Written by: LIZ LANGLEY
During the autumn estrus, a male elk emerges from the bushes of the Alaskan tundra.
摄影：JOHN EASTCOTT、YVA MOMATIUK，NAT GEO IMAGE COLLECTION
The season has entered autumn. For humans, this usually means huddling indoors in anticipation of the upcoming holidays. For many animals, however, this is a season to hurry up and prepare for the approaching winter.
As the days get shorter, many species, whether deer, birds or bears, begin to go into frenzied food gathering, mate hunting, and so on.
Studying this behavior of wild animals helps scientists understand how they respond to environmental challenges — such as cold temperatures , and how this ability to adapt can help them cope with future harsh environments, such as rising temperatures due to climate change.
Whenever the leaves start to fall, the following animals enter a state of winter preparation, let's take a look.
Deer in heat
For members of the deer family, including its largest species, the moose, it means that the mating season has arrived. From September to mid-October, male moose, which usually move alone (throughout the northern United States, Canada, Alaska, and northern Europe), look for other males to fight and compete for opportunities to get close to the female.
The surge in testosterone causes the soft, furry skin covered on the moose antlers to fall off, turning the antlers into sharp weapons for combat.
moose
Species: Mammals
Diet: Herbivores
Group Name: Group
Average life expectancy in the field: 15-20 years
Dimensions: shoulder height 1.5-2 meters
Weight: 816 kg
Population trends: increasing
IUCN Red List Status: Non-Threatened Species
A nearly 40-year study by researchers in Denali National Park in Alaska found that males who won courtship battles, often the largest and highest-ranking, were responsible for 88 percent of mating behaviors.
Female moose give birth to cubs in the spring, usually starting in late May.
Birds resting
When birds fly south for the winter, several species of birds make stopovers.
For example, after leaving the Pacific Northwest and Midwest, black-necked catfish flock to Lake Mono in California and Great Salt Lakes in Utah, where they forage for food and moult. Other birds that rest on their migration include the Freud gull, which stops in the Great Plains, the wooden duck that stays in the Great Lakes watershed, and the red-bellied sandpiper and other shorebirds that stop at various beaches.
In New Mexico, a black-necked mantle with breeding feathers swims around a lake.
摄影：TIM FITZHARRIS，MINDEN PICTURES/NAT GEO IMAGE COLLECTION
The red-bellied sandpiper migrates back and forth between the Arctic and the Southern Hemisphere each year, flying 2,400 kilometers non-stop, then stopping to rest, eat and molt, and they return to the same place each year to rest.
A bear with strong resilience
Every autumn, North American bears are busy "overeating", eating as much as possible to gain weight and spend the long winter hibernation.
While chronic obesity and lack of exercise have serious health consequences for humans, a recent study in the journal Biological Communications found that during the fall and winter, grizzly bears undergo different regulation of their genes to cope with such somatic changes.
In the Yukon region of Canada, a grizzly bear bites a freshly caught salmon.
摄影：PETER MATHER，NAT GEO IMAGE COLLECTION
For example, during hibernation, grizzly bears' genes are expressed in ways that reduce sensitivity to insulin, so their blood sugar remains at normal levels and can be used by the brain during prolonged sleep.
Joanna Kelley, an evolutionary geneticist at Washington State University and co-author of the study, points out that this also allows the large mammal to metabolize fat during hibernation, which is not possible for resting humans.
Gluttonous ladybugs
Mike Raupp, an entomologist at the University of Maryland in the United States, said there are nearly 5,000 species of ladybugs worldwide, and as autumn approaches, many ladybugs will "eat thousands of aphids and soft prey," such as the colorful Asian seven-star ladybird that invaded North America. After a big meal, the ladybugs will gather together, sometimes in groups, and then go into hibernation, waiting for the end of the long winter.
Ladybugs like to hide in crevices in rocks that expose the ground, but sometimes they also congregate on either side of people's houses, and they may think of the sides of the house as "a huge rock face," Raupp quipped.
This flock of ladybugs is often overlooked by predators, but if a hungry animal spotes one of the groups without noticing its bright warning color, the ladybug may resort to reflexive bleeding tricks. Stinking hemolymphs, or insect blood, seep out of his "knees" and make disappointed predators gag, he said.
"Hibernating" birds
While other birds are busy flying south for the winter, the North American Nighthawks of Western North America and Mexico are in their nests.
These nocturnal beings are the only birds known to enter a "hibernating" state. During "hibernation," the North American nighthawk can lower its body temperature to 41°C.
In British Columbia, Canada, a North American nighthawk blends in with its surroundings.
摄影：JARED HOBBS，ALL CANADA PHOTOS/ALAMY
North American nighthawks "hibernate" on the ground, and their mottled brown camouflage makes them nearly invisible. Mark Brigham, a biologist at the University of Regina in Saskatchewan, said that just like mammals, north American nightingales weighed their highest levels before entering a "hibernating" state.
In the study conducted in Arizona, Brigham found that the dormant North American nighthawk faces southwest, so the afternoon sun may help them warm up as a supplement to their body's metabolism, he said.
Brigham collaborated with people on a study that was published this year in the journal Ecology. The study found that the average "hibernation" time for North American nighthawks was around 5 days, but one of the particularly "sleepy" North American nighthawks slept for 45 days.
(Translator: Stray Dog)
Source: National Geographic Chinese Network (Official V)