Complex sentence: Rats and stoats are known to kill Hochstetter ´ s frogs and predators known to predate other frog species in New Zealand (pigs, cats, hedgehogs, ferrets) are also likely to have an impact.
Split into simpler sentences: Rats and stoats are known to kill Hochstetter ´ s frogs. Predators known to predate other frog species in New Zealand, such as pigs, cats, hedgehogs and ferrets, are also likely to have an impact.