Camouflage Comparisons among Fox Squirrels from the Mississippi River Delta

Populations of fox squirrels (Sciurus niger subauratus) from the delta of the Mississippi River include pale-agouti, dark-agouti, and nonagouti-black individuals. I tested the possibility that predation could maintain this polymorphism by measuring how well these morphs matched tree-bark backgrounds with respect to overall brightness (intensity), average size of brightness patches, and variation in sizes of brightness patches. Results indicated that pale-agouti morphs consistently are most cryptic and hence that static camouflage alone cannot account for the polymorphism. Either there must be an antipredator advantage for dark morphs when the squirrels are moving, or some other advantage to dark coloration that is unrelated to predation must counterbalance the advantage to pale-agouti coloration in static camouflage.