Data and code from: Prey detection by a stepwise visual template matching mechanism

Prey capture success by a predator can be improved by the formation of a
search image, and recent experience with a prey item provides a visual
template to which subsequent potential prey are compared. Following
observations of distinct trout feeding responses to drifting mayflies in a
large western U.S. river in the same month across two successive years, we
developed a set of experiments to test if changing ratios of sequentially
delivered prey of the same species but different body sizes caused a shift
in trout feeding response. We discovered that large-sized focal prey were
always consumed. Comparing predation on large- versus small-sized prey
(137% length difference), few small prey were consumed, but when comparing
large- versus medium-sized prey (99% length difference), all medium prey
were consumed. When small-sized prey, initially rejected, were compared
with the newly established medium-sized focal prey (57% length
difference), all medium and small prey were consumed. When trout
previously exposed to small prey were subsequently fed only large prey,
fish memory of the small prey lasted for at least 14 days. These results
provide evidence that predator search image formation for novel prey
requires a dynamic stepwise neural template matching process. We discuss
how this mechanism could be used by many consumers to optimize foraging,
with implications for predator and prey population dynamics, such as the
persistence of rare prey and its role in selection on prey phenology to
minimizes predation of different size classes, species, or both.