The Evolution of Dilution
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Transcript The Evolution of Dilution
The Evolution of Dilution
Andrew Paitsel
Allen Patton
Co-evolutionary Arms Race
• Predator/Prey Survival Adaptions
– Faster prey = faster predators
– Better eyesight = better camoflauge
• Other Survival Adaptations
- Warning calls
- Mobbing behaviors
- Traveling in herds (Dilution Effect)
Questions to Address
• What is the Dilution Effect?
• What are the advantages/disadvantages?
• What species has practiced this trait?
• What is the Selfish Herd theory?
• How does it affect the population?
• What other ways do animals behave due
to predation?
Dilution Effect
the assumption that everyone has an
equal chance of survival while in large
groups due to the fact that no individual is
being singled out by a predator.
Advantages
More eyes watching out for predators
Predator not being able to choose the
easiest prey
Prey species spend more time foraging
instead of scanning for predators
The frequency of scans as a result
of relative danger
Bednekoff et al, 1998.
Disadvantages
• More likely to be seen by predators
• More competition over resources
• More competition over mate selection
Examples
Stotting
Stotting
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Alarm signal hypothesis
Social cohesion hypothesis
Confusion effect hypothesis
Pursuit deterrence hypothesis
Disadvantages of Stotting
• Time Cost
• Energy Cost
• Survivorship Cost
The Selfish Herd
• Competition for safer positioning within the
herd.
– Middle position has overall higher survival
probability that individuals on the outer parts
– Increasing your overall fitness at the expense
of others
Future Research
Determine if traveling in herds is a learned
or genetic trait
Look into how predators counteract the
Dilution Effect
Is stotting a learned or inherited trait
Continue to evolve until
someone gets the upper hand
References
• Alcock J. 2005. Animal Behavior: An Evolutionary Approach. Sinauer
Associates, Inc. 8:176-199
• Bednekoff P.A., Lima S.L. 1998 Re-examining safety in numbers:
interactions between risk dilution and collective detection depend
upon predator targeting behaviour. The Royal Society. 265:20212026
• Caro T.M. 1986. The Functions of Stotting in Thomson’s Gazelles:
some tests of the predictions. Animal Behaviour. 34(3):663-684
• Caro T.M. 1985. Functions of Stotting. Animal Behaviour. 34(3):649661
• Cresswell W., Jakobsson S., Kaby U., Lind J., Quinn J.L. 2003.
Animal Behaviour. 66:643-648
• Garay J. 2008 Cooperation in defence against a predator. Journal of
Theoretical Biology 257:45-51
References Cont.
Pictures
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