April 2019 Natural Mystery: Test Prep Edition

posted Apr 9, 2019, 7:41 AM by Jonathan Poppele   [ updated Apr 9, 2019, 10:08 AM ]

Support the Newsletter on Patreon

If you enjoy these natural mysteries, please consider supporting the Minnesota Wildlife Tracking Project newsletter on Patreon.

March 2019 Natural Mystery Answered

posted Apr 8, 2019, 11:19 AM by Jonathan Poppele   [ updated Apr 18, 2019, 10:54 AM ]

Our March natural mystery was a tricky one, as small bird tracks usually are. In this case, it is possible to trim down the list of possible birds quite a bit based on when and where this photo was taken—in January in an urban area of St. Paul, MN. By making a list of possible birds, and comparing that to the size ranges in the literature, we are left with just a few candidates…

I'll start out by noting that this is an unverified track photo, so we may never be able to be 100% certain on the ID, but let's see how close we can get.

Kirsten Welge drew on her experience living in St. Paul to create a list of the most likely candidates: Northern Cardinal, American Robin, Black-Capped Chickadee, White-Breasted Nuthatch, American Crow, and Blue Jay. She measured the mystery track at 1 5/8” long, eliminated the corvids, robin and chickadee based on size, then selected the Northern Cardinal over the White-Breasted Nuthatch based on morphology. As she notes, “nuthatch shows a very skinny foot and a strong claw register – not a match for our mystery track.“

This is a good process, but there are a few other birds we need to consider before we conclude that these are cardinal tracks. Juncos, finches and even a few sparrows also frequent St. Paul in January. So let's take a further look at a more extensive list of candidates.

If we look on eBird for sightings in Ramsey County in January, we can put together a list of about 15 species of smaller passerines. Using size data from Elbroch & Marks Bird Tracks & Sign we can pare the list down even farther:

In our photo, the right track in each pair appears to be 1 1/2" long. Interestingly, the left track in each pair appears longer--about 1 11/16". Perhaps this is because of the way that foot drags the snow in the hopping gait, or perhaps the left foot is splaying more. In any case, we can use the range of 1 1/2” to 1 11/16” as a starting point.

Based on Elbroch's measurements, the tracks are too large to be a wren, goldfinch, house sparrow or chickadee. Though there are no data in the literature, comparing body to similar species we can likely eliminate American tree sparrow and pine siskin, both of which would also be unusual to see on a sidewalk in an urban area of St. Paul. The tracks are too small to be robin, starling, or blue jay.

That leaves house finch, purple finch, northern cardinal, dark-eyed junco, white-breasted nuthatch and white-throated sparrow as possibilities.

As Kirsten notes above, we can eliminate white-breasted nuthatch based on morphology.

While there is no published data for house finch or purple finch track sizes, we can make some guesses based on body size of these birds and comparing them to their slightly smaller cousin, the goldfinch. Assuming that these birds are proportional, we can compare various linear measurements such as body length, wingspan, and the cube root of body weight. I used data from the Cornell Lab's All About Birds website to do this, and found that house finch can be up to 10% larger than goldfinch and purple finch can be as much as 20% larger. This suggests that the tracks of these slightly larger finches would still be under 1 3/8”, making them too small for our mystery.

The tracks seem a little on the large side for any of our remaining candidates, but if we allow for the tracks appearing a bit large because of the snow, we can consider junco, white-throated sparrow and cardinal.

Dark-eyed junco tracks show slender toes and, of particular note, a slender hallux. These images appear to show plumper toe pads, particularly in the hallux, compared to junco. Elbroch also lists the hopping strides for juncos as 1-6”, while we were told that our trail showed hopping strides of 7-10”

White-throated sparrow also have a more slender hallux than cardinals, but the difference is less pronounced. Here again, Elbroch lists the hopping stride as 6” or less, where our bird was consistently hopping over 7”. We are also on the very edge of white-throated sparrow winter range, and they are a much less common sight in these urban areas compared to cardinals.

This leaves us with the cardinal as the last bird standing. The hopping stride fits Elbroch's data, the track size appears a tiny bit on the large side, but seems reasonable, and the morphology seems the best fit. Like finches, cardinals have a fatter hallux than sparrows and juncos do--particularly the proximal pad--a feature we see in these tracks. Although it isn't definitive, the clues we have available most strongly suggest that these are the tracks of a Northern Cardinal.

An Interesting Note: Elbroch lists the size of cardinal tracks as 1 1/4" - 1 9/16", which is still smaller than the measurement for the left side tracks--but he notes that his size range comes from a small data pool. If we the same calculations we used for the house finch and purple finch suggests a maximum track size for cardinals of at least 1 9/16" (the same as Elbroch's data pool), and possibly as much as 1 11/16" (the length I measure for the left track in this photo). But cardinals have a different enough body shape from goldfinch that I don't think this is more than a curiosity.

Support the Newsletter on Patreon

If you enjoy these natural mysteries, please consider supporting the Minnesota Wildlife Tracking Project newsletter on Patreon.

March 2019 Natural Mystery

posted Mar 6, 2019, 12:01 PM by Jonathan Poppele   [ updated Mar 6, 2019, 12:03 PM ]

February 2019 Natural Mystery Answered

posted Mar 6, 2019, 10:32 AM by Jonathan Poppele   [ updated Mar 13, 2019, 11:05 AM ]

Our February Natural Mystery proved challenging--but two of you met the challenge. Congratulations to Anne Marie Meegan & Rob Grunewald for successfully identifying this common, yet surprisingly unfamiliar track. We are so used to seeing the full track pattern of this and related species, we may not recognize these two prints in isolation. Two prints--but not a double register.

These are, as Ann Marie put simply, "the front feet of a Lagomorph." Specifically, an Eastern Cottontail. Rob Grunewald identified the species and offered these additional comments:

"In a Cottontail's bound, the typical gait for this species, the front prints sometimes land next to each other, as pictured here. The animal is moving toward the top of the picture. You can see the entry at the bottom of the print where the snow is disturbed, the exit has a sharper edge."

The fur on the bottoms of rabbit feet tends to obscure the details of the foot morphology, but if you look closely, you can make out some toe pads, and even a couple of claw marks on the leading edge of the two tracks.

Thanks to everyone who tried their hand at this mystery--and congratulations again to Anne and Rob.

A Correction

Last month's Natural Mystery were the tracks of a flying squirrel. When I posted the mystery, I wrote that the photo came from Cedar Creek Ecosystem Science Reserve, in southern Minnesota. I was mistaken about this. The photo that I posted was actually taken in far Northern Minnesota, on the edge of the Boundary Waters Canoe Area. According to the range information I have been able to find, this means the tracks must be those of a Northern Flying Squirrel (Glaucomys sabrinus). The size of the tracks and the trail fit within the published ranges for both Northern and Southern Flying Squirrels, and the hopping gait is reported to be much more common for Southern Flying Squirrels. It appears, however, that it is not diagnostic. In truth, where size overlaps, I cannot find any features of the tracks or the trails that are diagnostic between these two species. Where their ranges overlap, it may only be possible to distinguish the tracks as Flying Squirrel.

My apologies for the mistake--and a delayed congratulations to Bren White, who was the only person (including me) to correctly identify this photo as the tracks of a Northern Flying Squirrel.

If you enjoy these natural mysteries, consider becoming a patron. Your sponsorship supports the Minnesota Wildlife Tracking Project newsletter, including these Natural Mystery blogs.

February 2019 Natural Mystery

posted Feb 6, 2019, 3:37 PM by The Center for Mind-Body Oneness   [ updated Feb 6, 2019, 3:37 PM ]

January 2019 Natural Mystery Answered

posted Feb 6, 2019, 3:29 PM by The Center for Mind-Body Oneness   [ updated Feb 8, 2019, 10:54 AM by Jonathan Poppele ]

Last month's natural mystery generated lots of responses. Everyone who wrote in identified these as squirrel tracks, and they are indeed the tracks of a squirrel. But we had a few different guesses about which squirrel left these prints. Congratulations to Kirsten Welge, Anne Marie Meegan and R Scott Semmens who correctly identified the species. These are the tracks of a southern flying squirrel.

Flying squirrels are both the most nocturnal members of the squirrel family, and the most arboreal. They can be quite illusive, even where they are common, and it is rare to see their tracks except in snow. The size and gait are two of the best clues, but there are a few morphological details that can help us distinguish these tracks as well.

Kirsten Welge starts us off with these observations. Some point to rodent or squirrel generally, while others are more specific to flying squirrels and southern flying squirrel:

"The front tracks show four toes, symmetrically arranged. Hind tracks show five toes, arranged in a 1-3-1 pattern. The metatarsals register as a thin, curved line.
The gait looks like a hop, with hinds behind the fronts.
Habitat is also a match – particularly with plenty of woodpecker nearby to create holes in punky wood for nesting and latrine sites."

Anne Marie Meegan also noted the classic rodent characteristics in the number and arrangement of the toes, and added: "the boxy shape and fronts leading led me to conclude southern flying squirrel." She also notes: "I remember reading something by David Moskowitz about toe 5 (hind, outside toe) in northern being almost as long as the middle 3." The toe arrangement Moskowitz describes is characteristic of all three North American flying squirrels. Here is his blog post on the subject.

Finlaly, R Scott Semmens noted the habitat and the "boxy" hopping gait, then added: "trail width of around 5 cm [is a match for southern flying squirrel, while] the hind foot length is over 2.54cm ruling out a brave chipmunk."

Semmens' comment about the length of the hind print caught my eye and got me thinking a bit more deeply about track measurements. As part of my recent research on southern flying squirrel tracks, I was comparing the size of this nocturnal glider to that of the eastern chipmunk. On average, eastern chipmunks are larger in every dimension—including the length of their hind feet. Published ranges for the hind foot of southern flying squirrel (including the heel) range from 21-33mm, while those for eastern chipmunk range form 31-38mm.

Yet as Semmens notes, the published ranges for eastern chipmunk hind tracks tops out smaller than those for southern flying squirrel. Elbroch lists the length of eastern chipmunk hind tracks as ½-⅞” and the length of southern flying squirrel hind tracks as ½-1⅜”. Paul Rezendes offers us a clue as to how the larger animal might be leaving smaller tracks. In Tracking & the Art of Seeing, Rezendes gives measurements similar to Elbroch's for eastern chipmunk tracks, and then adds:

“The full length of the hind foot often does not show in mud, which explains the longer length of the front track compared to the hind. In snow, the hind foot will register its full length, and the hind track will be longer than the front track.”

It seems that the difference here is in the typical presentation of the tracks. Chipmunks tracks are rarely seen in the snow. These fossorial squirrels tend to stay underground most of the winter. Flying squirrel tracks, on the other hand, are rarely seen except in the snow. As a result, some of what we think of as differences between chipmunk and flying squirrel tracks may actually be difference between squirrel tracks in mud and squirrel tracks in snow. We could expect a chipmunk hind track in the snow to be a little longer than that of a southern flying squirrel.

Curiously, although it appears that Elbroch's measurements for chipmunk hind tracks do not to include the heel, both of his photos for this species in Mammal Tracks & Sign show the heel registering. Although neither photo includes a scale, using his other measurement ranges as a guide, the hind tracks appear to range up to 1½” long—considerably more than the ⅞” he lists as the maximum length.

I found this to be a good lesson in both the value and the limitations of track measurements published in the literature.

Dolan, P. G., & Carter, D. C. (1977). Glaucomys volans. Mammalian Species, (78), 1.
Elbroch, M. (2003). Mammal Tracks & Sign: A Guide to North American Species (1st ed). Mechanicsburg, PA: Stackpole Books.
Rezendes, P. (1999). Tracking & the Art of Seeing : How to Read Animal Tracks & Sign (2nd ed.). New York: HarperCollins.
Schwartz, C. W., Schwartz, E. R., Fantz, D. K., & Jackson, V. L. (2016). The Wild Mammals of Missouri (Third revised edition). Columbia: University of Missouri Press : Missouri Department of Conservation.

Cedar Creek Wildlife Survey, Winter 2019

posted Feb 1, 2019, 3:51 PM by Jonathan Poppele   [ updated Feb 1, 2019, 3:52 PM ]

On Saturday, January 26, Cedar Creek hosted its largest ever wildlife tracking survey, with 27 trackers and naturalists heading out in five teams to explore the landscape and share stories from the tracks and sign we found. Undaunted by the arctic cold, our teams recorded the tracks and sign of at least 18 different species of mammals across the reserve, and had some amazing adventures along the way. Here is our story of the day.

Cedar Creek received about two inches of fresh snow mid-week on top of a thin, hard base, which offered a great substrate to catch tracks. The new snow meant that only tracks from the past day-and-a-half were visible, allowing our teams to see clear gait patterns and follow individual trails. As we headed into the field on Saturday morning, a light dusting of snow added an extra challenge as it obscured fine details on all but the freshest tracks.

With such a large team, we were able to cover lots of ground. The five teams spread out across the length of the reserve with one team headed south to the bison enclosure, two teams sticking close to Lindeman Hall, and two teams headed up to the North Unit.

mink trail on top of a log
The team in the south focused their attention on tracking coyote. Over the past several surveys, we have noticed a lack of coyote activity in many parts of the reserve and wondered where they were concentrating their activity. It now seems clear that the answer is in the bison enclosure. With the favorable snow conditions, the team was able to not only identify, but also trail coyote for some distance. Along they way they found signs of foraging and bedding down. One thing the team notes was the overall shape of the coyotes' trails. Though the coyote moved in fairly straight lines, those lines followed the natural curves of the landscape. The influence of the landscape on the coyotes' movement and behavior was clearly written in the fresh snow.

In addition to coyote, the team identified mink, weasel, rabbit, vole (via a live sighting!) and squirrel, including some large tree squirrel tracks that may have been left by fox squirrel. They also found a mysterious trail that at first appeared to be a coyote, then took on more the appearance of a fisher before finally revealing itself to be a raccoon. The trickster strikes again.

The teams that stayed close to the main campus found large numbers of deer tracks, especially on Cedar Bog Lake. The concentration of deer near Cedar Bog Lake is interesting, as this is an area where we often find wolf tracks. But there were no wolf tracks evident on the lake that day. Besides the deer, the team identified mouse, vole, squirrel, red fox, coyote, weasel and fisher trails. Both teams were stuck by the large amount of weasel activity in the area. It seems we are finding more weasel trails this winter than we have in the past. Is this because there are more weasels in the areas we are tracking, or are we just getting better at spotting then and distinguishing their narrow trails from those of small rodent?

Our teams in the North Unit set off to find evidence of the resident wolves--and were not disappointed, despite an unexpected start to the day. One team tracked along the main road, while a second team (with special permission) ventured off trail to look for evidence of breeding among the wolves. Surprisingly, the first set of tracks these teams found were those of a coyote moving straight down the road inside of Gate 7. There were two sets of tracks. One leading in and another leading out—as though a single coyote had ventured in and returned. This is the first time any of our teams has verified coyote tracks following this road. We have gotten the impression from past surveys that coyote are largely excluded from this area by the wolves—or at least kept out of the open. But this trail was clear and unambiguous. The trail ended at the edge of the woods, near the first road junction. There, the carcass of a road killed deer was being scavenged by foxes as well as coyotes, and perhaps weasels as well. Could it be that the wolves have enough food at the moment that they are tolerant of a visiting coyote? One thing is certain, the wolves are near by. Although there were no fresh wolf tracks at the carcass, there was a fresh trail less than 50 yards down the road.

This fresh trail marked the starting point for the second North Unit team. Over our past two surveys, evidence has been growing that there are now at least two wolves at Cedar Creek. We have suspected for some time that the animal we have been tracking for the past two years is a now three and a half year old female. If the second animal is a male—and the size of the second set of tracks suggests this is the case—we wanted to look for evidence of breeding: raised leg urination marks with blood in them. The best way to find these would be to follow a fresh wolf trail. And that is what the team did.

We first found the tracks where the animal turned off the road into the woods. And at that spot, the team found a raised leg urination. Based on the tracks, we believe that this was the trail of the female we have grown familiar with. The tracks were smaller than those we found last summer, and the position of the feet compared to the urine was consistent with a female.

The team followed the trail of this animal for about a mile-and-a-half. What likely took the wolf a few minutes to lay down took the team abut four hours to follow.

Possible Bear Den
Not long after entering the woods, the wolf emerged again into the open—in a spot we have found tracks and scat on past surveys. She ventured about 50 yards from the woods in a trot before making a sharp turn and returning to the tree line in a full gallop. When she reached the edge of the trees, she dropped back into a trot, then a walk as she turned parallel to the edge of the woods, walked about 20' with a perfect view out into the field, then angled deeper into the forest. Had something startled her? A car out on the highway, perhaps?

Once back in the woods, she traced a winding path south in the direction of Cedar Bog Lake. Usually moving in a trot, she moved though dense thickets, under fallen trees, and across frozen bogs with equal ease. Her trail passed by two possible bear hibernation dens. Was this just by chance? Or is there some reason a wolf would swing past a bear den during her rounds? Near Cedar Bog Lake, her trail turned west and headed in the direction of Cedar Creek. Shortly after her trail turned, it crossed another of her trails, also left within the past day-or-so. As the trail continued farther west, the team began to see signs of more wolf trails of various ages—but all still fairly fresh—in addition to an increasing number of fisher trails. Along the way, the team found two more urine marks. Both of these appeared to be squat urinations, rather than raised leg, and neither showed any sign of blood. There is no sign that she is breeding this year.

Deer carcass
Early in the afternoon, after more than three hours on the trail, the team found a large set of fisher tracks that had been made since the light snow of the morning had stopped—likely no more than an hour old. A short distance farther, the fisher tracks stopped at a chunk of deer hide sitting on top of the snow. Near by were more bits of hide and areas of trampled ground, which led to the remnants of a deer carcass.

Not much was left of the seven point buck. The head, neck and right-front leg were mostly intact, along with the spine and some of the ribs. But there was little else. The stomach and a few bits of other organs sat on the ground near by, and bits of hide were strewn across the landscape. A large hole in the deer's throat betrayed the cause of death. Which wolf had taken this deer was a mystery to us, but the tracks made it clear that both our female and a second wolf had come to feed. As the team headed back to the car, they came across the tracks of the second wolf. Its tracks were much larger than the female the team had trailed all day, and matched the prints some of our trackers had sketched during our Fall Survey. The trails of the two wolves crossed each other in several places. They are clearly interacting, but there was no evidence that the animals were traveling together.

It was a rich day for all of the teams and as usual it left us with more questions than answers.

One thing we are all curious about is the number of weasel trails we were seeing. Have we simply not noticed how common they were, or are they more abundant or more active this winter?

We are also curious about the larger weasels on the landscape--the fishers. We have never identified fisher tracks during our spring, summer or fall surveys. They tend to stay in the woods where the ground is covered with leaf litter. We have not been lucky enough to spot their tracks crossing one of the sand roads. In our winter surveys, however, we find their tracks all over the reserve. What we don't know is how this abundance of fisher tracks relates to abundance of fisher. Are there lots of fisher at Cedar Creek, or a small number that range across the reserve? What is the typical range for a fisher, and what are typical densities? And can we learn to detect these forest dwellers when there isn't snow on the ground?

And we have lots of questions about our wolves. On this survey, we verified what we began to suspect over the summer--there are at least two wolves making use of the reserve. How are these animals interacting? They do not appear to be traveling together. Do they regularly share food? Are they both killing deer? When one takes a deer, do they typically share the carcass?

With these and many more questions in mind, we look forward to our next Cedar Creek Wildlife Surveys. Here is our schedule for 2019:

Spring Survey: Saturday, April 13
Summer Survey: Saturday, July 13
Fall Survey: Saturday and Sunday, September 21-22

A warm thank you to everyone who took part in our winter survey and helped bring back the stories from the landscape. We look forward to getting out into the field with you again and building our understanding of the wildlife of Cedar Creek.

An Informal Bird Langauge Sit

posted Jan 14, 2019, 5:30 PM by Jonathan Poppele   [ updated Jan 14, 2019, 5:31 PM ]

On Saturday, January 5, our monthly Bird Language gathering was canceled because the Minnesota River Valley Wildlife Refuge was closed due to the federal government shutdown. However, a few of us met in south Minneapolis for an urban bird language sit where Cedar Avenue crosses Minnehaha Creek. The weather was relatively warm for the season with a slight breeze from the west. We sat on the north and south sides of Minnehaha Creek. Note that the map is oriented facing south.

Throughout the sit American Robins flew over head from the northeast in small groups of 3 to 5 birds. It seems they were dispersing for the day from a roosting site in the southern part of Hiawatha Golf Course. A number of the Robins landed in the south eastern part of the sit area where we heard frequent calls and some alarms. Crows were also active with movement and calls in the sit area. One set of Robin alarms sounded when a Crow flew close to them in period 2. There didn't seem to be much reason for Robins to be overly concerned about a Crow this time of year (away from nesting season), but they may have been responding to secondary alarms if the Crow was moving and calling in response to a threat (said with the "Corvid disclaimer" -- interpreting Corvid behavior may be a foolhardy venture). In period 4 we heard a Northern Flicker call in the sit area. After the sit we investigated a peculiar Raccoon trail with a direct register walk, sorted out differences between Red and Grey Squirrel tracks, and watched a Bald Eagle fly overhead.

January Natural Mystery

posted Jan 11, 2019, 2:10 PM by Jonathan Poppele   [ updated Jan 11, 2019, 2:10 PM ]

December 2018 Natural Mystery Answered

posted Jan 11, 2019, 2:08 PM by Jonathan Poppele   [ updated Jan 12, 2019, 3:32 PM ]

The December Natural Mystery was an extremely challenging track. At first glace, it looks like a deer, and indeed there were deer tracks in the area. But this is not a deer track. Rob Grunewald was the first to point out that there was something strange about the drag marks into and out of the print. They are broad and flat, rather than showing a pair of groves that we might expect from the tips of a cloven hoof. Kim Cabrera picked up on this as well, and takes it from there with her correct interpretation:

Domestic dog. There appears to be some sort of drag heading into the track, which is headed to the right. At first, I thought it might be a set of squirrel tracks going to the left, but it looks more like a dog to me. There are some faint indicators of claw marks to the right side. The points are the two leading toes, with the claw marks. Nearer the 1 inch mark on the ruler, there are the outer two toes of the dog's track. I think it slipped or just dragged the foot a little bit as it made this particular track

Yes, this is a domestic dog track. Kim is exactly right that the outer toes (2 & 5) are faintly visible in the print--just much fainter than the impressions of the middle toes. I came across this track on a day I was out looking for deer trails to follow. The entire outing was a reminder in how much dog tracks can resemble deer tracks in the snow. On some of the harder packed trials, I was regularly finding dog tracks that only clearly showed toes 3 & 4 and looked surprisingly like deer tracks. This track was the most extreme example, but I was doing a lot of double takes that day!

Thanks as always to everyone who offered answers to this Natural Mystery.

1-10 of 52