Tag Archives: Ravens

15,000 crows

I had imagined it like a beckoning flood.  A small sputter of water followed with increasing force until a great river finally makes its way.  Rather than water though, the flood I was trying to envision was the ascent of 12-15,000 crows to their nightly roost in Bothell, Washington.

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Witnessing it in person, I found that my water analogy was not entirely accurate.  Rather than being a steady stream with a predictable course, their arrival ebbed and flowed, sometimes leaving the sky lonely with only its fading grey light while other times exploding into seemingly endless black clouds.  They arrived from all cardinal directions, colliding into a mass that could be deafening at close range.  Although the movement of the flock as a whole was more restrained, individually they showed off with spontaneous dives and barrel-rolls.  Soon the light receded completely, and all I could sense was the cacophony of so many crows settling into the willow trees they would call their beds for the evening.

Time lapse of Bothell crow roost I took with my GoPro in December of 2016.  Music by Andy McKeen.

Since that first experience, I have visited the Bothell roost many times, each as awe inspiring as the time before.  This behavior isn’t unique to my region, however.  Cities and rural areas all over the world call themselves home to the upwards of thousands, even hundreds of thousands of crows that may seek their refuge when darkness falls.  Even in the greater Seattle area, Bothell is only one of two roughly equally sized roosts.  This kind of mass sleepover, known as communal roosting, isn’t unique to crows, but it certainly captures our attention in ways most other birds don’t.  So what exactly are the characteristics and functions of roosts?

For all species of corvid, roosts are places where anywhere from a small handful to hundreds of thousands of individuals may converge to spend the night together.  Though roosting occurs year round, it peaks in winter, when territorial pairs are free from the eggs or nestlings that demand all-night attention.  They may occur in wildlands, but more typically occur in cities, where sequestration of heat is higher than in surrounding areas.  Here in Bothell, the roost converges in a wetland outside of the University of Washington’s Bothell campus, but in other areas they may take over the rafters of abandoned buildings or trees dotted within a business district.

Historically Danville, IL hosted North America’s largest roost, a whopping 325,000 birds but I do not know if they remain the contemporary record holder.  The midwest is particularly primed to host such large numbers because many thousands of crows head there during winter from their too cold territories in Canada and because appropriate roosting locations are few and far between.

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Prior, or just after roosting crows attend “staging” or “pre/post-roost” areas where they gather in the trees or on the ground by the hundreds or thousands.  Since these staging areas often occur on asphalt or turf where there’s little food or water, their function continues to elude scientists though social or anti-predator implications seem likely.1 A new UW research study is attempting to parse why crows are so vocal during the staging period and what they might be trying to communicate.  Perhaps their findings will shed some much needed light on these events. 

Corvids get different things out of roost itself depending on the species or possibly even the region they live.  For example, for ravens roosts act, in part, as mobile information centers.2  A raven knowledgeable of a food bonanza such as a moose carcass will display to other ravens at first light, and recruit others to the food.  Rather than being a sign of food altruism, this kind of recruitment is often the only way a lone raven can gain access to a large carcass.  Finding and gaining access to an animal carcass is challenging both because its arrival is unpredictable but also because it’s intensely guarded by the pair whose territory happened to claim the animal’s life.  Overpowering a pair takes a small army, so by recruiting other birds, rather than giving up food in the name of helping others, the lone raven actually gains access to a resource it would have otherwise been boxed out of.

American crows on the other hand do not have this need because urban waste and invertebrate filled yards are so easy to come by.  For crows, roosts act in large part as predator protection.  The odds of successfully fleeing an incoming owl are much better when there are thousands of you, rather than just you and your mate.  They may serve other purposes as well though including socialization, mate finding, and thermoregulation.  Lastly, while there isn’t strong evidence of information sharing among crows it would be arrogant to claim we know it doesn’t occur.

How roosts are organized remains largely mysterious.  For example some evidence shows that ravens that come from the same food bonanzas also sleep near each other in a roost,2 whereas other work done on crows suggested that group cohesion is low at roosts.3  Still, other research suggests that while group cohesion from the territory is low,  it’s high leaving the staging area.  So perhaps there is deep rhyme and reason for who they sleep with, it just hasn’t been captured by the questions we’ve so far asked.  One thing is for certain though; the one place you don’t want to be is low in the trees with others above you.  There would be no escaping the white shower raining down throughout the night.

Even the people who share the UW’s campus are sensitive to this reality.  In perfect synchrony with the incoming cloud of birds, the umbrellas bloom like moonflowers.  Here in Seattle, people seem willing to take such measures to coexist with the birds (though I’m sure there are many who only do so only by rule of law).  In other areas though the cultural attitude or resulting damage makes such cohabitation difficult, even deadly.  In the most extreme case, 328,000 crows were killed in 1940 when the city of Rockford, IL elected to dispose of a local roost with dynamite.4  Today, crows are protected under the migratory bird treaty act and cities are usually required to take more creative, non-lethal approaches including noise and light deterrents.

City living doesn’t always lend itself to witnessing the kind of mass animal movements we fawn over when they appear in Planet Earth footage, but that doesn’t mean they are devoid of such spectacles.  The mass micro-migration of thousands of crows is an awe inspiring event,  grand in both scale and the mysteries it contains.  Any corvid or birdwatcher would be remiss to ignore such an opportunity and I encourage everyone to get outside, head to your roost, and watch the magic unfold.

Literature cited

  1. Moore JE, and Switzer PV. (1998).  Preroost aggregations in the American crow, corvus brachyrhyncos.  Canadian Journal or Zoology.  76: 508-512.
  2. Wright J, Stone RE, and Brown N. (2003).  Communal roosts as structured information centers in the raven, Corvus corax. Animal Ecology 72: 1003-1014.  DOI: 10.1046/j.1365-2656.2003.00771.x
  3. Donald F. Caccamise, Lisa M. Reed, Jerzy Romanowski and Philip C. Stouffer
    (1997). Roosting Behavior and Group Territoriality in American Crows. The Auk 114: 628-637
  4. Marzluff, J.M. and Angel, T. 2005. In the company of crows and ravens.  Yale University Press

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Filed under Birding, Crow behavior, crow conflicts, Crow curiosities, Crow life history, Crows and humans

Why the crow smiles

There’s hardly a corvid species that doesn’t strike me as beautiful but there’s only one that’s always struck me as particularly gleeful.  Looking at the New Caledonian crow it’s evident there’s something different about the shape and proportions of its bill. It’s a bit shorter and more blunt, and it lacks the obvious downward curve of a typical crow bill, with lower mandible actually curving slightly up. Put together, these features appear to give it the perpetual grin that trademarks this species.  I’ve joked that this must be because they’re always feeling very pleased with themselves for being so smart, and thanks to new research, I’ve come to learn my joke had it backwards.

By using tomography scans, Hiroshi Matsui and his team were able to compare the shape and structure of the NC crow’s bill with that of its close relatives. Their conclusion, which they report in the March issue of Scientific Reports, is that this shape makes the handling and manufacturing of tools easier. Looking at photos of the birds in action, it feels intuitive that the more exaggerated curve of a raven or American crow bill would have a hard time achieving the dexterity that NC crows need to use their stick and hook tools.

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Given this new research it’s time to amend my joke. It’s not that NC crows grin because they’re smart, they’re smart because they grin.

Literature cited

  1.  Matsui, H., Hunt, G., Oberhofer, K., Ogihara, N., McGowen, K., Mithraratne, K., Yamasaki, T., Grey, R., and Izawa, E. 2016.  Adaptive bill morphology for enhanced tool manipulation in New Caledonian crows.  Scientific Reports 6. doi:10.1038/srep22776

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Filed under Crow behavior, crow intelligence, Crow life history, New Research

I spy with my raven eye…

…someone trying to steal my lunch.  Turns out, humans are not the only ones wary of peeping Toms; new research shows raven can imagine being spied on by a competitor.

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The other day my friend and I were having a very merry time at the thrift store when, without cause or provocation, this women decides to up and ruin our trip.  Well really, she simply spotted the same gorgeous caste iron dutch oven that my friend wanted and reached it first, but the consequence was the same (it was a tragically beautiful dutch oven). This dynamic-my friend having her own intentions (to obtain and own that dutch oven for herself) and recognizing that this other women had her own intentions (to obtain and own that dutch oven for herself) is something so second nature to being human we rarely give it any thought.  But the ability to attribute mental states to those around us is an incredibly profound and complex cognitive task.  Understanding if this ability, called Theory of Mind, exists in other animals has been among our top interest as ethologists.

Like other corvids, ravens cache food and, as a consequence, run the risk of their caches being stolen by others.  It has long been known that if ravens can see that they are being watched, they behave differently when it comes to caching than if they are alone.  This is interesting, but doesn’t necessarily speak to whether they posses theory of mind because of the confounding effect of “gaze cues”.   Basically, the correlation between head cues and competitor behavior make skeptics doubtful about non-human animals having the ability to know what others might be seeing.  So raven master Thomas Bugnyar and his colleagues Reber & Bruckner recently published an elegant study to address just this issue.

By training captive ravens to look through a peephole, and then allowing them to cache food with the peephole opened or closed, the researchers were able to show that ravens behaved as if they were being watched when they could hear ravens and the hole was open, but not when they could hear ravens but the peephole was closed.  What this suggests is that ravens are capable of remembering their own experience of looking through a peephole to see into another room, and can imagine that another bird might be doing the same thing even if they cannot see this bird.

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Experimental set up.  Bugnyar et al. 2016.  Nature Communications

Theory of mind and imagination (which are not mutually exclusive) are the cornerstones of what makes for a powerful cognitive toolkit and have long been thought to be uniquely human.  As we continue to build on the body of work showing non-human primates, corvids and some other animals posses some of the same skills we do, many will be challenged to redefine what it means to be human.  Personally, framing the question that way doesn’t interest me.  To me the more interesting question is not how are humans different from ravens, but how are we the same and why? What is it about being human and being raven that make possessing imagination important?  Fortunately there is still loads more research to be done, and when it comes to teasing out this question I can only imagine the possibilities.

Literature cited:

Bugnyar, T., Reber, S.A., and Buckner, C.  (2016) Ravens attribute visual access to unseen competitors.  Nature Communications 7.  doi:10.1038/ncomms10506

 

 

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Filed under Crow behavior, crow intelligence, New Research, Raven behavior, Raven intelligence

Why the crow is black and other mythology

Since humans began telling stories and writing them down, they’ve told stories about crows and other corvids.  This should come as no surprise considering corvids are found in nearly every corner of the world and are as connected to us now as they were centennials ago.  Whether they are sharing (or thieving) the food we grow, consuming the soft tissues of our dead, or delighting us with their company, corvids have infiltrated the most intimate parts of our lives. They walk the earth cloaked in black, and yet persist with the light of life even we perish through disease or famine.  It is this juxtaposition that I think made our human ancestors look upon those glossy feather and conclude they must have some greater tie to creation than their other avian kin.  Be it India, Rome, the Middle East or the New World, they’ve been written into the oldest stories explaining how the facts of the world came to fruition.  With that in mind, let’s break from answering questions with the rigors of science this week and embrace the explanations offered by our ancestors.

Photo: American Museum of Natural History

Photo: American Museum of Natural History


Why the crow is black (According the the Greeks/Romans)

Apollo, the son of the most powerful greek God Zeus, had an important, albeit tumultuous relationship with crows.  The greek word for crow, corone, comes from the name of Apollo’s mistress, Coronis.  According to the version of this story told by Appolodorus, although Coronis and Apollo had been lovers, she left him to marry a mortal, Ischys.  The crow, then white, brought news of the marriage to Apollo who became so incensed he burned the bird’s feathers and then burned Coronis to death.  In other versions Coronis is herself turned into the black crow and it’s possible the Greeks saw a mated pair of crows as a representation of the forbidden love between Coronis and Ischys.   This may be one of the earliest stories of a woman marrying below her class for love.

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Why the crow is black (According to Muslims)

Muhammad, born sometime around 570 CE, is considered to be the founder of Islam and the last profit sent to earth by God, according to the Islamic faith.   A popular legend depicts a time Muhammed was hiding from his enemies in a cave.  A crow, then white, spotted him and cried “Ghar, Ghar!” (cave, cave!) to his seekers.  They did not comprehend the crow’s cries, however, and Muhammad escaped.  He turned the crow black for the betrayal and cursed him to only utter one phrase for the rest of time;  “Ghar, Ghar!”


Why the crow is hoarse (According to Greek/Romans).  

Apollo sent a raven to gather water for a feast but the raven was distracted by an unripened fig tree.  Determined to obtain the figs, the raven waited until the tree ripened, ate his fill, and then captured a watersnake to bring back to Apollo.  The watersnake, the raven explained, was the reason he was late and unable to collect the requested water, but Apollo saw through the lie.  As punishment, Apollo declared the raven could never again drink from the stream until the figs ripened.  Since the raven must now wait, his voice is hoarse from thirst.


Why owls and crows fight  (According to Hindus)

According to the great animal epic, the Panchatantra, the birds had come together to elect a king and choose his earthly appearance.  They had elected the owl and were beginning to organize his lavish coronation, when the crow arrived.  The crow laughed at their decision, protesting that the owl was too ugly, his features without tenderness, and his nature without pity.  Furthermore, Garuda, the eagle mounted Vishnu was already their king and to take another was a sin that could result in severe punishment by the Gods.  The others, scared by the crow’s warning left in agreement.  Being nocturnal, the owl had slept through all this but now awoke to find his coronation canceled due to the crow’s persuasive words.  They have fought ever since.

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Why we die (According to the Haida Natives)  

Ravens have a significant role in the creations legends of many different Native American tribes.  According to the Haida tribe of the Queen Charlotte Islands, Greater Raven was the creator that first called earth into being on the endless sea.  He then made humans out of both rock and leaf.  The people of rock were (as I can well imagine) more difficult to shape and were never finished.  The people of leaf, on the other hand, were quickly completed and ready to roam the land.  The raven instructed them that, like the leaf, they must eventually fall and rot back into the earth and thus death entered the world.

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Why the sky is full of light (According to the Tsimshian Natives)

Greater Raven, as mentioned above, eventually gave dominion of the world to his sister’s son, Lesser Raven, who it was said was as robust as stone and would live forever.  Unlike Greater Raven, Lesser Raven was both a trickster and had a voracious appetite.  To satisfy his hunger, Lesser Raven filled the earth with food, but feared he would be unable to find it, as at that time the earth was still dark.  Seeking a solution, Raven flew through a hole in the sky where he found another world much like our own.  When he saw the daughter of the Chief of Heaven collecting water he transformed into a needle and floated into her vessel.  When she drank the water and the needle, Lesser Raven impregnated her and was later reborn as her son.  The infant charmed the Chief and his wife and was granted permission to play with the box containing the light of day.  Suddenly, Raven took his original form and flew back to earth through the hole in the sky, taking the box with him.  Later, he broke the box out of anger and filled the sky with the sun, moon and stars.

Map showing tribal delineations for NW coastal tribes including the Haida and the Tsimshian

Map showing tribal delineations for NW coastal tribes including the Haida and the Tsimshian

 

Why we bury our dead (According to Judaism)

According to the Yalkut Shimoni, an aggadic compilation of the Hebrew bible written in the 13th century, after Adam and Eve’s son Abel died, they did not know what to do with the body.  Seeing their distress, a raven killed one of his companions to show the grieving couple how to dig a hole and bury the body. To thank the raven for his kindness, God feeds baby ravens until their feathers turn black after which their parents take over.

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Thus, be it the color of ravens or the intimate mysteries of human death, crows have offered a canvas on which early peoples the world over painted their explanations of life.   My thanks to Borgia Sax and his terrific book, Crow, which was the factual source and inspiration for this post.

 

 

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Filed under Corvid mythology, Crows and humans

Yellowstone field experience

Last week I had the great pleasure of spending a week in Yellowstone National Park with both corvid expert, John Marzluff and predator-prey dynamic expert, Aaron Wirsing.  In addition to spending an entire week with these two, I also had meetings and saw presentations from folks like the golden eagle team of Al Harmata and Marco Restani, the head researcher of the wolf project, Doug Smith, Bison expert Rick Wallen, and wolf and cougar kill expert Dan Stahler.  It was an amazing week of breath taking wildlife and in depth expertise on what’s going on in the park.  This week, I thought it would fun to take a little break from corvids and just share some of the photos I took along with the stories and biological details that go with them.

Birds
Ungulates
Predators
Miscellaneous

Birds

To kick the trip off we headed outside of Bozeman, Montana to meet up with eagle researchers Dr. Al Harmata and Dr. Marco Restani.  They’ve been doing research on eagles for more than 30 years and know more about these birds than maybe anybody.  Right now, they’re conducting an ongoing study to look at the effects of lead poisoning on  eagles.  Although lead shots have been banned in waterfowl hunting and in some states like California, in most other places lead bullets are still used for other kinds of game.  The lead fragments end up in the gut piles hunters leave behind, or in the prairie dogs or other carnivores that their shooters had no intention of taking home.  Eagles scavenge these remains and can wind up with deadly levels of lead in their bloodstreams.  Elimination of lead from bullets will likely be a necessary step to protect eagles, though I expect a robust fight from the NRA and some hunting communities.

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For corvids, spring time means nesting time and the magpies were busy at work.  Unlike crows and ravens which build more traditional looking nests, magpies make nests with roofs, further protecting them from predators.  If that’s not cool enough, magpies are known to build several of these dome nests and have been observed moving both eggs and chicks between them.

The magpie's nest is the big clump in the middle of the tree

The magpie’s nest is the big clump in the middle of the tree

A bill-load of mud to finish off lining the nest

A bill-load of mud to finish off lining the nest

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Seeing peregrine falcons perched along the 520 bridge on my way to school is always a treat, but there’s something about seeing them in this setting that’s all the more spectacular.

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At lunch time we were greeted by John’s special raven friend, Big Guy, which has been visiting him in the park for the last 15 years.  He and his mate were also busy nest building though we were unable to locate it.

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Mountain bluebirds were such a spectacular addition of color to the park, and I was super lucky to be in the right place at the right time to snap this photo.

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Ungulates

When we first arrived to the park, we were surprised to be greeted by pronghorn.  John has been leading classes to Yellowstone for 15 years and had never seen them as far into the park as we did.  Pronghorn aren’t adapted to run very well in deep snow, so they generally avoid the higher elevations in the park until later in the year. The snow melt came incredibly early this year, however, allowing them to penetrate further into the interior of the park than usual.  While the level of early snow melt we experienced isn’t unheard of, it was unusual and fit the models that predict increased drought in this area as a result of climate change.

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Bighorn sheep were prolific across the park.  In the winter and spring, male bighorns form large groups while the ewes and lambs heard up to do their own thing. I never got tired of seeing those big curls!

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Bison are truly the iconic ungulate in the park.  Theirs is a story of an amazing comeback, and one that’s really not so different from wolves.  As of 1902 there remained only 23 bison left in the park, and but thanks to ranchers and the US Army administrators of YNP, new animals were brought in and over the next 50 years that small population grew to over a 1000 animals.  Now, the park supports about 4000 animals, and is considered the only place in the country that has both maintained bison since prehistoric times, and supports non-cattle hybridized bison.

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Right now, bison regulation within the park is subject to much debate due to the presence of brucellosis.  Brucellosis is a bacterial infection that was brought when settlers first introduced cattle to the west.  It results in the abortion of calves in animals like bison, elk and livestock.  It’s transmitted by contact with an infected mucous membrane, which generally happens when curious animals touch and smell the aborted calves.  Although it’s not fatal to the mothers, the aborting of calves represents a potential economic threat to ranchers.  Although elk are also important vectors of this disease, a rancher we spoke with echoed the opinion of the ranching community at large in saying that bison are the main problems and their departure from the park needs to be controlled.  As of 2002, the Sate and Federal government developed an inter-agency management plan to control bison and the spread of the disease, which basically means that many (think in the thousands) of animals are killed once they cross the boarder.  Lead park bison biologist Rick Wallen described to us the controversial nature of this tactic which results in, one the one hand, folks from the ranching community saying there isn’t enough being done, while on the other, members of the public decrying the park for killing such an iconic species.  Despite these culls, however, the park maintains a stable population of bison, which other than run-ins with lakes and geothermal features, are basically free from predation apart from one particular wolf pack which occasionally manages to take one down.

One of my colleagues illustrating the difference between cow (left) and bull (right) bison horns.  She also sports a radio transmitter used to track an individual bison across the park.

One of my colleagues illustrating the difference between cow (left) and bull (right) bison horns. She also sports a radio transmitter used to track an individual bison across the park.

A couple of bison playfully testing each other

A couple of bison playfully testing each other

One of the most interesting insights from Rick was the observation that bison both engage in what looks like altruistic behavior, like the time he witnessed a heard protect an injured female from wolves, to completely brutal behavior like the scene my classmates and I had the serendipitous opportunity to witness.

We happened upon this scene when checking the area for signs of a bear we had heard was scavenging some bison carcasses. Although we didn’t see the bear, we quickly noticed that there was a bison calf trapped in the water, and not too far from drowning by the sounds of its breathing. The banks of these lakes are incredibly slick, and it can be impossible for an animal to get out. We watched with bated breath, conflicted between rooting for the bison to make its escape and for it to drown, as that would mean an almost guaranteed bear and wolf sightings the following days. Finally after about 10 minutes the calf managed to pull itself from the water. While all this was going on, its heard had been nearby and quickly after the calf escaped began to approach it. We were all expecting a Disney style reunion but to our shock the entire heard proceeded to haze the calf! They pushed it about 100 m down the valley before finally relaxing their assault and letting the calf rest and start to graze. Since we didn’t see bears the next day, our best guess is the calf managed to regain its strength and make it through the night.

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A tree shows some ears after being used as a scratching post for a bison.

A tree shows some wear after being used as a scratching post for a bison.

Although much of our time in the park was dedicated to simply looking for, and observing wildlife, we also collected a couple of different kinds of data while we were there.  For the last 7 years this class has been conducting “elk follows” which means that we select an individual elk in the different parts of the park and record its activities for 15 min.  Later, we will use this data and match it up with data from the Wolf Project to ask questions about elk behavior, condition, and spatial use in light of the presence of wolves.  This big bull was taking a little rest and is a great illustration of the hardship of winter.  You can clearly see the low fat reserves on its rump, as evidenced by the outline of its spine and pelvic bones.

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This bull is a good example of one that’s already lost its antlers, and it’s probably feeling a little lighter than its 5-point companion, since elk antlers can weigh up to 40lbs!  Antlers are the fastest growing tissue and in the height of spring and early summer they can grow up to an inch a day.  One of our faculty members, Aaron Wiring, told us an incredible story of seeing a big 6 point bull being chased by wolves in an earlier trip, only to loose one antler during the chase. A little lopsided, the bull managed to fend them off until it was finally cornered against a tree when, you guessed it, the second antler fell off.  It was all over soon after that. Talk about bad timing!

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Predators

A coyote makes off with the leftovers of a bison carcass.  Coyotes are often killed by wolves, and they need to be extra mindful when in open spaces near kills sites like this.  Why wolves are so predatory towards coyotes and not foxes is something of a mystery.

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One of my favorite experiences while in the park was seeing the wolves.  There’s just something about seeing such an iconic animal that lifts your spirit.  The reintroduction of wolves was, and still is, incredibly controversial.  There’s no doubt that their presence on the landscape is a threat to ranchers and pet owners alike, but I was inspired by our talk with Hannibal, a rancher who lives adjacent to the park boundary.  Despite loosing three dogs and many sheep and calves to wolves, he maintains his position that they are a necessary part of the Western landscape and deserve a place along side he and his family.  After his daughter, Hilary Zaranek, started range riding (rounding up and sleeping with the heard at night) predation by wolves dropped to nearly zero and their three current dogs seemed very happy to me.  By shifting the ranching paradigm to one where multiple ranchers join herds and share space, range riders become a sustainable and economical option for ranchers.  Hannibal and Hilary are the forefront of this shift and their dedication to the presence of wolves was awe inspiring.

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While we were in the park we were privy to some pretty special changes going on within the packs. Inside the park, wolves are killed almost exclusively by other wolves.   Recently, the alpha male of the Lamar Valley pack was killed by members of the competing Prospect pack after he confronted them.  His death put the alpha female in an incredibly precarious position since she will be unable to hunt after she gives birth to her dead mate’s pups and in a few weeks.  Although her 6 current pups are nearly a year old they are still too young to provide for her during this time.  As a result, she is attempting to court 4 of the male members of the Prospect pack in an effort to gain a new alpha male that will help raise her pups.  Unlike lions which will kill the cubs of a competing male, wolves will help raise the former dad’s pups after they take over.  Some readers may even be familiar with the famous story of 8, the hero ‘little wolf” who did just this.  While we were in the park the female appeared to be courting a spectacular grey male, but shorty before we left we learned that he fell out of contention.  Who the next alpha male is is up to the alpha female, and only time will tell who she chooses.

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The effects of wolves in the park have been profound and their necessity to maintain a balanced and healthy ecosystem is unquestionable.  For more information on the wolves’ effects on the Yellowstone ecosystem check out this Ted talk.

One of the most interesting things we did was meet up with wolf expert Dr. Dan Stahler.  He and fellow carcass expert, Kai, lead us to a recent cougar kill and described how to identify kills as either wolf or cougar and showed us the kinds of data they collect off such kills.  Key signs off cougar kills are puncture marks around the throat, neat, cleanly picked bones, and characteristic caching (or covering and hiding) of the carcass.  Wolf kills, on the other hand, are not hidden, show signs of hemorrhaging around the animal’s back legs, and the carcasses are found dismembered.  This particular cow elk was killed and partially eaten by a cougar before being discovered by wolves and other scavengers.

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Miscellaneous

A badger skull found while hiking the bighorn lambing grounds on the edge of the park boundary.

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On our last day I spotted a couple of yellow-bellied marmots, marking the fist time John has seen them inside the park during this trip.  I’ve never gotten such a good look at these little animals and I must say they’re very pretty!

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Antler drops are an important source of calcium for many animals in the park, and this particular one shows its age with a beautiful patina of lichen.

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A bison carcass lays peacefully in its resting place of Lamar Valley.

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Filed under Being a scientist, Birding, Field work

The politics of ravens

With the (insert relevant election cycle) coming up, a 2014 publication from Massen et al. reminds us that we are not alone in our affection/affliction for political scheming. No, ravens don’t hold elections or engage in thinly veiled attempts at voter suppression, but they do build relationships and attempt to thwart the alliances of others.   Massen’s team observed the interactions of hundreds of individually marked birds and categorized their relationships as either (1) breeding pair with territory, (2) strongly bonded w/o territory, (3) loosely bonded w/o territory or (4) nonbonded.   Ravens build bonds by participating in affiliative behavior such as allopreening (mutual grooming), and interrupting these interactions can be risky if the pair fight back. Over six months they recorded affiliative interactions and found that 18.8% were

Photo credit: Jorg Massen

Photo credit: Jorg Massen

interrupted by a third bird, giving rise to their curiosity over the function of these interventions.  Given that ravens have been previously shown to track the dominance relationships of others, they wanted to know if there was a relationship between bonding status and the likelihood of being an intervener or being intervened.  In both cases they found that there was a significant relationship between the two.  Birds who were either a pair or at least strongly bonded were most likely to intervene, and those attempting to forge loose bonds were the most likely to be interrupted.  The researchers interpreted these results to show that strongly allied birds attempt to preclude the threat of competition by squashing the alliances of future coalitions.  Importantly, they were less likely to bother with nonbonded birds since, for now, their social ties are too weak to become threatening.  Conversely, they also stayed out of the interactions of other pair or strongly bonded birds since these interventions pose a greater physical risk to the third wheel.

These results are quite intriguing but there’s still a lot to vet and better understand before they will be widely accepted.  Critically, there is no immediate benefit to the intervener.   Embracing the results of this study requires accepting the idea that an animal, especially a bird, is capable of putting future rewards ahead of current risk or losses.  Loose bonds are too weak to act as a competitive threat, so this effort on behalf of the intervener is only useful if you assume that those loose bonds will become a threat if allowed to flourish and become stronger over the course of days, weeks or months. Risking a fight now to thwart a relationship that only may be problematic next month is a big temporal leap.  As humans, this kind of future planning is an ability we take for granted but it’s quite a cognitive feat.  Although the scales are beginning to shift, I imagine we have many more studies to go before results like this are considered representative of the temporal flexibility of ravens and other corvids.

  1. Jorg J.M. Massen, Georgine Szipl, Michela Spreafico, Thomas Bugnyar. Ravens Intervene in Others’ Bonding Attempts. Current Biology, 2014; DOI: 10.1016/j.cub.2014.09.073

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Filed under New Research, Raven behavior, Raven intelligence