This is Sean Whalen (prion).
I don't remember if this issue was brought to a consensus, but I know that there was some discussion about what the Sleighers (in Tracking Song) were doing when they told the Panigaku to not eat certain rare animals much.
Since the Sleighers are terraforming the planet, they, as per their implied desire not to change what occurs very much, don't want any animals to become extinct because of their actions. They tell the tribes to not eat food they see rarely, because after the warming some species of "food" will have difficulty coping with the changes (like those who live in snow) and decrease in numbers. If the tribes ate them when they found them (as a treat, if they become rare) they would probably go extinct.
prion