Last week a neighbour’s daughter needed help with her school assignment on native and non-native species in North Sydney. That led me to think about nativism – the protection of native species against introduced ones – and the whole business of native, domestic, and feral animals and plants.
Exotic flora and fauna are a big problem in Australia. The Red Fox (Vulpes vulpes), for example, was introduced to the Sydney area around 1845 because English expats missed their foxhunting. Feral foxes now range over much of Australia. This one was on a farm in Boorowa.
Foxes, together with feral cats, have been responsible for the loss of many of our native fauna, principally smaller marsupials and ground-dwelling birds. North Sydney Council tries to control foxes by baiting them, but with only partial success. Baiting was underway at Ball’s Head this week:
The fox’s spread was helped by the introduction of the European Rabbit (Oryctolagus cuniculus), which in turn became a major pest itself. I’ve seen rabbits in many places; these two were also at Boorowa:
The Common or Indian Mynah (Acridotheres tristis) is another introduced species, but is much less of a rural problem. Mynahs seem to prefer urban areas which are largely “exotic” anyway, so they have become just another scrappy aggressive bird coexisting with other fauna. And scrappy they certainly can be!
Another import that’s not so damaging is the Goldfinch (Carduelis carduelis). It doesn’t directly harm native species, but it does divert food and resources away from them. This one was near the fox in the earlier photograph.
European Honey Bees (Apis mellifera) are now widespread—and vital for many of the exotic crops and fruit we now depend on for food. Ecologically though, they are another import, and while they don’t directly harm native bee species, they do take up a big share of the pollen and nectar resources, like this one on a grevillea flower:
Australia’s list of disastrous introductions goes on and on, and includes species introduced in good faith to solve existing problems. The Cane Toad (Rhinella marina) is one such disaster, now widespread across the north. However a few introductions really did solve problems. The 23 species of Dung beetles introduced from Africa have greatly reduced blowfly numbers by neatly rolling away much of the dung that harboured their maggots. And Cactoblastis Memorial Hall in Boonarga in Queensland celebrates the insect that stopped the runaway invasion of yet another import – the prickly pear cactus.
The prickly pear highlights another aspect of this: the huge number of feral plants that cause problems all over Australia—and the rest of the world. But some are not all bad. For example Pampas Grass is an invasive pest species, but it’s clearly an approved nesting material for this Red Wattlebird:
Highly invasive Lantana (Lantana camara) is described in an Australian government publication as “a Weed of National Significance… one of the worst weeds in Australia.” It is poisonous to livestock (which of course are also introduced animals). Yet native birds eat its fruit and spread the seeds widely, and its flowers feed native pollinators such as this blue-banded bee.
One consequence of the bad name given to exotics is that native plants are now favoured by many suburban gardeners. The plants are usually easy-care, being adapted to the local environment, and include some very attractive shrubs like Grevilleas and small trees like Banksias – here seen with a Rainbow Lorikeet:
Flowering eucalypts, and bloodwoods like this Corymbia ficifolia, are also popular with gardeners:
But that also creates a problem to nativist purists, because many of the favoured plants aren’t locally native—they come from other parts of Australia. Also, they consist of just a small subset of the local flora; less attractive plants are left out. Gardens then only attract the local wildlife that favours the chosen plants, usually becoming the domain of the bigger more aggressive nectar-eating parrots and honeyeaters, like the Rainbow Lorikeet and the Noisy Miner shown in the last two photos. Also, such gardens usually have no thickets, making them unsafe for smaller birds like wrens or pardalotes. The result is a disproportionate increase in the Rainbow Lorikeet and Noisy Miner populations around the cities.
Many of Australia’s difficulties with invasive fauna have arisen since white settlement because the sea had previously insulated our island-continent from the placental mammals evolving in Eurasia. Also, because Australia is big enough to have multiple habitats, what is “locally native” can change over time. For example, many northern birds are extending their range southwards as the climate warms. One example is the Channel-billed Cuckoo (Scythrops novaehollandiae). A hundred years ago Sydney was the southern limit of its range, but that limit is now extending beyond the border with Victoria.
The Channel-bill raises another question – how truly “native” is a bird that spends half the year in Indonesia? A further question – when does an exotic become a native? For example Dingoes (Canis lupus dingo) are generally regarded as native, having migrated from New Guinea via a land bridge less than 8,000 years ago – much later than Homo sapiens, which is not a native species.
But it’s small islands which have the starkest problem with exotic life. Their isolation, size and lack of predator species allow their few native species to develop in ways that render them highly vulnerable to any predator or competitor from a harsher environment. One example occurs in that very special part of NSW, Lord Howe Island:
The island is an extinct volcano, around 6 million years old. It’s always been separated from the mainland by hundreds of kilometres of sea, so is only populated by animals that were once able to fly or swim across. These included the ancestors of this Lord Howe Woodhen (Gallirallus sylvestris):
The Woodhen is a flightless member of the rail family, whose ancestors would have flown to the island after it emerged from the sea. In such a sheltered environment, functional wings were an unnecessary encumbrance, so their descendants became flightless. They also became quite naïve about predator dangers – for example they will investigate any noise, making them easy to lure from cover:
Inevitably as feral cats, rats, dogs, pigs and humans arrived on the island, Woodhen numbers plummeted, down to just 15 by 1980. At that point, the survivors were removed from the island for an offshore breeding program while their major threat, feral pigs, was eliminated. The birds were then restored to the island and provided with ongoing protection, which allowed the resident population to grow back to around 250, until they were evacuated again recently. This time it was because of the current baiting program to eliminate the rat population introduced when SS Makambo ran aground in 1921. To protect them from the poisoned baits the Woodhens were removed to Taronga Zoo. They will be returned to the island in the near future..
The Woodhens were lucky that some people cared enough to work hard to save them. The grim statistic for Lord Howe Island is that 9 out of its 13 endemic bird species or subspecies have become extinct in the last 200 years.
There are plenty of other similar stories elsewhere in the world ranging from catastrophic to relatively benign. One of the less disastrous ones is the feral population of Red-necked Wallabies (Macropus rufogriseus) thriving on the UK’s Isle of Man - one of the few occasions where marsupials have turned the tables on placental mammals! Another is the troop of Vervet monkeys (Chlorocebus pygerythrus) from Africa living on St Kitts in the West Indies, which are quite destructive to the islanders’ crops:
For me, the message is to protect the native species, and discourage exotics, but also not to lose sight of the ‘bigger picture’.