungent odours, or rattling sounds, but most often, insect combine two or three of these into a multisensory display. Predators learn to avoid these signals to reduce their toxin intake, and many studies have shown that insect warning signals are designed to be particularly effective in the avoidance learning process. However, one critical aspect of predator avoidance learning that has been omitted by current theoretical and empirical analyses of warning signals, is that of the defence chemistry itself. This is a complex issue. Although insects store toxins internally, many also secrete chemicals when attacked by a predator. These secreted chemicals may or may not be toxic. We need to know how birds perceive and learn about these chemicals in order to predict how warning signals and defence chemicals function in the real world. Perhaps more importantly, knowing how birds process this information in their foraging decisions will provide basic knowledge for the development of avian repellents for the agriculture industry. Our existing research has already shown that multiple defence chemicals can have a significant effect on the learning process in avian predators. However, we have been unable to separate the different interacting effects between internal toxins and distasteful external chemicals. We have established a new protocol by which we present birds with a sequence of prey which can be edible or chemically defended, and use taste and visual signals to signal their toxicity. Our aims are to: 1. Establish that birds can learn to use taste signals to indicate internal toxin; 2. Test whether taste signals enhance the association between toxicity and visual signals. Answering these questions will provide essential data about associative learning. There is a significant body of work in the experimental psychology literature concerned with taste-toxin associations, and also whether taste can enhance colour aversion learning after a single encounter. We build on this to look at how these processes work when animals have to discriminate between different stimuli, and in particular how interactions between taste, toxin and colours affect asymptotic avoidance rates. This is important for testing current models of warning signal evolution, since asymptotic avoidance rates are likely to be a significant selection pressure exerted by predator psychology on prey survival. Specifically, we will use our data to re-evaluate mathematical simulations of mimicry and warning signal evolution, since the use of taste signals make new predictions about the stability and evolution of insect communication. In addition, we will also make testable predictions about the evolution of insect defence chemistry, and for the first time bring a psychological perspective to an ecological problem. Our work studies basic cognitive processes in an adaptive context. The results will have a significant impact on our own field of receiver psychology and signal evolution, but also be of wider interest to researchers who work on brain and behaviour at multiple levels, for example cognitive and systems neuroscientists. The data are also important for the development of avian repellents for the agricultural industry, where seed eating by birds inflicts millions of pounds worth of damage annually. This systematic study of avian gustatory abilities will be the first of its kind. Using this new data in association with visual signals could be an important step in producing more safe and effective deterrents.

Summary

Perception and cognition are crucial processes in the evolution of animal communication. This is particularly evident in insect warning signals, where toxic prey indicate their unpalatability to predators using conspicuous signals. These can be vivid colour patterns, pungent odours, or rattling sounds, but most often, insect combine two or three of these into a multisensory display. Predators learn to avoid these signals to reduce their toxin intake, and many studies have shown that insect warning signals are designed to be particularly effective in the avoidance learning process. However, one critical aspect of predator avoidance learning that has been omitted by current theoretical and empirical analyses of warning signals, is that of the defence chemistry itself. This is a complex issue. Although insects store toxins internally, many also secrete chemicals when attacked by a predator. These secreted chemicals may or may not be toxic. We need to know how birds perceive and learn about these chemicals in order to predict how warning signals and defence chemicals function in the real world. Perhaps more importantly, knowing how birds process this information in their foraging decisions will provide basic knowledge for the development of avian repellents for the agriculture industry. Our existing research has already shown that multiple defence chemicals can have a significant effect on the learning process in avian predators. However, we have been unable to separate the different interacting effects between internal toxins and distasteful external chemicals. We have established a new protocol by which we present birds with a sequence of prey which can be edible or chemically defended, and use taste and visual signals to signal their toxicity. Our aims are to: 1. Establish that birds can learn to use taste signals to indicate internal toxin; 2. Test whether taste signals enhance the association between toxicity and visual signals. Answering these questions will provide essential data about associative learning. There is a significant body of work in the experimental psychology literature concerned with taste-toxin associations, and also whether taste can enhance colour aversion learning after a single encounter. We build on this to look at how these processes work when animals have to discriminate between different stimuli, and in particular how interactions between taste, toxin and colours affect asymptotic avoidance rates. This is important for testing current models of warning signal evolution, since asymptotic avoidance rates are likely to be a significant selection pressure exerted by predator psychology on prey survival. Specifically, we will use our data to re-evaluate mathematical simulations of mimicry and warning signal evolution, since the use of taste signals make new predictions about the stability and evolution of insect communication. In addition, we will also make testable predictions about the evolution of insect defence chemistry, and for the first time bring a psychological perspective to an ecological problem. Our work studies basic cognitive processes in an adaptive context. The results will have a significant impact on our own field of receiver psychology and signal evolution, but also be of wider interest to researchers who work on brain and behaviour at multiple levels, for example cognitive and systems neuroscientists. The data are also important for the development of avian repellents for the agricultural industry, where seed eating by birds inflicts millions of pounds worth of damage annually. This systematic study of avian gustatory abilities will be the first of its kind. Using this new data in association with visual signals could be an important step in producing more safe and effective deterrents.
Committee Closed Committee - Animal Sciences (AS)
Research TopicsX – not assigned to a current Research Topic
Research PriorityX – Research Priority information not available
Research Initiative X - not in an Initiative
Funding SchemeX – not Funded via a specific Funding Scheme
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