Predator-prey interactions and the evolution of animal aggregation
This theme explores why animals live in groups (flocks, shoals and herds) particularly as a response to predation risk. Living in a group reduces an individuals chance of being eaten by a predator through a range of different mechanisms, which we explore using small shoaling fish such as guppies and sticklebacks, and theoretical (computer) models. Research projects under this theme include:
Confusion and oddity effects
A high density of individuals gives rise to visual confusion effects that reduce predation success (as predators are unable to ‘lock on’ to a target). One mechanism by which predators may counteract the confusion is by targeting individuals that are distinct from other group members, known as the oddity effect. We are currently looking understand how predatory animals search for and target prey by applying methods used by experimental psychologists to examine visual search behaviour in humans. In contrast to the role of oddity inpredator-prey interactions, the human response to unique items (targets) that differ from accompanying distractors is well understood.
Researchers: Khia Dobbinson, Helen Kimbell, Gwen Rodgers
Funding: University of Hull (2015-2018), University of Hull (2011-2015), BBSRC (2007-2011)
Mechanisms for aggregation in animals: the selfish herd
When many animals are frightened, perhaps because they detect a predator, they tend to bunch together tightly. This has been called the ‘Selfish Herd’ because each animal tries to reduce its chance of being captured by the predator by moving in between other individuals, and the best place to be is in the middle (which is selfish because it pushes others to the edge, where they are more vulnerable). But how can animals achieve this? By modelling different ‘movement rules’, we have shown that ecological variables (such as group size and density), the time at which predators attack, and the position of an individual within the group all influence the optimal movement rule for an individual. More recently, our empirical work with guppies indicates that they are most likely to be accounting for the position of multiple neighbours.
Researchers: Lesley Morrell & Helen Kimbell
Funding: NERC (2006-2010), University of Hull (2011-2015)
Forager responses to patch size, density and purity
Two opposing hypotheses predict how the density or purity of a resource patch affects its vulnerability to attack by a forager. The resource concentration hypothesis (RCH) predicts increased vulnerability in dense patches, while the resource dilution effect (RDE) decreasing vulnerability with increasing aggregation. This project seeks to understand how the density and purity of wheat crop patches affect attack rates by aphids and their parasitoids; how differences in forager traits impact on the forager’s response to the size, density and purity of a resource patch, and how the distribution of beans affects the behavioural choices of seed beetles.
Researcher: Catherine Carrick
Funding: University of Hull (2014-2017)