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Size-structured risk assessments govern Daphnia migration.

  • Lars-Anders Hansson
  • Samuel Hylander
Publishing year: 2009
Language: English
Pages: 331-336
Publication/Series: Royal Society of London. Proceedings B. Biological Sciences
Volume: 276
Issue: 1655
Document type: Journal article
Publisher: Royal Society

Abstract english

One of the more fascinating phenomena in nature is animal mass migrations and in oceans and freshwaters, diel variations in depth distribution of zooplankton are a phenomenon that has intrigued scientists for more than a century. In our study, we show that zooplankton are able to assess the threat level of ultraviolet radiation and adjust their depth distribution to this level at a very fine tuned scale. Moreover, predation risk induces a size-structured depth separation, such that small individuals, which we show are less vulnerable to predation than larger, make a risk assessment and continue feeding in surface waters during day, offering a competitive release from down-migrating larger animals. Hence, we mechanistically show that such simple organisms as invertebrate zooplankton are able to make individual, size-specific decisions regarding how to compromise between threats from both predators and UV radiation, and adjust their diel migratory patterns accordingly.


  • Ecology
  • ultraviolet radiation
  • Daphnia
  • zooplankton
  • migration
  • risk
  • predation


  • Centre for Animal Movement Research
  • ISSN: 1471-2954
Lars-Anders Hansson
E-mail: lars-anders [dot] hansson [at] biol [dot] lu [dot] se


Aquatic ecology

+46 46 222 41 69






Research group

Aquatic Ecology

Other projects I´m involved in

Doctoral students and postdocs

PhD students, main supervisor

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