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On a beauty of a day in mid September, I shrugged all my computer and household chores and cruised to a big patch of bog blueberries. Alas, I'd waited too long. Most of the rich blue carpet of berries was already taken. By diligent searching, I finally gathered about a cup and a half of berries.

Judging from some cub-size footprints in the mud, I think a mother bruin and her family had helped themselves to the feast. Undoubtedly, some humans more prompt than I, had been there too. Maybe a flock of robins had passed through. Rodents had nibbled open some berries to extract the seeds. And quite a few fruits had simply fallen to the ground, uneaten by anybody.

So many fallen fruits were a rare sight back in the Midwest, where I studied wild fruiting plants years ago. There the waves of fall migrant birds usually wiped out the crops of pokeweed, spicebush, grapes, sassafras, dogwoods, and viburnums. The birds flew south during the night and foraged all day in the woods and hedgerows. Foxes, raccoons, and opossums got some too.

We don't get those huge waves of migrants here, not in such numbers. Even bears and human harvesters can't keep up with bumper crops of wild fruits in Southeast. So, especially in past years, I've seen unharvested, over-ripe salmonberries slowly sagging toward the ground. Or blueberries going soft and mushy, uneaten and no longer desirable. In years of good fruit crops, we seem to have more fruits than harvesters can use.

All those succulent fruits are designed evolutionarily to be eaten by vertebrate animals, which disperse the seeds after digesting the fruit. So fallen fruits represent a failed attempt at dispersal.

Somehow, plenty of seeds usually get dispersed, and we have a wealth of wild fleshy fruits, some common and widespread, others very localized or rare.

Among all those wild, fleshy fruits, almost all are sugary and more or less sweet; very few are packed with oily substances (a local example would be the white fruits of red-osier dogwood). Oils and fats are good nutrition for fruit-eating birds and mammals, and oily fruits are moderately common in the tropics. But why are oily fruits so rare here?

We also lack fruits with big seeds, such as persimmons or pawpaws, both of which are consumed by foxes and raccoons and sometimes bears in the southeastern part of North America. But there are foxes and coyotes, and of course bears, in Alaska. So the potential dispersal agents are here and something else must prevent big-seeded fruits from living here. But what?

The bright red fruits of bunchberry (a.k.a. dwarf dogwood) are common here and familiar to many local folks. But neither birds nor mammals seem to eat the rather pithy fruits, which sit on the plants for months and seldom appear in scats. Rodents sometimes open the fruit and extract the seeds, but that's death, not dispersal, for the seeds. How does this plant become so common if the seeds are seldom dispersed?

Mysteries remain, so there are lots of things still to learn. I love it!

• Mary F. Willson is a retired professor of ecology.