Archive for the ‘Amphibians’ Category

Houston, We Have Legs!

Posted by in Amphibians,Behind the Scenes,Conservation

In the last blog post, we discussed how egg and tadpole development can be broken down into various stages, called Gosner stages. The stages start with the fertilization of the egg (Gosner stage 1) and extend to Gosner stage 46, which is when the baby toad (also called an emergent) absorbs all of its tadpole tail.

emergent-with-tailLate last week, one of our tadpole tanks reached the developmental stage that we have been carefully monitoring for – Gosner 42! Gosner 42 is a really important time point in metamorphosis in which the tadpole starts to develop lungs. This means that the tadpole will soon give up its aquatic lifestyle for a new life on land.

We know that tadpoles are reaching this critical time point because they start to grow their front limbs. Did you know that both limbs don’t “sprout” at the same time? While we are monitoring for Gosner 42 stage tadpoles, it is not uncommon for us to see tadpoles swimming around with three legs!

Once one front leg is observable on a tadpole, we carefully collect it from the tank with a net and transfer it to a tank with shallow water and moss. This setup allows the tadpole access to both water and land as it finishes transitioning from gills to lungs.

As of today, we have 19 emergents from our first round of breeding several weeks ago. Several of these little guys still have some of their tail remaining, while others look just like tiny toads! Each emergent weighs less than a gram. It is hard to imagine that in a year they will weigh from 20 to 50 grams!

emergents

We are currently also caring for 47 tiny little toads that were head-started by our collaborators at Texas State University. These little toads are from egg strands collected around the Bastrop area and are the first wild toads to be brought into the facility since 2010. These toads will hopefully add “new genetics” to our captive colony, which is important so that we can maintain high genetic diversity in the eggs, larva, and toads that we release back into the wild in the coming years.

Stay tuned as we post more updates our newest additions!

Raising a Houston Toad

Posted by in Amphibians,Behind the Scenes,Conservation

So what does it take to raise a Houston toad from an egg? A lot of water quality testing, algae paste, and some good ol’ fashioned TLC.

The Houston toad facility at the Houston Zoo has four sets of tadpole racks that are designed to raise eggs to tadpoles. The racks themselves are made up of four aquariums with a circulating water system that runs through a set of filters. Water quality is of upmost importance, and the water is tested for the presence of nitrogen waste products every day.  Additionally, old food and debris are removed on a regular basis. The water in each rack is replaced as needed to keep it as clean as possible.

Unlike the carnivorous adults, Houston toad tadpoles are primarily vegetarians. In the wild they eat a variety of aquatic plant matter, as well as pine pollen that falls on the pond’s surface.  Here at the zoo the tadpoles are fed algae wafers and an algae paste that is smeared on pieces of PVC (which sinks to the bottom where the tadpoles like to feed). Older tadpoles are fed pieces of sweet potato and bok choy for additional vitamins and minerals.

As the tadpoles grow, they start to show distinct physical characteristics that can be used to determine what stage of metamorphosis they are in. The characteristics have been broken down into specific developmental time points called Gosner stages.  For example, when tadpoles start to develop a mouth they are in Gosner stage 23, Gosner stage 26 is when the hind limbs start to form, and Gosner 42 when the front limbs start to form.

We carefully monitor the tadpoles when they get close to Gosner 42. It is at this point that we collect the tadpoles from the tadpole tanks and transfer them into a separate tank with shallow water and moss. Not only are the tadpoles forming their forelimbs at this point, but they are also changing from using gills to lungs; therefore, it is very important that they have a surface that they can use to crawl up and out of the water!

We monitor the little toadlets until they completely absorb their tadpole tail. Did you know that the tail is the little toad’s first meal? Yummy! Once they absorb their tail they are carefully moved to another tank designed with shallow water and lots of moss that they can hop around on. In these tanks the toadlets are fed tiny insects called springtails.  As they grow they are offered larger food items, such as baby crickets (called pinheads), fruit flies, bean beetles, and eventually crickets.

Currently, we have 6 tanks of tadpoles that we are caring for that will eventually make toads that will become members of our captive assurance colony (which means they will be parents in the future!) Our oldest tadpoles are just now growing out their back legs (Gossner 28). We’ll keep you posted on their progress!

A Houston Toad Success Story!

Posted by in Amphibians,Conservation,Endangered Species

The past three weeks in the Houston toad facility have been a whirlwind of activity. Keepers, veterinary staff, and toads have all been racing the clock to get everything prepared to try to squeeze in a breeding event before the end of Houston toad’s normal breeding season. We are happy to announce that in all we were able to produce ~36,000 Houston toad eggs that have now been released in and around Bastrop State Park.

This marks the first release of eggs from the Houston toad facility. Generally, the survivorship of eggs in the wild is quite low, around 0.01%! However, our collaborators at Texas State University placed the egg strands inside wire cages, termed “predator excluder devices,” to protect the eggs from getting eaten by birds, fish, aquatic invertebrates, and even other amphibians! The eggs will develop and hatch inside the protective wall of these cages. Eventually, the resulting larvae and tadpoles will swim through the wire mesh; however, the cage will be left in the water so the tadpoles can continue to use it as a hiding place.

A graduate researcher from Texas State University is currently monitoring the developing eggs. She has recently observed very large Houston tadpoles hanging around one of the excluder devices from the first batch of eggs released, indicating that they are working and the tadpoles are surviving!

We kept a few of the eggs in the Houston Zoo’s toad facility to grow up to “toadhood” so they can be a part of our captive assurance colony.  These little toads are the offspring of some of our oldest and most “genetically precious” toads that we have here in the facility. Two of the females and three of the males that laid eggs last week are members of the very first group of toads that were brought into the toad program in 2007. We’re so happy that these toads are getting their offspring back into the wild!

Fingers crosses that the egg strands will produce lots of little toadlets that will be chorusing at the Bastrop ponds next year!

Home Sweet Home

Posted by in Amphibians,Conservation

Inspecting a toad before weighing

Last week we were happy to announce that the Leon county toads, a group of toads that had been housed at the Houston Zoo’s toad facility since 2010, had finally been given approval for release back into the wild. On the first leg of their journey, the toads were transported from the Houston Zoo to an outdoor facility managed by Texas State University.  The facility is in the county of Bastrop, one of the few counties in Texas where Houston toads still remain in the wild.

The facility consists of ~40 large tubs filled with sand, water, and vegetation.  When the Leon county toads arrived at the Texas State facility, groups of sixty toads were placed into the tubs. Here the toads were given an opportunity to acclimate to the outdoors before actually being released into the environment.

The “release” itself was staged over the course of several evenings. Graduate student Melissa Jones from Texas State was in charge of orchestrating each of the toad releases.  Before they could be released, Melissa had to weigh, measure, photograph, and give each toad an identifying mark. We were very fortunate to have the opportunity to assist Melissa in processing the toads one of these evenings.

Documenting toad information

First, we had to find the toads hidden in either the sand or in the water of the tubs, and then take their measurements. Melissa was very patient showing us how to perform these techniques in the field – it was far more difficult than taking these same measurements in the comfort of the quarantine building at the zoo! Collecting all of this data took several hours, but it was an amazing night.  The gentle winds blowing through the pine trees kept us company and were additionally treated to the singing of several other wild amphibians.

Processing toads

After processing, the toads were transferred to smaller bins and driven out to a pond near the holding facility. We stumbled through the dark with flashlights, carefully clutching our precious cargo as we made our way through the brush. Surprisingly, we did not disperse our charges at the pond’s edge; instead, under Melissa’s direction, we circled the pond and placed toads in small holes that we dug in the soil with our hands. We made holes under trees or other brush, placing two or three toads in each. By spreading out and hiding the toads in this way, we were ensuring that we were not making a “toad buffet” for hungry predators.

Slowly but surely, some of the little toads dug themselves out of their holes and made their way to the pond. Like any good “toad mom,” I got a little teary eyed watching these animals that I have taken care of for so long take their first few hops into  this strange new place, but I take comfort knowing that they have finally made it back where they belong. This is what wildlife conservation is all about. Thanks to everyone who has supported the Houston toad program and conservation programs everywhere!

Free at Last!

Posted by in Amphibians,Behind the Scenes,Endangered Species

We have fantastic news from the Houston toad program! On the morning of Friday, April 12th, we got the call from the US Fish and Wildlife Service that we had been crossing our fingers for – the “go for release” of our Leon county toads! Finally, three years after being collected from the wild as eggs, Red and her friends were finally going home.

This event is the first ever release of adult Houston toads from the Houston Zoo. Animals head-started in the facility are generally only kept a few weeks after metamorphosis and are thereby released as juveniles.  In the case of the Leon county toads, several unfortunate events prevented this particular group from being released after they were reared here at the facility.

The initial phone call from USFWS set off a flurry of events in the toad facility. It is no easy matter to pack up and ship out 600+ adult Houston toads!! With a rain event predicted mid-week, we were scrambling to get the toads out in enough time to give them a chance to acclimate to their new environment. In the world of the toad, rain means breeding, and getting more Houston toads to breed in the wild is one of our leading priorities!

With the help of our Houston toad interns and volunteers, we were able to pack up all of the Leon county toads Saturday afternoon. Dr. Lauren Howard of the Zoo’s veterinary team visually inspected every single toad being shipped out. Wow! I bet the doctors as the medical center can’t say that they’ve seen that many clients in a day!

After their health check-up, the toads were carefully loaded and transported to an outdoor facility outside of Bastrop State Park that is managed by our collaborators at Texas State University. We met up with graduate student Melissa Jones, to move the toads into several large, outdoor tubs where the toads would be allowed to acclimate to outdoor conditions for several days before being released. Melissa will be monitoring the released toads as part of her PhD dissertation work.

Loaded up and ready to go!

As soon as we placed the Leon county toads into these large holding tubs, which were deigned to be half water and half sandy shore (aka perfect toad habitat!) the male toads immediately started to call.  The sound was deafening in the quiet of the evening and honestly brought tears to my eyes. Though I know they were just “doing what toads do,” I would kind of like to think that they were saying “thank you…”

Goodbye and good luck!

 

Moving the Leon county toads to the Texas State facility was just the first stage of the release. To find out about the next step in their journey home, please check out the blog next week!

Houston Toads: What Are Those Bumps?!

Posted by in Amphibians,Conservation,Endangered Species

One of our Leon county toads, Red, paused chasing crickets for moment for a quick photo op. She is quite the photogenic toad!

Have you noticed in our Houston toad photos the large, lump-like structure behind the eyes? This structure is not a lump or a wart; it is in fact a specialized gland called the parotid gland. This gland is responsible for producing toxins that protect the toad against predators. Different toads produce different toxins of various “strengths.” In general, these toxins are not dangerous to humans; however, the cane toad (Bufo marinus) produces a toxin that can cause some skin irritation. Has your dog ever picked up a toad, then started foaming at the mouth? It is a reaction to these chemicals that the toad hopes will distract the unlucky pup so it will have a chance to get away!

The size and location of the parotoid gland can also be used to tell the difference between different species of toad. A good resource can be found here: Know Your Toads.

Did you know several compounds made by the skin of amphibians, specifically frogs, are currently the focus of a great deal of biomedical research? Several studies have found that many of these compounds have anti-microbial properties which have led some researchers to believe that they might be used to make the next generation of antibiotics. Additionally, a compound produced by the skin of the green-eyed tree frog (Litoria genimaculata) may be able to stop infection by the HIV virus, the virus that causes AIDS.

It is estimated that ~32% of all amphibian species are threatened with extinction.  Who knows what amazing medical breakthrough is waiting to be discovered on the back of a frog or toad? Now more than ever it is critical that we join together to help save these amazing creatures!

 

For more reading:

http://jvi.asm.org/content/79/18/11598.full.pdf+html

http://www.natureserve.org/library/amphibian_fact_sheet.pdf

Houston Toad Update

Posted by in Amphibians,Conservation

Last week we introduced everyone to Red, one of the many Houston toads that we are caring for here at the Houston Zoo. Red is a member of a group of toads that we refer to as the Leon county toads, which were collected and head-started from an egg strand that was found in Leon County, Texas (for an explanation of what head-starting is, please see the previous blog post).  Unfortunately, we were unable to release this group of toads the year they were collected and they have been with us at the zoo ever since. Now, 3 years after the eggs were originally found, these toads may finally have an opportunity to be released back into the wild!

One of the reasons it has taken so long to get Red and her siblings back out into the Texas landscape is because the Houston toad is considered a habitat specialist.  What is a habitat specialist? A habitat specialist requires a very specific environment in which to live. Houston toads require deep, sandy soil as well as an over story, which is a fancy term for “tree cover.” During the hot summer months, Houston toads actually bury themselves in the sand (called estivation) under the shade of trees and logs to escape the heat. The Houston toad also needs water in the form of lakes, ponds, or ditches in the early spring for reproduction.

Have you ever found a toad underneath an outdoor trashcan or within the coils of your garden hose? Most likely you have discovered the daytime hiding place for a Gulf Coast toad, the toad that most folks see in their yards.  The Gulf Coast toad is considered a habitat “generalist” in that it can make a home almost anywhere without the necessity of sand or other specific environmental features.  Because they are not picky about where they live, the Gulf Coast toad has adapted much better to living with humans, whereas the Houston toad has not.  Gulf Coast toads still require water for hydration and breeding, which is why you might catch one sitting in your dog’s water bowl on summer nights!

It took several years to locate land with the right environmental requirements where the Leon county toad “refugees” could be released. (But we’ve finally found a great place – yay!) Most of the land in Texas is privately owned, so are relying heavily on collaborations with local landowners to help us bring this species back. Thanks to everyone out there that is involved in the program!

Though Houston toads prefer sandy soil, we don’t actually keep them on sand in the facility. Want to know why not? We’ll tell you all about in our toad husbandry post next week!

 

Meet “Red” the Houston Toad!

Posted by in Amphibians,Conservation

This post written by Cassidy Johnson

The Houston toad staff would like to introduce everyone to Red, a 2-year old female Houston toad. Red is a little smaller than some of her female tank mates; however, what she lacks in size she makes up in spunk!

Red is a member of strand 25, which is a group of toads that were collected from Leon County, Texas. Why do we call groups of toads in our facility strands?  Unlike many species of frogs that lay their eggs in large clumps called egg masses, many toads lay their eggs in linear strings, or strands.  Each strand represents the offspring of a single mating event, so all of the toads in a strand can be considered brothers and sisters.

The Houston toad facility at the zoo raises toads from egg strands that are either laid in captivity or from partially collected wild egg strands. Why don’t we collect and raise the entire wild egg strand?  Just like other amphibian eggs, the Houston toad eggs are an important part of the ecosystem and it is important that we leave some behind. Additionally, in the off chance that something happens to the eggs that are taken to the facility, there will still be offspring produced from the eggs left behind.

Once they reach a certain size, the toads raised in the facility are released back where they were collected.  This process of raising toads from eggs in captivity is called head-starting, and continued release of animals back into the environment using this method will hopefully increase the wild population over time.

Back in 2010, several partial egg strands were collected from a site in Leon County; unfortunately, due to unforeseen circumstances, the toads head-started from these strands could not be released back at the collection site.  It has taken several years and lots of work by our partners at U.S. Fish and Wildlife, Texas Parks and Wildlife, and Texas State University, but a new, suitable release may have finally been located!

Why was finding a suitable location so difficult? Check out the blog again next week to find out!

Older Posts »

We're behind the scenes with Keeper Chris learning about turtles...read all about it! http://t.co/BMvDk5lMR7