Tuesday, November 22, 2011

A Day at the Racetrack

Each year, I make it a goal to narrow down my state list of herps I've yet to see in the field. One species was of particular interest as its ecology & presence in Michigan are not well understood. That species is the Prairie Racerunner, one of only two lizard species which occur in the state. The Prairie Racerunner is a diurnal species which prefers scrubby areas and sandy substrate for burrowing. In Michigan, the racerunner inhabits one small sand prairie which sparse vegetative cover including grasses, sedges, and prickly pear cactus. Like its name implies, the racerunner is extremely fast and agile. This makes it difficult to apprehend by predators or by the human hand. Because of its extremely limited distribution in Michigan, the Prairie Racerunner is listed as a Threatened species. In early September, I coordinated with a researcher who is working on this population of lizards and was able to join him for an afternoon of observation. It didn't take long to get my first look at one, as I spotted this sub-adult in the process of excavating a burrow.

 Prairie Racerunner - Aspidoscelis sexlineatus viridis

These lizards are quite striking, with adult males obtaining a vibrant green coloration on the head and neck. The researcher explained to me that this species often excavates temporary burrows for cover during the night hours and from inclement weather and predators. We watched this individual for fifteen minutes or so, constantly entering the two entrances to the burrow and kicking out sand with his back feet. I was able to slowly move close enough to get this shot as he had just emerged from the burrow. The researcher explained that they try not to handle the animals by hand as much as possible, and even so it is extremely difficult to capture one by hand. The researcher had to take off but allowed me to stick around and shoot as many photos as I wanted. I noticed movement all around me within the sand prairie and realized they were all racerunners. I decided to stand still and wait for one to come within distance to fire a few shots as quickly as I could.

 Prairie Racerunner - Aspidoscelis sexlineatus viridis

Most of the active animals were juveniles like the one photoed above. They exhibit a characteristic light blue tail which can be lost and regrown, similar to the Five-lined Skink. The racerunners rarely stopped moving for more than a second or two, and it took a lot of patience to get the mediocre shots that I did. I watched one adult which was clearly foraging, as it followed a grasshopper into a small shrub and apprehended it. I tried to snap a shot of the order but the lizard moved to fast for me to get a clear shot. I noticed a beautiful adult male later on which escaped before I could fire a photo, but I did get the chance to get within range of this adult female for the best shots I took all day.

 Prairie Racerunner - Aspidoscelis sexlineatus viridis

Here you can see the characteristic black and yellow striped on the dorsum of the racerunner. Juveniles lose the blue coloration of their tails as they age. Racerunners prefer hot, dry conditions and are only active during the warmest parts of the year in Michigan, usually between May and August. The Michigan population is disjunct from the racerunners recognized range, and it is unclear whether or not it is a relict native population or if it is introduced. Continuing research is trying to determine this issue and to better understand the racerunner's ecology in Michigan in order to better manage it in the future.

I ended up seeing close to 50 individuals on this day at best estimate, most of which were a fleeting glimpse like the photo above. I'd like to thank the researcher for allowing me to observe these animals for the afternoon, it's a species I've wanted to see for a long time. Hopefully, the future will be bright for the Prairie Racerunner in Michigan.

Tuesday, November 15, 2011

The Sculptured Turtle: Observations in Michigan & New Jersey

The name Glyptemys insculpta literally translates into "sculptured turtle." There's no better way to describe the carapace of the Wood Turtle, a Species of Special Concern here in Michigan. This species has suffered significant declines across its range due to illegal collection, habitat loss, nest predation, and road mortality. Their striking appearance, charismatic personality, and rarity make them highly sought after in the herp community. It is a wide ranging, northern species that is found as far west as Wisconsin and Minnesota, north to Canada, and as far east as Maine. The appearance and habitat preferences of this species varies greatly across its range, and after working with them all summer I decided to dive into these differences to see what I could find out.

Wood Turtle, Glyptemys insculpta, adult male, Michigan

Wood Turtle, Glyptemys insculpta, adult female, New Jersey

Wood Turtle, Glyptemys insculpta, adult male, Michigan

Wood Turtle, Glyptemys insculpta, adult male, New Jersey

The most noticeable difference in the turtles above is coloration. Wood Turtles from the western extent of their range (Michigan, Wisconsin, & Minnesota), are often much brighter in coloration that Wood Turtles from the eastern extent of their range (northeastern United States). The Wood Turtle has been affectionately referred to as "old red legs." Specimens from the northeast exhibit this characteristic, ranging from deep red to a more orange-red. Most of the turtles I worked with this past summer in New Jersey exhibited a red-orange coloration. Specimens from the western portion of their range exhibit yellow to yellowish-orange coloration, with younger turtles being brighter yellow. Some older males approach a deeper orange color, but nothing close to individuals from the eastern part of their range.

Wood Turtle, Glyptemys insculpta, adult male, Michigan

Wood Turtle, Glyptemys insculpta, adult male, New Jersey

Another very prominent difference between eastern & western Wood Turtles is the abundance of carapace markings. Most Michigan individuals I've encountered exhibit radiating yellow markings on the carapace, usually with high frequency. The adult male from Michigan pictured above is a particularly striking individual, most individuals are not as striking. The adult male from New Jersey has almost no visible radiating lines, a duller carapace seems to be more characteristic of populations from the northeastern United States. Some individuals did exhibit yellowish-orange markings on the carapace, but not the level exhibited by individuals I've encountered in Michigan at various sites. So why so much variation among the eastern and western extents of the range? To answer this question, the evolutionary history of this species has to be examined.

Dispersal patterns of Glyptemys insculpta from a southern refugia (Amato et al., 2008)

A great study done on the phylogeography of Wood Turtles was published back in 2008 in Molecular Ecology, and can be read here. Phylogenetic analyses were used to examine differences in mtDNA in Wood Turtles across its geographic range. These analyses suggested a large genetic bottleneck occured during the late Pleistocene glacial period, followed by a rapid northward expansion from a common southern refugia. Subsequent western expansion from the northeast clade occured, creating the two genetic clades in Glyptemys insculpta which are recognized today (Amato et al., 2008). These two clades have been separated for a long time and thus have resulted in slight phenotypic variation between the eastern & western portions of the turtle's distribution. Beyond phenotypic variation, wood turtles occur in varying habitats and stream types between the eastern and western portions of the range.

Northern Michigan Steam, May 2010

Wood Turtle, Glyptemys insculpta, adult male, Northern Michigan River

New Jersey Stream, May 2011

Wood Turtle, Glyptemys insculpta, adult male, New Jersey stream

Woods from Michigan, Wisconsin, and Minnesota tend to be found in medium sized rivers with sandy substrate with ample surrounding forest. They occasionally wander into smaller streams and tributaries of larger streams. Wood turtles from the northeast may also occur in streams of this type but are more often associated with streams that have a gravel or rocky substrate. This is due to the differences in elevation and geology between the eastern & western portions of the range. Wood turtles from the northeast are often found in mountain streams within the Appalachians and the surrounding forests and meadow which are adjacent to them. After tracking wood turtles in New Jersey this summer, I was able to experience their movement patterns throughout the course of the season. Most of the males stayed within the stream corridor throughout the course of the summer, and were rarely found more than a few meters away from the stream itself, with males wandering as far as twenty meters or so from the stream in one or two cases (both of these cases occured during breeding season). Females often wandered great distances from the stream even after nesting, in fact most were found away from the stream the entire season. In Michigan, most of the turtles I've seen while kayaking have been males, with the exception of a few females being found very early or very late in the season. Without the aid of radio telemetry, I cannot voice the movement patterns of males and females in Michigan but can guess that it is similar to what I observed in New Jersey. 

Wood Turtle, Glyptemys insculpta, adult male, Michigan

Despite their differences in appearance and habitat, wood turtles from across their range are a charismatic and intelligent turtle species that needs to be preserved. Managing current habitat, head starting juveniles, nest protection, and turtle crossing signs are all protocols that can be used to ensure this species persists in the future.

Tuesday, November 8, 2011

Wild & Wonderful West Virginia

"Wild and Wonderful." I read this statement as I crossed from Maryland into West Virginia on my way to meet a fellow herper. I had driven through West Virginia several times but had never actually gotten out to explore it. Today, I would be in search of some coal country horridus.

Our first stop was a powerline cut along a ridge that had plenty of rock outcrops, fallen timber, and other hiding places for our species of interest.

The steep ascent yielded many rocks to flip, but only yielded a lone ringneck snake by the time we reached the top of the slope. My partner assured me than he had seen several rattlesnakes and copperheads earlier in the year and that we just needed to be persistent. As we spread out, I stepped over a fallen tree and noticed this a few feet away.
Timber Rattlesnake - Crotalus horridus

This was the first example of the "dark" phase snakes that inhabit much of the northeastern United States. This snake coiled in a patch of greenbrier (Smilax sp.) and sat contently for photos. I was pretty stoked to have had success at our first stop, so we packed up our gear and headed on to our next location. Our next stop was completely different than our first location. Unlike the steep, rocky slope of the powerline cut, this site was a large upland forest area atop a ridge. There were several openings in the forest with fallen trees and only a few scattered rocky outcrops. It wasn't long before we laid our eyes on this monster.

Timber Rattlesnake - Crotalus horridus

This was by far the largest rattlesnake I've ever encountered in the field, well over the four foot range and brilliantly marked. Timber rattlesnakes do not get much larger than this, especially in the northern portion of their range. To reach this size, you need a lot of years and an abundant prey source. What was equally impressive about this snake was its string of rattles, totaling thirteen segments. We spent a good amount of time photographing and enjoying this specimen, a truly formidable snake to meet in the field.

We eventually parted ways and continued to explore the area. Just a few short minutes later, another timber made an appearance in awesome fashion.

This timber rattlesnake was in textbook ambush position. Using their sense of smell, timber rattlesnakes will follow the scent trails of small rodents to locations such as fallen trees or logs. Small rodents such as chipmunks and squirrels use regular travel routes. Rattlesnakes are able to detect these trails and position themselves to intercept rodents on these travel routes. Usually, the snake will coil along a fallen tree or log with its head resting on the edge. This allows the snake to sense the vibration of an incoming rodent and thus prepare itself for a lethal strike. For more information on timber rattlesnakes foraging behavior, read this study done by H.K. Reinert at. JSTOR. I've always wanted to see a timber in ambush position, and this was certainly a memorable field moment. We did not disturb the snake and continued on in exploring the area andf before long we turned up this duo.

Copperheads are some of the best examples of how effective comouflage can be. These two were found near a large rock outcrop where the sun was hitting. Unlike the timber rattlesnake, copperheads come into contact with people much more often due to their numbers. In some areas, copperheads may be the most common snake species and can be easily missed by an unaware hiker.

 Northern Copperhead - Agkistrodon contortrix mokasen

Copperheads are always a treat for me, especially because I don't wander into their range terribly often. We managed to pick up one more timber rattlesnake, an in-shed individual found under a large rock bring our totals on the day to five timbers and two copperheads. It was a quick day, but it was enough to leave a lasting impression on me. West Virginia is a beautiful state that harbors many cool herp species, especially the salamanders. I'm sure I will be back next year to see more of the state that truly is wild and wonderful.