When we talk about the damage introduced predators cause, birds often get top billing. And understandably so. Rats prey on eggs and chicks, compete with native birds for food and can have a devastating impact on vulnerable populations.

But look a little closer, and a little lower, and there’s another world being affected.

Rats don't just eat birds. They eat insects, spiders, wētā, snails and other invertebrates too. And while these smaller creatures might not attract quite the same attention as a kākā or kiwi, they're doing some seriously important work behind the scenes.

The small stuff matters.

An ecosystem is a web, and some of its smallest inhabitants are holding a surprising number of threads.

We tend to rally around the animals we can see, hear and connect with. In conservation, that often means the big, beautiful or charismatic species get most of our attention. Invertebrates? Too often they're simply lumped together as “bugs” — or worse, pests.

But they make up an extraordinary part of the natural world, and life as we know it depends on the jobs they quietly perform.

Take our spider.

Spiders are predators themselves, feeding on insects and helping keep their populations in balance. Other invertebrates play completely different roles. Moths, flies, beetles and other insects help pollinate plants. Worms and countless tiny creatures living in leaf litter and soil help break down dead plant material and return nutrients to the earth. Others become food for birds, reptiles and other wildlife.

They're pollinators, predators, recyclers and food — tiny pieces of a big, beautiful puzzle.

A single rat eating a single spider isn't going to change a forest, of course. Predation is part of nature. The problem comes when introduced rats become abundant enough to put sustained pressure on species that evolved without mammalian predators like them.

Suddenly, that little meal caught on camera is part of something much bigger.

A web, not a collection of species.

It can be tempting to think about conservation one species at a time: protect the kiwi, save the kākā, bring back the birds.

But nature doesn't really work like that.

Healthy bird populations depend on healthy forests. Healthy forests depend on healthy soils, plants, fungi and invertebrate communities. Those communities depend on one another in ways we can see, and plenty we're still learning about.

Remove or significantly reduce one part of that web and the effects can travel further than the species being eaten.

That's one reason controlling introduced predators isn't simply about increasing the number of birds we see. It's about giving the whole ecosystem more room to function as it should.

And why should we care?

Even if spiders aren't exactly your favourite backyard visitors, the work happening at this smaller scale matters to us too. We rely on healthy ecosystems for some pretty fundamental things.

Pollinators help wild plants and many of the crops we eat reproduce. Decomposers recycle nutrients and contribute to healthy soils. Predators — including spiders — help regulate other populations. Plants and healthy soils, in turn, support cleaner water, store carbon and create habitat for other species.

You don't have to be a conservationist to benefit from any of that.

Your veggie patch, the food grown by farmers, the trees shading your local park and the birds you hear in the morning are all connected, in one way or another, to the busy little world happening under leaves, inside soil and beneath logs.

Much of it goes completely unnoticed.

Until, occasionally, a field camera gives us a glimpse.

Back to the rat and the spider.

There's something fitting about this tiny encounter.

One rat. One spider. One meal in the middle of the night.

Yet behind it sits an entire network of relationships between predators and prey, plants and pollinators, soil and forests — and ultimately, us.

It's a good reminder that protecting nature isn't only about protecting the big, beautiful or obvious. Sometimes it's about protecting the small things doing very big jobs.