Wildlife in Rockstar open worlds is often treated seriously. RDR2 had amazing wildlife; GTA V was lighter on wildlife presence but did feature a functioning wildlife system nonetheless. Wildlife we can actually see in GTA 6 footage has been pretty slim - understandably, because of how early we are - but every little critter we can see matters, because Rockstar typically doesn't feature animals in trailers that don't make it into the final game.
This is an incomplete list. We'll be adding to it as footage arrives. See also the Everglades region guide and the Florida Keys page for the wider region.
Confirmed by trailer footage
Alligators. Seen in Trailer 1 (briefly, on a road) and Trailer 2 (during the wetlands sequence). The model is detailed enough to suggest they actually have AI and aren't just scenery. Documented in the alligators piece.
Flamingos. Seen in some wetland frames of Trailer 2. Pink and flying in at least one frame. Unknown if they can be interacted with, or if they're just ambient scenery. Elaborated on in the flamingos piece.
Dogs. Noticeable at street level in city frames - on leashes with their owners, or roaming as strays. Expected for any city in GTA.
Pelicans and other waterfowl. Spotted flying or at rest in Keys-coded and wetland frames.
Strongly suggested but not yet confirmed
Florida panthers. The real wetlands have them, and the visual coding hints at them, but no specific scene confirms one. Plausible, just not shown.
Manatees. The water around the Keys analogue and in the wetlands would be a plausible habitat for them. No footage confirms it.
White-tailed deer. Typical inland Florida fauna. Seen in Rockstar's previous countryside environments. Could work here. No footage confirms it, though.
Sharks. The open-water shots around the Keys imply they're there. RDR2 had wildlife in the water; GTA V had sharks. Almost certain but not explicitly shown.
Sea turtles, dolphins. They make sense as coastal wildlife. Not seen in any footage.
What this tells us about the system
Wildlife captured on screen so far covers two of the game's four regions heavily (wetlands: alligators, flamingos, waterfowl; coastal: pelicans). We've seen less inland and urban wildlife. That said, it could be a function of trailer editing more than wildlife actually being absent from the game.
You can't tell much about animal AI from trailer screenshots, but the alligators' behaviour in the wetland scene is vigilant instead of docile. Red Dead Redemption 2's animal AI is the easy comparison; GTA 6's seems to be at least in the same conversation. We cover this comparison in more depth in the wildlife vs RDR2 piece.
What we don't know
The total number of species. Whether animals respond to weather. Whether animals can be hunted in any real sense (we discuss hunting separately - it's speculative). Whether the species mix differs significantly by zone, or you see the same fauna wherever it has a reasonable chance to occur.
Most questions will be answered at launch. We update this list as confirmed content is released.