February 2021 Natural Mystery

posted Feb 17, 2021, 9:16 AM by Jonathan Poppele   [ updated Feb 17, 2021, 9:16 AM ]

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January 2021 Natural Mystery Answered

posted Feb 17, 2021, 9:15 AM by Jonathan Poppele   [ updated Feb 17, 2021, 9:16 AM ]

It looks like people had some fun with last month’s natural mystery. At a quick glance, it resembles a cat or dog track—but Bill Cass, Kirsten Welge, and Rob Grunewald saw through this first impression and correctly identified the track maker. They even took a stab at narrowing it down to the species.

These are the tracks of a typical squirrel—a member of the Tribe Sciurini, which includes the red squirrels, gray squirrels and flying squirrels.

Bill starts us off with these observations:

“Although from a distance it could be mistaken for a cat track, we see individual toes in the ‘toes’, so instead of toes we have four individual feet, meaning the ‘heel pad’ is actually a butt. Although the toes are not clear, they are long, clawed, and arranged symmetrically.”

Rob adds that “toes 2, 3, and 4 in the two outside hind tracks are close together, indicative of a squirrel track.”

So these are squirrel tracks. Can we narrow it down to the species? Rob suggests that with the observation coming from just outside Buffalo “the habitat would lean more toward a gray squirrel than a red squirrel.” That’s a reasonable place to start, but there is reason to be cautious here. I get red squirrels in my urban back yard in St. Paul. Similarly, a search on iNaturalist shows a number of observations of red squirrels in the Buffalo metro area. Gray squirrels are unquestionably more common, but it doesn’t look like we can rule out red squirrel based on what we know about the location.

Kirsten offers some additional details about the tracks to make a good case for a Sciurus species while also using my new favorite vocabulary word:

“The right impression also shows a clear, robust trapezoidal metapodial pad, which is diagnostic for one of the larger tree squirrels. The size of negative space between the toe pads and metapodial pad also points to a larger tree squirrel. A red squirrel would show more delicate toe pads, and a longer negative space between metapodial pad and toe pads.“

The details of the foot morphology do indeed point us toward a large tree squirrel in the genus Sciurus. The two large tree squirrels in the eastern US are the Fox Squirrel and Gray Squirrel. Mark Elbroch notes that “the hind toes of fox squirrels are slightly more compact than those of gray squirrels,” but also that “the tracks and trails of these species are similar and easily confused.” So let’s consider the range of each species.

Many range maps suggest that fox squirrels could be found in the Buffalo, NY, area. But the reality appears to be that they are exceptionally rare near by. A search on iNaturalist shows only 3 fox squirrel observations within 50 miles of Buffalo, only one of which is Research Grade. This leaves the eastern gray squirrel, Sciurus carolinensis, as our most likely candidate.

Congratulations again to Bill, Kirsten and Rob for sharing their answers and their reasoning with

January 2021 Natural Mystery

posted Jan 12, 2021, 4:20 PM by Jonathan Poppele   [ updated Jan 12, 2021, 4:20 PM ]

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December 2020 Natural Mystery Answered

posted Jan 12, 2021, 4:03 PM by Jonathan Poppele   [ updated Feb 17, 2021, 7:58 AM ]

Our December Natural Mystery proved to be a real challenge. We received a number of thoughtful guesses, but no correct answers. There is a modern proverb in American medical schools that has, appropriately, been adopted by many trackers. "When you hear hoofbeats in the night -- look for horses, not zebras."1 But I might add that if we examine carefully, and what we find is not a horse, we must consider...

This is the carcass of a Mongolian Jird (Meriones unguiculatus), better known as a gerbil. It was almost certainly someone's unfortunate escaped pet.

As we think through this mystery, it may help us understand that although we always want to "look for horses," we should not completely rule out zebras.

As several people noted in their answers, the animal has the large hind legs characteristic of a bipedal rodent, such as a kangaroo rat. But there no members of family Heteromyidae native to the Eastern U.S.--so we would need to come up with a plausible story for how one could have ended up at the edge of someone's yard in a small town in Pennsylvania. Even putting range aside, a study of Heteromyidae finds that their hind legs and their tails are even longer than what we see here.

The body form isn't a match for any of Pennsylvania's native rodents, either. Jumping mice, which are closely related to the bipedal Jerboa of the Mideast, have larger ears, a different shaped forehead, and different proportions in their hind legs. The same is true of woodrats, deer mice, and Old-World rats. Voles have shorter tails and less developed hind legs.

As we look for "horses," we come up empty. So we need to consider zebras. We need to consider animals that are not native to Pennsylvania, and not known to be invasive, but none the less might plausibly turn up there. That combination suggests a pet.

A quick search for "pet rodents" finds that hamsters, rats, mice, gerbils, and guinea pigs are the most common rodents kept as pets. A search for pet gerbils yielded this page. This and other information about pet gerbils suggest that is our match. Our "zebra" turned out to be a Mongolian Jirid.

Part of what supports this conclusion is that, despite the fact that we have identified a "zebra," there is still a plausible explanation for how it ended up in Oil City, Pennsylvania. From my research, it appears that there are other gerbils in the sub-family Gerbillinae have similar proportions. From the photo alone, I don't see any way to distinguish them. But the Mongolian Jirid is the only one that is known as a pet in the United States. So it's a zebra, but its the kind of zebra that are kept at the local zoo.

Mongolian Jirids are native to the grasslands, shrublands and deserts of China, Mongolia and Russia. The species was named by Henri Milne-Edwards in 1867 based on specimens sent to the French National Museum of Natural History from Northern China by the zoologist and Catholic missionary Armand David. The name roughly translates as "clawed femur."

Gerbils were brought to the United States from eastern Mongolia in 1954 for use as a lab animal, and soon found their way into the pet trade. All pet gerbils in the United States are decendents of the original lab stock of 20 males and 26 females.

1) According to Quote Investigator, the first known record of this saying was in a column called "Our Town" by Charles Allbright, published in the "Arkansas Gazette" of Little Rock in October 1962. Here is an extened quote:

"The father of a young man who was there reports that at the University of Arkansas School of Medicine this week a doctor surrounded himself with about a dozen students and sought to go to the heart of proper diagnostic procedure.

In the end he summed up good diagnosis this way: “When you hear hoofbeats in the night, look for horses — not zebras.”

December 2020 Natural Mystery

posted Dec 15, 2020, 10:35 AM by Jonathan Poppele   [ updated Dec 15, 2020, 10:35 AM ]

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November 2020 Natural Mystery Answered

posted Dec 15, 2020, 10:09 AM by Jonathan Poppele   [ updated Dec 15, 2020, 10:36 AM ]

Everyone who sent in an answer to our November Natural Mystery recognized this as a webbed bird track, but there was some question about exactly which web-footed bird was responsible. Congratulations to Joe Conrad, Mike Holtz and Kirsten Welge who correctly identified the track maker.

These are the tracks of a mallard. Joe starts us off with this pithy explanation:

"Web footed—not big enough to be a Canada Goose."

Kirsten adds a few more details, noting:
  • Each print shows three clear toes, a hallux, and webbing.
  • Metatarsal pad looks to be circular. Goose metatarsal is typically teardrop-shaped.
  • Size of each track is about 2.75” long, which points to a large-footed duck and effectively rules out goose. Elbroch's goose track range starts at 3 7/8"" range.

Mike added that “Ring-billed gull would leave a smaller track.” This is true, but herring gulls leave similar size tracks and could be around this time of year. Kirsten pointed out the hallux in the tracks, and that is one clue that these are duck tracks rather than gull tracks. Ducks have a larger hallux than gulls, which registers more reliably in the tracks. Additionally, gulls nearly always splay their toes wider than we see here (ducks sometimes do as well), and their toes almost always appear more curved.

Mike also pointed out that goose and swan track would be larger "based on the time of the year." And, yes, gosling and cygnet tracks could overlap in size—though, as with gulls, geese and swans have a proportionally smaller hallux that is less likely to show in their tracks and, as Kirsten noted, their metatarsal pad looks different.

Finally, Mike notes that “mallards are a safe bet around town any time of year.” He suggests that “black duck is also a possibility, and looks similar.” And, indeed, black duck tracks are indistinguishable from mallard tracks. We can only say with 100% confidence that these tracks were made by a mallard rather than a black duck because Rob watched the duck leave the trail. However, given how much more common mallards are in the Twin Cities at this time of year compared to any other large duck, we could have greater than 99% confidence that these are mallard tracks based on the location.

Congratulations again to Joe, Mike & Kirsten, and thanks to everyone who submitted an answer to this mystery.

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November 2020 Natural Mystery

posted Nov 16, 2020, 9:52 AM by Jonathan Poppele   [ updated Nov 16, 2020, 9:53 AM ]

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October 2020 Natural Mystery Answered

posted Nov 16, 2020, 9:29 AM by Jonathan Poppele   [ updated Nov 16, 2020, 9:39 AM ]

We received a range of answers to our October natural mystery implicating a wide range of animals from birds and mammals to freshwater sponges. Congratulations to our generous Patreon supporter Mike Holtz and one anonymous contributor who successfully identified this common but rarely seen sign.

This is beaver scat. Mike Holtz gets us started with this pithy and useful description:

“Sawdust meatballs! Found in water, contents look like mostly woody fiber, size looks good at around an inch to an inch and a half.”

Our anonymous contributor goes into some additional depth and analysis:

"I notice the pellets appear to contain woodchip pieces. The size matches the range of 1"-1.25" in length for beaver pellets and 0.75" in diameter. The yellow coloring is interesting-- perhaps from the water that they were floating in? Or the type of tree? When I look at photos of fresh beaver chew sign on conifer trees (trees popular in BWCA), I see instances of yellow or red color to the cambium. Perhaps this is retained in the scat. Beaver would be likely inhabitants of the BWCA lake so also a reasonable candidate for scat. Owl pellets have a similar elliptical shape but would contain fur and bones rather than wood. Owl pellet size covers this range, but if they were in water, I'd expect to see the swollen appearance of wet fur."

Beaver usually deposit scat in the water, so we rarely find it even where it is quite abundant. We are most likely to find beaver scat after water levels drop, exposing previously submerged ground. Our tracking club has found beaver scat at Ft Snelling State Park on just four occasions, despite the dense population of beaver there.

Congratulations again to Mike and our anonymous contributor!

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Fall 2020 Wildlife Survey Story-of-the-Day

posted Oct 9, 2020, 10:46 AM by Jonathan Poppele   [ updated Oct 9, 2020, 10:46 AM ]

Our Fall Wildlife Tracking Survey took place this past October 3 at the Carlos Avery Wildlife Management Area. Eight members of the Minnesota Wildlife Tracking Project gathered to survey the sandy roads or Carlos Avery, just a few miles from our regular survey location at Cedar Creek Ecosystem Science Reserve. While we only found clear tracks of a few species of mammals, they included footprints we had never seen in the filed. We also may have verified a species we had never confirmed at Carlos Avery before. Here is our story of the day.

Our group divided into two tracking teams for the day. One team walked a loop around Pools 6 & 8, focusing attention on an old sand pit just off Wyoming Rd. dubbed “Peaceful Canyon” by our friend Blake Southard. The other team followed South Rd into the southern extension of the WMA, just across Co Rd 18 from the DNR headquarters.

The dirt roads through Carlos Avery provide a mix of substrate ranging from hard, gravely soil to soft sand. There are natural track traps along most roads, but many of these areas get regular traffic. With duck hunting season in full swing, there were few clear tracks along the roads. Digging sign from fossorial mammals along the edges of the roads, however, abounded.

Both of the teams noted large, fresh pocket gopher mounds and mole runways. The greater Twin Cities Metro Area is home to only one species of Pocket Gopher—the Plains Pocket Gopher (Geomys bursarius)—so we can identify these mounds with confidence. Two species of moles are found in the area. The Eastern Mole (Scalopus aquaticus) and the Starnosed Mole (Condylura cristata). Starnosed Moles are weaker diggers than Eastern Moles, are most common along the edges of waterways, and rarely push up the kinds of prominent runs we were finding. We can safely identify most of these runs, many of which were extremely large, as having been made by Eastern Moles.

Many of the pocket gopher mounds we found had tunnel openings in them. Some of the mole runs we found showed openings in them as well. Pocket gophers typically plug their tunnel entrances to maintain consistent humidity and deter predators. Most times of the year, it is rare to see open tunnels in pocket gopher mounds. On this occasion, however, they were quite common. Do pocket gophers have a different set of needs at this time of year? Are these open tunnels related to dispersal? Are they the work of other species, such as voles, making use of the gophers tunnels?

The open mole tunnels were their own mystery, and also offered a rare treat. On the two-track road leading into Peaceful Canyon, one team found a mole runway so shallow that it was an open trench rather than a tunnel. And on the floor of the runway were the clear tracks of an Eastern Mole. Unlike species such as the Hairy-Tailed Mole (Parascalops breweri) which regularly come to the surface to forage in leaf litter, Eastern Moles are almost completely fossorial and may spend their entire lives underground. Eastern Mole tracks are quite rare, and none of our trackers had ever seen them in the field before. As far as we know, these are the only photographs of Eastern Mole tracks on iNaturalist, or anywhere in the tracking literature. 

And these weren’t the only surprising tracks our teams found at Carlos Avery. One team returned with a photo of a single large canine print from a sandy roadside. It was an isolated tracks. The rest of the trail had been covered over by human traffic. But it was tantalizing. The print measured 3 3/8” long and 2 1/2” wide, with a star-shaped negative space. It is always difficult to identify a large canine to species based on a single track. Carlos Avery is a popular spot for dog walkers, and canine tracks in the WMA are generally best considered “domestic dog until proven otherwise.” In this case, we had something to compare the track to—field drawings of the hind track of the wolf our team had been tracking at Cedar Creek for the past few years, prior to the pandemic. Not only is the size of this track an exact match, but specific shape of the palm pad is as well. While it is possible, at least in principle, that there is a domestic dog with a rear palm pad that has the exact proportions of the wolf we have tracked at Cedar Creek, it is highly improbably. If we found this track at Cedar Creek, I think none of us wold have any doubt that it was from our local wolf. Cedar Creek is only about 10 miles away from where this observation was made, and is connected by nearly unbroken stretches of woods and wetlands. So this shouldn’t be a huge surprise. But this is the first time we have gotten a strong indication that the wolf is ranging into Carlos Avery. It also appears to be the first track from this animal we have recorded since last winter.

There were other sightings throughout the day as well. We identified some animal remains, such as this meadow vole and this red-bellied snake who were unfortunate victims of cars. Our teams also found the tracks of three species of squirrels and were able to take a deep dive into the sometimes subtle differences between the tracks of chipmunks, red squirrels and gray squirrels. Some of these observations also offered a reminder to us in the value of multi-factor analysis. One of the chipmunk trails we found measured 3 3/16” wide, which is wider than any of the published ranges for chipmunk trails. Elbroch lists 2 7/8” as the upper limit. But the track size and foot morphology were distinct. Apparently they grow ‘em big in Carlos Avery.

You can see all of our observations from the day here on iNaturalist.

Our Fall Survey is the last wildlife survey for 2020. We are holding off on scheduling or 2021 dates until we have a better understanding of when normal operations will resume at Cedar Creek. Stay tuned for future announcements and keep an eye on the calendar. We hope you can join us for a future survey.

October 2020 Natural Mystery

posted Oct 9, 2020, 10:22 AM by Jonathan Poppele   [ updated Oct 9, 2020, 10:22 AM ]

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