The Toughness modifiers on this table represent average specimens of particular species for comparison, but there are always exceptions. Not every great white has a +4 Toughness bonus. A young specimen might have a +3, while a larger fish might be +5 or even +6. The same is true for humans. Small humans suffer a -1 penalty, while those with the Brawny Edge gain a +1 bonus. Use the table as a baseline when creating your own creatures then adjust for particularly large or smaller versions.

Savage Worlds Deluxe Edition p. 154