Pale Swallowtail Butterfly 2015 02 19
A pale swallowtail butterfly. Image: Jason Goldman

"Did you play any stick sports as a kid?" That's the first thing Elizabeth Long asked me when we met at Charmlee Wilderness Park in Malibu, on the coast just west of Los Angeles. Her theory is that people who have experience playing baseball, hockey or lacrosse come prepared to skillfully wield the butterfly net she then handed me. I was probably nine or ten years old the last time I held a baseball bat, and before we'd even left the parking lot my dreams of scampering through the fields happily netting butterflies quickly dissolved.

Our mission was to hike several sites in the mountains and take note of the butterflies we saw. In addition, Long was hoping to capture a few specimens to add to the Natural History Museum's entomology collections. But this wasn't just a stroll through the park. She was also looking for clues to solve a mystery.

The Santa Monica Mountains begin in Hollywood and stretch out 64 kilometres to the west before giving way to tidal lagoons and sand dunes and eventually the chilly Pacific Ocean. At the eastern end of the range lies Griffith Park, one of America's largest urban parks. Researchers Tim Bonebrake and Dan Cooper discovered recently that the butterfly community there has changed dramatically over the past one hundred years. Thanks to historical records and preserved museum specimens, they found that of 55 native butterfly species known to have fluttered about the peaks, valleys and arroyos of the park in the early twentieth century, ten of them – 18 percent – had disappeared by 2012. They apparently vanished, without a trace.

Some might be surprised that Los Angeles was once (and still is) home to so many native butterflies. The city, equally famous for its film industry and for its traffic, is also part of a global biodiversity hotspot called the California Floristic Province. What is perhaps less surprising is that a century of climate change and increasing urban development has been associated with a loss of nearly one in five native butterfly species from the park.

Long is now extending that study beyond Griffith Park to the rest of the Santa Monica Mountains, a range characterised by a mosaic of federal, state, county, and city governed public lands and private properties, punctuated by two major highways and lots of roads. By surveying a series of sites along the remainder of the mountain range approximately every three weeks, Long aims to find out which butterflies are present now, and compare her data both to information collected nearly a century ago and to the Griffith Park study.

In the world of butterflies, monarchs are like the giant pandas: they're well known, charismatic critters. But as we set off into Charmlee Wilderness Park, our first of three sites for the day, I quickly learned that most of the butterflies I thought were monarchs were, well, not. Monarch butterflies do migrate through California – there's a population west of the Rocky Mountains that migrates, though not quite as impressively as those that fly from Mexico to Canada and back – but most of the critters I immediately identified as monarchs were actually painted ladies. It's a reasonable mistake to make: painted ladies are excellent monarch mimics.

Everybody we met walking around the park – who immediately sized us as lepidopterists (butterfly researchers) thanks to our giant nets – had something to say about the monarchs. But most of the butterflies we observed – and all the ones we netted – were others. There were a handful of painted ladies, plenty of California sisters, and also tiger swallowtails, pale swallowtails, red admirals, white checkered-skippers and at least one mournful duskywing. Biodiversity hotspot indeed.

Our second site was a trail in Leo Carillo State Park. After several successful captures and lots of flailing about, Long encouraged me to take a swing. The idea was possibly to convince me how difficult it is to successfully catch a butterfly, so that I'd judge her own flailing about less critically.

White Checkered Skipper Butterfly 2015 02 19
A white checkered skipper. Image: Jason Goldman

Unlike other types of fieldwork, butterfly research hasn't benefited from all that much innovation in recent decades. The lightest of GPS trackers is still too heavy for even the biggest of butterflies. Camera traps are useless for detecting them. The lepidopterist's toolkit doesn't look all that different from a century ago: hiking boots, binoculars, notepad, butterfly net. Researchers like Long can now extract their DNA to rapidly determine the genetic makeup of each population of butterflies in each canyon along the mountain range. But first you have to catch one.

I spotted a California sister flying along the hiking trail only a couple feet off the ground. I readied my net, holding it in both hands like a Klingon Bat'leth, ready to strike. The metal pole felt cool between my hands. The goal, as I understood it, was to snap the pole towards the butterfly. It reminded me more of throwing a Frisbee than of swinging a baseball bat.

Beads of sweat collected on my forehead. The rest of the world melted away, and it was just me, my net and the butterfly. Once it was trapped helplessly inside the net, you twist it around to prevent the bug from escaping its fate. How hard could it be?

“There is no graceful way, I discovered, to swing a butterfly net.”

Butterflies may look like delicate bugs, flapping their wings as they drift lazily from flower to flower, but the truth is they are highly skilled pilots, able to weave and dodge their way out of the path of a net without breaking a sweat. They're scrappy insects. It is not easy to catch a butterfly.

As if the sister could foretell the future, suddenly it arced at least twenty feet into the air. There is no graceful way, I discovered, to swing a butterfly net. Somehow this particular butterfly knew that I was trying to show off my field research skills. So she left me to jumping up and down, waving the net through the air in utter futility like an idiot.

And what did my foe do next? As soon as she was out of my strike zone, she returned to the ground, hovering along just above my knees. If butterflies can laugh, and I'd like to believe they can, then this butterfly laughed so hard that tears fell from her eyes.

By the end of the day, I did manage to snag one. By accident. I swung for it and missed, and then the confused butterfly flew itself right into my net anyway. I didn't even realise it. From a few paces down the trail, Long shouted at me to twist the net to prevent the butterfly from flying out. She dispatched the critter quickly and carefully, placed it into a small envelope and labelled it with the time, date and location. 

California Sister Butterfly 2015 02 19
A California sister. Image: Jason Goldman

Eventually, Long will be able to determine whether the missing Griffith Park butterflies have disappeared entirely from the mountain range, or whether they still persist elsewhere, hanging on to existence in a rapidly changing environment. Whichever the case, her research will reveal important information about the ways in which development in one of the most highly urbanised cities on the planet impact the wildlife with which we share our neighbourhoods. 

After a few days my butterfly will get pinned and join the Natural History Museum's collections as permanent record of its presence in the Santa Monica Mountains. Perhaps a hundred years from now, entomologists will be able to compare the butterflies living in the Santa Monica mountains (or, at least, the parts of the mountains that still remain above sea level) to the data that Long will have collected.

A century-long drama is unfolding in the mountains that cut Los Angeles in half, and most of us zip along the freeway without giving it a second glance. Still, each week Elizabeth Long sets out for the mountains armed with little more than a notebook and a butterfly net. 

Top header image: Sequoia Hughes, Flickr