Mice no longer eat parrot eggs

Short claws.
photo: document

A rare and mysterious native fish that lays its eggs on land is getting help to fight off rats that are pillaging its nests.

Last year, Department of Conservation ranger Fern Donovan was surprised to discover three nests of the endangered short-chinned parrot in Northland’s Waipoua Forest.

This is the first time a Short-jawed Kokop spawning site has been discovered in Northland – in fact, it is the first time a Short-jawed Kokop spawning site has been discovered anywhere, apart from a spawning site discovered in Taranaki in 2001.

The short-jawed kōkopu’s nest consists of more than 50 tiny, translucent eggs, which are laid on leaf litter or gravel at the edge of a stream.

The short-jawed kokopu is a rather unusual fish among fishes because its eggs develop on land, such as here in the Waipoua Forest.
photo: DOC/Verne Donovan

However, Donovan’s surprise quickly turned to despair.

“I set up trail cameras to monitor the nest and went there every day. I was sad to see that the number of eggs in the nest was decreasing day by day,” she said.

“When I checked the trail camera, it showed a rat had visited multiple times and eaten all the roe.”

Within ten days, the remaining eggs had rotted and were no longer viable, even for mice to eat.

That was enough to prompt the Department of Conservation and local iwi Tiroroa to take action.

Together, they developed an intensive predator control program to tackle this year’s shortjaw spawning season (peak spawning is May-June).

Te Iwi o Te Roroa scientific adviser Taoho Patuawa said Donovan’s findings demonstrated the impact rats had on taonga at a critical stage in the species’ life cycle.

He said rodent tracking tunnels used to measure the presence of rats and mice show that predator control strategies are working.

In the predator control areas, only 3% of the tracking tunnels were visited by rats, while 96% of the untreated areas were visited by rats.

A mouse nibbles eggs from a short-jawed kōkopu nest in Waipoua Forest last year, captured by a trail camera.
photo: DOC/Verne Donovan

Donovan said she has found two more nests this year.

As of last week, little eyes had appeared in some of the eggs, and if she looked closely, she could see the larvae twitching.

This gave her hope that the eggs could survive.

She said that last year when they reached that stage, all the eggs had been eaten.

She was unable to return to the nest this week due to heavy rain over the weekend, but she is optimistic the eggs have hatched.

Short-jawed Cooters lay their eggs on the edges of streams during late fall to early winter, when water levels are high after heavy rains.

The eggs develop on land and do not hatch until the next flood hits two weeks to two months later.

The larvae are then washed into estuaries and the sea, eventually swimming upstream as whitebait.

Donovan said she made the discovery after monitoring adult fish in Waipoua Forest for several months in 2023.

“When I was sure they were spawning and laying eggs, I searched around along the edge of the stream, crawling on my hands and knees. So when I finally found some spawning sites after weeks of searching, I was ecstatic and very excited.”

Donovan said the short-jawed Cope is worth protecting.

“They are endemic to New Zealand, which means they are found nowhere else in the world. They are an important part of our freshwater ecosystems and a good indicator of the health of our streams. They are an important part of biodiversity and represent the uniqueness of our flora and fauna,” she said.

EPA ranger Fern Donovan at the Waipoua River.
photo: DOC/Sarah Wilcox

Mr Patuawa said he looked forward to seeing the results of the joint efforts of the Department of Conservation, Te Roroa and other organisations to restore the Waipoua River.

“It’s great to have such a concentrated effort in our forests. Our findings will be valuable for the conservation of this taonga species here and in other parts of New Zealand, and ensuring the short-jawed kōkopu can thrive,” he said.

The project is part of the Department of Conservation’s ‘Ngā Ika e Heke’ freshwater migratory fish project, which aims to protect New Zealand’s short-jawed kokopu, inanga, longfin eel/tuna and lamprey populations.

The short jawfish is the rarest of the six native fish species that are used as whitebait. Their threat status is Threatened – Nationally Vulnerable.

Waipoua Forest is also home to New Zealand’s largest living kauri trees, including the famous Tāne Mahuta.