Data from: Natural enemy ecology: comparing the effects of predation risk, infection risk and disease on host behavior

1. Growing interest in unifying the field of natural enemy ecology has
revealed similarities between predation and parasitism. In parallel with
predation, parasite infection – and even the threat of infection – can
alter host traits and indirectly affect community interactions.
Nonetheless, few studies have considered multiple mechanisms of natural
enemy-induced behavioural alteration in parallel (e.g. effects before and
after enemy contact) or the factors that drive variation in behavioural
responses. 2. We first evaluated how the threat of infection by a virulent
trematode (Ribeiroia ondatrae) compared to the well studied risk of
predation in triggering inducible defences in amphibian hosts, prior to
direct contact with either enemy. We then evaluated five separate factors
that influenced the magnitude of parasite-induced behavioural changes
after successful transmission. 3. In both the laboratory and an outdoor
mesocosm experiment, we found no evidence that tadpoles of two species
(Pseudacris regilla and Anaxyrus boreas) altered their activity levels in
response to chemical cues from uninfected host snails, trematode-infected
snails, or from conspecifics actively becoming infected. In contrast,
tadpoles sharply reduced their activity in response to lethal predation
risks posed by caged dragonfly larvae. 4. After infection, however,
Ribeiroia caused strong decreases in host activity and escape distance
that correlated positively with infection intensity and negatively with
host size and developmental stage. Five days after infection with a
one-time pulse exposure, hosts recovered to near-normal activity levels.
Hosts exposed to a chronic daily exposure of equal intensity, however,
continued to decrease activity. Unlike Ribeiroia, two less virulent
trematodes had no detectable effects on host behaviour. 5. Our results
highlight key distinctions between predation and parasitism. The
contrasting effects prior to enemy contact may stem from the fact that
unlike predation, the consequences of macroparasite infection are
intensity-dependent and unpredictable. In contrast, the strong changes in
host behaviour after infection are more similar to non-consumptive
predator effects in terms of their potential influences on host fitness
and community interactions.