Talk:Functional response

Discussion

The functional response is an important concept in ecology, however, the definition given in the introduction here ("the relationship between prey and predators") is at best too vague. I propose: "the relation between the number or density of prey and the number of prey consumed per predator per unit of time". Actually "prey" and "predator" should be replaced by "resource" and "consumer". This definition is equivalent to the ones found in textbooks, e.g. the one by Begon, Harper and Townsend and in Peter Yozis' Introduction to Theoretical Ecology. OpenScience (talk) 11:13, 24 December 2009 (UTC)

Okay, I have rewritten quite a bit of the article: the introduction, Type I and Type II, and will probably also edit Type III soon. I hope previous authors are okay with this, if not let me know here, we can probably come to an agreement that makes everybody happy. My main point of improvement is that the functional response is now not presented as a response of predators to prey, but more generally as one of consumers to resources. I want to replace the figure with three new figures, one for each type, with asymptotes. The article already covers the main things to be said about the functional response, so improvement would best come form better style etc. not so much from covering more aspects. Or did I forget something important? OpenScience (talk) 01:28, 27 December 2009 (UTC)

I think "dome-shaped" (sometimes also called "type IV") and "rollercoaster" FR should be mentioned shortly at the end of the article. See ref's: Jeschke et al 2004 Biological Reviews, Jeschke and Tollrian 2005 Oikos, Vucic-Pestic 2010 Pedobiologia, Bressendorff and Toft 2011 Biology Letters and many more. For a better understanding this should be included in the conceptual figure. Unfortunately, I really don't have any time left for this at the moment. Cheers, Wurstendbinder (talk) 16:06, 6 May 2012 (UTC)

I agree, type IV should be included. The defining features would be first increasing, then decreasing. The increasing would probably have to be at a decreasing rate, so that the first part of the curve is not sigmoid. An example would be f(R) = R/(aR^2 + bR +c). I recently published a paper with this equation as a light-response curve with photoinhibition (p-I curve, the rate of photosynthesis as a function of light). This may cause alternative stable states. Read if you like: Gerla et al. 2011, Oikos: 120:359. OpenScience (talk) 19:49, 10 November 2013 (UTC)

Somebody added a paragraph about ratio dependence to end of the section about Type II. Although a section about ratio dependence might be useful, I don't see why it would go under Holling's Type II. I also don't see why it is contrasted with the Lotka-Volterra model (which uses Type I, by the way). Since the author did not justify his contribution here on the talk page, I will remove it. OpenScience (talk) 20:14, 10 November 2013 (UTC)

Somebody added a paragraph about prey switching to end of the section about Type III, including an equation without any explanation. This is not the way to go. Please make sure when adding text to put it under the right heading, and create this heading if it is not there yet. Then, about the added text itself: "When all prey species are at equal prey densities, the predator will indiscriminately select between prey species. However, if the density of one of the prey species decreases, then the predator will start selecting the other, more common prey species with a higher frequency." Why would the predator do that? This reasoning is at best incomplete. I think optimal foraging theory (which assumes a predator maximizes its energy (or maybe nutrient) intake per unit time) predicts that a predator should drop a less nutritious prey form its diet if the density of the more nutritious prey rises above a threshold, because then the predator better not waste time handling the less profitable prey while it could be hunting for the more profitable one. OpenScience (talk) 11:20, 11 April 2014 (UTC)

Type IV responses

The math biol literature contains references to "Type IV" responses, but I am not sure how familiar regular ecologists will be with that one.137.205.183.31 (talk) 11:16, 22 July 2016 (UTC)

Type II is not an hyperbola

In the Type II section, it reads "Type II functional response is often modeled by a rectangular hyperbola, for instance as by Holling's disc equation[2], ..." with reference to Holling, C. S. (July 1959). "Some characteristics of simple types of predation and parasitism". The Canadian Entomologist. 91 (7): 385–98. doi:10.4039/Ent91385-7. S2CID 83738084.

I believe this to be wrong. The equation is not an hyperbola, or at least I couldn't re-arrange it to look like one. The reference also does not explicitly states that Type II is the equation of an hyperbola.

I suggest this sentence to be checked and either: 1) be removed; or 2) add how to re-arrange the equation to look like an hyperbola (which I don't think it's possible). Emilio.Berti (talk) 05:59, 11 July 2024 (UTC)