(CNN) -- While rescue workers continue to search for human survivors in the rubble of buildings destroyed by Japan's earthquake and tsunami, animal welfare groups are leading efforts to rescue Japan's animals.
Isabella Gallaon-Aoki of Animal Garden Niigata is currently in Sendai, a coastal city badly damaged by the tsunami.
"The animals are dying by the day," she said.
"It's cold here, they have no food. Dogs in Japan can be tied up, especially in rural areas, and the dogs who are tied have no chance of foraging for food or anything so I'm sure they're in a pretty desperate condition."
But Gallaon-Aoki says efforts to rescue animals in the region have so far been hindered by a severe fuel shortage and damage to roads, which has made it difficult to access coastal areas.
"So far we've seen the very worst areas where there is basically nothing -- I mean everything has been completely wiped out, there's no sign of life at all, it was total destruction," she said.
"What we're going to do from now on is go out to the areas where we think animals have been left and we're hoping there's a chance we can find some alive."
Animal Garden Niigata is being assisted by a volunteer veterinarian from U.S. organization World Vets.
World Vets CEO Cathy King said: "It's probably going to be a few days before there's going to be a lot of serious animal rescue going on inside the main disaster zone because access is so restricted, and obviously the focus right now is on finding any people that might be there.
"But one of the really big issues is that there are a lot of people -- especially foreigners -- fleeing the country and leaving their animals behind.
"Shelters are getting calls from people saying 'I'm on my way to the airport, I'm leaving, I have four dogs left in my apartment and my neighbor has the key.'
"The urgent thing right now is taking care of those animals."
David Wybenga, an American living in Japan, is the director of Japan Cat Network, based in Shiga Prefecture, about 550 kilometers south-west of Sendai.
His group has joined forces with Animal Garden Niigata and animal welfare group HEART-Tokushima to form Japan Earthquake Animal Rescue and Support.
Wybenga agreed that the biggest challenge at this stage is helping animals left behind by those escaping the disaster.
He said: "What has emerged is that people in less affected areas are deciding to leave those areas: some embassies have decided to call back their nationals, some international schools have decided to close, some educational programs have said, 'this is enough let's bring you all back.'
"Suddenly they have to leave and depending on the country you have to go to there are procedures for traveling with a cat or dog, and if you're leaving suddenly you're probably not ready -- you don't have the necessary papers.
"We are trying to reach out to those kinds of folks and we will do our best to take their pets and hopefully to reunite them with them when they return, but that's going to be something with a lot of unknowns."
King said World Vets has previous experience helping animals after natural disasters, including working in Haiti after its earthquake last year, and in the United States in the aftermath of Hurricane Katrina in 2005.
She said one problem that emerged after Katrina was that because pets were rescued by different groups and taken to different locations, their owners were often unable to trace them, meaning the animals had to be adopted.
It's a scenario King wants to avoid in Japan. She said a priority would be to set up a centralized database of rescued animals, containing information about where and when they were found and where they were taken.
She added that World Vets has four teams of four volunteers -- veterinarians, translators and animal workers with experience of natural disasters -- on standby, ready to fly to Japan once it has identified where their expertise is most needed and will be most effective.
King believes that in the weeks to come their efforts will include helping agricultural animals as well as pets, a situation that will strain the resources of Japanese animal welfare groups.
"Really the biggest issue is that these shelters are all going to be totally overwhelmed with animals," said King.
"The groups have areas for sheltering animals but they're already filling up. They've reached out to us -- they need some kind of warehouse or prefabricated buildings or enclosures where they can start housing animals in individual cages -- so we're trying to help them with finding that."
She added: "Pets are very meaningful to people in Japan. People love their dogs and cats there -- a lot of people have pets that are part of the family."