Paleofeces at Eagle Cave: A Preliminary Report of Ongoing Research

**This post is the first of several that give additional details regarding some of the different analyses that are currently being conducted with material from Eagle Nest Canyon.**

Steve Black stands next to the coprolite poster at TAS.

Steve Black stands next to the coprolite poster at TAS.

By Stephen L. Black, Emily R. McCuistion, Matthew E. Larsen, and Chase W. Beck

The 2015 Ancient Southwest Texas Project excavations were the first to document paleofeces (coprolites) in Eagle Cave. During the original site excavations in the 1930s and 1960s no coprolites were reported (even though substantial amounts of paleofeces were likely encountered). Therefore, while not completely unexpected, we were pleasantly surprised when we uncovered the first coprolites.

Extreme care was taken as we excavated these fragile organic remains. Rocket bulb air puffers were used to remove sediment from around in situ specimens. After in-field photography, paleofeces specimens were point provenience with a Total Data Station and/or Structure from Motion (SfM) before being carefully removed and bagged without handling. Specimens were transported to the field laboratory in boxes or by hand to avoid crushing. Temperature extremes were avoided and bags were vented if moisture condensed in the bags.

(Left) Paleofeces in association with faunal remains. (Center) Emily McCuistion using a rocket bulb to gently poof sediment away from a coprolite. (Right) Coprolite on a rock in situ. Another is visible in the profile.

(Left) Paleofeces in association with faunal remains. (Center) Emily McCuistion using a rocket bulb to gently poof sediment away from a coprolite. (Right) Coprolite on a rock in situ. Another is visible in the profile.

Preservation

Preservation conditions of all archaeological material varied across the site. Ironically, the best observed preservation was towards the dripline, whereas the worst was towards the backwall of the shelter. This was true for all non-carbonized organic remains, not just paleofeces. However, even within the well-preserved areas of the site there is differential preservation between individual specimens.

We are still exploring why preservation changes across the site, but some factors affecting preservation became clear when a small sample of coprolites were analyzed in the lab at Texas A&M. Of these, many were fragmentary and exhibited insect bore-holes and vacuoles, suggesting gaseous release before desiccation. Upon microscopic analysis, due to the poor condition of some coprolites the pollen was poorly preserved, and degraded, folded, and torn grains prevented the completion of a standard analysis.

There are distinctive differences between a well-preserved coprolite (top) and a poorly preserved coprolite (bottom).

There are distinctive differences between a well-preserved coprolite (top) and a poorly preserved coprolite (bottom).

Distribution of Paleofeces

Over 120 coprolites were point-provenienced during the 2015 field season. The majority of these specimens were excavated from the front of the rockshelter and approximately a meter below the surface. At Eagle Cave the coprolites are mainly found in areas of discarded fire-cracked rock and plant remains (cut leaf bases and other fiber). Sometimes they are found within compacted and dry-cracked sediment, which we sampled and hypothesize may be evidence of urine-soaking.

Locations of point-provenienced paleofeces samples from Eagle Cave.

Locations of point-provenienced paleofeces samples from Eagle Cave.

Paleofeces Variation

A representative sample of Eagle Cave coprolite sizes, colors, forms, and preservation states. All coprolites are displayed to scale.

A representative sample of Eagle Cave coprolite sizes, colors, forms, and preservation states. All coprolites are displayed to scale.

SIZE

Size is affected by several conditions, including length of time since the last bowel movement and the types of food eaten. Meals based on a single type of food can result in smaller stools, though a vegetarian diet can result in a larger stool than an omnivorous diet.

SHAPE

Previous paleofeces studies have found that plump, shapely coprolites are often from a fiber/plant-heavy meal while the “loose” ones may be from an individual who had recently consumed a lot of meat. There are, however, many other reasons that one could have had fluid bowel movements including parasites, water containing algae-born toxins, plants with a laxative effect (like lechuguilla and sotol), and even an individual’s emotional state.

COLOR

Color can be indicative of diet; the darker specimens often result from meat consumption while the lighter ones can be indicative of a vegetarian and/or carbohydrate-rich meal. When dried, however, colors change. Nonetheless, it is interesting to note color variations.

Preliminary Analysis

Field Lab Observations

Botanists and faunal experts can identify large plant and animal remains within coprolites. Thorough analysis requires rehydrating the coprolite and separating it into constituent parts. Sometimes, however, macrofossils are visible on the surface. In the field lab, Emily McCuistion observed several plant and animal remains while photographing specimens. Observable in the photos to the right are a rather large bone fragment from a jackrabbit-sized creature, as well as numerous seeds, including mesquite and prickly pear.

Macrofossils observed in Eagle Cave coprolites. Clockwise from top-left: a mesquite endocarp in a coprolite fragment; jackrabbit-sized bone embedded in a coprolite; and unidentified seeds in a coprolite.

Macrofossils observed in Eagle Cave coprolites. Clockwise from top-left: a mesquite endocarp in a coprolite fragment; jackrabbit-sized bone embedded in a coprolite; and unidentified seeds in a coprolite.

Laboratory Analysis

Ten samples were sent to Texas A&M University for a preliminary study of Eagle Cave paleofeces conducted by Chase Beck. These specimens varied greatly in size, completeness, and preservation. When conducting the analysis of the ten specimens, some contained no coprolitic material, some contained mixed coprolitic and non-coprolitic material and some seemed to be multiple broken piece of coprolites which could not be re-assembeled into a whole.

Microfossils observed in Eagle Cave coprolites (from left): unknown Liliaceae phytolith; sotol phytolith; and an unidentified phytolith.

Microfossils observed in Eagle Cave coprolites (from left): unknown Liliaceae phytolith; sotol phytolith; and an unidentified phytolith.

Five specimens were selected for further analysis. These were hydrated and sieved, and then the material was separated. While the coprolites had some evidence of bone fragments, there was no hair. The majority of material in the coprolites was botanical in nature. Seeds, pollen, calcium oxalate crystals, druse crystals, plant fibers, and phytoliths were all observed. Sotol was the most common pollen grain observed, but other taxa were also present. The presence of calcium oxalate and druse crystals has been linked in the past to the consumption of prickly pear cactus pads. Some of the phytoliths observed are associated with various grass species (Poaceae). The stylus phytoliths are likely sotol (Dasylirion spp.) or agave (Agave spp.). The seeds observed are tentatively identified as sumac (Rhus spp., likely Rhus virens).

Microfossils observed in Eagle Cave coprolites (from top): calcium oxalate crystals found abundantly in prickly pear cactus; stylus phytolith indicative of lechuguilla or sotol; and raphide crystals common in both sotol and lechuguilla.

Microfossils observed in Eagle Cave coprolites (from top): calcium oxalate crystals found abundantly in prickly pear cactus; stylus phytolith indicative of lechuguilla or sotol; and raphide crystals common in both sotol and lechuguilla.

Future Study

Matthew Larsen uses sign language to indicate he has discovered another coprolite.

Matthew Larsen uses sign language to indicate he has discovered another coprolite.

Avenues of future analysis include studying macrofossils, pollen, phytoliths, parasites, DNA, radiocarbon dating, and comparison studies with paleofeces from other sites, such as Hinds Cave.

Although the first samples proved too degraded for full analysis, hope remains that DNA may provide more in-depth information. Better preserved samples may be more conducive to future full analysis as well.

The oldest units opened at the end of the 2015 field season are showing some excellent preservation and there are high hopes for more coprolites in the 2016 field season.

A full PDF version of the poster is available here: Blacketal_TAS2015_Paleofeces

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2 thoughts on “Paleofeces at Eagle Cave: A Preliminary Report of Ongoing Research

  1. You freaks–this is the best reporting of coprolite field research I have ever read. I’m struck by the concentration of specimens in the south end of the shelter. A couple of things:
    A. I’ve been told verbally, probably more than once, that Eagle would have been a great winter shelter. It’s shielded from the prevailing winter air masses from the northwest, but the winds still blow down the canyon. And the whole shelter receives the warming morning sun on clear days. The breezes remove latrine odor down-canyon if located in the southern end, as it is. If large predators or enemy groups want to follow the scent trail upwind, they have some of the roughest terrain to overcome, and the twists and turns of the canyon walls would quickly dissipate the scent anyway. The gentle slope immediately south of the shelter, up to the Skiles Ranch headquarters cuts against this idea, but it has been my experience that one has to know exactly where the rock shelter lies before using that slope and trail, and scent wouldn’t guide an enemy to the head of that trail.
    B. Ethnographies of Plains and Great Basin groups, much, much, later than your folks, describe war chiefs, camp chiefs, and travel chiefs. Camp chiefs had the authority to assign tenting areas and fair access to water and other resources. You get the picture. Could the Eagle southern latrine be a remnant of a defined facility and part of an intentional community layout? If its use was defined by a community ordinance, then the hypothesis is at least partially testable: you have five or six point-plotted specimens in the central area of the shelter away from the southern latrine. Given the hypothesized community ordinance, these outlaw coprolites may have been the poops of ill adults and babies who couldn’t make it to the latrine or hadn’t been toilet-trained yet. You have a photographic record of coprolite types and shapes. There is support for the hypothesis if the outlaw coprolites are predominantly those types indicating gastric distress–low mass/distorted shape/baby poop/diarrheic. Small sample size is a problem we have with us always.

    later.

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