Multi-camera field monitoring reveals costs of learning for parasitoid foraging behaviour

1. Dynamic conditions in nature have led to the evolution of behavioural
traits that allow animals to use information on local circumstances and
adjust their behaviour accordingly, for example through learning. Although
learning can improve foraging efficiency, the learned information can
become unreliable as the environment continues to change. This could lead
to potential fitness costs when memories holding such unreliable
information persist. Indeed, persistent unreliable memory was found to
reduce the foraging efficiency of the parasitoid Cotesia glomerata under
laboratory conditions. 2. Here, we evaluated the effect of such persistent
unreliable memory on the foraging behaviour of C. glomerata in the field.
This is a critical step in studies of foraging theory, since animal
behaviour evolved under the complex conditions present in nature. 3.
Existing methods provide little detail on how parasitoids interact with
their environment in the field, therefore we developed a novel
multi-camera system that allowed us to trace parasitoid foraging behaviour
in detail. With this multi-camera system, we studied how persistent
unreliable memory affected the foraging behaviour of C. glomerata when
these memories led parasitoids to plants infested with non-host
caterpillars in a semi-field set-up. 4. Our results demonstrate that
persistent unreliable memory can lead to maladaptive foraging behaviour in
C. glomerata under field conditions and increased the likelihood of
oviposition in the non-host caterpillar Mamestra brassica. Furthermore,
these time- and egg-related costs can be context-dependent, since they
rely on the plant species used. 5. These results provide us with new
insight on how animals use previously obtained information in naturally
complex and dynamic foraging situations and confirm that costs and
benefits of learning depend on the environment animals forage in. Although
behavioural studies of small animals in natural habitats remain
challenging, novel methods such as our multi-camera system contribute to
understanding the nuances of animal foraging behaviour.