Disease causing high mortality in Yellow-eyed Penguin chicks

In late November several cases of Avian Diptheria (Corynebacterium) were confirmed in yellow-eyed penguin chicks at locations on the Otago Peninsula and North Otago. The disease results in lesions in the mouth and throat causing respiratory problems and poisoning of young birds. Mortality rate of chicks is thought to be 60% or higher.

After further sampling, the epidemic was found to be more widespread than first thought. Aside from being present in every colony checked on the Otago Peninsula and North Otago, Yellow-eyed Penguin Trust Staff discovered infected chicks at Sandy Bay in the Catlins. No other species are known to be affected.

Back on the Peninsula the treatment of chicks with antibiotics is having mixed results with some chicks dying and others recovering. Massey University Scientists are working hard at identifying the specific bacteria and this may give us some clues as to the source of the disease and its mode of transmission.

We are continuing to monitor the situation in the field and treating chicks where practical. PhD student Thomas Mattern (assisted by David Blair, Projects Officer for the Yellow-eyed Trust) has started deploying GPS loggers on adults from affected nests at Boulder Beach and will do some diet sampling. This will give us a picture of where the birds are foraging and on what, which may prove useful if the source or trigger of the infection is marine based.

Adult penguins remain unaffected so tourists wishing to see penguins are still able to view them. However, tourism operators reliant on nests being viewed are affected as the adult birds may not remain at the nest sites when the chicks have died. The adults can still be viewed as they go out to sea in the morning and return to land in the evening.

Unexplained Chick Losses on Stewart Island

The Yellow-eyed Penguin Trust has just completed the first year of a planned five-year study to measure the effects of cat predation on yellow-eyed penguins on Stewart Island’s north-eastern beaches. But instead of cat predation, what we found was as yet unexplained high chick death rate.

Because of an apparent decrease in yellow-eyed penguin numbers on Stewart Island, the Trust, assisted by the Department of Conservation (DOC), was testing whether the loss might be attributed to predation by feral cats. During the 2003/2004 breeding season all nests along the Mt Anglem coastline were monitored intensely.

Early in the breeding season we discovered that chicks were dying at an alarming rate. Of 42 chicks hatched only 11 were still alive by mid-February. This is a survival rate of just 26%. At some beaches every chick died.

There were no signs that these deaths were due to cat predation, instead starvation appeared to be the most likely cause of death. This possibility was tested by comparing the weights of yellow-eyed penguin chicks from the offshore islands of Bench, Tommy and Whenua Hou (Codfish) to those in the study area / main island.

Although the weights of chicks on the offshore islands were on average lower than those on the Otago Peninsula, the weights of the surviving chicks in the research area were comparable.

Observers monitoring the penguin chicks noted large pieces of regurgitated fish beside some of the dead chicks. Could this be a repeat of the mystery disease or biotoxin that killed off a significant proportion of the breeding population on the Otago Peninsula in 1989-90 or a widespread shortage of food?

At the moment we have lots of unanswered questions, although we’re hoping there may be some partial answers when analyses of samples and autopsies are completed.

These results highlight the importance of regular, ongoing monitoring of our penguins. “If the Yellow-eyed Penguin Trust had not been on Stewart Island this summer, we would never know this event had happened. The Department looks forward to working with them to determine what is actually happening with these birds and if there is anything we can do about it” says Brent Beaven, DOC Programme Manager – Biodiversity, Stewart Island.

The Trust had already committed in principle to a five-year programme on Stewart Island, subject to finance being available. Although we feel it is important that our monitoring continues, we have not as yet been able to find total funding. This year’s work was largely funded by two, unexpected one-off grants. One was from the Community Trust of Southland, and the other from Contact Energy, as a result of Otago people using 10% less electricity to ensure adequate power supplies during early winter 2003. If you would like to consider helping fund this research, any donations marked Stewart Island Project will be earmarked for next season’s work.

Feral Cat Study on Stewart Island

Despite the fact that the first year of our study into the effects of feral cats on hoiho populations on Stewart Island did not show high rates of predation, we still managed to obtain some useful data.

Grant Harper’s research in an inland forested area on Stewart Island in 2002 found that the average weight for male cats was 3.4kg and for females was 2.6kg. Sandy King found almost identical results in the coastal yellow-eyed penguin habitat during our study this season: males 3.4kg and females 2.5kg.

However, the two studies differed in what food the cats appeared to be eating. Rats made up 60% of the diet of cats in the inland area, with birds making up 19% and invertebrates 15%. On the coast, rats and possums only accounted for about 30% of the diet, with beetles making up another 10%. Interestingly 27% of the stomachs were empty. Thankfully this season there is no evidence of yellow-eyed penguins in cats diet.

This year there was no cat predation seen of chicks. Our previous experience in Otago suggests that predation events may be sporadic and sometimes only occur every 2-3 years. The long-term monitoring that we have instigated will, over time, tell us to what level feral cats are affecting yellow-eyed penguin breeding success.