Creature: Grazers

Grazing animals like cows, sheep, and goats, converting plant biomass into meat and bioactivated fertilizer that enriches soil.

Featured Creature: Fireflies

I flicker and float in warm evening air,
Like nature’s own fireworks, more care than scare.
No sound, just light as I drift and play
What glowing insect lights up your way?

Fireflies in upstate New York
Image credit: Alexandra Ionescue

Fireflies

We’re doing Featured Creature a little differently this week. Instead of a written piece, we’re publishing this conversation between Adrianna Drindak (Science Communications Intern) and Brendan Kelly (Communications Manager), with media and contextual commentary from Alexandra Ionescu (Associate Director of Regenerative Projects). 

Brendan

Hi Adrianna.

Adrianna

Hi Brendan.

Brendan

So, Alexandra Ionescu had this idea of exploring fireflies for Featured Creature this weekend. It’s obviously Fourth of July in the United States and we typically celebrate with fireworks, and she made this great observation from the woods in Upstate NY, about fireflies being nature’s fireworks, and I thought that was so great and left open so much room to explore not just the ecology and biochemistry, but also I think our collective childlike awe and fascination with them.

Alexandra

Exactly! Thank you both and I’m so bummed I have to miss the rest of this conversation, but yes I wanted to give a little more context.

This summer I shared a really beautiful moment with my dad while he was visiting from abroad.

I took him to one of my favorite spots in Upstate NY near my husband’s parents house to see the beavers. We went at dusk and were able to catch a beaver and a few tail slabs. It was nearly dark by this point and the path back to the car cut through the forest. And what unraveled was this beautiful transition from being in the presence of a beaver and observing its movement through the water, and then walking back to the car through the dark forest.

Except, it wasn’t.

The forest was lit up by probably thousands of fireflies. Wherever you looked you could see them flickering and communicating and signaling. There were rhythms and waves of dots and points and flashes of light dancing all around us.

And it’s fascinating to realize that firefly season coincides with the 4th of July, especially if we think of fireflies as nature’s own fireworks. (Only, it happens through chemistry, with absolutely no sound the human ear can detect, and no pollution.)

How does nature illuminate, versus how humans illuminate?

Maybe it all comes down to an intentionality of being—one that respects the web of life, that practices co-existence, where illumination doesn’t disturb the ways of other beings, but coexists alongside them—through silence, wavelengths, and chemistry.

So I invite everyone this weekend—and beyond—instead of going to see the violent, explosive fireworks, the human–made fireworks, go see nature’s own fireworks instead.

By Alexandra Ionescu

Brendan

Thanks Alex, that’s such a beautiful way to set course for this conversation and our hope is to circle back around to some of those themes by the end. Okay, Adrianna, what do we know about fireflies?

Adrianna

Thanks Alex! Yes, let’s talk about fireflies. Or lightening bugs, depending on where you live or grew up.

Brendan

I was raised in Kansas, they’ve always been lightening bugs to me.

Adrianna

As a New Englander, it’s fireflies.

Brendan

Agree to disagree.

Adrianna

Sure. So this probably won’t come as a surprise to anyone, but fireflies are unique in that they are one of the few organisms that are able to produce their own light.

Brendan

You’re talking about bioluminescence?

Adrianna

That’s right, bioluminescence. Oxygen inside the firefly’s light organ, or lantern, mixes with three other components: adenosine triphosphate (ATP), a molecule called luciferin and the enzyme luciferase. And researchers believe that different fireflies can give off different intensities of light that they’re producing based on the level of oxygen that’s being supplied to the light organ, to the lantern.

During that reaction, nearly all the energy is released as light, not heat. It’s one of the most energy-efficient light sources in nature.

Brendan

That’s really neat. I’m reading right now that they’ve even inspired energy-saving LED technologies. If Alex was still here I think she’d have a lot to say about biomimicry!

I see that one way LED designers have drawn from fireflies is by adding microscopic surface structures that help light escape more efficiently. In most LEDs, those structures are symmetrical, but fireflies have asymmetric, angled microstructures on their lanterns. This boosts light output in two ways: First, the greater surface area increases light interaction, so less of it gets trapped. And second, the uneven angles scatter the light more randomly, giving it more chances to exit. It’s really clever. I’ll send you the article. The close-up images are wild.

Adrianna

And kind of like how you can buy different color LEDs, there are different colors of light amongst fireflies.

Brendan

Oh, interesting. Is it involuntary? I was reading about how, we can get into this in a second, but how the light is used to signal and communicate, where males will have their own flash patterns and specific sequences. So is what you’re talking about the mechanism by which that is controlled or are we talking about two separate things?

Adrianna

We’re talking about two separate things. Oxygen and chemical regulation can vary between species, which is why you get different colors and hues of light from different species of firefly. Separately, yes, each firefly can control the sequence of signals it sends.

But, it’s important to note that some firefly species are active during the day instead of at night. They don’t produce light, so instead of flashing, they communicate using pheromones.

Brendan

Yeah, I saw something similar in a recent report, just a couple years old. So…what do you call a lightning bug that doesn’t light up? Just a bug?

Adrianna

Well, technically fireflies aren’t bugs; they’re beetles.

Brendan

I’ll be honest I’m not entirely sure where that leaves us.

Adrianna

Communication.

Brendan

Right. One of my more recent feature creature articles was about African gray parrots and I focused pretty much exclusively on the communication aspect because what I love about those birds is that their vocalizations are hyperlocal and they have their own dialects based on where they live in the forest. Almost like accents. And it almost seems like there’s a similar phenomenon going on here with this sort of language of light.

Photo by Jud McCranie. Butler Island Plantation, Georgia

Adrianna

Yes! There are around 2,000 species of fireflies, which is wild to think about. When multiple species live in the same area, they each occupy a specific “signaling niche.” That means they might share habitats, but they’ll come out at different times of night, and they use distinct flash patterns to communicate. So even if they’re in the same place, they’re not getting their signals crossed, each species is speaking its own visual language, on its own schedule.

Brendan

That’s such a cool thing to know. If you’re observing fireflies in your backyard or local area, you can probably start to notice patterns, like what time they come out, how they flash. And then maybe when you’re somewhere else in the summer, you could compare what you’re seeing and pick up on the differences. I’m not sure if there’s a whole firefly-watching community out there like birders, but it’s fun to think about!

I was reading that the whole thing is kind of like a dance, at least when it comes to mating. The males are the ones flying around, flashing their little signals like peacocks, trying to get attention. The females stay on the ground or in low vegetation, and if they spot a male they like, they flash back. That’s how they find each other and connect.

Adrianna

That’s right. The male sends a flash of light and then the female will see the signal from a male of her species, and they communicate and find each other. They navigate their way towards each other through those sequences of flashes.

Brendan

It’s almost melancholy though because when you see them you get excited but they’re at the end of their life basically if you see them flying around flashing, right?

Adrianna

Yep. I’m looking at a diagram now and they are eggs for about 3 weeks, in their larva stage for about one to two years, in their pupa stage for about three weeks, and then they’re adults for only three to four weeks.

Brendan

Okay now I read this in a few reports so I have a degree of confidence about it. In some species, like Photuris fireflies, the females will actually mimic the flash patterns of a different firefly species to lure in unsuspecting males. The male thinks he’s found a mate, but when he arrives, it’s a total bait-and-switch…she eats him instead. It’s a wild example of aggressive mimicry.

Adrianna

That’s crazy.

Brendan

Yeah. Who knew the life of the lightening bug could be so hostile. But I guess on that point, it can be a hostile life!

Adrianna

It can, for sure. I came across a recent Penn State project studying threats to fireflies, and one key point was how climate change is affecting their development. For many U.S. species, the seasonal temperature patterns they rely on (warmer summers and cooler winters) are shifting. Unseasonal heat or cold can disrupt their life cycles. Changing rainfall patterns are also a problem: both droughts and flooding can interfere with firefly development at different stages.

Brendan

That makes sense. Fireflies usually need some level of moisture, so drier conditions are definitely a concern. But the issue of light pollution stood out to me. As cities expand and the night gets brighter, the bioluminescent signals fireflies use to find mates can get drowned out. If the flashing is less visible, then males and females may just miss each other altogether.

It’s a reminder that habitat isn’t just about physical space, it’s also about light, temperature, and other environmental cues that species depend on.

Adrianna

Definitely. I’ve never lived in a city before and I think it’s been really interesting for me to notice those kinds of changes and to think about those kinds of shifts in what organisms I’m seeing and which organisms I’m not seeing. I was just home last weekend in upstate New York like Alexandra, and we were walking in the woods and there were fireflies everywhere. And then I come back to D.C., where I’m living this summer, and it’s just very different.

Brendan

I didn’t see many fireflies when I lived in D.C. either, and I think that makes sense. When you’re out of the city, you can look up and see the stars clearly. But in the city, even on a clear night, you look up and the stars are hidden by all the light. And I think it’s probably the same for fireflies. To our eyes, a star and a firefly are about the same size. If we can’t see the stars, we’re not going to see the lightning bugs either. And more importantly, they might not see each other.

I’m sure pesticides are a factor too, but light pollution alone feels like a big deal.

Photo by Bernd Thaller. Graz, Austria

Brendan

Bringing this full circle, I’ve been thinking about how deeply embedded fireflies are in our collective memory, especially for those of us who grew up in suburban or rural areas in the U.S. They’re not like pets, exactly, but I’d still put them up there with cats and dogs in terms of how familiar and emotionally resonant they are. Almost everyone seems to have a memory: running barefoot through the yard at dusk, chasing little flashes of light, maybe at a cookout or camping trip. All of mine are social. Playing with friends, watching them float above the grass while the adults talked nearby. Even now, fireflies still feel special. You can’t be alone in the woods at night if there are fireflies all around.

There’s something about them that’s instantly nostalgic. Mention catching one in a jar and people don’t need an explanation…they just nod, like, “Yeah, I remember that.”

Adrianna

Yeah, and going back to how Alex opened this conversation with that contrast between fireflies and fireworks. On one hand, you’ve got fireflies, which have this quiet, calming, joyful presence. And then on the other, fireworks, which are loud and disruptive to so many living things. It’s just a really different kind of relationship you can have with each of them.

Adrianna Drindak is a rising senior at Dartmouth College studying Environmental Earth Sciences and Environmental Studies. Prior to interning at Bio4Climate, she worked as a field technician studying ovenbirds at Hubbard Brook Experimental Forest and as a laboratory technician in an ecology lab. Adrianna is currently an undergraduate researcher in the Quaternary Geology Lab at Dartmouth, with a specific focus on documenting climate history and past glaciations in the northeast region of the United States. This summer, Adrianna is looking forward to applying her science background to an outreach role, and is excited to brainstorm ways to make science more accessible. In her free time, Adrianna enjoys reading, baking gluten free treats, hiking, and backpacking.

Alexandra Ionescu is a Certified Biomimicry Professional, Ecological Artist and 2024 SUGi Fellow. Her aim is to inspire learning from and about diverse non-human intelligences, cultivating propensities for ecosystem regeneration through co-existence, collaboration and by making the invisible visible. She hopes to motivate others to ask “How can humans give back to the web of life?” by raising awareness of biodiversity and natural cycles to challenge human-centric infrastructures. At present, Alexandra is immersed in expanding her knowledge of ecological restoration through Miyawaki forests, beaver-engineered landscapes, and constructed floating wetlands. In her spare time, Alexandra is part of the Below and Above Collective, an interdisciplinary group that combines art with ecological functionality to build constructed floating wetlands. 

Brendan Kelly began his career teaching conservation education programs at the Columbus Zoo and Aquarium before relocating to Washington, DC. Since then, he has spent a decade as a journalist and policy communications strategist, designing and driving narratives for an array of political, advocacy, and institutional campaigns, including in the renewable energy and sustainable architecture spaces. Most recently before joining Bio4Climate, Brendan was working in tech, helping early and growth stage startups tell their stories and develop industry thought leadership. He is interested in how the intersection of informal education, mass communications and marketing can be retooled to drive relatable, accessible climate action. While he loves all ecosystems equally, he is admittedly partial to those in the alpine.  


Featured Creature: Markhor

What animal is the largest of the wild goat species, whose name means “snake eater” in Persian, and is the national animal of Pakistan?

An adult male markhor at the Stone Zoo, Stoneham, Massachusetts
Image credit: Sienna Weinstein

Not Your Average Billy Goat

While interning at the Stone Zoo in Stoneham, Massachusetts, one of my duties involved filling up large black food bowls with a carefully measured mix of various feed for the zoo’s markhor. Prior to this internship, I had never heard of this fascinating species of bovid. The males were majestic with their artistically-curved horns and strikingly-bearded chin; so of course, my lunch break that day was spent photographing these amazing animals. This was no easy task, as these creatures had the habit of moving just out of sight around their enclosure as soon as my camera was properly set. However, persistence paid off, and I managed to snap a few photos during the brief moments when the markhors obliged me by standing still.

At 4.5-6.2 feet (1.37-1.89 m) long, with females typically weighing between 70 and 88 pounds (39.9 kg), with some weighing upwards of 100 (45.4 kg) or 110 lbs (49.9 kg) and males weighing up to 242 pounds (110 kg), the markhor is the largest of all wild goat species. Males release a pungent odor which has been described as stronger than that of domestic goats, and is used to  repel predators, mark territory, and as a natural cologne to attract females during the breeding season.

There are a few examples of sexual dimorphism, or noticeable physical differences between genders, among markhor. Besides their differences in size, males have a longer coat, especially around the chin, throat, chest, and shanks. Females are typically redder in color compared with males, have shorter hair and beards, and lack the majestic mane males display along their neck. Both genders also sport an impressive set of corkscrew-like horns, which measure up to 10 inches (0.25 m) for females, but can exceed an astonishing 5 feet (1.52 m) for males! 

What’s In a Name? A lot for the Markhor!

Found primarily in Pakistan, parts of Afghanistan, and the mountain ranges of the Himalayas and Karakoram, the markhor is the national animal of Pakistan. In Pakistan, the markhor is known as the “screw-horn”, or “screw-horned goat.” The Persian words “mar” and “khor” mean “snake” and “eater”, respectively, leading to the moniker “snake eater” or “snake killer”. This moniker is in reference to the ancient belief that the markhor would actively kill and consume snakes! (Which is not correct–markhors are herbivores.) This regional myth is believed to stem from the “snake-like” form of the male’s horns, curling and twisting like a snake, possibly leading ancient peoples of the area to associate them with these limbless reptiles.

Capra falconeri distribution,  Shackleton, 1997

Native to the mountainous regions of South and Central Asia, the markhor has evolved powerful and flexible hooves with hard, large outer edges and softer centers to grip the rocky surfaces of the terrain. Their hooves allow them to scale sheer cliffs and escape predators such as Eurasian lynx, wolves, and snow leopards.

The markhor plays a crucial role within its ecosystem by contributing to the health of their mountainous habitat. Keeping the native plants in check, the markhor controls the growth of certain vegetation through their eating habits, even climbing trees to reach the tastiest bits. Markhors spend more than half of their day grazing, about 12–14 hours on average! They mostly feed on grass in the warmer months, but upon the arrival of winter, they switch to other plants, including shrubs and twigs. This seasonal shift from grazing (eating grasses and low vegetation) to browsing (eating leaves, shrubs, and woody plants) helps balance plant communities at different heights and root structures, which supports more diverse insect, bird, and herbivore populations. Their feeding habits prevent overgrazing and help to promote biodiversity by allowing a range of plant life to flourish.

A female markhor and her kid at the Stone Zoo, Stoneham, Massachusetts
Image credit: Sienna Weinstein

An Icon Under Threat

Despite their remarkable adaptations, cultural status, and ecological role, markhor still face mounting pressures in the wild. They’re currently listed as Near Threatened on the IUCN Red List, largely due to overhunting and poaching for their meat, skins, and striking corkscrew horns. But that’s only part of the story. Across their range, habitat is shrinking. It’s cut for fuel, carved up for livestock, and increasingly shared with domestic goats that compete for food and risk hybridization. These overlapping pressures have made it harder for wild populations to recover, even in places where protections are in place.

With focus and exposure dialed in, I pressed down the shutter button, grabbing just a few frames. The markhor stepped out of view again, just as they had a few moments ago. I kept looking anyway.

Sienna Weinstein is a wildlife photographer, zoologist, and lifelong advocate for the conservation of wildlife across the globe. She earned her B.S. in Zoology from the University of Vermont, followed by a M.S. degree in Environmental Studies with a concentration in Conservation Biology from Antioch University New England. While earning her Bachelor’s degree, Sienna participated in a study abroad program in South Africa and Eswatini (formerly Swaziland), taking part in fieldwork involving species abundance and diversity in the southern African ecosystem. She is also an official member of the Upsilon Tau chapter of the Beta Beta Beta National Biological Honor Society.

Deciding at the end of her academic career that she wanted to grow her natural creativity and hobby of photography into something more, Sienna dedicated herself to the field of wildlife conservation communication as a means to promote the conservation of wildlife. Her photography has been credited by organizations including The Nature Conservancy, Zoo New England, and the Smithsonian’s National Zoo and Conservation Biology Institute. She was also an invited reviewer of an elephant ethology lesson plan for Picture Perfect STEM Lessons (May 2017) by NSTA Press. Along with writing for Bio4Climate, she is also a volunteer writer for the New England Primate Conservancy. In her free time, she enjoys playing video games, watching wildlife documentaries, photographing nature and wildlife, and posting her work on her LinkedIn profile. She hopes to create a more professional portfolio in the near future.

Dig Deeper


Featured Creature: Giraffes

What animal, despite having the same number of vertebrae, has a neck longer than the average human, has spot patterns as unique between individuals as our fingerprints, and despite their gentle appearance, can kill lions with a karate-style kick!?

A tower of Reticulated giraffes (G. reticulata)
Image credit: Bird Explorers via iNaturalist (CC-BY-NC)

Some might say this is quite the… tall order for my very first Featured Creature profile! (Hold the applause!)

One of my earliest memories regarding these unique icons of the African savanna was when I was around five years old. My parents and I were visiting the Southwick Zoo in Mendon, Massachusetts, when we came upon the giraffe enclosure. One of these quiet, lanky creatures lowered its head across the fence bordering the enclosure, and licked my dad on the face with its looooong, black tongue! Once the laughter had died down, a flood of questions rushed into my head:

Why DOES the giraffe have such a long neck?

How do they sleep at night?

And what’s the deal with those black tongues?

A Tall-Walking, Awkwardly-Galloping African Animal

Their scattered range in sub-Saharan Africa extends from Chad in the north to South Africa in the south, and from Niger in the west to Somalia in the east. Within this range, giraffes typically live in savannahs and open woodlands, where their food sources include leaves, fruits, and flowers of woody plants. Giraffes primarily consume material of the acacia species, which they browse at heights most other ground-based herbivores can’t reach. Fully-grown giraffes stand at 14-19 feet (4.3-5.7 m) tall, with males taller than females. The average weight is 2,628 pounds (1,192 kg) for an adult male, while an adult female weighs on average 1,825 pounds (828 kg).

A giraffe’s front legs tend to be longer than the hind legs, and males have proportionally longer front legs than females. This trait gives them better support when swinging their necks during fights over females.

Giraffes have only two gaits: walking and galloping. When galloping, the hind legs move around the front legs before the latter move forward. The movements of the head and neck provide balance and control momentum while galloping. Despite their size, and their arguably cumbersome gallop, giraffes can reach a sprint speed of up to 37 miles per hour (60 km/h), and can sustain 31 miles per hour (50 km/h) for up to 1.2 miles (2 km).

Herd of giraffes running in Tanzania, Africa

When it’s not eating or galavanting across the savanna, a giraffe rests by lying with its body on top of its folded legs. When you’re 18 feet tall, some things are easier said than done. To lie down is something of a tedious balancing act. The giraffe first kneels on its front legs, then lowers the rest of its body. To get back up, it first gets on its front knees and positions its backside on top of its hind legs. Then, it pulls the backside upwards, and the front legs stand straight up again. At each stage, the individual swings its head for balance. To drink water from a low source such as a waterhole, a giraffe will either spread its front legs or bend its knees. Studies involving captive giraffes found they sleep intermittently up to 4.6 hours per day, and needing as little as 30 minutes a day in the wild. The studies also recorded that giraffes usually sleep lying down; however, “standing sleeps” have been recorded, particularly in older individuals.

Cameleopard

The term “cameleopard” is an archaic English portmanteau for the giraffe, which derives from “camel” and “leopard”, referring to its camel-like shape and leopard-like coloration. Giraffes are not closely related to either camels or leopards. Rather, they are just one of two members of the family Giraffidae, the other being the okapi. Giraffes are the tallest ruminants (cud-chewers) and are in the order Artiodactyla, or “even-toed ungulates”.

A giraffe’s coat contains cream or white-colored hair, covered in dark blotches or patches which can be brown, chestnut, orange, or nearly black. Scientists theorize the coat pattern serves as camouflage within the light and shade patterns of the savannah woodlands. And just like our fingerprints, every giraffe has a unique coat pattern!

The tongue is black and about 18 inches (45 cm) long, able to grasp foliage and delicately pick off leaves. Biologists thinks that the tongue’s coloration protects it against sunburn, given the large amount of time it spends in the fresh air, poking and prodding for something to eat. Acacia giraffes are known for having thorny branches, and the giraffe has a flexible, hairy upper lip to protect against the sharp prickles.

Both genders have prominent horn-like structures called ossicones, which can reach 5.3 inches (13.5 cm), and are used in male-to-male combat. These ossicones offer a reliable way to age and sex a giraffe: the ossicones of females and young are thin and display tufts of hair on top, whereas those of adult males tend to be bald and knobbed on top.

An elderly adult male Masai giraffe at the Franklin Park Zoo, Boston, Massachusetts
Image credit: Sienna Weinstein

There is still some debate over just why the giraffe evolved such a long neck. The possible theories include the “necks-for-sex” hypothesis, in which evolution of long necks was driven by competition among males, who duke it out in “necking” battles over females, versus the high nutritional needs for (pregnant and lactating) females. A 2024 study by Pennsylvania State University found that both were essentially acceptable! Check out the graphic below for a good visualization. 

A graphic summarizing the evolution of the giraffe’s body based on gender needs
Image credit: Penn State University, CC-BY-NC-ND 4.0

A Flagship AND Keystone Species

Alongside other noteworthy African savanna species, such as elephants and rhinoceroses, giraffes are considered a flagship species, well-known organisms that represent ecosystems, used to raise awareness and support for conservation, and helping to protect the habitats in which they’re found. As one of the many creatures that generate public interest and support for various conservation efforts in habitats around the world, giraffes have a significant role.

Giraffes, like elephants and rhinos, are also classified as a keystone species–one that plays a crucial role in maintaining the health and diversity of their native ecosystems, as their actions significantly impact the environment and other species. What is it that giraffes do that impacts their local ecosystems and environment? By browsing vegetation high up in the trees, they open up areas around the bases of trees to promote the growth of other plants, creating microhabitats for other species. In addition, through their dung and urine, they help distribute nutrients throughout their habitat. Some acacia seedlings don’t even sprout and grow until they’ve passed through a giraffe’s digestive system! By protecting giraffes, we also contribute to protecting other plant and animal species of the African savanna and open woodlands!

The Life We Share

The woodlands and grasslands where giraffes live are shaped in part by those long necks and unique feeding habits. As they browse high in the canopy, they open up space for other plants and animals to thrive. These ecosystems aren’t something we built, they’re something we’re lucky to witness. And if we have a role to play, maybe it’s simply to make sure our presence doesn’t undo the work that nature is already doing so well.

Sienna Weinstein is a wildlife photographer, zoologist, and lifelong advocate for the conservation of wildlife across the globe. She earned her B.S. in Zoology from the University of Vermont, followed by a M.S. degree in Environmental Studies with a concentration in Conservation Biology from Antioch University New England. While earning her Bachelor’s degree, Sienna participated in a study abroad program in South Africa and Eswatini (formerly Swaziland), taking part in fieldwork involving species abundance and diversity in the southern African ecosystem. She is also an official member of the Upsilon Tau chapter of the Beta Beta Beta National Biological Honor Society. 

Deciding at the end of her academic career that she wanted to grow her natural creativity and hobby of photography into something more, Sienna dedicated herself to the field of wildlife conservation communication as a means to promote the conservation of wildlife. Her photography has been credited by organizations including The Nature Conservancy, Zoo New England, and the Smithsonian’s National Zoo and Conservation Biology Institute. She was also an invited reviewer of an elephant ethology lesson plan for Picture Perfect STEM Lessons (May 2017) by NSTA Press. Along with writing for Bio4Climate, she is also a volunteer writer for the New England Primate Conservancy. In her free time, she enjoys playing video games, watching wildlife documentaries, photographing nature and wildlife, and posting her work on her LinkedIn profile. She hopes to create a more professional portfolio in the near future.

Dig Deeper


Featured Creature: Sloth

What creature used to live on the ground but now hangs in trees, has hair that grows in the opposite direction than most mammals, and turns green because of the algae that thrives in their fur?

The Sloth! (Folivora)

Hoffman’s Two-toed Sloth, Choloepus hoffmanni
(Image Credit: Andrae Scholz via iNaturalist (CC-BY-NC))

Would you be surprised if I told you that sloths aren’t lazy, but slow and careful? 

Sloths have been labeled as some of the laziest animals due to their slow movements and the (unfair and misguided) assumption that they sleep all day. This belief isn’t helped by the fact that the word sloth literally means “laziness,” as does its common name in many other languages. But as we’ll learn, there’s a lot more to this creature than meets the eye, and their chill, methodical nature is actually a quite ingenious survival mechanism. 

The six surviving species of sloths are categorized into two groups: Bradypus, the three-toed sloths, and Choloepus, the two-toed sloths. Even with this naming, all sloths have three toes on their back limbs – whereas two-toed sloths only have two digits on their front limbs. Both groups descend from ancestors that were mostly terrestrial (meaning they lived on the ground) that existed about 28 million years ago. Some of them reached sizes rivaling those of elephants! The sizes of modern sloths vary, with three-toed sloths typically ranging from 60-80 cm in length (24-31 inches) and weighing between 3.6-7.7 kg (8-17 lbs), while two-toed sloths can be slightly larger, particularly in weight.  

Found in the tropical rainforests of Central and South America, you can identify them by their rounded heads, tiny ears, and a facial structure that makes them look like they’re always smiling. They have stubby tails and long limbs ending in curved claws that, historically used for digging, now work with specialized tendons and a grip strength that is twice as strong as a humans to climb tree trunks and hang upside down from branches effortlessly. It is believed that over time, sloths evolved into a suspensory lifestyle to have easy access to plentiful food (mainly leaves), stay safe from predators (like jaguars and ocelots), and conserve energy.

Hoffman’s Two-toed Sloth, Choloepus hoffmanni
(Image Credit: Andrae Scholz via iNaturalist (CC-BY-NC))

Leafy Lunches

Sloths have a very low metabolism, meaning their bodies take quite a while to turn food into energy, thus the characteristically sluggish pace. Sloths move at about 4 yards per minute, and in an entire day, they may cover only around 120 feet, which is less than half the length of a football field. These languid movements are the reason why sloths can survive on a relatively low-energy diet, like leaves. While three-toed sloths are almost entirely herbivorous, two-toed sloths have an omnivorous diet that includes insects, fruits, and small lizards.

Even though leaves are the main food source for sloths, they provide very little nutrients and don’t digest easily. These lethargic tree-dwellers have large, slow-acting, multi-chambered stomachs that work for weeks to break down tough leaves. In fact, up to two thirds of a well-fed sloth’s body weight consists of the contents of its stomach. What other animals can digest in hours takes sloths days or weeks to process! Due to their slow digestion, sloths descend every week or so to defecate on the ground. Why exactly they do this is still a mystery to scientists, especially because sloths are at much more risk to predators on the ground.

Did you know that baby sloths learn what to eat by licking the lips of their mother?

Hoffman’s Two-toed Sloth, Choloepus hoffmanni
(Image Credit: Andrae Scholz via iNaturalist (CC-BY-NC))

Sloths, Moths, and Little Green Friends

Perhaps one of the most fascinating things about our slow-moving friends is what lives in their fur. Believe it or not, it’s a miniature world! Acting as a mobile home for a variety of different insect, fungi, and microbial species, sloths are, in fact, thriving ecosystems. But first, let’s set the scene.

Sloth fur grows in the opposite direction than it does on other animals. Normally, hair will grow towards the arms and legs, but because sloths spend so much of their lives upside down in the canopy with their limbs above their bodies (eating, sleeping, even giving birth hanging upside down), their fur grows away from their extremities and towards their bodies, giving them protection from the elements. 

The layered and grooved structure of sloths’ shaggy coat is the perfect environment to host many species of commensal beetles, mites, moths, fungi, as well as a symbiotic green algae. While the sloths don’t directly consume and gain nutrients from the algae (legend held for many years that sloths were so lazy, they’d rather eat the algae off their back than search for food), its presence helps protect the sloths from predators by aiding in their camouflage, hiding them from predators like harpy eagles.

Hoffman’s Two-toed Sloth, Choloepus hoffmanni
(Image Credit: Andrae Scholz via iNaturalist (CC-BY-NC))

A Slow but Important Presence in the Rainforest

Sloths are an integral part of tropical rainforest ecosystems. They regulate plant growth through their consumption of leaves, provide a unique habitat for smaller organisms like algae and moths in their fur, and contribute to nutrient cycling by depositing their feces on the forest floor, dispersing seeds and fertilizing new plant growth. 

Some species of sloths are at risk because of deforestation, contact with electrical lines, and poaching and animal trafficking. The health of these creatures is wholly dependent on the health of the tropical rainforest. If their habitat begins to deteriorate, sloths are forced to live elsewhere in places that cannot support healthy populations.

Luckily, The World Wildlife Fund (WWF) works with communities, governments, and organizations to encourage sustainable forestry, and collaborates to expand areas of forests under responsible management. WWF has worked with the Brazilian government since 2003 on the Amazon Region Protected Areas (ARPA) initiative, helping it become one of the largest conservation projects in the world. Not to mention, The Sloth Institute of Costa Rica is known for caring, rehabilitating, and releasing sloths back into the wild.

Northern Atlantic Forest Three-toed Sloth, Bradypus variegatus
(Image Credit: Kevin Araujo via iNaturalist (CC-BY-NC)) 

More than meets the eye

While sloths are well-known for their slow-moving pace and are labeled as lazy, to believe that that is the only notable thing about them is largely inaccurate. Similar to how judging a person based on one aspect of their personality is not an accurate judgment of their character, judging sloths based on their sluggishness is not an accurate judgment of sloths as creatures. It overlooks how they’ve adapted from life on the ground to life in the trees, how they use their muscles and long claws to hang upside down and save a ton of energy, their role as ecosystem engineers, how they create habitats for other organisms, and how they help maintain the health of the forest.

So the next time we come across a creature – whether in the wild or at a sanctuary – we might ask, “What else can this creature do?”

Abigail Gipson is an environmental advocate with a bachelor’s degree in humanitarian studies from Fordham University. Working to protect the natural world and its inhabitants, Abigail is specifically interested in environmental protection, ecosystem-based adaptation, and the intersection of climate change with human rights and animal welfare. She loves autumn, reading, and gardening.

Sources and Further Reading:

Featured Creature: Nilgai

Which creature is the largest Asian antelope, considered sacred to some and pest to others?

The Nilgai!

Photo by Hemant Goyal from Pexels

This fascinating four-legged friend could be described by a whole host of leading questions, depending on which notable features we want to emphasize. Elizabeth Cary Mungall’s Exotic Animal Field Guide introduced the nilgai with the question “What animal looks like the combination of a horse and a cow with the beard of a turkey and short devil’s horns?”

Personally, I find the nilgai much cuter than that combination might suggest, but it may all be in the eye of the beholder. The name ‘nilgai’ translates to ‘blue cow’, but the nilgai is really most closely related to other antelopes within the bovine family Bovidae. Mature males do indeed have a blue tint to their coat, while calves and mature females remain tawny brown in color.

Photo by Clicker Babu from Unsplash

As their physiology suggests, nilgai are browsers that roam in small herds, with a strong running and climbing ability. I encountered them in the biodiversity parks of New Delhi and Gurgaon, where efforts to rewild the landscape to its original dry deciduous forest make for ideal stomping grounds for the nilgai. 

Prolific Browsers

Indigenous to the Indian subcontinent, the nilgai is at home in savanna and thin woodland, and tends to avoid dense forest. Instead, they roam through open woods, where they have room to browse, feeding on grasses and trees alike. They’re considered mixed feeders for that reason, and will adjust their diet according to the landscape. Nilgai are adept eaters, standing on their hind legs to reach trees’ fruits and flowers and relying on their impressive stature (which ranges from 3 to 5 feet, or 1 to 1.5 m, at the shoulder) to get what they need.

Photo from Wikipedia
(By Akkida, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=34508948)

Like other large herbivores, nilgai play an important role in nutrient cycling and maintaining the ecosystems they’re a part of. In this case, that looks like feeding on shrubs and trees to keep woodlands relatively open, as well as dispersing seeds through their dung. One 1994 study noted the ecological value of the nilgai in ravines lining the Yamuna River, where the nitrogen contained in their fecal matter can make a large difference in soil quality, particularly in hot summer months. 

These creatures actually defecate strategically, creating dung piles that are thought to mark territory between dominant males. As a clever evasion tactic, these are often created at crossroads in paths through forest or savanna-scape, so that predators may not be able to trace the nilgai’s next steps so easily. 

Photo from Wikipedia (By Bernard Gagnon – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30634949)

Food webs for changing times

The natural predators of the nilgai once included the Bengal tiger and Asiatic lion, as well as leopards, Indian wolves, striped hyena, and dholes (or Indian wild dogs) which sometimes prey on juveniles. However, as deforestation, habitat loss and fragmentation, and development pressures change the face of the subcontinent, the ecological role of the nilgai has become more complicated. While their association with cows, a sacred animal in Hinduism, has widely prevented nilgai from being killed by humans, the relationship between people and nilgai is becoming more contentious. 

Where nilgai lack their traditional habitat to browse, they turn to plundering agricultural fields, frustrating the farmers who work so hard to cultivate these crops. Farmers in many Indian states thus consider them pests, and the state of Bihar has now classified them as ‘vermin’ and allowed them to be culled.  

Photo from Wikipedia (By Jon Connell – https://www.flickr.com/photos/ciamabue/4570527773/in/photostream/, CC BY 2.0)

There’s no place like… Texas?  

Strangely enough, when I got inspired by my nilgai sightings in India and decided to learn more about these Asian antelopes, one of the first search results I encountered involved nilgai populations here in the US. Specifically in Texas, an introduction of nilgai in the 1920 and 30s has spawned a population of feral roamers. Accounts say that nilgai were originally brought to the North King Ranch both for conservation and for exotic game hunting, somewhat distinct priorities that regardless led to the same result, a Texas population that now booms at over 30,000 individuals.

In this locale, nilgai largely graze grasses and crops, as well as scrub and oak forests. Here hunters have no qualms about killing them, but some animal rights groups object, and popular opinion remains divided on whether such treatment is cruelty or, well, fair game. 

These days, one concern is that a large nilgai population contributes to the spread of the cattle fever tick. Another concern remains about these grazers acting as ‘pests’ on agricultural land. 

Fundamentally there is a question that lies at the heart of the nilgai’s fate, both at home in India and Bangladesh, where natural predators and original habitat have steeply declined, and abroad, where they weren’t a part of the original ecosystem at all: what do you do when an animal’s ecological role is out of balance? 

In my view, there are no easy answers, but a familiar pattern we seem to uncover – that healthy ecosystems, where intact, harbor more complexity than we can recreate or give them credit for. Little by little, I hope we can support their conservation and resurgence. 

By Maya Dutta

Maya Dutta is an environmental advocate and ecosystem restorer working to spread understanding on the key role of biodiversity in shaping the climate and the water, carbon, nutrient and energy cycles we rely on. She is passionate about climate change adaptation and mitigation and the ways that community-led ecosystem restoration can fight global climate change while improving the livelihood and equity of human communities. She is the Assistant Director of Regenerative Projects at Bio4Climate.

Sources:
https://animalia.bio/nilgai
https://www.thedailybeast.com/nilgai-the-chimeric-beast-overrunning-texas-and-spreading-disease
https://en.wikipedia.org/wiki/Nilgai
https://www.britannica.com/animal/nilgai