FEEDING ECOLOGY OF A GENERALIST PREDATOR, THE CALIFORNIA KINGSNAKE (LAMPROPELTIS CALIFORNIAE): WHY RARE PREY MATTER

We studied the feeding ecology of California Kingsnakes (Lampropeltis californiae) based on stomach contents of 2,662 museum specimens, 90 published records, and 92 unpublished observations. These snakes typically are diurnal, wide-foraging generalists and ingest prey head-first. Twenty-nine percent of 447 diet items were mammals, 29% were snakes, 25% were lizards, 11% were birds, 4% were squamate eggs, 1% were unidentified squamates, and 1% were amphibians. We detected no differences in diet based on kingsnake sex or color pattern, nor evidence of individual specialization. Rodents, lizards, and birds were eaten more frequently by larger individuals; snakes were eaten with similar frequency independent of predator size. Predation on mammals, birds, and lizards, but not snakes, was seasonally restricted. Kingsnakes from arid bioregions consumed more snakes, fewer rodents, and fewer lizards than did those from non-arid bioregions. Overall frequencies were similar for rodents and snakes, yet snakes accounted for 45% of prey biomass; among snakes, rattlesnakes comprised 24% by frequency and 37% of snake prey biomass and energy. Prey-predator mass ratios averaged 0.24 +/- 0.19 (range 0.01-0.73; n = 43); a positive relationship exists between prey mass and snake mass, but larger snakes also consumed small prey items. Rattlesnakes, amounting to only 7% of overall diet and 16% of total biomass and energy value, are available throughout the active season and provide higher payoff per item than other diet types. Our findings thus provide a resolution to the paradox that this generalist predator is specialized (i.e., venom immunity) to feed on rattlesnakes, a rare prey type.