Looks like a Leopard Slug, Limax maximus, which we get here. Believe it was accidently introduced to the US.

Markings do seem to confirm "Leopard Slug" even though the size is suggested to be 4-8 inches. However, my specimen is not extended and likely still in a dormant state due to ground temps, even though on the day I spotted it the air temp was in the 60's.

Apparently not considered a serious invader in MI, MISIN - Midwest Invasive Species Network, doesn't list it. Although I guess if it showed up in your garden you might feel differently.

iNaturalist actually shows a record in the same park, or very near the same park, where I spotted my specimen.

floraluk2 Thanks for the help.

8" would be a big example at full extension. They come smaller and if not stretched out can look much like yours.

should it be reported to MSU extension service??? .. or the Ag office??

https://www.misin.msu.edu/ doesn't list Limax maximus at their site so I presume it is not on their watch list.

well.. there ALWAYS has to be a first.. maybe they will name it after y.. lol ..

ken

I don't know how to report to "MSU extension service??? .. or the Ag office??", you didn't provide a link or email address so it has been reported to "West Michigan Conservation Network". It cannot be reported to "Midwest Invasive Species Information Network (MISIN)" because the species is not listed at their website, hence, there is no "page" or "form" available to report it, in order to report it the species has to be pulled from a list. I know this from experience because I am registered there and have made reports before.