Evol Ecol Res 10: 351-371 (2008)     Full PDF if your library subscribes.

Should I stay or should I go? Optimal parental care decisions of a nest-guarding fish

Geoffrey B. Steinhart,1* Erin S. Dunlop,2# Mark S. Ridgway3 and Elizabeth A. Marschall1

1Aquatic Ecology Laboratory, Department of Evolution, Ecology and Organismal Biology, Ohio State University,Columbus, Ohio, USA,  2Department of Zoology, University of Toronto, Toronto, Ontario, Canada and  3Ontario Ministry of Natural Resources, Peterborough, Ontario, Canada

Address all correspondence to G.B. Steinhart, Department of Biological Sciences, Lake Superior State University, 650 W. Easterday Avenue, Sault Ste. Marie, MI 49783, USA.
e-mail: gsteinhart@lssu.edu


Background: Parental care generally increases offspring survival but, for the parent, providing care can reduce adult growth and survival. Therefore, a trade-off exists between investments in current or future reproduction, and populations with different demographics and selective pressures may have different thresholds for when and how much care they provide.

Question: How variable are different populations of smallmouth bass Micropterus dolomieu in their willingness to provide care for small broods? What factors are most important in determining optimal brood abandonment thresholds?

Methods: We used dynamic programming to explore how adult and juvenile survival, brood predation, probability of nest success, angling pressure, and parental care costs affected brood abandonment thresholds.

Results: Adult annual survival was the most significant factor in determining optimal parental care decisions. Abandonment was less likely when adult annual survival and offspring daily survival were low than when survival was high. High parental care costs led males to abandon larger broods. Factors varying with parental age (e.g. adult survival or cost of providing care) were more important in determining abandonment behaviour than age-independent variables (e.g. offspring survival or probability of nest success) in part because of the larger brood sizes for older, larger males. Increasing angling pressure, storms or nest predators increased abandonment thresholds, but to differing degrees.

Keywords: dynamic programming, expected fitness, nest abandonment, nest defence, parental care, round goby, smallmouth bass.

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