Sex differences in the behavioural traits across ontogenetic stages in a sexually-size dimorphic spider

Selection acts differently on females and males due to differences in
potential reproductive rates, driving the evolution of sex differences in
traits, including growth and behaviour. Additionally, selection pressures
vary during an individual's ontogeny, with growth being crucial in
early developmental stages and reproduction during adulthood, leading to
age- and sex-specific behavioural strategies. In this study, we
investigated a sexually-size dimorphic spider, the raft spider (Dolomedes
fimbriatus), where females are substantially larger than males. We
repeatedly observed spiders from juvenile to adult stages, examining
boldness, voracity towards prey, and probability to attack. Our findings
revealed that females exhibited greater boldness, voracity, and
probability to back-attack the simulated attacker compared to males.
Notably, the observed behaviours changed during ontogeny, with sex
differences in the magnitudes and directions of change, indicating
distinct life history strategies between sexes. Moreover, we detected
positive associations between body mass or age and behavioural traits,
supporting a proposed positive feedback loop between assets and behaviour.
While mass and age were not significant confounding predictors in the
analyses of sex differences in behaviour, some collinearity was present
between sex, mass, and age, so that their effects on behavioural
differences between sexes cannot be conclusively disentangled.
Repeatability of behaviours was low but significant for boldness and
probability to attack, with similar estimates between sexes. These results
underscore the importance of considering sex-specific life history
strategies in behavioural trait studies.