Category: Amphibians

California Slender Salamanders

California slender salamander

A California slender salamander. Image taken on campus at San Francisco State University.

California slender salamanders are a great amphibian species to watch and learn from. They are pretty easy to find; they are relatively common and will almost always be found in the same area day after day. Most of the time, you can find these salamanders within 2 meters of the place you first spotted them and in one study, 59% of the time they were even spotted underneath the same piece of covering. That was certainly the case for several salamanders that I was watching between classes at SFSU, including this beautiful salamander shown above. You can find these guys under rotting logs or wood, sometimes under large flat rocks or even just under a thick pile of leaf litter-moist areas. From late spring through the summer, they might be harder to find, because they tend to go underground when things dry up. They are one of the few salamanders that are skinny enough to crawl into termite tunnels and earthworm burrows. They’ll also go underground sometimes to forage-they will eat spiders, mites, insects, earthworms and snails.

If you’re getting to know your local slender salamanders, keep in mind that they are most active at night. Also, if you’d like to handle them, here are a few suggestions:

1. Be gentle. Try putting your hand near them and encouraging them to walk on you rather than picking them up. If they are coiled up, then try scooping them from underneath rather than picking them up from above.

Califronia slender salamander

A California slender salamander climbs aboard my hand. Image taken on campus at SFSU.

This might seem obvious, but it’s especially important with salamanders because if they are adequately disturbed, this might happen:

California slender salamander

A California slender salamander with part of its tail missing. Image taken on campus at SFSU.

Salamanders will “drop” their tail if they are threatened, to help them get away. Their tail will regenerate, but it can take between 1 and 3 years. This salamander is in the process of regrowing its tail (This happened before I found it-it wasn’t me I swear!) and wasn’t doing too well when I last checked on it.

2. Don’t wear any perfume, lotions, bug repellents or sunscreen. Since amphibians have permeable skin, these things can harm them. Also, these particular salamanders don’t have lungs or gills, but breathe through their skin and the membranes in their mouth or throat, so you don’t want to gunk up their skin with lotion.

3. Moisten your hands, but be sure NOT to use regular tap water. If you go to a pet store and purchase a dechlorination liquid (very cheap bottle, used for fish tanks), put a few drops in a spray bottle of water and then spray your hands. This way the salamanders won’t dry out while you hold them. This is true for all amphibians you handle. They will be more comfortable if you do this. You can also rub your hands in whatever moist area you find them in, which will help a little as well.

If you follow these steps, then you can enjoy your salamander friends without stressing them too much or harming them. Also, keep in mind that many amphibians will secrete substances that some people are allergic or are sensitive to.

Speaking of which-one of the cool things I came across while learning about this salamander was an observation by a scientist who was working with these animals in lab conditions. He was trying to learn about anti-predator mechanisms for this species. Of course he came across the usual things-they drop their tails, or these amphibians will flip themselves to push themselves away from the threat and then sit still. But, when one salamander was exposed to a garter snake, it prevented being eaten by looping its tail around the snake’s head, forming a knot. Then the salamander released an adhesive skin secretion that glued the snake’s jaw shut for 48 hours. Salamander win!

And now, here’s one last shot of a beautiful California slender salamander:

California slender salamander

A California slender salamander. Image taken on campus at SFSU.


Hear Them Call: the Sirens

Lesser siren

Very little is known about this unique amphibian, the lesser siren. Image taken at the California Academy of Sciences.

This elegant little amphibian is the lesser siren, one of only 4 species of siren, all of which are found in North America. They all have the same body shape-long and slender, like an eel. They don’t have any rear limbs. The only limbs they have are the two tiny, weak arms in front, one of which is showing above.

These animals spend a lot of their life buried in mud or sand at the bottom of swamps or ponds. They can tolerate some pretty harsh conditions.  If their pond dries out, they can cover themselves in a mucus that hardens to make a thick papery cocoon with just their mouths sticking out, where they can wait for rain to restore their habitat. In the rainy season, at night, they can even travel short distances across land.

This group of amphibians will retain their larval characteristics for their entire lives. This means they will always have those big, fluffy gills (even though they also have small lungs), no eye lids and a lateral line, which allows them to feel pressure changes, and thus objects, in the water.  There have been some cool experiments to see if they can make a siren metamorphose. It seems that they have completely lost (or never had?) this capacity genetically. When researchers injected other tailed amphibians that retain their larval characteristics, such as the axolotls, with a hormone called thyroxine, they can induce metamorphosis, but not in sirens.

Scientists have wondered why certain amphibians will stay in their larval stage or retain larval characteristics. Why would this have evolved? One thought is that the aquatic habitats are surrounded by hostile land and therefore it’s beneficial to stay in the water. Another thought is that in some areas the water doesn’t have a lot of iodine, which is necessary to produce the hormone thyroxine needed for metamorphosis.  This is still an open area in research.

By the way, if you’re wondering what a true siren call is, it’s actually a distressed yelping sound. And honestly, I can’t imagine a siren call that would work better as an irresistible lure for me than the call of an animal in need.  Well…maybe a U2 song.


A rough-skinned newt pauses from his squirmy escape attempts. Image taken at Angelo Reserve, California.

The year was 1979, on a night filled with fun and games and of course tons and tons of alcohol. The excitement of the evening died down when all in company started noticing that something was wrong with one of their companions. He was a man, 29 years old, drunk off whiskey who was becoming numb and weak. He told them he thought he was going to die. Still, he refused to go to the hospital. He was left alone. In 15 minutes, his heart gave out.

Flashback, to right before the problems began. In their drunken madness, someone thought it would be funny if our victim ate a rough-skinned newt. He dared him to do it. Who can resist the temptation of a dare? He swallowed a newt and it was his fatal mistake.

He’s not the only one to succumb to this temptation. A 36 year old man, also inebriated, consumed 5 rough-skinned newts on a dare. He could just barely walk. He was dizzy and was vomiting. He had trouble coordinating his muscles. He went to the hospital and was treated and he survived. He was very fortunate.

It’s hard to believe that this inoffensive adorable little newt could cause these problems, but in fact, in terms of sheer potency, you are arguably looking at the deadliest animal in our country-worse than rattlesnakes or black widow spiders. This little newt is the only land animal to  contain tetrodotoxin, an incredibly potent neurotoxin, that is also found in the deadly puffer fishes (I recall a Simpson’s episode where Homer eats improperly cut puffer fish sushi and believes he only has 24 hours to live) and the blue-ringed octopus. The octopus gets its toxin from another organism living inside of it, however there is some evidence that this newt can produce its own toxin.


Full body view of a rough-skinned newt. Despite its neurotoxin, I can hold it in my hand as long as I avoid touching my face and wash my hands afterward. The toxin is only a problem when consumed. Image taken at Milagra Ridge in the San Francisco Bay Area.

Fortunately, this neurotoxin is only a problem if the newt is consumed. It doesn’t leach into its environment, which also means it doesn’t have any effect on our drinking water (yay!). For the most part, as long as we can avoid eating these animals, they’ll have few negative effects on us. (Apparently, this is easier said than done. I really just mentioned a couple of cases of grown men eating these guys, but there has also been instances of small children trying to stick these amphibians in their mouths and getting sick. For the record, my new state, Oregon, has the record for death by newt.)

The same can be said for other animals that might prey on the newt. If predators just choose a different meal, then they won’t be poisoned. So, how do they know to avoid this newt? Well, the newt gives them a warning. It’s called the unken reflex, where they arch their back in such a way that their head and their tail move toward each other. This exposes their bright belly.


The bright belly of a rough-skinned newt. Also, notice the vent on this animal is cone shaped, which indicates to us that this is a female. Image taken at Milagra Ridge in the San Francisco Bay Area.



The bright warning color of this newt covers its entire underside. Image taken at Milagra Ridge in the San Francisco Bay Area.

What’s interesting is that research has shown that its the position as well as the coloration that deters predators. The color alone is not as effective. The behavior is also important. I couldn’t tell you with certainty why.

So, predators are given a warning and they now know not to eat this newt. But every animal has to have a nemesis. In the case of the rough-skinned newt, that is the common garter snake. The newt and the garter snake seem to be co-evolving.  The garter snakes have developed a resistance to the newt toxin. In fact, after consuming a newt, the snakes become poisonous, storing the toxin in their liver for up to seven weeks. Three weeks after eating just one newt, the garter snake still has enough toxin in its liver to kill a bird predator.

The strength of a rough-skinned newt’s toxin varies in intensity geographically. Some populations have a stronger toxin than others. It seems that in some areas, the garter snakes tend to leave the newts alone, so it doesn’t benefit the newt to have a more potent toxin and the loss of energy from making a more potent toxin could be detrimental to its survival or reproduction. In other areas, the snakes prey heavily on newts, causing selection for higher toxicity. But there is still a limit to how toxic a newt can get and still benefit. If a newt has the right level of toxin, garter snakes are known to throw them up. Sometimes up to 85 minutes after a newt has been eaten, it will be vomited up ALIVE! However, if their poison is too strong, the snake can be paralyzed before the newt is regurgitated, selecting against  an even more potent newt.

Aside from the research done involving this newt’s toxin and co-evolution with garter snakes, other interesting studies have been conducted as well. While these newts have pretty stable populations right now and are surviving pretty well (considering the overall amphibian decline), there was some interesting finds involving them and exposure to UV radiation. It was hypothesized that UV, combined with many other factors (including the chytrid fungus), was partly behind the world wide amphibian decline. Research indicated that for these newts, exposure to UV radiation altered their anti-predator behavior and also enhanced the toxicity of PAHs, contaminant found in ponds and streams that often comes from runoff or industrial discharge. This study was conducted involving other amphibian species as well, and it turns out that some amphibians have more resistance to damage or problems from UV radiation than others.

Anyway, if you want to catch a glance of these amphibians, now’s a good time. As is gets colder and wetter, these animals start to look for places to overwinter on land, so you can see lots of them out and about. Just be sure to drive carefully, as many get squashed on roads at this time of year as well.

Last but not least, here is one last picture of my little friend, right before she got her wish and was released back into her pond.



A rough-skinned newt. Image taken at Milagra Ridge in the San Francisco Bay Area.


Amazon Milk Frog

An Amazon Milk Frog. Image taken at the Oakland Zoo.

This little froggy is an Amazon Milk Frog. No wait, it’s a Mission Golden-eyed Tree Frog. No wait, it’s a Blue Milk Frog. Oh no, I was wrong on all accounts. What this frog is, is a perfect example for why scientists use scientific names rather than common names. (Except often with birds, since the common names are relatively standardized.) So, this frog is Trachycephalus resinifictrix. But for now, we’ll call him an Amazon Milk Frog. Why milk frog? Well, it’s a fitting name for an animal that oozes out poisonous white milky stuff through its skin when it’s threatened.

There is dramatic variation in the life cycles of frogs and  often it is how the amphibians bring about the next generation that mesmerizes herpetologists. This particular frog is no exception; he has an interesting story to tell.

It all starts about an hour after sunset. Mr. male Amazon Milk Frog, who lives high up in the trees, begins to call. He is seeking a female and until one appears, he will keep calling and calling. He might end up making 4,000 calling notes in one night. But, once he attracts a female they will mate and she will deposit up to 4,000 eggs (average is less than 3,000 ) into his water-filled tree hole. She leaves in the morning, but dad is not done. The eggs will hatch in less than 24 hours (!) and there are a lot of hungry tadpoles to feed. At first, they’ll eat whatever detritus they can find, but this won’t last.

So, Mr. dad Amazon Milk Frog will begin to call for a female again. Why is he calling again? He already has more mouths than he can feed! But it turns out, there is method to this madness. When the next female comes, he will not fertilize her eggs when she deposits them. Instead, they become food for his already hatched tadpoles to eat and grow on.

Amazon milk frog

An Amazon Milk Frog, front view, eyes partially covered. Image taken at the Oakland Zoo.

And so you might wonder, why would this deception evolve? What problems are being solved by this method of reproduction and parental care? To try to figure this out, we have to look at what makes this frog different from other frogs. And the answer is simple: his home. Other frogs more typically use ponds and streams as their breeding sites. But living in the rain forest means that there are many more temporary bodies of water that can be used for breeding. These sites offer a few advantages- the most important being way less competition and fewer predators. They also don’t have to worry about currents. However, in order to exploit these potential breeding sites, they have to overcome some obstacles. First, the water in these plant structures can dry out quickly. So, for a frog to use this area to reproduce,  the young have to hatch and develop quickly, to ensure they can leave the water before the water leaves them. The 24 hour hatch time is an important adaptation that allows this frog to remain in the trees. The second problem is a lack of food. This frog species solves that problem by having females lay nutritious eggs for the tadpoles to eat.

Of course, other frog species solve this same problem without the deception. A close relative of this frog, T. hadroceps (no English common name), solves this problem with parental care from the genetic mom to her own offspring. She returns to deposit unfertilized eggs for her tadpoles every 2-3 days.

Either way, these behaviors evolved to solve a basic problem and to exploit a relatively predator and competitor free breeding site, that allows these frogs to spend their entire life up in the trees.

Amazon milk frog

An Amazon Milk Frog resting on a tree branch. Image taken at the Oakland Zoo.

Once again, I can’t talk about frogs without mentioning the world wide amphibian decline and to recommend visiting Save the Frogs for more information on the extinction threat many frog species are facing and to find out what you can do to help.

Tiger Salamander

Tiger Salamander. Image taken at the San Francisco Zoo.

Tiger salamanders are large burrowing salamanders found throughout North America. They have been the focus of a lot of research particularly because various species of tiger salamander have different possible developmental paths and how and why they take one path over another has been a fascinating area of study.

For example, some of these salamanders are neotenic. This means that when conditions on land are particularly harsh, they will retain some of their larval characteristics, like big, fluffy external gills and never complete metamorphosis into a terrestrial adult form. They will stay safely in the water for their entire lives. Although they keep larval characteristics, they can still reproduce.

And then there are several species of tiger salamander that have cannibal morph larva. That is, there are two larval forms, a smaller form that eats aquatic invertebrates, and then a much larger form that can also eat the smaller larval form.

Tiger salamander larva

A cannibal morph tiger salamander larva eating a non-cannibal morph tiger salamander larva. Image by David Pfennig and James Collins.

Scientists wanted to know what triggers a “typical” larva to morph into a cannibal larva? They discovered several environmental factors, that actually make a lot of sense. For example, cannibal morphs develop when they live in very dense populations with other tiger salamander larva. This makes perfect sense because if the population is dense, then there is a lot of competition for food and potential food if you can eat your own kind. Another factor that determines whether or not a larva develops into a typical morph or a cannibal morph is how closely related the larva around them are. If they are closely related to nearby larva, they are not likely to develop into a cannibal morph. Again, it makes sense because if they are related then they share genes and they don’t want to eat an animal that will increase the likelihood of passing those shared genes on to the next generation. Studies have also shown that when given the choice, cannibal morphs will choose to eat non-kin rather than their own kin. And yes, they can tell if they’re related and even how much they’re related to each other. Experiments indicate that it is probably by sense of smell.

Another question that had intrigued scientists is why don’t we see more cannibal species in nature? When you think about the benefits of cannibalism, such as removing competition for food and possibly mates if its sex specific cannibalism, as well as having a nearby food source, it seems like evolution would have selected for this more often. They found a good explanation for this one as well. Most diseases are pretty host specific. For example, while there are a few diseases that can be transmitted between us and say our cats, there are a number of diseases that can’t be.  Carnivores in general prey on the sick and the weak, or the easiest to catch prey. Laboratory results showed that cannibal tiger salamander larva did in fact choose to prey on the sick and were more likely to die from an acquired disease. And so cannibalistic tiger salamander species kind of have the best of both worlds. They aren’t cannibals unless the conditions are optimal for them to be so. Then some of them can switch.

And what adorable little cannibals they are!

Tiger salamander

A tiger salamander. Image taken at the San Francisco Zoo.

By the way, the California tiger salamanders are not doing so well and there has been constant fights from groups who want to develop on prime tiger salamander habitat to remove their protected status in California. The fight was won yet again this year when the California Fish and Game commission voted to keep them protected under the California Endangered Species Act. There are actually a lot of things working against these animals right now and they need the limited protection they are granted because of their status.  Stay informed and find out what you can do to help protect them at Save the Frogs, which incidentally will also save the salamanders.

If Wolverine was a Newt

Ribbed newt

Spanish ribbed newt. Image taken at the San Francisco Zoo.

These adorable little critters have been the subject of quite a lot of recent research and we’re learning a lot of new things about the fascinating way these animals defend themselves. It has several levels of defense, the first simply being to squirm a lot and try to get away. Since they’re quite slippery, this can be very effective. If that doesn’t work, they’ll move to phase 2 and secrete a nasty toxin that is irritating to humans, but is strong enough to kill a mouse and probably makes them taste bad or makes them even more slippery (many newt species ooze out toxins for defense). The Spanish ribbed newt is immune to its own toxin, which is particularly important for this species and that’s because of defense strategy #3.  As a last resort, they’ll actually push their ribs through their skin to act as defensive barbs. The ribs have been documented rotating as much as 65 degrees! The ribs protrude from small orange warty-looking bumps along their sides.

Spanish ribbed newt orange bumps

Spanish ribbed newt, side view. Note orange bumps where ribs protrude. Image taken at the San Francisco Zoo.

The orange spots might act as a warning to make the ribs more obvious. When they stick their ribs out, they also release antimicrobials, so as to prevent infection. When the threat is gone, the ribs relax back into place and they heal up.  Mind you, there is no permanent opening where the ribs come out, they are actually piercing their own skin each time they do this. The next step in this research is to make observations as to the effectiveness of this defense. I really can’t wait to find out what they discover.

Find more information about this research done by Egon Heiss and gang in this pdf of his publication or on the Caudata Culture website, which nicely summarizes their work as well as gives some good general information.

By the way, dramatic prairie dog…

dramatic prairie

Dramatic prairie dog, popular internet meme.

I’d like you to meet your new foe…

Dramatic Newt!!!

Dramatic newt

Dramatic newt, dramatic prairie dog's new foe. Image taken at the San Francisco Zoo.

The Gastric Brooding Frogs

Gastric Brooding Frog

Northern Gastric Brooding Frog; now extinct. Photo by M. Davies.

I really hate to start off the amphibian section of this blog with a bittersweet story, but at the moment it seems that all amphibian stories are heading that way, as there is a huge decline in their numbers around the world.  But these amazing frog species, the gastric brooding frogs, were my favorite amphibians, and they went extinct in my life time, just a few short years after they were discovered.

Why did I love them so much?  Well, what they are most remembered for is also what they got their common name from, and that is their amazing reproductive strategy.  When these frogs laid their eggs, the digestive acids in their stomachs would shut off and they would swallow their own eggs.  There the eggs would sit until they hatched, and the tadpoles would never see the light of day.  Instead, they completely developed into little froglets while still inside their mother’s stomach and to give birth, the mother would dilate her esophagus and 18-25 little froglets would jump out of her mouth, one at a time!

Gastric brooding frog and froglet

Gastric brooding frog with froglet emerging from its mouth. Photo by Mike Tyler

If that’s not cool, I don’t know what is.  In this way, the frog kept its eggs safe at the expense of not being able to eat for 6 to 7 weeks while the young were developing.

One interesting aspect of these frogs’ mysterious solution to egg predation is how they managed to shut off their stomach acid.  It appears that the digestive acids shut down because of chemicals being secreted by the egg jelly and the tadpoles.  Why is that important?  Because scientists thought that maybe this chemical held the secret to a fantastic ulcer treatment.  Unfortunately they never found out, nor will they ever find out.  And I will never be able to see my favorite frog in real life.

The University of Michigan has some great further reading on their Animal Diversity Web site.  Please note that the first picture in this blog is the northern gastric brooding frog, while much of the research and information provided here was about the southern gastric brooding frog.

If you are interested in why amphibian populations are declining world wide and what you can do to help, please check out Save the Frogs to learn more.  This is a fantastic organization focusing on education and research to help protect amphibians.