How many species are in your house?

Most ecologists are oblivious to the shockingly high biodiversity in front of their eyes every day. Our new paper explores the astonishing biodiversity in an urban Australian home - a house of a thousand species.
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We spend more than half our lives in our homes, so shouldn’t every ecologist roughly know how many species they live with? 

It wasn’t until we got locked down in our house during COVID, that we set out to finally answer this question for our property in Annerley, QLD, Australia. Annerely is an inner-city suburb 2.7km from downtown Brisbane. The house occupies roughly half of the 430 sqm piece of land and is only a block or two away from a main arterial road, train station, hospital, apartments, and shops. When we showed photos of the house and described our survey methods to 157 professional ecologists - they, on average, guessed we'd find 200 species over the year. 

Surprisingly, we found 1,150 species in our house and yard. 

So why was the actual number of species present so high and why was the average professional Australian ecologist so wrong? The simple answer to both of those questions is insects! 

Bar plot of the 436 lepidoptera, 109 diptera, 103 plantae, 95 coleoptera, 88 hymenoptera 78 hemiptera, 63 arachnida, 56 aves, 49 other insects, 30 other arthropods, 13 fungi, 11 mammalia, 8 reptilia, 5 mollusca, 2 amphibia, 2 other animal, and 2 annelida we found
Number of species across different groups of organisms from Rogers, Holden & Yong (2023). https://doi.org/10.1002/ecy.4225

Moths

Shockingly, we found 436 species of moths and butterflies. A few moths were vibrantly coloured, and nearly the size of a human hand. For example, three species of large fruit-piercing moths in the genus Eudocima, fed on the neighbourhood fruit trees.

Dot-underwing moth (Eudocima materna) found in our stairwell.
Matthew Holden

However, most of the moths we found were tiny and barely noticeable. They may seem dull in comparison until you put them under a microscope or learn about their behaviour. For example, Scatochresis innumera is a micro-moth (pictured below) that lays its eggs in possum poo. Its caterpillar spends its entire life feeding, and even pupating in a single scat. Another species in the Scatochresis genus specialises in koala poo, but unfortunately, this species, nor Koalas, could be found on the property.

A tiny moth, Scatochresis innumera,  
through a microscope.
Russell Q-Y Yong

Natural enemies

The house was not only teeming with fruit and poo-eating moths but also predators who ate them, such as spiders. We found 56 spider species.

Giant huntsman, Heteropoda sp, eating a cricket.
Matthew Holden.

One of the more fascinating predators was the thread-legged assassin bug. Some of these bugs pluck at spider webs, and when the spider comes to check out their “meal” they find out that they are indeed the meal of this clever assassin.

Over half of the 88 Hymenoptera species (ants, bees, and wasps) on our property were parasitoid wasps, laying eggs in or on their hosts. When the eggs hatch, larvae emerge to feed on the host (often from the inside out) eventually killing it. Given the number of different butterfly and moth species, it is not surprising that parasitoid wasp diversity was high. These wasps often target moth and butterfly caterpillars.

A parasitic Braconid wasp in the subfamily Euphorinae.
Matthew Holden.

Natives abound

One hundred of the 103 plant species were non-native. There were also a few invasive insect pests. For example, the citrus mealybug, Planococcus citri, fed in our garden, and the flatworm, Platydemus manokwari, consumed snails. P. manokwari contributes to native snail population declines around the world. Our record of this species is the first in Australia’s leading biodiversity database, the Atlas of Living Australia.

Citrus mealybug, Planococcus citri, feeding
on a plant in our yard. Russell Q-Y Yong.

But these invasive pests were exceptions. The overwhelming majority of the animals in our house and yard were native, and most of these native species were insects. This included several bee species, like native stingless bees, blue-banded bees, and fluffy teddy bear bees. The latter two species slept in the hedges under our windows at night.

Blue-banded bees sleep by grasping
plant stems with their mandibles.
Andrew Rogers

Even the vertebrates were mostly native, including possums, flying foxes, kookaburras, brush turkeys, and rainbow lorikeets. A blue-tongued skink lived under the house slab - just one of five native skink species on the property. During the rainy season, we were serenaded by the calls of green tree and stripe marsh frogs. However, quite surprisingly, we did not find any cane toads.

Common brushtail possum, Trichosurus vulpecula. Matthew Holden.

A big reason for all the native wildlife in our yard was the varied vegetation: the shrubs, trees, and weeds in the yard. The monotony of a perfectly tended lawn may be nice for the kids to play on, and heavily sprayed and manicured flowerbeds may be nice to look at, but, as a habitat for urban wildlife, they are lacking.

We did little work in the garden. However, by not spraying or mowing, and by sacrificing some lawn for native trees, shrubs, and weeds, we ended up with an urban home teeming with wildlife - something much more valuable.

Even the most well-kept properties will be home to many species. Everyone, including ecologists, will be shocked by the biodiversity in their homes – all we need to do is take a closer look.

References

Rogers, A, M H Holden & R Q-Y Yong (2023). The house of a thousand species: The untapped potential of comprehensive biodiversity censuses of urban properties. Ecology. https://doi.org/10.1002/ecy.4225

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