One-eyed Jack was a small dog, more suited to sitting on laps than navigating the streets of Beijing. The squat male mixed-breed dog's single eye shone bright as he approached strangers hoping to be adopted. This stray had obviously once been owned by somebody.

But that was a long time ago. His fur coat had grown filthy. His ratty collar that once clung loosely to his neck was long gone.

"He was a great little dog," recalls Trevor Metz, the Canadian owner of expat watering hole Plan B, in Shuangjing district, in the east of the city. "Every morning, he would be here [in front of the bar]. I felt really bad for him. He was a stray during winter, so I let him stay inside, where it was warm. But I was thinking, 'Oh god, I can't take in another dog.'"

Metz never intended to become an animal rescuer but he found it impossible to ignore the city's needy dogs. By tapping into his network across the capital, he has managed to rehome nearly a dozen strays over the past five years.

This is how One-eyed Jack came to be adopted by a regular at Plan B, a British expat who worked in the administration department at one of Beijing's premier international schools. This was someone, Metz says, he could trust.

Two weeks later, One-eyed Jack was dead.

In the early hours of May 24, the new owner had taken One-eyed Jack out for a walk when he encountered a group of chengguan, or urban management officers, who demanded proof of registration for the dog. Fluent in Putonghua, the owner argued that One-eyed Jack had been vaccinated, but that he hadn't gotten around to registering him yet.

This wasn't good enough for the chengguan.

"The four of them produced these metal poles and just beat the dog to death," says Metz. "One held my friend while the others beat the dog and threw it into a bag and hauled it off. The way [my friend] describes it is horrendous. The men just walked up and swung as hard as they could right on top of the head. The dog let out a whimper and just went down."

Metz is uneasy talking about the incident. His friend was "completely traumatised" and refuses to speak to the media about it, he says. A blog post by the dog owner describes the beating in brutal detail: "It makes me cry, it makes me feel sick. It's disturbing my sleep and the feeling doesn't go away easily."

The police told Metz there was nothing they could do. If the dog had been registered, there may have been compensation, but because it was an unregistered "stray", there was nothing they could charge the chengguan with. Beating a stray dog to death in the street is not illegal in the mainland.

"I feel horribly responsible," admits Metz. "I found him a home, I doomed him. Doing the thing that I thought would save him ended up killing him."

The odds seem to be stacked against Beijing's ad-hoc animal rescuers.

"We don't have an industry where you have animal shelters that are legally licensed NGOs with non-profit status," says Mary Peng, co-founder of the International Centre for Veterinary Services, a clinic in Beijing. Without this, adds Peng, "you can't publicly [raise funds]. This licensing and registration process doesn't even extend to animal shelters. That category isn't covered by the [municipal] commerce bureau."

The result is a patchy network of volunteers who try to save street dogs and cats with few resources and no official lines of support.

IT'S A BLISTERINGLY HOT day in June. Jerri Lan Zihui has come with six of her dogs to Beijing Pet Adoption Day, an event held every few months around the city. On this occasion, the organisers are setting up in front of the 3.3 shopping mall in Sanlitun. The heat is almost unbearable for the animals. Participants pile buckets of ice into cat cages and rub cold bottles of water over the dogs.

The animals, all former strays, quickly become the centre of attention. A young, well-heeled crowd strains to catch a glimpse of those up for adoption. One twenty-something, surnamed Zhang, coos over a plump white cat with crooked black streaks over its eyes. She has never owned a cat before.

"I didn't know whether the cats would be dirty or something," she says, "but actually they are quite clean."

Zhang fills out the form to adopt the cat. Later in the day, the animal rescuer will visit her apartment to determine whether Zhang is a suit-able match.

Meanwhile, one of Lan's dogs, Niu Niu - a beagle and dachshund mix - is attracting plenty of attention. She perks up whenever a person passes by, her tongue slipping away from her rather flat snout. The effect is disarmingly sweet. A young teen applies to take Niu Niu, but Lan doesn't seem too excited - she doesn't think the girl would make a good match. "We'll just have to see," she says, vaguely.

Lan found the dog begging for scraps from customers at a restaurant. Once the nursing mother secured a mouthful, she would promptly sneak off to feed her puppies. But during Lunar New Year, when customers became few and far between, Niu Niu began to starve.

That was two years ago and still Lan hasn't found a home for Niu Niu. The squat brown mutt is temporarily housed along with three other rescues at a "pet club" - a business that offers kennelling and grooming services. While not a licensed shelter, it sometimes houses stray dogs.

Lan visits several times a week to walk the dogs but worries she won't be able to find stable homes for them.

Frustration is evident in her every expression. Sighs often break out when she talks of how difficult it has been lately. She found adoptive homes for 10 dogs and one cat in 2011. But last year, she only managed to rehome two dogs - and one of those ran away from its new family and hasn't been seen since. Lan still goes out searching for that dog, months later, hoping she can find it before the chengguan do.

"I really can't help more dogs," says Lan, with a twinge in her voice. "I can't help but think about the unlucky ones. It is heartbreaking. I want to take them home, but I already know what I have to face. It is like a dead end."

Ding Shiying, aka Grandma Ding, is perhaps the most famous animal rescuer in Beijing. She started sheltering stray cats in her home in Shichahai district in 1983. Back then, she says, strays were a rarity and for years there were only seven or eight cats living with her in her courtyard home. But, at one point, the 86-year-old was caring for more than 300 cats.

Ding says the number of stray cats in Beijing's hutong districts exploded at some point in the past decade, but she's fuzzy on when exactly. Peng believes the rise in the stray-cat population happened sometime in the early 2000s - and theorises that it may have been directly related to the Sars epidemic of 2002-2003.

Peng was one of the first advocates for the grass-roots trap-neuter-return (TNR) policy, a controversial control programme under which feral cats are sterilised and vaccinated before being released into an informal colony overseen by a caretaker. Homes are found for some of the cats while those deemed unadoptable have the tips of their ears permanently marked, to signal to other rescuers both their status and that they have been spayed and vaccinated, so resources aren't wasted.

Peng says she only had four or five cats in her colony before the Sars panic gripped the country. In a matter of months, the number of cats in her TNR project had ballooned - and, she says, other TNR caretakers experienced the same jump in numbers.

Once the source of the disease was traced back to the consumption of civet cat, she says, people feared their pets could harbour the deadly illness. But what they didn't know was that despite their name, civets are more closely related to the mongoose than they are the cat. And the panic didn't stop at cats - dogs, too, were thrown out onto the streets.

Strays and ferals were multiplying faster than anyone could keep up with. Ding had more than 250 cats and several dogs in her three-room courtyard home. There was no way she could take care of such huge numbers on her retirement income, so she went to the papers to seek potential adopters and to publicise her case.

However, donations weren't the only thing that showed up on her doorstep. People started dumping pets at her gate and Ding found it impossible to turn any of them away. Instead of finding a safe harbour, most of these abandoned cats would go on to suffer a terrible fate.

An electrical fire engulfed Ding's home in 2012. Barking dogs jolted the elderly woman out of her sleep in the early winter hours. She rushed outside to get help, but it was too late. By the time the fire was put out, more 150 cats and dogs had perished in the flames.

Two years later, having received generous donations, she is caring for the surviving animals in her newly rebuilt home.

Ding looks all of her 86 years. Beside her sits a scraggly cat that is, allegedly, 25 years old. Toothless, the knotted ginger cat, dappled with bare patches of skin, is never far from Ding.

"Why don't you die already?" she says, seemingly half-joking. But it almost seems self-directed. She admits she's tired of it all, but "has to keep going" for the sake of the animals.

Ding can no longer take the dogs for walks, nor can she easily care for the 40 or so remaining cats. They are remarkably clean, and bottles upon bottles of veterinary medicines line her desk, opposite the bed. A domestic helper comes by to help clean and care for the animals.

SOLO ANIMAL RESCUERS are dedicated but often they are unable to effectively rehome their charges. The typical animal rescuer was traditionally "a retired person who collected strays, but had no connections, no adoption routes", says Chris Barden, a long-time American expat and former writer and translator who now runs the Little Adoption Shop, in Shunyi district.

While it currently functions as a dog shelter, the initial idea was to help these one- or two-person rescue groups find homes for their strays.

"We wanted to help shelters, not become one," Barden says, but the need was so great that he has become a one-man rescue operation.

The Little Adoption Shop - a sort of pet store housing dogs that are ready for immediate adoption - officially started in 2011, when Barden joined other animal lovers in blocking a truck carrying cage upon cage of dogs being shipped north, to hotpot restaurants. A motorist who had spotted the dog-meat truck on the Jingha Expressway blocked it with his car and put a call out over social network Weibo for others to join him. About 200 animal lovers turned up and began a stand-off that was to last 15 hours.

"I was there in the first couple of hours," recalls Barden, who had responded because he thought these rescued animals would eventually need homes.

But it wasn't as simple as that. Many of the dogs had infectious diseases. Others were too big to be adopted in Beijing (the capital imposes size limitations on dogs within key districts). While the rules are routinely ignored, the police can take animals away on suspicion and, unlike the dogs that fall within the limits, which will be returned if the owners pay fines, large dogs will simply never be seen again.

The justification for this policy, says Peng, is probably a cultural assumption that big dogs are aggressive. Before 1993, private ownership of dogs was banned within the city. The only dogs Beijing residents probably had contact with were large guard dogs specifically trained to be aggressive.

Furthermore, the number of deaths from rabies rose from five in 2011 to 13 in 2012. And because it was found that most victims were bitten by their pet dog, not random strays, it was decided to strictly enforce the laws on dog registration.

Barden is not confident that these measures actually help reduce the number of rabies deaths in the city. For one, the cost of registering a dog with the police is relatively expensive: 1,000 yuan (HK$1,255) for the first year and 500 yuan every year thereafter.

A free rabies vaccination is offered to those who register but many pet owners will simply do the maths and (at best) get their unregistered dogs vaccinated. Cat owners are under no obligation to either register or vaccinate their pets.

"The [dog registration] policy is out of step," says Barden. "They won't achieve the goals they want to achieve … if the dog licence was cheaper, say, 20 yuan, way more people would register."

Calling the ban on big dogs "totally unrealistic", Barden adds, "Go online and see what people are selling. Golden retrievers, huskies, Tibetan mastiffs. Half this city are hiding their dogs."

Some of the big dogs Barden helped rescue from the truck are still living at his shelter. Because they can't be adopted by people living within the most populated districts of Beijing, he is thinking of starting a programme to find them homes in America.

The new wave of animal rescuers, including Barden, are finding more success than their predecessors, as they have much better social networks and have employed creative means to raise money.

Lucky Cats rehomes about 200 felines a year and performs TNR on feral cats living in Beijing parks. It currently shelters about 40 animals waiting to be adopted.

The interior is well organised, with a medical room for sick and unadoptable cats and a loft for shy moggies still learning to socialise with humans. The main room has high perches and cat-friendly furniture that would look more at home in Tokyo's famed cat cafes than in an animal shelter.

"We used to have 70 [cats] in here," says Zeng Li, founder of Lucky Cats, "but they get anxious and were more prone to illness." She affectionately strokes the cats lounging on her desk, before adding, "People think [all I do is] play with cats all day."

The whiteboard over her desk, which displays a rather complicated medication chart, says otherwise.

Lucky Cats doesn't have charity or NGO status but operates as a social enterprise. Its activities are funded by proceeds from the sale of its cat-themed trinkets on Taobao. Li, who worked in IT before she started Lucky Cats, says the organisation also provides logistical support to some 300 TNR groups in Beijing. Many of the animals that call Lucky Cats home come from these groups. The feral cats are sterilised and returned to the area in which they were found, while the rest are kept in the shelter until a suitable home is located.

Li says she was moved by the sad fate of Beijing's street cats after she bought her first moggy from a local market years ago.

Lan also credits her first pet, bought from a puppy dealer, with opening her eyes to the suffering of stray animals.

"My dogs are so happy and healthy, so I wondered why [street dogs] should have to suffer."

Peng says, "In general, not enough people [in the mainland] have grown up with a pet in their life."

It is the people who have experienced the love and joy you get from a pet who have started to advocate for change, she adds.

"These are the people who start to think, 'Does my pet feel sad? Does it feel pain? Does it hurt when it is treated or handled in a certain way?' This is what I have seen start to seep into our collective consciousness as a society, which I find very exciting."