The End of the 2013 Herp Season Approach-eth....but there are still TURTLES!

The beginning of the semester sort of stinks.....

The collision of the field season and the school season means there isn't a free second.  We have three projects still in the active data-collection phase, which we are trying to coordinate schedules for....and everyone has class (students) or teaching/grading (me).

All of that will change sooner than we think, though.  We are in that time of the year when weather becomes highly variable.  Last week, for example, we had a high of 90 deg. F on Tuesday, and a high of 63 deg F on Friday.  This week we had two days in the mid-80s, while today it was in the mid-60s over the weekend.

That means Fall is coming, which also means the cold-blooded critters will be going down for the winter very soon.

So....thought I'd share some late-season "herpstuff".  Mostly a random conglomeration of neat things seen over the last few weeks.

Our 200-level Field Methods in Ecology class had their annual day of turtle trapping and marking (see here for last year's haul).  This year was another great one.  By luck, we got to take advantage of the last few good days left for trapping before the turtles started to focus on hibernation (and, thus, aren't as attracted to bait). 

We set traps out for two days straight.  Day 1 yielded some nice little Painted Turtles (Chrysemys picta)........

........ and of course some nice Common (northern) Snapping Turtles (Chelydra serpentina).

 

 

On Day 2, however, our traps were nearly exploding with turtles! 

A ton more Paints....

.....no Snaps (suprisingly)...BUT...a much rarer find: a Blanding's Turtle! (Emydoidea blandingii). 

Photo courtesy of T. Gotrik

In three years of trapping this location, we've never caught a Blanding's Turtle before.....

We also trap the nearby creek...and this year got another first: a Spiny Softshell Turtle (Apolone spinifera).

Photo courtesy of T. Gotrik

The students were pretty excited (and so was I).  In the end, we caught 26 Paints, 2 Snaps, 1 Blanding's Turtle and 1 Spiny Softshell.

Enough turtles for everybody to be able hold at least one in a group photo!

Photo courtesy of T. Gotrik

The students worked hard and enjoyed themselves....even when hip waders weren't quite enough to keep them dry....

OH...and it's the time of year when salamanders are migrating from their summer ponds, to where they will spend the winter.

As we found out when checking our drift fences recently.....

Tiger Salamanders (Ambystoma tigrinum).
Photo courtesy of N. Rudolph



Blue-spotted Salamanders (Ambystoma laterale)
Photo courtesy of N. Rudolph

The Beaten Bear, Poor Ol' Slim, and a Size-13 Snapper!

A random conglomeration of stuff from recent happenings during summer field work.  There's been alot of things going on.  There's so much to share that I can't fit it into a blog post in any type of logical order.

We've been running the drift fences surveys since the beginning of May, which has resulted in many excellent captures (one of which is below).

Yet, we also see cool stuff while we are walking out to our fences.  For example, there's an old gnarled tree that overhangs the creek near one of our fences.  Every day there are multiple Northern Watersnakes (Nerodia sipedon) hanging on the branches catching some rays.


Photo by N. Rudolph

They never really appreciate my grabbing them...and the result is usually a bit of drawn blood (as you can see on my hand below).  The bite looks much worse than it is, however.  They are non-venomous, and their teeth feel like nothing more than tiny pin-pricks.

Photo by N. Rudolph

The poor watersnake frequently suffers greatly at the hands of humans.  When the average person sees a snake near the water with a body pattern that is NOT similar to a gartersnake, they often think: "cottonmouth!" or "water moccasin!" and the snake is killed.  There are NO cottonmouths or moccasins in the upper Midwest, unless one inlcudes southern Illinois (and I don't think they do?). 

Amazingly, folks often argue with me about this!  Here are example responses I get to telling them it wasn't a cottonmouth they saw: "Nope, I saw a cottonmouth on that canoe trip.  There's nothing else it could have been." ...or..... "Well, I'm pretty sure that it was a moccasin that swam along the bank next to me while I was fishing." 

But, let me re-iterate: the snakes in my hand above are NOT cottonmouths/moccasins!  We do not have said venomous species 'round these parts.

BUT....none of this is even the point of my current post!  So, I'll get on with it....

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The Beaten Bear:

Below is an impressive and "battle worn" Black Bear (Ursus americanus) that the wolf researchers captured on one of the camera traps.

Take a look at the lip on the left side of his face (right at the beginning of the clip).  It looks to be torn....and his ears have clearly seen better days.  He must be a wily sort to have avoided the hunters all these years.

I wonder whom he had a run-in with to have acquired all of that damage?  Males compete for breeding rights, and perhaps his

I wonder whom he had a run-in with to have acquired all of that damage?  Males compete for breeding opportunities and perhaps this was from another male Black Bear?  They certainly run afoul of wolves, which may be particularly problematic when wolves have pups in the den. Hunting dogs are another possibility, I suppose.  But all of that damage is to the face and head.  Is this type of damage typical of such encounters?  Could the torn up ears be where identifying ear tags were yanked out?

I love a natural history mystery!
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Poor Ol' Slim:

Poor Slim.....the unfortunate Short-tailed Weasel (Mustela erminea) that I found dead on the road not far from my house.  I caught a glimpse of it while my daughter and I were driving home one day....and I thought it looked like a weasel, so we had to turn around so I could pull over and snap a picture (it wasn't in good enough condition to turn into much of a specimen).

Slim is either a juvenile Long-Tailed Weasel (Mustela frenata) or an adult Short-Tailed Weasel (M. erminea), based on the size and the black tip on the tail.  The other weasel in our state...the Least Weasel (M. nivalis) has no black tail tip. 

Adult Long-Tailed Weasels attain average sizes (13-16 inches) and this individual is not that large.  Yet, this could be a juvenile Long-tailed Weasel....which would also make sense, seeing that the Long-Tailed Weasel is more common in the southern part of the state (where I am located) than the Short-tailed.  But the tail on this specimen looks to be particularly short. 

Hmmm.....

Another good mystery!

Fortunately, the summer hasn't been only negative encounters with weasels.  Below are pictures of a little Least Weasel my students and I captured in a drift fence a few weeks ago (note the lack of black-tip on the tail).  The drift fences are primarily for amphibians and reptiles, but we get just as many small mammals.  In fact, the hidden secret of this herpetological technique: it's probably just as effective and less work day-in and day-out for small mammals as Sherman Traps.  Although the fence takes alot of effort to install initially, there isn't the hassle of setting and re-baiting traps all the time.  Plus, we get many intectivores (Shrews) and the occassional weasel, which Sherman Traps aren't effective at catching.

I imagine these little carnivores are attracted to the fence due to the smell of vole, which we catch many of.  According to King and Powell (2007, The Natural History of Weasels and Stoats, Oxford University Press) the Least Weasel is the weasel that is the most narrow in its dietary preferences....eating almost exclusively on rodents and then focused primarily on voles (especially Microtus sp.).  I've caught Least Weasels on several occassions in drift fences in years past, so I wasn't totally shocked.  This is also not my first weasel post in the last year (see here).

But that doesn't mean I wasn't incredibly excited to see one!  The Least Weasel, in particular, is rare 'round here....so it was quite a treat!  Holding still is not the strong-suit of these frenetic little carnivores....so forgive the blurry pics (these were the best of about 30 attempts).

Photo by N. Rudolph

Photo by K. Rutzen

 

Photo by K. Rutzen

I love me some Mustelids.....

A Size-13 Snapper:

Mid-summer is when I often do most of my turtle trapping.  As part of survey work this summer, I've been trapping in wetlands with the hopes of catching some Blanding's Turtles (Emydoidea blandingii).  I've caught a few (as you can see)....

We also catch many, many Painted Turtles (Chrysemys picta)....


Photo by N. Rudolph

Frequently these are given a unique mark.  This is done by notching the edge of their shells in a certain order with a file or dremel tool so that we can identify the turtles in the future.

Photo by N. Rudolph

But, in addition to the Painted Turtles, I almost always also catch Northern Snapping Turtles (Chelydra serpentina).  In fact, I would not be shocked if just about every water body in the state (from tiny pond to giant river) has at least one snapper lurking in the depths.  The Northern Snapping Turtle (previously called the "Common" Snapping Turtle) rarely leaves the water.  It doesn't usually sit on logs and bask in the sun, like many other pond turtles.  It mostly remains unseen in the mud and muck on the murky bottom.  The females are seen more frequently on land during the nesting season, when they must traverse the dangers of an over-land movement to lay their eggs.  It's during these times that snappers must frequently head out into vehicular traffic.  Poor snappers.  Especially considering that people apparently swerve to hit turtles crossing roads.

Regardless, the Northern Snapping Turtle is one of my favorite turtles: ornery, cantakerous, dirty, smelly, mean-looking.....everything I like in a critter :)

Photo by N. Rudolph

This summer, we've been lucky enough to catch many snapping turtles, like the individuals above.  At one particular pond, I caught at least five individual snappers in a single night that had carapaces (upper shells) which ranged from 8 to 12.5 inches.  The one below is a prime example.....

 

But that one pictured above wasn't even the biggest captured this summer.

That prize belongs to the individual below.  To put this into perspective, the boot on my chest-waders in this photo is a size 13.

It would be nice if more snapping turtles could make it to this size (or bigger). 

I guess we have to start by getting folks to restrain from hitting them on purpose (I can't believe I had to actually say that). 

Next we can try and come up with ways in which the average person can avoid hitting them on accident.

-sigh-


Skulls and Skull Cleaning: Part I

I find skulls fascinating.

First of all, so much can be learned from their close inspection.  This includes the likely diet of the organism in-question (at least in a general sense)...prominant muscle attachment areas, which provide information on life history....and important information about sensory function and brain-size (just to name a few).

I'm obviously not alone in this.  Just about anyone I know who is interested in vertebrate ecology (and obviously morphology) is also a "skull-o-phile".

Anyhoo....figured the best way to share my love of skulls with you all was to dig into the university's specimen collection and show you some examples.

We can start with one of my favorite groups, the reptiles.....

Reptiles:

Look at the teeth of a crocodilian (in this case, a small Black Caiman; Melanosuchus niger).

Very impressive chompers!  Incredibly sharp...well-suited for grabbing prey and holding it fast.  This is perfect for an ambush predator that lunges out of the water to grab a critter that's come down for a sip.

BUT...as impressive as these teeth are...they are alittle "one-dimensional".  In other words, they are mostly the same in shape (large, sharp and conical), because they all serve a similar purpose: grabbing, holding, tearing prey.

Here's another interesting example....the turtle.  Although also a reptile, the turtle's mouth is not filled with teeth.  Rather than teeth, turtles have flat, sharp, cutting plates....that resemble a sort of "beak".  These cutting plates have are sheath made of keratin (which is protein-based and similar to our fingernails) that is over the bones of the jaw.  The example below is the skull of a Snapping Turtle (Chelydra serpentina; previously known as the Common Snapping Turtle).

This lack of teeth (among other features) differentiates turtles from the rest of the reptiles.  In fact, they are in their own Order (Testudines).  Note: other well-known reptiles belong to the Orders Squamata (lizards & snakes), and Crocodilia (crocodilians).

Also, check out the large projection of bone coming off the back of the skull (appearing similar to a crest).  This bone, called a supraoccipital bone, creates a large area for muscle attachment....these muscles are involved in bringing those jaws closed with the force that snapping turtles are renowned for.  The muscles also play an important role in pulling the head into the shell and keeping it there, where it is protected.

Mammals:

Now let's move on to some mammals....

Mammal teeth, unlike reptile teeth, are "differentiated".  In other words, they are not all uniform in shape, size and general purpose.  Think of your own teeth.....feel around in your mouth with your tongue...it's fun!.  As mammals, we have incisors, pre-molars and molars that all differ in their shape and general use.

These teeth are also modified among the different groups of mammals and reflect their various feeding styles/preferences.

Herbivores:

First, a herbivore.....the White-tailed Deer (Odocoileus virginianus)

Artiodactyl skulls are easy to identify, as most  lack upper incisors.  They also have teeth that are very well designed for thoroughly masticating (chewing) tough food: vegetation.

Check out these grinders!  They are broad and sharply ridged so that when used appropriately can grind the heck out of even very tough vegetation....in an effort to break it down as much as possible before passing it to the digestive system.

Now compare the WTD to a herbivore specialized for chewing: a rodent.  In this case, one of my favorite rodents: the North American Beaver (Castor canadensis). Rodents have large incisors, immediately followed by a large gap, or arch with no teeth, called a diastema.

Rodents have the broad, flat and ridged pre-molars/molars, for grinding vegetation, that one would expect of a herbivore....

But, as you can see in the top picture of the Beaver above.....they also have those large incisors shaped like chisels.....which is exactly what they are used for.  Rodents can use those large chisels to chew with great effect.  In the case of the Beaver...as you all know.....they can even chew through tree trunks!  Other groups (such as Lagomorphs like rabbits) also have a large gap between chisel-like incisors and molars...but Rodent incisors are different than those of bunnies.  The action of chewing actually helps sharpen rodent incisors, due to the thick layer of enamel on the front relative to the back of these teeth.  As they rub together....this actually results in the incisors sharpening, which is not the same for lagomorph teeth.

Carnivores:

Compare the teeth of herbivores to that of a strict carnivore: the domestic cat (Felis catus).

Felids have teeth that are very effective at slicing through meat.  See the narrow molars and premolars above.  These are very sharp and come perfectly together with similarly narrow/sharp molars on the lower jaw to create teeth that behave like meat scissors, called the carnassials. 

Note also the large round/bulbous structures at the back of the head (the left one is broken on this specimen)....these are the auditory bullae, and they house the inner ear, including the tiny ear bones (or ossicles): incus, malleus, stapes.  Large auditory bullae are often found in mammals with acute hearing.

Canids have carnassials as well.  However, many Canids will eat more than just the soft bits of flesh from their prey....and some frequently crack into larger bones, etc.  As a result, the molars behind the carnassials on a Canid are more broad and flat for crushing. 

We can see this must be put to good use by wolves (Canis lupus; below), as their molars behind the carnassials have fairly broad surfaces for really crunching up bone.  Interestingly, according to Paquet and Carbyn (2003), wolf molars are broad...but less broad than the Coyote (Canis latrans), which eats more vegetation that requirs broader molars for mastication.

This is even more interesting when we compare the Wolf's teeth to those of the dainty little Gray Fox (Urocyon cinereoargenteus). According to Cypher (2003), these are often used for "crushing flesh and vegetable foods", which are less difficult to mash-up than bone.

It's also pretty cool to compare the areas for muscle attachment associated with the jaws of these two species.  The Wolf has a broad zygomatic arch (cheekbone)....see view from the bottom, looking up through the Wolf's zygomatic arches.  Also...note again the large bulbous auditory bullae....

The zygomatic arch helps protect the animal's eyes, but also makes room for large, strong jaw muscles.  These muscles attach to the mandible (lower jaw)....run underneath the zygomatic arch...and attach to the sagittal crest.  This is a bony projection that runs along the mid-line of the top of the cranium.  The large sagittal crest on the wolf represents a big surface area for the attachment of large muscles that power the jaw...and help generate the force to use those molars for crunching through bone.

We can again compare the wolf to the rather diminutive Gray Fox and see that the fox has obvious temporal ridges for muscle attachment, but the sagittal crest is (proportionally) much smaller than in the wolf. 

The Gray fox is not so much of a bone cracker.....or at least not to the extent of the Wolf.

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I also can't resist but to compare some of these structures to extinct critters....in this case, Felids.  There are a pair of outstanding books that I recommend to anyone interested in skeletal morphology.  Wang and Tedford's Dogs: their fossil relatives and evolutionary history, and Turner and Anton's The Big Cats and Their Fossil Relatives.  Fun to read and full of great drawings of the extinct critters.  I wish I had the rights to include some of the illustrations from these books in my blog, because they perfectly detail what I'm about the describe.

Anyways, if we compare the width of a modern African Lion's (Panthera leo) skull to that of an extinct sabertooth cat, the concepts of large jaw muscles, the zygomatic arch, and feeding strategies can be brought together.

Modern lions have wide skulls due to wide zygomatic arches, and relatively short snouts compared to sabertoothed cats, such as Smilodon sp..  The wide arches accommodate large muscles that produce considerable bite force and strength.  This bite force is employed when lions kill their prey.  Lions can bring down large prey by clamping their jaws around the throat of the animal...or around the end of their muzzle....and suffocating them.  The captured animal will surely struggle when in the lion's jaws, and holding them requires the lions have considerable jaw strength (i.e. large jaw muscles and, thus, wide zygomatic arches to allow the jaw muscles to pass underneath).

The sabertooth cats...however....probably did not use such a hunting/killing strategy.  Rather, it's speculated that they held their prey down with their strong fore limbs....and once the prey was immobilized.....unleashed their famous teeth to sever the major veins/arteries and trachea in the throat to quickly kill the animal.  Thus, sabertooth cats did not require jaw muscles that were as strong as modern lions, because they used a different strategy to kill their prey.  Hence the reason why they have relatively narrow skulls and long muzzles compared to modern lions.  Sabertooth cats did, however, need strong fore limbs to immobilize their prey, which are proportionally larger than modern lions.

Wow!

Skulls are fun to talk about!  But....all of this has distracted me from the fact that I STILL haven't talked about how to clean them. 

Well....we'll get to that next time!

Literature Cited:

Cypher, B.L. 2003. Foxes (Vulpes species, Urocyon species, and Alopex lagopus). In Wild Mammals of North America: biology, management and conservation (second edition). Feldhamer, Thompson, Chapman (eds.).  Johns Hopkins University Press.

Paquet, P.C., and L. N. Carbyn. 2003. Gray Wolf (Canis lupus and allies). In Wild Mammals of North America: biology, management and conservation (second edition). Feldhamer, Thompson, Chapman (eds.).  Johns Hopkins University Press.

Field Ecology Methods Week 2 (2012): Reptiles

After a week of invertebrates and Limnological techniques, the students spent some time learning how to conduct some standard surveys for reptiles.

First, we checked the existing artificial cover objects on-site for snakes....

This resulted in only TWO juvenile Gartersnakes (likely born this year).  But it was unseasonably warm on the day we checked the boards (upper 80's)....probably too warm for snakes.

The students then worked to measure out additions to our existing coverboard grid. 

Few things make me happier than to see all 18 of these students working hard in the field and no one standing idle.

Let's face it....field work can be grueling (especially in the warm conditions we had while deploying the boards).  But, this gives the students a small taste of less than ideal field conditions that one might face as a field ecologist.  It's not all catching Cougars and Narwhals every second (or as a colleague here says...there's not a "gorilla behind every tree").

After the artificial cover objects were laid, we moved over to the creek and deployed some hoop traps for turtles.

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The traps sat for a night, and a small group of volunteers came out with me the next morning to check and re-bait the traps.

Thankfully, we had more luck with turtles than with snakes.

Two large adult Snapping Turtles (Chelydra serpentina).....

Five cute little Painted Turtles (Chrysemys picta).......

We took our morphological measurments, such as carapace (or upper shell) length....

Then we released the turtles back into the stream.
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The next day it was back to check the traps again, and this time the entire class was present.

...and once again, we had good fortune!

Day 2 yielded 14 painted turtles and one little snapper....a good haul!

Once again, appropriate morphological measurments were made....the turtles were given a permanent mark....and released back into the creek. 

Hopefully, we'll see some of them again in the spring!

For more information on standard survey techniques for reptiles, see this excellent new book:

McDiarmid, R.W., et al. 2012 Reptile Biodiversity: standard methods for inventory and monitoring. University of California Press. Berkeley.

The following book is also a good introduction to standard reptile survey methods.  Unfortunately, it's out-of-print, but you can still get it from libraries or through interlibrary loan.

Karns, D.R. 1986. Field Herpetology: methods for the study of amphibians and reptiles in Minnesota. Occassional Paper 18 of the James Ford Bell Museum of Natural History, University of Minnesota.