In the animal world, a good parent can be hard to come by. Most snakes will abandon their eggs, harp seals nurse their pups for just 12 days before leaving them on the ice (where they stay for up to six weeks without eating before entering the ocean on their own), and some animals, like hamsters, will eat their own young. Don’t lose hope, though. In rare cases, another animal will take up the task of parenting, regardless of size or species.

1. AN ORANGUTAN CARES FOR TIGER CUBS

When humans began caring for four tiger cubs at The Institute of Greatly Endangered and Rare Species in Myrtle Beach, S.C., one orangutan resident, Suryia, wanted to lend a hand, too. Robert Johnson, a senior trainer at the preserve, told ABC News that “Suryia showed genuine interest in the cubs when the humans were feeding and caring for them ... Suryia started mimicking the human care giving behaviors and became very connected to the mothering process, which is particularly interesting for a male orangutan.”

2. A DOG TAKES IN A MONKEY

In 2006, Babban Yadav brought home a baby monkey, which, at just a few weeks old, had been found lying on the banks of the Ganga River near death; its mother had been killed in an accident. Once in Yadav's home, an unlikely surrogate parent stepped in: Guddi, Yadav's Pomeranian. The dog adopted the little monkey immediately, nursing it and letting it ride on her the same way it would ride on its mother. "This is really a very bizarre union where you have a dog nursing a baby monkey," Yadav said. "It's just a demonstration of a mother's love."

3. A DOG ADOPTS A SQUIRREL

In another example of canine adoption, this Papillon, named Mademoiselle Giselle, adopted a baby squirrel while preparing to give birth to her own babies. Her owner, Debby Cantlon, originally agreed to take the squirrel—now named Finnegan—when someone asked her to nurse the orphan back to health. Mademoiselle Giselle dragged the squirrel’s cage over to her bed twice, and eventually took Finnegan in as part of her litter.

4. A BABOON CARRIES A BUSH BABY

The Nairobi Animal Orphanage houses many animals who have been hurt or orphaned. Among its inhabitants were a Galago (bush baby) named Bushie that was adopted by a juvenile yellow baboon named Dina, which professionals say is unheard of: "This is not normal," warden Edward Kariuki said. "It has not happened here [before] and I guess it has not happened anywhere else."

Still, there's probably an explanation for the unlikely pairing. "Female baboons are fascinated by infants their whole lives," one expert told National Geographic. If she were in the wild, Dina would be spending her days playing with juveniles her own age and peering at the infants in her group. Bushie, meanwhile, chattered at Dina like she would her Galago mother.

5. A CAT NURSES A PITBULL PUPPY

Lurlene, a cat at the Cleveland Animal Protective League shelter, had just given birth to a litter of kittens when a humane officer discovered this baby pitbull in a garbage can in 2013. The officer brought the day-old pitbull to the shelter, and the staff decided to put the puppy—who they named Noland—in with Lurlene. According to APL director Sharon Harvey, "Lurlene welcomed Noland into her family, nurturing and nursing him as if he was one of her own. And the kittens were fine with him, too."

Noland's mother, a dog named Molly, was later found, chained to the back of the house near where the puppy had been discovered. Emaciated and afraid, she was unable to take care of him, so he grew up with Lurlene and her kittens. Though the staff was concerned he might get too big, "Lurlene had things under control and it didn't take the kittens long to learn how to put him in his place," Harvey and the shelter's director of development, Judy Hunter, would say later. "Actually, Noland blended in with the family so well, he was even found using the litter box a few times." Eventually, Noland was placed with a litter of foster puppies, and, later, reunited with his mother at the shelter for play sessions. (Molly's owner was convicted of animal neglect.)

Lurlene and Noland's relationship helped the shelter out, too. The Petco Foundation helps animal welfare groups with awareness projects and grants. When the foundation found out about the adoptive family, they awarded APL $25,000 to help with future projects.

6. A WILD BOAR CARRIES A JAPANESE MACAQUE

A Japanese macaque named Miwa-chan was rejected by its parents at the Fukuchiyama Zoo in Japan, and had to be raised by his keepers. No one expected him to become such great friends with Uribo, a wild boar who also lived in the zoo. Miwa-chan would often cling to Uribo's back, just as the little monkey would have done to its mother. Soon, the duo became YouTube sensations; one video garnered more than 22 million views. The pair were given their own enclosure together at the zoo, and some literal piggy-back riding still happens, even though Miwa-chan is no longer a baby.

7. A CAT TAKES IN A SQUIRREL

In 2012, 8-year-old Bailee Shultz was playing in the woods when he heard something crying. It turned out to be a baby squirrel, so young its eyes weren't yet open. His grandparents, Nowell and Stephanie Box, collected the little squirrel and put it with their cat, Oreo, who had just given birth to a litter of kittens. Oreo didn't immediately accept the squirrel, which Bailee dubbed Bushytail, but nursed him anyway.

Bushytail lived with the cats for a few months before going off on his own, but he would return occasionally to see his adopted family. “He would play with [the kittens] like he was a cat,” Stephanie said. “One time he jumped on a cat’s back, and the cat just started walking, dragging his little feet behind it. It was almost like he was going for a ride.”

8. A DOG ADOPTS BABY TIGERS

When a tiger at a private safari park in Caney, Kans., gave birth to three tiger cubs in 2008 and immediately abandoned them, Isabella, a golden retriever, took the cubs in. “It was basically a do-or-die situation," park owner Tom Harvey told TODAY, "and Isabella stepped up to the plate and hit a home run.” The dog raised the tigers for about a year before they just got too big to be left alone with her, and were transferred to their own area of the park. The publicity from the unlikely family brought lots of attention (and visitors) to the safari park, saving it from being shut down.