Abstract

Cannibalism is common in species which have overlapping and discrete life stages. Copepods are a typical example of the type of species which exhibit adult cannibalism of juvenile life stages. The scale of observation typically used in cannibalism studies may allow misinterpretation of the results. I used populations of Diaptomus leptopus from six independent ponds to determine the effects of body lengths of cannibal and prey, length asymmetry, and scale of observation on cannibalism rate. Five adults and 25 one to three day old nauplii were placed together in 50 ml of water for 12 hours. Separate treatments were run for each sex. Cannibalism rates ranged from 0.000 to 0.053 prey · cannibal -1 · hour -1 and were significantly different between sexes and ponds. Length asymmetry was the most accurate predictor of cannibalism rate but most of the predictive power came from adult length. Results from large scale observations, while seemingly robust, did not correspond well with results from small scale observations. The implication of scale of observation on interpretation of cannibalism studies is discussed.