Can wild surges spawn Umbra Aniimo?

A chance is all it is, so treat nurturing as something you do steadily rather than something you do once expecting a result. What you should not do is save your best offerings for it. The quality of the items you hand over during ecosystem nurturing no longer decides the quality of the surge that follows, so feeding in higher grade items buys you nothing. Offer what you have and keep going.

The payoff for actually getting one is large. Every Umbrawl Aniimo, the same thing people call Umbra Aniimo, is guaranteed perfect potential stats. There is no roll to lose on. You spot them by their coloration, which is distinct and reads as a Darkler appearance, so a surge worth stopping for looks different from a surge that is just a crowd of wild spawns.

Ordinary surge spawns still deserve a look. Wild spawn rates for Aniimo with 9/9 and 10/10 potential have been increased, so the non-Umbra creatures coming out of a surge are more likely than they used to be to be worth keeping. Before you register or release anything back at camp, check its Alpha status, whether it is a weather or special form, and its potential grade. Releasing is not something you get to undo.

What surges will not give you

Dark forms are a separate track. Darklers and the Umbrabow form come exclusively through Egg Heist, and no amount of nurturing will produce them in the wild. Egg Heist is also where accumulated currency can be exchanged directly for an Umbrabow egg, which is the one route there that does not depend on chance. If a dark form is what you are after, surges are the wrong system to grind.

Not settled: The chance of a surge producing Umbra Aniimo is not given as a rate, and with item quality no longer feeding into surge quality there is no known way to push those odds up.