Kiwi birds are flightless birds native to New Zealand. They are cherished as a national symbol and treasure in New Zealand. Unfortunately, kiwi birds face numerous predators that threaten their survival in the wild. In this article, we will explore the major predators of kiwi birds and the dangers they pose.
Stoats
One of the most significant predators of kiwi birds are stoats. Stoats are small carnivorous mammals that were introduced to New Zealand in the late 19th century. They have had a devastating effect on kiwi populations.
Stoats prey on kiwi chicks and eggs. Female kiwis will leave the nest for hours to find food, leaving the egg vulnerable. Stoats are agile hunters and can access kiwi nests in burrows. They will eat eggs and kill chicks. Stoats are responsible for over 50% of kiwi chick deaths in areas where they are present.
The impact of stoats has been amplified by habitat loss. As forests are cleared, kiwis nest in more exposed areas, making them easier targets. Stoats have caused local extinctions of kiwi populations in certain parts of the North and South islands.
Fortunately, intensive trapping and predator control programs have reduced stoat numbers in key kiwi conservation areas. But they remain a persistent threat. Continual control efforts are needed to protect kiwi nests from stoats.
Feral Cats
Feral cats are domestic cats that have been introduced to the wild. They also prey on kiwi chicks and eggs. Although they do not naturally occur in New Zealand, feral cat populations became established through early European settlement.
Feral cats are formidable nocturnal hunters. Their keen eyesight and swift movements make them effective kiwi predators. Cats will patiently wait outside burrows to ambush adults as they enter and exit. They also raid nests for eggs.
Feral cats are difficult to control over large areas. They have resilient populations due to high reproductive rates. Feral cats are most problematic in grassland habitats where kiwis nest in the open. Their predation pressure adds to kiwi losses from other introduced predators.
Possums
Possums are another major predator. They are Australian marsupials introduced to New Zealand for the fur trade. Possums eat large quantities of native vegetation. They will also take kiwi eggs and chicks if given the chance.
Possums locate kiwi nests using their strong sense of smell. They will raid nests and mangle eggs by chewing through the tough outer shell. Possums usually target vulnerable nests on the ground or in tree hollows.
In addition to direct predation, possums degrade kiwi habitat. Their browsing damages native forest understories where kiwis forage for food. Possum control is vital in areas where their populations are dense.
Dogs
Dogs that are allowed to roam freely, especially pig hunting dogs, will attack kiwi. Their keen sense of smell allows them to track down kiwis by their strong musky scent.
A single dog can wipe out a significant number of adult kiwis in its territory. There are many reported cases of dogs killing over 50 kiwis in a year. Dogs will rapidly pursue and seize adult kiwis. Their powerful jaws easily puncture and crush kiwis.
Dog predation is most common in rural areas near forests. Property owners must be educated to control dogs and prevent them accessing kiwi habitats. Otherwise, dogs pose a lethal threat to local kiwi populations.
Habitat Loss
Habitat loss is another critical threat facing kiwis. Since human settlement, over 90% of native forests in New Zealand have been cleared. This has greatly reduced kiwi habitat and populations.
Forest areas provide kiwis with suitable habitat features. This includes dense undergrowth for nesting sites, rotting logs containing insect prey, and plentiful ground cover. Habitat loss removes these necessities.
With less habitat, kiwi populations become fragmented into smaller groups. These isolated populations are at higher risk of dying out completely. Habitat restoration projects help link fragmented habitats to allow kiwi populations to mingle and boost their genetic viability.
Predator-proof Fencing
Predator-proof fencing provides a safe haven for kiwis by excluding introduced mammals. Extensive fenced reserves have been established in key kiwi areas including Rotorua, Coromandel and Northland.
These fences utilize mesh netting, electrified wires and curved hoods to prevent predators climbing over or burrowing underneath. Once enclosed, intensive trapping can remove any predators that remain inside the fence.
Monitored kiwi populations within these sanctuaries have thrived. Chick survival rates have significantly improved compared to unfenced areas. Predator fences demonstrate the positive potential if destructive introduced mammals can be controlled.
Predator Control
Ongoing predator control is critical to protect vulnerable kiwi populations outside of fenced sanctuaries. This is achieved through extensive networks of traps and toxin baits.
Trapping targets stoats, ferrets, feral cats, possums and rats. Baits containing biodegradable poison control possums, rats and stoats. These methods must be regularly maintained to keep predator numbers low.
It is also vital to control predators prior to the kiwi breeding season when eggs and chicks are most at risk. This gives juveniles a greater chance of surviving to adulthood.
Advantages of Flightlessness
Kiwis’ inability to fly, while a disadvantage against predators, also provides some surprising benefits.
Flight requires large amounts of energy. The kiwi’s flightless design is energy efficient with minimal fat and feathers. The energy saved can be used to power their acute sense of smell and strong legs.
Flightlessness allowed kiwis to occupy a unique ecological niche. They evolved as one of the only ground-dwelling birds to fill the role of small mammals.
By giving up flight, kiwis sacrificed speed and agility. But their evolutionary path provided them with distinct advantages in their native habitat prior to human-introduced predators.
Threats to Eggs and Chicks
Kiwi eggs and chicks face the most danger:
- Stoats, feral cats, and possums will raid nests and eat eggs
- Pig dogs have been known to wipe out over 50 adult kiwis in a year
- Chicks have no escape from introduced predators once hatched
- Only 10% of kiwi chicks survive to adulthood without predator control
- Habitat loss leaves nests more exposed to predators
Eggs and chicks are helpless against most introduced predators. Protecting nests is crucial to kiwi survival.
Threats to Adult Kiwis
Adult kiwis face fewer predators but still remain under threat:
- Stoats attack vulnerable adults around nest burrows
- Dogs are lethal to adults due to powerful biting jaws
- Feral cats ambush roosting adults at night
- Vehicle collisions are an increasing risk
- Habitat loss increases competition for limited resources
Adult kiwis have fewer predators due to their size, spurs and camouflage. But losses still accumulate over time.
Kiwi Predator Prevention Methods
Several proven methods protect kiwis from predators:
- Predator-proof fencing create safe reserves
- Trapping networks control stoats, rats, ferrets and possums
- Toxin baits target rats, stoats and possums
- Dog control prevents attacks on adults
- Habitat restoration provides dense cover for nests
These intensive efforts have increased kiwi chick survival where implemented. Ongoing work is needed to counter persistent predator populations.
Conclusion
Introduced predators are the major threat to kiwi survival. Stoats, ferrets, feral cats, possums, rats and dogs all endanger kiwi populations. Controlling these predators through integrated methods has proven effective.
But constant vigilance is needed. Kiwis rely on successful conservation work to thrive. Their long term future in New Zealand depends on effectively managing introduced predators.
