Tales from the Trail Cam

At Wolf Ridge, we have a trail-cam, a small camera we can stick in the woods that records photos when motion is detected. A couple weeks ago, it was placed in front of a deer carcass that had been taken in from a nearby road, and we ended up with some pretty incredible photographs.

It's not uncommon to see ravens and bald eagles feeding alongside each other - both are opportunistic scavengers. However, I still found this to be a bit surprising, given my recent knowledge about how ravens will mob predators hanging out near their nests.

Bernd Heinrich also found this to be curious and in Mind of the Raven, he describes how he introduced various non-ravens into the enclosure where he kept four ravens and observed their reactions. For example, when he put a chicken inside, the ravens harassed it at first, pulling at its tail, but quickly lost interest and ended up ignoring the chicken. In contrast, when he put a large, proud rooster inside, the ravens did not torment the bird whatsoever, leading Heinrich to wonder whether they'd already learned to generalize all "chicken-like" creatures or if they were intimidated by the dominant demeanor of the rooster. Heinrich continued to experiment, with a turkey, a dog, etc., ultimately concluding that ravens always attempt to get to know a novel predator in their feeding environment and then engage in one of two reactions: ignoring it or trying to kill it.

In general, ravens seem willing to tolerate dangerous predators if there is food to be had nearby - ravens have been observed feeding beside coyotes in Yellowstone National Park. Sometimes, they even get brave enough to try to dominate a feeding site, or steal food from a larger predator. In this PBS video, a raven pulls at an eagle's tail; the eagle could do some serious damage to the raven with its talons, but they are currently in use holding onto some meat. Eventually, the eagle gives up and lets go, giving the raven its chance to sneak in and grab a snack.

Sometimes, ravens will mess with eagles, seemingly just for the sake of messing around.

Here are some more awesome trail cam photos:

Bloody Beak.

Defensive posture.

"Back off!!"

An immature bald eagle.

Four at once - bald eagle party!

Suddenly...a bobcat appears!

Bobcat checking out the camera.

And a fox.

I Saw a Mobbing in Canada

Last weekend, Jill, Sara, and I took a mini-road-trip up to Thunder Bay in Ontario to spend Easter weekend with Jill's boyfriend, Peter, and some of their awesome Canadian friends. The weather was unbelievably terrible, so most of the weekend was spent indoors watching Game of Thrones, or in various Canadian coffee shops, restaurants, or markets playing cards and hanging out.

This is what a Canadian Easter looks like (photo credit: Sara Sloan)

That's okay, though, because we got a huge dose of nature awesomeness during our drive north. Shortly after crossing the border (I successfully managed not to say anything stupid to the border agent), we noticed what is becoming a very familiar sight this year: a great gray owl perched on the road-side telephone wires. That trip marked my fifth and sixth individual great gray owl sightings of the year! Naturally, we pulled to the side of the road to get a better look ("classic facial discs" -Jill). All of the sudden, two ravens came flying out of nowhere, dive-bombing the formerly peaceful owl. The owl immediately flew to a different perch, but the ravens were persistent, flying at the owl no matter where it flew. Eventually, the owl ended up flying down to the ground under the cover of some trees, and the ravens settled down, but remained perched nearby, seemingly ready to pounce should the owl attempt to relocate again.

As surprising an event as this was to witness, I was even more surprised to discover the birds mobbing owls is a fairly common event. Given that owls regularly eat songbirds, the mobbing is a defense mechanism when an unwanted owl is hanging around. Some researchers have managed to incite mobbing behavior in songbirds by simply playing an owl call in their vicinity. Turns out that corvids (ravens and crows) are both the most common mobbing culprits and also the most vicious; the "guarding" behavior that we observed is normal. This is also why one of the names for these groups of birds is a "murder" of crows and an "unkindness" of ravens.

Mobbing potential owl predators offers three benefits for songbirds. First, it will hopefully result in the removal of a harmful predator. Second, it is a way for parent birds to teach offspring which birds are dangerous predators. Third, if young notice this behavior is happening, it will typically act as a warning sign for them that a predator is nearby and they should take appropriate caution.

When songbirds want to initiate a mob, they will give a distinctive call, which acts as a "call to arms," harkening to the other birds in the area to assist in the mobbing. Birds of all sizes have been observed to participate: an Anna's hummingbirds (4.3 grams) was once observed mobbing a spotted owl (1.3 lbs), a 142-fold difference in size (for a comparison, think of a very small child poking an elephant in the leg with a stick). If owls are being mobbed by "harmless" birds, they will often ignore the event, sometimes even sleepily closing their eyes until eventually the mobbers give up.

In a study by Frederick Gehlbach, 60% of mobbings on screech owls happened during the breeding season. This is the time of year when owls are feeding themselves AND fledglings, so the rate of preying is significantly higher. Also, resident and wintering birds were found to initiate a mobbing more frequently than migrants - an owl is a greater threat to a bird that lives near it permanently than one that is simply passing through.

A couple days ago, I hiked up to Caribou Falls, a short one-mile loop of the Superior Hiking Trail. The ice is finally starting to break up and flowing water is beginning to appear again. While watching the half-frozen water fall, I once again saw some ravens ganging up on a dangerous predator, this time an immature bald eagle. Demonstrating very similar behavior to what I saw in Canada, they continued to launch themselves at the eagle until it eventually flew away.

This is what April in Northern Minnesota looks like. 

Raven Enrichment

(I apologize that the videos in this post are such low quality. I can't upload gigantic video files into blogger, so this is the best I can do).

I've posted a couple times about Korppi, our captive raven, and how she's a pretty smart bird (biggest brain in the bird world).  Since Korppi has this large brain, our daily challenge as animal caretakers is to keep her brain engaged. Furthermore, since she is living in a small enclosure instead of in the great outdoors, we need to keep her body active. We've been creating tons of daily enrichment activities for her, constantly assessing to see if the enrichment is keeping her occupied and appearing to be challenging to some degree. Her enrichment comes in the form of a multitude of different activities that encourage a healthy body and mind, but generally fall into four larger categories: 

-Foraging enrichment is creating a situation where Korppi has to work to obtain her food. This is especially important because ravens are scavengers in the wild, meaning they are always searching and working to obtain their food. For Korppi, we might hide peanuts around her enclosure, put raisins in the branches of her tree, bury a hard-boiled egg in the snow, put crickets in a plastic container with one small opening, or put live minnows in her pool of water. In all cases, she has to do some level of work to find and/or obtain her food, just like she would in the wild.

For this foraging enrichment, we gave Korppi three pinecones with peanut-butter and raisins in them. They are a relatively new item to her, so she is treating them with great caution. When ravens approach a potential food source in the wild, they have to ensure that it is dead, so they often will approach and then fly back quickly, as she demonstrates here, until they gain more confidence.

-Sensory enrichment is anything that engages Korppi’s senses of vision, hearing, smell, or taste. In other words, we are constantly putting novel stimuli in her enclosure to mimic the fact that she would always be encountering new things in the wild. This might include hanging a colorful toy from a perch, playing frog call sounds on a CD player, or adding interesting spices to her food.

For this sensory enrichment, we put a cake pan, a novel item, in Korppi's enclosure. The pan would initially be visual enrichment as it is new and shiny and if she eventually approached it, could be aural enrichment, as it makes loud noises when dropped, moved, and pecked at with a raven beak. In this video, Korppi is constantly moving around her enclosure, looking at the cake pan from all different angles. Eventually, she must have approached it, because when I returned later that day, it had shifted positions.

-Manipulanda enrichment is anything that Korppi can manipulate or “play with,” that will specifically challenge her motor skills. This represents the effort that is oftentimes required for ravens to obtain food in the wild. This might include giving her a phonebook to tear apart, hiding food inside a paper bag filled with newspaper strips, or putting treats inside of an old mayonnaise container that she has to figure out how to open up.

This is one of our favorite manipulation enrichment activities: half of an egg carton with peanuts punctured into it hanging from a perch. There are multiple steps that Korppi has to figure out how to maneuver: getting the carton up to her perch, getting the peanuts out of the carton, and then getting the peanuts out of the shells.

-Training involves working with a human and performing certain actions to earn positive reinforcement (in this case, raisins, mealworms, peanuts, etc). I wrote a little bit about training in a previous blog post (http://miskwaadesi.blogspot.com/2012/12/training-korppi.html). When Erin and I first started training Korppi, our main objective was simply to get her comfortable with humans (specifically us) and teach her to correlate humans with positive experiences. This primarily involved giving her lots of treats for coming closer and closer to us. As Korppi learned to trust us, we began to train her to do more complex activities, which has included perching on various perches in the enclosure, flying to perch on our arms, or staying in one spot while we enter and leave her enclosure. Training is an important part of Korppi’s daily enrichment because she is constantly trying to figure out what we want, how she can earn a treat, and we are able to positively reinforce behaviors that will help Korppi to be a more successful education animal.

I have been trying to incorporate students into the creation of Korppi's daily enrichment activities when I teach our birds class. I explain a little bit about Korppi's story and the necessity of enrichment to the students and then ask them what activity we should make for her. The kids always come up with great ideas. For example, one class had me take three identical containers into her enclosure and show her that I was putting apple slices into one of them. Then I mixed up the containers to see if Korppi would remember and go for the one with the apple slices first. She didn't, but he look of wonder on that class of eighth graders’ faces as Korppi figured out how to get the apple slices out of a closed yogurt container was just one more demonstration to me of how many great lessons this education animal can teach us all.

Ravens: Big Bird Brains

I've been working a lot with Korppi (our captive raven) these past couple of weeks, as I try to develop new enrichment activities for her and formalize an enrichment schedule. I know that she is a smart bird. In a recent training session, she learned that when I said "station" I wanted her to perch on a rock in the corner of her enclosure in a matter of five minutes and then proceeded to try and trick me into giving her more treats. I can see the wheels turning in her head when we present her with a contraption that she has to open or unlock to retrieve the food inside. At the risk of anthropomorphizing her, I would classify her reaction as "curious" when I hung a pair of sparkly pants from one of her perches last week. She's a smart bird. And I know from the literature (and straight up reputation) that ravens are considered one of the smartest. But I wanted to know why.

Korppi tries to retrieve peanuts punched into an old egg-carton top that was dangling from her perch.

So, I turned once again to Bernd Heinrich, biologist, author, and raven expert. I recently finished his second book about ravens, Mind of the Raven: Investigations and Adventures with Wolf-Birds. This is his account of his observations, experiments, and experiences with a group of captive ravens he reared, as well as many wild ravens that he encountered. I highly recommend the book - one story after another of the amazing feats and incredible mind-power of these intriguing birds.

To answer the "why" of all these smarts, we have to go straight to the brain. All vertebrates have a similar brain structure, composed of a hindbrain, midbrain, and forebrain. The hind and midbrain are generally responsible for sensory information and organizing movement and attention. The forebrain, on the other hand, is where conscious activity takes place, including learning and memory. While hind and midbrains don't show much size-variability in different vertebrate species, forebrain sizes are incredibly diverse. The reason humans have such large brains is because of our large forebrains.

In general, the greater one's brain volume, the more information that species can process. Bigger animals require bigger brains simply to control their bigger bodies; so brain size predictably increases proportionally to body size. When a brain is bigger than predicted based on body size, this is called "encephalization." Thus, second only to dolphins, humans are the most encephalized animals on the planet. In the 1940's Adolphe Portman, a Swiss zoologist measured and compiled data on bird brain volumes. He discovered that on average, the corvids (the family of birds to which ravens belong, in addition to crows and jays) have the highest encephalization of all bird families. As it turns out, ravens are not only the most encephalized of the corvids, but of all the birds.

We can correlate intelligence with brain size because more brain volume means more neurons and synapses, which are directly connected to one's information processing powers (this is neuroscience at its most watered down aka the only way I will ever understand neuroscience!). When discussing intelligence, though, we have to clarify intelligence "with reference to what." Most primates, for example, have high levels of encephalization and the extra "brain space" is dedicated to visual processing, because they are highly visual creatures.

So why do ravens have such high levels of encephalization? One could argue that extra bird-brain-space is needed for flight capabilities; however, dragonflies (and other flying insects) have four wings, six legs, and no encephalization, while ravens only have two wings and two legs. Furthermore, having a large brain is a HUGE energy expenditure: humans' brains take up 1.5% of our body weight but 20% of our energy reserves. Anthropological studies have shown that human brains made a leap in size when humans switched from being strictly herbivores to omnivores. Nonetheless, hawks and ravens are equally effective predators, despite hawks' significantly smaller brains, so the ability to hunt is a weak explanation for an enlarged brain.

The latest research is actually indicating that ravens' (and our) large brains could primarily be accounted for by social complexity. In turn, the ability to not just recognize others, but SPECIFIC others increases social complexity, creating a sort of positive feedback (big brains enable social complexity which encourages bigger brains). Ravens are highly social creatures: Heinrich describes in many chapters the social hierarchies that exist within groups, their ability to recognize other individuals, the formation of pairs and coalitions of pairs, and the mutual relationships formed with dangerous predators. These and more require instant reactions and making choices that when made in the head, are much safer and quicker. In other words, they require consciousness. That ravens are such social creatures seems to explain, more than anything else, their large brain size. And that large, encephalized brain, is why Korppi has no trouble remembering where she's cached hundreds of raisins all over her enclosure, among many other remarkable feats.

Korppi investigates the strange, black box I've brought into her enclosure.

Training Korppi

Korppi's first day at Wolf Ridge

At the beginning of the school-year, a new education animal joined the team at Wolf Ridge, a common raven we named "Korppi" (the Finnish word for "raven").  Working with Korppi quickly proved to be an entirely different situation than working with the education raptors.  Ravens are significantly smarter than raptors and require daily enrichment.

Korppi's enrichment comes in a number of forms.  Every day, we try to present her with a different challenge for obtaining her food, whether that involves hiding it somewhere in her enclosure, putting inside of some sort of puzzle-container, or simply giving her something that is challenging to eat (like an apple or a pumpkin).  Enrichment also comes in the form of training, which is something that I've been working with her on a daily basis.

When she first arrived, Korppi needed to simply become comfortable with me and learn to associate me with positive experiences.  So, I sat in the corner of her mew and threw raisins for her to eat.  Eventually, she would come closer and closer to me until she was eating raisins right next to me.  Then, she spent a couple of days eating raisins off of my shoes before she finally worked up the courage to take them right out of my fingers.

Korppi tentatively investigating a pine-cone full of raisins

My next project was to crate-train her; that is, train her to voluntarily go into a travel crate so we can take her in and out of her enclosure.  This started off pretty good, but we reached a point where Korppi was refusing to enter the crate (even though she clearly knew what I wanted) and was beginning to get aggressive with me.  I figured out that we hadn't built up enough trust together yet, especially since her only experience with crates up to this point was being involuntarily stuffed into and out of one before she arrived at Wolf Ridge.  Her negative association with crates coupled with our quickly fading trust with each other created a situation that was not working for either of us.

At this point, it was time to focus on building trust together, so I spent the next month training her to perch on a scale perch during which I fed her lots of raisins.  Throughout the course of the month, I began to notice a change in our sessions as Korppi became more relaxed with me, nipping at my fingers less and less.  I also became more relaxed and I think my awareness of my body language contributed to our progress.

And then, today happened.  As Korppi was perched on her scale perch, I had my arm extended just below the perch and without any prompting, she stepped onto my arm.  I was completely caught off guard and made sure to reward her immediately.  It was an exciting moment - a testament to the trust we've finally built with each other.  She stepped up on my arm five or six more times today without any hesitation.

A moment I'm always going to remember

Now that she trusts me enough to step up onto my arm, we can move forward with some other training activities when I get back from Christmas break.  Where will our training sessions go from here?  Sometimes, it seems like that is more Korppi's decision than mine.