Resource manipulation reveals interactive phenotype-dependent foraging in free-ranging lizards

Recent evidence suggests that individuals differ in foraging tactics and
this variation is often linked to an individual’s behavioural type (BT).
Yet, while foraging typically comprises a series of search and handling
steps, empirical investigations have rarely considered BT-dependent
effects across multiple stages of the foraging process, particularly in
natural settings. In our long-term sleepy lizard (Tiliqua rugosa) study
system, individuals exhibit behavioural consistency in boldness (measured
as an individual’s willingness to approach a novel food item in the
presence of a threat) and aggressiveness (measured as an individual’s
response to an ‘attack’ by a conspecific dummy). These BTs are only weakly
correlated and have previously been shown to have interactive effects on
lizard space use and movement, suggesting that they could also affect
lizard foraging performance, particularly in their search behaviour for
food. To investigate how lizards’ BTs affect their foraging process in the
wild, we supplemented food in 123 patches across a 120-ha study site with
three food abundance treatments (high, low, and no-food-controls). Patches
were replenished twice a week over the species’ entire spring activity
season and feeding behaviours were quantified with camera traps at these
patches. We tracked lizards using GPS to determine their home range (HR)
size and repeatedly assayed their aggressiveness and boldness in
designated assays. We hypothesised that bolder lizards would be more
efficient foragers while aggressive ones would be less attentive to the
quality of foraging patches. We found an interactive BT effect on overall
foraging performance. Individuals that were both bold and aggressive ate
the highest number of food items from the foraging array. Further
dissection of the foraging process showed that aggressive lizards in
general ate the fewest food items in part because they visited foraging
patches less regularly, and because they discriminated less between high
and low-quality patches when revisiting them. Bolder lizards, in contrast,
ate more tomatoes because they visited foraging patches more regularly,
and ate a higher proportion of the available tomatoes at patches during
visits. Our study demonstrates that BTs can interact to affect different
search and handling components of the foraging process, leading to
within-population variation in foraging success. Given that individual
differences in foraging and movement will influence social and ecological
interactions, our results highlight the potential role of BT’s in shaping
individual fitness strategies and population dynamics.