Analysis of scat pix From Cuyamaca Rancho State Park 9/30/25

Don Rideout took 22 iNat obs of poop found along the West Mesa Loop on 30 September 2025. See the iNat obs for a map of the locations, as well as the complete set of photos for each observations. The purpose of this intensive sampling was to see if the poops clustered into separate categories that might give us hope of identifying the poopers.

Tom Chester measured the sizes of the poop, both for each entire "poop event", and for the longest individual members of the poop, for the 19 obs which had individual components. Three of the 22 obs had amorphous or decayed poops in which individual members weren't apparent.

Plots of the sizes of the entire event, and the longest individual members, produced similar plots, with two main groups and two outliers. The plot of the longest individual members of the poop had the tightest groupings, shown in Fig. 1.

Fig. 1. The length and width of the longest individual member of each poop event. The poop events are labeled as those with fur in the poop (5 events); and those with seeds or plant material (14 events). Individual segments could not be recognized in three of the obs, and are not represented in this plot. Two groups, representing different sizes, and two outliers, have been labeled. See also unlabeled plot.

Poops with fur are the largest ones.

Group 1 only has poop with seeds.

Group 2 has some members with fur, and some members with seeds.

The size range, and average size, of the longest individual members are:

Poop A is an unusual one in that it has fur and bones in it, including what looks like a deer hoof. Perhaps because of the bones, the scat is the widest of this set. Its individual segment size is 7.7 x 3.6 cm (3.0 x 1.4 inches), which is more typical of a mountain lion (1.0 to 1.5 inches wide) or a coyote (0.7 to 1.5 inches wide), than a bobcat (0.4 to 1.0 inches wide). The expert Rachel Larson examined the iNat post for this poop, and said "Mountain lion is my first guess. But I think you could also make the case for large coyote, given the hoof."

Poop B, consisting of fur, is the largest one for length by far, and is the most segmented, which argues for it being from a species of cat. Its individual segment size is 9.8 x 1.9 cm (3.9 x 0.7 inches), which is more typical of bobcat (0.4 to 1.0 inches wide) than a mountain lion (1.0 to 1.5 inches wide).

The poop in Group 2 consists both of specimens with just fur, and specimens with just seeds, which argues for it being from either coyotes or foxes. Its average individual segment size is 6.7 x 2.3 cm (2.6 x 0.9 inches), which fits coyotes (0.7 to 1.5 inches wide) better than foxes (0.5 to 0.75 inches wide)

The poop in Group 1 consists only of seeds or other plant material. Its typical size of 3.3 x 1.6 cm (1.3 x 0.6 inches) fits foxes (0.5 to 0.75 inches wide) best.

A map of the scat locations shows some coherence to the locations of the scat in Group 1 and in Group 2; see Fig. 2. It is conceivable that one fox is responsible for the scats in Group 1 in the southwest corner of that map, and another in the northeast corner.

Fig. 2. Map of the locations of the scats in Groups 1 and 2, as well as Poops A and B.

All 22 poops are shown in Figs. 3 to 5 at the bottom of the page. The photographs are not all to the same scale. Measurements of the longest individual member, when they existed, are given below each photograph, along with the Group assignment. Click on the picture to go to the iNat obs.

We asked the expert Rachel Larson, who studied coyote diets for her masters thesis, for her review of this page to see whether our conclusions are sound. She kindly replied with the following:

I think you're definitely on to something. Diameter of scat is a good diagnostic tool for species ID, although I will say there can be some overlap among species. For example, typical gray fox scat is between 1-1.6cm in diameter, while bobcat and coyote scat is often 1.5-2.5cm. Length is more difficult to assess, because the content of the scat often determines how long it can get before breaking apart. But size is only one aspect; one must also consider morphology ("shape", e.g., blunt, segmented, ropey), contents, and location (both habitat-wise and the exact location of the deposit).

I also wonder about other species beyond these three that could also be present in Cuyamaca Rancho. Skunk and opossum are viable options, especially for the high-seed scats and ringtails might be possible as well in areas with lots of boulders. Opossum scat can be particularly difficult to distinguish from coyote scat. Ringtails will also place their scats on elevated objects like gray fox. In those cases, habitat associations may help to distinguish likely depositors. For example, gray fox prefer dense chaparral, but ringtails prefer areas with large boulders. Skunk and opossum are more likely to be closer to a riparian area whereas coyote will use all kinds of habitats. Skunks are insectivores and their scats are often full of bug parts in a way that other carnivores are not.

Scat ID is difficult even for experts. I often struggle to ID scat observations on iNat, even when they contain a ruler for sizing, because it is difficult to get the scat context (where it's located on the trail), the habitat information, and other important information (like paw prints). Putting notes on the observation about these kinds of things definitely helps, but it's still not the same as seeing the scat in person.

We really appreciated those comments, and thought they would be valuable for other iNat people as well! Rachel kindly granted permission for her comments to be placed online here.

Scats in Group 2 and those with fur

6.5 x 2.4 cm, Group 2.
6.8 x 2.6 cm, Group 2.

9.8 x 1.9 cm; the longest individual segment, and also the only one with a prominent "tootsie roll" (segmented) appearance, Poop B.
7.6 x 2.8 cm, Group 2.

7.7 x 3.6 cm, Poop A, our widest scat.
5.8 x 2.5 cm, Group 2

6.5 x 2.0 cm, Group 2
6.6 x 1.9 cm, Group 2

7.0 x 2.1 cm, Group 2 		(intentionally blank)

Fig. 3. Photographs, not to the same scale, of the five poops which had fur in them, along with the three other members of Group 2.

 

Poops in Group 1

3.8 x 1.1 cm, Group 1
3.6 x 1.5 cm, Group 1

3.4 x 1.9 cm, Group 1
3.3 x 1.9 cm, Group 1

3.3 x 1.7 cm, Group 1
3.3 x 1.7 cm, Group 1

4.1 x 2.3 cm, Group 1
3.1 x 1.4 cm, Group 1

2.5 x 0.8 cm, Group 1, the only one with mostly plant material other than seeds
2.4 x 1.5 cm, Group 1

Fig. 4. Photographs, not to the same scale, of the ten poops which had seeds in them in Group 1.

Disorganized or decayed poops with no measurements

Fig. 5. Photographs, not to the same scale, of the disorganized or decayed poops.

 

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Copyright © 2025 by Don Rideout and Tom Chester
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
http://tchester.org/analysis/poop/CRSP_250930.html
Comments and feedback: Tom Chester
Last update: 15 October 2025