the wind, scattering its seeds along the way. Wherever it
comes to rest, still more seeds are released.
Other plants are designed to have their seed dispersal
units, called diaspores, attach to an animal. Hooks,
barbs, burrs – even a sticky, adhesive surface or gluelike
substance – gets the job done. Sticking to an animal,
bracts hold tenaciously to fur. When pulled apart or
simply broken apart over time, the seeds are released.
The wood bison of Manitoba has a woolly coat that’s a
perfect attachment surface for the burdock’s hooks, and
a vast habitat through which he may travel and sow the
seeds. It’s no surprise, then, that in tallgrass prairie ecosystems, the bison is a species that profoundly shapes the
biodiversity of the land. Dozens of ingested forage plant
seeds are dispersed in bison droppings, and as many as 76
species of seed stowaways have been documented in hair
samples. Humans are good dispersers, too, as we know
from the seed hitchhikers found clinging to our boot
laces and wool trousers whenever we go afield.
Birds, of course, have famously mutualistic relationships with seeds. It’s believed that bright red and purple
fruits especially attract bird frugivores because they stand
out like signal flags directing the birds through a sea of
foliage to the foods they seek. While color is the “dinner
is served” attractant for avian seed consumers, mammals
key in on aromas wafting from ripe fruit. Here in our
woods, the omnivores – including raccoon, striped
skunk, opossum, fisher, American marten, red and gray
fox, coyote and black bear – are quick to indulge.
Black bears have particularly catholic tastes. When
analyzing the contents of their scat nationwide, I’ve
identified 56 plant species, and I’m certain that’s not
all. It’s no coincidence that so many fruits ripen when
bears gorge in preparation for hibernation, and birds
for migrations. For a short trip, the best option for seeds
is to book a flight with a bird; for a longer journey, the
mammals, especially the black bear, are the best travel
agents in town.
Last fall, I was scouting a friend’s property to look for
animal sign in an extensive wild orchard, which we’ve
been restoring for several years by releasing crown space
for hundreds of apples and hawthorns. Our work has
really yielded results – healthy, leafy branches and tons
of fruit for wildlife.
I have a soft spot for hawthorns, though their nasty
spines occasionally remind me of just how soft I am.
How can a bear, or any critter, possibly access the fruits
from these trees? I no sooner wrapped my mind around
the absolute impossibility of getting by the hawthorn’s
fortress of spines when, voila, I saw a big pile of fresh
bear poop full of brightly colored hawthorn seeds.
Susan C. Morse is founder and program director of Keeping Track in
The winged seeds of white ash (Fraxinus americana) are called samaras.
Young bull wood bison with burdock and thistle seeds in Manitoba.