Beware of Crunchy Figs!

Here's a Moreton Bay fig fruit sliced in half.

The fruit of a Ficus sansibarica provides a cozy home for fig wasps.

Recently, the Wildlife Disease Laboratories received an interesting request from Seth Menser, a senior horticulturist at the San Diego Zoo, asking if we could take pictures of plant parts under the microscope. “I would really like to do a couple of shots of a fig cut in half with the fig wasps still inside. I have the figs needed for the shots. And, if you have never seen inside a fig, with the fig wasps, it is a very incredible thing to look at!” We were curious, so agreed to help.

Fig wasp

This amazing view of a fig wasp was taken in our Wildlife Disease Laboratories.

Seth brought up several figs from a Ficus macrophylla, commonly known as a Moreton Bay fig. These trees originate in the subtropical rain forest of eastern Australia but do well in frost-free climates such as ours. These majestic trees can reach up to 200 feet (60 meters) with long, aerial roots providing the tree with additional support to hold up the immense canopy. Seth brought several figs ranging from green and firm to dark maroon with spots on the outside. He explained the life cycle of the fig and the fig wasp as he cut them in half, and we set up the cameras.

Here's one

This female fig wasp has her wings. Is she ready to fly to a new fig?

Ficus trees are unique because the flowering parts of the plants are inside the fruiting parts (figs), making it difficult for insects to pollinate the trees. Thus begins the cooperative relationship with the fig wasp. The fig provides refuge and a food source for the wasps, and, in turn, the wasps pollinate the tree.

To begin the cycle, a tiny female fig wasp enters into a narrow opening (ostiloe) at one end of the fig. While wiggling into this small hole, she often looses a wing or antenna. Safely inside, she lays her eggs. As she is wandering through the fig, she spreads pollen from the fig she hatched in, thus helping the fig tree produce viable seeds. The cycle of the female wasp is complete, and she dies. Her eggs hatch, and the young wasps grow, finding food and refuge in the fig. Interestingly, only female wasps grow wings and leave the fig. The males live their entire life in the fig. Their function is to mate with the females and chew small openings through the fig’s wall for the females to escape, and the cycle begins again.

How many fig wasps can you find in this fig?

How many fig wasps can you find in this fig?

We were totally fascinated by the story. Using a dissecting scope with a camera attachment and a macro lens on a photo stand, we were able to capture the intertwined life cycles of the fig and the wasp. We photographed the narrow ostiole of the immature smooth fig where the female enters. Mature figs looked completely different on the inside. They were soft and fleshy, with delicate flower structures and seeds lightly attached to the inner walls. Each mature fig contained several wingless male wasps, and Seth was lucky enough to find one female flighted wasp.

At first glance, theses tiny wasps are difficult to see. The magnification helps, but a keen eye is needed to see them. How many can you find?

April Gorow is a senior pathology technician with the San Diego Zoo Institute for Conservation Research. Read her previous post, We Never Stop Learning.


What’s in Your Backyard?

A scorpion is caught under UV light.

A scorpion is caught under UV light. Photo credit: Dr. David Aveline

The school year has started, and I’m back to student life in Los Angeles, where I’m starting the third year of my Ph.D. at UCLA. It really isn’t too far from the costal sage scrub in San Diego County where I’ve spent the last few months in the field studying the Pacific pocket mice (see Up All Night with Pocket Mice), but it feels worlds apart. For starters, I’m back on a normal schedule—I’m awake during the day and get to sleep at night! What a luxury. But being up during the nights, and hiking around outside, is a very different experience than anything I had been used to.

I have always been a little afraid of the dark—and extremely afraid of spiders!—so doing nocturnal fieldwork was never something I envisioned. Actually, it wasn’t something I had ever even thought about existing, let alone doing. But when the opportunity presented itself, I jumped right in and have become fascinated with what is happening when most of us are normally sleeping!

Many mammals are active at night. There are about eight species of rodents I regularly see in the coastal sage scrub along with tons of rabbits. Coyotes are also very busy at night; we hear them yipping and howling so often it has become a normal part of the sound landscape. Other carnivores like bobcats and mountain lions are up during the night. I haven’t spotted any myself, though I have caught a few deer in my headlamp. They have huge eyes that appear to glow bright green when the light hits them. Most nocturnal vertebrates have this eyeshine, which is caused by a reflective layer called the tapetum in their eye behind the retina. This allows light to hit the visual censor twice; once when it passes into the eye and once when it reflects off this extra layer, which lets them take maximum advantage of the available light. Humans do not have the tapetum layer, though cats and dogs do, allowing them to see much better in the dark—and sometimes giving them crazy eyes in photos taken with a flash!

In addition to mammals, owls are around during the night. They hunt rodents, so we often see them in areas where we are working. Owls have unique feathers and a wing structure that allow them to fly silently. I don’t often think of birds making a lot of noise with their wings, but it is very startling when an owl passes close by and there was nothing to warn you it was coming. This stealth tactic helps them hunt unsuspecting prey!

A tarantula hawk carries away its latest catch: a tarantula!

A tarantula hawk carries away its latest catch: a tarantula!

There are also plenty of creepy crawlies out at night. So many scorpions! We quickly discovered that scorpion burrows look a whole lot like pocket mouse burrows. Scorpions fluoresce under a UV light (black light), which we carry around with us to help identify tagged mammals. It’s amazing how much more visible they are when they are glowing bright green! Another fun fact about scorpions is the mothers give live birth to the young (called scorplings!), which then ride around on her back until their first molt, when they gain some protection from predators and can regulate their body moisture.

The most bizarre and (warning!) terrifying creatures I’ve encountered, though, are tarantula hawks. Tarantulas themselves are fairly common at certain times of year, and, while they can have a painful bite, are not particularly dangerous to humans and not at all a problem unless provoked, like being picked up or handled. Tarantula hawks are parasitic wasps that have glossy black bodies, bright orange wings, and a very menacing stinger. The female wasp captures and stings a tarantula, paralyzing but not killing it, and drags it back to her burrow. She lays an egg on the spider’s abdomen, and when the larva hatches, it burrows into the spider and feeds on it, leaving the vital organs so the spider stays alive. After a few weeks, the wasp larva pupates and eventually becomes an adult and emerges from the spider’s abdomen. I actually witnessed a tarantula hawk dragging a paralyzed tarantula toward her burrow!

These are things I imagine in the tropics, in exotic places far away. But this all goes on nightly, right here in southern California! After all these months in the field, I’m much more comfortable being outside at night, but I also appreciate nature for being both more fascinating and horrifying than ever before.

Rachel Chock is a graduate student and volunteer with San Diego Zoo Global’s Pacific pocket mouse project.


It’s (Almost) Black Tuesday for Bees

The damaging effects commercially managed bees experience from pesticides are also suffered by native bees.

The damaging effects commercially managed bees experience from pesticides are also suffered by native bees.

Yes, I mean the catastrophic crash of the stock market in 1929 and the economic Great Depression that followed. As I listened to today’s stock market gains and losses on PBS’s “Marketplace,” I was struck by how closely our society follows this information. We pay attention because it affects our lives directly. The situation with pollinator decline is no less critical yet is barely on the radar of most. Since we have not hit bottom yet, it seems like a problem for another day—and there is no index to tell us how close we are.

Still, the warning bells are ringing. Pollinators like bees, butterflies, beetles, and flies are in crisis worldwide, suffering from pesticide exposure, habitat loss, and disease. Pollinators make fertilization possible for many plants; without them, food as we know it would simply not exist: no fruits, veggies, peanut butter, or chocolate—and that’s just a start.

If this suddenly sounds like the same old story you hear about humans and nature, stay with me a little longer. It’s more than another wildlife-in-crisis story, and I can guarantee that it will affect you personally—and definitely financially—if we keep the current course.

So, in the spirit of “Marketplace,” let’s do the numbers!

Visit the San Diego Zoo’s Pollinator Garden.

30% of the food we eat results from insect pollination.
This includes everything from cucumbers to squash, coffee to basil, strawberries to cantaloupes, cashews, and everything in between. It doesn’t include the insect-pollinated foods like alfalfa and clover that we feed to our livestock (where we get milk, eggs, and meat), so the percentage is likely much higher.

There is a 59% decline in overwintering monarch butterflies in the Central Mexican butterfly preserves since 2012.
75% of the Earth’s flowering plants depend on insect pollination to set seed or produce fruit.
The value of insect-pollinated crops in the US is $27 billion.

US beekeepers experienced a 30% decline of managed honeybee colony winter losses in the 2012-2013 year.
This number is far greater than the acceptable range of losses and only represents winter loss, not total loss. There are only about 2.5 million commercial honeybee colonies in the US. For perspective, it takes 1.6 million colonies to pollinate the annual almond crop alone.

All insects are affected by contact with insecticides. In particular, a newer class of systemic insecticides called neonicotinoids has been shown to severely affect bee health. In agriculture, this type of insecticide is most often applied as a seed coating, and the insect nerve poison is subsequently expressed in every tissue as the plant grows; leaf, stem, pollen, and nectar.

As a result, though the insecticide is targeted at “pest” insects, there can be serious consequences for any insect that visits the plant for nectar or pollen. Some need only be present when the planting occurs, as some of the chemical seed coating is released in a crop “dust” in agricultural plantings. The effects of these pesticide exposures include immediate death by contact, but some are sub-lethal, meaning that the animal does not die right away but experiences disorientation, loss of navigational ability, paralysis, and even memory loss as the result of contact.

Though there are federal regulations governing the concentrations of these poisons in agriculture, there are none for home use. Many products containing this type of insecticide can be found in local home improvement stores for landscaping use. Consumers often do not follow the instructions for application, and the concentrations can be many times higher than federal regulations allow. This means more of the poison will find its way to bees and other insect pollinators through gardens and runoff from irrigation.

It is important to note that the majority of research on pesticide effects in pollinators has been conducted in honeybees, because they are managed commercially and are thus more accessible and measurable. Since their biology is very similar to that of native bees, it is safe to assume that the damaging effects they experience from pesticides (and other sources) are also suffered by native bees.

Habitat loss
As human populations grow, less space remains for native pollinators. Overgrown spaces with wildflowers, weeds, and nesting sites are disappearing, making way for manicured lawns that eliminate key nectar and pollen sources like dandelions and encourage pesticide use. Agricultural practices claim land that was once suitable pollinator habitat with a diversity of nectar and pollen sources and replace it with insecticide and herbicide-laden monocultures.

Genetically modified (GM) crops
Two types of GM crops are routinely used in agriculture. One is an insect-resistant type, where a bacterium that is lethal to certain insects is incorporated into the genome of the plant, and the target insect species are killed upon feeding on the plant.

The second is an herbicide-resistant variety and is definitely of concern for pollinators, especially butterflies and bees. In herbicide-resistant GM crops, the plants are engineered to be resistant to applications of certain herbicides. As a result, the crop can withstand repeated applications of herbicide, which in turn kills all the flowering weeds surrounding the planted area.

This is of particular concern for monarch butterflies, whose larval host plant is milkweed, which thrives in disturbed habitats and has historically been found adjacent to crops. Most people are familiar with the epic migration of the monarch butterfly to the oyamel fir forests of Central Mexico. This year, the count of overwintering monarchs in the protected reserves revealed a catastrophic drop—down an incredible 59 percent from that of 2012 and standing at an all-time historical low since the migration was discovered in the 1970s. Lack of available host plants due to GM-related herbicide application has been identified as a significant contributor to this staggering decline.

There are a great many parasites and pathogens that burden pollinators such as bees, and the ones causing the most damage are introduced species. Native bumblebees suffer from a nonnative fungal disease, while honeybees struggle with introduced ectoparasites such as Varroa mites and fungal infestations from Nosema spores.

A combination of all these and probably other factors has created the phenomenon Colony Collapse Disorder, which is decimating honeybee colonies in the US. The precise cause is unknown, because the bees simply disappear, thus taking the evidence with them. But one thing is clear—life is hard for commercial honeybees these days.

Pollinator gard_1

A native bee house for mason and leafcutter bees in the Pollinator Garden provides holes to make nests.

At the San Diego Zoo, we are committed to helping pollinators recover:

Providing a safe haven
We have a pollinator “way station” at the Pollinator Garden, located at the entrance to Elephant Odyssey. This space is dedicated to helping sustain pollinators by providing a steady supply of pesticide-free nectar and host plants, as well as suitable living spaces for native bees. We have a large section of milkweed available for monarch butterflies to lay eggs on from spring through fall, helping to boost the West Coast population.

Educating our guests
Our Education Department is working with Zoo Corps kids to help raise native milkweed for monarch butterflies in our Pollinator Garden. Staff have also incorporated the garden as a teaching tool for various curricula.

Live and let live
Where possible on Zoo grounds, we allow honeybee swarms to move on in their own time and only actively remove established hives when either human or collection animal health is clearly at risk.
National Pollinator Week awareness
The Entomology Department participates every year in National Pollinator Week, with the help of many departments. During the entire week, the insect keepers are giving daily presentations on bees and other pollinators at the honeybee display in the Insect House at 11:30 a.m. and 2:30 pm.

A steady wave of small choices can help turn the tide. Here are a few ways you can help:

Buy organic
If you don’t currently buy any organic foods or clothing, think about picking even one item the next time you visit the store. For one, you could potentially lower the demand for crops produced using pesticides and reduce the overall application (over one MILLION pounds yearly) of these chemicals in the US. This alone will help pollinators.

Secondly, even if you don’t care about whether or not you eat GM crops, buying crops that are genetically modified supports the practice of widespread herbicide application in agriculture and the decimation of pollinator habitat that results. Organic items cannot intentionally include GM crops; those labeled “No GMO” have been positively determined not to contain them. One item in your basket is a small step in the right direction for pollinators.

Build your own way station
Plant some milkweed! Create a habitat in your yard, garden, or flowerbox that invites pollinators. Some great planting information can be found at, along with more details on the status of pollinators and insect conservation in general.

Avoid pesticide use at home
If you really, truly must use pesticides, read the manufacturer’s instructions on recommended concentration, and only use it at or below that level.

Let part of your lawn go wild for pollinators
Long, overgrown grasses create a perfect habitat for nesting and overwintering native bees, and flowering weeds are a staple nectar and pollen source for bees and butterflies alike. Keep in mind that most native bees are solitary and do not sting readily. They are good, safe neighbors—especially if you have a garden.

Tell your friends
Most people have no idea that the sustainability of food as we know it is so tightly linked with the health of pollinators. Share what you know!

This week, June 17 through 23, is National Pollinator Week. It is the perfect time to visit the Zoo’s Pollinator Garden and spend some time watching monarch butterflies laying eggs, and bees and hummingbirds finding a nectar or pollen meal in a beautiful flower.

But it is an even better time to act. If we can all make one small change in our habits this week, we could make a big difference for pollinators. To bring it back to our financial analogy, it has been said that if more people knew the current status of pollinator decline, they would be more concerned with that than with the ups and downs of the NASDAQ or S&P 500.

So now you know the stakes—and you are definitely a stakeholder. Will you invest in the solution?

Paige Howorth is an animal care manager at the San Diego Zoo. Read her previous post, The Queen Will Not Be Denied!


News about Zhen Zhen


Zhen Zhen relaxes after her 3rd birthday festivities in 2010.

Back in February, we reported with excitement that panda Zhen Zhen had bred for the first time and was the first female at the Bi Feng Xia center in China to do so in 2013 (see post Panda Zhen Zhen). For newer panda fans, Zhen Zhen is Bai Yun and Gao Gao’s youngest daughter and moved to China in September 2010. Well, it is with some sadness that we share the latest news on Zhen Zhen: On May 6, Zhen Zhen gave birth to a single cub; however, the cub died soon after birth.

Of course, we know that Zhen Zhen, who will be six years old this August, will have many more opportunities to breed and have cubs in the future, and there is no reason to doubt that she will be successful down the road. An early May birth is very unusual for pandas, with most of the births being recorded between July and September, after a variable period of diapause and a 50-day period of gestation.

Megan Owen is a conservation program manager for the San Diego Zoo Institute for Conservation Research. Read her previous post, Our Pandas in China.


Choose Your Favorite Butterfly GIF

Butterfly Jungle is in full swing at the San Diego Zoo Safari Park. You have until April 7 to bask in the fluttery glory, but in the meantime, check out these gifs of butterflies in the exhibit and let us know which one is your favorite. You can tell us in the comments below or tweet it to us at Enjoy!

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5. 5


Counting Mosquitoes

Summer interns Kathleen Connolly, left, and Christina Mangan pose with some of their finds.

Since October 2011, we have been monitoring disease vectors in the Safari Park Biodiversity Preserve (aka The Back 900). Here, the valuable coastal sage scrub habitat has been undergoing cactus restoration as well as monitoring of one of its important inhabitants, the cactus wren (see post Cactus Wrens Rise from the Ashes). Our goals are to monitor the presence and activity of mosquitoes and midges, two important disease vectors, and test them for West Nile virus and blood parasites, including plasmodium, the cause of avian malaria, in and around this reserve. From this data, we will be able to look at the occurrence of these disease agents in insects within the cactus wren habitat and which mosquito or midge species act as likely vectors.

Another interesting aspect of this study is analyzing what hosts these insects have been feeding on by evaluating their blood meals. Only females feed on blood; the male mosquitoes and midges feed on nectar. So for this study we are only concerned with the female insects. DNA is extracted from the blood meal, and a barcoding PCR is performed. The PCR product sequences are then compared to published sequences in the Barcode of Life database, which contains DNA sequence information for a large number of animals. Finding a match between the DNA sequence extracted from the blood meal and a known DNA sequence will enable us to determine which animals these insects have been feeding on. Mosquitoes and midges within the Safari Park have been found to feed upon various local creatures, including mallards, desert cottontail rabbits, mule deer, humans, and an occasional collection animal.

So, how do we convince the insects to be tested? Once every other week, our summer interns and I go out into the field, setting up UV traps and CO2 traps to attract and capture mosquitoes and midges. While out in the field, it can be quite an adventure, from the bumpy roads and rolling hills to the occasional visit from a resident mule deer or a speeding roadrunner. It is often enjoyable to get out of the laboratory and into the field and observe virtually undisturbed habitat right in our own Park’s backyard.

The UV traps attract the mosquitoes by emitting a UV light of about 350 to 400 nanometers; this acts as a visual stimuli for the mosquitoes and midges. The CO2 trap contains dry ice that emits CO2 to mimic the respiration of an animal and works as a chemical attractant for the insects. After anesthetizing the insects back at our Wildlife Diseases Laboratory, the students then have the arduous task of tediously counting and identifying the various species of mosquitoes and midges. Later, they extract the DNA and RNA from these insects and utilize it for the PCR testings.

This project has given our interns the opportunity to gain experience in the laboratory and in the field!

Jennifer Burchell is a research coordinator for the San Diego Zoo Institute for Conservation Research. Read her previous post, Invisible Clues.


Cockroach Improves Search-and-Rescue Robots

Hissing cockroach

Of all the species found in nature that are inspiring new engineering designs, one would not immediately think of the cockroach as a particularly inspiring animal. But time and time again, especially in the San Francisco Bay area, the cockroach has proven to be a wellspring of information for both biologists and engineers.

The methodology in which biological systems, processes, and elements are studied to draw analogies to be applied to human design challenges is called bioinspiration or biomimicry. The University of California, Berkeley, is leading this interdisciplinary method of design with the departments of integrative biology and engineering teaming up to develop a long list of bioinspired robots. The cockroach, a pest from most perspectives, is their star organism, inspiring generations of wall-climbing, terrain-tackling, and rapid-running robots.

The latest form to come out of their program is a swinging bot. If you’ve ever seen cockroaches scatter when a light is switched on, you know they have pretty impressive evasion tactics. Robert Full, Ron Fearing, and their students discovered an even trickier tactic than scattering: disappearing completely. Cockroaches, geckos, and now robots are capable of inverting from the top of a ledge to the bottom in the blink of an eye. To accomplish this disappearing act, the robot builds up speed, and then runs right off the end of the ledge. Before completely flying off the surface, it grabs the ledge with a hind leg and swings like a pendulum 180 degrees to attach itself to the underside of the same ledge. Cockroaches not only invert themselves on a ledge, but they continue to run on the underside, retaining 75 percent of their running energy.

DASH (Dynamic Autonomous Sprawled Hexapod), the cockroach-inspired robot, is paving the way toward more agile robots, improving search-and-rescue capabilities.


Dena Emmerson is a biomimicry research assistant at the San Diego Zoo. Read her previous post, Biomimicry, Biomaterials, Biometics.


Butterfly Watching

WOO HOO! Butterflies are back! Spring is in the air, plants are blooming, and I saw my first two monarchs in my courtyard last week!

As a zookeeper, I’ve worked with many species during my career. I’ve always been concerned about wildlife and habitats and how vitally important it is to conserve both, as each is dependent on the other for survival. But when I started working in the San Diego Zoo’s Entomology Department, it really hit me. Working with invertebrates up close opened my eyes to how important conservation, and education, is to our survival…and theirs.

The population of one of my favorite animals, the monarch butterfly, has seriously declined in the last few years. While they get food in the form of nectar from flowers, they perform the critical act of pollination and thus are important for the survival of plants and the potential production of fruits, nuts, and vegetables. The best effort to help this beautiful butterfly comes by planting native milkweed, their host plant, in our backyards and gardens. While it might seem like a small act, each of us really can make a difference.

Behind our Insect House in the Zoo’s Discovery Outpost is a small flower garden containing several plants for attracting butterflies. I had always wished I could do something similar in my own home, but I live in a very small condo with an even smaller garden space. What space I have is planted with a lot of succulents. But last year, I decided a small spot is better than none and planted six milkweed plants in the hope of attracting monarch butterflies. While I didn’t ask, or expect, help from my neighbors, I did let everyone know what I was doing and how important it was and asked all to help “monitor” the new plants.

Within a few days, we had a number of butterfly sightings. We saw females laying eggs on the plants and later on watched as the caterpillars started eating them. What joy at watching all the butterflies alighting on the plants, going from one plant to another! One of the unexpected perks was how excited my neighbors became when the monarchs started arriving. It was quite surprising! Interest really increased when we spotted the caterpillars. Then we started comparing notes on how many caterpillars we saw, and before we knew it we started having “happy hours” to compare notes on our new neighbors. What a blast! Our complex is small, and we all know each other, but having a new butterfly garden created a good reason to actually stop and visit each other. And that led to several happy hours and lots of laughter during the season. But not to be lost in all this excitement is the fact we started a new way station for our insect friends, and I hope this will help increase their numbers.

Regardless of how much space you have, you can help, too. It’s a great teaching tool for children about how important we all are and how important it is to save habitat for our animal friends. If you don’t have any children, you can always have a happy hour with your neighbors.

If you decide to plant a butterfly garden for monarchs, be sure to use native milkweed rather than tropical milkweed, which is lasting longer and longer in our warmer climate and is encouraging monarchs to “stay out too late.” They need to be on their way to an overwintering site by fall, and using a native species such as Asclepias fasicularis ensures the plant dies back after the first cold snap.

I will leave you with the story of the atala butterfly Eumaeus atala. On Key Biscayne in Florida, this endangered butterfly’s range was restricted to the northern end. There was suitable habitat in the southern region, but it was thought to be inaccessible to the butterfly due to development throughout the central portion. The host plant for this species, however, was a favored plant for backyard gardens; enough people planted it to create a bridge for the butterfly to reach the southern edge and new habitat, where it is now established. Thus, the beauty of citizen science and butterfly gardens!

Barbara Boon is a senior keeper at the San Diego Zoo.

Note: The Xerces Society for Invertebrate Conservation provides native seed, including native milkweed, to interested parties.


Garden Fest Insect House Tweet-up

The crew from last year's Festival of Flight tweet-up

UPDATE: The tweet-up is now full. Stay tuned for the next one!

Sure, we’re known for our animal collection, but did you know we’re also a world renowned botanical garden with over 700,000 rare and exotic plants? That’s why our next tweet-up (if you don’t know what a tweet-up is, educate yourself) at the Zoo will be on May 12 at 9:30 a.m. to celebrate our annual Garden Festival. However, unlike last year’s Garden Festival tweet-up, which was all about the plants, this year’s tweet-up is focusing on those cute little critters you might find in your garden at home: bugs!

Our very passionate insect keepers, Paige Howorth and Kelli Walker, will lead guests on a VIP tour of the Insect House in the Children’s Zoo, and they’ll bring out a few crazy bugs for guests to see up close. Unfortunately, our Insect House has a limited capacity, so we can only allow 30 tweeps to join us. If you want in (Zoo admission required), tweet these exact words:

I want to make friends w/bugs @ the #GardenFest tweet-up at the @sandiegozoo on May 12

The first 30 people who tweet the above will get a direct message from us with an invite to the tweet-up. If you’re not one of the first 30, you’ll be put on the waiting list. Please note, Zoo admission is required. If you want to bring guests, let us know and we’ll try to make accommodations depending on space available, but no promises. Our apologies for the limitations, but we’re excited to introduce 30 lucky tweeps to our creepy crawly friends. Now hurry and get tweeting!

Matt Steele is the social media planner for San Diego Zoo Global. Read his previous post, A Story of Love at the Zoo.


The Queen Will Not Be Denied

The queen's head and part of her thorax peek out of the fungus garden at her last "sighting" in 2007. The size difference between the queen and the worker ants is dramatic.

A keeper jokingly told me the other day why, early in his career, he chose to work with large mammals: “I like to actually be able to find and count all the animals in my care.” It made me laugh—who wouldn’t? But at that time I didn’t know that I would soon be counting—at long last—one of the most notorious and elusive animals in the San Diego Zoo’s insect collection and that it would inspire more anxiety than relief!

Tracking animals in the Zoo’s entomology collection affords little of the numerical certainty that helps to manage other animal groups. The reality is that in some of our invertebrate cultures, there are just going to be too many individuals to count, and certainly too many to count each day. This is not to say that we don’t keep track of them—in fact, we adhere to very strict permit conditions issued by the U.S. Department of Agriculture (USDA) in order to display and rear the regulated exotic invertebrates in our collection. When they recommend, as a containment measure, the presence of queen–excluding mesh on our leafcutter ant queen’s accommodations, that’s what we provide. Huh? Allow me to explain…

Paige prepares to moves the young colony and queen into the queen chamber in 2007.

All ant species have a reproductive division of labor, an overlap of at least two generations, and cooperative care of young. For our leafcutter ants (one of the most highly specialized ant species on Earth), it translates to one enormous queen ant, which accomplishes all the egg-laying in the colony, and hundreds of thousands of varied-age sterile worker ants that do everything else. (This is an immense oversimplification, but a treatment of leafcutter ant biology and behavior is another blog entirely!)

Leafcutters are quite famous for the long, green rivers of cut plant material that they produce while traveling back to their nests. They use the cuttings as a substrate to maintain and grow a fungus within their nests that they use for food. In the areas where they occur—particularly Central and South America—they are widely regarded as agricultural pests. So it is no surprise that our regulatory agencies would like to feel secure that though we may not always be able to see the queen ant, we always know where she is. Enter the queen excluder!

The queen ant in the tropical species that we hold, Atta cephalotes, is a big girl. In ant terms, she towers over the other colony members at a size of about one inch in length. But it is the widest, most rigid part of the queen’s body that the excluder must contain—the thorax. Our queen-excluding mesh is ¼-inch x ½-inch, big enough for the largest ants to access her chamber, but sufficient to keep Her Majesty in one spot.

And in one chamber she has remained for the five years she has been with us. We always feel confident that she is doing well based on the colony behavior and health of the fungus gardens (particularly the royal one), and that has to be enough, as we have not actually SEEN her for four years. Buried within the royal chamber, she is busy laying eggs (close to 30,000 per day), and participates in no other daily aspects of colony life. As long as she is producing continual reinforcements for the short-lived adult ants, the work of the colony carries on.

Here’s the containment area in the Insect House, showing the current housing of the two leafcutter ant colonies at the San Diego Zoo. Individual fungus gardens for each colony are maintained within the larger terraria.

Early in November, we noticed that the ants were reducing the amount of fungus in the queen chamber, little by little. Knowing that as the queen goes, so goes the colony (for leafcutter ants are not capable of producing a “backup” queen if their foundress dies), this was an unsettling turn of events. Each day we would check the garden and try to triangulate the height and shape of the fungal peaks (“Do you think it looks smaller today? I think it looks smaller.”), until we could no longer deny that something was changing. And that change seemed likely to include the relocation of the queen, since the ants had already started the demolition of her quarters.

The ants, of course, are quite oblivious to our needs, wants, and regulations. If they encounter an obstacle in nature, they do what it takes to surmount it. So here we were, faced with the unconquerable result of a decision rule (the obvious desire to move her), a very large queen, and a port of exit too small to safely accomplish the task (the excluder mesh). This made me very nervous, because I knew they would try to get the queen where they wanted her to be, but the outcome of that effort might be MOST unsatisfactory to ALL parties involved.

When I came in on Sunday, senior keeper Barb told me that the ants had been trying to move the queen out through the mesh, royal head first. Panic! There are anecdotal reports of other captive colonies, faced with this very circumstance, giving it a try and ending up with the head of the queen on the outside of the chamber and the rest of her body inside—effectively excluded, but with a huge price. Barb covered the entrance with a piece of plastic, and I headed for the toolbox in a hurry.

The young colony's fungus garden was only the size of a softball when it arrived at the San Diego Zoo.

As long as the excluder keeps the queen in a controlled area (one that could be examined if need be), we are well within the limits of our permit. Since the back area of our display colony houses several fungus chambers, including the queen’s, we decided to give her access to all of the other chambers in the off-exhibit area and move the excluder to the port that leads into the exhibit. In this way, the ants would have some freedom to choose where to house the queen, and all we would lose is the ability to know exactly in which of the 11 chambers she resides. Though that specific knowledge is a huge benefit for long-term management of the colony, I decided that we could live without it—after all; there is no long-term management for a colony with a headless queen.

In fits and starts, scraping angry, biting ants off of each hand as I went, I snipped away the steel excluder mesh at the chamber entrance, placed a fitting with a new excluder on the exit tubing, and removed the plastic barrier that Barb had placed earlier that morning. Within an hour or so, I got a call from lead keeper Kelli: “They are taking her out!” I ran back to the containment room, and we all watched a few supermajors (also known as soldiers) emerge with an entourage of medium-size workers carrying the queen! They made a direct line for a chamber on the bottom row, and after a few gut-wrenching (for us) tries to get her in there sideways, they figured it out, and she was in. And then she was GONE! During the transport, she remained still, but once she hit the ground in the chamber, she made her way quickly to the interior.

Seeing the queen of a leafcutter ant colony is a really unique, fascinating, and rare experience. It is a glimpse of a hidden world, and for insect lovers, akin to seeing a celebrity—only way better! But in managed care, it can be nerve-racking, because it could mean that the colony is rejecting something about their current living arrangement. So it appeared here, and we are happy to have been able to read the signs and facilitate the transition.

A few days later, there is harmony again, with all chambers receiving new leaf material and business resuming as usual. Leafcutter queens can live at least a decade, laying more than ten million eggs per year. Assuming there was no disease or failing in fertility that precipitated this event (or any that follow it), I hope she stays with us for the rest of her long life. And please understand that I say this in the most respectful way: I would gladly count lions, eagles, or stick insects all day long, but I hope I NEVER see Her Royal Majesty again!

Paige Howorth is an animal care manager at the San Diego Zoo. Read her previous post, Off with his Leeeeg!