Temperature-dependent interspecific interference alters pygmy backswimmer predation on water fleas

Co-occurring predators may compete for the same prey, with interactions
among them potentially modifying predator-prey dynamics. Although
predator-prey interactions are often studied in the context of direct
competition, less attention has been given to how non-competing predators
influence the foraging of other predators by their physical presence.
Abiotic factors like temperature also can shape such interactions by
influencing the behaviour of prey, predator, or other species occupying
the same space. This study investigates how increasing densities of a
non-competing predator – the water mite Arrenurus sp. – and increasing
water temperature (16°C and 25°C) affect the functional response of the
pygmy backswimmer, Neoplea striola, eating
juvenile Daphnia magna. The functional responses were Type II
across all treatments. Functional responses became shallower as water mite
densities increased at 25°C but not at 16°C, indicating
temperature-dependent interference from a non-competing predator. With no
water mites, however, the functional response was higher at 25°C than at
16°C, caused by higher space clearance rates at 25°C in the absence of
water mites. Handling times were lower at 25°C than at 16°C but were
unaffected by water mite density. The differences in parameters suggest
that the mechanism of inter-specific interference was through movement,
encounters, or capture success, rather than through post-capture
processing. This study showed how non-competing predators may affect
predator foraging, particularly at higher temperatures.