Threats

Yellow-eyed penguins / hoiho are very vulnerable to bycatch in set nets (gill nets), and have also been recorded as trawl bycatch, although to a lesser extent. The Ministry for Primary Industries (MPI) estimate that 44 hoiho die each year around the mainland in fishing nets, the majority of these deaths are in set nets. Even a small increase in adult mortality can have serious effects on the long-term survival of hoiho.

Indirectly fisheries may impact hoiho by influencing the distribution and availability of fish on which the penguins feed, or damage the seabed and animals that live on or in it.

Starvation and nutritional stress are now becoming more common for hoiho. Variation in the quality and quantity of prey can result in reduced fledging weights, breeding success and growth rates, chick mortality, and an overall decline in local hoiho populations.

The Conservation Services Programme (CSP) is administered by DOC and Fisheries New Zealand (FNZ), funded by a levy on the fishing industry and has the following objectives:

• To understand the nature and extent of adverse effects from commercial fishing activities on protected species [e.g. hoiho] in NZ waters.
• To develop effective solutions to mitigate adverse effects of commercial fishing on protected species in NZ waters.

This forum has been used to lobby for increased observer coverage on fishing boats, especially those engaged in inshore set netting, to determine the true picture of penguin mortality. The Trust is engaging with MPI and the fishing industry to attempt to resolve this significant conservation threat.

Yellow-eyed penguins / hoiho live in the sea and on land and therefore come into contact with a range of pollutants which cross both habitats. Typically, penguins are most vulnerable to pollution in the ocean as this is where they feed and likely to ingest or come into direct contact with pollutants.

Toxins or pollutants released on land make their way to the coast via storm drains, sewage outfall pipes or as run off from land into our rivers. Pollution is likely to be an issue for penguins living close to larger settlements (e.g. Dunedin).

Oil spills can have devastating localised effects particularly for small penguin populations. Oil affects penguins in two ways either through ingestion which may lower hormones and suppress breeding or poison them; or through the oiling of feathers. Oil reduces the waterproofing and insulation of the feathers, making the birds lose buoyancy and either drown or leaving them vulnerable to cold.

Algal blooms (a fast growing dense population of algae) can result from an increase in nutrients (e.g. from outfalls, storm water), and a combination of favourable environmental conditions. Less than 2% of these blooms can release toxins. Toxic algal blooms were a suspect in the unexplained mass mortality events of adult hoiho in 1989-90 and 2012-13, although there was no direct evidence.

Ingestion and entanglement in marine debris, is a major issue for many seabirds, although it has not yet been observed in hoiho. Plastic is a growing problem as it does not biodegrade quickly and forms more than 70% of the litter on New Zealand’s beaches. Plastic also contains toxins which can accumulate in the food web.

Predation by invasive mammals is a major cause of species extinctions globally. Invasive mammals are a particular problem for island nations like New Zealand where animals have evolved in the absence of such predators.

Land-based predators which may kill penguin chicks or eat their eggs include mammals such as rats, stoats and ferrets. Predation by cats is suspected, but there is no direct evidence. Dogs are capable of killing adult birds as well as chicks. Pigs are also an issue rooting up nest sites, eating eggs and even killing adult birds. Annual chick mortality can be as high as 60% in the absence of effective land-based predator control.

Predation of hoiho in the sea is exclusively by native animals such as New Zealand sea lion and sharks. Barracouta are thought to cause accidental injury when they cross paths with hoiho or feed in the same area. All of these species have evolved together however and so predation events at sea are natural.

Penguins are susceptible to a range of infectious and parasitic diseases. Birds can be more susceptible to disease if they are stressed (environmentally or nutritionally) and their immune system is suppressed.

Avian diphtheria is a disease which commonly affects young chicks. Bacterial plaques form in the mouth and can be inhaled, causing aspiration pneumonia, or result in a blockage which prevents feeding and causes dehydration. Chicks which survive have reduced growth rates and often fledge in poor condition.

Avian malaria is caused by blood parasites (Plasmodium sp.) which are transmitted by mosquitoes. In the season 2018/19 there were 29 confirmed hoiho deaths from avian malaria which affected adults as well as chicks. Each year we see deaths from malaria. It is likely that significant rain events and increased temperatures led to favourable breeding opportunities for mosquitoes, thus increasing their numbers.

Disease has the potential to become a bigger issue in the future as the climate warms, and as human disturbance and stress on the penguin population increases.

The degree to which human disturbance is an issue that tends to be site specific, some penguin breeding sites have no public access and others have a constant stream of visitors.

There are various types of disturbance, from extreme direct impacts (e.g. a dirt bike squashing a penguin nest) to the more common indirect impacts (e.g. noise and visual disturbance from people at breeding sites). Seemingly harmless acts such as standing on the beach, can actually prevent a penguin from accessing the nest and feeding its chicks.

A number of studies examining the impacts of tourism (particularly unregulated tourism) on hoiho show that disturbance increases stress, and reduces breeding success, fledgling weight and the probability of survival.

The influence of human habitation in New Zealand has resulted in changes in land-use, the damming of rivers, the threat of fire and historically the harvesting of penguins.

Historical changes in land-use through large-scale clearance and fragmentation of coastal forest to make way for farming has transformed native vegetation to pasture. But whilst the changing landscape has influenced their nesting habits, hoiho are able to breed successfully in modified environments.

The introduction of large grazing stock like cattle and deer can create problems in hoiho habitat by trampling nests and birds (particularly chicks). Smaller grazing animals such as sheep pose less of a risk through trampling, but do browse and destroy vegetation.

Fire could be devastating for a local penguin population. A catastrophic scrub fire was responsible for the deaths of more than 60 adult hoiho at the Te Rere Reserve in the Catlins in 1995.

Most species are well-adapted to short-term variation in climate or weather, but not to long-term shifts in climate and increased frequency or intensity of extreme events.

Short-term extremes in weather, like intense storms and high temperatures can affect birds directly. Fat and heavily feathered, the hoiho is perfectly insulated for foraging in the depths of the cold ocean. But ashore, in this warm temperate climate, the insulation becomes a liability. The birds cannot remove their ‘wetsuits’, but need shady undergrowth to avoid overheating. Shade also prevents their eggs from getting too hot. Storms can stir up the ocean reducing visibility for hoiho which swim to the seabed to capture fish.

Global warming may also impact oceanic processes and alter the food webs on which hoiho depend. Fluctuation in the numbers of breeding pairs of hoiho from year to year are at least in part linked to climate change, in particular changes in sea surface temperature (SST) and rainfall. Adult survival was low in periods with warmer than normal SST and conversely was high with cooler than normal SST.