Stress affects different animals in different, but useful, ways

Chronic stress affects nearly all parts of the body

Stress is our body’s internal mechanism to deal with changes in our internal balance. As such, the stress response affects nearly every organ system through a cascade of both fast and slow hormonal changes. While short-term stress can be adaptive, long-term stress may cause serious health issues.

Stress evolved as a survival mechanism to keep humans alive

Stress activates the “fight-or-flight” response when we face threats. It’s triggered by the hypothalamus, which signals the release of adrenaline and cortisol, heightening awareness and energy. While acute stress helps in short bursts, chronic stress—persistent over time—can harm both physical and mental health, leading to conditions like hypertension, anxiety, or depression.

Fear (and stress) can be contagious via pheromones secreted by the body

While seeing someone else in a panicked state may induce a stress response, researchers have found stress can be literally contagious—chemicals contained in sweat and other secretions can trigger stress hormone release in others. Theories suggest this feature is an evolutionary adaptation to protect groups from danger.

The positives of feeling stressed

Worrying about past events and upcoming challenges is not a pleasant experience, but a reasonable amount of stress can bring a lot of good into our lives. In this episode of "The Happiness Lab" with Dr. Laurie Santos, two psychology experts offer tips for resetting one's relationship with stress. Listen and learn how to make stress a positive tool rather than a debilitating emotion.

Noise pollution from humans and technology alters animal behavior

Animals may experience chronic stress and health issues due to noise pollution, which often interferes with their mating sounds. Due to traffic, nightingales sing louder on weekday mornings, and birds near airports start singing earlier to avoid upticks in takeoffs and landings.

Stress is a response to external triggers, while anxiety is persistent and internal

When distinguishing the two, stress is a reaction to identifiable situations like deadlines or conflicts, and its symptoms fade when the stressor is gone. However, anxiety may jump from one worry to another over time without any apparent cause.

Zoo animals have developed allergies, too

Although scientists do not know if allergies manifest among wild animals—and if animals can survive with them—in a zoo setting, veterinarians have observed zoo animals with common allergy symptoms, including itchiness, crusty skin, and runny eyes. Veterinarians have identified Asian elephants with pollen allergies and at least one jaguar with an allergy to fleas.

Extreme heat is neurologically impairing animals

Dog bites increase in summer, birds struggle to learn, and goats pick more fights. Scientists are unraveling new details about how heat impairs animals' neurological systems.

Animals get SAD—especially those in zoos, like pandas

Giant pandas in locations outside their evolved latitudinal range (from southeast Asia to northern regions around Beijing) exhibit more sluggish behavior, even when they were born there. Researchers have observed that similar sensitivities to "photoperiods" (or time with light) impacts many animals, including birds, insects, and our pets. (Nautilus imposes a metered paywall.)

Environment and genetics explain why animals have widely different lifespans

Both environmental conditions and genetic factors shape how long various animals live. For some creatures, colder conditions allow for less energy use and slower aging. Larger animals have fewer predators. While humans don't live the longest, we are a rare species that successfully lengthened its average lifespan over time.

Some animals seem to live well on little sleep

African bush elephants typically sleep for about 2 hours per 24-hour day, coming in well under a human's recommended seven-hour minimum. Other animals also appear to skimp on sleep, by human standards, without the consequences humans associate with being sleep deprived. This academic article details the sleeping habits of animals that appear to thrive on fewer than 40 winks and explores whether their sleep processes are just built different.

Grief rewires the human brain

The human brain handles stress and emotional traumas similarly. In response to the emotional stress of a situation like the death of a loved one, divorce, or abuse, the brain may strengthen or weaken connections between nerves to form new neural connections. Over time, chronic stress can diminish brainpower, reducing overall nerve growth and memory to shift resources to enable elevated fear responses and enable humans to survive.

Increasing contact between humans and wild animals is driving zoonotic threats

Zoonotic diseases, which spread from animals to humans, present one of the most significant emerging threats worldwide. Scientists have identified around 200 viruses capable of infecting humans, and unfortunately, the number of such diseases are on the rise—at least 60% of all emerging infectious diseases are zoonotic in origin.

The adorable happiness of animals, in photos

Can animals experience happiness? And even if they do, do their bodies manifest happiness in similar ways to humans? Regardless, you surely will derive some happiness after viewing these thirty photos of a variety of animals appearing to smile big, beautiful smiles.

Why don't giraffes get hypertension?

The average blood pressure of a giraffe is about double that of a human, yet they don't suffer from the symptoms of high blood pressure that humans do: stiffening of the left heart ventricle, shortness of breath, fatigue, or swollen legs and ankles. This article explains how giraffes have evolved to have the "biological equivalent of support stockings."

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Humans aren't the only mammals who go through menopause, but it's rare in the animal world

While scientists are unsure how many mammals actually experience menopause, they do know for sure that humans aren't the only ones. Orcas and some toothed whales (like belugas and narwhals) go through menopause. And a recent study found chimpanzees also experience the condition, though it's late in life.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights

Dr. Martin Antony, a Canadian expert on phobias and anxiety, says that fears of creepy, crawly animals like snakes, spiders, and mice are particularly common.

The hormone that spreads love and helps fish share fear

Scientists consider emotions like fear and empathy to be among the oldest evolutionary behaviors observed in mammals. Yet to date, how these reactions are processed in the brain, regardless of species, is not well understood. A new study reveals how the chemical oxytocin—known as the "love hormone" in humans—helps let fish know when their friends are in danger.

Brain studies suggest some animals do dream (sort of)

Studies on sleeping cats, rats, fish, and finches show that their brains fire as if performing actions from waking life. Spiders and insects also have REM-like sleep. Whether these findings indicate that animals dream depends on one's definition of dreaming.

Porcupines, when threatened, go piloerect—essentially, they get goose bumps

If stressed, the animal appears to grow to about twice its normal size because it goes piloerect, which causes the quills to stand erect. If this intimidation tactic to avoid conflict doesn't work on the predator, the animal may get stabbed by the quills upon contact with the porcupine.

Mental health symptoms may manifest differently across cultures

Mental health, like physical health, is imbued with values, beliefs, and traditions. Symptoms of distress are not universal and may differ based on racial, ethnic, and cultural contexts. Because mental health may be stigmatized or communities may have varying belief systems about causes of mental health challenges and how to fix them, it may affect how symptoms manifest. Chest pain, for example, may be a sign of mental distress—not the need for a doctor.

Watch how viruses like Ebola can spill over from animals to humans—and vice-versa.

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

Your pet might eat you if you die

Cats and dogs can eat their deceased owners. Experts say it typically occurs after days without food and reflects basic survival instincts, rather than aggression, affection loss, or a sudden behavioral shift.

Being near a lightning strike—even without getting struck—can be fatal

Because animal tissue is generally more conductive than soil, electricity moving along Earth's surface after a strike tends to travel up and back down an animal's legs, discharging dangerous amounts of energy along the way, with risks increasing the farther apart the legs are. This ground current accounts for about half of all lightning-related deaths and injuries in humans.

Imagining if Disney films about animals were scientifically accurate

Then when Scar took over from Mufasa, he would have likely killed all of the existing cubs in the pride, including Nala. Or when Nemo's mom died, his dad would technically have become a female.

Tigers emerged much earlier as a species than lions

Both lions and tigers are iconic big cats known for their size and power, but they remain distinct species. Beyond just looking different, they can exhibit very different behaviors. For example, tigers are significantly less social than lions, who live in social matriarchal groups. Tigers and lions are unlikely to ever interact in the wild, but humans have artificially bred them in captivity, creating a "liger."

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

See how Budweiser's famous Clydesdales spend their days at Warm Springs Ranch, where roughly 70 to 80 of the beer brand's giant horses can be found at any given time.

American short story writer Flannery O'Connor raised 40 peacocks, which became potent symbols for her fiction's elegant violence

SpongeBob exemplifies Aristotle's philosophy for living well because he understands that happiness doesn't come from external factors like money, recognition, or power.

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

Explore an interactive map built from more than 100,000 survey responses on where people find joy in their lives

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

US consumers collectively owe more than $1T to credit card companies—almost as much as they owe in auto loans.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.