February 2026 Natural Mystery Answered

In our February Natural Mystery, Mark Fulton invited us into the otherworldly realm of macro photography. It is likely that none of us had ever anything quite like this image before. Nevertheless, three of you worked through the clues and correctly identified this tiny object. Congratulations to Maria Wesserle, Haleigh Ziebol, and Adrian Iacovino for figuring out what this object is and who was responsible for leaving it on the snow.

This is a shrew scat, most likely from a masked shrew (Sorex cinereus).

Maria kicks us off with this observation:

“In the photo above, we see a dark-colored tube with a tapered end that appears to contain the remnants of insect exoskeletons.”

Based on this appearance, Haleigh offered the following interpretation:

“[The insect parts] led me to consider an insectivore who would occupy a small hole in the snow. While moles lives underground and have an insectivorous diet, they rarely have entrances visible to their burrows. Moles that deposit scat above ground do so in latrines. One pellet does not a latrine make. That leaves us with shrew. [The small size suggests that] this scat likely came from a smaller shrew in the Sorex genus.”

Spot on. Maria shares a bit about her first impressions, and some additional details about shrew scat:

"When I first glanced at this photo, I thought it was a cough pellet – that is, until I noticed the scale. At only 4mm long and just over 1mm in diameter, this is a very tiny specimen! I can't think of anything else that it could be besides scat. The fact that it was found in the snow near a hole (presumably a hole that somebody was using) lends credence to this theory. So who is tiny and tunnels through snow in the winter? Shrews!

According to Mark Elbroch's Mammal Tracks & Sign, cinereus shrew scats are 0.1cm - 0.2cm in diameter and 0.5cm long (1-2mm in diameter and 5mm long). In The Natural History of Canadian Mammals, Donna Naughton says the following of Sorex shrew scats:

‘Scat appearance varies with diet: shrews eating entirely soft-bodied prey, such as earthworms or slugs, produce a liquid squirt of faecal matter, but those eating hard-bodied insects produce small, tubular, black, sometimes twisted, scat with tapered ends that may contain undigested, often shiny bits of insect chitin.’

In the photo above, we see a dark-colored tube with a tapered end that appears to contain the remnants of insect exoskeletons. I am therefore calling this a shrew scat of the Sorex genus. It's likely a cinereus or masked shrew (S. cinereus), which are common in eastern North America, but pygmy shrews (S. hoyi) and arctic shrews (S. arcticus) also live in the area. While North American water shrews (S. palustris) also inhabit the region, they are quite a bit larger than the other shrews mentioned.”

Adrian describes the scat as “seed-like in shape with a slightly tapered end. It is a very light brown, almost rust colored.” Taking measurements from Elbroch’s Mammal Tracks & Sign, he then goes on to compare all the mammals found around Bemidji that could produce scat roughly 4 mm in length. His list includes:

• Deer mouse; 2-6 mm long

• Cinereus shrew; ~5 mm long

• Jumping mouse; 3-13 mm long

• Eastern chipmunk; 3-7 mm long

• Northern short-tailed shrew; 6-17 mm long (outside size range)

• Northern Flying Squirrel; 3-10 mm long

• Meadow vole; 4-8 mm long

He offers the following analysis of these species.

"Volume

Based on the description of this scat deposit, I am assuming that this was a singular deposit in front of a snow hole. Several of my candidates (voles, flying squirrel and deer and jumping mice) typically have latrines with multiple deposits in one area – so I am ruling them out.

I have little experience seeing scat like this and so it is hard for me to assess if this is a typical or atypical volume other than plurality. This is too short of a scat for Blarina brevicada (Northern short-tailed shrew). As for Sorex cinereus, it looks spot on for length.

The single, isolated pellet at a tunnel entrance is consistent with a small insectivore moving through the subnivean network, rather than a herbivorous rodent that typically leaves clustered droppings in runways or latrines.

Contents

I notice that parts of the contents have intact structures. I would assume that these structures have chitin (insect exoskeleton) that are not digestible for the consumer. If this were a scat from an herbivore, I assume that their digestive system would work to pulverize the material into a mush that would appear to have a consistent granular like scat. For this reason I am eliminating traditional herbivores on my list (voles). 

Although deer mice may consume invertebrates, their winter diet leans more heavily on seed – which produces a more seed-rich pellet without chitinous fragments that I am claiming to be evident here.

During the winter months, of my above candidate list, to my knowledge, only the shrews would be actively searching for and consuming winterized insects in leaf litter in the subnivean layer.

Context

With this scat being 'found next to a small hole in the snow, in -25 °F temperatures,” I am eliminating jumping mouse, chipmunk, and flying squirrel because these animals either don’t go into snow holes, or would not be out exposed in these conditions. Furthermore a flying squirrel would have a latrine in a tree cavity. 

Shrews are active all year round and have to eat a lot to keep up with their incredible metabolism. Northern short-tailed shrew is my runner up candidate, and I do think that there could be a scat from this species that could potentially be 4 mm in length. However, the length and the rest of my evidence brings Sorex cinereus to the top of the list.”

In the field, we had the added advantage of the animal’s trail and the size of the hole. You can see our observation here on iNaturalist which shows the trail, the hole, and the scat in the snow near the 6 mm mark on the ruler.

Congratulations again to Adrian, Haleigh, and Maria for identifying this tiny scat. And thank you to all of you who wrote in with your guesses and interpretations. Sharing your ideas and your process helps us all.