What’s taking place here and why?

Dry land otter set...

shellfish oil poured in a hole and buried and a fox is digging

Something was buried there weeks ago but it wasn’t shellfish oil and yes, foxes are digging there.

Turtle eggs....snapping, mud, or slider's eggs.

Little chilly for turtle eggs.

Not when they were layed by the turtle.....a few months ago.

That could be true, no shells around like normally is when a nest is raided though.

Some pretty good guesses!

Don't believe turtle eggs overwinter....

You don't have any mob hits there do you?, lol

You need to bury the bodies deeper, HT.

Sandy turtle egg laying sites are scavenged year-round down here. Critters dig up the egg shell and any that didn't hatch.

and plant some endangered wildflowers over it.....

Earthworms, grubs, etc may be what the foxes are after.