Scared fish get lazy, and lazy fish get fat

  • Johansson F
  • Andersson J
  • 81


    Mendeley users who have this article in their library.
  • 36


    Citations of this article.


1. Many biological textbooks present predator-induced morphological changes in prey species as an example of an adaptive response, because the morphological change is associated with lower predation risk. Here we show that the adaptive morphological response observed in many systems may actually be an indirect effect of decreased activity - which reduces the predation risk - rather than a direct adaptive response. 2. One of the classical examples comes from crucian carp, where the presence of pike leads to a deeper body. We manipulated pike cues (presence and absence) and water current (standing and running water) and found that both standing water and pike cues similarly and independently induced a deeper body. 3. Since the presence of pike cues as well as standing water might be associated with low swimming activity, we suggest that the presence of pike causes a reduction in activity (antipredator behaviour). Reduced activity subsequently induces a deeper body, possibly because the energy saved is allocated to a higher growth rate. 4. Our result suggests that even if morphological change is adaptive, it might be induced indirectly via activity. This important conceptual difference may be similar in many other systems.

Author-supplied keywords

  • Adaptation
  • Anti-predator behaviour
  • Body shape
  • Induced defence
  • Phenotypic plasticity

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document


  • Frank Johansson

  • Jens Andersson

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free