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San Diego Zoo Institute for Conservation Research

29

Yun Zi in China

Yun Zi arrives in the quarantine area.

Yun Zi arrives in the quarantine area. Photo credit: Wolong

Life is Good in Dujiangyan

We were all sad to see giant panda Yun Zi leave the San Diego Zoo and move to China, and honestly, we all miss him! However, we were not surprised to hear reports from keeper Jennifer Becerra (see Yun Zi Travels to China) that he traveled well, and it looked like the transition to his new life in China would be very smooth.

Yun Zi explores his new digs.

Yun Zi explores his new digs. Photo credit: Wolong

The changes a panda might experience when he or she moves to a new, far-away home include some changes in diet, new voices, different smells, and, for bears heading to China, the presence of a larger population of other pandas. Experiencing these novel stimuli for the first time may be both challenging and exciting for a young panda, and given Yun Zi’s generally spirited personality, I have no doubt that this was very exciting for him!

A good place to leave a scent mark?

A good place to leave a scent mark? Photo credit: Wolong

Yun Zi is now living at the Duijiangyan Base (part of the China Conservation and Research Centre for Giant Pandas), where there are 21 pandas, including 10 adults. Reports from our colleagues indicate that he is doing very well. Now 4½ years old, Yun Zi is approaching adulthood, but he is not yet of breeding age. That said, this breeding season could provide Yun Zi with some indirect experience, as he may hear the vocal communication of courting pandas at the facility and potentially catch the scent of a panda female in estrus. In a couple of years, he may be ready to experience panda courtship firsthand, but for now, he is simply enjoying spring in the Sichuan Province.

Megan Owen is an associate director with the San Diego Zoo Institute for Conservation Research. Read her previous post,
Panda News: The Good and the Bittersweet
.

38

What to Eat When There’s Nothing to Eat?

Bear ambassador Mi Ton Teiow finds relatively shallow snow, but no food, as the northern winter begins.

Bear ambassador Mi Ton Teiow finds relatively shallow snow, but no food, as the northern winter begins.

The answer? Nothing.

Most of us are familiar with the idea that some bears spend long periods of time in dens, inactive and not consuming significant amounts of food or water. Some bears in some locations survive eating nothing by doing almost nothing. They become inactive, which is sometimes called winter sleep or hibernation. Although you may be familiar with this aspect of bear ecology, have you thought about how incredible it is? These big mammals can go without eating or drinking for months, sometimes while birthing and nursing cubs, yet wake up without bedsores or weakened muscles! This is why the physiology of bears, including that of giant pandas and polar bears, has been a hot field of research.

The only way for a wild American black bear to survive for months without food in the northern U.S. is to save energy by hibernating in a safe, insulated den. The hole to the right of the tree trunk is the only obvious indication that there is an American black bear below the snow.

The only way for a wild American black bear to survive for months without food in the northern US is to save energy by hibernating in a safe, insulated den. The hole to the right of the tree trunk is the only obvious indication that there is an American black bear below the snow.

Although all female bears seclude themselves in dens to give birth to cubs, not all bears enter dens for long periods of time. There’s even variation within species in whether or not individual bears remain in dens or for how long. Researchers have found that in general, bears spend long periods in dens not to avoid cold temperatures, but to reduce their metabolic requirements when there is not enough food to survive environmental conditions. So, in the southern part of their range where their energy balance can remain positive, individual brown bears, Asiatic black bears, and American black bears may not den except to give birth. At last year’s meeting of the International Association for Bear Research and Management (see post, A Whimsical Bear Ambassador Arrives), Lorraine Scotson and Dave Garshelis reported that some sun bears might den for periods of time in the most northern parts of their range, meaning that non-reproductive denning may occur among at least half of the world’s bear species.

The holes melted in the snow are made by the black bear’s respiration.

The holes melted in the snow are made by the black bear’s respiration.

The giant panda is one bear species that has not been known to den in response to a relative lack of food, and perhaps it cannot do so. During the rare times when all the bamboo plants in an area have flowered and then died, the giant pandas have left the area in search of food; they have not entered dens. Perhaps this is because a bamboo die-off is unpredictable from the giant panda’s point of view, or perhaps this is because a giant panda eating bamboo cannot build up sufficient energy reserves to be able to wait out the lean time in a den, or maybe both factors play a role.

Adult polar bears also do not enter dens solely to avoid food shortages. Pregnant polar bears do spend prolonged periods of time in dens, but biologists think other adult polar bears don’t do so. However, polar bears in some populations regularly fast for extended periods when sea ice conditions don’t allow them to hunt. As for other bears, anything that causes a polar bear to expend more energy, whether inside or outside of a den, or to fast for a longer period of time, makes it less likely that the bear will survive. Climate change is doing just that by reducing the amount of sea ice available to polar bears: the bears expend more energy and go without eating for a longer period of time, creating a great challenge for the conservation of this species (see Polar Bears, Climate Change, and Mi Ton Teiow).

Hibernating bears often line their den with leaves, twigs, and grasses, insulating themselves from the cold ground and conserving additional energy.

Hibernating bears often line their den with leaves, twigs, and grasses, insulating themselves from the cold ground and conserving additional energy.

The Bear Specialist Group’s Ambassador Mi Ton Teiow recently made a visit to the northern US, where he found plenty of snow but little food for bears. After a short stay in this area, which receives an average of 45 inches of snow per year, the ambassador returned (fled?) back to sunny San Diego, where the last measurable snow fell on the city in 1967. The odds are good that Ambassador Mi will not be snow camping in San Diego any time soon.

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research. Read his previous post, Courtship in Front of the Camera.

261

Xiao Liwu: Weaning Wrap-up

Xiao LiwuLate last week, we separated Xiao Liwu from his mother for the last time. He remained in the main viewing exhibits for a few days while Bai Yun was shifted out of the area so that they were not across a door from one another. We have found in the past that in the first few days post-weaning, the cub can be quite vocal, calling for mother as it wanders about. This can arouse a response from Bai Yun; therefore, we find it best to put some distance between them to allow our adult female to remain relaxed.

As anticipated, our littlest bear has shown some tendency toward wandering and vocalizing in the last few days. This is normal. As mentioned in a previous post, the cub is always the one most unhappy about the separation and would prefer to prolong his or her relationship with momma bear. The lure of a constant companion, playmate, and milk source is strong! Her absence from the cub’s life is something the youngster clearly responds to. However, past cubs seem to move on from their discontent within about a week or so, and we expect Xiao Liwu will follow suit.

For her part, Bai Yun does not seem to reciprocate the sentiment that “absence makes the heart grow fonder.” Keepers have reported that she is doing very well post-separation. The only restlessness observed with her are those typical of food anticipation, the same bouts observed when the cub was with her daily. Otherwise, Bai Yun is very focused on priority number one: her bamboo and other food. For our matriarch, it’s business as usual. Her job of cub rearing now done, she appears thoroughly content.

Xiao Liwu has been shifted off exhibit to the upper bedroom area where he is closer to his keepers. This is beneficial to the little bear, as the keepers are poised to fill some of the social void left by his mother’s absence. Already, they have had nice sessions with him during which they have been able to hand-feed him apple slices and offer him back scratches. The apple slices are a small victory because, as you may recall, he has been unwilling to eat anything but bamboo to this point. Having a food source over which the keepers can bond with the youngster will enable them to build a stronger relationship. These bonding sessions become an important foundation for future training and husbandry that requires cooperation and mutual trust between keepers and animal.

While Xiao Liwu will be off exhibit for some time to facilitate his keeper-bonding experience, there is a silver lining for some of our panda fans. Patriarch Gao Gao has been shifted back to the main viewing area, where he will remain for the next few months. When you observe the bears, you may notice that both Gao Gao and Bai Yun have small shaved patches now, as both underwent routine veterinary check-ups at the end of last week. With that out of the way, and weaning complete, our panda facility will now settle into a new routine that will be the status quo for the near term.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Weaning Xiao Liwu: Leafy Greens.

111

Weaning Xiao Liwu: Leafy Greens

Xiao Liwu is surrounded by leafy greens.

Xiao Liwu is surrounded by leafy greens.

After many days of short separations, giant pandas Bai Yun and Xiao Liwu were doing well. Both bears had a few hours each morning to be on their own, and both spent that time eating heartily. Reunions between them at the midday feed were non-events. Although occasional nursing bouts were observed, it did not appear that the frequency of nursing had been accelerated. Further, the duration of observed nursing bouts was very short, lasting only about two minutes. This suggested that either mother Bai Yun’s milk supply had begun to dwindle or that the nursing was more about comfort-seeking than calorie-seeking on the part of our youngster, Xiao Liwu.

Since no other comfort-seeking behaviors had been observed, we opted to move forward with our weaning protocol. Last week, we lengthened the time the two bears are separated. The two are no longer reunited at midday and instead are separate still as they are served lunch. Access to each other is now delayed until the end of the workday, when the last keeper is ready to head home.

Did you notice? Probably not, since the bears showed no overt response to this change. We have only one report of “Wu” knocking on the door that separated mother from son, and it was a brief event. They are both taking this change very much in stride. In fact, by all accounts, Wu seems to be handling this separation better than any of his siblings. He is a very relaxed bear.

I can’t say why it is that he seems so much better able to adapt to the weaning process than his siblings. Perhaps it is because of his penchant for bamboo. He still refuses to eat anything but his leafy greens, despite our keepers’ gallant attempts to offer him something—anything—that he might like as an alternate treat. We know that adult pandas have to spend a lot of time feeding on bamboo to meet their caloric needs. Perhaps Wu is not so concerned about weaning because he, too, is very focused on bamboo feeding. To get his calories, he isn’t relying on carrots and apples and Gao Gao bread and honey-soaked softened biscuits (keepers have been really trying to entice him!), so he has to take in as much bamboo as he can get his paws on, and there is little time to worry about his mother.

In fact, these weaning separations may be helping him to some degree. Our little panda actually gained some weight in the first nine days of our separation protocol. Perhaps having the bamboo all to himself is beneficial to him. It will take some time, and several more weigh-ins, to see if his weigh gain trajectory alters as a result of weaning separations.

In a short time, if both do well, we will be looking to complete the weaning process for Xiao Liwu. Though some of the details have yet to be worked out, be sure that our keeper staff stands ready to provide Wu with the added social support all of our past cubs have needed once he is independent of his mother. All of our previous cubs have incurred a short period of pining for their mother after weaning was complete (generally not reciprocated by Bai Yun, they’d be sad to learn), but perhaps our bamboo boy will pine the least of all. He’s very busy, after all, getting in those leafy greens.

Watch our pandas daily on Panda Cam.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Weaning Xiao Liwu: Conflict over Calories.

97

Weaning Xiao Liwu: Conflict over Calories

Xiao Liwu nibbles on a bamboo stalk.

Xiao Liwu nibbles on a bamboo stalk.

Over the last week or so, we have allowed our giant panda mother-cub pair access to more space to see what kind of behavioral pattern develops. We’ve watched Bai Yun and Xiao Liwu closely during this time, both with formalized behavioral observations and informal sessions by keepers and staff. What we have seen is rather typical for this stage in their lives together. Bai Yun is food-focused, moving around both exhibits in search of the choicest bamboo and other snacks. Xiao Liwu is also becoming increasingly food-focused, though interested only in bamboo. When he is finished eating, he follows his mother around, like a little shadow.

Interestingly, this cub is not ingesting much kibble or produce. This makes him rather unique among his siblings in that they were motivated to feed on these calorie-dense items. Xiao Liwu, on the other hand, is limiting all of his non-milk calories to bamboo, which makes it that much more important that he gets plenty of his leafy greens. Since he is nursing very infrequently, probably less than once each day, his bamboo intake is meeting most of his energetic needs.

This is where a conflict arises. Bai Yun is quite determined to meet her caloric needs as well, and though she ingests a lot of produce and kibble, she’s also keen to exploit the bamboo resources we provide. Right now, she has a little competition for the choicest bits, and we have witnessed several bouts of wrestling over bamboo between mother and cub as a result. She’ll even steal the cub’s bamboo and hold him at bay, squealing, while she munches on the remnants of what Wu was working on. Though we provide the two bears with plenty of food, sometimes Wu loses out to his mother with respect to the bamboo he wants. Although he can usually walk away and find something else to snack on, we wonder to what degree his ability to meet his caloric needs is inhibited by his mother.

When not feeding, Xiao Liwu moves about the exhibits in fairly close proximity to his mother. Bai Yun, on the other hand, has not been observed following her son. This is a pattern we have observed with past panda cubs. If the little ones had their way, weaning separations would be delayed by months, or even years! Who wants to give up on the milk bar and the built-in playmate? But Bai Yun is less interested in fulfilling these roles as time goes by. Rejection of nursing bouts is something we have seen off and on for some time. And play bouts are not always welcome. For example, we recently witnessed a bout in which Wu bounded onto his mother with a sudden leap, resulting in Bai Yun biting down hard enough on him to elicit a loud yelp. This brought the play bout to a skidding halt, which may have been the result Bai Yun was going for. As this kind of interaction becomes more common, it reinforces for us the importance of considering momma bear in the weaning equation.

The indicators suggest to us that we should move ahead with our weaning protocol. For this reason, you will notice that Bai Yun and Xiao Liwu will now have periods of separation, each one housed in one of the main exhibits for a few hours each day. The bears will be separated in the morning and given their own foods to chow down on. The cub will not have to worry about his mother stealing his breakfast, and Bai Yun won’t have to worry about play bouts interrupting her meal. We’ll bring them back together about lunchtime and repeat the process the following day. We will, as usual, be watching closely to see how the bears adapt. Stay tuned to this channel for further updates as the process unfolds.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Weaning Xiao Liwu.

75

Tracking Safari Park Elephants

Swazi receive a GPS anklet to wear during Charlotte's study.

Swazi receive a GPS anklet to wear during Charlotte’s study.

The San Diego Zoo Institute for Conservation Research works closely with the elephants both at the Zoo and the Safari Park. We consider research an important part of advancing elephant care and welfare, as well as providing us with opportunities to apply what we can learn about elephants here to those in the wild. Our most current project looks at the effects of quality versus quantity of exhibit space on elephant behavior, walking rates, and stress-related hormones in an effort to improve the welfare of elephants in zoos. Elephants need a good amount of space to fulfill their physical and psychological needs. However, space may not be of any use to an elephant if it is predictable. An elephant may benefit more from a smaller, more dynamic space (quality) rather than a larger, less dynamic space (quantity).

The Safari Park’s African elephants have access to both the east and west yards via a hydraulic gate. This gate makes it easy to manipulate the space, or quantity, of the exhibit for this study. To manipulate the quality of the space, we present controlled food enrichment. Using five different manipulations of food enrichment and available space two times a week for three trial periods, we can assess the relationships between quality and quantity.

Each manipulation lasts 22 hours. I come in to do observations in two- and-a-half-hour shifts three times to assess the elephants’ activity patterns and behavioral diversity. (This is when you might see me on Elephant Cam!). Eight of the elephants are equipped with GPS tracking anklets. With the help of some innovative thinking, we have designed an anklet to house the GPS device as an alternative to the typical collar devices. The device records the coordinates of the elephant wearing it every five seconds. At the end of the 22 hours, the GPS data is downloaded and sorted, and walking rates along with distance can be calculated.

The Safari Park's elephants stroll through the morning's mud.

The Safari Park’s elephants stroll through the morning’s mud.

Lastly, in order to examine the stress levels of the elephants, we collect both fecal and saliva samples representative of the time period of interest. Using both techniques allows us not only to gain a more robust picture of the amount of stress hormones present but also gives our endocrinologist an opportunity to perfect and define the methodology of these hormones via saliva samples, a technique which has been understudied in elephants.

It takes a lot of people (and elephants!) to make a study successful. The Elephant Team plays a huge role in helping us design and achieve solid research that can help elephants in a variety of places and situations. So far for this project, we have already found some potentially interesting results in regard to our elephants’ walking rates. I am excited to carry forward with the trials of the project. Stay tuned for another blog update when the study is finished!

Charlotte Hacker is a research technician for the San Diego Zoo Institute for Conservation Research.

54

Weaning Xiao Liwu

Xiao Liwu enjoys a bamboo lunch in his expanded habitat.

Xiao Liwu enjoys a bamboo lunch in his expanded habitat.

When a giant panda cub is totally weaned from his mother in the wild places of China, one of two things likely happens: either his mother runs him off with aggressive behavior, as has been noted with some brown bears, or the mother and cub simply wander away from each other and begin separate lives. Many panda fans worry that that final weaning event is a sudden change for the bears, but in reality it is the culmination of a longer process that begins some months before, when the cub develops his bamboo-feeding dentition.

At about a year of age, the cub’s diet changes from one of 100 percent maternal milk to one incorporating his staple adult food, bamboo. He starts by feeding on small quantities of leaf, mastering the process of chewing and swallowing a solid food. Gradually, the cub ingests more and more bamboo and needs less caloric support from mother’s milk. By the time a final weaning separation occurs, he may only have been nursing once a day, or even skipping days between suckling bouts. The development of this nutritional independence takes time, and thus, weaning is not accomplished overnight.

Xiao Liwu turned 18 months old on January 29, 2014, and we have begun preparations for weaning him from his mother, Bai Yun. Many of you have noticed changes in the access given to our mother-cub unit, as they are now regularly seen exploring both the left- and right-hand exhibits. We have opened the door between these two usually separate spaces, allowing the pair to freely explore either side, moving independently or together as they see fit. This is an opportunity for both animals to become comfortable with the right-hand exhibit, which Bai Yun hasn’t seen in nearly two years; the cub has never experienced it before.

During this period we will be watching the pandas to see how they are utilizing this newly enlarged space. Do they spend more time in close proximity or separate? Does the cub follow his mother everywhere or explore alone? Does Bai Yun seem to move away from her cub when he approaches? The answers to these questions will tell us more about Bai Yun and Xiao Liwu’s readiness for weaning and will inform our decision-making as we move through this process. We aren’t in any rush here.

The weaning period is sometimes a difficult one for our blog readers and panda fans. There is often concern about the well-being of our bears during this time. Bear in mind, however, that a zoo setting is unlike a wild one in that there are barriers to animal dispersal. Simply put: our animals reside in enclosures, and they are not free to wander away from each other as they might in the wild. We have to help them adhere to their natural tendencies by opening up new spaces.

By making changes to the access our bears have to the spaces around them, and to each other, we are facilitating a natural process that is taking place in wild habitat even as we speak. In doing so, we are respecting the health and well-being of both mother and cub, guided by the best practices that biology, science, and husbandry allow.

I will update you periodically as to the status of our weaning process. In the meantime, I encourage all of our newest panda fans to read up on past weaning events with other panda cubs, in blogs such as:

Weaning Panda Cubs

Weaning Zhen Zhen: And So It Begins

A Big Step Forward

In these, you can find more details about what we know about this period in a panda’s life and the importance of remembering that this is not just about the cub but also the mother. You can get a flavor for how the process unfolds and how past cubs have responded to our weaning protocols. After eight years of blog-writing, our panda archives contain a wealth of information that you can access to learn about this and any other panda-specific topic you might be curious about.

One final note: To make room for our mother-cub pair and changing needs, we have moved Gao Gao to our off-exhibit area. You may see less of him on Panda Cam, but he is still here, happily munching away on bamboo and getting lots of attention from our staff. He won’t be back on exhibit again for about a month, as the weaning process will be focused in the main exhibit spaces.

Suzanne Hall is a senior research technician for the San Diego Zoo Institute for Conservation Research. Read her previous post, Yi Lu Ping (Have a Good Trip), Yun Zi.

26

Bear Ambassador Learns Importance of Plants

Ambassador Mi Ton Teiow explores some bamboo growing at the San Diego Zoo. This bamboo represents the incredible horticultural collection of San Diego Zoo Global and a key component of giant panda habitat.

Ambassador Mi Ton Teiow explores some bamboo growing at the San Diego Zoo. This bamboo represents the incredible horticultural collection of San Diego Zoo Global and a key component of giant panda habitat.

We’ve mentioned in previous Bear Blog posts that some of the major threats to different bear species are habitat loss, or habitat degradation, or habitat fragmentation. As you can tell, for bear conservation it’s important to consider the amount and quality of bear habitat. For food, bears (except for polar bears) rely on plants. Thus, people concerned about bear conservation often become concerned about the conservation of the plant communities on which the bears depend. Although San Diego Zoo Global is involved in conservation of animals, it also does a lot of work with plants.

Recently I talked to botanists and horticulturists at the San Diego Zoo, and our whimsical Bear Ambassador, Mi Ton Teiow, was able to visit plants from bear habitats around the world. You might know that our horticultural staff grow most of the bamboo eaten by the giant pandas or the eucalyptus eaten by the koalas, but that’s just the beginning of what they do! I knew that certain parts of the Zoo contained plants related to some I’d seen in Andean bear habitat in the cloud forest of southeast Peru, but our horticulturists pointed out close relatives of plants that are important to Andean bears in the dry forest of northwest Peru, as well as plants from Australia, Hawaii, and Africa.

This flowering powder puff tree (Calliandra haematocephala) may catch your eye, but there’s more to the plant collection than what meets the eye.

This flowering powder puff tree (Calliandra haematocephala) may catch your eye, but there’s more to the plant collection than what meets the eye.

One reason they are able to grow such a diversity of plants at the Zoo is its variation in topography, which helps create a wide range of microclimates. I was surprised to learn that during winter, certain parts of the Zoo may receive frost at night! Of course, another reason the horticulture staff is able to grow such diverse plants is their research to understand just what the different plants need to grow and reproduce. Sometimes this research requires them to conduct experiments such as those in the lab to determine the best conditions for propagating orchid seeds, or field trips like those to investigate wild fig trees.

San Diego Zoo Global grows plants for many different reasons, and sometimes because the plants themselves are of conservation concern, plant species can be endangered, and captive reproduction can be an effective tool for plants as well as animals. In addition to plant conservation efforts, horticulture staff grow plants for several reasons related to animal husbandry. As I mentioned earlier, some plants are fed to the animals, providing them with more natural sources of nutrition than they would get otherwise. Parts of other plants are given to animals as a form of enrichment, especially because of their scents. When an animal shreds a few branches it’s been given, the animal is performing a natural behavior in a renewable manner: the horticulture department will grow more!

This diversity of plant species and structure may resemble tropical bear habitat, but it’s actually part of the horticultural collection at the San Diego Zoo.

This diversity of plant species and structure may resemble tropical bear habitat, but it’s actually part of the horticultural collection at the San Diego Zoo.

Woody plants are also used as structures in the animal enclosures. Large limbs, logs, and sometimes stumps are placed so that animals have items to rub on, climb on, and sometimes sleep upon. You can probably see our bears interacting with their log “furniture” any time you visit the Zoo. And, any time you visit, you can pick up a free map and take yourself on a self-guided walking tour of the botanical collection surrounding you. If you’re able to visit the Zoo on the third Friday of a month, you can explore the plant collections further. On those Fridays, called Plant Day & Orchid Odyssey, you can take a free narrated botanical bus tour to learn more about the plant collections, and you can visit the orchid greenhouse, which is home to more than 3,000 orchid plants!

The next time you’re visiting the San Diego Zoo or Safari Park, or a zoo elsewhere, take a closer look at the plants; they’re a whole lot more than “just” landscaping; they’re food, furniture, and enrichment for the animals and plant ambassadors of the habitats on which their wild relatives depend.

Russ Van Horn is a scientist with the San Diego Zoo Institute for Conservation Research. Read his previous post, Bad News Bears.

2

DDT: Another Challenge for Condors

Rachel poses for a photo with Jake the sea lion at the Zoo's Wegeforth Bowl.

Rachel poses for a photo with Jake the sea lion at the Zoo’s Wegeforth Bowl.

Recently I had the opportunity to meet Jake, a star sea lion at the San Diego Zoo’s Wegeforth Bowl. When a sea lion like Jake leans in for kiss, what is the first thing you think of? Perhaps you wonder if he brushed his teeth or if there is a towel near by to wipe away the slobber? In any case, I bet you wouldn’t wonder, as I did, about how many environmental contaminants are present in his blubber. Sure, this may sound a bit grim and out of place, but I can assure you that my reasons for thinking this are part of a larger, intriguing story, in which I am completely immersed as I pursue my master’s degree through the University of Missouri. This story involves a pesticide that was banned 40 years ago, the Los Angeles County sewer system, and San Diego Zoo Global’s continued commitment to the recovery of the California condor.

No need to worry about Jake and other sea lions living in zoos, as there are relatively low levels of contaminants present in their tissues. Those living off of the California coast, however, conceal some of the highest detectable levels in any marine mammal species of DDE, the breakdown product of the pesticide DDT. How did levels of DDE come to be so high in sea lions? The answer is shockingly simple. From the 1940s to 1970s, the world’s largest manufacturer of DDT dumped hundreds of pounds of it down the drain daily, where it traveled through the Los Angeles sewer pipes offshore to the Palos Verdes shelf. This dumping occurred over 30 years ago; however, these chemicals are particularly resistant to degradation and still exist in shelf sediments. As tiny critters feed on the sediments, they accumulate DDE. From the smallest invertebrates to fish and larger animals, more and more DDE creeps its way up the food chain to a top predator, the sea lion.

As sea lions migrate up the coast, they take DDE with them. Some do not survive the annual journey and therefore become part of a larger food web that includes the California condor. With over 50 reintroduced condors circling the coastal cliffs, it is a real possibility that a beached sea lion would become a welcomed scavenging opportunity. While this find is an amazing feast for a condor, should we be concerned about the DDE it conceals?

Fuego hatched in 2008 at the Los Angeles Zoo and was selected to fill the nest of his soon-to-be foster parents Amigo and Cosmo of Big Sur, California. His foster parents taught him the skills needed to survive in the wild, including two wildfires!

Fuego hatched in 2008 at the Los Angeles Zoo and was selected to fill the nest of his soon-to-be foster parents Amigo and Cosmo of Big Sur, California. His foster parents taught him the skills needed to survive in the wild, including two wildfires!

To answer this question, we can imagine traveling the California coast on a birding tour in the mid-1900s. We would start along northern Channel Islands where the peregrine falcons are being reintroduced after a population crash. Next, at Santa Barbara Island, we could see a shrinking cormorant population that hasn’t produced a chick in years. Finally, on Santa Catalina Island we would look for a bald eagle, but without luck as they have disappeared. Each of these populations has one thing in common; birds were exposed to high levels of DDE, and they produced notably thin eggshells.

Reintroduced condors currently feed higher up the food chain than the above-mentioned coastal birds, and as you may have already guessed, are producing thin-shelled eggs. Our colleagues at Ventana Wildlife Society have found that eggshells of coastal birds are 34 percent thinner than those of inland birds. This has contributed to a 50 percent decrease in successful hatching of coastal chicks. This discovery has led managers to successfully take in eggs from the wild, incubate them in captivity, and allow the wild parents to incubate and fledge captive-laid eggs.

Multiple lines of evidence suggest a link between thin eggshells and DDE exposure in coastal condors, but how can we possibly be sure without exposing condors to harmful chemicals? DDE is an endocrine disrupting compound (EDC). It can disrupt normal endocrine (hormone) pathways and functions, like reproduction, by activating hormone receptors, producing an unnatural hormone-like signal, ultimately resulting in weak eggshells. Luckily for the condors, our lab is developing a reliable assay within a test tube to determine the sensitivity of condor receptors to DDE and other EDCs. Determining which EDCs most strongly interact with condor receptors gives us a clue as to which will be most disruptive to condor reproduction. Connecting this knowledge with EDC assessments of habitats will assist conservation managers in locating release sites for California condors. Our hope is to safely release these magnificent birds into a historic habitat that provides a rich, contaminant-free diet, allowing the hatching of many wild condors in the future.

Rachel Gerrard is a research technician for the San Diego Zoo Institute for Conservation Research.

3

Sifting through Poop

A tiger's poop can reveal a lot of information to researchers.

A tiger’s poop can reveal a lot of information to researchers.

I sift poop for a living. Well, that’s not quite true! I study hormones, those tiny chemical messengers that circulate in your body and control all sorts of amazing things, like when to grow or feel happy or sad, and, what I’m interested in, when to reproduce. Poop is just where I find the hormones. I could look for them in blood, just like your doctor might. But I work with animals, and they would rather you didn’t take their blood—anyone interested in getting close enough to a rhino or tiger to take a blood sample? Besides, blood only gives me a snapshot of their hormones at that moment when it’s collected. Hormones just don’t hang around in the blood very long. They do their job and are removed, often ending up in poop. In fact, hormones accumulate in the poop. When I measure the hormones found in poop, I get an average of what’s going on for that animal over the last 12 or more hours, not just a snapshot. And it’s easy to collect! So that’s the why, the how is bit more involved.

Every day the keeper collects a fresh sample in a small plastic cup, then freezes it, which stops bacteria and mold from growing, and prepares it for the next step. The sample is then freeze-dried, just like coffee. Freeze drying removes the water and makes the sample stable for long-term storage at room temperature. Next the sample is crushed and sifted. This removes the undigested material that interferes with the hormones during testing. A small amount of this dried and sifted material is weighed out and placed in a container with a liquid solvent. The hormones come off the poop and move into the solvent. This liquid is saved, and the rest is thrown away. I now have a liquid, or extract, containing the hormones I’m interested in.

Since hormones are too small to count directly, even with a microscope, a small portion of this extract is subjected to a special test called an immuno-assay. The assay involves combining the extract with a solution of specially labeled antibodies that attach to the hormone I’m testing. Once combined with these antibodies, the hormone that was too small to see or count becomes visible in a special detection machine. The detection machine counts the hormone-antibody couplets, and then it’s an easy calculation to determine the hormone level for each sample and each day. Graph the data, and you get a hormone profile revealing the reproductive status of each animal indicating if she is cycling, pregnant, or about to give birth. This information helps our animal care staff make informed decisions about how to care for and manage each animal.

Alan Fetter is a laboratory manager for the San Diego Zoo Institute for Conservation Research.