Tuesday, April 16, 2019

Does Social Status Change Brains?

A reposting of an original article in The Scorpion and the Frog.

Photo by The Grappling Source Inc.
at Wikimedia Commons
Being subordinated is stressful. The process of one individual lowering the social rank of another often involves physical aggression, aggressive displays, and exclusion. In addition to the obvious possible costs of being subordinated (like getting beat up), subordinated individuals often undergo physiological changes to their hormonal systems and brains. Sounds pretty scary, doesn’t it? But what if some of those changes are beneficial in some ways?

Dominance hierarchies are a fact of life across the animal kingdom. In a social group, everyone can’t be dominant (otherwise, life would always be like an episode of Celebrity Apprentice, and what could possibly be more stressful than that?). Living in a social group is more peaceful and nutritive when a clear dominance hierarchy is established.

Establishing that hierarchy often involves a relatively short aggressive phase of jostling for position, followed by a longer more stable phase once everyone knows where they fall in the social group. Established dominance hierarchies are not always stable (they can change over time or from moment to moment) and they are not always linear (for example, Ben can be dominant over Chris, who is dominant over David, who is dominant over Ben). But they do generally help reduce conflict and the risk of physical injury overall.

Nonetheless, it can be stressful to be on the subordinate end of a dominance hierarchy and these social interactions are known to cause physiological changes. Researchers Christina Sørensen and Göran Nilsson from the University of Oslo, Cliff Summers from the University of South Dakota and Øyvind Øverli from the Norwegian University of Life Sciences investigated some of these physiological differences among isolated, dominant, and subordinate rainbow trout.



A photo of a rainbow trout by Ken Hammond at the USDA.
Photo at Wikimedia Commons.
Like other salmonid fish, rainbow trout are aggressive, territorial and develop social hierarchies as juveniles. Dominant trout tend to initiate most of the aggressive acts, hog food resources, grow larger, and reproduce the most, whereas subordinate trout display less aggression, feeding, growth, and reproduction. The researchers recorded the behavior, feeding and growth rates in three groups of fish: trout housed alone, trout housed with a more subordinate trout, and trout housed with a more dominant trout. The researchers also measured cortisol (a hormone involved in stress responses), serotonin (a neurotransmitter involved in mood, the perception of food availability, and the perception of social rank, among other things) and the development of new neurons (called neurogenesis) in these same fish.

This video of two juvenile rainbow trout was taken by Dr. Erik Höglund. Here is Christina Sørensen’s description of the video: “What you see in the film is two juvenile rainbow trout who have been housed on each side of a dividing wall in a small aquarium. The dividing wall has been removed (for the first time) immediately before filming. You will see that the fish initially show interest for each other, followed by a typical display behaviour, where they circle each other. Finally one of the fish will initiate aggression by biting the other. First the aggression is bidirectional, as they fight for dominance, but after a while, one of the fish withdraws from further aggression and shows only submissive behaviour (escaping from the dominant and in the long run trying to hide... and as is described in the paper, depressed feed intake). The video has been cut to show in quick succession these four stages of development of the dominance hierarchy”.

The researchers found that as expected, the dominant trout were aggressive when a pair was first placed together, but the aggression subsided after about 3 days. Also as expected, the dominant and isolated trout were bold feeders with low cortisol levels and high growth rates, whereas the subordinate trout did not feed as well, had high cortisol levels and low growth rates. Additionally, the subordinate trout had higher serotonin activity levels and less neurogenesis than the dominant or isolated trout. These results suggest that the subordination experience causes significant changes to trout brain development (Although we can’t rule out the possibility that fish with more serotonin and less neurogenesis are predisposed to be subordinate). In either case, this sounds like bad news for subordinate brains, right? Maybe it is. Or maybe the decrease in neurogenesis just reflects the decrease in overall growth rates (smaller bodies need smaller brains). Or maybe something about the development of these subordinate brains improves the chances that these individuals will survive and reproduce in their subordination.


A crayfish raising its claws. Image by Duloup at Wikimedia.
Research on dominance in crayfish by Fadi Issa, Joanne Drummond, and Don Edwards at Georgia State University and Daniel Cattaert at the University of Bordeaux helps shed light on this third possibility. Crayfish (which are actually not fish at all, but are freshwater crustaceans that look like small lobsters) form long-lasting and stable social hierarchies. If you poke a crayfish in the side, an isolated or dominant crayfish will turn towards whatever poked it and raise its posture and claws to confront it; A subordinate crayfish will do one of two maneuvers that involves lowering the posture and backing away from whatever poked it. Furthermore, dominant and subordinate crayfish have different neuronal activity patterns in response to being poked, and part of this difference involves differences in the activity of serotonergic neurons.

It appears that the brains of dominant and subordinate individuals function differently and part of this difference involves serotonin. This may help dominant animals to continue to behave in a dominant fashion and subordinate individuals to continue to behave in a subordinate fashion, thereby preserving the peace for the whole social group.

Want to know more? Check these out:

1. Sørensen, C., Nilsson, G., Summers, C., & Øverli, �. (2012). Social stress reduces forebrain cell proliferation in rainbow trout (Oncorhynchus mykiss) Behavioural Brain Research, 227 (2), 311-318 DOI: 10.1016/j.bbr.2011.01.041

2. Issa, F., Drummond, J., Cattaert, D., & Edwards, D. (2012). Neural Circuit Reconfiguration by Social Status Journal of Neuroscience, 32 (16), 5638-5645 DOI: 10.1523/JNEUROSCI.5668-11.2012

3. Yeh, S., Fricke, R., & Edwards, D. (1996). The Effect of Social Experience on Serotonergic Modulation of the Escape Circuit of Crayfish Science, 271 (5247), 366-369 DOI: 10.1126/science.271.5247.366

4. Issa, F., & Edwards, D. (2006). Ritualized Submission and the Reduction of Aggression in an Invertebrate Current Biology, 16 (22), 2217-2221 DOI: 10.1016/j.cub.2006.08.065

Tuesday, April 9, 2019

What To Do If You Find Orphaned Wildlife

A repost of an original article from The Scorpion and the Frog.

A nest of baby cottontails waiting for sunset when their
mom will return. Image by Jhansonxi at Wikimedia.
Spring is finally in the air, and with Spring come babies! Finding baby animals in the wild is thrilling, but also concerning. Does this animal need your help? Where is its mom? What do you do?

Whenever possible, baby animals will do best when we leave them in the care of their mom. Even a well-meaning human is seen by a wild animal as a threat. Our interactions with them cause them extreme stress that can cause serious health problems and even death. Furthermore, if we take a baby animal home, it will not be able to learn its species-specific behaviors and skills and it can lose its natural and healthy fear of humans. It is also very hard to meet the specialized dietary needs of a wild animal in a captive setting. Taking a wild animal home can cause problems for us as well: many carry diseases that can be transmitted to our pets or even ourselves. And most wild animals are protected by state and federal laws that prohibit unlicensed citizens from possessing or raising them.

Luckily, most baby animals that seem alone actually have a mom that is not far away, either looking for food to feed herself and her babies or simply hiding from you. For example, rabbit mothers actively avoid their nests most of the time so as to not attract predators to the nest. Cottontail moms visit their babies only briefly at dawn and dusk for quick feedings. If you find a bunny nest, you can test to see if the mom is visiting by placing a few blades of grass or thin twigs in an X-shape over the babies. If you come back the next day and the pattern has been disturbed, then their mom is still caring for them and you should leave them be.

Many animal moms are prevented from taking care of their young when concerned people are hovering. Deer moms, for example, also actively avoid their babies (called fawns) so as to not attract predators to it. They generally return to nurse the fawns every few hours, but they won’t return to nurse if people or pets are around. If you find a fawn and it is not wandering and crying non-stop all day, then leave it alone so its mom will come back.

A red fox mom and baby. Photo by Nicke at Wikimedia.

Even if you find a baby all by itself in the open, the best course of action is often still to leave it alone. Many mammal moms, like squirrels, raccoons, mice, rats, foxes, and coyotes, will retrieve their young if they fall out of their nest or wander away from their den. Although it is a myth that most animal moms will abandon their babies if you get your smell on them, your odor can attract predators. It is best not to touch wildlife babies if you can avoid it.

Awww... as tempting as it is to pick up an adorable baby skunk, don't do it
unless you are a trained and licensed wildlife rehabilitator (like this woman is).
Image by AnimalPhotos at Wikimedia.

So when should you get involved? If an animal is in a dangerous location (like a busy street), then it may need to be moved. You can slowly, quietly and gently try to guide a mobile baby animal away from hazards and to a safer location. If the animal is not yet mobile, in most cases, you can use clean gloves to pick up the animal and move it to a safer location, placing it as close as possible to where you found it.

If you know that the mom is dead or has been relocated, then you are dealing with a truly orphaned baby animal. Likewise, if an animal has been attacked (or brought to you by your “helpful” cat), or is bleeding, injured, wet and emaciated, weak, infested with parasites, or has diarrhea, then it may need medical attention. In these cases, contact a licensed wildlife rehabilitator. Wildlife rehabilitators have been trained and have the necessary equipment to temporarily care for and treat injured, sick and orphaned wild animals so they can be released back into the wild. If you can’t find a wildlife rehabilitator, contact the Department of Natural Resources, a state wildlife agency, animal shelter, humane society, animal control agency, nature center, or veterinarian. Ideally, they will come to pick up the animal themselves. If they can’t, then they should give you detailed instructions for your situation on how to catch and transport the animal.

For more information, check here:

The Humane Society of the United States

The Wisconsin Department of Natural Resources

The Virginia Department of Game and Inland Fisheries

Tuesday, April 2, 2019

5 Animal Species With Surprising Memories

A repost of an original article from The Scorpion and the Frog.

We often think of animals as having hilariously short memories – the “memory of a goldfish”, if you will. But many animals have memories that can put yours to shame.

There are many different kinds of memory and each of them is controlled differently by different parts of the brain. Short-term memory can be thought of as the brain’s scratch pad: It holds a small amount of information for a short period of time while your brain decides whether it is worth retaining in long-term memory or if it can just fade away. When a short-term memory becomes a long-term memory, this process is called consolidation and involves physiological changes in the brain.

Long-term memory can be further divided into two main types: procedural memory and declarative memory. Procedural memory is used to remember how to do things and what objects are needed to do those things. Declarative memory is used for recall and can be further divided into memory used to recall facts (semantic memory) and events (episodic memory).Each of these different types of memories are stored in different parts of the brain. Furthermore, different types of facts (remembering faces versus numbers, for example) and different types of events (depending on if they have an emotional component or not, for example) are also stored in the brain differently. Because species differ in how we rely on our brains, it makes sense that this might be reflected in our abilities to remember in different ways.

So let’s check out some of the most amazing memories in the animal kingdom:

Do you know what all your kids and nieces and nephews are
doing right now? These elephants do. Photo by PJ KAPDostie
at Wikimedia.
1) They say an elephant never forgets. Elephants are very social animals that live in large stable herds. This has led to some incredible feats of social memory. They can keep track of the whereabouts of 30 group members at once and they can remember an animal they briefly met over 20 years ago. For an animal that lives about 50 or 60 years, this is very impressive. Elephants also have outstanding episodic memory: In 1993, Tarangire National Park in Tanzania suffered the worst drought that it had seen in 35 years. It was so severe that it killed 20% of elephant calves, compared to the average loss of about 2%. Of three herds that lived in the park in 1993, two of them were led by females that had lived during the severe droughts of 1958-61 and those herds left the park and were more successful at finding food and water. The herd that stayed was led by a younger female that had never experienced such a severe drought and that herd suffered 63% of the total mortality.

Dolphins never forget a name. Photo from the
NOAA Photo Library available at Wikimedia.
2) Bottlenose dolphins have even more incredible social memories. They, like elephants, live in complex social groups. Each dolphin has a unique whistle that it uses like a name. When they are played recordings of whistles of companions they lived with years or even decades earlier, they approach the speakers for longer than when they are played the whistles of dolphins they never met. The fact that they, like elephants, remember companions for over 20 years is much more impressive because their lifespan is only 40-50 years!

Sea lions can remember
meaningless tricks for years.
Photo by LSA2886 at Wikimedia.
3) Sea lions have amazing procedural memory. In 1991, marine biologists at the University of California, Santa Cruz, taught a California sea lion named Rio a card trick. They held up one card with a letter or number on it and another set of two cards: one that matched the first card and one that did not. Rio learned to pick the matching card to be rewarded with a fish. Everyone was impressed and she didn't do the trick again... until 10 years later, when researchers pulled out the cards and asked her to do it again. Rio had the same score in 2001 with no practice that she did in 1991 when she originally learned the trick!







Clark's nutcrackers can remember where they stashed
30,000 pine nuts.I can't even keep track of my keys.
Photo by Gunnsteinn Jonsson at Wikimedia.
4) Clark’s nutcrackers can remember the exact location of 30,000 pine nuts. This kind of superhero ability is born out of necessity: nutcrackers completely rely on their caches of food to get them through the winter. However, despite their amazing long-term spatial memory, their short-term memory is below average: they can’t even remember the color of a light for 30 seconds.

5) Chimpanzees can put your working memory to shame. Working memory is a form of short-term memory that is applied to a task. A group of researchers taught chimpanzees to do a task in which they were shown the numbers from 1-9 in random locations on a computer screen. When the numbers are covered, chimps can remember where each number was. Furthermore, they only need to see these randomly placed number for a few seconds to get this task correct. In comparison, only people that are considered savants have comparable abilities.



Tuesday, March 26, 2019

Interrupting Insects

A reposting of an original article from The Scorpion and the Frog.

What do you think of when I say “communicate”? Most likely, you are imagining people communicating by an auditory mode (talking and listening, making expressive sounds) or by a visual mode (observing body language, reading and writing). As a species, humans inherently rely heavily on our hearing and vision to perceive the world around us and so it makes sense that we communicate with one another using these modalities. But animal species are incredibly diverse in their means of perceiving their worlds and their modes of communication. Because we have been so focused on studying animal signals that we can perceive, we have only recently begun to more actively explore animal communication in these other modes. One of these modes is soundless surface vibrations.

The photo is of an adult Tylopelta gibbera on a host plant stem
(photo (c) Rex Cocroft).
Despite the fact that we do not perceive most animal surface vibration signals around us, vibrational communication is very common, especially among insects and spiders. Rex Cocroft at the University of Missouri at Columbia and Rafa Rodríguez at the University of Wisconsin at Milwaukee point out in a review of vibrational communication that over 195,000 species of insects communicate using soundless surface vibrations. We can experience many of these substrate vibration signals by broadcasting them through a speaker as an airborne vibration (which we perceive as sound).

Vibrational signals serve a number of functions in the insect worlds. Social insects, like ants, termites, and bees, often use vibrational signals to coordinate foraging. Groups of juvenile thornbug treehoppers vibrate when a predator approaches, calling in the mother to defend them. Males of many species have been found to use vibrational signals to attract females and the females often use these signals to choose a mate.

Vibrational signals are carried through a solid substrate, so they can only travel as far as the substrate is continuous and they are affected by attributes of the substrate (like changes in density). Because of these constraints, most vibrational signals can only travel about the length of a human arm. Many insects that use vibrational communication live on host plants, and it is these host plants that transmit the vibration signals. These animals face many challenges in transmitting their signals to the intended recipient. For example, wind, rain, and environmental sounds can create competing vibrations (background noise). In addition to environmental background noise, the vibrational soundscape of a given plant stem will likely include many signaling individuals, often of many species. Not only are there difficulties in getting your signal to your intended audience, but there are also risks of eavesdropping predators and competitors.

Frédéric Legendre, Peter Marting and Rex Cocroft at the University of Missouri at Columbia, demonstrate the social complexities of vibrational communication in a new study of competitive signaling in a treehopper species, Tylopelta gibbera. Tylopelta gibbera is a small treehopper in the southern United States, Mexico and Guatemala, that only lives on plants from the Desmodium genus. Males will attract and court females with vibrational signals and interested females will respond to the male with vibrational signals of their own. However, many individuals can often be found on a single plant and if two signaling males are present, the receptive female will typically respond to both of them and only mate with one (generally the first one she encounters). What is a competing male to do?

Listen to a male Tylopelta gibbera advertisement signal here.


The researchers performed a series of experiments, in which they observed treehoppers on potted host plants in the lab. With this set-up, they could control the environmental conditions, decide the number of males and females on the plant, record vibrational signals and play them back. They found that once a male signals and detects a female response, he will actively search for her along the plant, alternating signals and steps in a “Marco Polo” mating game until he finds her. Males found the females almost twice as fast if they were the only male on the plant, indicating that the presence of a second male on the plant somehow interferes with their ability to locate the female. Also, when two males were on the plant, they produced a new signal type that was never produced by a lone male on a plant. Males that had no male competition only produced signals that had a whine sound, followed by a series of pulses (and the female would then immediately respond with a harmonic sound of her own). This male signal is called the advertisement signal. Males that had a competing male on the plant would produce an additional signal that was a short tonal note. Interestingly, these males often produced this second signal at the same time that their competitor was advertising himself. Hmmm… could this be a masking signal used to interrupt the competitor? How could you figure that out?

This figure from Legendre, Marting and Cocroft's 2012 Animal Behaviour paper shows
the whine and pulses of a male advertisement signal (top) and a histogram of when the
masking signal occurs in relation to the timing of the advertisement signal (bottom).
First, the researchers asked, “When do males produce this second signal?” The researchers put two males on a plant with one female and recorded their vibrations. They found that in this situation, males typically produced this second signal while his competitor was just beginning the pulse section of his advertisement signal. Next, the researchers played back recordings of male advertisement signals followed by female responses to a lone male on a plant. All of the males tested produced the masking signal during the pulse section of the male advertisement signal on the recording.

Don't you hate it when someone does this?

Next, the researchers asked, “How do females respond to this second signal?” On plants with one female and two males, females didn’t respond as much to advertisement signals overlapped by a second signal as they did to advertisement signals alone. The researchers then played recordings of male advertisement signals to lone females on the plants. Females responded significantly more often if the advertisement signal was not overlapped by a masking signal.

So, male treehoppers get an edge up on getting the girl by interrupting the other competing males. Sneaky buggers!

Want to know more? Check these out:


1. COCROFT, R., & RODRÍGUEZ, R. (2005). The Behavioral Ecology of Insect Vibrational Communication BioScience, 55 (4) DOI: 10.1641/0006-3568(2005)055[0323:TBEOIV]2.0.CO;2

2. Legendre, F., Marting, P., & Cocroft, R. (2012). Competitive masking of vibrational signals during mate searching in a treehopper Animal Behaviour, 83 (2), 361-368 DOI: 10.1016/j.anbehav.2011.11.003


3. A Japanese research team has harnessed this phenomenon to create a remote-control that makes annoying people stop talking. Find out more at the blog Gaines on Brains!

Tuesday, March 12, 2019

Reduce Stress with this Animal Behavior Meditation

A reposting of an original article from The Scorpion and the Frog.

In a search for the promised inner peace and tranquility of meditation, I attended a meditation class at a local yoga studio. In a room with dim fluorescent lights and an artificial wood floor I laid on my back on my yoga mat, sandwiched between a fidgety woman who kept her smartphone on the edge of her mat and a man whose stress had apparently resulted in a flatulence problem. I was told to close my eyes, breathe deeply, and think about nothing. I closed my eyes, took a deep breath, and thought: “How do I think about nothing?” I thought about black. “Does black count as nothing? Wondering if I’m thinking about nothing is definitely not nothing. Am I doing this wrong? Is this going to work? If this isn’t going to work, I’m just wasting my time. I could be working through my to-do list right now. Oh! I forgot to put laundry on my to-do list. Oh, right… think about nothing. Black?

This ring-tailed lemur has found her inner peace - Can you find yours?
Photo by Margaret at Wikimedia Commons

It was years later that I realized that meditation doesn’t have to be so painfully contrived. I do it all the time naturally. Maybe you do too. We just have to nurture those moments. Here’s one way to do it:

1) Go to a place where you have seen at least one animal in the recent past. Maybe you saw a squirrel or a songbird in that tree in your yard. Maybe you saw fish in the creek you pass over on your way to school. Maybe there’s an occupied spider web in the corner. Maybe you have a favorite spot at the local zoo or aquarium. Go there. Don’t worry if there is an animal there now or not.

2) Sit down in a comfortable position and take a deep breath. Look around and take in your surroundings. Feel the environmental conditions. Listen to the sounds around you. Wait and observe. If you’re quiet, they will come.

3) When an animal shows up, focus on it. If multiple animals show up, pick one to be your focal animal. Observe every possible detail of your focal animal: What does it look like? Does it have any markings? What is it doing? How does it position itself with respect to its surroundings? What is its posture? How does it respond to changes in its surroundings?

4) Allow your mind to wander into your focal animal’s world (or umwelt). How do you think your focal animal perceives its surroundings?

5) Allow your mind to ponder explanations and consequences of your focal animal’s behavior.

6) Continue for as long as you can keep your mind focused on your animal, or until you have somewhere else you are supposed to be.

Try this out for yourself, and then let us know what you experienced!

Tuesday, March 5, 2019

Hey Hey! We’re The Monkeys!

 Updated and reposted from March 6, 2013.

A tamarin rock star
(photographed by Ltshears at Wikimedia)
Our moods change when we hear music, but not all music affects us the same way. Slow, soft, higher-pitched, melodic songs soothe us; upbeat classical music makes us more alert and active; and fast, harsh, lower-pitched, dissonant music can rev us up and stress us out. Why would certain sounds affect us in specific emotional ways? One possibility is because of an overlap between how we perceive music and how we perceive human voice. Across human languages, people talk to their babies in slower, softer, higher-pitched voices than they speak to adults. And when we’re angry, we belt out low-pitched growly tones. The specific vocal attributes that we use in different emotional contexts are specific to our species… So what makes us so egocentric to think that other species might respond to our music in the same ways that we do?

A serene tamarin ponders where he placed
his smoking jacket (photographed by
Michael Gäbler at Wikimedia)
Chuck Snowdon, a psychologist and animal behaviorist at the University of Wisconsin in Madison, and David Teie, a musician at the University of Maryland in College Park, teamed up to ask whether animals might respond more strongly to music if it were made specifically for them.

Cotton-top tamarins are squirrel-sized monkeys from northern Colombia that are highly social and vocal. As in humans (and pretty much every other vocalizing species studied), they tend to make higher-pitched tonal sounds when in friendly states and lower-pitched growly sounds when in aggressive states. But tamarin vocalizations have different tempos and pitch ranges than our tempos and pitch ranges.

Chuck and David musically analyzed recorded tamarin calls to determine the common attributes of the sounds they make when they are feeling friendly or when they are aggressive or fearful. Then they composed music based on these attributes, essentially creating tamarin happy-music and tamarin death metal. They also composed original music based on human vocal attributes. They played 30-second clips of these different music types to pairs of tamarins and measured their behavior while the song was being played and for the first 5 minutes after it had finished. They compared these behavioral measures to the tamarins’ behavior during baseline periods (time periods not associated with the music sessions).

As the researchers had predicted, tamarins were much more affected by tamarin music than by human music. Happy tamarin music seemed to calm them, causing the tamarins to move less and eat and drink more in the 5 minutes after the music stopped. Compared to the happy tamarin music, the aggressive tamarin music seemed to stress them out, causing the tamarins to move more and show more anxious behaviors (like bristling their fur and peeing) after the music stopped.

The tamarins also showed lesser reactions to the human music. They showed less anxious behavior after the happy human music played and moved less after the aggressive human music played. So, human voice-based music also affected the tamarins to some degree, but not as strongly. This may be because there are some aspects of how we communicate emotions with our voice that are the same in tamarins.

Can you imagine what we could do with this idea of species-specific music? Well, David and Chuck did! They have since developed music for cats using similar techniques.

We often think of vocal signals conveying messages in particular sounds, like words and sentences. But calls seem to do much more than that, making the emotions and behaviors of those listening resemble the emotions of those calling.


Want to know more? Check these out:

Snowdon, C., & Teie, D. (2009). Affective responses in tamarins elicited by species-specific music Biology Letters, 6 (1), 30-32 DOI: 10.1098/rsbl.2009.0593

Snowdon, C., Teie, D. and Savage, M. (2015). Cats prefer species-appropriate music. Applied Animal Behaviour Science, 166, 106-111.

Tuesday, February 26, 2019

The Contagious Cancer (A Guest Post)

By Stephanie Stanton

The Tasmanian devil, perhaps more popularly known by its animated counterpart Taz in Warner Bros.’ “Looney Toons,” is a carnivorous marsupial native to Tasmania, an island off the southern coast of Australia. Similar to Taz, the Tasmanian devil lives a violent lifestyle. While a good portion of fights don’t go beyond screaming matches, sometimes (especially during the mating season) fights escalate to full-on biting matches. Unfortunately, it is this aggressive nature that has been linked to the alarming drop in Tasmanian devils’ numbers over the last decade. However, it is not violent wounds acquired during fights that are causing this rapid decline, but rather the Devil Facial Tumor Disease (DFTD), a contagious cancer.



DFTD is a transmissible cancer that operates as its own living entity- it is genetically distinct from its host and lives on its host’s face. Most of these tumors appear on their faces. Coincidentally, this also happens to be where a majority of open wounds are acquired in this species. Because of this, it is believed that DFTD is transferred through open wounds on the skin.

A healthy Tasmanian devil in all his glory. Photo by Chen Wu at Wikimedia Commons.

This cancer has been so successful in spreading throughout the population because of the devils’ small population size and low genetic diversity. Among the genes with low genetic diversity in the population is the Major Histocompatibility Complex (MHC), a collection of genes responsible for a strong immune response in vertebrates. Without a strong immune response, it is difficult to fight off serious threats such as DFTD. Unfortunately for the devils, the tumors growing on their faces do not even register on their limited immune system’s radar- so their bodies don’t even fight back! Because of this, DFTD is in most cases fatal within six to nine months of showing clinical symptoms.

A Tasmanian devil afflicted with DFTD. Photo courtesy of Menna Jones, available at Wikimedia Commons

Three Australian scientists by the names of Rodrigo Hamede, Hamish McCullum, and Menna Jones from the University of Tasmania and Griffith University recognized the alarming decline in the Tasmanian devil population and sought to find a way to better understand and control the spread of the disease. They looked at two separate populations over four seasons, collecting data once every three months by taking counts of bites on individual devils and tracking who got DFTD, when, and on what part of their bodies. They hypothesized that because the tumor was transmissible through open wounds, then the number of open wounds could be used as an early predictor for the onset of DFTD.

And they were right…although perhaps not in the ways they thought they would be. Contrary to what common sense would have everyone believe, devils with the least amount of facial wounds were the most likely to develop the fatal cancer. How could this be?

Simply put, it appears that the disease is getting transferred from devil to devil not because their bodies are exposed to a bite from an infected individual, but because devils are biting the tumors of infected individuals, thereby creating a direct path for the tumor to enter the new host.

The scientists argued that the devils that have the fewest open wounds were better at fighting and also the most aggressive (A side effect of the cancer? Perhaps.) Tasmanian devils are likely to have cuts or scrapes in their mouths because of their aggressive eating style, providing a port for the cancer cells to invade. It was because they were biting the tumors of the infected devils that they were contracting the disease, which also explains the higher occurrence of tumors in the mouth. Less aggressive devils accumulated more injuries to the face, but as long as the cancer cells did not come into contact with open wounds, their likelihood of contracting the disease was slim.

Rodrigo, Hamish and Menna hope that their results along with further research can help reduce the effects of the disease on the shrinking Tasmanian devil population by offering potential solutions to better control its spread. Exciting research published in 2016 is also already offering hope in keeping Taz and his furry counterparts alive for future generations to enjoy.


Want to know more? Check out the original article below:

Hamede, Rodrigo K., McCullum, H., Jones, M. (2013). “Biting injuries and transmission of Tasmanian Devil facial tumour disease. Journal of Animal Ecology. DOI: 10.1111/j.1365-2656.2012.02025.x.

Tuesday, February 19, 2019

One of These Sharks is Not Like the Others (A Guest Post)

By Emily Masterton

When you think of a shark, what usually comes to your mind? Big teeth and the beach, right? Well, that’s not how the Greenland shark likes to live at all. Like the name denotes, this shark prefers cold waters and depths that would kill most sharks and people. The Greenland shark is mostly restricted to the waters of the far North Atlantic Ocean and the Arctic Ocean, which range from 34 – 68 degrees Fahrenheit. The Greenland shark has also been recorded diving down to depths ranging from 0 – 4000 feet. To put that in perspective, that’s equal to 3.2 Empire State Buildings stacked on top of each other!

Picture of a Greenland shark in the Admiralty Inlet, Nunavut.
Image by Hemming 1952 at Wikimedia Commons.

The Greenland shark is able to survive in this harsh environment because of the shark's high levels of nitrogenous waste products (any metabolic waste product that contains nitrogen) in their tissues. The nitrogenous waste products that are found in the Greenland shark are urea and trimethylamine N-oxide (TMAO). These chemicals help the shark maintain their osmotic balance (the movement of water across cells) in this very salty environment. This osmotic balance is important for the body to function and keep water and salt in balance in the cells.

TMAO and urea act as a type of anti-freeze that keeps the cells from freezing and developing ice crystals. The TMAO and urea work by preventing ice crystals from forming in the shark’s cells. They work by lowering the freezing point of water in the cells and by binding to ice crystals and preventing them from forming or growing. This protects the cells from denaturing due to the extreme pressure from the depths the shark dives at. If there were no TMAO and urea in the shark, then ice crystals could form and break cell walls, which could result in tissue and organ damage, then death.

This figure shows how TMAO and urea bind to the shark's protein and keep ice crystals from growing and forming. This prevents the protein from denaturing and ultimately killing the shark. Image by Emily Masterton.

While these chemicals are great for the Greenland shark, they are bad news for anyone or thing who decides to eat them. TMAO and urea are very toxic. The Greenland shark has the most toxic skin among all sharks and even made it to the Guinness World Records in 2013 for this level of toxicity. If you were to eat the skin of a Greenland shark without preparing it right, you will have symptoms similar to being extremely drunk.

Greenland shark meat is eaten in Iceland in a dish called Hákarl. The shark’s meat must be prepared a certain way so that the TMAO and urea are no longer present in the meat. This is done by fermenting the meat and then drying it for 4-5 months. Once it has been dried and is ready to eat, it is often served in cubes on toothpicks in small servings.

Although these extreme conditions would kill any human being or another shark, the Greenland shark is able to survive and thrive in these conditions, thanks to the chemicals TMAO and urea. These chemicals keep ice crystals from forming in the cells of the shark and ultimately keep the shark alive. There are 465 species of sharks in the ocean, but only one can call the harsh North Atlantic Ocean and Arctic Ocean its home.


References
• Farrell, Anthony Peter, et al. Physiology of elasmobranch fishes: internal processes. Academic Press/Elsevier, 2016
• Strøksnes, Morten. “My Hunt for the 400-Year-Old Shark Whose Flesh Gets You High.” Vice, 30 June 2017
• O’Connor, M. R. “The Strange and Gruesome Story of the Greenland Shark, the Longest-Living Vertebrate on Earth.” The New Yorker, The New Yorker, 15 Feb. 2018
• “The Greenland Shark: An Icy Mystery.” Greenland Shark | Sharkopedia Sharkopedia
Polar Seas: Greenland Shark

Wednesday, February 13, 2019

A Snail’s Dart of Love (A Guest Post)

By Jenna Miskowic

Snails that shoot darts. Who would have thought? Turns out, snails have a lot of competition for mates. Females of some snail species have evolved ways to select which males they want to be the father of their eggs. One of these strategies is a female can mate with multiple males and store their sperm. The female can then “choose” which sperm she wants to fertilize her eggs. This affects how males compete for mates. Males want to make sure they are the father to the offspring because they want their genes to be passed on. So male snails have developed ways to increase their chances of paternity.

Euhadra quaesita gliding through foliage. Image by Angus Davison
and Satoshi Chiba posted at Wikimedia Commons.

Enter the dart-bearing land snail, Euhadra quaesita. Snails of this species are simultaneous hermaphrodites that use cross-fertilization. Simultaneous hermaphrodites are animals that have both female and male reproductive tissues and systems. Cross-fertilization means that the snails require a mate. So, when two dart-bearing land snails cross paths and decide they want to mate, they will take their love-dart and pierce it into their mating partner. Because the snails are simultaneous hermaphrodites, they both perform this behavior before exchanging their sperm.

Love darts are composed of a crystalline form of calcium carbonite, which is what sea shells are made of, called aragonite. They are very sharp and pointed so that they are able to pierce the other snail. The dart is covered with a secretion from its mucous glands. When the dart pierces into the other snail, mucus is transported from the dart’s glands into the pierced snail’s blood. This mucus helps increase the amount of sperm being stored in the recipient snail and increases the likelihood of the donor snail being the father to the offspring of the recipient snail. Researchers Kazuki Kimura, Kaito Shibuya, and Satoshi Chiba from Tohoku University in Japan hypothesized that the dart’s mucus would also reduce future matings and promote laying eggs, also called oviposition.

Drawing of Euhadra quaesita’s love-dart. Cross-section on the left and lateral view on the right.
Image by Joris M. Koene and Hinrich Schulenburg posted at Wikimedia Commons.

To test these hypotheses, the researchers conducted two separate experiments. The first experiment focused on the effects of dart shooting and future matings of the recipient snail. Individually, non-virgin adult snails were presented with a non-virgin or virgin adult for their initial mating. In this species, non-virgin adults shoot their darts and virgin snails do not shoot their darts while performing the mating behavior. Thus, the subjects paired with a non-virgin adult were pierced with their partner’s love-dart, and the subjects paired with a virgin adult were not pierced with their partner’s love-dart. Then the subjects were offered to mate again with an unfamiliar non-virgin snail with a high mating motivation caused by individual rearing. They recorded how long the snail subject went, in days, before mating again with another individual of the same species. The researchers found that the amount of time between matings was longer in pierced snails than in ones not pierced.

The second experiment focused on the effect of injected artificial mucus on future matings and promotion of oviposition behavior. Researchers dissected an extract of the mucous glands out of adult snails and combined it with saline solution to create the artificial mucus. There were two groups used in this experiment: (1) adult snails injected with the artificial mucus, also known as the treatment group and (2) adult snails injected with only the saline solution, also known as the control group. They recorded the number of hatched eggs and their parentage. They found that artificial mucus-injected snail pairs mated less often than the control pairs. Additionally, they found that the amount of the snails that laid eggs was larger in the snails injected with artificial mucus. These findings support the researchers’ hypotheses that dart mucus can subdue future matings in its recipients.

So what are the benefits to stabbing your partner with a love dart? Well, if an animal has multiple partners, then it is quite advantageous for the partner to make sure that they are the parent. Mating suppression after being injected with the love dart is one way to fight off the competition. So, beware to all who search for Cupid’s arrow this Valentine’s Day. There may be more to an arrow of love than you realize.


References

Kimura, Shibuya, & Chiba. (2013). The mucus of a land snail love-dart suppresses subsequent matings in darted individuals. Animal Behaviour, 85(3), 631-635.

Tuesday, January 29, 2019

Why You Can’t Hibernate the Winter Away

A reposting of an original article from January, 2015.

You open your eyes, slap the alarm, and pull the covers a little tighter around your shoulders. It’s still dark outside and you dread the moment that you step out from under the warm comforter and the cold sucks your breath out. Can’t you just hibernate and sleep the winter away?

A dormouse in his snuggly hibernation state.
Image by Krysztof Dreszer at Wikimedia.
Actually, no. Hibernation and sleep are two completely different physiological processes (shown by studies of brain function). And chances are, you don’t have the physiological bits needed to hibernate safely.

Hibernation has more to do with energy and body temperature than it does with sleep. Hibernation is defined as a process in which an animal allows its body temperature to approximate the environmental temperature for several days or longer. It is a strategy that some animals use during periods of food shortage to conserve the energy that would normally be used to generate body heat. When food is scarce in the winter, the animal will lower its metabolism (the burning of food molecules to create energy and heat), which will result in the animal having less energy (and entering a sleep-like state) and less heat (until the body approaches the environmental temperature). So really, hibernation is the reduction of metabolism when food is scarce. Lack of activity and cold body temperatures are just the by-products.

Almost all species that hibernate are small mammals, including some hamsters, dormice, jumping mice, ground squirrels, marmots, woodchucks, bats, marsupials and monotremes. Bears, common examples of hibernating species, are actually debated by scientists as to whether they should even be considered hibernators due to the fact that their metabolisms and body temperatures do not decline as much as those of other hibernating species. The only bird species known to hibernate is the poorwill.

Each hibernating species has a specific range of body temperatures that their body can endure. Their first line of defense is to find a hibernaculum (a chamber or cavity in which to hibernate that is more insulated than the exposed environment). If the hibernaculum becomes so cold that the animal’s body temperature drops below its minimum endured range, it will either increase its metabolism slightly to raise its body temperature or it will arouse (wake up). Arousal is the process of increasing metabolic heat production to near-normal levels. All hibernating species seem to undergo multiple periods of temporary arousals during hibernation and scientists are still unsure why. Increasing the metabolism and body temperature from lower levels is an energetically costly process (similar to how your car uses more gas to accelerate than to maintain a higher speed). In most hibernating species, the process of increasing the metabolism uses a specialized tissue called brown fat.

Fat cells come in two main types: white fat and brown fat. White fat, the squishy stuff that we constantly try to diet and exercise away, is filled with lipids (fats) that we store to generate energy in the future. Brown fat cells also contains lipids, but they are specialized to break them down faster. Brown fat is found in newborn mammals and adult hibernators and is commonly located on the upper back, neck, chest and belly (like a vest) and around major arteries. Brown fat cells have lots of mitochondria (the metabolic parts of the cell that break down food molecules like lipids to generate energy). Brown fat mitochondria is specialized in that they have a protein called uncoupling protein 1 that causes them to generate heat rather than energy when they break down lipids. When the body becomes stressed, it releases norepinephrine, a stress hormone, which causes brown fat cells to increase the rate at which they break down lipids to generate heat. This heat warms the major arteries and increases blood flow, which then distributes the heat throughout the body.

A PET scan shows brown fat in a human.
Image by Hellerhoff at Wikimedia.
Although humans are born with a fair amount of brown fat, we lose it as we age. More specifically, it converts to white fat. We used to think that we lost it completely, but in recent years we have learned that some lean adults maintain a few pockets of brown fat in their necks and chests that obese people are more likely to lose. Researchers are currently exploring if and how we can convert some of our adult white fat to brown fat in order to increase our metabolisms and potentially combat obesity and diabetes.

So for now, we can’t hibernate the winter away. But continuing research into hibernating animals may hold an important secret to our own health.

Tuesday, January 22, 2019

Nature Shapes Faithful and Unfaithful Brains

A reposting of an original article from January 22, 2017.

Among monogamous animals, some individuals are more faithful than others. Could these differences in fidelity be, in part, because of differences in our brains? And if so, why does this diversity in brain and behavior exist?

A snuggly prairie vole family. Photo from theNerdPatrol at Wikimedia Commons.

Prairie voles are small North American rodents that form monogamous pair bonds, share parental duties, and defend their homes. Although prairie voles form monogamous pairs, that does not mean they are sexually exclusive. About a quarter of prairie vole pups are conceived outside of their parents’ union.

Not all male prairie voles cheat on their partners at the same rates. In fact, some males are very sexually faithful. It turns out, there are both costs and benefits to being faithful and to cheating. Mariam Okhovat, Alejandro Berrio, Gerard Wallace, and Steve Phelps from the University of Texas at Austin, and Alex Ophir from Cornell University used radio-telemetry to track male prairie voles for several weeks to explore what some of these costs and benefits might be. Compared to males that only sired offspring with their own partner, unfaithful males had larger home ranges, intruded on more territories of other individuals, and encountered females more often. However, these unfaithful males were also more likely to be cheated on when they were away (probably because they were away more). I guess even rodents live by The Golden Rule.

Maps of how paired male voles in this study used space. The solid red/orange/yellow peaks show where a faithful male (in the left map) and unfaithful male (in the right map) spent their time in relation to where other paired males spent their time (showed by open blue peaks). Image from the Okhovat et al. Science paper (2015).

Vasopressin is a hormone that has been found to affect social behaviors such as aggression and pair bonding when it acts in the brain. Mariam, Alejandro, Gerard, Alex, and Steve all set out to determine how vasopressin in the brain may relate to sexual fidelity in prairie voles. They found that faithful males had lots of a particular type of vasopressin receptor (called V1aR) in certain brain areas involved in spatial memory. Surprisingly, faithful males did not have more V1aR in brain regions typically associated with pair bonding and aggression. A male that has more V1aR in spatial memory regions might better remember where his own mate is and where other males have been aggressive, which would decrease the chances that he would intrude on other territories in search of other females and increase the time that he spends home with his own mate. A male that has less V1aR in spatial memory regions might be less likely to learn from his negative experiences and more likely to sleep around.

Photos of a brain section from a faithful male (left) and unfaithful male (right). The dark shading shows the density of V1aR vasopressin receptors. The arrows show the location of the retrosplenial cortex (RSC), a brain area involved in spatial memory. Faithful males had significantly more V1aR receptors in the RSC compared to unfaithful males. Image from the Okhovat et al. Science paper (2015).

The research team then found genotype variations that related to having lots or not much V1aR in one of these spatial memory regions (called retrosplenial cortex … but we’ll just call it RSC). They confirmed these findings with a breeding study, in which they reared siblings that were genetically similar, but some had the genotype they predicted would result in lots of V1aR in RSC and some had the genotype they predicted would result in very little V1aR in RSC. They confirmed that these genetic variations correspond with the amount of vasopressin receptor in this specific spatial memory area.

The researchers then looked closer at the different versions of this vasopressin receptor gene in the RSC brain region to see if differences in the amount of vasopressin receptors in RSC may be caused by the epigenetic state of the gene (i.e. how active the gene is). They found that the genotype that results in very little V1aR in RSC had many more potential methylation sites, which can repress gene activity.

All of this data together tells a very interesting story. Male prairie voles that have the genotype for more V1aR vasopressin receptors in their RSC part of their brain are more likely to remember where their home and mate are and to remember where other aggressive prairie voles are, which will make them more likely to spend more time with their partner, to be sexually faithful and to have sexually faithful partners. Male prairie voles that have the genotype for less V1aR in their RSC are more likely to forget where their home and mate are and where other aggressive prairie voles are, which will make them more likely to cheat and to be cheated on. Overall, faithful and unfaithful male prairie voles have roughly the same number of offspring, but advantages may emerge with changes in population density. Prairie vole populations vary anywhere from 25 to 600 voles per hectare from year to year. When population densities are high, you (and your partner) are more likely to encounter more potential mates and it may benefit you to cheat (and have a “cheater’s brain”). When population densities are low, you (and your partner) are less likely to encounter more potential mates and it may benefit you to be faithful (and have a “faithful brain”). But when populations fluctuate between high and low densities, both faithful and unfaithful genotypes will get passed along from generation to generation.


Want to know more? Check this out:

Okhovat, M., Berrio, A., Wallace, G., Ophir, A., & Phelps, S. (2015). Sexual fidelity trade-offs promote regulatory variation in the prairie vole brain Science, 350 (6266), 1371-1374 DOI: 10.1126/science.aac5791