Q: How can suburban neighborhoods control deer populations?

—Bev Brooks | Sanford, North Carolina

It’s a serious issue, says William McShea, a biologist at the Smithsonian Conservation Biology Institut e . There are ways to keep deer out of gardens—fences, dogs and wind chimes are some of the most effective methods. But deer can spread tick-borne diseases and cause fatal car accidents, and as the proverb goes, headlights don’t always scare them away. That’s why many towns allow limited hunting or even hire professional hunters to cull local deer populations. Scientists have developed contraceptive darts for areas densely populated with humans, or places where the residents want a more humane approach. But in areas surrounded by forests and growth, it’s difficult to dart enough animals to keep the population down significantly. Driving slowly remains the best way to avoid accidents.

Q: Why are barns red?

—James DeWitt | Lakewood, Colorado

Because of stardust, says David DeVorkin, a historian at the National Air and Space Museum . Red paint was once cheaper than other colors because its color came from iron, an element that’s plentiful in Earth’s crust and was forged in the hearts of stars. When iron is exposed to oxygen it forms iron oxide. The redness of bricks comes from iron oxide—and so does the redness of the rust farmers once mixed with linseed oil to protect their barns’ wood. One way or another, red barns have always owed their color to this cosmic compound.

Q: Was Lincoln in poor health when he died?

—Maria Pantagis | Englewood, New Jersey

Scholars have speculated that Lincoln had Marfan syndrome or multiple endocrine neoplasia type 2B, disorders marked by tall frames and lanky limbs. But Harry Rubenstein, curator emeritus at the National Museum of American History , says neither condition can be diagnosed from those traits alone. What’s more, Lincoln lived to be 56, which was well beyond the average life expectancy for either of those two conditions. It’s hard to know whether the president’s health would’ve failed if he hadn’t been assassinated. We do know that he suffered from melancholic depression and likely got mercury poisoning from the pills he took to treat it. For those who want to keep analyzing Lincoln’s physical features, the Smithsonian has casts of his hands and face .

Q: Is climate change giving any mammals an advantage?

—Patricia Spohn | Willow Creek, California

If any land mammals are well positioned to endure a changing climate, it’s small rodents like moles that live in more stable environments underground, says Melissa Hawkins, mammal curator at the National Museum of Natural History . In contrast, large Arctic animals like polar bears and walruses are especially vulnerable: They need more fuel for their large bodies, and their habitats are changing the most dramatically. In the water, some bigger mammals like orcas are beginning to move into areas that were once frozen. This may be an advantage in the short term, but over time they’ll endanger creatures like narwhals and alter the balance of life in other, unpredictable ways. Even changes in the tiniest creatures like ice algae have troubling implications for animals all the way up the food chain.

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