Data from: Body condition reveals hidden correlations between co-infection and behavior in sunfish

The role of parasites in maintaining consistent inter-individual
differences in behavior (i.e., personality) is the subject of increasing
study and debate. While behavioral differences may expose individuals
differently to parasites, parasite infection can itself change host
behavior, sometimes favoring the parasite’s own transmission. Furthermore,
parasites can alter the functioning of energetically costly organs like
the brain, thus affecting cognitive performance. However, relationships
among infection, cognition, and behavior can be complex and difficult to
interpret, especially in wild populations where individual health status
is unknown. The inclusion of body condition as a fitness proxy may help
reveal relationships between parasites and host traits that are otherwise
masked. We examined relationships among host body condition, personality
(i.e., exploration, boldness), cognition (i.e., aversive learning), and
parasite density in wild-caught pumpkinseed sunfish (Lepomis gibbosus)
naturally infected with endoparasites. We measured exploration (i.e,.
surface explored in cm), boldness (i.e,. latency to emerge from shelter in
seconds) and cognition (i.e. aversive learning; difference between trial 1
and 2 in latency time to enter the black side). Exploration and boldness
were measured twice (trial 1 and 2). Cognitive performance had one
learning trial, and two test trials (24-hour delay between trials).
Exploration in an open field test was repeatable in sunfish. Boldness,
assessed using a shelter test, was not repeatable, but was correlated with
exploration. Host exploration decreased with both increasing parasite
density and decreasing body condition. Only individuals in relatively
lower body condition displayed a negative relationship between parasite
density and exploration, suggesting a pathologic effect of the parasites
on the sunfish. Aversive learning was not influenced by co-infection. Our
results show that body condition is important to consider when studying
wild populations as some patterns observed between parasite density and
host behavior were only revealed when body condition was taken into
consideration.