A bobcat traveling atop a downed tree. Photo courtesy ©Max Allen.

May 1, 2024

The Bobcat Chronicles: How the public helped scientists track bobcats expanding across Illinois

A map of the counties of Illinois, and the counties slowly fill will green to show the recolonization of bobcats into habitats in Illinois.
Map showing the probability of county-level occupancy for bobcats in Illinois, where 1.0 means 100 percent probability that the county is occupied. Map ©Javan Bauder.

Bobcats are a charismatic species that are shrouded in mystery; a species that challenges and captivates wildlife enthusiasts. Beyond their sleek, elusive nature and striking physical features—characterized by tufted ears, and the bobbed tail that gives them their name—bobcats possess a mysterious charm rooted in their adaptability, hunting skills and elusive behaviors. Their silent movements through the underbrush and ability to vanish into the landscape prompt a sense of awe and respect among those fortunate enough to catch a fleeting glimpse and make seeing a bobcat in the wild a rare and rewarding experience. It is this elusive quality that give bobcats an almost ghost-like presence, leaving an indelible mark on the imagination of those who seek to witness its elusive beauty.

Bobcats were rare in Illinois for many years due to habitat loss and unregulated hunting and trapping. Bobcats were listed as a ‘threatened’ species in 1977 and remained scarce into the 1980s. Sightings became more common at the end of the 1990s, especially in southern Illinois and along the Kaskaskia River basin, the Illinois River valley and in northwestern Illinois.

Despite the difficulty of spotting bobcats, the Illinois Department of Natural Resources (IDNR) relied on sightings by the public to document the continued expansion of bobcats in Illinois in a recent study published in Landscape Ecology led by Dr. Javan Bauder. In the quest to better understand animal distribution in Illinois, IDNR and researchers often rely on volunteer members of the public to record and report their observations of rare and elusive species. This publicly sourced data on wildlife (often called citizen or community science) often play a pivotal role in expanding our understanding of wildlife populations and distributions. Using data from 2001 to 2018, Dr. Bauder and his team documented how bobcats have expanded their range from their southern strongholds into the rest of the state.

As Dr. Bauder related, “Community science data has incredible potential to transform how wildlife managers study and conserve wildlife populations. Scientists can only collect so much data and our ability to monitor and study wildlife is always constrained by limited resources. Public participation in collection of wildlife data exponentially expands our ability to collect information on where wildlife occur and how they respond to current and future landscapes and environments. People who participate in collecting community wildlife programs, like Illinois’ archery deer hunter surveys, are helping to manage and conserve, as well as enjoy, our wildlife resources.”

The low densities and cryptic behaviors of many animals, such as bobcats, make them challenging subjects for traditional research methods. Citizen scientists, by actively participating in data collection, provide a wealth of valuable information, often covering vast time periods and geographical scales that would be logistically challenging for researchers alone. IDNR, as custodians of the natural environment in Illinois, recognizes the immense value that the public brings to the table. By actively engaging with the community, IDNR fosters a sense of collective responsibility for the well-being of the local environment.

As noted by Stan McTaggart, the IDNR Wildlife Diversity Program Manager, “Many hunters and trappers enjoy the opportunity to help us monitor wildlife trends by reporting what they see in their areas every year. This information not only enhances our understanding of ecological dynamics but also cultivates a commitment to appreciate, manage and protect the wildlife that we all share.”

A portrait of a bobcat with tan, brown fur and black markings. In the background are pine boughs.
A portrait of a bobcat in dappled light. Photo © Max Allen.

Across Illinois, bobcats have slowly been reclaiming their territory over the past few decades. Dr. Bauder and his team (of which I am one) explored their expansion in Illinois using 18 years of observations by archery deer hunters who served as dedicated participants in the study. This study demonstrates the potential of harnessing observations from the public to gain valuable insights into the distribution patterns of carnivores over extended time periods. For bobcats, it unveils a captivating narrative of a species comeback and the intricate ecological factors influencing its expansion across Illinois.

“The big take-away from our study is that bobcats have been able to successfully recolonize most of Illinois after being absent in parts of the state for many years. I think that this is all the more remarkable considering how agriculture dominates much of Illinois’ landscape and highlights the versatility of bobcats as a species,” said Dr. Bauder.

In order to estimate spatiotemporal patterns in bobcat occurrences and understand the factors influencing their recolonization, Dr. Bauder employed sophisticated Bayesian spatial and non-spatial multi-scale dynamic occupancy models. These statistical models revealed a substantial increase in bobcat distribution in Illinois counties over time. When estimating the probability that a county was occupied (called “occupancy” by scientists), bobcats essentially doubled – increasing from being found in 43 percent of counties (mainly in southwestern counties) to 0.83 percent (nearly throughout the state) over the course of the study.

The combination of thousands of observations from hunters and these space age statistical models also allowed Dr. Bauder to unravel the factors influencing their recolonization over time. Surprisingly, the study found that county-level landscape features did not have as large effects as expected on the recolonization of bobcats. The primary effects on occupancy and the probability of colonizing a new county the following year were linked to the availability of forest and wetland habitat.

Another landscape feature that was important were river corridors, especially those along the Mississippi and Illinois rivers. While the large rivers may have initially blocked bobcats from immigrating easily into Illinois, the corridors themselves emerged as vital travel routes and sanctuaries for bobcats. These sinuous ribbons of riparian habitats provide a verdant pathway that fosters biodiversity by connecting fragmented habitats and enabling the movement of wildlife across different regions.

When asked what surprised him the most about his findings, Dr. Bauder replied “I think the biggest surprise was how clearly we were able to see bobcats expand their distribution in Illinois. In 2001, bobcats were most likely to be seen in southern Illinois. Over the next 18 years, our model showed bobcats steadily expanding within southern Illinois and north along the Mississippi and Illinois rivers. By 2018, our model predicted that bobcats were widespread throughout western and southern Illinois. Other parameters estimated by our model also indicated bobcat expansion within Illinois, such as an increasing probability of hunters seeing or detecting bobcats. We were also surprised to see that landscape features, such as the amount of forest or grassland in a county, did not have as strong an influence on bobcat recolonization as we expected although our model did indicate that bobcats were positively associated with greater amounts of forest and grassland within a county.”

This compelling research underscores the power of community science in unraveling the mysteries of nature. Interested readers have the opportunity to join other members of the public by uploading observations to platforms for community-generated science such as iNaturalist.com and eBird.com.

This research on bobcats was made possible only through the participation of the public, as Dr. Bauder noted, “The numbers of hunters participating in these surveys each year was pretty remarkable. We averaged over 1,600 hunters per year participating and had as many as 2,700 hunters participate during a single year.”

The return of the bobcat to Illinois is a testament to the intricate dance between wildlife and environment and unveiled through the collaborative effort of the public and professional researchers.

Max Allen is a carnivore ecologist with the University of Illinois. His research focuses on the ecology and behavior of the carnivore guild around the world, with a focus on understanding ecological interactions of carnivores for applied conservation and management.

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