How to Build a Pollinator Garden

Pollinators are one of Mother Nature’s greatest gardeners, yet many populations continue to decline at an alarming rate. While National Pollinator Week continues to raise awareness, conservation of our precious pollinators is a year-round project. One way you can be a hero for wildlife is by creating a pollinator-friendly habitat in your own yard or community, and invite hummingbirds, bees and butterflies to do what they do best.

Hummingbird | How to Build a Pollinator Garden

For starters, you’ll need a nectar source for your hummingbird guests. They get most of their nectar from tubular blossoms, the perfect shape to accommodate their long, slim beak and tongue. Hummers like bright plants that are open during daylight hours, when the birds are awake and hungry. Sage is an excellent option for these tiny pollinators, not to mention the added bonus of providing your herb pantry with some homegrown goodies.

Bee | How to Build a Pollinator Garden

It’s no secret that honeybee and native bee populations are in trouble. Entertain bees in your outdoor space by planting a diversity of vibrant flowers. It’s extremely important to select plants that do not contain neonicotinoids, a class of insecticides that may contribute to Colony Collapse Disorder. Nowadays, some stores label plants that have been treated with neonicotinoids, but many do not, so it’s best to consult with your local nursery before purchasing.

Bee | How to Build a Pollinator Garden

Including suitable nesting habitat in your landscape can help bolster the struggling populations of native bees. Many are solitary (so you don’t need to worry about a hive) and a good number of species are considered stingless, in case that is a concern. You can purchase ready-made nesting houses for mason and orchard bees online, or make your own.

Butterfly | How to Build a Pollinator Garden

For butterflies, a simple search on Google will help you discover which species are common in your area. Once you know which butterflies live in your region, it’s important to learn about their habitat needs. Certain species require specific host plants to serve as larval food for caterpillars. Choose a variety of colorful, native plants with upward-facing blossoms as they provide a landing pad for butterflies to stop and sip on sweet nectar.

Butterfly | How to Build a Pollinator Garden

Adding a water source for all of your pollinator guests is another great idea. If you’re going to use a bird bath to accomplish this, just be sure to add stones that peek above the surface so your tiny guests (bees) don’t drown.

Do you have any tips for creating a pollinator-friendly garden? Leave them in the comments.


Jenn Beening is the social media planner for San Diego Zoo Global. Read her previous post, 10 Cats You Don’t Want to Cuddle With.


DIY Succulent Centerpiece

If you haven’t stopped to smell (or observe) the flowers and plants at the San Diego Zoo and San Diego Zoo Safari Park, your senses are seriously missing out. Inspiration is in full bloom! And today, the brains behind the stunning botanical arrangements at the Safari Park are eager to share this spring-inspired DIY project.

#DIY Succulent Centerpiece

Step 1.) Start by filling the bottom of your pot with soil mixture. For best results, your mixture should be equal parts soil, pearlite, and sand.

#DIY Succulent Centerpiece

#DIY Succulent Centerpiece

Step 2.) Loosely arrange larger succulents in your pot and fill in soil to the same height as your plants.

#DIY Succulent Centerpiece

Step 3.) You can also include pre-cut succulents in your arrangement. In fact, recycling these fleshy plants is a great way to reuse them and fill any gaps in your bouquet. Just be sure to let cut plants rest in a dry place for three to five days before planting. Once they’ve dried for a few days, simply stick a hole into the soil and insert your cut stem.

#DIY Succulent Centerpiece

Step 4.) Have fun with your arrangement and try to incorporate different succulent species for a colorful display. If you’re visiting the Safari Park, stop by the Plant Trader where you can pick up drought-tolerant plants from our own collection.

#DIY Succulent Centerpiece

Do you have any horticulture-based requests for our team? Leave them in the comments and we’ll gladly offer tips from the experts.


Jenn Beening is the social media planner for San Diego Zoo Global. Read her previous post, 19 Fascinating Butterfly Facts.


An Insider’s Look at the Horticulture Department: Part 2

Plants for animal exhibits are chosen carefully for their association with the species—and durability!

Plants for animal exhibits are chosen carefully for their association with the species—and durability!

I wanted to work with the horticulture department because I love teaching the public about animals and am inspired by San Diego Zoo Global’s conservation work. In a nutshell (or seedpod), I wanted to discover how the flora and fauna departments work together at the Park.

To fulfill common conservation goals, the Safari Park’s animal care and horticulture departments work together to create beautiful, functional, and accurate exhibits. Plants in and around exhibits are often plants native to those animals’ exotic habitats. This exhibit planting improves the public perception of the Park—on a caravan safari, guests will actually feel as though they are in Africa. Endemic plantings also facilitate natural animal behaviors. For example: endemic plants in an aviary means birds can gather the same nesting materials at the Park that they might in the wild. However, this type of habitat-specific planting can be challenging. P.J. Rhodes, lead horticulturist, has to find African plants that are drought-resistant and cold-hardy to withstand California’s challenging climate—and resilient enough to tolerate the animals living among them.

Providing our weaver birds with the right plant material encourages natural nesting behavior.

Providing our weaver birds with the right plant material encourages natural nesting behavior.

For Gail Thurston, lead horticulturist, the most challenging part of her job revolves around integrating plants with both exotic animals in our collection and native California creatures. Most botanical gardens do not display animals, so plants in these settings have fewer threats. Gail says that “here at the Safari Park [we make a] constant effort to protect our plant material from not only the exhibit animals, but native animals as well: rabbits, squirrels, deer, vermin, and vectors…eat [our plants], dig them up, lay on them, or use them for nesting.” Although the local California mule deer are often the biggest problem, exhibit animals like giraffes can also create big—er, tall—challenges as well. The giraffes love eating the bark on the palm trees planted in the African field enclosures, so the horticulture department had to come up with a creative way to deter them. Many of the palm tree trunks are now enclosed in sturdy mesh to stop those pesky 16-inch giraffe tongues.

However, some of the plants at the Park are meant to be food. Thanks to the Browse Department, the Safari Park supplies the acacia, eucalyptus, bamboo, and fig foliage that feed many species at the Park and Zoo, including giraffes, koalas, giant pandas, and elephants, and many primates. The Safari Park annually produces 20 tons of acacia, 200,750 pieces of eucalyptus, 15 tons of bamboo, and 60 tons of fig foliage! Our sustainable forage supply exemplifies San Diego Zoo Global’s conservation-minded approach.

The next time you visit the Park, stop and see the rhinos—but also take the time to appreciate the gorgeous acacia or ficus tree those rhinos are lying under. Most importantly, talk to a horticulturist on grounds. This dedicated team works hard to make the Park beautiful for your enjoyment and would love nothing better than to spend a few minutes sharing their love of plants with you.

Elise Newman is a Caravan Safari guide at the San Diego Zoo Safari Park. Read her previous post, An Insider’s Look at the Horticulture Department: Part 1.


An Insider’s Look at the Horticulture Department: Part 1

Look among the animals at the Safari Park, and you'll discover an amazing botanical collection.

Look among the animals at the Safari Park, and you’ll discover an amazing botanical collection.

Not only is the San Diego Zoo Safari Park one of the top wildlife breeding and conservation facilities in the world, it is also a world-renowned botanical garden. The Safari Park’s horticulture department cares for 1,750,000 plant specimens spanning 1,800 acres. For the last few months, I have been working with the Park’s horticulture department on a job-share a few days each week. My goodness, these are hard-working people!

The horticulture department, comprised of 35 people, divides the 1,800-acre Safari Park into sections; one staff member’s section may span several acres. Specific teams are responsible for maintaining the plants and gardens in the center of the Park, around the off-exhibit breeding facilities, near the hospital, and in the large African and Asian field enclosures. Specialized arborists, irrigation, and pest control crews also help keep the Park in tip-top shape.

Working with the horticulture department, I’ve met an extremely friendly staff, full of welcoming, encouraging people who are passionate about plants. The horticulture team members came from very disparate backgrounds to work at the Park. Some have degrees in horticulture, irrigation, or arboriculture. Some had long, successful careers in completely unrelated fields and are horticulturists as a second career. For example, some of the horticulturists used to be zookeepers, work for construction crews, or work as gardeners in the private sector.

Saharan cypress

Among the Park’s plant collection is a North African cypress, one of the most drought-tolerant and frost-resistant conifers known—and a critically endangered species, having been exploited for centuries for its wood.

Let me set the record straight. If you’re picturing an arthritic 90-year old planting petunias in his front garden on a lazy Sunday, then you’re not seeing the Safari Park’s horticulture team. These horticulturists are fit, efficient women and men who face risks every day. In addition to working outdoors in 100+ degree Fahrenheit temperatures, they operate heavy machinery including chain saws, wood chippers, and dump trucks. They avoid rattlesnakes, thorns, bugs, sunburn, dehydration, and rainstorms. And they do it all with (amazingly) positive attitudes. Gail Thurston, the lead horticulturist of the Field section, says that “my favorite part is the daily creativity and the ability to have every day be different and fulfilling…every day we work in a beautiful garden.”

In addition to beautifying the Park, the horticulturists’ work augments San Diego Zoo Global’s mission. Plants are important in their own right, therefore San Diego Zoo Global is working to conserve not only endangered animals, but endangered plants as well. In fact, the Safari Park houses many endangered plants, including Catalina mahogany Cercocarpus traskiae native to Santa Catalina Island, Wollemi pine Wollemia nobilis indigenous to Australia, and Saharan cypress Cupressus dupreziana from Algeria. These plants are endangered in their native habitats, so growing them in botanical collections like the Safari Park helps increase their population numbers. Additionally, the horticulturists cooperate with San Diego Zoo Global’s Seed Bank and Institute for Conservation researchers to preserve endangered San Diego County habitat.

The horticulture team members are as dedicated to the Safari Park’s botanical conservation mission outside of work as they are in uniform. When they are not working at the Park, many of the horticulturists can be found at botanical conferences, re-planting coastal sage scrub in fire-damaged habitats in Southern California, or studying trees in the Amazon.

Stay tuned for the second part of this blog: how the Park’s flora helps the Park’s fauna!

Elise Newman is a Caravan Safari guide at the San Diego Zoo Safari Park. Read her previous post, Wild Romance.


Gorse Crisis: Making Way for Native Plants

Amanda and Amy remove some invasive gorse.

It goes without saying that wild bird populations are dependent upon good quality, natural habitat for foraging, nesting, and escaping from predators, to survive. The native forest birds of Hawaii face a multitude of threats, and the loss and degradation of habitat is one of the primary reasons for the decline of these unique species. Invasive plants and animals are taking over and destroying their forest home. For example, introduced pigs and deer browse on the plants and churn up the forest floor in search of food, killing native seedlings and providing an opening for faster-growing, invasive plants to gain a foothold in native environments. In many cases, in order to restore native plants, we must first remove the nonnative ones.

Gorse in bloom. Note the nasty thorns!

Gorse is one such invasive plant common in parts of Maui as well as the Big Island. The dense, prickly shrub, introduced to Hawaii in the 1800s, originated in western Europe, where it is still valued as a living fence for livestock. In addition to its aggressive tendencies, gorse grows much more quickly than most of Hawaii’s indigenous species and easily out-competes them for space and sunlight. Today, gorse is considered to be a serious weed, and all attempts to eradicate it have failed. The International Union for Conservation of Nature recognizes gorse as one of the top 100 worst invasive species in the world; so far, the best-recognized method for combating gorse is to plant faster-growing plants that are able to shade out sun-loving gorse.

At the Maui Bird Conservation Center, we have our own gorse crisis. Fellow intern Amy Kuhar and I are tackling our gorse invasion head on. Because the gorse defends itself with innumerable thorny spikes, we have started by taking down different sections of the weed in phases. We start by trimming back branches with loppers, then we use hand saws to sever each plant at the base. When possible, we also dig out the roots. The process is very time consuming, and we have worked many hours on the project. “Painstaking” would be the best adjective to describe the effort, because the gorse fights back, and after an afternoon of gorse eradication, we are left with innumerable itchy, tiny thorns embedded under the skin of our hands, arms, and legs!

A mamane sapling planted at the MBCC.

In addition to rescuing resident koa, ‘ohia, and mamane trees choked by gorse around the facility, we also began the process of replacing the invasive vegetation with native plants such as `a`ali`i and more mamane. In one area alone, we have planted more than two dozen new trees and are excited to see them growing over the newly cleared area! But the battle does not end there. One of gorse’s greatest weapons is its massive production of seeds, which can lay dormant in the soil for many years. As the older gorse is cleared, the seeds rapidly germinate, and within a few weeks there is a bed of new gorse seedlings. To stay on top of these, we must spray with herbicide to prevent another new invasion, allowing the native plants to flourish.

Hopefully, future interns will continue to clear gorse to make way for more native planting, all of which will someday create habitat for our wild, feathered friends such as the `amakihi. We hope the native plants will also eventually provide a source of perching, nesting material, berries, and seedpods for the birds in our care.

Amanda Maugans is an intern at the San Diego Zoo Maui Bird Conservation Center.


The Desert: Blooms and Hail

Grape-soda lupine

San Diego County is the most botanically diverse area in the U.S., with nearly 2,000 species, many of which are endemic (unique to a defined geographic area, so many are found only in San Diego County). There are not many places where you can experience the ocean, the snow, and the desert within a couple hours. The desert transition habitat is found down the east side of the Peninsular Ranges, and this is the site of our recent seed collection trip. The weather forecast looked ominous, but we were optimistic. To get to our site, we had to drive up and over the Cuyamaca Mountains and out into the lower elevations beyond.

Apricot mallow

When we finally reached our site, we saw a mix of cacti, shrubs, and huge granite boulders. It was freezing cold and very windy. At certain points the wind became so strong it was difficult to open the truck doors to get out and identify plants. Despite the rough conditions, it was a beautiful place to explore. We saw desert apricot Prunus fremontii, golden gooseberry Ribes quercetorum, and grape-soda lupine Lupinus excubitus in bloom.

As the day wore on, the weather only got worse. When we tried to collect a sample of apricot mallow Sphaeralcea ambigua, the rain turned to hail, and we decided to admit defeat for the day.

McCain Valley overlook

On the drive back up and over the Cuyamacas, the hail turned to snow! It was so much fun to watch everything turn white throughout the course of our drive. We followed a snowplow most of the way down the mountain; I never would have imagined experiencing something like that in Southern California! As we dropped in elevation, the snow slowly changed back into rain and everything turned green again. It was odd to realize that we had only been a half an hour away from the ocean.

San Diego is truly a remarkable place, and I couldn’t ask for a better area to study plant diversity.

Lauren Anderson is an intern at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. Read her previous post, Wake Up, Seeds! Germination Testing.


Conserving Threatened Palms

The threatened palm Brahea aculeata

The descriptor “tropical forests” usually conjures images of lush green forests with high canopies brimming with life—or at least for me it did. But as I look across the lands of the Sierra de Alamos-Rio Cuchujaqui Protected Area in Sonora, Mexico, I see large, columnar cacti peeking out from the fading green and pale brown of surrounding trees. Yet this, too, is considered a tropical forest—a tropical deciduous forest. Here the lush green foliage bursts forth with the summer monsoons and extends through mid-fall and hurricane season. As winter approaches, the trees drop their leaves, though not because of the cold temperatures, as with temperate forests, but due to the dry climate. By March, there is nary a leaf in sight, and the hillsides have taken on a red-brown-gray referred to locally as mojino. Many of the adaptations we associate with desert plants developed here to survive the harsh, dry season. The green that remains is found along the arroyos and in the stems of the tall cacti. That’s not to say there is no color, for during the dry season there is always something flowering. Blooming amapas Tabebuia impetiginosa add a splash of color to the fading greens and brown as we drive to the protected area.

A hawk perches on an amapas tree. Click on the photo to enlarge.

But the image of a forest brimming with life still fits, even if the first view doesn’t confirm it. Thousands of plant species live here, many are found only here. The Sierra’s tropical deciduous forest supports a rich array of fauna as well. With over 450 resident and migratory bird species, and many recognized as threatened or endangered, Birdlife International has designated the Sierra de Alamos as an Important Bird Area. The area also provides essential habitat and corridors for charismatic megafauna such as jaguars, ocelots, and margays. Many tropical amphibian and reptile species reach their northern range limits here, while desert species, such as the Gila monster, also extend into the region.

The protected area where we are working represents the northernmost stretch of tropical deciduous forest in the Americas, and possibly the most intact. Once extending from here in southern Sonora to Panama, and usually with only a width of around 30 miles, only 15 percent of the tropical deciduous forest in North America remains. And only about 1 percent of that is in protected areas. Though rather unusual for a protected area, the majority of lands in the Sierra de Alamos-Rio Cuchujaqui Protected Area remain in private hands; the reserve limits activities such as mining and land clearing, but cattle ranching still dominates the land, and overgrazing prevents a large risk. As part of the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research, I’m here as part of a research team focusing on a threatened palm, Brahea aculeata, and how various management practices (i.e. cattle grazing) affect the palm population.

Nature and Culture International (NCI), a nongovernmental organization partnering with San Diego Zoo Global in several locations in Latin America, represents an important resource for our project. They own land, have staff who serve as excellent field assistants and guides, and have strong relationships with ranchers in the area. Seeing the importance in conserving this little-known corner of the tropics, NCI has taken on the task of adding more stringent protection by purchasing the ranches along the main watershed. With just a few years’ break from cattle, it is easy to distinguish NCI lands from neighboring ranches; willows and other riparian vegetation really do flourish without the constant munch of cows. Hoping to widen its impact beyond the landholdings, NCI is working with us on some land-management issues in the area. We hope to base management practices in science and share them with the neighboring ranches. Building on this partnership, we hope to conserve this special part of Mexico, the tropical deciduous forest and the wonderful wildlife it contains.

Christa Horn is a senior research technician in the Applied Plant Ecology Division of the San Diego Zoo Institute for Conservation Research. Read her previous post, Observing Nature as a Child.

For more information on NCI and San Diego Zoo Global’s partnership…

For more information on the tropical deciduous forest of Sonora and NCI…


Seeds Make the World Go Round

There is a whole world of wonder inside a fig most people know little of, from fig wasps to seeds.

Every day I get blown away by certain characteristics of plants. There is no lack of drama or intrigue here. From succulents that look like rocks to flowers that smell like carrion to attract pollinators, the botanical world never seems to disappoint. It would be nice to think that plants do this for the pure pleasure of us humans. But this is, of course, not the case. Their reason is simple: survival. I thought it would be fun to look at some of the various ways plants distribute their seeds. Seed development and dispersal methods take high priority and have had a timeless trial-and-error process resulting in ingenious systems for prolonging the species, something us humans could learn a thing or two from!

We all have memories as kids blowing dandelions into the wind. What we were doing was spreading their seeds. Many primitive and early plants used the wind to spread pollen and seeds, and some still do. As more and more creatures roamed the Earth, plants exploited animals to help pollinate their flowers and distribute seeds. (Plant pollination is another fascinating topic that can be explored in a future blog; for now we will stick with the seeds.) With the help of the increasing numbers of fauna, the floral world really began to blossom.

As with most members of the bean family (fabaceae), Scotia brachypetala's seeds are hard and typical looking. However, many can be very colorful!

If you want something to go somewhere, wrap it in a delicious package. That is exactly what fruit does. The fruit attracts animals to take it off to another part of the forest with the seeds inside where they can be tossed aside to germinate. That is the tastiest method of seed dispersal, but many others exist. Take, for example, seeds that have barbs or hooks. They attach to a passing animal and get a free ride for a distance and fall off. Nuts are often collected by squirrels and buried, later to be forgotten about and so become trees. Winged seeds use propeller-like motion to glide away from their parent plant. And even some seed pods explode when touched by raindrops, sending their seeds a good distance away!

The bottom line is that plants need their seeds to be put in a good position to germinate and carry on the species. By these clever techniques, they achieve this. It is an area in the natural world often overlooked but should not be forgotten.

Seth Menser is a senior horticulturist at the San Diego Zoo. Read his previous post, Biomimicry: Nature Deals with Fire.


Biomimicry: Nature Deals with Fire

The seed-laden cones on banksias can survive the flames of a rushing wildfire and use them advantageously. Pictured is scarlet banksia, in Southwest Australia.

I woke up the other morning to the smell of smoke, an unfortunate sign of fall here in San Diego. Luckily, it was a small brush fire and contained before the dry, Santa Ana winds really picked up. It was a sober reminder that we live in a part of the world that has fires. Our fire season is a natural cycle and has been going on for millennia. We are not the only part of the world where fire is part of the ecosystem. Fires can occur all over the world, but in South Africa, Australia, and California, it is a routine. So perfectly, like most things in nature, native plants in these areas have developed ways to grow and even use fire to their advantage.

Fire is destructive, yet it does serve a purpose. It clears vegetation, produces nutrients, and opens up light to the forest floor. Many plant seeds in wildfire country, like conifers and proteas, are enclosed in a fire-proof, protected cone. These cones are designed for fire. A more specific example of this is the beautiful banksia of Southwest Australia. The seed-laden cones on banksias can survive the flames of a rushing wildfire and use them advantageously. The intense heat causes the valved capsules, which contain the seeds, to open up. When the fire passes and the cones cool off, the seeds fall to the ground, ready to become new plants. Because the fire has burned vegetation and let in sunlight, the altered forest floor is now the ideal place for the seeds to successfully germinate; a perfect and well-tested system in this seemingly harsh environment.

A common grasstree in Perth, Southwest Australia, is renewed by a brush fire.

So what can we take away from this? How can we use nature here as our teacher? Well, we already have at least one example of using fire to our advantage, and ironically, it protects us from fire. Sprinkler systems in buildings activate by burning a release mechanism. Once engaged, the water will put out the flames. But we should look beyond this.

There are two options for the millions of people who live in fire-prone areas: either move away or learn ways to deal with this natural occurrence. Since most of us are going to stay, perhaps we can look into paints that change their chemical structures when intense heat is applied and, in turn, form a fire-resistance barrier. This would be a savior for houses and structures. Even reforestation projects could be preemptively done, where native seeds could be set out ahead of time, in nonnative stands of plants, waiting for the inevitable wildfire.

Many good ideas could, once again, come to us by looking at how nature tackles adversity. Our mindset could change so that instead of waking up to the smell of smoke and being in fear, we could be inspired.

Seth Menser is a senior horticulturist at the San Diego Zoo. Read his previous post, Biomimicry: Hope for the Future.


Freezing and Thawing: Not so Easy

In reading over some of the blog posts here on the Zoo’s Web site, I could not help but notice that there are few, if any, about the laboratory work done at the San Diego Zoo’s Institute for Conservation Research. Lab work is a little tough to write about because there are no cute animals, no stories of climbing mountains or hiking through deserts. The work, however, is vital to our conservation efforts, and so I’ve decided to make an entry now and then to describe some of the things happening here in the Reproductive Physiology lab, including a new challenge we’re working on!

The most common task my fellow technician Nicole Ravida and I perform is the cryopreservation of male gametes – that is, we freeze the sperm of endangered species. The majority is collected from animals after they have died at the Zoo or Wild Animal Park; sometimes even other zoos send us testes (or ovaries) from their animals so we can add those gametes to our bioresource bank, the Frozen Zoo®. To date, we have banked over 14,000 vials of sperm from more than 850 individuals representing 260 species. Because sperm from different species differ in how well they endure the freeze and thaw process, we constantly are tweaking our methods. We do these experiments with sperm from model animals (i.e., domestic or non-threatened relatives of the species we need to save), and the sperm from endangered animals stay in the Frozen Zoo until a circumstance arises when they are needed.

Although the factors for preparing sperm for cryopreservation are many and their interactions are complex, the actual freezing of the sperm is not high tech. Years before I began working here, technicians devised a freeze method utilizing a Styrofoam box (pictured below) of certain dimensions with a certain level of liquid nitrogen inside. All you have to do is tape the vials of semen on top of a Styrofoam platform and float it on the liquid nitrogen. For a fast freeze rate, use a thin platform, for a slower rate, a thick platform. Close the lid on the box to allow vapor to surround the vials. (Nitrogen is liquid at an icy -320 degrees Fahrenheit or -195 degrees Celsius, and its vapor is nearly as frigid.) After 15 minutes, the sperm are frozen solid and the vials are ready to be plunged into the nitrogen and stored in a tank until they are needed. This is the basic freeze method we use for almost all mammalian sperm, or, at least, it was…

When you use Styrofoam boxes year after year, eventually they begin to wear out, get beat up and dented, and maybe even a little warped. So a couple years ago we noted that ours (all two still in stock) were rather worn looking. It was time to replace them. A company here in Southern California had made them for us in the past, and so we thought getting new ones would be simple. The company, however, was no longer in business. We then assigned one of our summer students with the task of finding another company. She found a local one, gave them the required dimensions, and when the boxes were made (we had to buy 18 at a time), she brought them back to the lab.

All should have been good and well, but it wasn’t. The Styrofoam wasn’t dense enough, so the liquid nitrogen was able to escape through the sides of the boxes, evaporating too quickly for us to maintain a set level for sperm freezing. But no problem, the company had a denser type and they made us 18 more boxes with the densest stuff they had. And yet the nitrogen still found its way out through the sides. Our student then tried sealing the outside of the box with paint. It didn’t help. She covered one completely in duct tape (surely all-purpose duct tape could save the day) but even this did not work. After a few more futile attempts to seal the boxes, she gave up. Nicole and I resorted to searching the Internet and calling companies to find a maker of dense Styrofoam, but we found no one who could help us. We resigned ourselves to the fact that they just don’t make Styrofoam like they used to, and we had 36 boxes to prove it!

In the end, we had to find something else to hold the liquid nitrogen, and we decided this something had to be easy to replace and easily duplicated by other labs; something anyone could buy. The standard ice bucket, present in almost every lab and available from many scientific companies, was a good candidate (pictured at top). It holds nitrogen well. However, ice bucket dimensions are not the same as that of our Styrofoam box, so we weren’t done yet. We had to figure out how much nitrogen was needed for freezing different types of sperm. Another summer student began this task by using a temperature probe to find a few levels that produced freeze rates similar to that of the Styrofoam box.

The next step was to do some test freezes to see how sperm fared when frozen in the ice bucket compared to the Styrofoam box. To make sure results are consistent, we have to do many freeze-thaw experiments—the same thing over and over, and, yes, this takes a long time. So far we have found that freezing in the ice bucket is actually better for the sperm of deer and antelope species than freezing in the box. A fantastic find! Our work is not done, however, and we still are in the process of figuring out how to best freeze the sperm of other mammals in the ice bucket. And what happened to those 36 not-so-dense styrofoam boxes? Don’t worry, they didn’t end up in a landfill. They went to Hawaii. Maybe they can’t hold liquid nitrogen, but they can keep things cold, and now they are serving the Hawaii Endangered Bird Conservation Program!

Dianne Van Dien is a research technician for the San Diego Zoo’s Institute for Conservation Research.