Brrr, it’s getting cold outside! Have you ever wondered how animals like squirrels survive Chicago’s freezing temperatures without so much as a coat? While people typically respond to the cold by staying inside and putting on layers, it turns out squirrels have a similar strategy for dealing with the challenges of winter. They tend to spend more time in the den, and they put on “layers” by fattening up.

The type of squirrel you’re most likely to encounter around Nature Boardwalk at Lincoln Park Zoo is an eastern gray squirrel (Sciurus carolinensis). These are predominantly gray in color—as you would guess from the name—with white bellies.

Gray squirrels do well in urban areas such as Lincoln Park. These critters are homeotherms, which means that unlike some mammals, their body temperatures remain fairly constant throughout the year; they don’t hibernate. In the winter, squirrels spend less time foraging outside their dens, and it’s more common for several squirrels to share a den. This behavior allows more animals to take shelter and also to keep each other warm.

If you’ve been watching the squirrels lately, you may have noticed they’ve been very busy caching food. Caching, also called hoarding, is a behavior characterized by storing stashes of food for later. Squirrels usually do this by putting their food in a shallow hole and covering it up. They don’t remember all these “storage units,” and some of the forgotten seeds they leave behind will germinate and become shrubs, trees, etc. The stashes that are remembered will serve as food when resources are scarce in winter.

Squirrels also prepare for winter by bulking up. Throughout fall, they maximize food consumption and body mass. In winter, when food is hard to come by, these reserves will help the animals survive.

One other tactic gray squirrels use to keep warm in winter is shivering. Shivering isn’t just a sign that you’re cold; it also serves as a way to keep warm. While it certainly doesn’t sound fun, gray squirrels are remarkably good at generating heat by shivering.

The gray squirrels at Nature Boardwalk are busily eating everything in sight and storing food for later. Come down to Nature Boardwalk today to see them in action as they gear up for the approaching cold and snow!

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This piece was originally published on Lincoln Park Zoo’s Nature Boardwalk Blog. Its author, Vicky Hunt, is the coordinator of wildlife management for the Nature Boardwalk.

Homelessness affects all types of people, including families and veterans of war. Credit: Marty Bahamonde/FEMA Photo Library

A few days ago, a family came to the Oklahoma City-based social services agency where I work seeking assistance. The family of five, three of whom were children under the age of six, was relocating to Oklahoma City from Texas. The father had been hired as a janitor at a local oil and gas company. The family pooled together what they thought would be plenty of money to relocate, find a place to live, and feed themselves until the father received his first paycheck.

Unfortunately, their car broke down, and they put all the money they had into repairing it. When it still wasn’t running properly, they were forced to sell the vehicle. Homeless and without transportation, the family was living out of a motel, which they paid for using the company’s relocation package. The night before Thanksgiving, the assistance the family was receiving expired. They were left with nowhere to go and no way to pay for the motel in which they were living, much less make a deposit on a house or apartment. Because they were new to the area, they had no family or friends who could take them in.

This family isn’t what we typically picture when we think about homelessness. Most of us tend to think of a single adult pushing a shopping cart, begging for spare change, and sleeping on the streets. We assume these kinds of people have a drug problem or a mental illness, and that they feel “safer” living on the streets. If they don’t have any addictions or medical conditions causing them to be homeless, we tell ourselves they should just get a job, and all their problems would be solved.

These myths have been perpetuated for decades, but the reality is that many American families are just a few strokes of bad luck away from homelessness. The Urban Institute recently reported that over 600,000 families a year will experience a period of homelessness. Twenty-three percent of all homeless people belong to families with children, according to a study by the US Conference of Mayors. Many homeless families, like the one mentioned above, have at least one parent who works full time and receive little to no government assistance.

While about 40 percent of homeless people abuse alcohol or other drugs, 15 percent of those suffer from a co-occurring mental illness. Many times, individuals with undiagnosed or untreated mental illnesses choose to self-medicate with drugs or alcohol to help them cope with daily life. Although 40 percent is not an insignificant number, it is far below what many of us would expect.

Once an individual or family becomes homeless, there are many barriers preventing them from escaping the situation. Even if they do have a job, like the father in the family above, there are many other issues that arise and make it difficult to avoid homelessness. These include: finding child care, securing reliable transportation, having a good education, gaining job skills, and maintaining proper hygiene. In addition, according to the National Low Income Housing Coalition, the rent for a one- or two-bedroom apartment at fair market value costs more than minimum wage. This means even when a homeless person is able to get a job, he or she may not be able to afford an apartment.

As for the family at the beginning of the story, our agency was able to provide them with assistance through our First Month’s Rent program. They qualified for funds that allowed them to make a deposit on a mobile home and pay their first month’s rent until the father received his first paycheck. Because he has a steady income and their rent is less than 30 percent of his income, they are on track to sustaining their permanent housing.

Many people want to help the homeless, but are unsure what to do or what difference it will make. There is a certain amount of risk involved in giving money to a needy stranger on the street, especially since there is no way to ensure that the donation will be put to good use. Giving money to a social services agency is a great alternative. These nonprofits work with the homeless and those in need on a daily basis. They put their clients on the path to permanent housing so families like the one in this story have a chance at a safe, affordable place to live.

A pilgrim statue and yellow arrow mark the way on the Camino de Santiago. Credit: René Madonna Ostberg

This past fall I went for a very long walk in Spain. How long? Well, I started out on September 22nd, in a small town in the French Pyrenees called Saint-Jean-Pied-de-Port, and got to my destination, the city of Santiago de Compostela in northwestern Spain, on October 27th. It was a walk that took me over four mountain ranges and a distance of about 500 miles (790 km)—nearly the same as if I had stepped out of my house in the suburbs of Chicago and walked south all the way to Memphis, Tennessee.

It’s actually fitting that I use Memphis as my example—home of Elvis Presley’s tomb at Graceland and considered a place of pilgrimage for rock ‘n’ roll fans and pop culture junkies from around the world. My walk was a pilgrimage too, only in the true sense of the word, ending at the Spanish region of Galicia at the tomb of the Apostle St. James. The walk is known as El Camino de Santiago, or the Way of St. James, and it’s been around a great deal longer than any American tourist trail. So long, in fact, it played an important role in the Reconquista of Spain during the Middle Ages.

There are numerous and conflicting stories explaining El Camino de Santiago’s establishment as a Christian pilgrimage route. The story in Spanish tradition is that St. James the Greater traveled all the way to Galicia to preach the Gospel after the death of Christ. He eventually returned to Jerusalem and was subsequently martyred by King Herod in 44 CE. After his death his disciples took his body back to Galicia to be buried at a site close to the Atlantic coast that was believed to be finis terre, or the land’s end of the Western world. St. James’s remains were said to lie forgotten for centuries until they were discovered and authenticated as belonging to the apostle in the 800s. A church was eventually built over his tomb and became a place of local pilgrimage.

Meanwhile, as large parts of Spain were claimed by the Moorish conquest, the Spanish Catholic Church took hold of the legend of St. James and his connection with Galicia to launch a re-conquest of Spain for Christianity. Stories sprung up of James appearing in battle to Christian Crusaders and securing their victory, and a rather problematic image was popularized of the apostle as “St. James the Moor-Slayer.” St. James’s tomb in Galicia, in a city now named after him, Santiago de Compostela, grew as a pilgrimage site, with routes to the tomb cropping up all over Europe. The most popular of these routes was the Camino Francés, a way that travels through the French Pyrenees to the Spanish village of Roncesvalles and then cuts west across northern Spain to Santiago.

Morning on the Camino, in the French Pyrenees. Credit: René Madonna Ostberg

This is the still the most common route of the Camino, and this is the route I took. Today it passes through numerous cities and villages whose fame and very existence began as a stop on the Camino de Santiago. Modern-day pilgrims on the Camino Francés pass through Basque country and right by the site of a battle in the French epic The Song of Roland. They walk through Pamplona (right up the street where the bulls run every July), Burgos and León (both of which have stunning cathedrals laden with images of St. James), and Ponferadda (which boasts a castle built by the Knights Templar). They also cross over mountains and a vast plain known as the meseta, pass by cornfields, sunflower fields, vineyards, and even a free wine fountain, ramble past groves of olive, fig, almond, walnut, and chestnut trees, and trudge through the mud on rainy Galicia’s frequently flooded roads and hills.

Grapes harvested from a vineyard on the Camino. Credit: René Madonna Ostberg

Along the way they sleep in albergues or refugios—very basic hostels open only to pilgrims, some run by churches or religious orders, some by private owners, some brand new, some in buildings centuries old. All albergues, however, have three things in common: they all feature snorers, they all kick pilgrims out at dawn to get them going on the Camino, and they all provide a stamp in a pilgrim’s passport of sorts, called a credencial, that pilgrims guard and furnish to prove how far they’ve walked.

At the end of it all, pilgrims come to a stunning cathedral in the old section of Santiago, where they are granted a certificate known as a compostela, named after the city where it’s granted. Receiving a compostela comes with a plenary indulgence or a pardon for sins by the Catholic Church. Most pilgrims are just happy to have finally reached Santiago and possibly witness the marvelous swinging of the botafumeiro, a giant incense-dispensing urn unique to the Santiago Cathedral that is swung literally to the rafters during mass on holy days.

A priest sets the botafumeiro swinging during mass inside the Santiago Cathedral. Credit: René Madonna Ostberg

These days many pilgrims still attempt the Camino for religious or spiritual reasons, while many do it purely for the exercise or for a personal time-out. Meanwhile, as in the old days, pilgrims still come from far and wide. I met pilgrims who walked all the way to Santiago from Switzerland and Germany (a 90-day journey according to one of them). I met a Catholic priest from the Philippines making his second Camino, and I met a young Israeli man filling up on adventure before his mandatory entry into the Israeli army. I met pilgrims from Canada, Ireland, France, Venezuela, Brazil, Australia, South Korea, Japan, Italy, South Africa, Sweden, Catalonia, Ibiza…but I met few fellow Americans. Maybe they’re too busy going to Graceland.

The author and a friend in front of Burgos Cathedral. Credit: René Madonna Ostberg

Whatever the reason and wherever one comes from, arriving in Santiago after walking the Camino is a glorious feeling. Walking 500 miles may not be as impressive as, say, walking across a continent or walking around the world—but in the end, with all the friends a pilgrim makes, walking the Camino feels a bit like walking with the world.

Painted turtles (Chrysemys picta) in climates like ours hunker down for winter and don’t emerge until the Sun is out and plants are sprouting again in the spring. On particularly cold, blustery winter days, I tend to think that isn’t a bad plan!

Painted turtles bask at Lincoln Park Zoo's Nature Boardwalk, April 2011. Photo courtesty of Vicky Hunt/Lincoln Park Zoo

Unlike humans, which need to keep a fairly consistent body temperature regardless of their surroundings, painted turtles are ectotherms, which means their body temperature depends on their environment. In the winter, as the pond begins to freeze, the painted turtles at Nature Boardwalk at Lincoln Park Zoo find a nice spot in the mud at the bottom, fairly close to shore and under the ice, where they will remain (more or less) for the rest of the winter.

Last year the turtles we were tracking all overwintered in the vicinity of the island. This year it looks like a similar pattern is occurring even though we’re tracking different turtles this time. The turtles are slowing down, but still moving around a bit, as they settle in. This is a map of three of the turtles’ locations on December 14, 2011. Image courtesy of Vicky Hunt/Lincoln Park Zoo

Their body temperature drops to approximately that of the surrounding water. Their metabolism slows to a crawl, and they won’t come up for air until spring. Even though they abstain from breathing, they still have some minimal oxygen requirements, which they meet by taking up oxygen from the surrounding water through their skin.

Urban Wildlife Institute Intern Mason Fidino uses radio telemetry equipment to pinpoint the turtles' locations in the pond. Photo courtesy of Vicky Hunt/Lincoln Park Zoo

It’s therefore important that the dissolved oxygen content in the pond’s water is adequate all winter so the turtles can take in oxygen.

At Nature Boardwalk, aerators run all winter to keep patches of the pond from freezing over completely. This ensures that dissolved oxygen levels are sufficiently high. Taking up dissolved oxygen in water through the skin is obviously not as effective as breathing, but the turtles seem to make it work!

Perhaps the most interesting thing about all this is that even with their metabolisms practically shut down—their body temperatures nearly freezing—the turtles do in fact move around.

Last year we tracked them through the winter using radio telemetry.

While the turtles stuck to the edges around the island in the pond, they did mosey their way around, often making small, but perceptible, movements from week to week.

We wouldn’t know this without radio telemetry. In fact, radio telemetry has helped scientists make many discoveries about the physiology of how turtles overwinter; without this technology we’d know a lot less about these amazing adaptations.

We don’t expect to see the painted turtles at Nature Boardwalk for several months now, but we’ll still be ‘keeping an eye’ on them via their radio transmitters!

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This piece was originally published on Lincoln Park Zoo’s Nature Boardwalk Blog. Its author, Vicky Hunt, is the coordinator of wildlife management for the Nature Boardwalk.

Originally published on Christmas Eve 2010, we decided that this post and its images, like the day itself, are timeless, and so we wished to share them with our readers once again.

From Santa Claus to Sinterklaas and from nativity scenes and solemn prayer, tomorrow most Christians around the world celebrate Christmas Day, a festival celebrating the birth of Jesus. On the occasion, we’ve dipped into Britannica’s archive to bring you a selection of images of the celebration since the 19th century around the world. (The last one, of course, is an homage to Britannica.)

To all those celebrating, Merry Christmas and have a safe, happy, and healthy holiday.

The first Christmas card, designed by J.C. Horsley for his friend Sir Henry Cole, 1843. Credit: Courtesy of Hallmark Cards, Inc.

Prince Albert, Queen Victoria, and the British royal family gathered around the Christmas tree at Windsor Castle, from the Illustrated London News, 1848. Credit: J.R. Freeman & Co. Ltd.

Illustration from an undated edition of Charles Dickens’s A Christmas Carol. Credit: © Photos.com/Thinkstock

Pres. John F. Kennedy and his wife, Jacqueline, in the Blue Room of the White House at Christmastime, 1961. Credit: Robert Knudsen—Official White House Photo/John F. Kennedy Presidential Library

The Union Christmas Dinner, print published in Harper’s Weekly in 1864 depicting President Abraham Lincoln’s invitation to the South to rejoin the Union on an equal basis with the other states. Credit: Library of Congress, Washington, D.C.

Children dressed as trolls during the annual Christmas procession in the Vestmanna Islands, Iceland. Credit: Floris Leeuwenberg—The Cover Story/Corbis

Manger Square and the Church of the Nativity during the traditional Christmas procession in Bethlehem, West Bank. Credit: Nasser Shiyoukhi/AP

A Christmas tree and Hanukkah menorah sharing space in Washington, D.C., 2004. Credit: © Tim Sloan—AFP/Getty Images

Festive lights decorate the outdoor markets at Romer Square in Frankfurt am Main, Germany. Credit: Brian Lawrence/SuperStock

Santa Claus, dressed in a traditional Finnish costume, totes a bag of toys in Rovaniemi, Finland. Credit: Bob Strong—Reuters/Landov

Christmas decorations adorn a house in Alsace, France. Credit: age fotostock/SuperStock

A Nativity scene by a Haitian artist reflects the island's tropical Christmas celebration. Credit: Toussaint Auguste/UNICEF

Christmas decorations lighting up Donegall Square, Belfast, N.Ire. Credit: Geray Sweeney/Tourism Ireland

Christmas-time magazine advertisement for “The Encyclopaedia Britannica”; mentions famous contributors and features bookcases for the EB set, “Britannica Junior,” and yearbooks. Date unknown, but probably 1940s. Credit: Encyclopædia Britannica, Inc.

Christmas, the festival commemorating the birth of Jesus Christ, is celebrated by a majority of Christians on December 25 on the Gregorian calendar. But early Christians did not celebrate his birth, and no one knows on which date Jesus was actually born (some scholars believe that the actual date was in the early spring, which would place the occurrence of the holiday closer to Easter, the holiday commemorating his resurrection).

The Nativity, fresco by Giotto, c. 1305–06, depicting the birth of Jesus; in the Scrovegni Chapel, Padua, Italy. Credit: SuperStock.

The origins of the holiday and its December date lie in the ancient Greco-Roman world, as commemorations probably began sometime in the 2nd century. There are at least three possible origins for the December date. The Roman Christian historian Sextus Julius Africanus dated Jesus’ conception to March 25 (the same date upon which he held that the world was created), which, after nine months in his mother’s womb, would result in a December 25 birth.

In the 3rd century, the Roman Empire, which at the time had not adopted Christianity, celebrated the rebirth of the Unconquered Sun (Sol Invictus) on December 25th—this holiday not only marked the return of longer days after the winter solstice but also followed the popular Roman festival called the Saturnalia (during which people feasted and exchanged gifts). It was also the birthday of the Indo-European deity Mithra, a god of light and loyalty whose cult was at the time growing popular among Roman soldiers.

The Holy Family, oil on panel transferred to hardboard, by Giorgione, c. 1500; in the National Gallery of Art, Washington, D.C. 37.3 × 45.6 cm. Credit: Courtesy of the National Gallery of Art, Washington, D.C., Samuel H. Kress Collection

As the church in Rome only formally celebrated December 25th in 336 during the reign of the emperor Constantine, who made Christianity the effective religion of the empire, some have speculated that choosing this date had the political motive of weakening the established pagan celebrations. The date was not widely accepted in the Eastern empire, where January 6 had been favored, for another half-century, and Christmas did not become a major Christian festival until the 9th century.

Matthew Stefon is the religion editor at Encyclopaedia Britannica.

(Geological Society of America) Where on Earth is it like Mars? How were the Apollo astronauts trained to be geologists on the Moon? Are volcanoes on Earth just like the ones on other planets? The exploration of our solar system begins in our own backyard. Discoveries on other planetary bodies cannot always be easily explained. Therefore, geologic sites on this planet are used to better understand the extraterrestrial worlds we explore with humans, robots, and satellites.

(Johns Hopkins University) Time can stand still, or at least look the same from year to year, two calendar reform advocates say.

(Helmholtz Association of German Research Centres) Every year for Christmas, the North American Air Defence Command NORAD posts an animation on their website, in which the exact flight path of Santa Claus’ sled led by reindeer Rudolf is precisely located http://www.noradsanta.org/en/.

(Technische Universitaet Muenchen) A group with researchers of the Technical University of Munich are the first to plot changes in the Earth’s axis through laboratory measurements. To do this, they constructed the world’s most stable ring laser. Previously, scientists were only able to track shifts in the axis indirectly by monitoring fixed objects in space. Capturing these shifts is crucial for navigation systems. The work has been recognized an Exceptional Research Spotlight by the American Physical Society.