Last updated: April 18, 2022
- Anna Willoughby
- Zoe Boyles (CURO Summer 2019)
- John Mark Simmons (CURO Spring 2019)
- Caroline Aikens (CURO/ECOL4960R Summer 2020)
- Sydney Speir (CURO/ECOL4960R Spring 2021)
- CJ Jones (CURO/BIO4960R Spring 2022, Summer Foundation Fellowship, Altizer Lab Student Worker Fall 2022)
- Logan Owens (Altizer Lab Student Worker Fall 2022/Summer 2023; CURO/ECOL4960R Spring 2023)
- Summit St. John (Altizer Lab Student Worker Fall 2023)
For wildlife to succeed in human-dominated landscapes, they must acclimate to changes in resources and disturbances. Mesocarnivores like raccoons and foxes are small predators that can reproduce more frequently and aggregate in larger groups than apex predators[1]. This mammalian guild often thrives in human environments due to both their omnivory and the loss of their larger-bodied predators, a process known as ‘mesopredator release’[2]. Recent studies describe the flexible strategies mesocarnivores use in anthropogenic habitats, such as changing their activity patterns to avoid humans or expanding their diet to include human-associated foods like trash and domestic pets[3,4]. Food web dynamics in human environments are expected to dramatically shift, with mesocarnivores at the top trophic level, fewer species interactions, and the uptake of human-associated foods. Understanding the wildlife community-level and behavioral responses to habitat changes such as urbanization can inform conservation and management policy as land development rates increase in magnitude and scale[5].
The exploitation of human environments can benefit mesocarnivores by clustering resources that both boost food access and decreases foraging movements[6]. Urban mesocarnivores frequently consume human-provided foods and exhibit distinct nutritional signatures as compared to rural populations[7,8]. Stable isotope analysis of animal tissues can reveal signals of anthropogenic diet, with human-provided foods skewed towards 13C, which is prevalent in processed foods. Another common but time-intensive method to assess diet involves identifying the macroscopic analysis fragments of digested organisms in scat. Both these methods provide incomplete mesopredator diet assessments: single elemental values or coarsely identified taxa groups (e.g., family). Scientists increasingly recognize that multiple methods, including genetic techniques, offer a more comprehensive view of predator diet diversity[9].
Large-scale camera trap studies have shown that mesocarnivores persist in urban environments by preferentially occupying the constricted natural forest habitats within the urban mosaic[10,11]. Some mesocarnivores can reside in human-built structures and may elude traditional grid-based camera surveys. Limited radio-telemetry studies of stone martens, raccoons, and other carnivores, show that building- dwelling individuals have smaller home ranges than wild counterparts[12–14]. This signals that human- built structures can be rich in resources, which could increase population densities and competitive interactions, particularly for territorial carnivores[15]. Mesocarnivores often use latrines, which are localized sites for repeated defecation, that can signal resource quality, territorial defense, or other social cues[16,17]. While rodent scat and bat guano in buildings are considered biological hazards causing diseases such as leptospirosis, histoplasmosis, and hantaviruses[18–20], mesocarnivore latrines disease status is unknown. Thus, buildings occupied by resident mesocarnivores with scat contamination may become a problematic disease interface for both mesocarnivores and humans occupying them. Some buildings can be a thermal refuge for mesocarnivores, buffering against the need for temperature regulation behaviors, and providing shelter from predators[21]. Use of these sites could therefore vary seasonally based on weather and changes in other species interactions and could further change mesocarnivore phenology. For instance, Widdows and Downs (2016) reported early breeding in structure-dwelling large-spotted genets in KwaZulu-Natal, South Africa, potentially to allow juvenile dispersal before attic temperatures become inhospitable[22]. Mesocarnivore diets are highly seasonally dependent, with individuals feasting on easily accessible resources following invertebrate emergence periods or fruiting seasons[23,24].
- How do the communities ringtails interact with, including predators, conspecifics, prey, and symbiotes, change in human-modified habitats?
This work commenced in November 2020 and is ongoing until November 2022 in Zion National Park (ZNP) and Grand Canyon National Park (GCNP). I identified sites of ringtail activity in structures (e.g., attic, crawl spaces, roofs) and in natural habitats (e.g., boulder outcrops, trails, river washes) following pilot work, using the presence of ringtail scat or tracks, and discussion with park staff. Five distinct areas were selected to ensure separate ringtail populations that do not regularly intermix based on previous radio-telemetry tracking[14; Holton pers. comm.]. These include the Zion Lodge Area, Zion Maintenance Yard Area, GC North Rim, GC Inner Canyon, and GC South Rim.
Sites are equipped with motion-activated camera traps (Bushnell Trophy) that capture 30 second videos at building sites and two picture sets at outdoor sites, with a 15-second interval between trigger events. Camera trap media are in the process of being classified to animal species through the citizen science Zooniverse portal, “Canyon Critters” ), to calculate total wildlife community diversity (e.g., birds, reptiles, terrestrial mammals), as well as diversity indices for community guilds relevant for ringtail biology: predators, competitors (e.g., skunks, gray foxes), and prey (e.g., birds, rodents). I expect for all guilds to be greater in outdoor sites compared to building sites.
Ringtail scat is collected every three months for the two-year study duration to compare seasonal shifts in diet diversity (n ~ 320 samples) and stored in ethanol and frozen. I am using traditional diet identification methods by filtering scat through 1 mm mesh to collect human-derived materials like paper and foil, as well as use morphometric traits to distinguish biological fragments (e.g., insect wing patterns, tooth cusps, seed size and structure). These methods are insufficient at fine taxonomic scales, with only 6% of scat items identifiable to species, and most classified to family. Additionally, ringtail diet can include digestible material like nectar[37]. Therefore, a major limitation in ringtail, and all omnivorous mesocarnivore, diet descriptions is a bias toward organisms with identifiable features post digestion. To overcome this barrier, I will pursue metagenomic assays in collaboration with Dr. Noah Fierer at the University of Colorado Boulder using a variety of primers to target natural diet items (Ac12S for vertebrates, trnL for plants, ArthCOI for invertebrate[38]). Briefly, genomic DNA from scat will be extracted using the DNeasy PowerSoil HTP 96 Kit. The target sequence section will be amplified from each sample for subsequent indexing in a second round of PCR, and then sequenced via Illumina Miseq. Outsourcing samples to UC Boulder provides laboratory expertise, quality checks, and bioinformatics analysis. Taxonomy is assigned to each “exact sequence variant” by mapping sequences against GenBank reference data and voucher specimens, with a threshold of 90% considered a match.
Species identifications
Isotope analyses
Activity
Parasite
Dietary composition
This work requires sample and specimen collection permits from field sites (NPS, Utah DNR) and museum (NPS, LACM), in addition to animal-use oversight from UGA and NPS. All permit records are stored here.