Jm. Fedriani et A. Travaini, Predator trophic guild assignment: The importance of the method of diet quantification, REV ECOL, 55(2), 2000, pp. 129-139
We quantitatively assessed the effect of three Methods of Diet Quantificati
on (MDQ) (based on frequency of occurrence of prey, dry weight of prey rema
ins, or estimation of fresh biomass ingested) on guild classification of th
ree carnivores species based on five data sets. Diet dissimilarity matrices
and recognition of trophic guilds were dependent on MDQ. Both omnivorous (
Red Fox, Vulpes vulpes, and Eurasian Badger, Meles meles) shifted to differ
ent trophic guilds depending of the MDQ chosen, whereas Iberian Lynx (Lynx
pardinus) remained consistently in the rabbit-eating guild. As a way to ass
ess the pervasiveness of inconsistencies in guild classification, we applie
d our approach to six other predator assemblages. The number of recognized
guilds shifted as a result of MDQ in 4 of 6 comparisons, changes in guild m
embership occurred in all assemblages, and mean percentage of guildmate fid
elity was only 30 % (1SD = +/-21, n = 6). The choice of MDQ depends on the
specific ecological question to be addressed with the data. When investigat
ors focus on the effects of prey on predators, an estimate of biomass inges
ted seems the best choice, but when the focus is on the effects of predator
s on prey, an approach based on prey numbers is more appropriate.