Introduction

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Long-Term Monitoring: The BLM has treated areas with herbicide since the 1980s, giving researchers the rare opportunity to research banner-tailed kangaroo rats on a long time-scale.

Banner-tailed kangaroo rats (Dipodomys spectabilis) are one of three kangaroo rat species in New Mexico. They inhabit the grasslands in New Mexico’s Chihuahuan Desert and are important in maintaining the health of grassland ecosystems because they are a keystone species that improve habitat for other grassland species. They are also considered ecosystem engineers because they alter vegetation structure structure
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Learn more about structure by constructing large mounds and selectively eating and spreading the seeds of certain species. The Chihuahuan Desert’s history of overgrazing, reduced fire frequency, and drought has caused shrub encroachment by creosote bush (Larrea tridentata) and honey mesquite (Prosopis glandulosa), and loss of the native grasses and vegetation structure critical for kangaroo rat survival. Not only does this landscape change threaten banner-tailed kangaroo rat populations that are classified as Near Threatened by the IUCN Red List, but the decline in banner-tailed kangaroo rat populations further threatens grassland health. 

In 2005, the Bureau of Land Management (BLM) initiated the Restore New Mexico (RNM) Collaborative Monitoring Program with the help of partners to restore the grasslands and grassland-dependent wildlife in New Mexico’s Chihuahuan Desert by applying shrub-specific herbicide treatments. Researchers from University of Illinois, Hobart and William Smith Colleges, USDA Agricultural Research Service, and New Mexico State University are leveraging these ongoing treatments specifically in creosote bush-invaded areas in partnership with the BLM to determine if and why banner-tailed kangaroo rats returned to treated areas.

Key Issues Addressed

Banner-tailed kangaroo rat populations have declined due to ongoing shrub encroachment in the Chihuahuan Desert, which is caused by the interactions between overgrazing, fire suppression, and drought. Furthermore, shrubs may be favored by climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.

Learn more about climate change due to higher drought tolerance than grasses. Shrub decline and grass recovery following herbicide treatment varies across treatment sites depending on environmental conditions after treatment, and site characteristics including soil type. 

Banner-tailed kangaroo rat populations face small- and large-scale constraints that affect their ability to increase on treated areas. Soil type and presence of abandoned mounds are important small-scale constraints. Sandy soils do not have enough structure to hold new mounds together, making it unlikely for banner-tailed kangaroo rats to respond to treatments on this soil type. Banner-tailed kangaroo rats also prefer to reuse abandoned mounds, and therefore are less likely to return to areas without them.

The distance between areas treated for shrub removal is an important large-scale constraint because low connectivity between treated areas and existing banner-tailed kangaroo rat populations limits their return to grasslands. Banner-tailed kangaroo rats have low dispersal ability, so they require high connectivity between old, grass-dominated and newly treated areas. There can be a 10-year time lag or longer between treatment and return of banner-tailed kangaroo rats, which implies that the restoration response of banner-tailed kangaroo rats may be contingent on factors other than shrub cover alone. 

Banner-tailed kangaroo rats also have the potential to experience genetic founder effects if only a small number of individuals disperse from a source population. Genetic founder effects occur when a subset of a population establishes a new population, resulting in decreased genetic variation. 

Project Goals

• Assess the importance and connection between small- and large-scale constraints on banner-tailed kangaroo rat response to grassland restoration and the amount of time it takes for banner-tailed kangaroo rats to return to treated areas
• Gain a deeper understanding of the interactions between banner-tailed kangaroo rats and their environment as keystone species and ecosystem engineers: these interactions include mound construction, selective granivory, and interactions with other species
• Communicate the importance of banner-tailed kangaroo rats as general indicators of grassland restoration success to project partners
• Assess potential for genetic founder effects as banner-tailed kangaroo rats return to treated sites: this occurs when a subset of a population establishes a new population, resulting in decreased genetic variation.

Project Highlights

• Ecosystem Engineers: Researchers found that banner-tailed kangaroo rats are important for the functioning of the overall grassland ecosystem. Their mounds are large and evenly spread out due to territorial behavior, which helps create habitat heterogeneity, or diversity, in grassland habitats. Further heterogeneity is created through selective herbivory, which occurs when banner-tailed kangaroo rats eat certain seeds and grasses over others. Habitat heterogeneity can allow more species to coexist in the same area, which increases the diversity of species.
• Keystone Species: Researchers found that banner-tailed kangaroo rats are indicators of restoration success because of their interactions with other species. Banner-tailed kangaroo rat mounds are important in providing food and shelter to animals including cottontail rabbits, grassland lizards, and harvester ants. For example, researchers found that mounds serve as shelter for lizards and that lizard populations are lower at restoration sites with fewer mounds.
• Connectivity and Treatment Age: Researchers found that the density of banner-tailed kangaroo rat populations is dependent on grassland connectivity and treatment age. The highest density was found at older treated areas with high connectivity to other treated areas and source populations of banner-tailed kangaroo rats, meaning that banner-tailed kangaroo rat populations will benefit from increased connectivity over time. Further, researchers found no evidence of genetic founder effects among newly settled populations of banner-tailed kangaroo rats despite limited dispersal ability.
• Partnerships: Researchers conducted this research on banner-tailed kangaroo rats in partnership with the BLM’s ongoing RNM project. Because of this partnership, they were able to establish plots for long-term monitoring and communicate their findings directly to the BLM to advise general RNM success.

Lessons Learned

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Designing this experiment with a multi-scale perspective was important to get a complete understanding of how RNM herbicide treatments are influencing banner-tailed kangaroo rat populations. Researchers observed banner-tailed kangaroo rats on a range of spatial and temporal scales. They looked at small- and large-scale constraints such as connectivity on the ability of banner-tailed kangaroo rats to return to treated areas and observed banner-tailed kangaroo rat populations responses at restoration sites that were up to 29 years old. Without long-term monitoring, researchers would not have realized the 10-year time lag, or longer, between treatment and return of banner-tailed kangaroo rats.

Researchers had to reframe what successful restoration looks like. Researchers knew that these grasslands would not fully return to their original condition because this area has experienced shrub encroachment for a long period of time and will continue to experience it due to climate change. Most treated areas have some remaining shrub cover, which has created a savannah habitat instead of a grassland habitat. Researchers changed their outlook of successful restoration to accept a savannah habitat, as long as banner-tailed kangaroo rats (and other focal species) can successfully return to the habitat. 

It was important for researchers to have meaningful connections and engagement with the BLM, which allowed them to conduct their research alongside the BLM’s pre-existing shrub treatment program. Researchers found people with shared interests within this BLM project to form this partnership. They were also able to inform BLM managers in this shrub treatment program on the importance of banner-tailed kangaroo rats as indicators of the program’s relative success.

Next Steps

• Research potential behavioral constraints affecting the return of banner-tailed kangaroo rats to treated areas including whether individuals with particular personalities might be more willing to disperse across a shrub-dominated landscape
• Conduct research on the potential effects of treated shrub “skeletons” on the return of banner-tailed kangaroo rats to treated areas: shrub skeletons are the remains of dead shrubs that persist for years due to slow decomposition.
• Make future projections on how climate change could affect banner-tailed kangaroo rat distribution in the Chihuahuan Desert

Funding Partners

• USDA, National Institute of Food and Agriculture, Managed Ecosystems Program (2010 - 2014)
• USDA, National Institute of Food and Agriculture, Agroecosystem Management Program (2016 – 2021)
• NSF, Jornada Basin Long-Term Ecological Research Program (DEB 1235828 and DEB 1832194)

Resources

• Cosentino, B., et al. (2014). “Constraints and time lags for recovery of a keystone species (Dipodomys spectabilis) after landscape restoration.” Landscape Ecology 29: 665-675.
• Cosentino, B.,et al. (2015). “Rapid genetic restoration of a keystone species exhibiting delayed demographic response.” Molecular Ecology 24: 6120-6133.
• Wagnon, C., Schooley, R., and Cosentino B. (2020) Shrub encroachment creates a dynamic landscape of fear for desert lagomorphs via multiple pathways.” Ecosphere 11(9): 1-16.
• Bureau of Land Management, Las Cruces District Office

Contacts

• Robert Schooley, University of Illinois: schooley@illinois.edu
• Bradley Cosentino, Hobart and William Smith Colleges: cosentino@hws.edu

CART Lead Author

• Brianna Flood, CART Intern, Northern Arizona University

Suggested Citation

Flood, B., M. (2022). “Restore New Mexico: Effects of Grassland Restoration on Banner-Tailed Kangaroo Rats” CART. Retrieved from https://www.fws.gov/project/grassland-restoration-effects-kangaroo-bats.