October 2025 Natural Mystery Answered

Last month's Natural Mystery was a somewhat atypical, tricky scat for a common urban resident, and was made more difficult by my choice to highlight the scat forms and size on a ruler, rather than presenting them in situ. Many thanks to those who took on this challenge, and congratulations to Erin Anderson for identifying these pellets as the scat of an Eastern Cottontail.

What makes this scat particularly interesting to me is how often I've heard, "Cottontail scat looks nothing like deer scat." It is true that the classic cottontail scat (a single squashed sphere, like a Skittle) is easily distinguishable from the classic deer scat (a couple handfuls of oblong pellets, like chocolate-covered almonds). However, the more I look for scats, the more I see variations in form and volume, particularly in the shoulder seasons. However, four characteristics of scat -- contents, context, structure, and size -- can help us work through more complex deposits, and Erin touches on each of these to arrive at her answer.

I'll let Erin walk you through her process:

"This is a rather unusual presentation of Cottontail scat. Cottontail scat never fails to make me second guess. When I first looked at this, I thought "tiny, miniature deer!" I had that impression because this scat presents with the classic teardrop shape of deer scat, with one end coming to a point and the other end appearing more flat. Many deer scats have dimples on the opposite end of the pointed end."

Erin isn't the only one who has been challenged with scat differentiation. Park staff and researchers running a 2024-2025 survey for Appalachian cottontail in a Pennsylvania park surveyed transects and collected rabbit fecal pellets for DNA testing. While DNA analysis detected six samples of the target species, results also showed several samples were, in fact, deer scat. [Article link]

"Here, though, size and substance lead me to conclude Cottontail. I have seen many, many cottontail scats in my own yard in Minneapolis. These deposits look a bit wetter and more teardrop shaped than a lot of Cottontail scat I've seen. But I recall the temperature being unseasonably warm at this time, so warmer weather could have affected the moisture content in the plant material consumed, especially after a first initial frost. As I examined these droppings more closely, I noticed the vegetative material in the drops that I would expect but also noticed some mucus on some of the droppings. I read on Cottontailclub.com that rabbits may pass mucus-covered scat when their diet is not providing them the sustenance they need or they are experiencing an issue with their gastrointestinal system."

As Erin describes, scats are a product of diet and digestion -- and both of these elements are dynamic. The atypical shape of these pellets sent me down a rabbit hole to review potential causes. Domestic rabbit owners and vets report that double or triple scats (seen above the 3.3 cm and 6 marks) can indicate the usual muscular contractions of the gut are slowing down and allowing pellets to collide in the intestine. Darker, moist scats may indicate the rabbit is getting too much protein in their diet. The presence of mucous (that reddish brown jelly above the 5.5 cm mark) may point to irritation of the intestinal lining. And small misshapen scats may indicate the rabbit is experiencing stress, and not eating enough. [For photograph examples, review this BUNS shelter article and Medirabbit.] 

I'll add one item to address another common visitor to this yard, the Eastern gray squirrel. Elbroch's Mammal Tracks and Sign gives a range for gray and fox squirrel pellets as large as .8 cm in diameter and 1 cm in length. (iNaturalist has several research-grade gray squirrel scat observations: from a 2023 certification in Minnesota, and a slightly larger deposit). 

While several of the smaller teardrop pellets fit that measurement range, two elements rule out this candidate: 

1) From the color and shine, we can see this cluster of scat is all the same age, therefore deposited at the same time. This volume would be massive for gray squirrel, but appears reasonable for a cottontail experiencing GI issues.

2) Two scats within this cluster are squashed spheres: the common form for cottontail, but not a match for any form of gray squirrel deposit. 

As Erin concludes:

"Now, I could be overthinking all of this. I am still seeing several round, "Skittles"-shaped droppings among the group of deposits, along with the dry-looking bits of vegetation within the deposits. Elbroch confirms that Cottontail scat can be teardrop shaped (Mammal Tracks & Signs, pg. 506)."

Congratulations again to Erin, and thanks for sharing her process with all of us. And thank you to everyone who submitted your answer and process for this Natural Mystery!