Amphibian Conservation: Breeding Puerto Rican Crested Toads

April is an important time for the Detroit Zoological Society’s amphibian conservation programs. Three of the four animals we work with at the National Amphibian Conservation Center (NACC) that are a part of Species Survival Plans (SSP) are preparing to take part in precisely planned and scheduled breeding events. The outcome is the release of captive-born offspring into the wild to aid in the increase of their populations.

First up for the season is the Puerto Rican crested toad, Peltophryne lemur. The PRC toad, as we like to call them, has been part of a well-managed SSP since 1984. Habitat loss and competition from the invasive cane or marine toad (Rhinella marina) are believed to have been primary causes for the toad’s decline. Listed as critically endangered by the International Union of the Conservation of Nature (IUCN), collaborative efforts by the Associations of Zoos and Aquariums, U.S. Fish and Wildlife Service and the Puerto Rico Department of Natural and Environmental Resources have aided the recovery of this toad in the wild. More than 300,000 captive-bred tadpoles produced by 20 zoos have been released to the wild since 1982. Since the year 2000, the Detroit Zoological Society has produced more than 45,000 tadpoles for this program. In 2015, three clutches of eggs laid produced 22,571 tadpoles for release – the largest amount the Detroit Zoo had ever sent. Ongoing research and the creation and protection of pond habitats have also assisted in the recovery of this toad in its natural habitat.

You may be wondering what it takes to produce thousands of tadpoles from toads half the size of the palm of your hand. The breeding season starts with the assignment of four breeding pairs from the SSP. Each toad in captivity is identified and tracked using a studbook. Specialized software chooses pairs of toads that will produce the most genetically diverse offspring. By mid-March, we know who these eight toads are and we can begin preparing them for breeding.

Each toad must be easily identifiable – if you think all toads look alike you’ll be surprised to know that wart patterns and throat markings are very unique, although reading glasses are sometimes needed to make the proper ID. Toads are conditioned by slightly cooling and drying their environments out for a month-long period. A thermostat-controlled refrigeration unit keeps the toads cooled precisely at 66 degrees Fahrenheit. While the toads are “sleeping”, their primary zookeeper works diligently on preparing the breeding tanks where the pairs will breed and the eggs will develop. At this same time, veterinarians prepare a schedule of specialized breeding hormones that will further assist in ensuring that eggs are laid and fertilization happens at the right moment.

Upon their exit from cooling, they return to normal husbandry to warm up and eat for a few days. Breeding calls of male toads are played to encourage breeding behaviors. Males are first to go into the breeding tanks, followed hours later by the females. If all the preparation works, pairs of toads will be in amplexus – which happens when a male is positioned on top of a female and he squeezes her to encourage egg-laying – before we leave for the evening, followed by a morning of tanks full of eggs.

It takes two to three days for eggs to hatch and another couple of days for tadpoles to begin swimming around and actively eating. Tadpoles can be some of the hungriest creatures you will ever encounter. Keepers spend the next 10 days keeping them fully fed by offering them algae pellets, powdered diets and romaine lettuce sometimes three times a day. At the same time, all those foraging tadpoles create a lot of waste, so keepers spend the rest of their time keeping their water clean with frequent water changes.

During all of this, we keep a very important date in the backs of our minds – the last big event in our PRC toad breeding season. Any facility that breeds the PRC toad needs to ship them to Puerto Rico for release on the same date. The release of the tadpoles is timed with the season in which the tads would grow and develop the best in the wild. Tadpoles also need to be shipped at a certain age, before they get too big and begin to develop appendages.

Amphibian staff can spend well over 24 hours collectively counting and packing the tadpoles into Styrofoam-protected shipping boxes. Heavy-duty fish shipping bags are used, doubled up and filled with oxygen to keep tadpoles healthy and safe on their trip to Puerto Rico. Approximately 24 hours later, they will reach their new home in a pond located in a well-protected forest in Puerto Rico. As they develop and grow, they will add to the wild population and one day, hopefully, participate in creating many more thousands of tadpoles!

Rebecca Johnson is the associate curator of amphibians for the Detroit Zoological Society.

Notes from the Field: Saving the Wyoming Toad

For the past few summers, I have traveled to Laramie, Wyoming for the Wyoming Toad Species Survival Plan (SSP) meeting, which is an effort by the Association of Zoos & Aquariums (AZA) to cooperatively manage species populations within accredited zoos and aquariums.

First, I fly into the Denver International Airport, which is followed by a 140-mile road trip to Laramie. The trip is full of spectacular views of mountains, canyons, vast plains, huge clouds and pronghorn antelopes. Sometimes I drive the distance alone but this year I made the trip with three colleagues from different zoos. Each of us is a representative for our respective institution, all sharing the same goal of saving one of North Americas most endangered amphibians, the Wyoming toad.

After a stop for groceries and gas, we arrived at our destination for the next five days – a cabin in this remote area of Wyoming. We’re joined there by most of the other members of the SSP – this year, 10 people stayed at the cabin. Most of us have known each other for some time, so sleeping together in a room full of triple-layered bunk beds seems like a week at camp with old pals. But it’s far more than summer camp – we take part in discussions and updates on a number of important topics such as husbandry, health, management, fieldwork and research on this toad.

The next morning, representatives from the U.S. Fish and Wildlife Service (USFWS) arrived along with the AZA SSP coordinator to begin the meetings. Besides the zoos and aquariums involved, there are two USFWS facilities in Wyoming that hold, breed and release the toads. Many important topics are discussed with the last being choosing captive breeding pairs for 2016.

The Detroit Zoological Society (DZS) breeds these critically endangered Wyoming toads at the National Amphibian Conservation Center (NACC). Since 2001, the DZS has released more than 6,500 Wyoming toads into the wild as tadpoles, toadlets and adults. In 2007, the Detroit Zoo earned the highest honor on the AZA’s list of the Top 10 wildlife conservation success stories for that year.

The population of toads is maintained in special bio-secure off-exhibit rooms of the NACC. We have enough room to breed four pairings each year, and any tadpoles produced by the pairings are shipped out to Wyoming for release into protected wetlands in efforts to create self-sustaining populations.

Like each of the organizations present, I brought detailed notes on every adult toad in our resident population so that the best pairs could be chosen. Captive Wyoming toads need to be of ideal weight and health to take part in a month-long hibernation, followed by a June breeding event. Through the AZA, there is an identified “studbook keeper” who matches toads pairs that are least related and most likely to produce offspring that will be the most genetically fit.

On the second day in Laramie, we received training for the USFWS field surveys. Field surveys are done three times during the warmer months of the year around Mortenson Lake. This lake is the last known area the Wyoming toad lived before it was removed from the wild to protect the species from extinction. It is also the site of past and present releases of captive-produced tadpoles and toadlets. Present-day releases are more protected and provide several topics for research. Members of the SSP have been assisting with the mid-summer field surveys for more than five years and the training is just the beginning of a two- to three-day process to see how many Wyoming toads can be found around the lake.

The third and fourth day of my stay is spent almost entirely out in the field surveying for toads around the lake. Teams of two or three people carry backpacks full of equipment for data collection. Each plot must be surveyed in a specific allotted amount of time and by walking in an S-shaped pattern. Toads can be found hiding under grass, sitting on hard-packed sandy areas or swimming near the shore of the lake. If a toad is located, the timer is stopped, and data collection starts. Toads are photographed for identification, weighed, swabbed for disease testing and, if large enough, “microchipped”. It is particularly exciting when an older toad or a toad with an existing microchip is found. This usually means the toad has survived one or more very cold winters and may potentially breed in the lake.

Weeks later, back at the Detroit Zoo, I receive the compiled results of the survey. This year, we located and collected data on 224 toads – 129 toadlets that were captive-born and released into the lake this spring; 29 toads that were captive-born, released last year and survived the winter; 33 adult females and 33 adult males. Until next July, go toads!

– Rebecca Johnson is the associate curator of amphibians for the Detroit Zoological Society.

Notes From the Field: Amphibian Diversity in Peru

Hola mis amigas y amigos!

My Peruvian friends have been telling me that the last few months have been very dry, so I had no idea what to expect upon my arrival. I was very surprised to see that the Amazon River was at least 30 or more feet lower than when I was here in March, which could potentially have a huge impact on what amphibians we see. Areas where there would normally be ponds could be completely dry. As you can imagine, I couldn’t wait to get out into the rainforest and see what may be waiting for us.

Unfortunately, my suspicions were accurate and amphibians were much harder to find than usual. Since we monitor some of the same areas year after year, I had a pretty good hunch on where and what I might find in certain areas. When we have time, we always check other areas but our priority is to first survey our research sites. Among many other pieces of data we have been collecting, we are looking at diversity and abundance of species – basically, what types of frogs and toads and how many. This year seems to be the most obvious change, likely, due to the dryness. The humidity levels even felt different – normally my skin stays moist but this time I was using lotion.So far, the most interesting or peculiar sighting was a toad that had climbed a tree. The toad, common to South America, was at least four feet off the ground with no visible easy climbing point. I can hardly wait to see what else we may find!

Buenos noches!

– Marcy Sieggreen is the curator of amphibians for the Detroit Zoological Society and is doing fieldwork in Peru, studying amphibians in the lower elevations of the Amazon River to see how they are faring with increased human populations and impacts in their habitats.

Editor’s note: Marcy Sieggreen was the curator of amphibians for the Detroit Zoological Society from 2008 until her passing in 2016. The Detroit Zoological Society established the Sieggreen Amphibian Conservation Fund in Marcy’s memory to continue to advance the work she so passionately championed.