Abiotic environmental factors contribute to spatial variation in boldness and exploration in guppies (Poecilia reticulata).

Research on wild fishes has tended to overlook the role of abiotic factors in shaping behaviours associated with boldness and exploration. This oversight could exist because small-scale variation in the abiotic environment might seem unlikely to influence such behaviours. We challenged this assumption through research in the Trinidadian guppy (Poecilia reticulata) system. We started by quantifying how behaviours associated with boldness (time in a shelter and time frozen in an open field) and a behaviour associated with exploration (number of grid squares crossed in an open field) varied for guppies within and among 15 pools across two streams, where all of the pools within a stream were within 150 m of each other. The measured behaviours differed little between streams, yet they varied dramatically among pools within streams and among individuals within pools, thus illustrating how such behaviours can be structured on very small spatial scales. We next assessed how the observed behavioural variation might be explained by individual-level attributes (sex and body mass) and pool-level abiotic factors (e.g. temperature and dissolved oxygen). Individual-level attributes explained little of the behavioural variation, although smaller guppies did display slightly bolder behaviour. Among-pool abiotic factors, however, were quite informative. As a clear example, guppies from pools with less dissolved oxygen displayed bolder behaviour and (possibly) greater exploration. Our results highlight the importance of abiotic factors in shaping behaviour even on small spatial scales.