When young animals lose their mothers to poachers, accidents or predators, they can't survive on their own in the wild. But thanks to dedicated volunteer caregivers at rescue centers around the world, many of these creatures are getting a second chance. Airing Sept. 23 and 30 on PBS, the two-part documentary "Nature's Miracle Orphans" travels to Costa Rica and Australia to depict the intensive care that goes into saving baby sloths, koalas, kangaroos, wallabies and fruit bats and preparing them for a return to their wild habitats.

"There are some really heartwarming and lovely stories in the series," says producer Mark Wheeler, who joined the BBC project early on and "set about looking for the best places to go and people to film at rescue centers." Costa Rica and Australia were ultimately chosen because they're "very different countries, but the problems for the wildlife are very similar. Both have long roads bisecting habitat and mothers that carry infants, especially arboreal animals can get hit by cars and attacked by dogs on the ground." Others fall victim to electrocution or are separated from their offspring in the black market pet trade.

A quick look at each country reveals how volunteers are meeting the orphaned animals' needs. At Australia's Cape Otway Conservation Center, a baby koala is fed every two hours, given a teddy bear for comfort and taught chase games to build the muscles he'll need to climb trees. Elsewhere Down Under, Bev Brown swaddles baby fruit bats in blankets and bottle-feeds them while Stella Reid teaches a young kangaroo the behaviors he'll need to join adults that roam wild outside the sanctuary. In Costa Rica, the Sloth Institute's Sam Trull plays surrogate mom to orphan sloths that cling to her 24/7.

Trull, who currently cares for ten young sloths, including two that are about to be released, relies on donations to keep her sanctuary going. "I always wanted to work with animals. When I was really little, I thought I wanted to be a paleontologist and work with bones of animals, but it was always related to animals somehow," she says. "I did undergrad in zoology, and my master's is in primate conservation. I've been working with primates since I was 16. I'm a little bit of a traitor because now I totally work with sloths, which are not primates. But the first time I met a sloth, I fell in love. They're amazing. They're also underdogs, because people think they're lazy or cute; there is nothing to them beyond that. But there's so much more to them. They’re very intelligent. They are absolutely not lazy. They're just efficient at conserving energy. But they need their mothers, and I was drawn to help. My entire life is dedicated to the sloths now, which can get a little overwhelming at times," she admits of her very attached charges.

Sam Trull and Monster the sloth hang out during 'Nature's Miracle Orphans'"Sloths ride around on their mothers for the first year of their life, physically clinging to them for warmth. Having them on my body, they get warmth on their stomachs, which is a very important a sloth because the bacteria in their stomach needs warmth to survive," Trull explains. "Also, clinging to me helps build their muscles. They come out of the womb being able to cling onto their moms, but they're building their muscles and practicing that. Then there's the emotional aspect. It sounds anthropomorphic to say they need to be loved, but that's the only way I know how to describe it. They need to feel safe and comfortable in order to grow up and learn the things that they need to learn and be curious enough to explore, because if they're scared, they're just going to want to run away and hide. If they're confident and feel protected, they start to behave more like a sloth."

Trull's ultimate goal is to release all the sloths she cares for, no matter how attached to them she becomes. "At some point, I have to let go and let them live their lives." She hopes that viewers come away with the desire to help them, via her nonprofit or otherwise. She worries that some smitten people might want to buy a sloth for a pet. "That's the absolute last thing that we want because [black marketers] literally take them from the wild as babies. They rip them from their moms, and they sell them on the pet trade. And they have to take more than just one in order to even have one that survives because they do so poorly," she points out.

The popularity of sloth videos "is great on one hand, because it can raise awareness to the issues that we are trying to fight, but it can be a double edged sword in that it can also spark an interest in owning them," Trull says. "It's important that whatever information that we disseminate is educating and actually shows that, yes, they're cute, but that doesn't mean you get to have one."