Showing posts with label ravens. Show all posts
Showing posts with label ravens. Show all posts

Monday, December 12, 2016

Name That Track! Ichnology Fun For All!

Hello Dear Readers!

The end of the year rush to get things wrapped up for 2016 has hit, and I am a busy ichnologist! The data collection is nearing the end, and once that end is nigh I can move on to analyzing all of that data. We'll see if the hypothesis I'm testing will be supported (yay!) or if the data don't support the hypothesis (huh, well that's interesting, what else could it mean?)

Note: don't get too attached to your hypotheses. If your data end up saying "Hold up: your hypothesis doesn't really describe me all that well. Can you try again?" listen to the data and rethink your approach. Maybe you need a different way to test your data. Maybe you need a different hypothesis.

One thing that I am quite pleased to talk about is a new ichnology-based game I've started on Twitter called Name That Track. It was an idea that I've had for a while now, but the implementation was inspired by Dr. Michelle LaRue's very popular Twitter game "Cougar Or Not." Tweeters look at a picture of a critter, and they have to guess if that critter is indeed a cougar. It's not as easy as it sounds! Depending on the picture, house cats, bobcats, and even deer can take on a cougar-ish look.

Name That Track is similar, but with pictures of footprints instead of animals. Every Tuesday morning I post one of the modern footprint pictures from my collection (I take a lot of pictures of footprints from modern animals) and people tweet me their guesses.

I started the game with everyone's favorite floofs: footprints of cats and dogs. I did a test run in January by posting a picture of a cat footprint and asked Twitter "Cat or Dog". People jumped in with both feet and made great observations.

Here are the images I've used to date.

A cat track in cement (please don't let your furry friends walk in cement: it's bad for the skin on their paws),

Our favorite Common Raven,


A festive Wild Turkey for the American Thanksgiving,


And, most recently, a Canada Goose track.


The most recent Name That Track - the Canada Goose - was a real eye-opener for me on how people see tracks. About half of the people who responded looked at the footprint and didn't see three pointy bird toes: they saw the curved outline of the sides of the footprint and the spaces in-between the toes and saw a large ungulate track (elk or moose). The other half of the respondents saw a the track of a large bird.

I'll admit: it took me reading several of the moose guesses for me to see why people were guessing moose in the first place. Then I switched gears and thought to myself "OK, let me see this as a moose track." Then the two hoof-like shapes popped out at me and the rounded side edges of the track came into focus, and I had the "Aha!" moment. This is valuable information for an ichnologist who likes to teach people about tracks and what tracks can tell us:

1. Differences in depth are difficult thing to convey in 2D photographs. Ins look like outs. Highs can look like lows. Non-specialists are used to seeing footprints that are innies, or impressions in the ground. Showing someone an infill of a footprint, or the positive relief version of a footprint can be confusing. Being clear about whether the image I'm showing is an impression versus a plaster infill of a track is very important for people wanting to understand the track.

 2. Edges are important. Our eyes are drawn to edges that define spaces. A track with poorly defined edges is going to result in a poorly viewed track. This particular Canada Goose track did not have very clear webbing impressions. Were the webbing visible, people would have made the goose connection based on that. It's also important to note that footprints oftentimes don't preserve the features we think we need to identify them...or if they are preserved, they lead to an inaccurate identification. That was revealed to me with the Wild Turkey track. The detail on the footprint is gorgeous, but I overlooked the small amount of webbing that was clearly preserved. Most people don't associate webbed feet with non-aquatic birds (why would they?), so it turned out the Wild Turkey received a few duck and goose identifications. Both the goose and the turkey print provided an opportunity to nerd out about cool features on bird feet, and the explanations were well-received. No harm, no fowl.

3. Scale matters. One of the things we are trained to do as paleoichnologists is not focus on the size of the track. We have to focus on its shape, because it's hard to tell if a size difference between two tracks is because they come from different species of track-makers, or if the small track is simply the young version of the large track. When we're showing certain modern tracks to non-specialists - particularly ungulate and bird tracks - scale does matter because there are closely related species coexisting whose feet differ only (in a general sense) in scale. Think of the footprints of an American Crow versus a Common Raven. They are both tracks made by corvids, and those tracks are really only different in size (in general). Knowing the scale helps people narrow down the list of potential track-makers because they are familiar with the sizes of modern-day animals. Size can be a useful diagnostic tool for modern tracking.

One exception I make for the "scale matters" rule is when using images of the footprints of domesticated dogs and cats. There are so many different sizes of dogs - and so many different sizes of dog feet - that there are footprints of small dogs the same size as the footprints of house cats. The reverse is true for large dogs and our large wild cats: the footprint of a large breed of dog can overlap in size with the footprints of bobcats, lynx, and cougars. That's when footprint shape and proportions become important. The exercise in trying to tell dog tracks from cat tracks is very similar to what we do to tell apart the different types of dinosaur footprints.

4. No trying to trip people. I might inadvertently stump people (like with the above mentioned Canada Goose footprint), but I have no intention of posting an ambiguous tracks and laughing evilly to myself in my secret lair (well, not any more evilly than I already laugh.) Being able to tell dog, cat, bird, ungulate, etc. is a great first step if you're not familiar with tracks. As you get more experience, the identifications can get more specific. All of the footprint pictures I'm going to post early on for Name That Track are of single clear (relatively) footprints. I've also seen who has made the footprints while the footprints were being made (particularly for the bird footprints - it's part of my research), so I'm not guessing at the identity of the track-maker. I do have some doozies that make my eyes cross, and those won't make an appearance until well in the future...or unless people cry out "Enough dogs and cats! Give us a toughie!"

Name That Track is not only a fun educational game, but it's also teaching me how non-specialists see tracks and how to talk about tracks the way that non-specialists see them. So, to all the people who play Name That Track with me: THANK YOU! I'm hoping I'll be able to keep Name That Track running for a long time. So, join me on Twitter every Tuesday and play Name That Track and let your inner ichnology nerd shine!

What will it be this week?
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Monday, May 16, 2016

Raven Regurgitates: Strange Woman Now Collects Bird Barf

I'm already the strange woman in the ditch looking at bird tracks, and the strange woman dashing on to the middle of the road to pick up roadkill, so I might as well be that bloody strange woman walking along the bridge on the highway, picking up raven barf.

We all have our hobbies, after all.

Yesterday (Sunday, May 15) our dojo did our annual highway cleanup. Having recently received the renewal for our institution's wildlife salvage permit, I was on the look out for recent roadkill. Birds and small mammals are all my recovering dermestid beetle colonies can handle at this point (thanks, wolf spider), but besides a couple of very flat mice, there was no roadkill to be had.

Wuz in ur coloneez, nomming ur beetlz.
What we did see, when walking over one of the highway bridges close to the local boat launch, was a railing full of raven traces in the form of poop (yes, it's feces, but poop is more fun to write) and regurgitated pellets!

Most people are familiar with owl pellets or regurgitates. Owls tend to swallow their prey whole or in large chunks. Bone, fur, feathers, scales, skin, exoskeletons, and anything that the prey was eating (seeds and vegetation) are all swallowed. The gizzard of the owl compacts all of this hard to digest and indigestible material into a pellet, which the owl later regurgitates.



Owl pellets are fascinating, and form the base of a really fun educational activity: owl pellet dissection! It's a wonderful way to demonstrate the food web and predator-prey interactions, and predator diets. Owl pellets are also an invaluable source of dietary data for ornithologists studying the prey of target owl species. Owl pellets can also provide insight into the preservation of small mammal fauna from Cenozoic sediments: a paper by Terry (2004) examines what happens to the pellets of extant Great Horned Owls (Bubo virginianus) as they break down in a temperate forest environment. This another great example of how studies on modern ichnology (pellets are traces of an organism, so they are 100% in the realm of ichnology!) give us a better understanding of fossil ichnology.

Owls are not the only birds that regurgitate pellets: birds of prey, gulls, herons, cormorants, shorebirds, and corvids. Bird species that consume a great deal of indigestible material with their meal are likely to hack up pellets.

This morning I went to the bridge to see how many raven pellets I could collect for our institution's summer educational activities. We already have a Barn Owl pellet dissection activity, but Barn Owls are not native to northeastern British Columbia. The Common Raven, however, is ubiquitous in our region.

It was easy to see which side of the bridge the ravens preferred to perch on: the side that is closest to the boat launch. Our local ravens figured out that where there are trucks, there are people and the tasty things that people leave behind.

This Common Raven watched me from the boat launch the entire time I was rummaging around their bridge perch.

Clearly ravens spend a great deal of time on this railing.


I set to work choosing my samples. It was clear which deposits were pellets, and which ones were raven poo.


I did not arrange these deposits for the photo. The deposit on the far left has passed through the digestive tract and was deposited via the cloaca: you can see the white material (uric acid) and the small mounds underneath the uric acid. The deposit in the center is a nicely intact pellet. There is white material in the pellet, but it is solid, thin, and fragments of a once larger object. Our working hypothesis is that it is eggshell that this particular raven picked out of the trash. The deposit on the far right is full of fibrous vegetation and uric acid. It may have been a pellet that was later pooped on, or it was fecal in origin and has weathered a lot before I came across it.

I collected two intact pellets, and have passed them on to our Education Coordinator who will now heat sanitize the pellets. This site is easy to access, so we have the opportunity to collect more throughout the year. Once the pellets are sanitized, the kids participating in the Owl Pellet Dissection can compare the diet of a Barn Owl to that of their local Common Raven.

Wish me luck in finding more local bird pellet locations!


References

Terry, R. C. 2004. Owl pellet taphonomy: a preliminary study of the post-regurgitation taphonomic history of pellets in a temperate forest. Palaios 19(5):497-506.
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