Chronicles of a Zookeeper

Ask A Biologist Podcast, Vol 127
Podcast Interview with
Bert Castro with a sloth at the Phonenix Zoo

Dr. Biology:


This is Ask A Biologist, a program about the living world, and I'm Dr Biology. For today's episode, we're getting out of the studio and into the wild. Well, maybe not the wilderness type of wild, but certainly a place where you can see thousands of animals. Yes, we're off to the zoo, and not just any zoo. We are visiting the Phoenix Zoo Now. We may not be able to see all 3,000 animals today, but we will get an introduction into the world of zoos why we have them, what they do for us, and the animals that live at the zoo. 


My guest today is Bert Castro, the President, and CEO of the Arizona Center for Nature Conservation, which is the group that operates the Phoenix Zoo. Bert's career started in 1985 when he was a volunteer and then, later that year, a keeper at the Tulsa Zoo. He has since then served in many roles at several zoos, including ones in Atlanta, San Antonio, Oklahoma, and now the Phoenix Zoo. For Ask a Biologist, we’re excited to be here because we often get questions from people wanting to work at a zoo. They love animals and they want to find out a way to work with them. Now, this episode is one of a three-part series we're doing about the zoo, and we plan to have other fun and interesting guests to follow. So, before anyone or any animal gets too excited, let's dive in and start exploring the world of zoos. Welcome, Bert, and thank you for sitting down to talk on Ask A Biologist. 



Thanks for having me. 

Dr. Biology:


Let's get started. We're at the zoo and it's huge. How big is the Phoenix Zoo compared to other zoos? A lot of people hear about the San Diego Zoo. 



You can measure a zoo on different levels. You can measure it by the size of its acreage. You can measure it about the size of its budget, but if you look across all AZA, which is the Association of Zoos and Aquariums, we're probably in the top 10 in terms of how large we are. We sit on 125 acres. The San Diego Zoo sits on 90 acres. The difference is the San Diego Zoo has a collection of about 6,000 animals and we have a collection of about 3,000 animals, so we're a little bit more spread out than the San Diego Zoo, but all in all, we're a very, very large, complex zoo. 

Dr. Biology:


Right, and that's one of the things I've always noted. There are areas in particular, I think, about the giraffes, the habitat for the giraffes. I mean, if I got to be in a zoo and I'm a giraffe, that looks like an amazing place. 



Yeah, it's a five-acre exhibit and I've been to Africa on many occasions and have been out on the savanna and when you walk up to our exhibit, they did a really good job of putting that exhibit together. It's very large, spacious. We have a variety of species in that exhibit and, you know, it allows the animals to kind of do their own thing and have an enjoyable time in that exhibit. 

Dr. Biology:


I agree. It's just a fantastic habitat. There is one that I've always wondered a little bit about, and that's the one for the bald eagle. Typically, you think of an aviary where it's big enough for the birds to fly, but this is not big enough for a bald eagle to fly, and I was always curious why that kind of a habitat. 



Yeah, we have a couple of bald eagles in that exhibit and you know, the interesting thing is they are not flighted birds. Those are actually rehab birds that can't fly. So even though the exhibit is probably 15 feet by about 30 feet in length, which seems small for bald eagles, it's actually quite appropriate because they cannot fly. 

Dr. Biology:


Oh, okay, that makes sense. I did not know that. 



We probably should put a sign up to let our guests know that. 

Dr. Biology:


Well, to be fair, maybe that sign is there and I missed reading it, but it's something for people to think about when they see some animals in habitats that they think maybe aren't big enough for them. It could be for this very reason. So, the next question I'd like to tackle is what should a good zoo be doing. 



Gosh, that's a really good question A good zoo there are good zoos in my opinion, and there are bad zoos. Let me start off by saying there are about 2,500 to 3,000 animal exhibitors in the United States, of which only about 9 or 10% are accredited AZA zoos. And you know, a great zoo has wonderful education programming. You know, at the Phoenix Zoo all our educational programs are aligned to Arizona State standards. So, we want kids to come out to the zoo and have a wonderful time, but we want the science that they're learning to be applicable to the classroom so that when they go back to the classroom they're learning something. And so that's an example of great education and an accredited zoo. 


Good zoos are conservation centers. 


They're places where we're working very, very hard on a daily basis to save animals in the wild. 


Many people don't know this and it's kind of interesting. We've been really good as zoos, in general, to talk about the fun things you can do at a zoo in terms of just a great, wholesome place to bring your family and have a great recreational outing. What I think we've done poorly over the years as a zoo community is not really talk about our mission like we should, and so a lot of people don't know that this last year, zoos and aquariums AZA zoos and aquariums contributed over $250 million to research and conservation around the world. So, every year over $200 million gets poured into conservation so the money that we make from people who come out and enjoy the animals. Many people won't ever have an opportunity to go to Africa to see giraffes in the wild, but they have an opportunity to come to the zoo and our hope is that through our education programs, through our conservation programs, people walk away from the zoo with a better appreciation for wildlife and a better appreciation for nature as a whole. 

Dr. Biology:


Right, and I think that makes a lot of sense. Some of the people that will have not the best view on zoos. They're thinking about the animals. I think the animals are actually. 



They feel like they're maybe in jail or they're you know, they're not, yeah biologists think at least from my perspective we think about the species and the survival of the species, whereas other groups think about the individuality of the animal and how is that animal being treated? You know, through our accreditation process we have very, very rigorous standards on how we maintain, exhibit, and take care of our animals, much different than, say, a roadside zoo. But I think one of the biggest problems is certain people clump all zoos together, so sometimes the good zoos get a bad rap from the bad zoos, and so I think it's important that we continue to get our message out. We continue to work with other organizations so that there's a better understanding about what we do as a zoo community, and we've been trying to do that, as the association has been working with a variety of groups out there to find common ground to work to help wildlife. I think that's very important and hopefully, through better understanding, everybody gets to understand everybody better. 

Dr. Biology:


What I find interesting, and one of the future guests, will be your person that's in charge of Behavioral training. 



Yeah, behavioral training. 

Dr. Biology:


And there was another term they used was enrichment. 



Oh, behavioral enrichment yeah. 

Dr. Biology:


And I just thought that was great because I have seen the rhino playing, I have seen Hindu, the Asian elephant playing. They actually have lots of toys and I think about my new grandson and I'm thinking, wow, these elephants get toys, just like my grandson, and they seem to really enjoy playing with them. 



Yeah, when I started in this business some 38 years ago, behavioral enrichment really wasn't a thing, and so it was really about, okay, how do we keep these animals alive, how do we keep them healthy? But in terms of their psychology, in terms of really keeping them in appropriate environments that are good for them, that's been a slow progress in zoos over the last 15 years or so, maybe 20 years. So, it's important to make sure that not only the animals have the appropriate space, but they also have things to do. You know, it's easy for animals, especially intelligent animals, to get bored, and so when I was a keeper, I spent my eight hours a day working, doing projects, cleaning. Now, our keepers today probably spend a third of their day doing routine and the majority of their day working with their animals to ensure that they're having the best possible life that they could possibly have. 

Dr. Biology:


Right, and you know, when we talk about that, one of the things that's going on right now for all animals, including humans. We're in the Phoenix area and the temperatures have been just unbelievably hot. For now over 20 days, over 110 degrees Fahrenheit. What are we doing at the zoo for the animals and again for all animals, I mean going to the zoo. If I was going to go to the zoo, that's going to be pretty tough as a human, but the animals too. What are we doing with this heat? 



Well, as everybody knows, we're in a desert, and so the animals that we keep at the Phoenix Zoo are animals that are found in warm climates. You won't see a polar bear at the Phoenix Zoo, so that's one thing we do. We have animals that are found in desert areas, in tropical areas. We also do a lot with shade, with misters waterers, and we give animals a choice. So, when it gets blisteringly hot, we give them a choice to either stay outside if they want or to go inside where there's air conditioning if they want. So, we give the animals the ability to make up their minds. 


Sometimes I'll walk out in the zoo. It'll be, you know, 105 degrees and you know the animals are outside because they prefer to be outside. A lot of our African animals love the heat, but when it gets really, really hot like it's been these last few weeks, we make sure that the animals have everything they need and the ability to go inside. One thing we did was close the zoo down earlier. We felt that that was important not only for our animals but for our guests. We were finding our keepers were struggling in the heat. Our guests were struggling. We weren't really seeing our animals struggle as much, but we wanted to make sure that we keep everybody safe while they're in the zoo. 

Dr. Biology:


Right, you start early hours right? 



We do. We open the gates at six in the morning for our members, seven o'clock in the morning for our regular guests, and we are now closing at 11. It used to be one o'clock, so through the month of July and August we'll close at 11. 

Dr. Biology:


Right Makes perfect sense. You talked about your keepers and actually, your career is really a fascinating one because you've done I wouldn't say you've done it all, but you've done a lot of different roles in the world of zoo management and zoos. So, let's talk a little bit about life when you're working at a zoo. What's it like? 



Well, it's all I know. It's all I've done in my entire career. Shortly after college, I started sending resumes all over the country and I would get these little thin letters that said thanks but no thanks. Congratulations on getting your degree. But you had no experience and so I ended up volunteering at my local zoo and there was a job that nobody liked to do and I said I'll do it and we had a mammal building there and down in the basement. At that time we had about 2,000 feeder rats and mice and my job was once a week I would come in on Saturdays and for eight hours clean the rat and mice cages. So, that was my start in Zeus. You know I did that for almost a year and I think a couple of positions opened up and they said well, you know what this guy? He's dependable, he shows up, he does the dirty work, he's a pretty good guy and they hired me as a zookeeper and I've been in Zeus ever since. So, I was a zookeeper for about eight years at the Tulsa Zoo. 


While I was there I went back to a small university in Wichita, Kansas, that offered an adult program in environmental studies with an emphasis in zoological administration. I did an internship at the Sedgwick County Zoo while I was still working at the Tulsa Zoo, and then from there, I went to New Orleans. I went to the Audubon Park Zoo as an assistant curator, spent a few years there, and from there on to Zoo Atlanta in Atlanta, Georgia, as a curator of birds and mammals, and then from there I took a general curator job at the San Antonio Zoo, and that's really where I learned how to not only take care of an entire animal collection, but I really learned a lot about the business side of zoos. As a biologist, I came up through the animal ranks and did know a whole lot about what it would take from a business standpoint to run a zoo, and so I learned quite a bit there. 


From there I went to Oklahoma City as executive director at the Oklahoma City Zoo, and that was a. It was a public non-profit. So, I had a board of nine individuals six of them came from the private sector, three of them were the mayor, the city council person, and city manager and so spent about seven years there. And then I came to the Phoenix Zoo. It's a non-profit zoo, a 501C3, which was much different than the previous zoo I was at. That zoo received a 1-8th penny sales tax. That generated quite a bit of money for the zoo. The Phoenix Zoo, being a non-profit zoo, receives no public funding for its operation, so it's run much differently, and I've been at the Phoenix Zoo for about 15 years now. 

Dr. Biology:


So, if someone wants to get started in the world of zoos and let's pick a student, let's pick one of our students that sends questions to us. It's usually a middle school or high school student that says I love animals and I've always wanted to work at the zoo. What's the best career path for them to go on? 



So, from a biologist's perspective right, because now zoos are so complex we've got accountants, we've got development people, we've got marketing people, pr people there's so many facets to running a zoo nowadays. So, we have a lot of people that are not biologists but are critically needed to help us with our mission. But if I'm talking to somebody who wants to be a biologist, I say, first of all, stay in school, get your degree. It's so competitive. You know, we were hiring for a position a few months ago and we had about 150 applicants for the position, many of them with master's degrees, applying for a front-line keeper position. So, it's extremely competitive, much more competitive than I think it was when I became a keeper. And so I would say stay in school and if there's any way, you can get experience. That's key because school is great and you learn a lot at school. But having that hands-on experience will just help you in the long run, especially when you're trying to get that job. 

Dr. Biology:


The zoos. To me, one of the amazing things is to spend time observing the animals. Why I find that interesting is I often wonder if the animals are also observing me, In particular some of them, as you say, some of the more intelligent animals. I really have always wondered if they're spending time looking at me, and the only reason I'm asking you this kind of a crazy question because obviously, you're not in the mind of animals is have you ever had that feeling when you're walking around the zoo, that they get to actually know you? 



They do. And as a keeper, you can be standing out there with 200 people and you'll walk in the midst of those people and that animal will pick you out and you know, it knows you. And it was quite interesting during COVID, you know, we had to close down for 161 days. Covid was tough for everyone. What we saw with a lot of our animals mostly our primates, a lot of our petting zoo animals, you know, our domestic goats was that they really missed seeing people, and so our keepers were actually spending more time with the animals. They'd go down to the exhibits and have lunch with the animals, because the animals at least, you know and this is anecdotal, this is not, you know, research by any stretch but we felt that the animals missed seeing people and we saw that, without being too anthropomorphic, that they were down a little bit, you know, and that having that connection was good for them, as well as with our keepers. So, I'm with you. I think animals do know who you are and they can certainly pick out individuals and they're very, very intelligent. 

Dr. Biology:


I actually was fortunate earlier before you and I got to take some time out to talk. I met Indu, the Asian elephant, and she gave me a rock with her trunk. She picked it up and handed it to me. The caretaker was there, by the way, I wasn't breaking any rules and it was interesting because she told me that's a present. 



That is a present, and she doesn't do that often Wow. You must have impressed her in some way. 

Dr. Biology:


I guess, did impress me, and I'm pleased to know that that was something special, because that felt special to me. Alright, so if it wasn't so hot, we could be wandering around the zoo and doing more talking rather than just being isolated in one place. But we're just like the animals. We have to regulate and, by the way, thermal regulation is the term we use so that you can be cool when it's hot and warm when it's cold. Animals have to do the same thing. We have a podcast about thermal regulation. So, along with animals, do you have a favorite animal, or maybe a couple favorite animals? 



I do. I love elephants. I was an elephant keeper for many years and everything they say about elephants about them being so intelligent and smart is exactly true. They're just amazing animals and just incredible to work with. I also have an affinity for jaguars. 


We have been working on a long-term project in Costa Rica. Dr. Jan Skipper, who's an associate professor here at ASU and was also our director of conservation, has been doing a lot of work there On a jaguar corridor. There's in southern Costa Rica there's an international park called La Amistad International Park, and then down by the Osa Peninsula about 30 miles away, there's another smaller park and there's a very vibrant population of jaguars in the very large park, and a stagnant, so to speak, a very bottlenecked population in the Osa Peninsula, and so we have been working with their government, farmers, landowners to build a wildlife corridor, to allow the jaguars and other wildlife to utilize a corridor so that jaguars can move back and forth because the land is so fragmented, the animals can't move from one park to the other, and so we've been working on that project for quite some time and I've been down in Costa Rica and had an opportunity to work with Dr. Skipper and it's just such a cool project and I've learned a lot about jaguars, so very cool animal. 

Dr. Biology:


Right yeah, animal corridors. It's a really good topic because a lot of times we don't think about it as humans. We build these freeways, we build walls, we do all sorts of things not thinking about the animals that might use that as their normal passageway. And while humans can figure out how to get around obstacles, animals don't. And that's problematic unless you're a bird, and then you probably have half a chance of flying over those, but that's correct. 


That's really an interesting one. It also comes to the discussion about conservation is one of the things that AZA. They contribute to conservation. This also deals with threatened and endangered species. That's true, guys, and so this is another role that I put the good zoos into is the fact that it's not just to bring animals closer to humans so humans get the benefit. It's also how do you ensure the survival of a species through these conservation efforts. And if you go to even Wikipedia I think is one of the nice things about Wikipedia now if you go to it and you look on the right-hand column, you'll see that there is a ranking there that shows you what the status of that particular animal you might be looking into, and it'll tell you whether it's threatened or endangered or, in some cases, there are some that are listed that are extinct as far as we know. So, let's talk a little bit about how the zoos are working in this realm of conservation and dealing with threatened and endangered species. 



So, ex-situ (off-site) working in zoos, we work through SSP programs, which are species survival plan programs. So, if you can think of it as maybe sort of like a pedigree, we have management committees that will focus on one species. To give you an example, today something came across my desk we have six African porcupines and the SSP. Once a year they make the recommendations for breeding. The whole idea is really trying to keep as much genetic diversity in the captive population as possible, and so we were asked to hold no breeding this year from our animals. But you know, they know everything about every animal in the population, what its health records are, what its genetic background is, where it's from, and we basically follow those recommendations. 


So, if they were to say, well, gosh, this certain animal who's been at your zoo for five years needs to go to Omaha to be paired with another animal, We'd immediately start working on making that transfer, because we're trying to sustain these captive populations. On the flip side of that, in terms of in-situ conservation, the AZA has developed a program called SAFE, Saving Animals from Extinction, and we have been I've been part of raising quite a bit of money for this program and it's really a way that we, as zoos and aquariums and individuals can work together to help save some of these species out in the wild. And so we've really kind of compiled our resources, have done a tremendous amount of fundraising, and then working with those researchers out in the wild and trying to support their efforts, their conservation efforts in the wild. 

Dr. Biology:


So, when I go to the zoo and I pay my entry fee or I'm even better I get my annual membership. Part of that money is going to these programs, that's correct. Yeah, that's great. It is great, that is really good. Well, Bert, before I let my scientists get out of here, I always ask three questions. I might modify the third one because we kind of covered it, but the first one is when did you first know you wanted to be a biologist and then when did you become very interested in working in a zoo? 



So, my story starts when I was really young. My family immigrated from Havana, Cuba, and so we came to the United States. I was born there. We came when I was two years old and when I was about six my mother started taking me to the zoo. It was a free place to go to and it was a fun place for me to go. And I can remember at around age seven I had two of my dear friends who I went to school with. They had birthdays around the same time and we had a birthday party at the Tulsa Zoo. As part of that birthday party, we were able to go and meet Gundah the elephant at that zoo, and my mother tells me that when she came to pick me up she just said I just wouldn't stop saying that, Mom, I want to be a zookeeper. 


I didn't know what a biologist was. All I knew was I had this amazing experience with this giant animal that was so smart and I told her I wanted to be a zookeeper. Well, 17 years later, I became that animal zookeeper and that has been my love ever since. That's all I've ever done. Zoos are part of who I am and I've learned a lot. You know you go into zookeeping for the love of animals, and then you start learning about all the complex issues around animals and those issues are big issues and how do you work with other people to help these animals. And so I'm still learning. I've been doing this for 38 years. I'm still learning every day on how we can conserve and give these animals a better life in the wild. 

Dr. Biology:


Right, what was the name of the elephant? Her name was Gundah Gundah. 



She just passed away, about a year ago. 

Dr. Biology:


Oh OK. 



Yeah, she was, I think, 70 in her 70s, so it's pretty amazing yeah. 

Dr. Biology:


Right. Well, that's another thing that I've noticed that we do these virtual tours on biomes, and often there are animals part of that, these virtual tours, these VR tours that we go into and I'm always doing the research on the animals that we happen to have captured in these VR tours, and when they show life spans, it's in captivity versus in the wild. I have yet to find one that doesn't live a lot longer in captivity than it does in the wild, that's for sure. 



I think you've got really good health care in zoos. You have no predators, so that probably has something to do with it. Yeah. 

Dr. Biology:


All right, so this is something you've done your whole life. I can tell you were basically imprinted by that elephant, which is really, really pretty cool, but I'm going to take it all away, for this question. So, your life in zoos is gone? Oh gosh, I know that's horrible. It's just a thought experiment here. We're not going to really take it away. Obviously. My question is what would you be or what would you do if you didn't have this? 



career. The one thing in the back of my mind that I thought I would like and I was intrigued by but don't know a whole lot about, was wastewater management and I thought, gosh, how do you take all this really dirty water and get it to a point where people can drink it? But I thought about it for about a day or two and then get back to zoos. 

Dr. Biology:


And today this is a really important topic. 



It really is. 

Dr. Biology:


Water is going to be key for many people around the world. Some will have too much and, like in the desert, we don't have enough right? 


The last question is typically what advice would you have for someone who wanted to start working in the zoos and pretty much covered that earlier on? So, I was going to ask you if there was something that you thought your young zookeepers forget to do or learn before they come, what would it be? What would be the thing that you would say will serve them well in their career that they may not be doing because they just don't think about it. They've done the usual stuff and there's something they're just not thinking about. 



You know, the thing I had to learn as a zookeeper was to be detailed, and what I mean by that is that when you're working with wild animals, it's important to be detailed in terms of how you take care of them, in terms of how you clean for them, in terms of safety, lock safety. You have to really be attuned to those animals and be attuned to what you're doing on a daily basis, because a lot of what keepers do is very redundant. I think the animals like that redundancy, they like routine, they're familiar with it, even though, you know, from a visitor's perspective, a lot of visitors come to the zoo and they say, oh gosh, that zebra looks so tame and it's a wild animal. And so it's important, as a zookeeper, to know that you have to be very detailed in what you're doing for your safety, for the public safety and for the animal safety. 

Dr. Biology:


Right, okay, for the young zookeepers out there that might have their pets at home, you could start your own project on that by creating your own log sheet to make sure when you feed them, how often you feed them. 



Clean that litter box. Clean that litter box. Yes, yes. 

Dr. Biology:


I will triple agree with that one there, one who has cats and loves them dearly. Well, on that note, Bert, thank you so much for visiting with me. On Ask A Biologist. 



Thank you so much. I really appreciate you having me here. 

Dr. Biology:


You have been listening to Ask A Biologist and my guest has been Bert Castro, the president and CEO of the Arizona Center for Nature Conservation, which is the group that runs the Phoenix Zoo. For those that live in the Phoenix area, I hope this podcast has you thinking about going to visit the zoo. Just remember, if it's in the summer, do it really early in the morning, and we'll also include a link to the zoo in the show notes so that you can get all the details about parking and other things that you might need to know for your visit. Keep in mind this is the first of a three-part series and if you have not subscribed to the Ask a Biologist podcast, you might want to do that right now so you don't miss the other really fun and interesting guests we're going to have on the show. 


The Ask a Biologist podcast is produced on the campus of Arizona State University and is recorded in the Grassroots Studio housed in the School of Life Sciences, which is an academic unit of the College of Liberal Arts and Sciences. And remember, even though our program is not broadcast live, you can still send us your questions about biology using our companion website. The address is, or you can just use your favorite search tool and enter the words Ask A Biologist. As always, I'm Dr Biology and I hope you're staying safe and healthy.

View Citation

You may need to edit author's name to meet the style formats, which are in most cases "Last name, First name."

Bibliographic details:

  • Article: Chronicles of a Zookeeper
  • Episode number: 127
  • Author(s): Dr. Biology
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Date published: July 28, 2023
  • Date accessed: June 12, 2024
  • Link:

APA Style

Dr. Biology. (2023, July 28). Chronicles of a Zookeeper (127) [Audio podcast Episode.] In Ask A Biologist Podcast. Arizona State University School of Life Sciences Ask A Biologist.

American Psychological Association. For more info, see

Chicago Manual of Style

Dr. Biology. "Chronicles of a Zookeeper." Produced by Arizona State University School of Life Sciences Ask A Biologist. Ask A Biologist Podcast. July 28, 2023. Podcast, MP3 audio.

MLA Style

"Chronicles of a Zookeeper." Ask A Biologist Podcast from Arizona State University School of Life Sciences Ask A Biologist, 28 July, 2023,

Modern Language Association, 7th Ed. For more info, see
An open book
How Does Speed Reading Work?

Be Part of
Ask A Biologist

By volunteering, or simply sending us feedback on the site. Scientists, teachers, writers, illustrators, and translators are all important to the program. If you are interested in helping with the website we have a Volunteers page to get the process started.

Donate icon  Contribute


Share to Google Classroom