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Coyotes Increased Across Illinois Over Four Decades, but County Trends Varied

Wild coyote at Meridian Business Campus in Aurora, Illinois
Conservation · Population & status

Coyotes (Canis latrans) increased across Illinois, USA over the four decades covered by long-running wildlife surveys, although local trends differed substantially among counties and periods. The conclusion comes from an analysis that combined four independent measures of relative abundance collected between 1980 and 2023.

The four datasets came from nocturnal spotlight counts, observations by archery deer hunters, trapper harvest records and hunter harvest records. None provides a direct count of the total coyote population. Each instead gives an index of how common coyotes appeared through a particular type of monitoring, and each is influenced differently by observer effort and detection.

Combining surveys separated population signal from survey noise

That mattered when the datasets were analysed separately. Only the spotlight survey produced clear evidence of long-term statewide population growth on its own, even though it also had the greatest estimated observation error. The archery, trapper and hunter datasets were individually too uncertain to show a consistent long-term increase.

When all four datasets were analysed together in an integrated state-space model, the statewide pattern became clearer. A state-space model separates variation caused by observation error from the underlying population process, allowing the surveys to contribute information without treating their raw counts as directly equivalent: the combined estimate showed positive long-term population growth and was more precise than estimates from any single survey. The authors argue that combining independent data sources can reduce the influence of biases specific to one monitoring method and reveal a population signal that is difficult to detect from any one dataset alone.

County trends shifted between decades

The statewide increase did not occur uniformly. County-level estimates showed periods of both growth and decline, and the locations of those changes shifted between decades. The researchers tested several ecological variables but could not identify clear causes for the fine-scale patterns from the available data. Human-caused mortality, prey availability and habitat quality are discussed as possible contributors, not as effects demonstrated by the study.

The study therefore supports a long-term increase in Illinois coyotes at the statewide scale while showing that local populations can follow different trajectories. The authors recommend finer-scale demographic work and continued use of both harvest-based and harvest-independent monitoring to understand those local changes.

Sources and image credit

  1. Scopel et al. (2026), Mammal Research — Improving inferences from coyote (Canis latrans) surveys across Illinois using integrated state-space modelsPrimary peer-reviewed open-access study, published and version of record 24 August 2026. Integrated four Illinois relative-abundance datasets from 1980–2023. The integrated state-space model indicated long-term positive statewide coyote population growth with greater precision than individual survey models, while county-level trends varied across space and time.

Image: Joseph Gage — wild coyote (Canis latrans) at Meridian Business Campus, Aurora, Illinois, photographed 8 September 2021; Wikimedia Commons/Flickr. Representative Illinois image, not an animal from the survey datasets. · CC BY-SA 2.0 · Source

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