Scavenger - Biodiversity for a Livable Climate

Featured Creature: Greenland Shark

What creature has a lifespan of over 250 years and catches prey by suction?

The Greenland Shark (Somniosus microcephalus) is one of the oldest and largest sharks in the world. It is the biggest of its superorder, Squalomorphii (one of the two groups of sharks). They can get up to 21 feet and 2,255 pounds, and have an average lifespan of 272 years. The oldest recorded Greenland Shark was almost 400 years old; that shark was alive during the Scientific Revolution! When I first came across these sharks and their longevity, I was fascinated. There are so many interesting things about this creature, so let’s take a look!

Amazing Adaptations

Unlike most other sharks, Greenland Sharks like cold, deep water, and are usually found near the Arctic or Atlantic Oceans. Greenland Sharks have special adaptations that help them thrive, and allow them to survive near-freezing water temperatures and high water pressure.

For one, they’re big animals, and larger animals tend to have slower metabolisms and therefore age slower. Their slow metabolisms also mean they move almost lethargically. This gives them part of their scientific name, Somniosus microcephalus; “Somniosus” comes from “somnum”, the latin word for sleep! That’s why they’re also called sleeper sharks.

If they’re so slow, how do they catch prey so fast? Greenland Sharks are known to eat seals, fish, and other fast aquatic animals, but they can only reach a maximum of around 1.6 miles per hour (one of the slowest animals of their size!). They primarily catch food by ambushing prey while they’re asleep, and by targeting injured animals. Since there’s little to no light at the depths these sharks are found at, and they’re usually dark colors, they can sneak up and surprise other creatures. They also have a special method of actually “grabbing” their targets. They open their mouths fast, creating a suction force that draws water (and the animal) into their large mouths, allowing them to swallow some prey whole.

Image: The open mouth of a dead Greenland Shark, showing off the teeth; Audun Eriksen (CC BY-NC 4.0 via iNaturalist)

Another example of Greenland Sharks’ adaptations to their environment is the fact that they have specific chemical compounds in their bodies that help them in different ways. The two common ones are urea and TMAO (trimethylamine N-oxide). Since these sharks are constantly surrounded by saltwater at high pressure, lots of urea in their body helps the shark’s cells keep their shape. This is why they’re classified as osmoconformers: they have high concentrations of urea in their body to match high concentrations of salt in the outside water, keeping a balance. Also, both urea and TMAO help the shark be less dense, allowing it to float better.

Urea does also have some negative side effects: too much of it can destabilize enzymes within the shark, hurting them and keeping proteins in their body from functioning correctly. TMAO counteracts this, stabilizing proteins even when there’s a lot of urea. This process allows Greenland Sharks to survive without trouble in the Arctic Ocean.

While these chemicals are helpful to sharks, they’re absolutely not for humans. TMAO in particular is extremely toxic to mammals, and can lead to extreme sickness or death. People do eat them, though! These sharks are a delicacy in some places: Hákarl, cubes of fermented Greenland Shark meat, is the national dish of Iceland. Because of the TMAO and urea, the meat has to be dried for weeks or months, and fermented in a certain way so it becomes safe for human consumption.

Image: Hákarl (fermented Greenland Shark meat, cubed); Wikimedia user Holapaco77 (CC BY 2.0 via Wikimedia)

Deep water usually doesn’t get much light, so these sharks adapted by also evolving other ways to “see”. They have an incredible sense of smell and rely heavily on it for navigation. They also have the ability to sense electric fields through special gel-filled pores all over their snout and face! This sixth sense lets them detect small movements and even heartbeats, allowing them to navigate both on a small scale (their immediate surroundings) and a large scale (Earth’s magnetic field).

In fact, their other senses are so well-developed that they don’t need sight at all. Many Greenland Sharks’ eyes become infected by a copepod called Ommatokoita elongata. This parasitic crustacean gets permanently attached to the corneas of the shark, injuring their eyes and sometimes rendering them completely blind (though the sharks don’t notice or care!). These creatures can sometimes have bioluminescence, making the shark look as if it has glowing eyes. It’s been theorized that, in the darkness of the water, this spot of light may help the shark attract prey.

Image: A Greenland Shark, eyes infected with *Ommatokoita elongata* parasites; Wikimedia user Hemming1952 (CC BY-SA 4.0 via Wikimedia)

Important interactions

Greenland Sharks have been around for a long time, and lots of different people have interacted with them in various ways. Because of their niche habitat range, accidental encounters are rare, and there haven’t been any recorded human attacks. These sharks aren’t aggressive (like most sharks, even though they get a bad reputation). Since they’ve been around for over a million years, different cultures have had different peaceful interactions with Greenland Sharks.

Sightings of these sharks may be behind the legends of the Loch Ness monster (although other creatures might contribute, too). There are also Inuit legends involving these sharks. Since they have such a high urea content, they smell like ammonia, or urine. One legend involves the sea goddess Sedna throwing a urine-soaked rag into the ocean, where it transformed into the first shark, a Greenland Shark. The nordic dish hákarl originally got so famous because when the meat isn’t fully fermented, it’s mostly non-toxic but has inebriating effects, which was thought to help people connect to and communicate with Sedna.

Image: A figurine of Sedna from the National Museum of Finland; Wikimedia user Sailko (CC BY 3.0 via Wikimedia)

These sharks have had plenty of negative interactions with people, too. They used to be purposely hunted for the production of certain oils. This doesn’t happen as much anymore, but they are still a frequent bycatch species. This means that they’re often accidentally captured or killed in the process of trying to catch some other animal. Modern fishing methods make bycatch more and more common, and this results in overhunting of many fish species around the world. Trawls are one of the most problematic examples of this.

A trawl net is a large, basket-like net that’s weighted to drag along the sea floor. Boats pull the nets along the ground at high speeds, and any animal in the way gets scooped up and trapped. This is terrible for sea life; imagine if you were a little sea creature at the bottom of the ocean, and out of nowhere an almost-invisible net grabs and traps you along with everyone else nearby. Entire populations of animals get captured in these nets, and most of them end up getting thrown away! Bottom feeders, or species that spend their time on the ocean floor (like Greenland Sharks), are typically deemed undesirable for selling. The targeted fish species only end up being a tiny fraction of the total catch, and the rest often gets discarded.

Image: Model representation of a trawl fishing technique; Andreas Praefcke (CC0 via Wikimedia)

Not only is this fishing method inefficient and wasteful, the nets damage homes of ocean animals by breaking or smashing everything in their path. Annually, around 3,500 Greenland Sharks are caught and killed as bycatch. Fishing methods like these have resulted in a decline in Greenland Shark populations, as well as many other aquatic animals.

Image: A mountain of dead dogfish being emptied from a trawl net; Wikimedia user Citron (CC0 via Wikimedia)

Other factors relate to the well-being of Greenland Sharks, and global warming is a big one. Since these sharks love cold water, they usually stay around the Arctic circle. Global warming is making this water a little warmer than it used to be, and a lot of the sea ice is melting.

Greenland Sharks have extremely long lifespans, but they also have low fertility rates and long gestation periods (how long it takes a baby to develop). Greenland Sharks have gestation periods of around 8 to 18 years. This means that it takes them a long time to replace population members. If too many die at once, baby sharks might not be born fast enough to save the population.

All of these factors influence the rarity and vulnerability of these sharks.

The IUCN Red List is a list that keeps track of vulnerable or endangered species. In 2020, Greenland Sharks got reclassified from near threatened to vulnerable. Unfortunately, since they have such a slow recovery time, their status will probably continue to get worse. This is bad news for a very strong reason: Greenland Sharks are incredibly important to their ecosystems.

As apex predators, they eat pretty much everything, including fishes and seals. They’re able to do this by ambushing prey, as described above. This helps them keep those populations in check by controlling how many of their prey species there are. If Greenland Sharks went extinct today, those other species would multiply. They would quickly take over ecosystems, destabilizing them, interrupting food chains, and overall harming everyone. Greenland Sharks prevent this by acting as a neutralizing force on population sizes of other fish. These sharks are important for maintaining balance in their environments.

Image: A Greenland Shark caught as trawl bycatch; Claude Nozères (CC BY-NC 4.0 via iNaturalist)

Greenland Sharks are scavengers; they eat carrion and other dead matter. They can eat large carcasses of animals that fall to the bottom of the oceans (like whales; have you ever heard of a whalefall?). Greenland Sharks actually have very unique, specialized teeth to let them do this; their upper teeth are small, thin, and pointy. Their lower teeth are chunkier with complex shapes that point away from the top teeth. This lets them tear off large chunks of meat when they roll their jaw. Teeth like this are another incredible example of Greenland Sharks’ specialized evolution! Eating already-dead animals lets them get energy and nutrients from other sources, “recycling” it and putting it back into the ecosystem.

Overall, Greenland Sharks are very important to their environments, and their removal would have disastrous effects on surrounding sea life.

Image: A dead Greenland Shark; Claude Nozères (CC BY-NC 4.0 via iNaturalist)

To me, these weird, fascinating sharks are incredible. They have strange and unique adaptations that help them survive their extreme environments, and they’re important to those environments because of their interactions with other species. Because of the specificity of their Arctic circle deepwater habitat, they’re relatively poorly studied. There isn’t that much recorded information on them; we still have a lot of unanswered questions. After learning more about them, I’m personally interested in how they’re able to survive for centuries (some genetic research implies it’s related to transposons, or “jumping genes” that can move around the chromosome!).

And while I tried, there’s also a lot about these sharks I didn’t mention. You can read more about their genetics here, about their longevity here, and about the harms of overfishing and trawling here.

Anya Reddy is a high school student at Blue Valley North. She loves biology and biochemistry, as well as entomology, ecology, and environmental science in general. Some of Anya’s non-science passions include archery and all kinds of 2D and 3D art. She enjoys learning about all kinds of organisms and how they connect and interact with others in their environment; she hopes to use writing to help share fascinating details about them, helping others like the weird and interesting organisms she loves.

Dig Deeper

Featured Creature: Bearded Vulture

What handsome creature dyes its feathers and almost exclusively eats bones?

The bearded vulture!

The bearded vulture (Gypaetus Barbatus) is a bird of prey known by many names including lammergeier, quebrantahuesos, boanbrüchl, and ossifrage.

The origin of these monikers come from the bird’s unique diet – bones. While most vultures pick off the meat on a carcass, the bearded vulture prefers to consume the skeleton itself. Over 80% of their diet consists solely of bones.

Weighing in at about 16 pounds and equipped with a wingspan of over 9 feet, bearded vultures are among the top ten largest birds of prey in the world. They use their substantial size to hoist the bone of their choice from the skeleton to the sky. They fly high enough to drop it onto a clifftop or boulder to break the bone into smaller, bite-sized pieces which they then swallow whole.

What makes these birds capable of digesting bone is the strength of their stomach acid. Bearded vultures have a stomach acid of nearly zero pH. This extreme acidity dissolves bone within 24 hours. To put this in perspective, humans have a stomach acid pH of about 2 while battery acid has a pH of about 0.8. Bearded vultures are the only carnivores capable of completely digesting bone.

Striking Appearance

Bearded vultures appear different from most other vultures due to the lack of a bald head. Most vultures are known for having no feathers around their head and neck which helps them remain clean when scavenging carrion. Bearded vultures, because of their chosen bone-based diet, do not need this adaptation, and sport a feathered head. Adults have white feathers along their body, chest, and face while their wings are dark brown. Black tufts protrude from their chin which gives them their modern namesake of bearded vulture.

Bearded vultures have large, glacier-white eyes that help them spot carcasses from the sky. As Old World vultures, their sense of smell is not advanced and they rely primarily on their eyesight when scavenging. When threatened or excited, the scleral ring around their eyes turns a bright red.

Bearded vultures have a unique propensity for the color red, so much so that they dye their white feathers a rusty vermilion. These birds will seek iron-oxide rich pools of muddy water or dust and bathe in it to color themselves a red-orange hue. Researchers are unsure of why they do this. Some posit that it is a sign of status – the redder the bird, the higher the seniority. Others believe the iron-oxide coloring helps prevent infections when breeding. Whatever the reason, bearded vultures paint themselves into a real-life phoenix.

Habitat and Ecological Role

Bearded vultures call the mountainous regions of Eurasia, East Africa, and parts of the Middle East their home. They prefer to live in areas that grant them the best visibility such as remote mountain ranges, steppes, canyons, and alpine valleys.

These birds tend to fly at high altitudes of about 6,500 feet above sea level. They utilize updrafts to ride the air currents which helps them conserve energy and glide for many miles.

In the early 1900s bearded vultures were hunted in Europe due to a false myth that they supposedly preyed upon children and livestock. The population in this area declined and is still recovering today. Currently, humans are the greatest threat to bearded vultures as habitat loss and poisoning endanger the remaining populations. The species is listed as near threatened by the IUCN.

Bearded vultures are an incredibly important species for the ecosystem because they act as nature’s garbage disposal. They help clean the environment of carcasses and diseases which keeps other species healthy.

Soaring away for now,
Joely

Joely Hart is a wildlife enthusiast writing to inspire curiosity about Earth’s creatures. She holds a Bachelor’s degree in creative writing from the University of Central Florida and has a special interest in obscure, lesser-known species.

Sources and Further Reading:
https://www.beardedvulture.ch/beardedvulture/biology
https://faunafocus.com/portfolio/bearded-vulture
https://safarisafricana.com/largest-birds-of-prey
https://factanimal.com/bearded-vulture/
https://digital.csic.es/bitstream/10261/64406/4/functilife.pdf
https://pubmed.ncbi.nlm.nih.gov/36596809

Featured Creature: Crow

Carrion crow (Corvus corone) black bird portrait of head and looking at camera. Wildlife in nature. Netherlands

What common bird possesses an uncommon intelligence, including diversified communication, excellent memory, and a talent for mathematics?

The crow!

Crows, members of the Corvus genus, stand out as some of the most intelligent and adaptable birds on the planet. These corvids include over 40 species, such as the American crow, hooded crow, and fish crow, and they inhabit diverse habitats ranging from dense forests to urban landscapes.

Known for their resourcefulness and problem-solving skills, crows have captivated scientists and observers alike with their remarkable behaviors. Crows continue to push the boundaries of how we understand animal intelligence, with recent studies on their tool use, awareness, and relationship to complex concepts gaining them well-deserved recognition and a place in the conservation conversation.

Crows are a fairly common sight in many parts of the world, with recognizable shiny black feathers and a familiar ‘caw.’ They are ground foragers with an incredibly diverse diet, ranging from insects and fruits to small animals and human food scraps. They tend to be associated with scavenging but are true omnivores, and can benefit soils and ecosystems by helping keep insect populations from surging out of balance. In urban settings, they are involved in flock feeding on human food scraps and garbage, and this adaptability to human environments means certain (though not all) species of crow maintain strong population numbers in the face of decreased access to natural habitat.

Communication and Complexity

While the crow ‘caw’ may seem like a simple call recognizable to many people, crow vocalization turns out to be quite differentiated. It has been discovered that among crows, groups form ‘dialects’ based on region. They also possess remarkable vocal mimicry skills, allowing them to imitate the sounds of other birds, animals, and even human speech. All of this allows the crow to engage in communication, social bonding, and strategic goals of deception and resource acquisition.

These crafty corvids possess a level of intelligence comparable to great apes and human children, allowing them to solve complex problems and even make and use tools. For instance, the New Caledonian crow, widely regarded as the most intelligent species among the corvid family, creates hooks and skewers from twigs to extract insects from crevices, showcasing their ingenuity. Researchers have studied crows’ usage of tools and observed that these birds will not only use pre-made tools or create simple combinations of tools in pursuit of their goal, but create multi-part composite tools, a behavior observed in only a few primates.

Famously, Aesop’s fables summarized long ago, “A thirsty crow wanted water from a pitcher, so he filled it with pebbles to raise the water level to drink.” Though the story is thousands of years old, these behaviors are still being studied and producing new insight today.

Image by Thanasis Papazacharias from Pixabay

Some of the most fascinating recent inquiries into crow intelligence have probed crows’ sense of self-awareness, long-term gratification, playfulness, and their understanding of complex concepts. As a math lover, one of my favorites among these is a unique phenomenon – conceptualization of ‘zero’. While many animals are able to perform basic counting, zero is generally a trickier beast, one that was absent from many ancient human civilizations’ numerical systems. However, crows are among the very few animals that grasp this number.

Additionally, crows exhibit impressive memory skills and can recognize individual human faces, reacting differently to perceived threats than to harmless humans. They are even known for ‘holding grudges,’ or conversely, remembering favorable relationships with people for years at a time. The ability to remember and share information within families and flocks may provide them with a significant evolutionary advantage in protecting themselves from harm.

Birds of a Feather Flock Together

In addition to their intelligence and adaptability, crows exhibit fascinating social behaviors. They often engage in cooperative mobbing to fend off predators, perform elaborate aerial displays to attract mates, and maintain strong family bonds by living in cooperative family groups. While adult crows primarily socialize just with their monogamous mate (with whom they pair for life), young crows stay with their parents for the first two years of life, and juvenile crows live in highly social ‘juvenile gangs.’ One theory into crow intelligence suggests that their ingenuity is due to the relatively long period of time young crows spend with their parents and the learning this enables.

Some crows, like American Crows, are also known to flock in large groups in winter months, both foraging for food and roosting together. These roosts can range from a few hundred to up to two million crows, with some roosts forming in the same general area for well over 100 years. Moreover, crows hold “funerals” for deceased members of their community, demonstrating a level of social complexity often overlooked among animals.

Crows will even form bonds with other animals. Crows in the wild have been observed playing with young wolves, and forming mutual attachments with these other social and intelligent creatures. Of course, there are many stories of the relationships humans have forged with individual crows, forming patterns of exchanging food for gifts or receiving trinkets after showing an injured bird care. One charming crow, Tuck, who has spent his life in a bird sanctuary in Tennessee, shares a moving friendship with his primary human caretaker, and has even become a conservation ambassador:

While many human cultures have depicted crows with respect for their ingenuity, recent trends have given crows a bad rap, primarily for the disturbance they cause to crops (hence the need for ‘scarecrows’). Despite their reputation as pests, though, crows play a crucial role in ecosystems as efficient garden helpers and natural pest controllers. They feast on insect pests like caterpillars and beetles, disperse seeds, and maintain a healthy balance in the garden ecosystem. Some crow species face significant challenges to their survival, such as habitat loss, disease, and predation, and crucial conservation efforts are underway to protect endangered species like the Hawaiian Crow through habitat restoration and captive breeding programs.

Crows have been both feared and revered by humans throughout history, often associated with death, darkness, and supernatural powers. The term “murder of crows” reflects their association with death and darkness in folklore, although alternative names like “horde” or “parliament” better capture their intelligent and social nature without perpetuating negative connotations. And many cultures and people have great respect for the clever crow, with whom we have coexisted for thousands of years. Despite their complex relationship with humans, crows continue to fascinate and inspire awe, challenging our limiting notions of animal behavior.

For a deeper dive into crows and the insights they share on animal intelligence, check out this fascinating video and the sources below:

May we continue to learn from our animal kin,

Maya

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. Having grown up in New York City and lived in cities all her life, Maya is interested in creating more natural infrastructure, biodiversity, and access to nature and ecological connection in urban areas.

Sources and Further Reading:
https://www.iflscience.com/crows-once-again-prove-their-intelligence-by-showing-that-they-understand-zero-60069
https://bigthink.com/neuropsych/crows-higher-intelligence/
https://arstechnica.com/science/2023/12/what-happens-in-a-crows-brain-when-it-uses-tools/
https://www.allaboutbirds.org/guide/American_Crow/overview
https://www.trvst.world/biodiversity/crow-facts/
https://www.audubon.org/news/10-fun-facts-about-american-crow
https://www.audubon.org/news/a-funeral-crows
https://www.npr.org/2020/10/23/927088859/crows-are-they-scary-or-just-super-smart

Creature: Scavenger