Herps in the News: Leatherback Turtle Migration Study

 

 

The main subject of this article was the migration patterns used by the leatherback sea turtle, Dermochelys coriacea, identifying potential danger zones in their paths.

The leatherback turtle is the world's largest sea turtle, as well as one of the most critically endangered species. Using this very large turtles patterns of migration allows for a new understanding of the most used areas of the Pacific Ocean by this turtle. This allows for an adjustment in fishing practices, hopefully reducing new deaths of this unique species.

These turtles are the widest-ranging marine turtle species and can migrate across the entire ocean, if necessary. This can increase the likeliness that they are caught in fishing gear, especially on the way to or from their foraging grounds to nesting beaches. This interaction with a number of fisheries is believed to be one of the leading causes of death, particularly in the Pacific Ocean, where the survival number of the leatherback turtle has dropped by more than 90% since 1980. These "hot spots" are being assessed to determine if limiting fishing at particular times of year may be effective for the protection of these large, wonderful creatures.

Overall, they found that of the two populations of leatherback turtles that nest either in the Eastern or Western Pacific, both were almost equally at risk of a negative human interaction, mainly fishing gear, because of the wide distributions of one populations and the very small distribution of the other that can cause them to have major changes in their migrations due to food concentrations.

I did my class powerpoint lecture on Sea Turtle Migration and this article was extremely interesting to me to read. While doing my lecture I found that finding information on the Leatherback Sea Turtles migration habits was very hard to come by. They have a very large (obviously since they can get up to 6 feet in length), soft carapace that can make it difficult to attach a satellite transmitter to, which is how they track the migration routes. It was interesting to learn why these turtles are extremely endangered, due to these said "hot spots" that they travel the most putting them more at risk of interacting with fishing gear from humans. Hopefully something will be done to fix this problem and allow for these turtles to regrow their population, as they are long-lived animals, but they take a long time to reach maturity.


References:
http://www.sciencedaily.com/releases/2012/03/120301103754.htm#.T3UVzJw_FOU.mailto

Brown Basilisk

Striped Basilisk
Basilicus vittatus
Size: Snout to vent= 6 in, Total length= 2 ft. Females are smaller than males
Sex: Male (prominent crest)
Natural Habitat: Mainland and coastal areas of Central America (near water bodies)

Brown basilisks are unique lizards found throughout the tropics of Central America and due to the pet trade they have even established populations in Florida. These lizards are omnivorous eating a variety of things such as insects, berries, other invertebrates, baby mice and even small fish. This species is aboral spending most of its time in trees but is also heavily dependent on heat sources and more importantly a large body of water as this species is also highly aquatic. Basilisks are perhaps most famously known as "Jesus Christ lizards" as they have the ability to run along the water's surface for an extended period of time. This is made possible by their toe scales on their hind limbs as they are wedge shaped to better distribute weight and better prevent breaking the water tension. This unique ability helps the species to avoid many potential predators. I saw this particular species in Costa Rica near a river bank. This was truly a remarkable experience for me to see these amazing reptiles and their unique ability to run on water as these are some of the most remarkable lizards in the world when seen in the wild.

Notophthalmus viridescens (Eastern Newt)

Notophthalmus viridescens (Eastern Newt)

Field Experience & Observation: On our very first field trip to the Caw Caw Interpretive Center in Ravenel, SC we found several Notophthalmus viridescens or the Eastern Newt. Newts are their own salamander family and are distinguished from other salamanders for their indistinct costal grooves and non-slimy rougher skin. These Eastern Newts had been caught in the minnow traps that were placed in a very wet and muddy area. These newts were a deep rep with the tell-tale large red outlined black spots on their backs (we did not count to find all 21 spots) and speckles of dark spots on their bellies. This red coloring is what distinguished them from being adults since adults are yellowish to dark greenish brown. All were in the eft stage, even though the minnow traps were found in the water. These efts were pretty hefty at about 3 inches long, but despite our efforts it was too hard to figure out their sexes (males have high tail fins, black tubercles on their thighs/rear feet, and a swollen cloaca when breeding). With both the friendly newts and no-see-ums, Caw Caw was a beautiful place to visit. I really liked getting to find these newts because I have never seen them before in their native habitat. 

Life History Stages & Behavior: I think that newts have the coolest life history of all the amphibians that we have studied this year in lab. Overall newts are aquatic critters, except for their terrestrial “eft” or juvenile stage. Aquatic eggs will become aquatic larvae that then transform into terrestrial efts. Some species however will skip this eft stage and exhibit neotony. Efts do not like direct sunlight, but they are not afraid to venture around during the day light. I think that the efts are not afraid because their bright coloring warns predators that they will secrete toxins from their skin glands. When efts are changing into from larvae they can be a yellowish color and when changing into adults their coloring can become very dark to almost a black color. The most amazing aspect of these morphological changes are the presence of gills, loss of gills for terrestrially, and the regaining of gills for adulthood.

Habitat & Range: Newts like ponds, small lakes, marshes, swamps, ditches, quiet areas of streams, and other places with continuous unpolluted water. Most of these bodies of water will have few fish (i.e. fewer predators) and lots of aquatic vegetation to hide in. Adults are seen to swim, crawl along the bottom, and just rest in a motionless state. Terrestrial efts will live in the moist woodland areas that around their adult counterparts.

Within the U.S. there are four regional varieties of the Eastern Newt – N. viridescens viridescens (Red Spotted), N. viridescens dorsalis (Broken-Striped), N. viridescens lousianesis (Central), N. viridescens piaropicola (Peninsula). All of these regional varieties exhibit a difference in coloring and patterns along with some other life habits like neotony.

So which one did we find at Caw Caw? Based on the range map it should have been the Central Newt that is normally found without red spots (or their spots will be partly outlined in black) in swamplands, woodland swamps, ditches and river bottoms. The Central Newt often skips the eft stage because of harsher (hotter, drier) environmental conditions. However, the Red Spotted and Central varieties are very similar and they can intergrade. I think that the ones that we found at Caw Caw are Central variety because this is a great habitat they were exhibiting the eft stage.

Sources:

Reptiles & Amphibians Eastern/Central Guidebook
http://www.caudata.org/cc/species/Notophthalmus/N_viridescens.shtml

She-male and Male: Tales from the Mating Ball

            The red-sided garter snake (Thamnophis sirtalis parietalis) demonstrates an unusual reproductive behavior involving multiple morphs of the animal’s male form. In order for either male morph to elicit mating behavior from the female, it must display several different behaviors of its own. Upon encountering the female, the male will press his chin into her dorsal skin and flick its tongue rapidly. He will then undulate his body along the female. If the female is sexually receptive, intromission will occur. This behavior commonly occurs at a ratio of many males to one female in a mating ball.

            Female garter snakes also play a role in sexual receptivity. Females produce a pheromone that delivers chemical cues to the male garter snake’s vomeronasal organ (VNO). Previous studies suggest that the male’s tongue flicking delivers the compound to the VNO.

            The present study aimed at identifying this compound through a bioassay. Chemical extracts were presented on paper towels to courting males and their responses were recorded. Female pheromones were obtained and fractionated and the active compounds were presented to the males one at a time. The pheromone was identified as methyl keytone, a nonvolatile contact pheromone.

            When attempting to mate, normal males typically ignore other normal males because the normal morph does not produce the same quantity of methyl keytone as the female. The normal male also produces a chemical called squalene. An interesting component of the red-sided garter’s pheromone system is perhaps in the alternate male morph, referred to in the literature as the “she-male.” The she-male is indistinguishable from the normal male morph and elicits mating behavior from the normal male. The she-male is a male mimic of the female and has comparable levels of methyl keytone to the female and does not produce any squalene.

            The normal male is sexually receptive to the she-male and will attempt to mate with the she-male morph in the same way that it does the female. When in the mating ball, the she-male will induce some of the normal males to move away from the female. The normal males begin their unproductive courting of the she-male and the she-male begins courting the female.

            Previous research suggests that the she-male is more than twice as successful at copulating with the female as the normal male. The she-male also contains about three times as much testosterone as the normal male. We typically think of testosterone as masculine and a characteristic that would be unattractive to the normal male morph. The article hypothesizes that although there is a higher level of testosterone in the she-male, this testosterone is converted by aromatase into estrogen in the skin, resulting in mating behavior from the normal male.

Mason, R.T. (1993). Chemical ecology of the red sided garter snake, Thamnophis sirtalis parietalis. Brain, Behavior and Evolution 41: 261-268.

Ancient World of Herps

http://www.bbc.co.uk/news/magazine-17544885

This article discusses a recent opening at the Smithsonian. This display features what scientists imagine a giant snake called a "titanoboa" may have looked like. Believed to be an ancient relative of the anaconda and boa constrictor,  the titanoboa was believed to be 50 feet long, based on skull fragments found last year and vertebrae fragments found in an open coal pit in 2002.

 Scientists were surprised to find fossils of the skull because snake skulls are typically very fragile, and after the flesh decomposes, the snake skull usually breaks into many different pieces. Scientists said that this was one of few snakes to make it into the fossil record because of how fragile the skeletons are. They estimate the reptile lived around 60 millions years ago, and it was much hotter than it currently is now. This has been interpreted to mean that with current global warming trends, eco-systems will still be able to cope with the heat and higher CO2 levels. When asked if titanoboa could make a return, Dr Jaramillo said "As the temperature increases you have the probability they will come back,but it takes geological time to develop a new species. It could take a million years - but perhaps they will!"

Natural History: Scincella lateralis

Two weeks ago our lab took a field trip to the Dixie Plantation in Edisto, SC.  We found a number of different specimens, but my favorite by far was the ground skink (Scincella lateralis).  Although my opinion on the best herp caught might be biased due to the fact that I myself caught this particular lizard, it is still fair to say these are some interesting little creatures.

I found the little lizard under a log in the forested area just a few yards off the trail we were walking.  He was very good at evading capture by quickly burrowing under nearby leaf debris, and upon capture it was quite easy to tell that the animal was a little exhausted.  The sides of the small skink were quickly being pushed in and out by the ribcage, a great example of negative pressure ventilation.

Ground skinks are small lizards of the family Scincidae and are found throughout much of the eastern half the US and into northern Mexico.  It is one of the smallest lizards found in North America with adults ranging in size from 3-5.5".  The one I found was approximately 3" long (snout to tip of tail).  These skinks live in a variety of habitats, including deciduous or mixed deciduous/coniferous forests, hedgerows, and the edges of streams and ponds.  They are a fossorial species which spend the majority of their life under leaf litter on forest floors.  And unlike many other species of skinks, they rarely climb.  Its primary means of locomotion is to wiggle through leaf litter with undulating movements, as I got to see first hand in the field.  They're coloration helps them blend in very well with the forest floor.

Ground skinks lay small clutches from as few as one egg to as many as six.  Females lay eggs under rotten logs or debris in the summer time. It is expected that these small lizards may lay several clutches per season but the specifics are still unknown.

Venomous species of snakes myth

Many people overestimate the amount of deaths caused each year by venomous snakebites. This may be in part because, at least in areas where they are rare, media coverage goes into overdrive. This can be related to the pop culture view of how many shark attacks happen each year, and since they don't happen all that regularly, news castors see it as an opportunity for an interesting story. Once put into the public eye it tends to create a little bit of widespread fear of the species. This in turn leads people to hunt the species out and kill them or spread their misconceptions. In reality venomous species of snakes only make up about ten percent of all the snakes known worldwide, and in areas where there actually are native venomous species, these species are considered rare, and most snakebites are caused by human error, either because a person was trying to kill a venomous species out of fear, or in some way not giving due respect to the snake. Many people do not consider the fact that when they come across a snake, which are generally much smaller than people, and in no way considering that person as a meal, that person is going to be considered a predator, and if necessary the snake will defend itself, so generally it is best to keep a safe distance from species that one cannot identify with confidence. However with the media's role in inciting fear of all snakes many people still believe every snake they come across could be venomous, and that's when the mistakes happen. No snake native to the United States is capable of eating a person so any perceived aggressiveness towards a person is strictly in defense. If a person is bitten by a snake it is important to gather as many details about the individual snake as possible for proper identification, without overestimating size or things of that nature. It is also important to note that snakes are typically shy creatures and will do their best to make an escape should they be cornered or captured, so if one does not want to get bitten, then all one has to do is leave a snake alone if they see one.