Summary
Localized antipredator behaviors have been observed in a wide variety of taxa. Recent work has also shown that animals that provide parental care adjust their behavior when faced with variation in offspring predation pressure. This variation in offspring predation pressure may also influence the antipredator behavior of offspring if improved antipredator behaviors can increase their probability of survival. We tested if a natural gradient in nest predation pressure influenced antipredator behaviors of larval teleost fish (smallmouth bass, Micropterus dolomieu). We examined the predator avoidance of wild larvae from 6 populations that differed in nest predation pressure, and we also compared the recovery from a simulated predator attack of 2 populations at the opposite extremes of predation pressure. We found that larvae differed in their ability to avoid the nest predator, but larvae from lakes of low predation pressure responded similarly to larvae from lakes of high predation pressure. Generally, older offspring were not significantly better at avoiding predators relative to younger offspring, but we found a weak and significant positive correlation between the size of young offspring and their predator avoidance behavior. The recovery from a simulated predation event varied relative to predation pressure. Larvae from the site of high nest predation pressure exhibited reduced rates of maximal oxygen consumption and recovered faster than larvae from the low predation pressure site. Thus, variation in nest predation pressure had little influence on the antipredator behavior of offspring, which are provided with parental care but may have important metabolic consequences.
Methodology
In the springs of 2008 and 2009, snorkelers surveyed the shoreline of 6 lakes on the Rideau River and Gananoque River systems (Upper Rideau Lake, Charleston Lake, Indian Lake, Newboro Lake, Opinicon Lake, and Sand Lake) in eastern Ontario, Canada, to locate smallmouth bass nests. Nests were individually marked using a numbered piece of polyvinyl chloride pipe. Experienced snorkelers estimated male total length (TL), (Suski et al. 2003) and these length estimates were later validated by catching some males by rod and reel (Suski and Philipp 2004, Gravel MA, unpublished data). Larger males attract larger females, which results in larger males receiving a greater number of eggs per mating (Ridgway, Shuter et al. 1991; Philipp et al. 1997; Hanson and Cooke 2009). Male and female size has the potential to influence offspring survival and behavior if larger parents produce larger offspring, which is closely linked to size-selective mortality and performance in juvenile fish (Sogard 1997) and thus must be considered in this study. These lakes were chosen based on their close proximity to each other (within a 50 km radius; Figure 1) and due to previously documented variation in nest predation pressure (Gravel and Cooke 2009). Bluegill (Lepomis macrochirus), pumpkinseed (L. gibbosus), yellow perch (Perca flavescens), black crappie (Pomoxis nigromaculatus), largemouth bass (M. salmoides), rock bass (Ambloplites rupestris), and conspecifics have all been documented as nest predators for smallmouth bass (Scott and Crossman 1973). Our work has shown that the nest predators in this system are almost exclusively L. spp., that nest predation pressure varies greatly among these lakes (Gravel and Cooke 2009) and that nest predation pressure is consistent across years (Gravel MA, unpublished data).