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| © Photograph by John Eastcott and Yva Momatiuk, Nat Geo Image Collection A male moose emerges from the bushes during fall rutting season on the Alaska tundra. |
It’s officially fall,
which for humans often means snuggling up inside and anticipating the
holidays ahead. Conversely, for many animals, it’s a season of intense
preparation for the looming winter.
From deer to birds to bears, many species are triggered by the
shortening days to switch into a frenetic mode of gathering food,
finding mates, and more. (See gorgeous pictures that celebrate the arrival of fall.)
Studying
such behaviors in wildlife can give scientists an insight into how
they’ve adapted to cope with environmental challenges—such as frigid
temperatures—and how such resilience can help them with future setbacks,
such as rising temperatures due to climate change.
Here are some species that go into overdrive when the leaves begin to fall.
Rutting deer
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| © Photograph by Tim Fitzharris, Minden Pictures/Nat Geo Image Collection An eared grebe sporting its breeding plumage swims on a lake in New Mexico. |
A rut usually means being stuck, but for members of the deer family—including its largest species, the moose—it means mating season.
From September to mid-October, males of the otherwise solitary moose—a
species that ranges across the northern U.S., Canada, Alaska, and
northern Europe—seek out other males to fight for access to females.
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| © Photograph by Peter Mather, Nat Geo Image CollectionA grizzly bear grips a freshly caught salmon in Canada's Yukon Territory. |
A surge in testosterone causes the soft, fuzzy skin covering on moose
antlers, called velvet, to shed, turning them into sharp weapons that
they’ll wield in battle.
Research spanning nearly 40 years in Alaska’s Denali National Park has found that these victorious males—usually the largest and highest-ranking—are responsible for 88 percent of mating events.
Females birth their calves in the spring, usually starting in late May. (Read about rare moose triplets spotted in 2018 in Canada.)
Resting birds
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| © Photograph by Jared Hobbs, All Canada Photos/AlamyA common poorwill blends into its surroundings in British Columbia, Canada. |
As birds fly south for the winter, several species take autumnal pit stops along the way.
After leaving the U.S. Pacific Northwest and Midwest, eared grebes,
for example, gather in great numbers to eat and molt at Mono Lake in
California and the Great Salt Lake in Utah. Other species that take rest
stops include Franklin’s gulls on the Great Plains, wood ducks on the
Great Lakes, and red knots and other shorebirds on various beaches. (See our amazing interactive map of bird migration.)
Red knots, which migrate annually from the Arctic to the Southern Hemisphere and back, will travel 1,500 miles at a clip and then pause to rest, feed, and molt at these places, faithfully returning to the same ones each year.
Resilient bears
In fall, North American bear species are busily engaged in a process called hyperphagia, eating and drinking as much as they can to gain weight for their long winter hibernation.
While people would suffer serious health consequences from an extended period of obesity and inactivity, a recent study in Communications Biology found that grizzly bear genes are regulated differently during fall and winter to cope with such physical trials. (Learn how hibernating bears keep weirdly warm.)
For
instance, during hibernation, their genes are expressed in a way that
reduces sensitivity to insulin, so that their blood sugar stays at a
normal level and is spared for use by the brain, which needs it during
the long sleep.
This also allows the big mammals to metabolize fat during hibernation, something resting humans can’t do, notes study co-author Joanna Kelley, an evolutionary geneticist at Washington State University.
Gluttonous ladybugs
There are around 5,000 species of ladybug, and many—such as multicolored Asian lady beetles,
which are invasive in North America—will “be fattening up on thousands
of aphids and soft-bodied prey” as fall approaches, says Mike Raupp,
an entomologist at the University of Maryland. After this banquet, the
insects will gather, sometimes in large masses, where they’ll enter a
dormant state to wait out the long winter.
Ladybugs prefer to
hunker down in the crevices of rocky outcrops, but will sometimes
congregate instead on the sides of people’s houses—thinking “that looks
like a wonderful, big rock face,” Raupp quips. (Read how without bugs, we’d all be dead.)
This
ladybug heap often goes unnoticed by predators, but should a hungry
animal discover one of these groups and not heed their bright warning
colors, the insects may turn to reflex bleeding. Smelly hemolymph, aka
bug blood, will seep out of their “knees” and give the disappointed predator a mouthful of yuck, he says.
'Hibernating' bird
While other birds are busy flying south for the winter, the common poorwill of western North America and Mexico is having a staycation.
These
nocturnal members of the nightjar family are the only bird species
known to go into a torpor, a similar state to hibernation, during which
the animals can bring their body temperature down to 41 degrees.
Poorwills
“hibernate” the way they nest—on the ground, where their mottled brown
camouflage renders them almost invisible. Like mammals, they’re at their
highest weight before they go into their torpor, says Mark Brigham, a biologist at the University of Regina in Saskatchewan.
In
his research in Arizona, Brigham has discovered hibernating poorwills
face the southwest, likely so the afternoon sun will help warm them as a
complement to their body's own metabolism, he says.
Brigham co-authored a study, published this year in the journal Oecologia, that found the average poorwill torpor is about five days—but that one especially sleepy bird slumbered for 45.
Give us the remote control—we’ll see if we can beat that time.
