Big things happen in small rodents: grasshopper mice as a model for the evolution of pain resistance

This post is written by MSU grad student Lauren Koenig

Lauren Koenig trapping small mammals for a previous field project in Colorado

Life in the desert is full of extremes. Daytime temperatures are scorching, monsoon rains are torrential, and plants are sparse and spiky. Yet many desert animals, such as grasshopper mice (Onychomys torridus) and pinacate beetles (Eleodes longicollis), are able to thrive in these conditions.

So what is the key to survival? For these species, it is the development of extreme adaptations in response to their environment, as well as to each other.

The evolution of adaptations and counteradaptations between two species is known as an evolutionary arms race. This phrase may aptly bring to mind an image of two countries duking it out, building bigger and better nuclear missiles. In the case of mice vs. beetles, the beetle’s missile is a nasty chemical spray consisting of benzoquinones and the launchpad is at the base of its abdomen. When threatened, pinacate beetles will do a headstand, a position best suited to target an oncoming predator’s eyes, nose, and mouth. While pinacate benzoquinones are not deadly to humans, they wreak havoc on sensitive tissue. For a much smaller mammal, benzoquinones will burn and blind on an even more intense level.

A grasshopper mice attacks a pinacate beetle

In turn, the grasshopper mouse appears to have evolved a superhero trait of its own. The well-known entomologist Thomas Eisner first described this attack and claimed that grasshopper mice avoid being sprayed by placing the beetles butt-end in the sand so that the glands discharge harmlessly into the soil1. I’m not so sure that the case is so cut and dry, however. Using its front paws, the mouse will try and grab the beetle, keeping it still long enough to take an incapacitating bite. This manipulation isn’t enough to prevent an onslaught of chemical spray to the face and the mice show signs of discomfort (i.e. grooming, burying behavior). Both Eisner and I can agree, however about the truly remarkable end to this battle. Grasshopper mice are not deterred from their pursuit. They are swift, vicious, and persistent carnivores. The desert floor is littered with the empty shells of pinacate beetles that met a similar demise at the hands of the only rodent species that seems to consistently withstand the spray. Deer mice, the facultatively insectivorous cousins that share the same habitat and encounter the same insects as grasshopper mice, are much less persistent in their pursuit of pinacate beetles and consume them far less often2.

So what makes grasshopper mice such rare rodents? What secrets lie in their physiology that make them less like Mickey Mouse, and more like Monty Python’s killer rabbit?

It turns out that grasshopper mice have some very weird and fascinating responses to pain. In addition to pinacate beetles, they prey on all the classic horror film stars, like tarantulas, centipedes, and bark scorpions, which possess one of the most painful stings. An elegant study by Drs. Ashlee and Matt Rowe discovered that scorpion venom binds to a sodium channel receptor that switches the venom’s effect from pain to that of an analgesic3. Essentially, the mice use the scorpion’s own defense mechanism as the very tool that allows them to successfully eat scorpions, no matter how many times the mice are stung. Deer mice, in comparison, won’t survive long after the first sting.

Benzoquinone, however, does not target sodium channels. It is likely that benzoquinone targets TRPA1, a conserved calcium channel in the nose and mouth that is found across the animal kingdom, ranging from humans to drosophila. It mediates reception of pain, temperature, touch, spice, and caffeine, among others. This is an excellent starting point to begin exploring the mechanism for pain resistance in grasshopper mice – we know that they exhibit reduced sensitivity to formalin, another TRPA1 agonist3. TRPA1’s versatility ensures that any organism that develops an antipredator system through TRPA1 disruption could target many predators with a single stroke.  In response, a predator that had a modified TRPA1 channel immune to that disruption could take advantage of prey that is inaccessible to most of its competition.

Here is where things get interesting. There’s a reason why most animals have not evolved resistance to pain. Pain serves a critical function in the nervous system to warn the body of potential damage (i.e. it tells you not to walk on a broken foot so that the foot can heal). Prey, like scorpions, take advantage of this in order to signal that they are harmful. If an animal lives to eat again it likely learns to never, ever try and eat a scorpion – and that’s a good thing for both the predator and the prey. Therefore, the crucial function of pain in survival ensures that natural selection favors pain sensitivity. So how and why do pain-pathway adaptations exist?  

It is at the junction of this paradox that I aim to pursue my graduate research. By studying grasshopper mice as the exception to the pain-pathway standard, I hope to learn about the underlying mechanisms behind their pain tolerance.

Why should we care about a rodent sized war happening in the middle of the Arizona desert? As researchers discover more about TRPA1, we’re realizing that this receptor plays an even more integral role in the nervous system than previously thought. TRPA1 receptors serve many types of functions and are found even in humans. Not all the signals they send are welcome, however, as TRPA1 is involved in inflammatory, neuropathic, and migraine pain, as well as airways diseases and diabetes4. The more we learn about TRPA1, the more we can learn about our own responses to pain and how to block it. By studying animals in which pain blockage is successful, perhaps we too can someday swallow a pill-sized dose of grasshopper mouse superpowers.


  1. Eisner, T., & Meinwald, J. (1966). Defensive Secretions of Arthropods. Science, 153(3742),1341–1350.
  1. Parmenter, R. R., & Macmahon, J. A. (1988). Factors limiting populations of arid-land darkling beetles (Coleoptera: Tenebrionidae): predation by rodents. Environmental Entomology, 17(2), 280-286.
  1. Rowe, A. H., Xiao, Y., Rowe, M. P., Cummins, T. R., & Zakon, H. H. (2013). Voltage-gated sodium channel in grasshopper mice defends against bark scorpion toxin. Science, 342(6157), 441-446.
  1. Nassini, R., Materazzi, S., Benemei, S., & Geppetti, P. (2014). The TRPA1 channel in inflammatory and neuropathic pain and migraine. In Reviews of Physiology, Biochemistry and Pharmacology, Vol. 167 (pp. 1-43). Springer International Publishing.
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The Poetry of Scientific Experiments

This post is written by UW grad student Sonia Singhal

TL;DR: Like poems, “beautiful” scientific experiments have a cohesive, coherent structure where each part reinforces the whole. In this post, I analyze the structures of the poem “Easter Wings” by George Herbert and the Meselson-Stahl experiment from biology. This work is the opinion of the author, and does not necessarily reflect the views of BEACON or its researchers.

Throughout history, people have said that science removes the beauty from the world. Yet scientists often find great beauty in their work. Scientific experiments have even been called “beautiful” by other scientists. Why is this? What is it about certain experiments that gives the perception of beauty?

I propose that one element may lie in the structure of the experiments. Specifically, we perceive beauty when the individual pieces reinforce each other to form a cohesive, coherent whole. In this way, a “beautiful” scientific experiment is akin to a work of poetry.

In poetry, perhaps more than in any other type of writing, structure (or, as a poet would say, form) is paramount. Poetry is judged not only on what the poet says, but also on how she says it. Aspects of the how include how a reader would recite the poem – for example, the rhyme scheme and the rhythm – as well as the look of the poem on the page. Are the lines short or long? Are they on the left-hand side of the page or the right, or do they straddle the center line? Even white space is meaningful.

A concrete poem, whose shape reflects its subject, takes form to an extreme. I’ll use the concrete poem “Easter Wings,” written by George Herbert in the sixteenth century, to illustrate why structure is so important in poetry.

Lord, who createdst man in wealth and store,
Though foolishly he lost the same,
Decaying more and more,
Till he became
Most poore:
With thee
O let me rise
As larks, harmoniously,
And sing this day thy victories:
Then shall the fall further the flight in me.

My tender age in sorrow did beginne
And still with sicknesses and shame.
Thou didst so punish sinne,
That I became
Most thinne.
With thee
Let me combine,
And feel thy victorie:
For, if I imp my wing on thine,
Affliction shall advance the flight in me.

Herbert’s poem describes the second coming of Christ (a popular subject for writers of the time). However, the beauty of the poem does not come (solely) from its subject. It also comes from the way the poem’s structure reinforces its message and themes.

Since this is a concrete poem, let’s start with the general shape. When you look at the poem from a distance, without reading the words, what does the shape remind you of? (Hint: Tilt your head sideways.)

Herbert’s poem has two stanzas (blocks of text separated by white space), each with a winged, bird-like shape. Herbert achieves this visual effect by altering the length of the lines. He starts the stanza with a line of ten syllables. Each subsequent line has fewer and fewer syllables, until the lines in the middle of the stanza have only two syllables each. Herbert then increases the number of syllables per line until he returns to ten syllables in the final line of the stanza.

When we pair the shape with the text, we find that where the lines contract and expand is not arbitrary. The lines contract when Herbert talks about mankind or himself, made “less” (according to Christian doctrine) by the curse of original sin. In particular, the shortest lines contain words that denote dearth or scarcity: “poore” and “thinne.” One interpretation of the short lines might be that they represent the narrowness or short-mindedness that people can exhibit when they only think about themselves. In contrast, the lines expand when Herbert talks about his faith in God and Christ, which makes him part of something greater than himself.1

Herbert repeats structural elements within his poem. Most obviously, there are two stanzas, each with the appearance of a flying bird. Herbert repeats words and rhymes between the stanzas. Rhymes ending in “-ame,” such as “shame” and “same,” appear in the first half of both stanzas, while rhymes ending in “-ee,” such as “thee” and “me,” appear in the second half.2 The second half of both stanzas also includes “victory,” “flight,” and other words that relate to birds (“larks” in the first verse; “wing” and “imp” in the second. “Imp” is a falconry term – when you imp a bird with broken or clipped wings, you attach new feathers to its wings to allow it to fly again). The references to flight coincide with Herbert’s recovery of hope and faith. Even the last lines of both verses are structurally similar (compare “Then shall the fall further the flight in me” to “Affliction shall advance the flight in me”). The repetition makes the poem feel tightly knitted and could represent the strength of Herbert’s faith.

In “An Essay on Criticism,” eighteenth-century poet Alexander Pope said of poetry that “The sound must seem an echo to the sense.” In other words, structure in poetry must emphasize the meaning. Herbert’s poem exemplifies this philosophy. The bird-like shape of the poem emphasizes the themes of rebirth and renewed faith, while the tight repetition of words and phrases creates a sense of safety and security. The structure and the meaning of the poem resonate with one another, and this resonance makes the poem “beautiful.”

The value of structure extends beyond poetry. The scientific process has its own inherent structure:

  1. You ask a question.
  1. You form a hypothesis, or a reasonable explanation, about the answer.
  1. You run an experiment.
  1. The experiment gives you data (results) that either support or refute your hypothesis.

When each of these pieces (question, hypothesis, experiment, results) reinforces the others with no extraneous content – in other words, when the structure of the whole experiment echoes its core message – the experiment may resonate with us in the same way that a well-constructed poem does.

To explore this idea, I’ll use a classic experiment in biology, the Meselsohn-Stahl experiment, which was fundamental to our understanding of how DNA works.

DNA is a molecule found in all living things. Each time a cell divides, or a parent has a child, the parent’s DNA gets copied and passed on to the next generation. Because the building blocks of DNA were relatively simple compared to other molecules, its importance was originally underestimated. But in the first half of the twentieth century, the results of biologists’ experiments began to indicate that DNA was in fact necessary for life. It encoded information about whether a living being was human, animal, or plant, what it looked like; and how its body worked.

DNA’s shape was first proposed in 1953, by James Watson and Francis Crick.3 At the time, they knew that the building blocks of DNA included four different bases that contained nitrogen (specifically, adenine, cytosine, thymine, and guanine). Watson and Crick also knew that, in any particular DNA molecule, there were equal amounts of adenine and thymine bases, and equal amounts of cytosine and guanine bases, but different amounts of adenine/thymine versus cytosine/guanine. Based on a photograph of X-rays bouncing off DNA taken by Rosalind Franklin, Watson and Crick suggested that DNA was made of two strands that wound around each other in a double helix (Fig. 1). The bases were arranged in pairs between the two strands like rungs on a ladder: adenine with thymine, cytosine with guanine.

Figure 1. Basic shape of a DNA molecule. The two strands (yellow) form a double helix. Between them, adenine (green) pairs with thymine (purple), and cytosine (red) pairs with guanine (blue).4

This arrangement immediately suggested a way of copying DNA without losing the information it encoded. Because the bases are paired, it is possible to determine the sequence of one DNA strand from the other’s: A thymine on one strand always corresponds to an adenine on the other, while a guanine on one strand always corresponds to a cytosine on the other. If you separate the strands, you can make an exact copy of each one to get a new DNA molecule.

However, base pairing also meant that different researchers came up with different ideas on exactly how the process of replication, of copying and creating a new DNA molecule, might work. They suggested three different hypotheses (Fig. 2):

  1. Semiconservative replication. The original DNA strands separated and were copied, and the new DNA molecules were made of one strand of original DNA and one strand of new DNA.
  1. Conservative replication. The original DNA strands separated and were copied, but afterwards the original DNA strands re-paired, and the newly made DNA strands paired with each other. One molecule was made up only of the original DNA, and the other was made up only of new DNA.
  1. Dispersive replication. The process of copying DNA involved making short segments from both strands – in other words, copying some of one strand, then some of the other, then more of the first. Molecules made this way would contain some original DNA and some new DNA in both strands.

Figure 2. Illustration of three hypotheses for how DNA might replicate.5

In 1957, Matthew Meselson, a graduate student, and Frank Stahl, a post-doctoral researcher, designed a simple experiment with bacteria to determine which of these hypotheses was correct.6 They took advantage of the fact that nitrogen, which appears in the DNA bases, has a heavy form and a light form. Normally, the lighter form of nitrogen appears in living things, so using the heavy form of nitrogen in DNA would let Meselson and Stahl track specific strands. In their experiment, they put the heavy form of nitrogen into the DNA of bacterial parents, but they only let the bacterial children and grandchildren use the light form of nitrogen to make DNA copies. The weight of the resulting DNA would reveal how it had been copied.

  1. In semiconservative replication, the weight of the DNA would change with each generation. In the first (child) generation of bacteria, new DNA molecules in the child bacteria would be made of one strand of old (heavy) DNA and one strand of new (light) DNA. DNA in both parents and children would have an intermediate weight.

    In the second (grandchild) generation of bacteria, new DNA molecules could be copied from both the old (heavy) and new (light) strands. There would be a mixture of intermediate-weight DNA (copied from heavy strands) and light-weight DNA (copied from light strands).

  1. In conservative replication, the parent would still have only heavy DNA, and the children and grandchildren would have only light DNA.
  1. In dispersive replication, all new DNA molecules would have some old DNA and some new DNA. All molecules would be of intermediate weight in parents, children, and grandchildren.

When Meselson and Stahl weighed the DNA before and after the bacterial parents reproduced, the results were indisputable. Before reproducing, the parents only had heavy DNA. After the first generation, parents and children had DNA of equal, intermediate weight. After the second generation, Meselson and Stahl saw both intermediate-weight and light-weight DNA. DNA was being copied in a semiconservative manner.

Even before the results of the experiment had been formally published, scientists called Meselson’s and Stahl’s experiment “beautiful.” Meselson said the results were “clean as a whistle.” Maurice Wilkins, a physicist and molecular biologist, described their paper on the experiment as “elegant and definitive.” Another molecular biologist, Gunther Stent, said that “it really tells the whole story.” Stahl noted, many years later, that he had “been trying to do something half as pretty ever since.”7

In the same way that the form of “Easter Wings” reinforces its meaning, the tight, self-contained logic and cohesiveness of the Meselson-Stahl experiment strengthens its core message. Structure is a little more difficult to illustrate in an experiment than a concrete poem, so I’ll start with a reductionist approach.

Suppose we strip the experiment down to its minimal necessary information: the question (How does DNA replicate?) and the answer (Semiconservatively). I would argue that these are bare facts; on their own, they would probably not be considered beautiful. Let’s add in the hypothesis, which gives details on the copying mechanism (the DNA helix unwinds, and a new DNA strand is copied from each original strand. New DNA is thus made of one strand of old DNA and one strand of new DNA). Now the answer makes a little more sense. The explanation is logical, and it matches the pairing of bases in DNA. Next, we add back the experiment – how you go about testing this hypothesis (start only with heavy DNA and make new, light DNA from it. Then track how much of each type of DNA, heavy and light, there is over time). Under different hypotheses of DNA replication (semiconservative, conservative, or dispersive), we expect a different result, so this single experiment will immediately let us rule out two of the three. Finally, we add back the results (from heavy DNA, we go to DNA of intermediate weight, then a mixture of intermediate-weight and light-weight DNA). One hypothesis (semiconservative replication) is supported; the others are rejected.

By breaking the experiment down in this way, we can begin to understand how the individual pieces of the Meselson-Stahl experiment – question, hypotheses, experiment, and results – work together to form a coherent whole. First, every piece centers on a single issue (how DNA is copied), giving internal cohesion. At the same time, each new piece gives us additional information, providing the impression of direction. Finally, there is closure and completeness: The possibilities suggested by the three hypotheses are neatly tied up by the results. By the end of the experiment, we have come full circle with the answer to our question. The pieces of the Meselson-Stahl experiment strengthen and resonate with each other, and we perceive this resonance as beautiful.

Structure is important to a work in any genre – science or art – because it allows us to organize our understanding of the work’s messages and themes. When the structure focuses around and reflects the themes in some way, it provides additional power to the work. In this way, a close examination of structure can give us another lens through which to evaluate “beauty” across disciplines.


1 The same argument works on a theological level as well. The title, “Easter Wings,” tells us that this is a poem in celebration of Easter, or the resurrection of Christ after his death. In a reading from this perspective, short lines represent death, while long lines represent life or resurrection. The poet’s spiritual death and rebirth parallel the death and rebirth of Christ.

2 Six of the ten “-ame” and “-ee” rhymes even involve repetition of entire words: “became,” “me,” and “thee.”

3 Watson, J. and Crick, F. 1953. Molecular structure of nucleic acids. Nature 171:737-738.

4 Credit: DNA_simple.svg by user Forluvoft, Wikimedia Commons.

5 Credit: DNAreplicationModes.png by Mike Jones, Wikimedia Commons.

6 Meselson, M. and Stahl, F.J. 1958. The replication of DNA in Escherichia coli. PNAS 44:671-682.

7 Quotations from Holmes, F.J. 1996. Beautiful Experiments in the Life Sciences. In Tauber, A.I. (ed.) The Elusive Synthesis: Aesthetics and Science. Kluwer Academic Publishers, Dordrecht, pp. 83-101.

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Historic $12.7 million gift to BEACON Center, MSU College of Engineering

John R. Koza, who is considered the "father of genetic programming," has donated $12.7 million to the Michigan State University College of Engineering -- the college's largest individual gift.

John R. Koza, who is considered the “father of genetic programming,” has donated $12.7 million to the Michigan State University College of Engineering — the college’s largest individual gift.

The Michigan State University College of Engineering has received its largest individual gift in the history of the college.

A $10.7 million bequest from a California entrepreneur joins a previous cash gift of $2 million, bringing his total giving to $12.7 million to support the college and the BEACON Center for the Study of Evolution in Action, one of the National Science Foundation’s Science and Technology Centers.

The commitment is from computer scientist John R. Koza, who is considered the “father of genetic programming.”

The $10.7 million bequest will fund two endowed faculty positions to attract eminent scholars for the development of computational tools inspired by nature. New endowments also will advance genetic programming and evolutionary computation through endowed prizes, fellowships and programs to attract top graduate students and an increasingly strong pool of faculty members, said engineering Dean Leo Kempel.

“The creation of two new faculty endowments joining a third endowed chair, as well as endowed prizes and graduate student support, is unprecedented in the College of Engineering,” Kempel said. “We are very grateful to Dr. Koza for the advances our faculty will achieve and the students we will serve as a result of this extraordinary gift.

“With this gift,” Kempel continued, “and the previous investment by the National Science Foundation in the BEACON Center, Michigan State University will be the leading institution for transformational research and education in this important field of scholarship.”

Koza said he is delighted to make the investment in the BEACON Center and the College of Engineering and believes they are the best place to carry forward his life’s work.

“The mix of private support, NSF support, and backing from MSU, under the guidance of my good friend and colleague, Erik Goodman, means the BEACON Center and its ground breaking work will continue for many years to come,” Koza said. “My personal connections to BEACON, MSU and the partner institutions have been very gratifying and I look forward to what we can do together.”

MSU President Lou Anna K. Simon said the gift will create a hub of expertise and excellence in a demanding and promising field.

“John Koza’s continued generosity will empower us to build on his pioneering work. We are thankful for his vision and investment in the research and learning being done at Michigan State, which will resonate far into the future.”

Koza’s $2 million cash gift was received in 2014 and created the John R. Koza Endowed Chair in Genetic Programming. In August 2016, MSU welcomed renowned specialist in genetic programming and evolutionary computation Wolfgang Banzhaf as the Koza endowed chair.

Koza is a computer scientist and pioneer in the use of genetic programming, or GP. For much of his career, he was a consulting professor at Stanford University, teaching classes about evolutionary computation and genetic programming while conducting his research in that field.

“His ideas have helped to push back the horizon of what we believe computers can do now and in the future,” said Erik Goodman, director of the BEACON Center for the Study of Evolution in Action. The BEACON Center unites those who study natural evolutionary processes with computer scientists and engineers to solve real-world problems.

Goodman, who has been friends with Koza since they were graduate students in the 1960s and 1970s, called Koza a brilliant computer scientist.

“John Koza is frequently called the father of GP. His publication of four gigantic books introducing genetic programming to the world, beginning in 1992, helped to earn him this accolade,” Goodman explained. “In his books, he introduces the concepts of automated programming of computers by evolutionary processes.”

Goodman said Koza’s early work also included organizing a series of international conferences on Genetic Programming, which he and Goodman helped later to merge into a broader conference series on evolutionary computation, the Genetic and Evolutionary Computation Conferences.

“All of us owe some of our inspiration to the successes achieved by Koza,” Goodman added. “In the end, there may be few of us whose lives are not touched in some way or another by John Koza’s work.”

Endowed funds allow the university to provide continual support to specific programs and projects. The gift’s principal is invested and a portion of the annual earnings is used for annual program support.

The gifts support Empower Extraordinary, the $1.5 billion campaign for MSU that launched publicly in October 2014. To date, the College of Engineering has raised more than $76 million of its $80 million campaign goal.

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Dr. Judi Brown Clarke as a 2016 Sequoyah Fellow

This post is written by BEACON postdoc Wendy Smythe


Judi Brown Clarke (center) with her two sponsors Drs. Kenneth Poff and Holly Schaffer

On November 12th, Drs. Kenneth Poff and Holly Schaffer nominated BEACON Diversity Director, Dr. Judi Brown Clarke as a 2016 Sequoyah Fellow at the 2016 American Indian Science and Engineering Society (AISES) National Conference in Minneapolis, Minnesota. Judi will formally be inducted next September at the 2017 AISES Conference in Denver, Colorado.

The Fellowship is name in honor of Sequoyah, the great Cherokee Indian who perfected the Cherokee alphabet and syllabary in 1821, resulting in the Cherokee Nation becoming literate in less than one year.  In this spirit, AISES Sequoyah Fellows are recognized for their commitment to the mission of “excellence in STEM” and to the entire American Indian community. They bring honor to AISES by engaging in leadership, mentorship, and other acts of service that support the students and professionals in the AISES family.


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BEACON attends the 2016 AISES National Conference

This post is written by BEACON postdoc Wendy Smythe

BEACON co-sponsored Alaska Native (Haida) pre-college students who presented research projects, two summer interns, presented research talks, and volunteered as undergraduate and graduate research judges.

Left to Right: intern Lauren Smythe, Judi Brown Clarke, Wendy F. Smythe, Alexa Warwick, intern Sarah Peele

Postdoctoral Fellows Wendy F. Smythe presented the research talk “Traditional Ecological Knowledge Coupled with STEM” and Alexa Warwick presented the research talk “Treefrog tales: incorporating evolutionary biology in research, conservation, and education”.


Sarah Peele (left) and Lauren Smythe (right)

Summer interns Lauren Smythe and Sarah Peele presented their research projects at the National Conference. Lauren was mentored by Chandara Jack, Ph.D. presented the poster “Influence of Rhizobia and Herbivory on Rapid Evolution and Invasive Plants”. Sarah mentored by Wendy F. Smythe, Ph.D. presented the poster “What the HEK-Haida Ecological Knowledge Coupled with STEM”. Lauren and Sarah are both Alaska Native students, from the Kaigani Haida community of Hydaburg, Alaska.

Back row, left to right: Judi Brown Clarke, Traesea Miramontez, Sonia Ibarra, Wendy F. Smythe, Joe Hilliare, Lauren Smythe. Front row, left to right: Stasha Sanderson, Nevaeh Peele, Sarah Peele, Lillian Borromeo, Alexa Warwick

Back row, left to right: Judi Brown Clarke, Traesea Miramontez, Sonia Ibarra, Wendy F. Smythe, Joe Hilliare, Lauren Smythe. Front row, left to right: Stasha Sanderson, Nevaeh Peele, Sarah Peele, Lillian Borromeo, Alexa Warwick

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Mormyrids might be Pokémon: Can we see ‘evolution’ within a single individual?

This post is written by MSU grad student Savvas Constantinou

Savvas Constantinou preparing to inject single cell Brienomyrus brachyistius embryos.

I’m Savvas Constantinou and I am a second year PhD student studying Integrative Biology (IBIO) & Ecology, Evolutionary Biology, and Behavior (EEBB) in the Natural Science department at Michigan State University. I came to grad school to study Evolutionary Developmental biology; specifically what interests me is understanding how gene regulatory networks are modified over evolutionary time to generate new species and novel structures. I am probing this question using Mormyrids, a species-rich group of weakly electric fish. Mormyrids generate low levels of electricity (less than 1 volt) from their electric organ, and then sense this electric field on their skin with specialized cells; by monitoring distortions of their electric field these fish can locate and discriminate objects in their environment and communicate with their own species and discriminate other species.

Development of the larval and adult electric organs and the accompanying electric organ discharges in Brienomyrus brachyistius. A. Top to bottom. The larval electric organ differentiates from skeletal muscle in the body but is restricted from a region of the tail called the caudal peduncle. As the fish metamorphoses into an adult, the adult electric organ develops and discharges simultaneously with the larval electric organ. Eventually the larval electric organ is lost and the adult electric organ fully matures and develops penetrations. B. Top to bottom: The electric organ discharges from a larval fish (note the simplicity), from a fish discharging from both a nearly degenerated larval electric organ (arrow, note small relative amplitude) and a non-mature adult electric organ, and from an adult, fully mature fish (arrowhead note small head negative peak). Figure modified from Denzoit et al. 1978. The larval electric organ of the weakly electric fish Pollimyrus (Marcusenius) isidori (Mormyridae, Teleostei). Journal of Neurocytology 7: 165-81.

The electric organ actually develops twice within the lifetime of a single individual. In the species I work with, Brienomyrus brachyistius, they develop a larval electric organ about a week after hatching. The electric signature of the larval electric discharge is very simple. During metamorphosis from fry into an adult, the fish begin to develop their adult electric organ in a different location from the larval electric organ. The electric signature from the adult organ is more specialized and complex than the larval organ and begins discharging while the larval organ is still active. Eventually the larval organ is completely lost and the adult organ becomes more complex through a specific change in anatomy (see figure for clarity).

What excited me so much about this system was the idea of being able to “see evolution” within the lifetime of an individual. The function of the larval electric organ has yet to be experimentally determined: it is a costly structure as they discharge upwards of 100X a minute and it is like a homing beacon for electroreceptive predators. The adult organ is responsible for the more complex signals; variation in these signals have thought to been a driving force in speciation of mormyrids. So why do mormyrids waste the energy to even build the larval electric organ? I believe it has to do with evolutionary constraints.

The most basal member of the Mormyroidea is Gymnarchus niloticus, a weakly electric fish that has an electric organ similar to the Mormyrid larval electric organ in location and discharge complexity. I think that the ancestor to these groups had an electric organ that was like the larval electric organ of Mormyrids. The Gymnarchus lineage survived with some changes to the electric organ whereas the ancestral Mormyrid developed this second, more specialized electric organ that allowed for their rapid species diversification. I want to investigate what gene regulatory networks are at play to induce development of the adult electric organ. Is this different from the genes involved in differentiation of the larval electric organ? By probing these questions, I hope to test the idea that mormyrids have a strict developmental trajectory that requires formation of the larval electric organ before the adult electric organ can develop.

To further understand evolution and speciation in this group, I also plan to investigate the genes involved in the anatomical change that occurs during the final maturation of the adult electric organ. Through this final maturation the adult electric discharge becomes more complex, a feature implicated as a force driving sexual selection. After Mormyrids evolved the anatomical change to increase signal complexity, multiple species and groups have lost the ability, again suggesting its importance in speciation. To me, understanding what genes drive this process and how they are tweaked in their timing and spatial distribution of their expression to give rise to the amazing signal diversity of Mormyrids is fascinating.

I have been spending most of my time in my PhD developing the “toolbox” of techniques that will help me to answer the questions I am interested in. I have been optimizing laboratory breeding and fry rearing in B. brachyistius to allow me to study these developmental questions. I am a molecular biologist at heart, and have begun to test gene function using the gene modification technique CRISPR. CRISPR is a way in which nearly any region of the genome can be targeted for change: either to modify the DNA and disturb gene function or to direct addition of other genes (like Green Fluorescent Protein). I intend to use RNA-sequencing of larval and adult electric organs at various time points to determine what genes may be responsible for their development. My grand plan is to be able to silence genes involved in larval electric organ development, and then to see if an adult electric organ can still be produced when the larval organ has not.

Eventually I want to compare the gene circuitry regulating the development of electric organs among many species of Mormyrids as well as to those of Gymnarchus. By comparing changes in expression levels, timing, and location, I hope to bring insight into a potential genetic mechanism involved in allowing Mormyrids to speciate so successfully and rapidly. Stay tuned for future “shocking” information on Mormyrid electric organ development!

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Love is in the air (or maybe it’s just bacteria)

This post is written by BEACON managing director Danielle Whittaker

Danielle Whittaker holding a black and white warbler at Mountain Lake Biological Station, Virginia

When we fall in love with someone else, is it because they are our soul mates… or is it because we like the way their microbes smell? We think a lot about the importance of physical appearance and the content of what we say. But when it comes to attraction, we may have less control over our preferences than we think.

Just like humans, birds are thought to rely on sight and sound as their primary senses, yet smell turns out to play an important role in choosing a mate. For the last decade, I have been studying how birds use odors as indicators of a potential mate’s suitability. Dark-eyed juncos (Junco hyemalis) are songbirds found throughout North America that spend the summer breeding in habitats with cooler temperatures, especially in the mountains or far north in Canada. Like most birds, they produce preen oil from their uropygial gland, located above the base of the tail. This oil, which they rub into their feathers while preening, is a source of odor that transmits information about an individual’s species, sex, breeding condition, and hormone levels. This odor also relates to individual reproductive success: males that smell more “male-like” have more offspring, as do females that smell more “female-like,” suggesting that these compounds are also communicating information about reproductive health or ability.

The preen gland is located above the base of the tail

Recently, my collaborator Kevin Theis (former MSU postdoc, now assistant professor at Wayne State) and I have been studying the source of these odors. While at MSU, Kevin studied the bacteria in hyena scent pouches. These bacteria produce the odors that hyenas use to communicate with each other. He suggested to me that symbiotic bacteria in the preen gland could also be responsible for producing junco odors. We decided to test this hypothesis by sampling the bacteria in and around the preen gland, and determining whether any of the bacteria present were capable of producing these compounds. We found that the preen gland is home to a very rich and diverse microbial community. Even better, using the Microbial Volatile Organic Compound database, we discovered that many of these junco bacteria are known odor producers. Two genera in particular, Burkholderia and Pseudomonas, are capable of producing over half of the compounds in junco chemical signals – and these two bacteria were very common and abundant in our samples.

Scanning electron microscope image of bacteria in a junco preen oil sample

Our next step was to test whether removing these bacteria actually changed the juncos’ smell. I injected a broad-spectrum antibiotic into captive juncos’ preen glands, and sampled them before and after treatment. Compared to control birds that were injected with only saline, birds receiving antibiotics had significantly lower levels of three volatile compounds – 2-tridecanone, 2-tetradecanone, and 2-pentadecanone. These three compounds are the same ones that are correlated with reproductive success, suggesting that symbiotic bacteria could be responsible for a chemical signal that’s important in junco mate choice. We are now in the process of sequencing the bacterial swabs from the birds in this study, to examine which bacteria were killed by the antibiotics and to identify candidates responsible for producing the compounds.

Female junco incubating eggs at Mountain Lake Biological Station, Virginia

We are also now studying how these symbiotic microbes are transmitted between individuals. We have found that nestling juncos have bacterial communities very similar to their mothers, and less similar to their fathers. This pattern makes sense because it’s only mothers that sit on the nest and keep the nestlings warm as they are growing, and microbes are shared through physical contact. We also found that the adult male and female pairs were more similar to each other than they were to other adults of the same sex – again, physical contact is the likely explanation. Our next steps are to examine more closely the effects of social behavior on individual microbial communities, and whether an individual’s odor reflects their social patterns.

So the next time you find someone attractive, stop for a moment and wonder why. Is it the way their blue eyes sparkle when they say something witty? Or could it be the scent of bacteria… maybe even bacteria they got from somebody else?

For more information:

Whittaker, D. J., N. M. Gerlach, S. P. Slowinski, K. P. Corcoran, A. D. Winters, H. A. Soini, M. V. Novotny, E. D. Ketterson, and K. R. Theis. 2016. Social environment has a primary influence on the microbial and odor profiles of a chemically signaling songbird. Frontiers in Ecology and Evolution 4:90.

Whittaker, D. J. and K. R. Theis. 2016. Bacterial communities associated with junco preen glands: ramifications for chemical signaling. In Chemical Signals in Vertebrates 13, eds. Bruce A. Schulte, Thomas E. Goodwin, and Michael H. Ferkin. New York: Springer International Publishing, pp. 105-117.

Whittaker, D. J., S. P. Slowinski, K. A. Rosvall, N. M. Gerlach, H. A. Soini, M. V. Novotny, E. D. Ketterson, and K. R. Theis. 2016. It’s what’s on the inside that counts… or is it? Microbial vs. physiological mediation of sexually selected chemical signals in a songbird. Oral presentation at Evolution 2016.

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Better Together: Of Hyenas and Men

This post is written by MSU grad student Zachary M. Laubach

“A guy needs somebody―to be near him. A guy goes nuts if he ain’t got nobody. Don’t make no difference who the guy is, long’s he’s with you. I tell ya, I tell ya a guy gets too lonely an’ he gets sick.”

– John Steinbeck, Of Mice and Men

Myself and Philomon, the head chef and camp manager of the Serena Hyena Camp. During my time in Kenya, I came to see Philomon as a source of social support and dear friend.

The notion that our social environment is important to our health and well-being is not new. There are profound and heartbreaking historical illustrations of how social interactions (or lack thereof) shape behavior and physiology. For example, adults who once resided in Romanian Orphanages, notorious for their depraved lodging conditions and neglect, exhibit severe psychoses and debilitating mental disease 1,2. Likewise, famous primate studies from the 50’s and 60’s demonstrated the importance of maternal touch and interactions with peers to healthy psychosocial development 3,4. However, despite the flurry of convincing correlative results linking the early social environment to future stress-related disease, the underlying molecular mechanisms remained poorly understood until the mid 2000s when Drs. Michael Meaney and Mose Szyf showed that DNA methylation (a stable epigenetic mechanism that alters gene expression without changing the nucleotide sequence) is both responsive to social stimuli and has a direct effect on stress phenotype. These scientists found that offspring born to mothers who did not engage in licking and grooming behaviors had higher methylation of the glucocorticoid receptor gene, which resulted in an inability to respond to elevated stress hormones. The elegant part of this study was that cross-fostering (e.g., switching the rat pups at birth between high licking and grooming and low licking and grooming moms) revealed that the effects of DNA methylation were not due to genetics, but rather, a direct effect of maternal care during the first few postnatal weeks 5.

My PhD research extends current knowledge of the relationships among the social environment, DNA methylation, and biological condition using data from Dr. Kay Holekamp’s population of wild spotted hyenas in the Masai Mara of East Africa, Kenya. You might ask, ‘Why spotted hyenas?’

A snapshot of Bart, a dedicated mom still nursing her nearly full-grown cubs. This photo highlights the extent to which hyena moms care for their young, even when they are rapidly catching up in size!

Several aspects of spotted hyena biology make them a powerful and relevant study population for my research interests. First, hyena cubs depend on their mothers for nourishment and protection through 2 years of age, presenting a window of opportunity to quantify a variety of novel measures of mother-offspring interactions. I am collaborating with Julia Greenberg, another PhD student in Dr. Kay Holekamp’s lab, to quantify patterns of maternal care using archived behavioral data. We are interested in the proximity of mothers to their young, time spent nursing, and frequency of grooming. Second, in addition to living in clans, hyenas hang out in cliques within each clan. Our detailed observational data regarding the number of individuals in a clique, the nature of interactions within group-members, and the amount of time spent together can be used to quantify unique aspects of a hyena’s social support system (see a previous post by Julie Turner). This notion that social support is critically important to well-being has been found in both non-human primate and human studies where both mothers and their babies are in better condition when social support is stronger 6–8. Finally, hyena societies follow a strict and well-defined rank system, which is of particular interest to me because it is analogous to socioeconomic status in humans; rank determines access to resources, friends, and mates. Thus, findings regarding the relationship between rank and stress phenotype in hyenas may be relevant to studies of socioeconomic position and health in humans.

A pile of hyena cubs keeping each other company, dozing off after a long bout of play.

Spotted hyenas are wild, gregarious, and perhaps not all that different from other social species (like non-human primates and even humans). Another reason why I am interested in this species is because most epigenetic research to date has taken place in highly controlled rodent and primate populations, limiting generalizability of findings to gregarious animals. Dr. Holekamp’s study population, therefore, represents a unique opportunity to explore how naturally occurring social behaviors correlate with epigenetic mechanisms and stress outcomes in a wild species exhibiting complex sociality. One huge hurdle that I’ve encountered thus far revolves around the task of carrying out epigenetics research in a species whose genome is not yet publically available (NB: the genome of the spotted hyena was sequenced and annotated years ago, but the Beijing Genome Institute has not yet released it). Fortunately, with the help of experts at the University of Michigan and at the University of Minnesota, I was able to sequence the region of interest (the glucocorticoid receptor promoter) using a technique known as multi-species alignment. In brief, I identified a sequence of hyena DNA that is comparable to the established target region in humans and rats. Next, I mapped the sequence to genomes of species in the same order as hyenas (Carnivora) – namely, the cat, dog, and walrus. Then, with a touch of bioinformatics, I sequenced the region in hyena DNA so that we could measure a comparable set of epigenetic marks to those identified in the rodent and primate literature. In addition to gene-specific epigenetic marks, I am also measuring genome-wide methylation content, which can be thought of as a proxy for an individual’s genomic stability and overall condition. Taken together, I hope that the measures of gene-specific and genome-wide epigenetics will shed light on how early social experiences shape adult phenotypes.

Preliminary results and what’s in store. Based on our initial work, which showed strong effects of a hyena mom’s rank on her offspring’s genome-wide DNA methylation, I suspect that inter-individual relationships and social status interact in ways that profoundly affect phenotype. The ways in which social experiences affect biology is relevant not only to health of individual organisms, but also has potential to impact how natural selection shapes phenotypes over time. The latter is of particular interest to me, as it implies that social experiences play a role in evolution. It is my hope that what we learn from animal models like hyenas, primates, and rodents will compel us to step back, and consider that humans are also merely animals whose behaviors, physiology, and health are shaped by social experiences. However, unlike other animals, we are uniquely endowed with the capacity to recognize the impact of our social experiences on our biology and how they may transcend generations. Knowing this should motivate social support, and the impetus to move beyond I-llness to WE-llness 9, especially in a world championed by individualism.

  1. Chugani HT, Behen ME, Muzik O, Juhász C, Nagy F, Chugani DC. Local brain functional activity following early deprivation: a study of postinstitutionalized Romanian orphans. Neuroimage. 2001;14(6):1290-1301. doi:10.1006/nimg.2001.0917.
  2. Kaler S, Freeman BJ. Analysis of environmental deprivation: cognitive and social development in Romanian orphans. J Child Psychol Psychiatry. 1994;35(4):769-781. doi:10.1111/j.1469-7610.1994.tb01220.x.
  3. Harlow HF, Harlow M. Learning to love. Am Sci. 1966;54(3):244-272. Accessed August 21, 2014.
  4. Harlow HF, Zimmermann RR. The Development of Affectional Responses in Infant Monkeys. Proc Am Philos Soc. 1958;102(5):501-509.
  5. Weaver ICG, Cervoni N, Champagne FA, et al. Epigenetic programming by maternal behavior. Nat Neurosci. 2004;7(8):847-854. doi:10.1038/nn1276.
  6. Campos B, Schetter CD, Abdou CM, Hobel CJ, Glynn LM, Sandman CA. Familialism, social support, and stress: positive implications for pregnant Latinas. Cultur Divers Ethnic Minor Psychol. 2008;14(2):155-162. doi:10.1037/1099-9809.14.2.155.
  7. Silk JB, Beehner JC, Bergman TJ, et al. The benefits of social capital: close social bonds among female baboons enhance offspring survival. Proc R Soc B Biol Sci. 2009;276(June):3099-3104. doi:10.1098/rspb.2009.0681.
  8. Silk JB, Beehner JC, Bergman TJ, et al. Strong and consistent social bonds enhance the longevity of female baboons. Curr Biol. 2010;20(15):1359-1361. doi:10.1016/j.cub.2010.05.067.
  9. From an anonomysous quote.
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Kombucha: More Than Meets the Eye

This post is written by UT Austin undergrad researchers Katelyn Corley, Matthew Hooper, and Zachary Martinez

“What starts here changes the world.” This is the motto that we as students at the University of Texas at Austin have come to embrace and strive towards in our everyday lives. In 2016, we began conducting research at UT Austin. For most of us, this was the first time we conducted research. We also took part in iGEM (international genetically engineered machine), and attended the annual conference in Boston. Our research experiences broadly spanned topics including microbiology, molecular biology, and synthetic biology, but our main work in 2016 focused on studying the microbiome of kombucha, with an ultimate goal of creating a designer beverage by altering the kombucha microbial community.

Example of kombucha “brewed” in a test tube. The large mass at the top is a layer of cellulose, while the mass at the bottom and the stringy “material” throughout the tube are clumps of bacterial and yeast cells.

Example of kombucha “brewed” in a test tube. The large mass at the top is a layer of cellulose, while the mass at the bottom and the stringy “material” throughout the tube are clumps of bacterial and yeast cells.

Kombucha is a popular fermented tea beverage that is home to a variety of microbes, both bacteria and yeast. Many die-hard consumers of kombucha love its acidic qualities and its characteristic vinegar taste, while these same attributes are what often turn others away from the drink. More importantly, kombucha is commonly referred to by its producers as being healthy or “rejuvenating” due to the presence of probiotics that are said to aid in digestion. As undergraduate scientists, we are skeptical of these claims, particularly because no current scientific evidence supports them. To us, kombucha soon became a vast frontier full of gray areas and large unknowns. Is it healthy, and if so, what makes it healthy? If not, could we make it healthy? These questions are what continually drove us forward as both researchers and as members of a community who desire to put something good into the world.

So then what did we learn? Over the course of roughly 6 months, the three of us along with our team, studied the “mysteries of kombucha”. We first identified some of the microbes that are naturally found in the drink. Species of bacteria such as Gluconobacter oxydans and Gluconacetobacter hansenii became commonplace names in our lab as we characterized these organisms and attempted to genetically engineer them for future study. Another major contributor to kombucha that we identified was the yeast, Lachancea fermentati. Interestingly, we found two unique strains of this species in our samples of kombucha with different phenotypes, and both appear to be required for proper kombucha brewing. One grew more quickly, while the other produced higher amounts of CO2. This finding immediately intrigued us. Not only do an array of species of bacteria and yeast coexist in kombucha, but differences in members of the same species appeared to have evolved in the process! Differentiation in the species was a possibility that we had not considered at first. The community of organisms that exists within kombucha appears to have evolved in a way that was much more complex than we had initially imagined. Kombucha was not simply a tea drink that was commercially sold and consumed, but was an exciting example of the world of microbial communities, which possess aspects of evolution and symbiosis that are still not fully understood.

Members of the Austin UTexas 2016 iGEM Team (from left to right): Prachi Shah, Matthew Hooper, Zachary Martinez, Katelyn Corley, Stratton Georgoulis, Alex Alario, Ian Overman

Members of the Austin UTexas 2016 iGEM Team (from left to right): Prachi Shah, Matthew Hooper, Zachary Martinez, Katelyn Corley, Stratton Georgoulis, Alex Alario, Ian Overman

We had the privilege of presenting our research at the 2016 iGEM “Giant Jamboree” in Boston. This research competition is one of the most incredible opportunities offered to both undergraduate and post-graduate students in the field of synthetic biology. We spoke with other students who work in our field and shared many of our successes and difficulties along the way. Additionally, we had the chance to present our research on kombucha to scientists, who gave us feedback and additional suggestions for expanding our project in the future. Our future plans include studying how the microbial community changes during a single brewing cycle as well as how the community might collectively evolve over multiple brewing cycles.

The major take-away from this experience was that, there is still work to be done, but that it is important work. Many of us first saw this project as being fun and approachable, and though we still view our lab work in this way, we have now begun to see how the scope of this project extends into greater, more compelling fields of science. Kombucha offers immense outlets for exploring the limitations of synthetic biology, as well as in exploring the types of evolutionary changes that must occur to enable specialization and the coexistence of microbes. Additionally, if we were to create a “designer” kombucha beverage, we need to consider the potential evolutionary shifts that might occur as we alter the microbial community found within kombucha. The great part about science is that you never know where it will lead you. This project took us from a grocery store shelf holding a bottle of kombucha, to an international conference in Boston, to a situation where we are now beginning to see how our work could shed light on an area of science that is not fully understood. On behalf of the entire Austin UTexas iGEM team, we encourage others to never stop digging deeper into science.

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Social networks in spotted hyenas

This post is written by MSU grad student Julie Turner 

I’ve always loved animals. This love isn’t exactly unusual in young children, but my fascination and curiosity about animals has not wavered. Among my earliest memories as a toddler was catching turtles in my backyard because they were slow enough for me to grab. As I got older, I started reading everything I could about animals, starting with lions (like many kids who grew up in the ‘90s, I was enthralled with The Lion King—except in my case, the movie became a recurring theme in my life). While learning more about lions, I realized that I thought their family groups were fascinating! I moved on to reading everything I could about other animals that lived in family groups, which grew into an interest in animals that live in larger groups with complex relationships like bottlenose dolphins and orcas.

When deciding what to do after college, I knew I wanted to study animals with complex social interactions and came across a program that studied spotted hyenas in Kenya. Prior to learning about this program, the most I thought about hyenas was watching The Lion King. I figured that the portrayal of hyenas couldn’t be right—as wonderful as the movie is, it is not renowned for its biological accuracy. I started reading obsessively about a new species and found that hyenas are so cool! They live in groups called clans that consist of multiple families reaching up to 130 members. Like humans they live in fission-fusion societies which means that, though they’re all in the same clan, the individuals they associate with change as hyenas come together or split apart to be alone or join other individuals (Kruuk, 1972). Their societies are as complex as certain baboon species and vervet monkeys, which is rare to see in non-primate species, especially carnivores (Holekamp, Smith, Strelioff, Van Horn, & Watts, 2012). As it turns out, these social traits make hyenas a great animal to study if you’re interested in how lots of individual little interactions like greetings, aggressions, and hanging out go together to form a cooperative social group, otherwise known as sociality in animals. I am studying a small part of sociality, specifically how sociality develops in growing hyena cubs and what that means for them throughout their lives.

Figure 1. PhD candidate, Julie Turner, with a darted hyena in Kenya

Sociality, especially complex sociality, is surprisingly difficult to understand and even to observe. For instance, imagine you’re at work with your officemates or in a class of 100 people. You might have a general idea of who hangs around with whom, but would you know how often everyone associated with everyone else in the group? Could you name each person’s friends? Shelly may be friends with Max, but does Max consider Shelly a friend in return? Is anyone actively avoiding someone else? In studying humans, at least researchers can conduct interviews or give people surveys. So, assuming people are answering truthfully, these challenges are difficult but manageable. Now imagine that you want to be able to address these questions in an animal that doesn’t speak any language you may know or could easily learn (though we have researchers trying to learn how hyenas communicate right now).

One method scientists use to try to tease apart and try to explain complex relationships is using social network analysis (SNA). A social network isn’t just Facebook. A social network is a group of individuals or entities (businesses, classes, etc.) that are connected by relationships or interactions (associating together, being friends, writing papers together, etc.). Individuals are represented by nodes; relationships and interactions are depicted by lines between the nodes called ties.

Figure 2. Random network graph. Blue squares are nodes that represent individuals or other entities. The lines are ties that indicate which nodes are connected by a relationship.

Social network graphs, such as the one just described, help us visualize relationships that may be difficult to see simply by observing. These graphs are especially helpful with animals when we only can use observations of behavior to understand relationships and cannot rely on interviews and surveys.

So, we observe animals over enough time to see many interactions and then build a social network to represent relationships during that time period. Hyenas have the potential to have many different types of relationships. Let’s use this interaction as an example:

Figure 3. A picture of a typical hyena interaction with their names.

Here we have five hyenas in a session together where three individuals are acting aggressively towards another, and GALA is off to the side doing her own thing.

One type of relationship that social network analysis (SNA) can address is relationships that are undirected, also known as binary, like individuals just hanging out with each other. Though all five hyenas here are not necessarily interacting directly, they are all associating together. GALA can’t associate with HEL without HEL also associating with GALA. This association network would be represented as the following graph:

Figure 4. Undirected association network of the illustrative hyena interaction.

Or relationships can be directed, for instance, when one hyena acts aggressively to another, as when HEL, CHLE, and TICA are aggressive to IKA.

Figure 5. Directed aggression network of the illustrative hyena interaction. The direction of the arrow indicates who is being aggressive to whom.

Once relationships are graphed, we analyze aspects of these social relationships statistically through SNA. We can learn things like if one clan of hyenas is bonded by stronger relationships than another, or how one individual’s social role varies from another. I’m using SNA to look at how individual hyenas learn their social role or position in the clan and how that position then affects aspects of their life like their personality or longevity. We already have evidence that cubs “inherit” their mothers’ social network (Ilany & Akcay, 2016), but what does that mean for the cubs’ development? These questions are examples of what we are currently exploring in spotted hyenas. Learning more about the social lives of hyenas helps us to see that hyenas are much more than “nothing but slobbering, mangy, stupid poachers” (I just had to bring it back around to The Lion King).


Holekamp, K. E., Smith, J. E., Strelioff, C. C., Van Horn, R. C., & Watts, H. E. (2012). Society, demography and genetic structure in the spotted hyena. Molecular Ecology, 21(3), 613–632.

Ilany, A., & Akcay, E. (2016). Social inheritance can explain the structure of animal social networks. Nature Communications, 7, 1–10.

Kruuk, H. (1972). The spotted hyena: a study of predation and social behavior.

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