Luna update: February 2022

2021, The year of Luna with Sol

We added Luna and Sol to the Urban Sloth Project in March 2021. Once Luna was fitted with a collar in March, we were able to track her and baby Sol every day. We estimated baby Sol to be around three or four months old at this time, but sloths are very difficult to age–we were unable to weigh Sol, which is usually the best way to guess a baby sloth’s age.

In August we began to see Sol becoming more curious about his surroundings; at first, it was only a limb or two reaching into the liana vines, but one day we came to track them, and we found him sitting next to Luna instead of on her belly!

He wasn’t quite ready to leave Luna entirely, and there was a lot of him going back and forth between his mama and the branches. We felt like proud parents watching little Sol gain his independence.

Becoming independent

By October, we confirmed that baby Sol was all grown up! We had consistently seen him separate from his mother, until one day they were no longer sharing the same tree.

In most mammals, once the parents raise the young to independence, the young are expected to disperse and find their own territory. With sloths, once the baby is ready, the mother leaves them with a portion of her own territory and moves on herself.

We were able to witness this with Sol, to whom Luna left her very favorite tree, while she moved further south. Luna moved all the way to the other side of the lot they occupied, leaving the tree she raised her baby on to her grown-up boy. According to our calculations, Sol gained independence at 10 months old.

December: Sol is finally grown up

We still tracked Luna every day, but with no radio collar, it has been hard to find Sol! We have seen him around a few times in his little territory that borders his mother’s, but if he decided to make a big move we probably wouldn’t know about it. Luna has continued to thrive in the new, more southerly portion of her territory, which she shares with a number of other sloths.

One Saturday in mid-December, when the tracking team went out to find Luna, they instead found massive deforestation occurring, with chainsaws and bulldozers cutting down their trees. Happily, the community made a big protest about this, the tree felling was stopped, and has not resumed while the relevant authorities are looking into it.

Read More: The community of Puerto Viejo came together to stop habitat loss

A new year, a new baby!

We’ve been waiting for it ever since Sol moved on to find his own territory, and the day has finally arrived: Luna has a new baby! Baby Celeste was born in the last week of January (2022), and is sooo tiny!

Luna and her new baby, Celeste. Can you spot the antenna?

Luna probably went into heat and conceived shortly after Sol started independently exploring in August. Although we are not precisely sure of the gestation period of three-fingered sloths, we estimate it is approximately six months. Researchers have not yet had the opportunity to observe a three-fingered sloth during the entirety of her pregnancy, so this gestation period is still being determined.

Read More: Sloth mating: not as slow as you think

sloth mom and baby — We think Luna is quite young, but as it is nearly impossible to determine the age of a wild sloth (until we can afford some telomere analysis) we are mostly guessing. She does not have the full complement of green algae on her fur that would indicate a completely mature fur ecosystem, but she does have a nice patchwork of browns and greys that is quite fetching.

Luna’s territory is a good one for sloths

Or it would be if they’d stop cutting down the trees. Several three-fingered mothers are known to inhabit the area. Thus when Sarah stopped by Luna’s territory while covering a shift for Ames (who was quarantined with Covid) she did not immediately recognize the mama sloth with a days-old baby velcroed to her side as our lady Luna.

sloths in guarumo after deforestation — Luna shares her territory with more sloths.

Since the area’s deforestation in December it’s not unusual to find crowds of tourists gathered around the lone guarumo trees, watching and snapping pictures of the half dozen three-fingered sloths that can be seen on any given day. When the crowds are looking up, we know everything is in order and the Sloth Star of the Day is high in the trees and safe. When the crowds are looking down at the ground, we know there is most likely a sloth trying to get somewhere, and it’s time to intervene. The intervention consists of politely explaining to people that the sloths are not here to meet them and asking the tourists to give them a little space so the sloths can get where they are going.

This is what was happening on a Friday when Sarah spotted a crowd and went to see whether the sloth needed an advocate or not. The sloth in question was crawling across an obstacle course of felled trees and organic debris, trying to get from one tree island to the next.

At first, Sarah was quite confident that no, this was not Luna–because look at that tiny baby!–but once she pulled out her own phone camera she was able to zoom in and see the antenna of Luna’s tracking collar. Our favorite mom was a mother all over again.

Sarah got some great footage to use as evidence that reforesting and bridge-building in this part of the maritime zone needs to be made a priority, because who can resist helping out baby sloths?

Read More: Baby sloths, everything you always wanted to know!

At least now we know why Luna disappeared on us for a few days; clearly, she just wanted some peace and quiet to deliver her new daughter, currently weighing in at around 300 g. That’s about 10 oz, or about two average-sized smartphones. (For the record, we don’t actually know that the baby is a girl. Right now we’re guessing, and we figured since we called her last baby a boy we needed to even up the gender ratio a bit.)

Though he won’t contribute much to raising little Celeste, we think we know who the father is, as there is only one mature male in Luna’s territory. We don’t have a name for him, but maybe his newest daughter will grow up to look like him!

Read More: A Little Taste of Heaven, Tracking Diaries #8

The babies of Luna

The sex of the babies will remain a mystery for some time as all genitalia are hidden internally in three-fingered sloths. The best and least invasive way to determine male from female is to look out for the brightly colored speculum that develops on all male Bradypus sloths (with the exception of the maned sloths). Unfortunately, the speculum does not develop until sexual maturity (at approximately two years old) which means that it can be difficult to know the sex of sloths before this point.

-SloCo Team

A Little Taste of Heaven: Tracking Diaries #8

I’m standing amongst the wreckage of felled trees and bulldozed undergrowth, my boots crunching on dead vegetation, but I’m not looking down.

I’m looking up. I’ve heard from Sarah that Luna has a new baby, just days old, and I haven’t seen her yet.

I haven’t seen much of sloths lately, it feels like. Between my other duties over the holidays and a couple of Covid scares I’ve become a little too intimately familiar with the view from my desk, the exact number of dead pixels on my computer screen, and the utter indolence of my cats, who literally do nothing other than sleep and demand food.

It feels a bit disorienting to be out in the field again. The last time I was this deep in Luna’s territory, it had more trees and less gravel, before some jerk came and tried to pave the place over. I watched from the other side of my phone screen as SloCo came to the rescue and notified the appropriate authorities of that transgression, and cheered through my coughing fits as my the community saved the remaining trees from the heavy equipment and sweated through a blistering hot day to put up fence posts to keep the tourists’ cars from finishing what the bulldozers had started.

It was in the dead branches of some of her former trees that Sarah found Luna and her new baby, trying to crawl to a safe haven through the twisted roots and twigs and spiders. Sarah reported that Luna arrived in her new tree safely, and it is now my job to figure out what the heck tree that actually was.

Our tracking equipment is being even weirder than usual. According to our radio receiver, Luna has in fact boarded a raft and is bound for—a quick check of Google maps—Aruba. It’s possible that the jungle has rusted some secret but essential piece of electronics deep inside the receiver, or that I’ve forgotten how to track sloths, or maybe that the antenna is possessed by demons.

(Note so self, Google “how to do an exorcism” when I get home. Don’t tell my boss.)

I’m still fiddling with the equipment when I have one of those perfect sloth tracking moments: I just happen to look up at a movement out of the corner of my eye and catch a slow-moving silhouette on the side of the guarumo tree. Quick as a cat, I whip out my binoculars, and then fist punches the air as I spot a three-fingered female with an itty bitty little replica of herself clinging to her fur. Another minute confirms the radio collar on her neck—this is definitely Luna!

The receiver is still insisting that Luna is somewhere out on the Caribbean waves, so I turn it off and instead pull out my phone, snap a few pictures, and then settle in for a good look at her.

Baby sloths are cute on a level that maybe ought not to be legal. They almost don’t look real; they’re just arms and eyes and fuzzy cuddles incarnate, like the living manifestation of a hug.

By now a crowd has gathered around me to marvel at the sloths. Luna has settled onto the branch she was after and gone to sleep. Watching them, I have to smile. Luna’s territory will take a long time to regrow, but here in front of me is proof that new life, and new growth, is always possible. We have named the baby Celeste, which means “heavenly”. It is also the Spanish word for the color of a clear sky in the daytime.

If you want a little taste of heaven, sometimes all you have to do is look up.

-Ames Reeder

Three-fingered sloth ‘adopts’ a two-fingered sloth baby!

These two sloths are not only different species, but they belong to two completely different families, separated by over 30 million years of evolution. Cross-species adoptions like this are incredibly rare in the wild, with only 3 other documented observations of this happening.

What happened?

On the 20th December 2020, Gerald Pereira and Oscar Solano Rojas were guiding a group of tourists in Costa Rica. Sloths are a common sight on these tours, but that day they saw something that they had never seen before – nestled quietly amongst the rainforest canopy they spotted an adult three-fingered female tending to a two-fingered baby sloth.

Read more: Is Costa Rica the best place in the world to see sloths?

Gerald and Oscar, both with over 11 years of experience working as ecotourism guides, knew they had witnessed something important.

The curious pair were observed in a fragmented strip of rainforest, sandwiched between a river, a pineapple plantation and a busy road. According to Oscar, “in that area, local people take great care of the sloths, so we always go to look there because there is a very large population”.

“Yesterday we started the tour, which we call the ‘Sloth Tour’, as usual. To see them active in the early hours of the day, we started the tour at 6am. Around 8am we arrived at a place where my partner Gerald and I saw a sloth hanging from a Cecropia tree. At first, it did not attract much attention, we saw that she was a female and a baby, but that morning we had already seen 3 baby sloths, and we did not think it was anything special or different from what we had seen. When we paid more attention to them, however, we discovered that it was a three-fingered female and a two-fingered baby.”

“I had already seen the two species in the same tree many times, and at first we thought it was just a coincidence that they were there together. When we found them it seemed like they were waking up. They both started scratching, and then the baby separated from the female, fed on cecropia leaves a little, and I thought that was the end of the interaction.”

“But then you see how the baby returns to the female, and she receives it with total naturalness, that is what surprised us the most. None of us who were there could believe it, neither Gerald nor I, because we had never seen it before. It left me astonished. In rescue centres, I had seen a certain attachment between the two species, but never in their natural habitat, as happened to us yesterday.”

As can be seen in the video footage captured by Gerald and Oscar, it does indeed appear that the two sloths interact with the gentle tenderness of a mother-baby relationship. When they returned to the area the next day, they once again found the pair snuggling together in a shady spot in the canopy. It certainly looks like the bond between these two sloths is much more than just a fleeting interaction. It appears as though the female has formally adopted this baby as her own.

Odd Alliances

Adult animals adopting unrelated young is nothing new to science, but in most cases these are intraspecies interactions – meaning that they occur between two unrelated individuals of the same species. This has most commonly been observed within sociable species, often herd or pack animals.

Interspecies adoptions – where a female adopts a baby of a different species – is an altogether much rarer occurrence in the wild. In fact, there have only ever been 3 other documented instances of this happening, and it has never before been observed in sloths.

In 2004, a group of capuchin monkeys were documented caring for a baby marmoset, and in 2014 a bottlenose dolphin adopted a baby melon-headed whale and nurtured it for it for 3 years. More recently, a lioness in India was found to have adopted an orphaned leopard cub in 2018 and she raised it alongside her own offspring.

Why do cross-species adoptions occur?

In evolutionary terms, caring for another animal’s offspring like this doesn’t make much sense. Raising a baby demands a lot of time and energy (something which a sloth has a limited supply of), and it is usually done with the purpose of propagating an individual’s own genes. So why do cross-species adoptions like this sometimes happen?

The truth is, scientists are still trying to understand it. Because these events are so rare, there isn’t much information available and each observed case appears to be very different. There are two popular theories:

Instinct: A lot of adult female animals are biologically hardwired through evolution to care for helpless infants. A cross-species adoption might occur accidentally after a female has recently given birth herself, when high levels of the hormone oxytocin encourage her to bond with the orphaned baby (even if it isn’t hers!).

Mutual benefit: If the benefits of the raising an unrelated baby outweigh the costs, this could explain why some interspecies adoptions take place. For example, it could be beneficial for a group of animals to add a new individual that would help to secure more food, or provide added protection. In some social species the simple benefit of companionship may be a driving force! This is unlikely to be an important factor for our solitary sloths though.

*Lioness, Nosikitok, nurses a leopard cub in the Ngorongoro conservation area in Tanzania. Photograph: Joop van der Linde/AP*

How did this happen?

The circumstances surrounding this adoption are not entirely clear, but SloCo founder and sloth expert Dr. Rebecca Cliffe has some ideas about what might have led to this unusual event.

“This is the first time that anything like this has ever been seen before in wild sloths, and it is certainly very interesting. I am used to sloths surprising us, but this has to be one of the most unusual things I have heard about. I suspect there are three possible scenarios which may have led to this happening:

1) Accidental human interference. Maybe someone found the baby sloth alone and tried to ‘reunite’ it with its mother, but accidentally paired it with the wrong sloth. Reuniting baby sloths with their mothers is a surprisingly common requirement for people in Costa Rica as babies are often found alone on the ground after falling from the tree.

A lot of people don’t realise that there are two very different types of sloth, and so they might not have realised what they were doing. In this situation, however, I would expect the adult sloth to reject the baby and so this feels like an unlikely scenario

2) The baby sloth lost it’s own mother, and instinctively clung onto the fur of another sloth. Baby sloths are born with a strong instinct to cling onto mom’s fur, and if they are separated, they tend to cling onto the next best thing. It isn’t impossible to think that this baby may have climbed onto the three-fingered sloth after becoming orphaned. However, in this situation I would also expect to see the adult sloth looking agitated and stressed out by her new uninvited companion – and I doubt the relationship would last more than a few hours.

3) The baby sloth lost its own mother, and the adult sloth recently lost a baby of her own. This unusual combination of events would provide a feasible opportunity for the pair to bond naturally due to a mixture of instincts and hormones. Although extremely rare, I think this is probably the most likely scenario!”

What happens next?

This unprecedented behavior leaves all of us with many questions – particularly regarding the welfare of both sloths! Will the baby survive? It’s certainly possible. While they are different species, they do share a broadly similar ecology.

The diets of both sloths overlap heavily, with both being predominantly folivorous (eating only leaves). Two-fingered sloths tend to be more flexible and adaptive with their choices, while three-fingered sloths are more selective about what types of leaf they will eat. With both species, babies maternally inherit knowledge about which trees are safe to feed from – and this arrangement may work in the baby’s favor!

Furthermore, it appears as though the baby sloth is approximately 7 months old. At this age, the baby would not be as reliant upon a steady source of milk from the mother as the natural weaning process would be taking place. Although the adult female could be producing milk, we don’t think this is essential for the survival of the baby at this stage.

Two-fingered sloths are also much larger than their three-fingered counterparts when fully grown, which means that the adoptive mother may have a challenge on her hands when lugging around her overgrown offspring.

But what happened to the baby’s biological mother? This remains a mystery. Considering the location in which the pair were observed is highly disturbed, it may be that she got into trouble with the busy road or nearby pineapple plantation. Or perhaps there was an accidental baby mix-up, and somewhere in the rainforest, a mother two-fingered sloth is tenderly nurturing a baby three-fingered sloth. It’s doubtful we will ever know for sure.

While there are certainly a lot of challenges for this pair to overcome, here at SloCo we have high hopes for their survival. After the unprecedented global difficulties that 2020 has brought, we are happy to embrace this heart-warming story (which has all the makings of a future Disney movie!).

We will be working closely with both Gerald and Oscar to monitor the two sloths as time goes on – we will keep you updated on their progress! For now, we are keeping our fingers and toes crossed for a happy ending.

2021 Update:

It’s with a heavy heart that we must inform our supporters that the wild three-fingered sloth mom that was found to be caring for a two-fingered baby has passed away.

Local guides who were tracking the pair witnessed the mom and baby fall from their tree. Unfortunately, mom did not survive the fall. The baby was uninjured and climbed back up into the tree.

The guides continued to watch over the baby for the rest of the evening, and returned to the spot every day to check on him – but after three days he had ventured off on his own into the rainforest.

We estimate that the baby was around 8 months old, at which point he would naturally begin to distance himself from his mom. Team Sloth is optimistic that his two brilliant sloth moms taught him everything that he needs to know in order to survive in the wild!

-Sloth Team