Feral cats hunting high in South Island mountains, some even crossing passes to West Coast headwaters

Feral cats have been tracked roaming high into South Island hills and sometimes over the Main Divide.

Manaaki Whenua – Landcare Research field ecologist Ivor Yockney recently gave an update on the progress so far of a project to track the movements of 20 feral cats captured and fitted with GPS radio collars in the upper Hope River (Lewis Pass) and Hawdon River (Arthur’s pass).

The research was started after confirmation that feral cats were killing adult kea at high altitude. Ten cats were trapped in each of the river valleys studied, and the cats were fitted with tracking collars before being released.

Little was known about feral cat habitat use, distribution, density, movement ecology, or impacts on native animal and plant life in these eastern beech forests, Landcare said.

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Not to be confused with your friendly neighborhood kitty, feral cats live and breed in the wild, hunting for survival and killing native birds in the process.

Anecdotal reports of increased feral cat abundance and distribution in those areas would point towards greater threats to native animals from predation.

Yockney said it had been surprising to find feral cats hunting at such high altitudes.

While kea predation was the motivation for the study, the research was about feral cats in the mountain landscape.

Kea were just a sentinel species of presumably a large range of fauna falling victim to feral cats, Yockney said, adding that an adult kea was probably quite formidable prey for a feral cat.

Cats were defined as feral when they are born and bred in the areas where they are found, and had no physical association with humans.

Landcare data shows the location of fixes of cats tracked in the Hawdon Valley.  Movements in hills in the center left are the 'alpine specialist', while the fixes at the bottom of the picture are of another cat that crossed through Walker Pass to the West Coast.  Fixes in the upper right are from a cat that traveled from the Hawdon to Cass, presumably crossing a bridge over the Waimakariri River.

Manaaki Whenua – Landcare Research/YouTube

Landcare data shows the location of fixes of cats tracked in the Hawdon Valley. Movements in hills in the center left are the ‘alpine specialist’, while the fixes at the bottom of the picture are of another cat that crossed through Walker Pass to the West Coast. Fixes in the upper right are from a cat that traveled from the Hawdon to Cass, presumably crossing a bridge over the Waimakariri River.

It was possible generations of cats had been living in the areas, and at the time the research stared no work had been under way to control the cats in the areas studied, Yockney said.

A “huge” amount of data had been gathered, but analysis had yet to start.

The sole non-tabby cat tracked was a black male in the Hope Valley, from which 336 days of data had been collected.

His home range was 23km long, and he spent much of his time on an area of ​​river flats, but he had also been over the Main Divide to the headwaters of the Tutaekuri River on the West Coast, Yockney said.

Landcare data showing the movement of 10 feral cats in the upper Hope Valley.  The small number of fixes from forested areas at higher elevation raises the possibility fixes are being missed in those areas.

Manaaki Whenua – Landcare Research/YouTube

Landcare data showing the movement of 10 feral cats in the upper Hope Valley. The small number of fixes from forested areas at higher elevation raises the possibility fixes are being missed in those areas.

There was 245 days of data on another male cat, referred to as the “alpine specialist”. A collar was put on him on the Hawdon Valley floor in September 2021.

That cat had spent much of his time in the alpine environment, but was also tracked down in the main valley.

“He’s covering a fair amount of terrain, making large altitudinal changes, and he’s seemingly in some sort of a circuit, and always returning back to the main valley floor between forays,” Yockney said. One time he was found in an adjacent catchment 9km away.

That cat was trapped and killed in the Hawdon Valley in mid-May as part of a feral cat control operation that was now under way.

That helped with a question researchers were hoping to answer, which was whether trapping cats on the valley floor would catch animals that spent time at higher altitudes, Yockney said.

Kea on Avalanche Peak, in Arthur's Pass.  Even at high altitudes, kea have been prey to feral cats.  (file pic)

ALDEN WILLIAMS/FAIRFAX NZ

Kea on Avalanche Peak, in Arthur’s Pass. Even at high altitudes, kea have been prey to feral cats. (file pic)

A slide of the movements of all the cats being studied in the Hawdon Valley showed that mostly they spent their time lower down in the valley.

“There’s a strong preference for edginess, however a couple of the cats definitely hunt the alpine,” Yockney said.

Along with the alpine specialist there was another cat from the Hawdon Valley that crossed the Main Divide. It had gone through the Walker Pass into the headwaters of the Otehake River on the West Coast.

Another of the cats was also going between Cass and the Hawdon Valley, presumably crossing the Waimakariri River by using the Mt White Bridge.

A feral cat photographed on Onoke Spit, at the bottom of the North Island in Wairarapa.

SUPPLIED

A feral cat photographed on Onoke Spit, at the bottom of the North Island in Wairarapa.

Issues with the study included the possibility that the sample of cats may have been biased because the animals were trapped on the valley floors, but the study was an initial pilot trial, and live-trapping cats higher up was logistically challenging.

Yockney said predation of kea during normal years was “fairly low”, but it was a different story following a beech masting event – ​​years when beech trees produce seeds.

Rodent numbers boomed during mast events, followed by stoats and presumably feral cats. Then rodent numbers fell catastrophically when there was no more seed.

“And then there are a load of predators out there, and their main source of diet has gone, and then they prey switch.”

A meta-analysis of other feral cat studies, by researchers from the University of Auckland, AUT and Landcare, shows the size of feral cats’ home ranges varies substantially.

A member of a colony of ginger cats that have been hunting white-fronted terns at a reserve in the Waitākere Ranges of west Auckland.

LINDY HARVEY/Supplied

A member of a colony of ginger cats that have been hunting white-fronted terns at a reserve in the Waitākere Ranges of west Auckland.

The researchers looked at 39 studies, including 11 from New Zealand and 15 from Australia. Male cats in the studies had home ranges varying in size from 22.1ha to 3232ha, while the home range of female cats ranged from 9.6ha to 2078ha.

Home range was considered the area within which an animal moved while carrying out normal activities such as mating, caring for young, foraging or hunting.

A previous study had found larger cats had larger home ranges, and cats living in more productive habitat had smaller home rangers, the paper, published in the New Zealand Journal of Ecology, said.

The results of the meta-analysis suggested it may be difficult to make further generalizations about what influenced feral cats’ home range size.

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