It may be one of the largest animal "migrations" across the island.
By the end of next year, more than 1,000 stray or abandoned dogs and about 800 cats housed in shelters in Pasir Ris Farmway will have to leave. The authorities want the land for industrial development.
The dogs, which make up the bulk of rescued ones here, will likely move to Sungei Tengah in Kranji, where the Society for the Prevention of Cruelty to Animals (SPCA) is located.
Tenants of Pasir Ris Farmway were told by the Singapore Land Authority (SLA) in a letter last week, which The Straits Times has seen, that the land must be returned to SLA by Dec 31 next year.
The Straits Times understands that SLA has been sending letters monthly to tenants about the Dec 2017 deadline since July.
But it did not provide details on when the Sungei Tengah sites will be available for tender or how big the plots are, causing uncertainty for the animal welfare groups.
"The process of bidding for the land and waiting to be successfully awarded will take time," said Mr Derrick Tan, president of Voices For Animals, which has more than 100 dogs.
"Preparations and building a new shelter will take months. If all these are not done in time, the animals have no place to go."
In a joint statement to The Straits Times, the Agri-Food and Veterinary Authority (AVA) and SLA said details of the tender will be provided when ready.
There are 14 farms in Pasir Ris - eight are ornamental fish farms, five are pet farms and one is a food fish farm. There are seven animal welfare groups - including Voices For Animals, Animal Lovers League and SOSD - located in some of these farms, said the authorities.
Individual volunteers, who are not affiliated with any groups, also house rescued animals in commercial boarding facilities there.
Housewife Lee Lee Sim, 54, who rescued three dogs from the streets, said: "For me, I can find another commercial boarder to house them, but what about the animal welfare groups with more dogs?"
Cost is another issue.
Dr Siew Tuck Wah, president of animal welfare group SOSD, which cares for about 100 dogs, said AVA officers had suggested to him during preliminary discussions that the new shelters should be at least two-storey high.
But multi-storey shelters are more expensive to build, said Animal Lovers League founder Cathy Strong. With at least 300 dogs and 200 cats, Animal Lovers League is the largest shelter in Pasir Ris.
To give a rough idea of cost, SPCA's single-storey facility in Sungei Tengah cost $7 million, Ms Strong pointed out.
She added: "Our operating cost is already at least $60,000, which we have to pay every month on top of the construction fees. Where will we get the money from?"
Voices For Animals' Mr Tan said that while it would be more ideal for dogs to be given more space to run about in the sun, a multi-storey shelter in land-scarce Singapore could work. He added that there were such shelters in London.
The affected animal welfare groups in Pasir Ris also worry whether they can afford to compete with commercial entities, such as pet farms, in a tender, which could push up prices.
They have twice submitted proposals to the Ministry of National Development (MND) for animal welfare groups to bid for land under a separate category from commercial entities. An MND spokesman told The Straits Times that it is considering their request.
Dr Siew said: "They have not gotten back to us. The situation is urgent. All we ask for is an answer. If we do not get more information soon, moving out by next year is not a viable option."