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Vol. 30, No. 2

Wildlife Projects on the North Rim

Multiple organizations have partnered with the park to research the movement, migrations, and threats of a variety of inhabitants of the Grand Canyon's North Rim.

Baby Bison Grazing on the North Rim

Bison

In collaboration with the U.S. Geological Survey, the park recently wrapped up a project on how to best estimate the size of the Kaibab Plateau bison herd on Grand Canyon’s North Rim using aerial surveys and bison outfitted with tracking collars. This model will be used to estimate the herd size annually. GCC funding assisted in purchasing tracking collars and logistics to refine this model. January 2023’s pre-calving population estimate was 227, with a 95% confidence interval (Hennig & Schoenecker), which is on target with the park’s short-term reduction goals of less than 200 bison.

Recent research using the same bison outfitted with tracking collars found that the Kaibab Plateau herd is one of the few free-ranging, seasonally migratory herds. A new range map was published and made publicly available on the park website. The same tracking collars enabled staff to evaluate bison movements across the plateau. Results show that bison are responsive to hunting across the Grand Canyon National Park/Kaibab National Forest boundary. They mostly avoid the boundary, but when they do cross, usually for coveted resources such as water and salt provided by hunters, they move up to 1.2 times faster on Forest land than on Park land regardless of terrain or vegetation cover (Salganek et al. in press).

At Grand Canyon National Park, bison are only found on the North Rim on the Kaibab Plateau. Scientists know much about how bison interact with ecosystems like tall and short grass prairies but little about them in forested habitats like the Kaibab Plateau. There are concerns about the density of bison and their effects on this different ecosystem. Park staff and collaborators have researched to learn more about local effects and to monitor them over time so the herd may be managed at an ecologically sustainable size. One research project that hopes to answer some of these questions is that of Colorado State University graduate student Dana Musto, who is defending her thesis on bison grazing effects on the North Rim this year. Musto is a former Polk intern whose research at Grand Canyon National Park was funded by GCC.

Butterflies

On July 15, 2023, a special Grand Canyon Conservancy Field Institute service project on the North Rim will assist the park with butterfly counts. Participants will work with lepidopterists (entomologists specializing in studying butterflies and moths) to help monitor the pollinators. This is an excellent opportunity to be part of the scientific work that the park does to understand the butterflies of the Kaibab Plateau. Comparisons of the results across years can be used to monitor changes in butterfly populations and study the effects of weather and habitat change on butterflies. This research aims to catalog species richness and abundance of butterflies in the Grand Canyon National Park region. This cataloging effort will supplement and compare data from previous butterfly counts conducted and specimen data collected from the 1930s–1950s by John Garth.

To learn more about this service project or to sign up to participate, visit https://www.grandcanyon.org/service-based/2023-july-north-rim-butterfly-count/.

Additionally, the park is stepping up its work related to Monarch butterflies due to their status as a species of concern. Monarch butterflies (Danaus plexippus) stop at Grand Canyon along their migratory route from Canada to Mexico. It’s a critical stop providing host plants essential for monarch survival, like milkweed and other nectar-rich species. Grand Canyon National Park has established pollinator gardens at the North and South rims to increase monarch habitat and assist with monitoring. When visiting the North Rim, you’ll find a pollinator garden at the Lodge Cabins adjacent to the Visitor Center and Grand Canyon Lodge.

Every year staff tag migratory Monarch butterflies to learn more about their migration patterns in the American Southwest and to and from Grand Canyon National Park. Tagging a monarch means you first must catch it in a net. Once that is accomplished, scientists collect data like the sex, condition, location, and activity of the monarch before placing a small tag on the wing.

Kaibab Squirrels

The iconic Kaibab Squirrel (Sciurus aberti ssp. Kaibabensis), found only on the North Rim, with its all-white tail and black belly, is always an adorable site to see at Grand Canyon. But threats, including habitat loss through wildfire and logging, drought and climate change, hunting, predation, and disease, have led to a decline in its population.

There have been previously perceived Kaibab Squirrel shortages in the 1920s and 1960s that recovered without issue. But because we still do not fully understand the population and ecosystem dynamics, the current population estimates are concerning. Currently, there are no formal Federal protections for the species. Arizona Game and Fish manages them as a game species as they are hunted seasonally.

This year, the park seeks public involvement to help locate endemic Kaibab Squirrels on the North Rim. Public help documenting sightings will be extremely valuable and will inform management and direct ongoing science.

The Kaibab Squirrel is one of six subspecies of Tassel-eared Squirrels and is only found on the Kaibab Plateau. In 1965 approximately 300,000 acres of Ponderosa Pine Forest were designated as the Kaibab Squirrel Habitat National Natural Landmark (NNL) by the Secretary of the Interior. The area encompasses the northern portion of Grand Canyon National Park and the North Kaibab District of the Kaibab National Forest. The NNL designation highlights the rare and diverse biotic community in addition to the scientific and educational values contained within.

Kaibab Squirrels are strongly associated with Ponderosa Pine forests for forage and refuge. Unlike other squirrel species, they do not cache much food and remain active all winter. Depending on snow cover, these squirrels may subsist on only inner bark, while at other times, they will feed on false truffles and pine seeds. It has been suggested that there is a mutualistic relationship between Ponderosa Pine, Fungi, Kaibab Squirrels, and Northern Goshawks. Changes to one may have substantial impacts on the others. Grand Canyon National Park and the Kaibab National Forest are collaborating with ongoing management efforts and new research to discover more.
 

Author: Miranda Terwilliger

Originally Published: 06-26-2023 Last Updated: 12-08-2023