Category Archives: mimicry

An experiment in scientific discourse: Fluorescence of the rattlesnake rattle

I get the sense that many people feel as if science and scientists are in an ivory tower; that science is out of reach of most people because they don’t have the educational background or the quantitative skills typified by professional scientists.  I think also that sometimes scientists disregard the ideas of non-scientists because they don’t have the educational background or quantitative skills most scientists have.  I think that both of these notions are mistaken.

Science is a community endeavor.  It benefits form discourse; the tossing around of ideas and interpretations by multiple people from many different backgrounds.  Whether we admit it or not, all humans are bias.  Our thought processes and interpretations of the natural world are the result of our prior experiences.   Hence, science benefits from many different people eyeing up the same problems because what one person may see as an intractable problem or routine observation is seen as an easily solved problem or extraordinary phenomenon.

In an attempt to engage a wide community of people, both professional and non-professional in the human endeavor called science, below I describe a research project I am currently working on related to the ultraviolet fluorescence of the rattlesnake rattle.  I will be presenting a poster of this very project a the 2nd Biology of the Pitvipers meeting in a few days.  After the description, I provide a short URL to a form where you can leave your comments and suggestions about the scientific process in general and the fluorescence project, specifically.  I ask that you use the URL instead of the comments section of this blog so that I have everyone’s comments in one place in a user-friendly format.

Ultraviolet Fluorescence of the Rattlesnake Rattle: Preliminary findings

All animals communicate within their own species and between species. For example honey bees do the waggle dance to tell other bees in which direction and how far to a plentiful food source.  Rattlesnakes advertise their potentially harmful bite by rattling the rattle on their tail.  Essentially, communication is the transfer of information from a sender to a receiver in which both parties benefit from the information exchange.  In many cases it is helpful to send information in more than one sensory channel.  For example some rattlesnakes use an auditory signal and a visual signal (some rattlesnakes have a conspicuously colored tail).

Fluorescence is a physical phenomenon in which light is emitted when the electrons of a substance are excited and change energy levels, whereby in the process photons are released.  The late, great rattlesnake biologist Laurence Klauber noted over 50 years ago that the rattlesnake rattle fluorescences under ultraviolet light.  No one has investigated the phenomenon since even though it is known that other animals utilize UV fluorescence, including parrots, many fish, and scorpions.Diversity_of_fluorescent_patterns_and_colors_in_marine_fishes_-_journal.pone.0083259.g001.png (1620×2741)

Our study had three objectives:  1) Develop methods to quantitatively  assess rattle fluorescence, 2) Document interspecific variation in rattle fluorescence, if it exists, and 3) Test hypotheses regarding the function and biological role of rattle fluorescence.

To meet these objective we built a 3×3 UV-LED (395-400 nm) light array in a black box and photographed rattlesnake rattles.  We utilized western diamondback and prairie rattlesnakes from the Northwestern Oklahoma State University Museum of Natural History.  We then quantified the intensity of the fluorescence using computer software similar to Photoshop.

We found that Western diamondback rattlesnakes exhibit more intense fluorescence than prairie rattlesnakes.

Rattlesnake rattles fluorescing under Ultraviolet light.

Rattlesnake rattles fluorescing under Ultraviolet light.

We have come up with a few ideas about why this might be.  First, it is possible that the fluorescence is a signal enhancer (that is how humans use fluorescence; that’s what Woolite and Tide do do to your clothes).  We thought this might be related to differences in habitat use or activity in these species, but they use very similar habitats (at least in Oklahoma) and both are active at night (there is available UV at night, however).  It is interesting to note that the Western diamondback has a banded tail which is also conspicuous.

Another possibility is that the fluorescence enhances the mimetic similarity between the rattle and segmented insects.  Several species of rattlesnakes exhibit a behavior called caudal luring in which they wiggle their tails to lure food within striking distance.  The video at this link is of copperheads luring, which are close relatives to rattlesnakes.

So, now is your chance to think like a scientist.  Follow the link below to a Google form that will provide you an opportunity to record your thoughts on this research.

 

The form can be found here:  http://goo.gl/vmGiXU

 


Keep your eye on the prize

I want to write a quick post on why I teach.  Not just why I teach, but why I enjoy teaching at a small liberal arts university (at least as liberal as it can be in NW Oklahoma, which isn’t very ;-)).

The story starts about a year ago when I got an email from the Oklahoma EPSCoR office announcing a small grant opportunity for undergraduates.  I read the announcement and it said that preference would go to projects at primarily research institutions working on problems in energy, but that all were welcome to apply.  I asked a student of mine who I knew would be around over the summer and would be interested in getting some research experience.  We tossed around a couple of ideas and decided we would test an hypothesis about mimicry in a little studied snake of Woods County, Oklahoma called the long-nosed snake (Rhinocheilus lecontei).  It was definitely a long shot, but we wrote up a short proposal and submitted to the program.  I had my doubts given the nature of the work and our low standing among research institutions in Oklahoma.  Amazingly we were awarded the grant

Now, Long-nosed snakes look somewhat like coral snakes in that they are black, red, and yellow banded.  The weird thing is that there are no coral snakes in Northwestern Oklahoma, so we wondered if the banding pattern afforded the snakes any protection from potential avian predators since many birds migrate to tropical habitats in the winter that are home to venomous tri-colored coral snakes.  To test the hypothesis, we created 400 clay models of tri-colored brown snakes and placed them around east central Woods County.  If birds pecked or grabbed the models they would leave behind tell-tale marks in the clay.  We later discovered that mammal teeth marks are also preserved in the clay.

The student worked all summer fashioning models, placing them in the field, collecting them and looking them over for evidence of depredation.  She learned field work is not always glamorous, especially when it’s 98 degrees and your clay models are melting.   Preliminary analysis showed the colored models were avoided by birds, but we were not sure if they were avoided because of the warning coloration, or because the banded pattern served as a disruptive pattern on the grass background.  To find out the student created 100 more models and laid them out on white backgrounds so that they banding was not disruptive on the grass background.  This would tell us if was avoidance or camouflage.  Unfortunately, this stage of the project was thwarted by a plague of locusts that literally ate most of the clay models.  Who knew locusts ate clay!

Undaunted the student wrote up a paper detailing the project.  I tightened it up a bit and made some suggestions and it looked to be a decent little paper on the protective coloration of R. lecontei.  I asked her if she wanted to submit it as a short paper to a peer-reviewed journal.  She agreed and formatted the paper herself according to the journals Guide to Authors.  We submitted the paper together last week and waiting with crossed fingers to hear back from the editors.

Long-nosed snakes resemble venomous coral snakes.

Long-nosed snakes resemble venomous coral snakes.

I know this is getting to be a long post, but for those of you not in science, this is a pretty big deal for an undergraduate to submit a paper for publication.  Personally, I am proud of the experience I was able to provide this student.  She “did science” from start to finish.  She assisted in writing the grant, collected the data, assisted in data analysis, wrote parts of the manuscript, and submitted the paper.  She presented the results of the research at our campus research day and won second place (the student who won did her research at one of the state’s R1 schools).

Things don’t always go your way, but if you give it your best shot and keep your eye on the prize, Nothing can stop you.  Not R1 universities nor swarms of locusts.


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