The deaths are part of a spate of incidents involving dogs and wildlife on Otago beaches since the beginning of the year.
Doc ranger Richard Seed said this was a devastating reminder for all dog owners to keep their pets under control on the beach.
"Hoiho [yellow-eyed penguins] are one of the world’s rarest penguin species and we are lucky to share our coastline with them.
"Their population is rapidly declining due to a range of threats on land and at sea," he said
"Disturbance and deaths from dogs is such a needless threat but one that our community can help to stop. That means keeping your dogs under effective control at all times, and giving wildlife plenty of space."
The deaths occurred in two separate cases. The most recent took place at Purakaunui Bay in the Catlins where a small dog was roaming off lead and mauled a male hoiho, killing it within seconds.
Earlier this year, a hoiho was observed being harassed by a dog on St Kilda Beach. The penguin later died from its injuries.
Other incidents involving dogs include an off-lead dog grabbing and shaking a sea lion pup on Tomahawk Beach. In this instance, the owner of the dog did the right thing by reporting the incident. The sea lion received no permanent injuries.
Earlier in February, a red-billed gull was mauled by a dog on Brighton Beach. It was taken to Dunedin Wildlife Hospital but died from its injuries.
Mr Seed said people needed to accept that any dog was capable of injuring wildlife.
"We know everyone is horrified when things like this happen and it’s not intentional.
"We always hear people saying that their dog would never harm wildlife but people need to understand that any dog, no matter the breed or how well-mannered they are, is capable of injuring or killing wildlife."
He said hoiho were endangered and taonga to Ngāi Tahu.
"They’re incredibly vulnerable, especially from February to April when they come ashore to moult.
"They — and all other wildlife — deserve to be able to come ashore and rest."
Dog rules around wildlife
Take dogs only to areas that allow them, and keep them under control.
Keep your dog close and away from the dunes.
If you come across wildlife put your dog on a lead and lead it away.
Warn other dog owners at the location.
Notify Doc if you see wildlife being harassed by people or dogs.
