Smooth greensnakes — a tiny, non-venomous reptile native to Illinois and Midwestern prairies — were already known to be in trouble in the Chicago region and beyond, with their numbers believed to be way down as habitats shrink amid development and other human activities.
But a recent study by a scientist with the Peggy Notebaert Nature Museum found other local threats to the snakes that could further impact their survival and health in the area and elsewhere:
- Toxins derived from polluted soil are seeping into their eggs.
- Fungal infections that have been affecting other types of snakes are now being confirmed in the smooth greensnakes, which can measure up to two feet in length and display a brilliant green coloration when older.
“We have learned that post-industrial land use history, proximity to transportation infrastructure, and proximity to intensive agriculture exposes the remaining populations to heavy metals during a sensitive developmental period for recruitment,” according to the study by Allison Sacerdote-Velat, curator of biology and herpetology at the Lincoln Park museum.
“Persistence of these pollution sources may impact egg survival rates, and disease susceptibility.”
The heavy metals, considered toxic in high concentrations, include arsenic, copper, iron and lead.
While some of the heavy metals appear to come directly from the soil, some also may be passed along from mother snakes to the eggs, the study found.
The study also found “that despite habitat fragmentation and barriers to snake movement” — the smooth greensnakes seem to mostly exist in patches of disconnected natural spaces in the area — “the presence of emerging fungal pathogens is affecting… populations regionwide.”
One of them — Ophidiomyces ophiodiicola — was found in smooth greensnakes in sample areas in Cook, DuPage and Lake counties, though the creatures were often asymptomatic.
“We’re trying to understand whether or not this is going to impact their survival,” Sacerdote-Velat says. At least for now, she says, it apparently “doesn’t impact them the same way” as with some other snakes, including the Eastern Massasauga rattlesnake that’s indigenous to Illinois and may still have scattered populations in the Chicago area, though Sacerdote-Velat believes “I think they’re pretty much gone” locally.
The infection, which can create skin lesions and lessen immunity, often proves fatal for the Eastern Massasauga.
Garter snakes are also susceptible.
Referring to the impact of the fungus on the smooth greensnakes, Scott Ballard of the Illinois Department of Natural Resources says: “It’s one more conservation concern we have for that species.”
Meantime, the study also found “a second emerging pathogen” affecting the snakes that is more symptomatic.
The findings could help “guide future conservation projects for the smooth greensnake,” the study says. And they may help inform how the snake is reintroduced into certain grassy areas in the suburbs, as has been done for more than a decade with Sacerdote-Velat a key part of that effort.
As of last year, more than 2,000 smooth greensnake eggs have been “incubated and hatched,” with 229 released in Illinois when they hit 10 months old and more than 1,800 released as hatchlings, Sacerdote-Velat said.
Most of the snakes were released into wilderness areas in DuPage and Lake counties, and more are expected to be released this summer.
“They are either released to supplement existing populations” or as part of an effort to reintroduce them into an area where they no longer exist, Sacerdote-Velat said.
A more positive finding of the study is that the snakes were found to still be living at a Southeast Side park described as “an urban, post-industrial site” where the species was studied in 1945.
“It was reassuring to find that a population of smooth greensnakes still persisted in the site 80 years later, despite heavy industrial pollution and subsequent restoration,” the study noted, while also finding “the density of snakes declined” and the gender now skews “heavily male,” which could present obvious problems for reproduction.
What’s more, the “soils and eggshells in the site had the greatest concentration of lead of any site” studied.
Such snakes can be important parts of ecosystems, as they feed on insects, and also serve as meals for other wildlife.
“Any time you’re losing a species you’re losing biodiversity,” with biodiversity translating into a healthier environment for wildlife — and humans, says Ballard, who as a herpetologist studies reptiles and amphibians.
Beyond that, says Kathyrn McCabe of the Lake County Forest Preserves, smooth greensnakes add to the beauty of our outdoors, saying: “Honestly, they’re adorable really, super cute.”
A petition has asked state wildlife officials to declare the smooth greensnakes “threatened” in Illinois, which afford them more legal protections, but more data was determined to be needed.