Red foxes exist throughout much of the United States, with the exception of the southwest. In Chicago, they are not common in high numbers, but are still 【小题1】in certain areas of the city. Coyotes(丛林狼) usually compete with red foxes, and the large coyote population and 【小题2】living space in Chicago maybe related to the small number of red foxes.

Red foxes are 【小题3】smaller than coyotes, weighing 7-15 pounds on average and standing up to 20 inches. Easily recognizable by their striking redcoats, red foxes also have black 【小题4】on their feet, black-tipped ears, as well as along tail.

Generally living alone, red foxes do not form 【小题5】like other dog-like animals. Adults【小题6】during the breeding(繁殖) season to raise their young in hidden places, such as fallen trees, or other natural or artificial structures. As omnivores(杂食动物), red foxes eat a variety of foods including rabbits, birds, insects and fruits. Red foxes may store food in buried locations where they pile up 【小题7】to eat later. Sometimes they are killed by coyotes and humans. They are also easily affected by harmful skin diseases that can lead to death if not 【小题8】.

When digging homes under buildings, red foxes may come into conflict with people. Sometimes foxes may hunt outdoor cats or chickens. Keep cats indoors and get these areas 【小题9】to prevent foxes entering. As with any wild animal, it is important to never feed red foxes, as this may cause them to lose their natural 【小题10】of humans and exhibit unusual behaviors.

If you see a house cat, the【小题1】are high that it will have white paws, a look that many owners affectionately call“socks.” But socks are rarely seen in wildcats, the elusive and undomesticated cousin of the house cat, so why do so many pet cats sport furry white feet?

As it turns out, this story started about 10,000 years ago, when humans and cats 【小题2】   life was better together.

This【小题3】eventually led to uber-prevalent socks on cats, as well as other well-known coat patterns, said Leslie Lyons, professor emerita and head of the Feline Genetics Laboratory at the University of Missouri College of Veterinary Medicine.

“As humans became farmers and started staying in one place, they had grain stores and waste piles” that attracted rodents, Lyons said. It was a mutually beneficial arrangement: the humans had fewer rodents to deal with and the cats got an easy meal.

The wild, undomesticated ancestor species of house cats, Felis silvestris, lives in Africa and Eurasia. These felines are tasty snacks as kittens and stealthy predators as adults, so 【小题4】 born with a coat that offers camouflage (保护色) have tended to survive and reproduce.

But not every F. silvestiis is born with a coat that blends into its habitat.

“Genetic mutations are occurring all the time.” Lyons said.

There isn’t much evidence to indicate why early cat people chose the individuals they did, but Lyons said the range of coats seen on modern domestic cats shows that our agrarian ancestors favored cats with markings that would have 【小题5】with their camouflage.

In its native mixed forest or scrub desert environment, a cat with stark white paws would have stood out to predators and prey.

When humans started taking an interest in cats, these white paws would have stood out to them, too. “There were probably people saying, ‘I particularly like that kitten because it has white feet . Let’s make sure it survives’”, Lyons said.

Humans probably also【小题6】cats who were calm and comfortable around humans, Lyons said. Behavioral traits seem unrelated to coat color, but for reasons that scientists don’t fully understand, white spots tend to appear when the 【小题7】individuals are selected and bred.

These【小题8】fur colors and markings emerge while a cat embryo is developing. The cells that give cat fur its color first appear as neural crest cells, which are located along what will become the back, Lyons said.

Then, those cells slowly migrate down and around the body. If those waves of cells move far enough to meet each other on the cat’s front side, the embryo will be born a solid-colored kitten, such as an all-black or all-orange cat. Felines 【小题9】white feet, faces, chests and bellies when these cells don’t quite make it all the way.

So, the next time you see a kitty wearing white socks, you’ll know that this 【小题10】 feature is a result of genetic mutations, domestication and developmental biology. Although if you try telling the cat that, it will probably just look at you quizzically before sauntering away.

Using dragonflies as contamination(污染) detectors

Mercury(汞)pollution from power plants and mining operations can end up in our air and water.

But it’s 【小题1】 to predict just how much of that environmental mercury will make its way into our food—and our bodies.

“We were working on developing a bioindicator, a biosentinel, that could inform us of the levels of mercury contamination across the US.”

Ecologist Collin Eagles-Smith of the United States Geological Survey and his colleagues came up with a practical way to 【小题2】 the scope of mercury contamination in an ecosystem by measuring mercury levels in a single species. Their bioindicator: juvenile dragonflies, or larvae(幼虫). Dragonfly larvae stay underwater, don’t move much, are easy to collect and live long enough to accumulate 【小题3】 amounts of mercury.

“If you have enough locations 【小题4】 with dragonflies, you can develop an index of the relative amount of mercury in the biological community. ”

The team measured mercury 【小题5】 in thousands of dragonfly larvae collected from waterways in 100 national parks during a 10-year period. And to amass the large sample number, they recruited volunteers through the Dragonfly Mercury Project.

The volunteers used dip nets to collect dragonfly larvae from their aquatic abodes(住所). National park staff then sent the larvae to laboratories for processing. For 【小题6】 the researchers also measured mercury concentrations(浓度)in other aquatic organisms.

“Using the relationships between dragonfly concentrations and fish concentrations, we were able to develop what we call an impairment 【小题7】 . ”

That index allowed the researchers to make health risk【小题8】 at each sample site.

“About 12% of the locations posed what we consider to be high or severe risk of health impairments to fish, wildlife or humans if they【小题9】 organisms from those locations. You can begin to build models that are predictive of how much mercury might be in a system and then apply that model to locations where you haven’t sampled dragonflies.”

“And that can inform future management actions to 【小题10】 the factors that are promoting the mercury production or simply inform agencies that may want to evaluate whether or not fish consumption advisories(警告)are necessary. ”

The study is in the journal of Environmental Science & Technology.