Smooth greensnakes, small non-venomous reptiles native to Illinois and the Midwest, face mounting threats in the Chicago area, according to a new study conducted by Allison Sacerdote-Velat, curator of biology and herpetology at the Peggy Notebaert Nature Museum. While habitat loss due to urban development has long been recognized as a major factor in their decline, the research reveals additional challenges related to environmental pollution and emerging diseases.
The study highlights that toxins from polluted soils, particularly heavy metals such as arsenic, copper, iron, and lead, are contaminating the eggs of smooth greensnakes. These metals can originate from the soil itself or be transmitted from mother snakes to their offspring during sensitive developmental stages. The presence of these contaminants may reduce egg survival rates and increase vulnerability to disease.
Beyond chemical threats, the research identifies fungal infections affecting local smooth greensnake populations. One pathogen, Ophidiomyces ophiodiicola, known to cause snake fungal disease, was detected in samples collected from Cook, DuPage, and Lake counties. Although many infected snakes appeared asymptomatic, concerns remain about potential impacts on survival, especially given the fungus’s severe effects on other species such as the Eastern Massasauga rattlesnake, which is nearly extirpated in the region. Scott Ballard, a herpetologist with the Illinois Department of Natural Resources, called the fungal presence “one more conservation concern” for the species.
The study also uncovered a second emerging pathogen causing more evident symptoms, though details about this disease were not specified. The interplay of habitat fragmentation, pollution, and disease underscores the complex threats facing smooth greensnakes in fragmented natural areas around Chicago.
Despite these challenges, the study offers some encouraging findings. Researchers documented a persistent population of smooth greensnakes in an urban park on the Southeast Side of Chicago, a site with a history of industrial pollution and ecological restoration efforts dating back to the mid-20th century. While population density has declined and a male-biased sex ratio was observed—conditions that may complicate reproduction—this persistence suggests some resilience.
Ongoing conservation efforts include a reintroduction program led in part by Sacerdote-Velat. Since last year, over 2,000 smooth greensnake eggs have been incubated and hatched under controlled conditions. More than 2,000 juveniles have been released into wilderness areas in DuPage and Lake counties to bolster or reestablish local populations, with further releases planned this summer.
Smooth greensnakes, known for their bright green coloration and small size, play an integral role in local ecosystems by preying on insects and serving as food for other wildlife. Advocates emphasize that the loss of such species diminishes biodiversity, which can have broader ecological consequences. Efforts to gain state-level threatened status for the species are underway but currently await additional data to meet regulatory requirements.