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The red howler monkey is on an island in the south that you can't get to until you reach a certain part in the story, closer to the end. The white panther is on your hideout island. I'm assuming those are the rate animals your looking for
I also found the white panther on one of the assassins missions for the templer keys it appeared near the end of a hunting mission. If you are having trouble finding the animals for upgrades you can buy them but they are costly.