Shift in red fox, Vulpes vulpes, mating system associated with El Niño in the Bering Sea

• Main Authors: Cynthia Jane Zabel, Spencer James Taggart
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Bering Sea; Round Island; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.165.4518; http://www.fs.fed.us/psw/publications/zabel/zabel7.pdf

Abstract. Fifteen reproductive groups of red foxes were observed on Round Island, Alaska during five field seasons. Polygyny occurred among these foxes, correlated with abundant food resources. The predictions of the polygyny threshold model were supported, i.e. polygynous females had equal or better reproductive success than monogamous females. However, beginning in 1982, widespread nesting failure of seabirds occurred (the primary prey item of the foxes), corresponding with the occurrence of El Niño in the Bering Sea. This change in food resources apparently caused red foxes to switch their diet from the most abundant to rarer prey species, and caused a shift from facultative polygyny to monogamy within this population. The polygyny threshold model was first developed to expain the evolution of avian mating systems (Verner 1964; Willson 1966; Orians 1969). This model predicts that the polygyny threshold is reached when a female pairing with an already mated male experiences reproductive success that is equal to or greater than a female pairing with an unmated male. The cost of sharing a male with a second female may be exceeded by the benefits which include occupying a superior territory, mating with a superior male, or cooperatively rearing offspring with another female (Emlen & Oring 1977; Wittenberger & Tilson 1980). Shifts from monogamy to facultative polygyny among avian species have been documented under ecological conditions predicted by the polygyny threshold