、。
If the prey were to die out, the hunters would disappear too.
Literal
By-chance prey [subject-が] die-out-[conditional-ば], hunters come-to-not-be [probably-だろう].
死に絶える ('to die out, go extinct') is a dramatic compound verb: 死ぬ ('die') + 絶える ('cease, come to an end'). Used specifically for extinction of a species or lineage. いなくなる ('come to not exist') is the inchoative 'disappear' pattern for animate beings. Note the missing particle: 狩人いなくなる drops the が, a slight compression that reads as casual or terse.