my best guess (full speculation so take this with an enormous grain of salt) is that the palos-sag valley region has a really high amount of contiguous remnant woodland1 that gets a good amount of restoration attention2. it accounts for about 32,000 of cook county's 70,000 acres of forest preserve and is, for the most part, only fragmented by 2 lane roads. lots of glacial moraine topography that's unusual for the region, as well as a lot of sloughs and ephemeral ponds3 that newts rely on for their life cycle4. that could provide breeding reservoirs for the newts observed in the largely residential areas surrounding the preserves.
the other possibility is that there's just more people out looking for newts there!
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"remnant" i.e. undisturbed by farming or logging, has relatively the same sort of soil profile and hydrology as it did before colonization by europeans
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see here for cook county's prescribed burn reports and here for a burn map of the state
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ponds that fill and dry seasonally. important amphibian habitat with the caveat that invasive buckthorn (Rhamnus spp) exudes an allelochemical into the soil and nearby water called emodin that's carcinogenic and teratogenic (causes cancer and disrupts development), so it's critical that areas with these ponds have aggressive buckthorn removal
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unlike most other salamanders, newts become aquatic as adults
this makes me think there's just a concerted effort to observe salamanders between 47th-159th and lemont rd-harlem ave. next time i see her i'll ask my coworker who used to be at the nature center down there if she knows anything about it
