Several species of hares—including the Arctic hare (Lepus arcticus), the mountain hare (L. timidus), and the snowshoe hare (L. americanus)—turn from brown or grayish to white in the winter. The color change is thought to be at least partially linked to photoperiod—that is, the amount of light received during the day. As the days shorten, receptors in the retina transmit that information to the hare’s brain, stimulating the replacement of brown hair to white, starting with the extremities. One study has shown that global warming may be a major threat to the survival of these animals. By reducing snow cover, the climatic phenomenon throws a wrench in the timing of the color change, leaving milk-colored animals to conceal themselves against earth-colored surroundings.

Three species of weasels swap their warm summer browns for icy whites: the least weasel (Mustela nivalis), the long-tailed weasel (M. frenata), and the short-tailed weasel, or stoat (M. erminea). The latter species is perhaps best known as the ermine, also the name of its winter fur, which is white except for the black tip of the tail. The uniquely patterned fur was once used to trim the robes of royalty and clergy. Weasels of the same species that live in more southerly climates usually don’t change color, though their more northerly relatives do. In transition zones, some weasels only partially change color, resulting in patchy white-and-brown fur. Interestingly, color-changing weasels have been shown to change color regardless of temperature or location, suggesting that they too rely on photoperiod to cue their molts.

A subspecies of caribou native to the High Arctic of Canada and Greenland, Peary caribou (Rangifer tarandus pearyi) exchange their silvery summer coats for white ones with the coming of winter. They are the only subspecies of caribou to undergo such a change. Other subspecies remain brown or gray year-round, though the shades may lighten slightly with the growth of their winter coats. Peary caribou are the smallest subspecies of caribou and, because of their morphological differences, were once considered a separate species.

Lemmings in the genus Dicrostonyx, which comprises an indeterminate number of species, turn from brown or gray in the warmer months to white when the snows come. (They belong to a different genus than true lemmings, which remain brown.) Strangely, they spend most of their time burrowing beneath the snow, which would seem to render camouflage unnecessary. They even grow special winter claws—really extensions of the toe pads—for digging through the drifts to create nests and reach the stems of the Arctic willows upon which they feed. Their skins were once used by Eskimo peoples as clothing embellishments.

All three species of ptarmigans—a genus of birds related to grouse, chickens, and pheasants—trade their scalloped brown plumage for white feathers. (They spend spring and fall in a mottled state, matching the patchy snow cover.) The white-tailed ptarmigan (Lagopus leucura) turns entirely white, while the willow ptarmigan (L. lagopus) and rock ptarmigan (L. muta) retain some black feathers in their tails. Ptarmigans even develop white boots to match; the downy foot covering also helps them to walk atop the snow. The air bubbles in their winter feathers—which may help with insulation—scatter light, making them appear more brightly white than other white birds.

This is probably the only animal on this list that you can actually keep as a pet. The Siberian hamster, or Dzhungarian hamster (Phodopus sungorus), often sold as the “winter white,” will change from a silvery chinchilla shade to mostly white if it is kept in a room that receives natural light. Temperature does not seem to affect the molt.

Arctic foxes (Vulpes lagopus) are typically brownish gray in the summer and frosty white in the winter. Weirdly, coastal populations in Alaska and Canada are slate gray and lighten only slightly during the winter. Some of these were introduced to the Aleutian Islands by fur trappers, who could charge more money for their unusually colored coats. Among the main predators of the Arctic fox is its cousin the red fox (V. vulpes). Though the overlap in range was historically rather thin, climate change has allowed the red fox to move farther into the Arctic fox’s icy domain, outcompeting it for food and sometimes eating it.

If you’re caring for a loved one with special needs, you may be thinking about how to enhance their care without compromising their eligibility for government benefits. Or perhaps you’re considering ways to provide for them after your death. Estate planning can be challenging in the best circumstances, but there’s additional complexity in setting up accounts and trusts for a family member with special needs.

The good news is you have choices, depending on the circumstances of your estate and the family member who needs lifetime care. Along with the Achieving a Better Life Experience (ABLE) account, various other trusts are available, including two types of special needs trusts that may be right for your family.

The Green Bay Packers and the Chicago Bears have played each other about 200 times since 1921, the year after the National Football League was founded. No NFL team has won more championships (13 for the Packers and 9 for the Monsters of the Midway), and none has placed more players in the Hall of Fame than the Packers and the Bears, not to mention the marquee value of their enshrined coaches—from founding Packer Curly Lambeau and George (“Papa Bear”) Halas to Vince Lombardi and Mike Ditka. As for the players, how about a few nicknames, such as the “Galloping Ghost,” “Golden Boy,” and “Sweetness”? But even more than longevity and legends, this is a rivalry about geography: namely, the relative proximity of the Midwest’s main megalopolis to the NFL’s smallest hometown, between which those from the Windy City—on their way to vacations on Wisconsin lakes—drive too fast, according to their Dairy State  neighbors, whom Chicagoans disparagingly label “cheeseheads” only to watch them embrace that nickname and wear it on their noggins at Lambeau Field.

The Los Angeles Lakers and the Boston Celtics have met 12 times in the NBA finals. They tower above the competition in terms of Hall of Fame inductees (some two dozen each) and championships (17 for Boston and 16 for Los Angeles). Try to name better personal rivalries than Magic Johnson versus Larry Bird or Bill Russell versus Wilt Chamberlain. How about better symbolic drama and entertainment value? Exhibit A: Red Auerbach  lighting his victory cigar on the parquet floor of the Boston Garden in the 1950s and ’60s. Exhibit B: slick-haired Pat Riley orchestrating the Lakers’ “Showtime” in Armani in the 1980s. The rivalry is also very complex, and race is part of the story. In the 1980s, when Johnson and Bird were dueling, the Celtics fielded a disproportionately white lineup at a time when the game had become dominated by African American players. Fans—both Black and white—noticed, though not as part of a meaningful national dialogue. Yet, two decades earlier, the Celtics had a starting line-up that featured at least four Black players in era when that was far from the norm. But then Boston, a hotbed of abolitionism in the 19th century, also was the scene of ugly antibusing demonstrations in the 20th century. Like I said, complex.