Inspection behaviour and inter-individual cooperation in juvenile qingbo: the effects of prior predator exposure and food deprivation

The predation pressure and food availability to which individuals are exposed during their life histories shape inspection behaviour in animals. In this study, we aimed to test whether such behaviours varied with prior experience (predation, starvation or both treatments) or measurement condition (with or without the presence of a predator; here, the snakehead fish, Channa argus) in the fish species Spinibarbus sinensis, known as qingbo. Unexpectedly, prior predator experience showed no significant effect on inspection behaviour as demonstrated by either the frequency or the duration of each activity outside shelter or on cooperation as demonstrated by the inter-individual distance or synchronization of speed. This may have been due to the different adjustments in behaviour among individuals (more shelter use vs. more inspection), the predator treatment used in the present study (exposure to caged predator rather than direct predation) and/or a species-specific strategy in the qingbo. The starved fish displayed shorter inspection latency, increased inspection behaviour and greater cooperation when measured without the predator; however, when measured in the presence of the predator, the starved fish showed increased inspection frequency but shorter inspection duration, possibly due to the compromise between energy needs and predation risk. Similar to those of the predation group, the fish from the double-treated group showed no difference in inspection behaviour compared to the control group under the predator-absent condition, while the high-frequency, short-duration inspection behaviours remained the same as in the starved group. These findings suggested that the adjustment of inspection behaviour and related cooperation are rather complicated according to either predator experience or food deprivation, partially due to the inter-individual differences in behavioural adjustment and/or different environmental conditions.