Tuesday, April 3, 2018

What do we know about flying ants?

When I began my research career I had the snobbish idea that I would not study a particular organism, site, or system.  I would instead come up with a grand question, and study any aspect of the world I needed to in pursuit of the answer.  This, I thought, was the way real scientists work.

Nearly a decade in, I have mostly tossed that archaic idea.  Rather than imposing ideas upon the world, I am more productive when I let nature guide me.  The best way for me to discover is to pick one thing in the world around me and try to figure out how it works.  Each answer reveals more questions, setting off a chain reaction of discovery.  An added consequence of this inspiration from the world is love for it.

I have come to realize, for example (despite my earlier snobbish pretensions), that I love ants.  Queens in particular—the mothers, explorers, and true individuals of ant societies.  I don’t just mean that I find them interesting or practical to study (although they are endlessly fascinating and useful).  When I see them in the wild, read about them, think about them, I get pangs of excitement and sympathy.  I occasionally dream about them.  On optimistic days, I even dare to think I understand them.



In most ant species, young queens have wings and fly to find mates or disperse to new nest sites (Aphaenogaster flemingi queen, photographer April Nobile, from AntWeb)

About a year ago, letting my mind wander during a particularly boring meeting, I realized I had devoted a good chunk of my life to understanding what it means to be an ant queen.  I spent years trying to wrap my mind around that dangerous part of their life when they leave their birth nests to fly through the atmosphere to find mates and new homes.


“The swarms of some ant species are among the more dramatic spectacles of the insect world.”
Bert H̦lldobler & E.O. Wilson РThe Ants

One of the only other people to devote their research so thoroughly to ant flight was the 20th century ecologist Mary Talbot.  And our knowledge of ants has advanced a lot in the decades since Talbot’s pioneering work.


“…the brief interval between leaving the home nest and settling into a newly constructed nest is a…dangerous odyssey that must be precisely timed and executed to succeed.” – The Ants

My idle musings led eventually to a review paper, published recently in Myrmecological News.  In the paper, I use new conceptual developments to weave together all that we know about what flying ants do in the air.


“No encompassing theory exists to explain the extreme variation in the patterns of mating behavior so far observed.” – The Ants

Several discoveries stand out.

Queens face hard choices.  They can, for example, choose to store lots of fat and protein in their bodies before they leave their nest to fly.  Doing so makes it easier to survive alone while they are trying to rear their first offspring.  But it may also make them less able to evade predators, find mates, or discover a suitable home.

Queens carry heavy burdens.  The pressure to load up on nutrients and still be able to fly has led to the evolution of extreme weight-carrying ability.  Some ant queens can carry ~1.5 times as much weight as other flying insects.

Ants can fly longer than we thought.  Some queens can fly for over an hour straight and some males may fly repeatedly over several days or weeks.  Queens of some species occasionally fly 20 miles in one go.

Ants are part of the atmosphere.  Queens and males enter the atmosphere in their millions, flying high to find mates, ride on air currents, and search for new homes.  There they form a major food source for birds, dragonflies, bats, and other predators.  They also transport energy and materials, including toxins like mercury, long distances across landscapes or among food webs.



I have spent much of my career trying to understand what ants do in the air (Dorylus driver ant male with author, photographer Alex Wild)

There is still much more that we don’t know about ant flight, especially when you consider that there are probably over 20,000 ant species in the world.


“…the reproductive behavior of ants is still a poorly explored domain with rich possibilities for general evolutionary biology.” – The Ants

In other words, there’s plenty of room for me and everyone else to continue exploring (and loving) ant queens.

Monday, March 5, 2018

Invasive acacias can benefit Bornean ants

A primary goal of conservation is to protect intact lands and waters.  High quality habitats like old-growth forests, unplowed grasslands, and unfished coral reefs are essential for the future of the world’s biodiversity.

Less pristine areas, however, also play a role in conservation.  Working landscapes like ranches, sustainably logged forests, easements along highways and power lines, and environmentally friendly farms, can be valuable tools for protecting our natural heritage.  Even lands that have been heavily impacted by farming or development can be restored to some semblance of natural vegetation.

Compared to areas that have never been damaged, however, working landscapes and restored areas often harbor fewer native species or function less effectively.   They are also more likely to contain invasives—organisms that have been transplanted by humans from other regions and that alter or harm native ecosystems.  Invasive species are a leading cause of extinctions, and transporting living things outside their native range is generally not a good idea.  Once established in a new area, many non-native species are difficult or impossible to eradicate.  But when doing conservation on highly degraded or working landscapes—habitats that are not, and may never be, pristine—exotic species can sometimes help deliver conservation benefits that would otherwise go missing.

The degraded landscapes around Gunung Palung National Park and elsewhere in Borneo illustrate this idea.  Over the past few decades rampant development has reduced most of Borneo’s original forest cover to sterile agricultural landscapes covered by oil palm plantations, rice paddies, or slash-and-burn farms.  These open disturbed areas are prone to erupting into wildfires which further eat away at the island’s remnant forests.  Most of the island’s native species, adapted to living in dark wet forests, cannot tolerate these conditions.  The result is that megadiverse rainforests are slowly replaced by barren areas dominated by a handful of plants that thrive in direct sunlight and can survive fire—mostly native alang-alang grass (Imperata cylindrica) and bracken ferns (Pteridium aquilinum).




Human-caused wildfires kill rainforest trees, but favor alang-alang grass and bracken ferns which need direct sunlight and resprout quickly in burned landscapes


After years of logging and burning, Bornean rainforests transition into man-made grasslands.  The condition is hard to reverse since few trees can survive the direct sunlight, frequent fires, poor soil and intense competition from grasses and ferns.

Restoring these areas is difficult, as most rainforest trees need dark, moist environments to grow.  Soils in the man-made grasslands are often impoverished after years of burning and erosion from heavy rains.  And the densely packed grasses and ferns crowd out any tree seedlings that could otherwise survive the harsh climate.

But one non-native tree thrives in these conditions.  Acacia mangium is native to eastern Indonesia, New Guinea, and northern Australia, but is now one of the most common non-native trees in Borneo.  It grows rapidly in open sunny areas (3 to 4 meters per year!), and quickly colonizes areas that have been burned or disturbed by humans.  It is also a legume, able to acquire nitrogen straight from the atmosphere with help from symbiotic bacteria, so it does fine in poor exposed soils.  Best of all, since it needs open sunlight to grow, it does not invade native rainforests, and its seedlings cannot survive under its own canopy.  Once a stand of Acacias grows tall enough to shade out the direct sunlight, the understory can be colonized by native rainforest species without competition from young acacias.  For all these reasons, people often plant Acacia mangium to help restore mines, logged areas, and other degraded landscapes.

Acacia mangium forests have become one of the most common habitat types in disturbed lands around Gunung Palung National Park, and the trees accelerate the transition from grassland to rainforest.  They restore soil that has been burned off or washed away, provide shady areas for native rainforest seedlings to germinate, and by blocking direct sunlight they kill off the alang-alang grass and bracken ferns that crowd out tree seedlings.  Given time, acacia forests revert to native secondary forest as rainforest trees replace acacias in the canopy.




Acacia trees thrive in sunny barren environments and form canopies that shade out and kill alang-alang and bracken ferns, creating the cool dark conditions necessary for many rainforest seedlings.  This Acacia forest began growing only 11 years ago after a wildfire, and is now ~20 meters tall.

Many of Borneo’s native animals can also survive in semi-natural acacia groves.  Last year, we set out to see what ant species called this new habitat type home (find our paper here).  We studied a young acacia forest that had sprung up after a wildfire 11 years before, and was starting to transition to native secondary forest.  Compared to native rainforest, the acacia forest harbored relatively few species.  But almost all of them were native, and a few invasive species were absent that were common just a few hundred feet away in farmlands and towns.  The major exception was the yellow crazy ant (Anoplolepis gracilipes), a notorious invader that has colonized many Pacific and Indian Ocean islands, and which was the most common ant in the acacia forest.  Nonetheless, the ant community here was more intact than nearby open areas.


Semi-natural Acacia mangium forests in Borneo are species poor compared to native rainforest, but still harbor more forest species and fewer invasives than nearby disturbed areas (poster by Sara Helms, photos from AntWeb or taken by author)

Our results suggest that these non-native trees are a useful conservation tool in disturbed landscapes in Borneo.  In highly degraded areas, sometimes a non-native is better than nothing at all.

Monday, April 3, 2017

Urban reforestation

Last week I got to do something I’ve fantasized about for years—urban reforestation.

Our organization here in West Kalimantan does a lot of reforestation work in Gunung Palung National Park.  We plant native rainforest seedlings in areas that are important for wildlife but have been illegally cleared for timber or farmland. One site is in a hilly area that was clearcut and then burned repeatedly until the forest was replaced by man-made grassland.  Another site is a peat swamp that was cleared to make rice paddies.  And earlier this year we planted on land recovering from years of use for farms and plantations.

But our newest challenge may be the most difficult yet.  We’re working to restore 0.5 hectares of urban landscape to native rainforest.





Our newest reforestation effort targets narrow belts of land around a private clinic

The land in question has a long history of abuse by humans.  It was farmed for years, and some small buildings were built on it.  Then in 2006 the vegetation was completely destroyed by a human-caused wildfire, paving the way for the plot’s invasion by invasive Acacia mangium trees.  After nearly a decade of regrowth the vegetation was again completely destroyed, this time by bulldozers.  Construction workers followed the bulldozers, covering some of the site in gravel and concrete, and using the rest as a dump.   The land today is covered in scraps of sheet metal, cans of paint and chemicals, and other garbage, much of which has been burned to form twisted piles of toxic ash and melted plastic.  There are even the ruins of an outhouse, the concrete toilet holes now filled with sand.





The land has been severely degraded by human activities, and many areas are now covered in concrete or trash

For years this land has been valued only for what people could get out of it, put on it, or dump in it, and we’re trying to change that.  If left alone this land could once again become valuable rainforest, and we want to ensure that happens.

To that end, last week we planted nine hundred seedlings of around fifteen native species.   What’s more, we turned our reforestation vision into an educational opportunity by inviting local teenagers to help.  Around 20 students volunteered after school to prepare the site and plant seedlings.


Teenagers from our conservation education programs volunteered to help plant native seedlings…









…and so did nurses, doctors, and other clinic staff

Although this project is relatively small—900 trees on ~0.5 hectares—it could have a huge impact.  It’s in a critical area bordering the national park and surrounded by rapid development.  The newly planted land will serve as a corridor that extends the park’s forest an extra 400 meters to a nearby road.  Just two years ago red leaf monkeys (Presbytis rubicunda) and silvery lutungs (Trachypithecus cristatus) could be seen from the roadside.  Then the land was bulldozed, new homes and businesses popped up nearby, and the monkeys disappeared.  The most commonly seen animals today are foreign invaders like tropical fire ants (Solenopsis geminata) and Eurasian tree sparrows (Passer montanus).

By ensuring rainforest once again reaches to the road, we not only hope to return the monkeys and other native species, but also keep wildlife populations on either side from becoming isolated by development.





We hope to create a narrow belt of forest extending all the way to the roadside to prevent development from fragmenting wildlife populations

The urban conditions are challenging for the seedlings—planted in compacted gravel or among concrete building foundations, exposed to fierce sunlight, and drawing nutrients from soil polluted by chemicals, metals and burned plastic—and we expect fewer to survive than normal.  But we’re optimistic.  Rainforests have thrived here for tens of thousands of years, and they can do so again if we let them.

I can't wait to see how these seedlings look in a few years.

Tuesday, February 14, 2017

Virtual fire ants

Last month I published my first computer modeling paper.  I understand the power and value of simulation studies, but I’m not usually a fan of them.  I tend instead to do projects that involve field experiments, collecting specimens, or measuring things in a lab.  But after years of collecting data on dozens of real-life ant species, I thought I had enough information to create a realistic virtual one.

A computer simulation would allow us to test ideas that would be difficult or impossible to test in real life.  We could, for example, build a virtual ant population and watch it evolve over generations.  And we could do that repeatedly with many populations at the same time.  In just a few days we could have 25 virtual years of data from hundreds of simulated worlds.  Getting the same information in the field could take a whole career.

So we got to work designing virtual ants.  We made a program that created worlds inhabited by ant colonies whose properties we could tailor as we saw fit.  We could then see how tweaking the biology of ant colonies—how they grew, died, and reproduced—affected their populations.




Our program followed ant colonies over several generations as they were founded, grew, acquired territory, reproduced, and died (figure adapted from Helms & Bridge 2017)

Our ant of choice was the red imported fire ant (Solenopsis invicta).  We chose to work with fire ants for three reasons.

1) We know a lot about them.  Programming a realistic animal requires a lot of information, and fire ants are perhaps the most studied ant on the planet.  We have detailed field measurements of how and when they reproduce, how colonies grow and compete for space, and how long they live.

2) They are important.  Fire ants are an invasive species in the US and elsewhere.  Farmers, governments, and conservation organizations around the world want to know how they spread.





Fire ants were accidentally introduced to Alabama in the 1930s and have since spread throughout the southern US (figure from Calcott & Collins 1996, The Florida Entomologist)

3) They are interesting.  Fire ants are a model system for studying alternate reproductive strategies.  They have a complicated life history and reproduce in several ways.  Colonies produce queens that fly off and found new colonies in vacant soil, but they also produce parasitic queens that take over other colonies of the same species.  So by studying them we could learn how parasitic ants evolve, and how the evolution of parasitism affects other aspects of their biology.  (Fire ants have plenty of other odd twists in their biology as well, but for this study we focused on parasitism)





Fire ant colonies practice two reproductive strategies—they produce some queens that found new colonies and other, parasitic, queens that take over existing colonies whose previous queens have died

Once we had our program and our virtual ants, we ran a couple experiments.  In the first, we set up different ant populations that varied in how colonies reproduced.  In some populations colonies only produced queens that founded new colonies, whereas in others half the queens produced by colonies were parasites, and other populations fell somewhere in between.  We then tested whether producing parasitic queens affected the demographics of populations—how large or how spread out the colonies were.

In our second experiment we created mixed populations inhabited by several lineages of ants.  Some lineages produced lots of parasitic queens and others didn’t.  We then watched the populations evolve over time as some lineages survived and reproduced more effectively than others.

We found that populations that produced more parasitic queens had larger colonies and occupied more of the available habitat.  Populations that don’t produce any parasitic queens, on the other hand, spread faster.  This is because parasitic queens can only take over existing colonies—they can only survive in areas already occupied by fire ants.  But queens that found new colonies can survive anywhere that isn’t already claimed by an existing colony.

When it comes to evolution, it turns out that location plays a deciding role in which strategy is favored by natural selection.  Populations at the edge of an expanding range, which are surrounded by suitable empty habitat just waiting to be colonized, evolved to produce almost no parasitic queens.  Conditions are nearly opposite in the interior of the range, which is saturated with existing colonies and contains little free space in which to found new ones.  Not surprisingly, populations in those areas evolved to produce more parasitic queens.

No computer model is supposed to be entirely accurate.  Models are instead meant to be useful for teasing apart how different factors influence a process.  What we need now is a field study to see whether we see the same patterns in nature that we do in our model.  That’s a project for another day…

So while a computer simulation was way outside my comfort zone, it did have one thing in common with all good research—it raised just as many questions as it answered.

Saturday, January 14, 2017

How to start an ant lab in the rural tropics

Borneo is one of the most important areas in the world for urgent ant exploration.  It is home to a high number of ant genera, is estimated to contain hundreds of undescribed species, and is under extreme conservation threat, with over half its land area cleared for farmland in just the past few decades.

But we still know little about the ants of Indonesian Borneo.  Most ant research in Borneo occurs in Malaysia or Brunei—the two countries that share the island with Indonesia—even though they cover only a small minority of its land area.  As far as ants are concerned, the three fourths of the island that happen to fall on the Indonesian side of the border are pretty much a blank spot.

So for the past few months I’ve been setting up a lab here in Sukadana, making us the only hub of ant work for hundreds of miles in any direction.  But starting a lab in rural conditions in the wet tropics required a bit of improvising.

Getting ethanol, for example, is almost impossible.  There is a medical supply store in the provincial capital of Pontianak, a 4 to 5 hour boat journey away through the winding Kapuas River delta.  But even they don’t sell ethanol.  Ethanol must be special ordered in Jakarta, shipped overseas to Borneo, and transported to Sukadana by riverboat.  This complex supply chain drives the cost up to a staggering forty US dollars per liter.

Stymied by geography and economics, we are forced instead to preserve specimens in rubbing alcohol, which is available in Pontianak.  Even that takes time, with the alcohol arriving by riverboat a few weeks after ordering.


To collect data in support of our conservation work, I’ve set up an ant lab in Indonesian Borneo

I brought some basic equipment with me from the US—microscope, lamp and bulbs, forceps and insect pins.  But much of the rest of our gear is pieced together from supplies available at local hardware or grocery stores.

I built a litter sifter, for example, out of two paint trays, some wire mesh, duct tape, epoxy and a can of spray paint.


I made a litter sifter to sort ants and other insects from piles of decaying leaves.  This one consists of two layers—a top one to hold the litter…


...and a lower one, spray painted white, to catch the insects that fall through the mesh.


To find ants inside rotting logs and vegetation, I bought a locally made machete.

To collect ants once we find them, we built pooters out of plastic tubing, rubber bands, and either a thin cloth or soft mesh from a kitchen strainer.


A pooter is a long straw that lets you use lung power to suck up ants, but prevents them from going into your mouth

To store specimens once they’ve been collected, Brian Fisher recommended I use plastic containers with mothballs and a drying agent.  I lined my containers with packing foam that Sara and I used on our move from the US, and sealed it in place with Elmer’s glue.


A plastic container, packing foam, a mothball, and some silica gel make a decent specimen drawer

After collecting and storing ants, the final technical hurdle was finding a way to view them under a microscope.  For this step I adapted a trick I learned at Ant Course in Uganda.  I placed a plastic ball inside a spool of electrical tape, and put a blob of modeling clay on top of the ball.  By sticking the pin in the clay and rotating the ball in its socket, I can view specimens at just about any angle.



A homemade ball-and-socket joint, with a dab of modeling clay or old chewing gum, can be used as a stage for looking at specimens under a microscope

With all our equipment in place, we are finally ready to begin collecting ants.  We’ll start with a couple projects to see how local slash-and-burn farming practices impact ant communities, and how our reforestation efforts help undo the damage.

I can’t wait to see what we find!