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Náttúra og náttúrutilfeingi


Effects of flow, turbidity and prey distribution on prey detection by visual and olfactory predators


Ása Johannesen

Institute of Integrative and Comparative Biology, University of Leeds

Aðrir luttakarar:
Lesley Morell and Alison Dunn

2010 - 2013

Stuðul úr Granskingargrunninum:
691.901 kr.

Original: Predators regulate the population sizes of their prey and exert strong control over their ecosystems in many ways. However, predators can be divided into those that hunt by sight, and those that hunt by smell, with potentially very different hunting strategies – is there a fundamental difference in the way these two types of predator influence, and are influenced by, the ecosystems in which they live? Animals make extensive use of chemical information from the environment for behavioural decision-making relating to foraging, reproduction and the assessment of predation risk: mammalian predators seeking prey; vultures searching for carcasses; hummingbirds locating and discriminating among foods and tsetse flies searching for blood meals. In aquatic systems behavioural and morphological prey traits are often induced by exposure to waterborne predator cues. Aquatic predators that hunt via olfaction can exert large effects on whole communities, and so predator-prey interactions in both marine and freshwater systems are therefore often chemically mediated from individual to community levels. However, probably due to a bias towards vision in our own perception of the world, our understanding of the role of olfaction in predator-prey interactions lags far behind that of vision. This project will investigate how predators that can use olfaction to hunt are influenced by three ecological factors that affect the use and availability of olfactory cues, and the interactions between them. We focus on 1) a reduction in the availability of visual information through increased turbidity; 2) the distribution of prey in the environment, and therefore the way olfactory cues from multiple prey individuals interact; and 3) the movement of olfactory cues in still and flowing water, and how information is transported from prey to predator. We will investigate the ability of two different predators, three-spine sticklebacks and common prawns, to find prey under a range of ecological conditions. Sticklebacks are primarily visual predators, but are able to use olfaction when visual cues are lacking. Prawns are olfactory predators and by comparing the two, we will be able to understand the differing roles of vision and olfaction in prey detection. Human activities are causing unprecedented environmental change and fundamental questions in biology lie in understanding how animals respond to these changes. In aquatic systems, one key change is the loss of visual information through increasing turbidity. Organic pollution is almost ubiquitous in freshwater habitats associated with human settlements, and is of particular concern given the broad range of impacts on aquatic life. Our project will initially investigate how turbidity impacts on the foraging success of sticklebacks, and go on to look at how this interacts with factors that may increase the availability of olfactory information: prey distribution and water movement. Animals are rarely evenly distributed in the habitat: aggregation is a common phenomenon, and may be evolutionarily favoured for a numbers of reasons, including a relative decrease in the likelihood that predators can detect groups. For predators that use vision to detect their prey, there is a well established theory that a group of individuals is less detectable than the individuals would be if they were dispersed, something that has received extensive empirical support. For predators that use olfaction, however, there is little theory, and no empirical understanding of how predators detect groups. Our project will investigate the relationships between prey group size and predator detection for olfactory predators (prawns) and for visual predators (sticklebacks) as the availability of visual cues decreases through increased turbidity. Finally, in aquatic environments, the physical movement of water influences the structure of water-borne chemical plumes, and the reception of chemical signals by consumers. The physical processes governing the transport of chemicals have a profound impact on the nature and success of chemosensory-mediated behaviour. The ‘olfactory concealment hypothesis’ or the use of ‘sensory refuges’ suggest that in moving water or air, there are areas of flow where prey benefit from a reduction in the ability of predators to detect them. Our project will investigate how the movement of chemical cues from prey to predator affects how predators can detect their prey, whether areas of turbulence create sensory refuges and whether grouping within such refuges by prey animals negates any anti-predator benefit of using them. Overall, the project will test theories and hypotheses regarding the olfactory detection of prey groups, and the use of sensory refuges, which are previously untested or for which only anecdotal information exists. It will add to a growing understanding of the role of olfaction in predator-prey interactions, and provide the basis for future projects understanding the behaviour of both predators and prey in aquatic systems.



1. Scientific articles, books, thesis etc.
Thesis: Predator-Prey interactions in aquatic environments (2013)
Johannesen, A., Dunn, A. M., & Morrell, L. J. (2012). Olfactory cue use by three-spined sticklebacks foraging in turbid water: prey detection or prey location? Animal Behaviour, 84(1), 151–158. doi:10.1016/j.anbehav.2012.04.024

Talks given:
ASAB 2011: Short talk on how sticklebacks detect and locate prey in turbid water.
ISBE 2012: Talk on aggregation as an olfactory predator-avoidance strategy
Behaviour2013: Short talk on the major findings from this project

2. Other results, such as unpublished articles, patents, computer systems, original models and new procedures:
Johannesen A, Dunn A, & Morrell LJ Prey aggregation is an effective olfactory predator avoidance strategy : Planned for Behavioural Ecology
Johannesen A, Dunn A, & Morrell LJ Detectability as a function of prey aggregation : Planned for Behavioural Ecology
Johannesen A, Dunn A, & Morrell LJ Turbulence lowers risk of detection of aggregated prey: Planned for Biology Letters Johannesen A, Dunn A, & Morrell LJ The use of lumpfish as cleaner fish on salmon farms: Planned for Applied Animal Behaviour Science

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