When learning the fundamentals of biology in school many years ago, I was taught that the rise of mammals was a direct result of dinosaurs dying out. Turns out that even the Jurassic forests were already full of squirrel-like creatures.
When recently a squirrel attacked and devoured an imperial moth in my yard, I searched the internet and found a couple of other examples of this behavior. Several observations of squirrels eating caterpillars and cocoons of silk moths were also sent to me by colleagues.
So, if small mammals similar to modern squirrels were already common 150-200 million years ago, at about the time when moths arose and diversified, why do we mostly view evolution of moth defenses such as cryptic and aposematic coloration through the prism of bird predation? Curious, fast-learning, diurnal and equipped with excellent vision, squirrels too are perfect predators, especially for large, resting by day, silk moths and hawkmoths. Squirrels also coinhabit tree trunk surfaces with these moths and would encounter them more readily than birds would. This week for example, for each bird I saw in the forest understory in San Felasco State Park in Gainesville, Florida, I saw 50 foraging squirrels, so they also can be quite common.
Squirrels are frequently described as omnivorous, eating not only vegetarian food, but insects, lizards, and nestling birds. According to Callahan (1993) squirrels are even known to stalk and take down larger prey. But how prevalent are large moths in squirrels’ diet today? Please send any observations of squirrels eating moths to firstname.lastname@example.org.
Here is a small sample of cryptically and defensively colored silk moths and hawkmoths:
Links and references:
Callahan, J.R., 1993. Squirrels as predators. The Great Basin Naturalist, pp.137-144.
Video: Florida Museum’s vertebrate paleontology curator, Jonathan Bloch, on evolution of mammals