Transcription
Almost any bird or other unique animal that has made its home in New Zealand has been shaped and molded in some way by the sheer remoteness of the islands. New Zealand is separated by its closest continent, Australia, by around 1,000 mi of ocean, being roughly equal in distance as France is to Iceland or Maine is to Florida. However, the Pacific Ocean isn't short of remoteness with thousands of tiny volcanic islands appearing as small dots separated by vast waves of blue. Many of which are strictly more remote than New Zealand.
But most of these islands are very young. The vast majority of islands in the Pacific are volcanic and so have usually formed fairly recently and their ecosystems haven't had long to take hold. New Zealand is very seismically active and has been shaped, elevated, and added to by its volcanoes. However, much of the land is of ancient origin, and New Zealand actually separated from the other continents over 80 million years ago. So, it had already gone its own way when the dinosaurs were being driven to extinction. And so, has had many millions of years for its animals and plants to evolve on their own after this and for its ecosystems to mature.
One of the largest consequences of New Zealand's unique history is that it is practically empty of mammals, but absolutely abundant with birds. There are two types of seal and two species of native bat that predate the arrival of humans, but that's it. Depending on definitions, New Zealand doesn't have any native land mammals. On the other hand, there are over a 100 species of reptile. And as a direct result of evolving in an ecosystem completely lacking in native mammals, birds often fill large animal niches occupied by mammals in almost all other parts of the globe. For example, across the world, mammals, especially small mammals, dominate nocturnal niches with around 70% of mamalian species being nocturnal. But in New Zealand, the nocturnal scavenger roles are mostly filled by birds. There are nocturnal parrots and five distinct species of kiwi that use their keen sense of smell to forage for worms, insects, and fruit on the forest floor after the sun goes down, occupying a similar niche to a badger or a hedgehog. Kiwis have even convergently evolved whiskers, but they are not made of hairs. Their whiskers are highly modified feathers that perform the same function.
One of the largest native land animals still living in New Zealand is a flightless bird named the takah. These birds are related to omnivorous mohens, but in addition to becoming flightless on New Zealand, they have evolved to primarily graze on grass. As a result of their diet, they have adapted an enlarged digestive system that helps break down and process large quantities of poor quality plant material. Although the way it is done is different, this is functionally similar to herbivorous ruminating animals, albeit not as efficient. So, in the absence of animals like deers and goats, the takah has adapted into a medium-sized grazer. Up until fairly recently, all of New Zealand's herbivorous niches were actually dominated by birds. New Zealand's largest animal being one of the largest birds that has ever existed, the mower. Mowers were actually very diverse, ranging from the size of a turkey to Dionis, where the females could stretch out to almost twice the height of an adult man. They were the tallest birds known to have lived and the second largest. Interestingly, they are also the only lineage of birds known to have completely lost their wings due to being flightless for so long.
New Zealand's flightless bird species have descended from at least nine different flying lineages that made the trip to New Zealand separately before evolving to become flightless. Although flightlessness seems like a downgrade, there are benefits to it. Birds have made a significant amount of sacrifices in other areas during the evolution of flight, and it requires an incredibly high amount of energy. So, there is a very strong selector pressure to lose the ability. If birds find themselves in an environment where it isn't strictly necessary to fly, they will likely evolve to lose it or at least become poorer flyers. For instance, without tree dwelling mammals, a bird named the cocako uses very similar movement to traverse between tree branches to opportunistically feed on fruits, nuts, and seeds. These birds are actually able to fly. They just fly poorly and instead prefer to climb between the branches most of the time instead, which is reminiscent of animals like squirrels and monkeys. Birds actually use less energy gaining altitude by climbing than they do by flying. So with less predators around, these birds have just evolved to hop through the trees instead.
Since there were no large mamalian predators, the largest predator on New Zealand until fairly recently was just an enormous bird of prey. New Zealand was once home to the heaviest eagle known to have lived named the Hass eagle that weighed roughly twice as much as the heaviest eagle living today, the Stella sea eagle. And amazingly, there is significant evidence they hunted giant mower despite being a fraction of their size. It wasn't just birds, though, and the absence of small mammals like rodents also affected insect evolution on New Zealand as well. The giant wetter is one of the heaviest insects in the world, weighing around 70 g, becoming opportunistic omnivores, living like small rodents.
New Zealand had already separated from the other continents before the KPG extinction that caused the extinction of the non-avian dinosaurs. And it was thought that this is what created this mammal and predator-free environment with abundant vacant ecological niches. However, more recent findings have shown this isn't the case. While in isolation from Australia and Antarctica, New Zealand does have a small fossil record of animals including dinosaurs. Their bones are fragmentaryary. But an ankyosaur has been discovered, a sorapod, and even an unidentified carnivorous dinosaur. And there is some evidence that these dinosaurs had evolved unique features evolving on an isolated island. New Zealand was significantly closer to the South Pole at this time. But as global temperatures were much higher, it wasn't cold. And these dinosaurs roamed a temperate coastal rainforest. The dinosaurs and many other animals that remained in New Zealand after its separation were driven to extinction by the asteroid impact, leaving the islands mostly uninhabited.
It was thought that due to the isolation, these vacant niches were quickly filled by birds instead of mammals like almost everywhere else in the world at this time. But it didn't actually play out like this. There is a history of birds on or around New Zealand dating all the way back to just after the mass extinction like Wymanu which was one of the earliest penguins ever discovered and a pelagonid which were enormous seabirds that used to be common but are now extinct. There are even some flightless birds like the kiwi that most likely had an incredibly ancient history on the islands descending from flying ancestors that arrived in New Zealand not long after the dinosaurs had gone extinct. However, genetic studies show that the majority of birds on New Zealand, including many of the famous flightless ones, actually arrived much later, around 25 million years ago.
But even more surprising, New Zealand did have mammals once upon a time. In the center of New Zealand's South Island, the jawbone, feur, and skull fragments of a mammal have been discovered that would have been a fully terrestrial animal. The discovery took place in the 19 million-year-old rocks of the St. Bathens formation long after the KPG extinction and other fossils in the area show the animal would have lived alongside many species of bird. The creature is not officially named going by the St. Bans mammal and was not closely related to any modern kind of mammal. Study of its very fragmentaryary remains has shown that it likely came from a lineage of mammal that sits somewhere in between the theans which includes marsupials and placental mammals and the monotreams the egg laying mammals although it was not closely related to either. This shows that a group of mammals survived on New Zealand when birds had started rapidly adapting, but also an extremely ancient mammal lineage survived on New Zealand up until much more recently.
New Zealand's native land mammals may have gone extinct, but there are now dozens of invasive mammals in New Zealand introduced by European settlers that are one of the biggest threats to the local wildlife that specifically evolved in an environment without them. When learning about the decline of various species and the destruction of the environment, it can seem pretty hopeless and extinction can feel inevitable, especially since it's now caused by humans. But it doesn't have to be if we start acting now, which is exactly why I joined Planet Wild. Planet Wild is a community-based organization with a goal to protect the natural world around us. Every month, the Planet Wild community with over 20,000 members, including myself, funds a different environmental mission that rewests, help threatened animals, or clean the world's oceans. These missions are documented in videos on YouTube so we can actually see the impact that we are making. Like in the past, we helped bring endangered seahorses back from the brink, restored Scotland's ancient woodlands, or even saved whales with drones. The topic of extinction is everpresent on this channel, and it is a natural process, but we are currently living through a biodiversity crisis with species going extinct 100 to a thousand times faster than what is normal. I like being a part of a community that is trying to change this. If you want to join a growing community that is making a difference in the natural world, then consider joining Planet Wild. Big or small, any contribution amount will make a difference. The first 100 people to sign up using my code, Motholike 2, will get their first month paid for by me. Just scan this QR code or click the link in the description. The moment you sign up, you'll immediately be making a difference and can see the results here on YouTube 30 days later. If you want to see Planet Wild at work, you can watch their mission saving seahorses with the link in the description.
The discovery of mammals and a much later arrival date for many of the birds shows that New Zealand actually had quite a complex geological history. New Zealand is comprised of two islands that together form a land mass that is slightly larger than the UK. However, it is actually only a small part of a significantly larger hidden continent that is submerged beneath the waves. The continent is named Zealandia and it is about 2/3 of the size of Australia. During the Jurassic period over 150 million years ago, all of the southern continents were lumped into one big superc continent named Gonduana. And Zealandia is just a big chunk of this ancient continent that has sunk to the bottom of the ocean. When New Zealand broke away from Australia and Antarctica, this large chunk of rock underwent significant continental thinning, which is when the tectonic plate is stretched horizontally, reducing its thickness. This continental thinning continued until the continent was almost completely submerged 1 to 2,000 m below the ocean's surface. This is significantly higher than the ocean floor, which is very deep in the Pacific, meaning there is a distinct continental shelf. At this time around 30 million years ago in the Igosene, the transgression from the sea left a scattering of low-lying islands. These would have acted like nature reserves preserving some of the long-lasting land animals that trace their lineage all the way back to Gonduana and some earlier arriving birds like the kiwi. This can be seen in New Zealand's geology as there are extensive limestone deposits dated to around 30 million years ago all over the islands. Limestone is formed from an accumulation of the shells and skeletons of marine animals. So these parts of the islands must have been submerged.
Around 20 to 25 million years ago, the Pacific and Australian tectonic plates shifted, creating intense seismic activity that pushed the ocean floor rocks up above the surface of the ocean. It also created intense volcanic activity that would have added to the land as well, sculpting a much larger land mass that was approaching the size of modern-day New Zealand. Because New Zealand was mostly submerged for a long period after its separation, it was likely harder for birds to gain a foothold on its ecosystem. However, after the land mass increased in size significantly around 25 million years ago, there would have been a land with very few predators, high amounts of food, low competition, and also just a larger target for animals like birds to find.
Mammals weren't the only animals that managed to cling on in New Zealand the whole time. And there are actually many small land animals hidden on New Zealand that trace their ancestry all the way back to Gondwana. Crawling in the damp undergrowth of New Zealand's rainforests are nocturnal predators named velvet worms. Velvet worms are ancient Gondwan creatures with a fossil record dated to over 300 million years ago and have been present in New Zealand since its breakup. New Zealand is also home to an ancient type of conifer tree named the arocaria. These trees were very common throughout the world during the Jurassic period but then declined heavily by the extinction of the dinosaurs. They were restricted to the southern hemisphere and so today you only see them in various pockets of Australia, South America and New Zealand. Also, New Zealand's largest reptile, the Touitara, is an ancient resident. Turitaras look like lizards but their anatomy shows they are actually very different animals. Touittaraas are members of a group of ancient animals known as the rinkalians that genetic studies show had a common ancestor with snakes and lizards around 250 million years ago in the early triacic period. The rinkalians were the dominant small reptile around the world for many millions of years but started to decline in the Cretaceous period at the same time lizards started to become more common. Today, the touittara is the last living ringalen. Since they separated from lizards a very long time ago, they have many unique features not shared by any other reptiles. Touittaraas don't have tooth sockets and their teeth are actually completely fused to the jawbone. On their top jaw, they have two rows of teeth that complete an interlocking mechanism with their bottom row of teeth when their jaws are shut. Finally, the front of their top jaw is fused, forming a beak-like structure, and these are advanced features they evolved after separating from lizards. On the other hand, they have some primitive features lost by many other living reptiles. For instance, their vertebrae is unlike any other living reptiles and much more reminiscent of fish and amphibians.
Alongside Turotara, New Zealand's native land-based reptile population is exclusively made up of geckos and skinks. And no other reptiles occur here naturally like other types of lizards or snakes. Genetic studies show that both geckos and skinks weren't present in New Zealand during its breakaway like Turitaras and actually are later arrivals. There are fossils of both skinks and geckos in the St. Bath Formation, so they must have been here at least 19 million years, but it isn't known when they arrived. They likely reach New Zealand due to being accidentally rafted over the ocean on floating vegetation. Birds are very good at establishing colonies or breeding populations in far off isolated places due to being able to fly. But what is perhaps more surprising is that reptiles are also quite good at finding a foothold on islands in far off lands. Unlike mammals, reptiles are very resistant to dehydration and as they have much slower metabolisms, require considerably less food and can go long periods without eating. Unlike amphibians, they are also much more tolerant to salt water. These features mean that reptiles have managed to disperse across vast oceans by accidentally being carried out to sea by fallen branches and vegetation that have rafted to far off islands. You can see this pattern on other islands like Fiji that other than bats have no native land mammals, but has four native species of iguana. Iguanas are native to the Americas and this is the only other place in the world they can be found naturally as they were rafted out to sea and landed here. Also, the Galapicus like New Zealand has a reptile and bird dominated ecosystem only having one native mammal, the Galapicus rice rat and all its other animals are various types of birds and reptiles that have migrated there.
As geckos and skinks are the only reptiles that manage to migrate to New Zealand, they have adapted to occupy niches filled by other types of lizards in the rest of the world. Geckos are very diverse in New Zealand, which is a global exception because by and large geckos are tropical animals, being most diverse in countries near the equator with hot and humid climates. Apart from being a little bit warmer, the climate in New Zealand is very similar to the UK, especially the South Island. But the UK has no native gecko species. The whole continent of Europe has around 12, but New Zealand has 48. In the absence of the other types of reptiles, many species of gecko in New Zealand have adapted to become hardier and survive in colder, harsher environments. For example, the orange spotted gecko found in the mountains of New Zealand's South Island survive in colder and harsher environments and can remain active in sub-zero temperatures. All known geckos native to New Zealand also give birth to live young rather than lay eggs, which is very unusual for geckos and is thought to also be an adaptation to the cold. Other species of cold weather reptiles like the viviver pararis lizard that lives across the northern hemisphere has also evolved to give birth to live young as the eggs are retained inside the body to keep them warm. The vast majority of skinks on New Zealand have also evolved to give birth to live young as well which is unusual compared to species found elsewhere. The way New Zealand's reptiles have spilled over hills and forests and speciated from just one dispersal event each is known as adaptive radiation which is when there is a rapid evolution of many species from just one ancestral line. This happens because if there is little competition pushing back, it is much more likely mutations will survive natural selection and potentially allow a new species to flourish over time.
This phenomena has happened with many of New Zealand's bird lineages as well. Around the world, most rails, which are birds from the ridai family like swamp hens and mohens, are semi-aquatic opportunists that forage for most types of food found in their wetland habitats. However, on New Zealand, rails are unusually diverse. There is the takah, but also the waker, a species of rail which has evolved to be larger and live in drier habitats where they have become considerably more predatory, hunting for small reptiles and mammals. Most other members of the family are omnivorous as well, but usually ignore animals like these. There is also a family of native parrots on New Zealand that are found nowhere else in the world named the strogidai that descend from one lineage of parrot that made its way to New Zealand. There are nine species of parrots on New Zealand, so they aren't that diverse in number, but these parrots are unusually diverse in their body shapes and behavior. The Kia is the only predatory parrot in the world. They aren't classed as true birds of prey because they are still omnivorous and sometimes scavenge, but a significant part of their diet can be made up of animals they have hunted. As a consequence of their diet, they have developed an overhanging beak and an inquisitive nature. Also, there is a nocturnal flightless parrot named the kakapo, which is the largest parrot in the world and spends their time on the forest floor foraging for plant food.
The kiwi as well has five distinct species that inhabit various corners of the islands, each with different adaptations that help them deal with a diverse climate. Interestingly, genetic evidence shows that despite the ancestral lineage of Kiwis being ancient, the five species are actually quite young in evolutionary terms, being around 5 to 10 million years old. This is likely because New Zealand has actually changed a lot over this time, becoming colder and more temperate, and its animals have changed with it. Over the past 30 million years, the southern continents have slowly moved northward, giving the Arctic Ocean better circulation around Antarctica, calling the Arctic seas, which affected New Zealand. Plus, the collision of the Australian and Pacific plates elevated the land more, not just above the surface of the ocean, but molding the landscape into great mountains within the last 5 million years, making them some of the youngest mountains in the world. In addition to the cooling climates in New Zealand, these new highlands created colder habitats as well, forcing animals to adapt. All kiwi species have adaptations for the cold, but the great spotted kiwi has taken this further to survive in its harsh alpine environments. They have evolved to become the largest kiwi species which naturally conserves heat and they also have warmer plumage. These kiwis are also prolific borrowers. All kiwis burrow but the great spotted kiwi create elaborate multi-entranced burrows to protect them from the elements.
New Zealand's fossil record clearly shows that during the meioene around 15 to 20 million years ago, it had many tropical species of plant and trees. But over time, as the climate transitioned, they either went extinct or declined. However, there are other islands on the continent that have retained some of these species. New Calonia is part of the same great sunken continent, Zealandia. But as the climate has remained stable and more tropical, it acts as a refuge for many ancient Gondwan and plant lineages that have gone extinct in New Zealand. So, Calonia's unusual flora offers a glimpse of what an ancient New Zealand may have looked like. New Zealand also used to be home to animals that are more common in hotter climates, too, like crocodiles. But also, fossil material has been discovered of the pelvic bone from a giant turtle that once lived here millions of years ago. Study of this material shows that the turtle was likely related to Molania, which was a giant horn turtle that used to live in New Calonia, and that went extinct as little as 2,000 years ago. They were around 2 1/2 m long, weighing as much as a brown bear, and were completely herbivorous.
So, New Zealand, as an isolated piece of land, traces its origins back to before the extinction of the dinosaurs. And although it has many plants and animals that bear a striking resemblance to fossils of this time, this can't be said for all creatures or even most that have radically changed to suit new challenges that arise in their environment and are forever changing. Thank you again to Planet World for their support. To see Planet Wild in action, you can watch their mission saving seahorses here. A big thank you goes to all my patrons, especially the big contributors that are listed here.