The Importance of Major Predators on the Nesting Bahavior of Lepomis Macrochirus, Bluegill Sunfish
Bellware, Michael S.
Many seemingly unrelated species share common traits within their reproductive strategies. One of those strategies found multiple times throughout different organisms is a breeding behavior know as colonial nesting. The onset of colonial nesting in the avian community has long been believed to be a result of predation and ephemeral food supplies. Only in the past few decades has the colonial nesting behavior of fish been actively researched. One species in particular, the Bluegill sunfish (Lepomis macrochirus) is found to primarily breed in colonial aggregations. L. macrochirus is also known to neither feed its young nor leave the nest to find food while it still has young. This behavior rules out the notion that social foraging is a determining factor in colonial nesting for this species. Furthermore, research has not been able to completely confirm anti-predation behavior as the sole reason for colonial nesting in Bluegill. However, the most commonly held theory is that L. macrochirus nest colonially to aid in anti-predation measures and those individuals that nest solitarily will therefore face higher predation pressures (Gross and MacMillan, 1981). This study consisted of using a variety of observational behaviors such as attacks, defenses, and neighbor chases to test this currently held hypothesis on why L. macrochirus nest colonially. The result of this experiment was that the theory of solitary nesting fish experiencing higher predation pressure than colonial nesting fish did not hold true for our experimental situation. Additionally, these results might also lead to a hypothesis that habitat plays just as important a role in driving L. macrochirus to coloniality as does predatory pressure.
iii, 28 p.
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