Pellet Like it is: Getting to Know Glacier's Goats

By Kelsey Cronin

Mountain goats utilize salts and minerals (calcium, potassium, magnesium, sodium, and phosphorus) found in eroding cliff faces to correct their chemical balance from all the succulent green vegetation they consume each spring.

NPS/Kristin Vinduska

Few animals are as emblematic of the uniqueness of Glacier National Park’s rugged alpine ecosystem as the mountain goat. Since 2008, the Crown of the Continent Research Learning Center’s Citizen Science Program has enlisted the assistance of trained volunteers to monitor the presence and distribution of this charismatic ungulate in Glacier. By recording the number of mountain goats observed at study sites, volunteers help build an invaluable long-term record of goat status within the park.

Concerningly, recent analysis of citizen science mountain goat trend monitoring data collected between 2008-2019 revealed a population decline of at least 30% (median 45%, range 32%-57%) with most of the decline occurring between 2008 and 2015. This preliminary analysis alerted park biologists to potential vulnerabilities in the population. However, without additional information about the specific ways the population is changing, it would be difficult to infer the overall risk to the persistence of mountain goats in Glacier. Further investigation is needed, but how can biologists gather more data from a species so sparse and difficult-to-reach?

The answer lies not in studying the mountain goats themselves, but by analyzing something they leave behind: their poop. Unsavory though it may seem, scientists can extract a wealth of information about a mammal’s diet and genetics by analyzing the DNA left behind in the skin cells attached to the goat’s poop, which scientists refer to as “pellets”. DNA analysis of pellets has the benefit of being minimally invasive to the animal, allowing researchers to sample the population while avoiding more stressful methods of wildlife surveying such as animal capture.

In 2019, citizen scientists, park biologists, and collaborators from the USGS launched a pilot study to collect mountain goat pellets from Glacier’s goat habitats. In this first season, biologists wanted to test the efficacy of pellet analysis as a method for identifying individual goats in Glacier. After arming mountain climbers, backcountry skiers, and intrepid hikers with collection envelopes and ethanol-filled vials, scientists were able to gather a total of 110 pellet samples as part of the pilot study. The results were positive: biologists were able to extract complete genotypes for 60 of the 110 samples, a success rate similarly reported in other wildlife studies.

With the ability to pair the genetic identity of an individual mountain goat to its geographic location, scientists can answer questions impossible to study through observation alone. For example, looking at the genetic relatedness of goats within a geographic area can show the amount of variation and diversity within family units. It can also help us understand whether Glacier’s goat population is large and interconnected, or if it is made up of smaller isolated sub-groups. Adding this important context on mountain goat population structure can enhance biologists’ understanding of the significance of observed declines.

Genetic structure isn’t the only important information that can be gleaned from pellet analysis. By examining DNA from traces of plant material left in the pellets, managers can learn about the diet of goats and thus, the types of plant communities goats utilize throughout the summer. This knowledge might become useful in studying goat habitat selection in the face of threats such as climate change and human disturbance. Additionally, when samples are collected fresh and remain well-preserved, they can be analyzed for the presence of corticosteroids, also known as stress hormones. The hormones present in mountain goats could potentially lead researchers to understand how stress might vary in different goat habitats and whether goats are more stressed in areas with high levels of human visitation.

After the success of the pilot study to identify mountain goats on an individual level, the USGS and the Citizen Science program partnered and received additional funding to increase the scope and reach of the project. In 2022, within the Citizen Science program, staff recruited and trained 30 volunteers in the proper identification and collection of mountain goat pellets. The process isn’t easy, as accessing a collection site can be a challenging first step. Although mountain goat pellets may occasionally be found along hiking trails, most pellets can only be found in the steep, mountainous terrain that goats inhabit. This means the volunteer often must leave established hiking trails, ascending higher-elevation peaks and passes to seek out goat pellet hot spots. Next, after locating pellets, the volunteer must avoid contamination of other DNA touching the pellet sample during collection. To maintain sample integrity, the volunteer uses tweezers, gloves, or rocks held like scoops to gather pellets into collection vials.

Concluding an enormous effort throughout the season, volunteers in Glacier used these methods to collect 209 pellet samples across some of the most remote areas of the park. Sample-collection treks often took days of hiking, bushwhacking, and climbing to successfully locate pellets. Park staff will be sending the hard-earned samples off to a laboratory for analysis this fall, after which point USGS researchers will undertake rigorous examination of the results. The mountain goat is no stranger to hanging on to unstable ground, but the challenges ahead may present uncharted terrain. Hopefully, goat pellets collected through this study will inform park staff about the ways the population is changing, allowing managers to make decisions that will allow this iconic species to persist.