Porter et al 1975

Environmental Constraints on some Predator-Prey Interactions

Pp347-364 in Perspectives of Biophysical Ecology, edited by

David Gates and Rudolf Schmerl

Springer, NY

 

Read pp 347-353 in detail, and look carefully at the graphs.  Answer the questions based on what information you derive from the graphs themselves, not what the author says he thought he saw in the graphs.

 

  1. How do the energy flow patterns shown in the diagram in Fig 20.2 related to the equation on p 349?  Are all of the same items in both?  Are there any items in the graph that are not in the equations?
  2. What does Fig 20.3 tell you about the environment for desert iguanas in mid summer (July 15)?  Why are the animals in their burrows except around 8am and 6 pm?  What specific information in the graph led you to your conclusion?
  3. How does Fig 20.4 relate to Fig 20.3?  Can you see if any part of Fig 20.4 is derived from Fig 20.3?  The axes on the graphs are different, but in some sense they are plotting similar information.  How does that work?
  4. Based on Fig 20.5, are observed patterns of behavior consistent with the predicted pattern of body temperatures at different times of day and different seasons?  How did you decide, using the data in the graph?
  5. Fig 20.6 is an analysis of the potential overlap in activity and habitat between lizards (predators) and ants (prey).  Based on the figure, what time of year would the ants likely be at the greatest risk of predation?  Why is the risk greatest at this time?  What information in the figure led you to the conclusion?
  6. Our discussions of predator prey interactions and competition in this class generally assumed that population densities were the only factors influencing the rate of predation or competition.  We distinguished extrinsic factors like rainfall (in examples like the Andrewartha Thrips study) from density dependent factors like predation and competition.  After reading this paper, have your views on the importance of density independent (weather/climate) and density dependent (predation/competition) factors changed?  If so why, if not, why not?