Theresa Vargas photographed this fox in her backyard on Nov. 15. (Theresa Vargas/The Washington Post)

One of the last times it snowed hard enough for the roads to be risky and schools across the Washington region to close, I watched a fox playing in my backyard.

He frolicked for about five minutes, his body a red streak against a white backdrop as he ran and jumped.

He made the snow seem almost inviting.

Through a window, I snapped a photo and posted it on a private social media page. I captioned it: “This is our backyard fox. And he might be the only one at our house that is loving the snow today.”

I had come to think of the fox as our fox because he came so often, usually leaving three very noticeable holes in our garden. My family was surprised the first time we spotted him and his siblings walking through our yard. But soon, we came to expect his visits, which is why we noticed when they suddenly stopped.

That snowy day, it turns out, was the last time we would see him. It would also mark the beginning of a mystery we still haven’t solved.

The fox played for five minutes, standing still for just a moment before taking off again. (Theresa Vargas/The Washington Post)

A few weeks after I posted that photo, we found a fox head in our yard.

The head was hidden in a part of our garden that made us feel confident no human had left us this gruesome gift. But then the obvious question was: What did?

A person can live for years, even decades, in the D.C. area and not notice the creatures that also make their homes here, hidden in the greenery that exists between major roads and commercial strips.

When wildlife does show itself, it is a rare enough occurrence that it makes the news. The Washington Post ran a story a few years ago about two vultures that showed up on K Street. I know this because I was assigned to write about it at the time. Another story involved two snowy owls that moved into the courtyards of the U.S. Department of Agriculture. They were nicknamed Thelma and Louise. Recently, a opossum caused a stir after it was spotted outside the newspaper’s office building in broad daylight. Washingtonians expect to see rodents. They don’t expect to encounter other long-tailed creatures.

I have lived in Northern Virginia for more than a dozen years, and it was only in the past few months — after I was pulled in by that fox head and the need to know what left it there — that I began to really learn about what lurks around us every day, unseen.

After we found the head, I started researching online and found an article about a family in Arlington who had discovered three decapitated fox heads in their yard in 2013. The discovery raised concerns among residents about the possibility of a coyote. It also stumped officials.

From the ARLnow article:

“AWLA Chief of Animal Control Alice Burton said that most of the time when people report coyote sightings to her, they turn out to be foxes, but this was a case that had her puzzled.

“ ‘It’s funny because I’ve reached out to professional naturalists on this and no one has a clue,’ said Burton.

“ ‘Usually when we find decapitated animals, it’s kind of unusual. Heads are actually the first thing that animals eat,’ said Alonso Abugattas, The Department of Parks and Recreations’s natural resources manager and one of the people Burton consulted with.”

I called Jennifer Toussaint, the chief of animal control at the Animal Welfare League of Arlington. She kindly asked if I wanted someone to pick up the head — yes, definitely yes — and then we discussed coyotes.

They are one of the most “respectful” animals, able to exist in neighborhoods without residents having any idea, she explained. She also confirmed that they have made homes in Arlington. While they are elusive, several have been picked up after they were hit by cars.

They also have been captured on video. Abugattas, who is known as the Capital Naturalist on social media, posted a YouTube video of a coyote sniffing in a fox den in an Arlington park. The coyote did that on three different nights, he said.

When I told Abugattas about my fox, he said the most plausible culprit was a coyote.

“Coyotes would see a fox as not only a potential prey but also as competition,” he said. “They’re hunting a lot of the same things.”

But he left room for other possibilities.

He said coyotes normally eat the whole body.

Abugattas said this area is rich with animal life many people have no idea exists. A bobcat was captured on video. Southern flying squirrels are abundant, he said. And a Mediterranean gecko was recently found in the laundry room of a local residence.

“They want to be in our area but not seen in our area,” Toussaint said. “Animals are very smart.”

Foxes have been known to use walkways, and one Toussaint nicknamed “Ma” likes to sunbathe in a grassy area by a parking lot, which has led some people to call the authorities.

Toussaint said many of the calls her office receives stem from a “lack of understanding that leads to unnecessary fear.” She got one call about an aggressive squirrel. It wouldn’t allow a woman to step out of her house. It turns out, a few days earlier, the family had patched a hole in front of the house, and trapped inside of it were the squirrel’s babies.

“They’re fantastic parents,” Toussaint said of squirrels, which have been known to adopt orphaned squirrels, relocating them from one tree to another. That all of this co-exists in the area speaks to “good city planning,” Toussaint said. If animals couldn’t successfully raise their young here, they would leave. If they are successful, “they do it again and again.”

So, what then killed our fox?

The possibilities alone speak to the range of wildlife in the area. I learned from Toussaint and Abugattas that there was no way to know whether the fox was hunted, became ill and died — or even if it was the same fox I had photographed (though I suspect it was).

That leaves us only with theories: Two foxes could have been fighting over a den. A territorial or hungry coyote could have hunted it. The fox could have fallen ill and a scavenger, or several, could have seen an opportunity.

We weren’t looking for it, but this past weekend my family discovered one more possible explanation. We went to an owl feeding at the Potomac Overlook Regional Park in Arlington and as we listened to the presentation before seeing the birds feed on tiny white mice, one detail stood out.

The great horned owl, which we have seen twice in our backyard, apparently has been known to make meals of other owls — and foxes.