The Humane Society of the United States estimates there are tens of millions of feral house cats living across the country.

Feral cats originate from pet cats that were lost or abandoned and learned to survive outdoors without human help. Most are difficult to tame or adopt.

Outdoor cats often live in colonies, populated by former pets and their offspring. They are resourceful, but some may still need help to survive a cold winter.

If you want to help feral cats in your community, here are a few things to consider:

Shelter

A cat takes shelter from the snow. A cat takes shelter from the snow. (Photo: kisluvkis [CC BY 2.0]/Flickr)

Cats have thick coats, but they may still need warm, dry places to protect them from harsh weather. Building your own shelter is relatively simple, and there are a variety of plans for inexpensive cat shelters available online:

When constructing a shelter, size is important. It should be large enough to house several felines, but small enough to trap cats’ body heat to warm the inside. If the shelter is too large, it will be difficult for cats to keep the space warm.

Straw is the best material to line the shelter because it lets cats burrow. Pillowcases loosely stuffed with packing peanuts and shredded newspaper are also suitable; however, the pillowcases will need to be washed and re-stuffed periodically.

If you won’t be able to check on the shelter regularly, don't use these types of insulation. Instead, line the shelter’s floor and inner walls with Mylar to reflect their body heat.

Avoid insulating shelters with blankets, towels, hay or folded newspapers.

Food and water

feral cat in snow Many people feel compelled to feed feral cats, especially during winter. (Photo: Alexey Khromushin/Shutterstock)

There are potential downsides to feeding feral cats, but it may also be a life-saving service in winter, and it can be done responsibly. If you decide to do it, place food and water near the shelter where it's easily accessible and safe from the elements.

The Humane Society suggests placing two shelters with their doorways facing each other and securing a board between them to create a canopy.

If your area is prone to freezing temperatures, place water or canned food in a thick plastic container that’s deep and wide, or purchase a solar-heated dish.

You can place food inside the cat shelter, but don’t put water bowls inside.

The Neighborhood Cats website has several other suggestions for keeping a cat's water bowl from freezing.

Trap-neuter-return

feral cats waiting to be sterilized for TNR program Feral cats await spaying or neutering as part of a TNR program in Washington, D.C. (Photo: Mandel Ngan/AFP/Getty Images)

The Humane Society endorses a practice known as "trap-neuter-return" (TNR) for managing feral cat colonies. TNR involves trapping feral cats, spaying and neutering them, vaccinating them, "ear-tipping" them for identification, then returning them to their territory. Kittens and sociable adults may be taken in for adoption.

TNR is supported by many animal-welfare groups, but it can be controversial. Feral cats are non-native predators that prey on native wildlife, sometimes at unsustainable rates, and research shows they also play a key role in spreading the parasite Toxoplasma gondii to wildlife, including endangered sea otters. While the goal of TNR is to humanely shrink feral cat colonies over time, many conservationists and wildlife charities dispute its effectiveness.

Research suggests TNR can be effective, but sterilization efforts must reach 75% of the colony for its population to fall over time. That level of sterilization can also reduce preventable cat deaths more than 30-fold, researchers found.

Aside from the ecological issues with TNR, some people have concerns about trapping cats during winter, since surgery requires females to have their stomachs shaved. According to the Humane Society, however, winter trapping can have advantages. There are fewer pregnant cats during winter months, for example, which makes surgery less complicated. Trapping cats in winter may also offer an opportunity to prevent the birth of more kittens come spring.

Before trapping feral cats in cold months, though, it may be wise to first provide a shelter for the colony, so they have a comfortable place to recover post-surgery.

How to care for feral cats during the winter
There are several ways to help feral cats survive cold weather.