Aging Animal Scats – A Study with River Otter Scats
Researchers often use scat (feces) counts as a way to determine abundance of various species. The basic idea is that if you know the rate that an animal defecates (say 3-4 times a day), and you’re able count scats from a known window of time, then you should be able to estimate the number of individuals in a given area. The problem is that it can be really tough to make sure you’re not counting old scats.
One method to ensure only fresh scats are counted requires researchers to search the survey site and mark or remove all the scats before the survey. Another method requires surveying after a snow. Some methods though require the observers to age the scats. I once worked on a project in Colorado where I had to count elk pellets from this season only. Even though the goal was to identify scats that are a year apart in age, it was not always easy.
Accurately aging animal scats can be extremely challenging. Weather, contents, and location can dramatically effect the way a scat ages. In fact, two scats of the same age placed a few feet apart may age at dramatically different speeds depending on the microclimate in each location.
A River Otter Scat Experiment
In 2005, my wife and I worked as wildlife technicians for a river otter project in Missouri. The project required us to canoe roughly 10 miles a day along different rivers and search for river otter scat. I decided this was a rare opportunity to collect extremely fresh otter scats (sometimes called spraints, feces, or droppings) and document how they age.
I placed scats in either the sun or the shade, documented the weather, and took daily photos. All told, I did this with 5 scats in the sun and 3 in the shade. In order to reduce the number of photos in this post, I decided to only post photos from 1 scat placed in the sun and 1 placed in the shade. The scats used in this study contained entirely crayfish.
River Otter Scat in the Sun
(Click on the images to view full size)
The fresh scat is compact, moist, and dark red.
The scat is looser after just 1 day in the sun.
Note the dramatic change between day 2 and 3. In only 2 days the scat has lost much of its red color.
After a rain, much of the red color returned to the scat.
After a few slightly drier days the scat has lost much of the red color.
Even after 10 days, the red coloration returned to the otter scat after a light rain.
After several days of rain and a persistent reddish color in the otter scat, a single day of sun has resulted in a complete loss of the reddish coloration.
After 17 days of aging, I flipped over the scat and found the underside to still contain a strong red coloration.
River Otter Scat in the Shade
The fresh scat is shiny, moist, and a consistent dark red color.
Notice the dramatic change in the scat between day 2 and 3. I believe insects may have fed upon the scat during the period between these photos.
After 8 days of almost continuos sun, the scat is almost completely bleached white.
A day of rain and the color quickly returns to the scat.
Notice how fast the scat in the shade aged in comparison to the scat in the sun. In all the tests I ran, the scat in the sun seemed to be baked into its shape and relatively resilient to falling apart. However, scats placed in the shade stayed moist and were more easily fed upon by beetles and other insects. The moisture also allowed them to stay soft which resulted in faster decomposition.
So What Does This Mean?
This basically means that scat aging is really tough. I take comfort though in something I learned about the San in the Kalahari Desert. They are some of the last people to practice persistent hunting where through a combination of excellent tracking and fitness are able to run down game until the animal collapses from exhaustion. They classify tracks into 3 basic categories: very fresh, fresh, and old.
- Very fresh: the animal is extremely close and we must approach quitely.
- Fresh: the trail is fresh enough to find the animal.
- Old: the trail is too old to follow.
There are some great tips on aging tracks in Practical Tracking: A Guide to Following Footprints and Finding Animals (Link to Amazon)
It is relatively easy to tell the age of a scat when it is extremely fresh. But as the scat ages, the difficulty in determining it’s age increases as well. This rule holds true for tracks as well.
Thoughts on this article? Feel free to comment below and I’ll do my best to respond.