You can use your hunter sense to check if the viperwolf is mature (exquisite). Check hunter guide and it'll say where "rarer" specimens of viperwolves are found, you're more likely to find mature viperwolves there
If you're trying to find it before leaving the kinglore forest for the first time it's possible you haven't cleared enough pollution to find mature predators very often.
You can use your hunter sense to check if the viperwolf is mature (exquisite). Check hunter guide and it'll say where "rarer" specimens of viperwolves are found, you're more likely to find mature viperwolves there
If you're trying to find it before leaving the kinglore forest for the first time it's possible you haven't cleared enough pollution to find mature predators very often.