How are the maternal instincts for an animal from Species A, triggered for an animal from Species B?

Question

CANEY, Kan. - A dog at a southeast Kansas zoo has adopted three tiger cubs abandoned by their mother. Safari Zoological Park owner Tom Harvey said the tiger cubs were born Sunday, but the mother had problems with them.

A day later, the mother stopped caring for them. Harvey said the cubs were wandering around, trying to find their birth mother, who wouldn't pay attention to them. That's when the cubs were put in the care of a golden retriever, Harvey said.

Harvey said it's unusual for dogs to care for tiger cubs, but it does happen. He said he has seen reports of pigs nursing cubs in China, and he actually got the golden retriever after his wife saw television accounts of dogs caring for tiger cubs.

Puppies take about the same amount of time as tiger cubs to develop, and Harvey said the adoptive mother just recently weaned her own puppies.

"The timing couldn't have been any better," he said.

Answer 1

I think its the fact that the mother had just weaned her own pups so giving her new babies to take care of fills in the gap of not having her pups.  

I have parkeets and they have been taking care of cokatiels the babes look quite different but they take care of them as if they can't tell the difference but it only seems to work with parents tat had just laid eggs or lost an egg.

Answer 2

It is hormonal. Women who are about to give birth develop

hormones that gives them the urge to both love the child and care and feed it. Animals have the same. I have seen

many picures of all different species caring for the young of other species. I have seen photos of cats nursing  puppies,

baby rats, baby mice, baby squirrels, dogs nursing kittens,

piglets, squirrels etc. Go on Youtube and you will find tons of video examples of this.