Why are New Zealand’s cicadas so loud this time of year - and is it dangerous?

Cicadas emerge from December to March, with males buzzing loudly to attract mates. Photo / Getty Images

By Nik Dirga of RNZ

Explainer – Depending on your tolerance, it’s the iconic sound of a Kiwi summer or a drill buzzing into your ears.

The seasonal serenade of cicadas kicks off as the weather warms and typically peaks in February. But how and why do these insects make such a loud noise?

Here’s a primer on how New Zealand’s annual cicada season works.

Why do they make so much noise?

They want some love.

Cicadas emerge from the ground, typically from about December to March, to spend the rest of their brief lives trying to mate. The males make their distinctive buzz as they’re desperately seeking some sweet, sweet cicada loving.

“I love it,” says Julia Kasper, Te Papa’s lead curator of invertebrates. “It’s beautiful, it’s the sound of summer and still very exotic.

“That’s basically the noise of a wedding. In summer, all the adults are emerging from nymphs that live in the soil.”

Cicadas spend most of their lives underground. The New Zealand varieties typically live as nymphs for two to three years before shedding their final shells and emerging as adults.

In some parts of the world, what are called periodical cicadas can spend as long as 17 years underground, such as in the eastern United States, where trillions of them can burst forth in a single season.

“It’s the males that sing, calling for the females, trying to be the loudest, the coolest, the best and getting, you know, the prettiest girl, and the girls are moving towards the males,” Kasper says.

Male and female cicadas. In most cicada species, females are larger. Photo / Getty Images

Of course, not everyone adores the cicada’s call.

“Some people love the sound,” says Professor Grant Searchfield, head of the department of audiology at the University of Auckland.

“[For them it’s] ‘the sound of summer’, so it’s not bothersome at all, but some people may find the sound annoying or are more sensitive to sound.”

A cicada’s song can hit more than 80 decibels, studies have found.

That’s within the range of “dangerous” sounds as defined by the American Academy of Audiology, which lists power tools, concerts and sporting events as hitting the same benchmarks, where damage can be caused with repeated exposure.

Aircraft can hit more than 120dB during takeoff, while gunshots can reach more than 150dB, well within the range of causing hearing damage.

How does such a small insect make such a huge sound?

Cicadas come with a built-in amplifier, a special organ called a tymbal.

“It’s amazing, and we still know so little about it,” Kasper says.

The tymbal sits in the insect’s thorax, “and it’s basically a drum. You can see it from the outside, it’s almost like it looks a bit like a window in their side”.

Many insects, such as crickets, make noise by rubbing body parts together. In the cicada’s case, the tymbal contracts and expands, pulling a ribbed membrane back and forth so quickly that it can sound to humans like a continuous sound.

“It’s so complex it’s unbelievable,” Kasper says, noting that studies using slow-motion video reveal how intricate the cicada’s song is. Humans may not be capable of hearing some of the sounds.

Our ears may not always discern it, but every species of cicada has a different song.

How many cicadas are there in New Zealand?

Cicadas are found all around the world, but there are at least 42 distinct species in New Zealand. There’s even a species endemic to Norfolk Island. The most common is the Amphipsalta zelandica, or chorus cicada.

One species lives high in the mountains of the South Island, which is the world’s only alpine cicada. It can freeze and go dormant.

Can some years be louder than others?

The size of each year’s cicada eruption depends on many factors.

“Every year is kind of different,” Kasper says. “The rainfall and the dryness and the humidity. Cicadas need moisture and warmth.

“If it’s too dry, they can’t get out of the soil to emerge, and if there’s too heavy rain, they’re probably washed off and drowned. It needs to be the right mixture.”

That means the peak cicada noise may be at a different time each year.

New Zealand has at least 42 cicada species, with noise levels varying yearly due to weather conditions. Photo / Getty Images

Are they the loudest insects in the world?

Certain cicadas sure are.

If you’re getting sick of hearing them out on the deck this month, take a moment to be happy you’re not living in the habitat of the African cicada, Brevisana brevis, which can hit 106.7dB and has been named the world’s loudest insect by Guinness World Records.

Can cicadas damage your hearing?

“Potentially, but unlikely in reality,” Searchfield says.

“If the cicadas were close enough to the ear, and you couldn’t get rid of them – they were there for hours – it’s possible. But a cicada that close would normally be flicked away.

“It is unlikely, but not impossible, that cicadas could cause hearing loss.” Generally, however, the sound is more irritating to some than dangerous.

Still, try to avoid sticking a cicada directly into your ear at this time of year, although that’s really pretty good advice any time.

Is there anything I can do to make them quieter?

“I never thought of that question because they’re so lovely,” Kasper says.

“I guess you could make your garden very bird-attractive, because birds feed on them.”

Searchfield advises against using earplugs, as they can make you more sensitive to the sound.

“Close the doors and windows and, if you have air conditioning, turn it up – there are sound conditioners, used to drown out noisy city sounds, that could be used. I’d suggest trying to think of them as your friendly reminder that the sun’s out.”

But as they say, all things must pass, and the cicada serenading season will end by about March as the last heartsick males give up the ghost.

“They only live for two weeks or so [once they come up],” says Kasper. “They’re only there to mate, and that’s why they sing.”

Until next year, that is, when the buzzy sound of summer will kick off again.