Where have all the snails gone?

The above map I put together based on the summary paper by Jass (2004). In this paper, she echoes the call of Hubricht (1985) and others that much of the upper midwest is woefully undersurveyed for snail abundance. Notice the large number of Wisconsin counties with fewer than five land snail species reported for that county. The most populous counties (Dane, Milwaukee, Brown), those with state universities within them, have the highest abundance. This is definitely not a result of natural distribution - I've found snails in counties that have no official records. It likely reflects the fact that the researchers concentrated their efforts close to home. What does this mean? If we want to know the true extent of the distribution of snails on this continent, we need more people looking for snails. They are an excellent indicator species and have a great deal to tell us about the modern (and ancient) environment if we'd only stop to listen.

Science and Reason: Philosophia Naturalis #1

Science and Reason: Philosophia Naturalis #1

Sorry for any repeat links - I'm trying out a remote linking option on blogger. But hey, this is the first carnival for this one, so it deserves two links :)

Carnival Hat Trick

In short order, I have three posts at three different carnivals - including a brand new carnival, sure to please all you physical science types.

The first is over at The Tangled Bank #62:

A travel bingo edition complete with drawings by the host. Very cool - and check out the rest of his site - very talented artists over there.

Next up is I and the Bird #32:

A fellow north-woodser gathers a slew of fascinating posts about birds. Who knew that there was another naturalist blogger in this area. How cool is that?

Finally, the brand new science carnival, Philosophia Naturalis #1:

Science and reason has something for all you chemists, physicists, and non-biological earth science types. Check it out - and you geo-bloggers better step up to the plate!

Whew! I'm spent. See you for the next round in a couple weeks...

The Driftless Area, pt. 2

How did the Driftless Area form?

In the previous post, I talked about the what and where of the Driftless Area. This is a brief discussion on how. During the last Ice Age, the thick sheets of ice that covered much of the northern part of the US and nearly all of Canada went around the Driftless Area. How did that happen? There are a couple of primary thoughts regarding this. The first and most likely is a result of the highlands of northern Wisconsin and the Upper Peninsula of Michigan (UP). The second is slightly more complex and factors in the amount of liquid water at the base of a glacier. Liquid water? At the base of a glacier? Yup - and I'll mention why later in this post.


The most cited explanation (e.g. Syverson and Colgan, 2004) for why the glaciers bypassed the Driftless Area is because the area in northern Wisconsin and the UP is topographically higher (even pre-glacier) than the surrounding region (see figure on the right). This diverted the glaciers around them, and slowed its movement enough to prevent the ice from covering the Driftless Area (green circle). A subset of this idea is that while lakes Superior (upper left) and Michigan (lower right) were not as they are today, they were likely topographic depressions that would have acted as channels that encouraged ice to flow through them, bypassing the area inbetween. These hypotheses are quite robust - they explain how the Driftless Area avoided being covered by ice, and are backed up by a great deal of geological evidence such as glacial deposits, glacial striations on bedrock, and computer modeling.

Another possibility is that the porosity of the bedrock in the Driftless Area absorbed the liquid water at the base of the glacier, and prevented it from flowing into the region, "gluing" the ice to the ground. So how does water get to the base of a glacier? One is that this far south, there was a considerable amount of melting going on, even in the winter (it is warmer down here than it is way up north, after all). This water flows down through the ice and often finds its way into (or creates its own) channels along the base of the glacier. Another way is through pressure. With increased pressure, the temperature required to melt ice decreases. At the base of the glacier the pressure is sufficiently high enough, and it is not cold enough, so that water can exist. This film of water acts much like the film of water beneath a pair of ice skates - reduces friction and allows the ice to flow faster. No water, no flow (or very, very little). Hence, the Driftless Area, with its porous bedrock allowed water to get away from the glacier, and prevented the ice from moving.

This film of water is also what alows modern glaciers to surge, sometimes a hundred meters or more in a day. The water reduces friction so quickly that the ice just shoots down the valley. With increasing global temperatures, the chances of more glaciers surging increases. Without increased input of snow and ice near the head of the glacier, it could disappear all the more quickly. Granted, this is a simplified prediction of a complex process, but in basic terms, it's one of the concerns glaciologists have as the earth's temperature continues to rise.

The Driftless Area, pt. 1

What is the Driftless Area?

Simply put, the Driftless Area is the region in Southwestern Wisconsin, Southeastern Minnesota, Northeastern Iowa, and Northwestern Illinois that was not covered by the late Wisconsin glacial ice and has a characteristically rugged topography. The broad plateau of paleozoic bedrock (mostly limestone, dolostone, and sandstone) is deeply dissected by the river drainage systems here because this area has been exposed to weathering for much longer than the surrounding area. Glaciers act as a kind of eraser - resetting many geomorphic features by planing off the high regions and depositing a thick blanket of glacial sediment, referred to as a 'ground morraine.' The older name for undifferentiated glacial sediments was 'drift,' hence the name for this region.

map data available from: http://seamless.usgs.gov

My research revolves around looking for snails buried in alluvial sediment within the Driftless Area. These late Pleistocene-aged snails were living in this region while there was ice less than 100 kilometers away. There's evidence for permafrost - and permafrost requires a mean annual temperature below freezing. While permafrost would inhibit the growth of trees (too cold, frozen ground prevents rooting), there are snails in the southern part of the Driftless Area that feed primarily on deciduous trees. This suggests that the permafrost was not continuous in the south, but perhaps it was farther north. One of my goals is to describe where different snail species are present and where they are absent (although absence of evidence is not exactly evidence for absence). Significant changes in the distributions of various species could indicate where there might have been some trees hiding from what must have been a cold and rugged climate. So maybe it wasn't as cold and nasty as people think - at least in some places.

So, why did the glaciers miss this part of the country? That's a post for another day...

UPDATE: Part two is up.

It's right around the corner

Fall is fast approaching. The birds are in bulk-up mode, preparing to either tough out the snow and cold, or head on a long journey south to fairer climes. Berries and fruits are still in ample supply, and all maner of fowl are taking full advantage of it. Here's a photo I snapped a few years back when I was down on UW-Madison's campus:



The birds up here on the north shore are just as busy (even getting started a week or two earlier), and the hawk migration is gaining momentum. Soon, kettles of broad-winged hawks, turkey vultures, and bald eagles will be soaring high over my house. I can't wait.

Spineless Circus #12

A wonderful post for the 12th circus of the spineless is up at Sunbeams from cucumbers. Check it out!

A garden visitor

It's almost September. That means for those of us along the big lake, summer is winding down. Pretty soon, we'll be at risk of frost and the vegetables in our garden will have to come out. This dragonfly decided to rest amongst the morning glories yesterday afternoon - it was still there this morning. I don't know if it's waiting for some sun and warmth, or getting ready to suffle off the mortal coil. But it afforded me a nice long photo session.

Katzenheimer

Messing around with my art tablet, I dressed up my cat.

Boundary Waters Canoe Area

Quiet Tyme:




Spent 4 days in the Boundary Waters Canoe Area Wilderness. A pleasant trip to get away from the stress of prospectus writing.

Papers read last week: climing snails and left-handed snails

For those of you who have visited this site in vain to find something new: I apologize to both of you. The demands of a dissertation have taken center stage.

Effects of Rock Climbing on snail diversity:

A while ago, I was perusing some snail literature and I ran into an article by McMillan et al. (2003)¹.

It had gotten picked up by one of the science news (http://www.sciencenews.org/articles/20030412/fob4.asp) feeds and the summary article garnered two comments, which I've quoted here:

I feel compelled to respond to this article. No one can enter and leave the wilderness without a trace, whether on foot, bike, horse, all-terrain vehicle (ATV), skis, snowmobile, or snowshoes. However, rock climbing is among the least invasive outdoor activities. Apparently, someone with a personal vendetta against rock climbers discovered that a snail population in one location might be affected by climbers. Is there anyone available to consider the effect of a single, noisy, smoke-spewing, oil-dripping ATV on a forest road?
...
Your article seems myopic. This is like doing a study to find that there are fewer species living on trails than untouched land. The benefits of the sport of climbing to the environment are much more important than this finding. Every climber is an environmentalist and open-space advocate.

My first reaction is that these folks commenting assume that because their recreational activities have a more subtle effect on nature than say ATV folks, they should be exempt from scrutiny of the impacts of their recreation. Nothing could be further from the truth. By that rationale, one could say that because I am trying to understand the ecological history of snails and because I feel that the results I get are by an large good for the environment, I don't need to understand the impact of my activities. There are times when "environmentalists" pat themselves on the back too much. Everything we do on this planet will affect the communities of organisms we are near. Bootstrap Analysis had an excellent piece on the perils of feeding feral cats. You may certainly think of yourself as a "nature lover," but don't be surprised when you find out that you're causing problems just by 'being there.'

My second reaction is that the comments are understandable. If given a choice between reducing ATVs and climbers, I would start with ATVs. But it also has an important message for resource managers: ALL trails have an effect.

---

Left-handed snails

My second paper was written by Dietl and Hendricks (2006)²

First off, a little disclosure - I worked with the 2nd author at the Geology Museum at UW-Madison for several years, so I know him personally.

This paper was interesting - their proposal was that sinistrally coiled snails persist (despite the disadvantages: see Aydin's Snail's Tales for further discussion) because there is an anvantage in surviving predatory attacks by crabs. Their null hypothesis was that handedness has no impact on scarring from crab attacks (not every attack is successful). They rejected their null hypothesis, so therefore the left-handed snails were statistically less likely to bear predation scars. One explanation they provided was that sinistral snails were more likely to be destroyed by predators (thus the fewer scarred survivors), but they felt that this was unlikely given the similarity in morphology and other shell characteristics.

So why the significant difference? They - and others studying the existence of left-handedness in people - propose that there is a survival advantage. Encounters with left-handed organisms is rare enough that right-handed organisms are at a disadvantage when it comes to direct conflict (such as a left handed batter against a right-handed pitcher) and thus left-handedness conveys a survival (or batting) advantage. Thus, the trait persists - if it was completely deleterious to be left-handed, one would assume that there wouldn't be any left.

I agree with the basic idea of the left-handed advantage. I also think that the results of Dietle and Hendricks (2006) are compelling. But, I think that both the researchers, and others in the past, have approached this issue from the wrong perspective. Namely it is rather anthropomorphizing to call them left-handed and right-handed and one needs to be careful in drawing overly broad generalizations about handedness. Still, it may help explain why - despite its deleterious effects - sickle cell anemia persists, since it does convey a higher likelihood of survival against malaria. But that's the post for another day.


¹McMillan, M.A., J.C. Nekola, and D.W. Larson. 2003. Effects of rock climbing on the land snail community of the Niagara Escarpment in southern Ontario, Canada. Conservation Biology 17(April):616-621.

²Dietl, G.P., and Hendricks, J.R. 2006. CDrab scars reveal survival advantage of left-handed snails. Biology Letters. (Published online - sorry, I don't have a link right now).

The operculum

Most snails, we are told, have an operculum. A flattened piece of hard material that acts like a door to the opening of the snail shell. While probably an effective barrier to predation, many land snails have abandoned the operculum. Instead, they seal their aperture with a mucous-based material called an epiphragm. In my opinion, the casting away of the operculum is probably the single biggest step towards being successful land invertebrates snails have taken since the evolution of the Pulmonata.

That's all I have to say about that right now - but an out loud thought I have regards extra space in the body whorl of operculates versus non. I suspect non-operculate snails have more extra space in their body whorl, but I don't have the data to back up that hypothesis. Anyone want to write a paper?

A little help?

I've got a snail that's proving hard to ID:



At first I thought it was Neohelix albolabris based on the size (it's 24mm wide) and shape/size of the reflected lip. But, its umbilicate, and Neohelix is not. So... any ideas? Burch's 1962 field guide hasn't helped me here. Perhaps it's an introduced spp? I posted an earlier pic because it has an interesting predation scar pattern.



I'm pretty sure this one is Mesodon given that it's about 2/3 the size of the first and the other characters do match with the description.

Beringia mollusks

Just came across an article - haven't read it beyond the abstract and a quick scan, but it's got some interesting info regarding Beringian mollusks. Primarily they suggest mollusks were introduced by migratory birds to the area. Hmmm...

LAURIOL, B., Cabana, Y., Cinq-Mars, J., Geurts, M.A., Grimm, F.W. 2002. Cliff-top eolian deposits and associated molluscan assemblages as indicators of Late Pleistocene and Holocene environments in Beringia. Quaternary International. 87, 59-79.

Reminds me of a previous post by Aydin regarding a book on a similar topic.

The Circus is in town!

Welcome to the 7th Circus of the Spineless!

We have all manner of posts for you, this month. With this handy dichotomous key, we can help you identify any post you might come across. Be sure to key out your specimen properly, or you might be surprised what "Inverteblogs" will appear.

1a. Post is not about Porifera ........................................ 2
1b. Post is about a sponge:
Circadiana (a.k.a. coturnix) with: sponges have circadian clocks?

2a. Blog is about an arthropod ...................................... 3
2b. Blog deals with a mollusk ........................................ 8
2c. Blog is about an echinoderm:
Medlar Comfits regales us with: Breakers Laundry

3a. Blog deals with Chelicerata ..................................... 4
3b. Blog caontains Lepidoptera ..................................... 5
3c. Blog deals with Diptera ........................................... 6
3c. Blog deals with Coleoptera .......................................7
3d. Blog deals with an insect that looks like another:
Bev provides the audience with: Insect Imposters

4a. Post is about a big spider in New Zealand:
White Tail Spider thanks to Pete
4b. Post is about a smaller spider in the northern hemisphere:
Bev with Spider Ranch

5a. Post is about moths and light pollution:
Rigor Vitae presents a Moth in the night sky
5b. Subject of post looks like a carpet:
Cindy brings us Scaled Wings
5c. Blog has picture of moth just sitting there:
Ben has a picture of A moth hanging upside down.
5d. Moth is in florida:
thingfish23 finds out that Sometimes they come back

6a. Blog discusses halteres:
Budak tells us A tale of two-pteras
6b. Post is about insects eating insects:
Ben has a picture of A light snack?
6c. Perhaps the most disturbing post in the circus:
Thoughts from Kansas forces us to confront Sometheing we don't want to have - ever.

7a. Post gets inspiration from the ancient Egyptians:
Medlar Comfits praises Dung Beetles.

8a. Mollusk has a really funky shell:
Aydin found a Frankensnail.
8b. Mollusk has been attacked, sometimes repeatedly:
Pascal found evidence of Snail predation.
8c. Last but not least:
tai haku has pictures of Colorful Squid

Apologies that this is a little late - I got lots of good posts. Hope you enjoy them as much as I did.

COTS right here!

I'm extending the deadline for the Circus - Blog Carnival has it listed a little later, so please get things to me ASAP, but if you're a little after 4pm - no biggie!

Reminder

Submissions for COTS #7 will be due on the 30th at 4pm. Don't be shy - send me a link!

capn.pituitary AT gmail.com

or, place a comment on one of my COTS threads.

See you here on the 31st!

Sinister snails

Dietl and Hendricks (2006) recently published an analysis of left-handed versus right-handed marine gastropods (mostly Conus and Busycon). Seems their results indicate a preference for sinistral shells. I want to get a copy of the article before getting into more detail, but since I went to school with the second author, I thought I'd give a quick shout out.

BBC news post.

Dietl, G.P., Hendricks J.R. 2006. Crab scars reveal survival advantage of left-handed snails. Biology Letters. Early Online Publishing.

It's not what you eat: it's the way how you chew it.

Going through my samples that I had collected this past fall, I came across a few examples of predatory attacks on snails:

Vallonia pulchella

The aperture of this Vallonia sp. was peeled back considerably - perhaps about 1/3rd of the entire body whorl. Yet the snail was able to regrow a new aperture (albeit short of the original length). As you'll see later, the regrown shell does look scarred - like a healed burn or deep cut on our skin. There are two points that are most interesting to me here: 1) this snail is less than 2mm wide, and 2) the snail survived an attack from a predator small enough to delicately peel back the shell of this tiny snail (my guess is some kind of carabid beetle).

Neohelix albilabris

At least, I assume it's a Neohelix. It's about 3cm wide and fits with descriptions that I've looked up. Aydin - if you have a better ID, I'm all ears. What really amazes me about this snail is the fact that it survived at least two different attempts to peel away the shell (black arrows).

Pupoides albilabris

The "White-lipped Dagger Snail" (cool name) has only been reported for the area where I found it once (Theler, 1997). However, the hill prairies of southwestern Wisconsin are under reported and surveyed, so I'm not surprised. What impresses me about these sampes is that there is a predator dextrous enough to peel back the body whorl to get the snail inside. I know that some birds and shrews eat land snails, but to peel back a shell at this level of detail probably requires something smaller. Something in the Caribidae, perhaps (ground beetles).

This relates to a post by Aydin: about snail predation as regards snail survival. As biologists (paleobiologists) we often see the remains of what doesn't work. Given the mathematical nature of the intrinsic rate of increase, it does not take much change in this rate to result in a significant improvement in reproductive success.

There are many changes in shell morphology that have been assumed to convey some improvement in success for terrestrial gastropods. Most of these have to do with the thickening of the aperture or "teeth" inside the aperture. However, my thought is, that the most successful adaptation for snails to survive predation is the mantle's ability to reprecipitate calcium carbonate.

Birds and Cats

My wife and I have two cats. One, Birke, is a textbook mouser. He plays with toy mice every day, sometimes for nearly 15 minutes at a time. When he was younger, I literally watched him play with a single mouse-toy for more than an hour. Like I said, he likes mice.

Our other cat, Pippin, loves to chase bits of paper across the floor, but has shown a real affinity for birds. He's a tad pudgy and doesn't jump as high as he used to, but little winged things really get his attention (he loves the bugs that get into our house as well). Earlier this week, we had a Pine Siskin pigging out at our window feeder - and Pippin was right there:



We keep our cats indoors, but let them outside with a leash and supervision - cats are far too good at catching wildlife to let them out on their own. But apparently, this Siskin didn't care - the cat swatted the glass several times, and the bird just stayed there, eating sunflower seeds. I can feel winter loosening its grip - both on my wife and I, our cats, and the birds. It will be nice to have summer birds at the feeders again. Besides, it will give Pippin something more to watch...

contact me

PS - you can get hold of me either through email (capn.pituitary AT gmail.com) or by leaving a comment on this post, or any other recent entry.

I've got three super-punctual folks who have sent me entries - be sure to get yours in by the 30th!

Squish-crunch vs. Crunch-squish

As a paleontologist, I'm faced with the fact that all of the stuff I work with is whatever didn't decay and rot away. I worked for several years at the UW-Madison Geology Museum both as project assistant, researcher, and tour guide. Our tours are geared towards kids, and one thing kids love is mild gore. So, as a mneumonic for remembering the difference between vertebrates and invertebrates, we had squish-crunch and crunch-squish. Which is what each group would do if they were stepped on. A bit gruesome, perhaps, but it got the point across. Vertebrates, with their bones inside the body will squish before the skeleton crunches. Invertebrates, with their hard parts on the outside, obviously will do the opposite (if they have anything to go crunch in the first place - but we don't find them as fossils, so that's not as much of a concern in a geology museum).

Those of us involved in paleontology can get lost in our own world. One of the things I like about having to give tours to 4th graders is that one is forced to put complex ideas into simple (perhaps graphic) terms.

COTS right here!

At the end of the month, swing on by for the rootinest, tootinest, spinelessest blog carnival of them all. Circus of the Spineless will be right here. If you have a submission, please send it in by 4pm CST, March 30th. See you here!

The little engine that could (tell you where it's going).

Earlier, Aydin at Snail's Tales posted photo evidence for his interpretation of a locomotive engine. I still think there's a chance it might not be an engine, but the simplest and most complete answer is that they are indeed locomotives.

So what about his first question? How can you tell what direction it's travelling? Trains don't do too well when pushed, so the majority of the time (if the train is moving), it is likely that the locomotive is pulling the cars. The cases where this may not apply are usually in rail yards or along industry spurs. If you see a picture of a long train, out on the mainline you've got a better than 50% chance that it's pulling the cars and not pushing them (assuming, again, that the train is moving).

I hinted at a case where you could be nearly 100% certain of dirction:






The picture at top, the steam engine is moving backwards and forwards below. Notice the smoke plume leaves a nice trail. Provided the wind isn't too strong, you could get an easy idea of motion. However, this doesn't always work either: sometimes they don't make much smoke.

Blogger?

Blogger has been acting a little odd. This is the first time I've been able to update in several days.

PS: Circus of the Spineless will be here (and I will have a backup to keep people going just in case)

Where railfanning and science collide

A recent post by Aydin about trains from above piqued my interest. At first, I looked at his interpretation and, being something of a railfan, I felt that I could correct and supplement his interpretation.

At first, I discounted his interpretation of the two darker-roofed cars on the left side. But, trying to be objective, I had second-thoughts. I can't just discount his interpretation based on my assumptions. I have to be able to falsify interpretations. Really, a wonderful application of science. So lets look more closely at his photo and interpretation. This photo below is taken from his site and his arrow points to what he interprets as the two engines of the train. The primary question he asks was "how can you tell what direction the train was going based on a satellite photo?" I'll get to that question later, but first, lets address Aydin's interpretation of "engines" on the left side of the string of cars:



Here is his closeup:


Aydin's interpretation that these two cars on the far left were engines. I discounted this - why did I? Because in general, locomotive engines have distinct roof-top characteristcs that would stand out even in satellite view:

Here's a slightly more oblique view of an enigne pulling a train of boxcars. Note the distinct patches on the top of the engine.

Big thing is the three large circles on the long end. These radiator fans (some have two, some have three) are extremely common. However, not all locomotives have these fans (this is what I jumped on first, but if one must be objective, we have to determine if this assumption is valid). However, all diesel locomotives have some kind of dark grille on their tops. There are some darker spots on those two cars in the above satellite photos. But, they aren't in distinct circles or rectangles which nearly all locomotives have.

However, there are electrified locomotives which are relatively box-like and don't have obvious grilles on top. But the boxes on top of the locomotives to hold the pantograph (the thing that touches the overhead wires) stands out. The tops of the cars on the far left of the satellite photo are smooth (albeit a little darker than the others).

The only difinitive characteristic that I don't see is the windshield. All locomotives have at least a little break in their shape at the location of the windshiled. Given the lack of radiator grilles and windsheild break, I am interpreting those end cars as boxcars. The beauty of interpretation of observed data is that I might be wrong. I would imagine someone could put forth a set of characteristics that would contradict my interpretations (which is different from Aydins'). It's science with all the warts and wrinkles that personal interpretation brings with it.

So, to answer Aydin's question: what direction is a train going? That's an answer for the next post.

March Circus Right Here!

Come one, come all. The March installment of the COTS will be here. It's been a slow couple of months for my blog-wise, but productive for research.

Email me: capn.pituitary AT gmail.com

I'll have a few reminders soon - come on by!

The "Ouzel."

It was a few years ago that I first picked up my own copy of David Sibley's bird guide then followed his "Guide to Bird Life and Behavior." Being an artist and naturalist, I loved just looking at the birds as paintings - it was amazing how he managed to capture feather patterns with brush strokes.

One bird, in particular, grabbed my attention: the American Dipper (Cinclus americanus). Specifically, his sketch of it walking along the bottom of a cold mountain stream. It quickly became one of those bird I had to see myself. My first opportunity came the summer of 2004 during field work in Wyoming. I didn't see much of it, but there was no mistaking the bobbing, the white eyelid and the squat little charcoal body. A vacation to Rocky Mountain NP later that summer netted me a fine picture:




Back in Wyoming the following summer, a family of Dippers made the stretch of stream near our camp its home. Every day, two juveniles would beg their parent for food - watching anxiously as they would crawl along the bottom of the stream looking for food:



The American Dipper is the only bird of the Cinclidae family in North America - in Asia and Europe there are about 4 other species. They used to go by the much more poetic name of "Water Ouzel," but dipper seems to be the nom-du-jour.