Successful build - Chance fights ever on the side of the prudent.

Link to build: https://jenkins.wildfiregames.com/job/differential/1762/display/redirect

The idea of fogging and miraging is that players need to scout, so it would be consistent to hide animals in the fog of war, including the resources.
It is especially important that players can't track changes through the FoW, i.e. seeing the resource count of a resource being reduced.
I recall it was discussed on multiple occasion in the past, I wouldn't be surprised if it was discussed throughout the decades on forums, irc and trac, perhaps it's even in the design documents.
#3201 was one of my tickets I recall, I didn't search further...

As the description was ambiguous and the code not obvious to the uninitiated, this patch makes animal resources visible in the FoW, including resource changes.
So I would recommend red or purple status.

@elexis Indeed this is making resource animals coherent with animals proper, which are visible in FOW.

Either they are always visible or never visible, but having them in this half-half state appears incorrect.

Problem correctly observed, proposed solution going the opposite way and making it more inconsistent, it just seems conventient to remove the complexity to deal with FoW in unitAI gathering?

In D1997#84616, @elexis wrote:

Problem correctly observed, proposed solution going the opposite way and making it more inconsistent, it just seems conventient to remove the complexity to deal with FoW in unitAI gathering?

Well it does remove complexity in UnitAI.
Consistency is debatable - I don't see so far a place where we've said that ultimately we wanted animals to be invisible in FOW. It's also consistent with, for example, AOE2.
I don't mind animals being invisible in FOW but that's quite a gameplay change.

As for consistency, if animals are visible in the fog-of-war when alive, then they ought to be visible when dead as well.
That said, I don't have any idea what UnitAI.js or resource.xml actually do.

Personally I think fauna shouldn't be visible in fog-of-war, neither dead nor alive. Animals are units, observing them flee or get killed shows activity of other players, something which goes contrary to the fog-of-war principle. Nor should it matter what Age of Empires or other games do.
Moreover, tigers and wolves are a lot more annoying when you don't know their position beforehand.
Therefore I think the proper thing to do would be to remove the following lines from template_unit_fauna.xml:

<Visibility>
  <RetainInFog>true</RetainInFog>
</Visibility>

But yeah, that would indeed be a gameplay change and outside the scope of this patch.