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

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.

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.

Caught in My Web: We Are Primates

Image by Luc Viatour at Wikimedia Commons

If the news cycle these days has you wondering about our own humanity, take a moment to reflect on our primate nature. For this edition of Caught in My Web, let's explore primate behavior in the news.

1. Elizabeth Preston at Discover writes about lemur "stink flirting" in High-Ranking Male Primates Keep Wafting Their Sex Stink at Females, Who Hate It.

2. Janelle Weaver discusses how primates grant favors for their own social benefit at Nature in Monkeys Go Out on a Limb to Show Gratitude.

3. Roxanne Khamsi at NewScientist reports that Envious Monkeys Can Spot a Fair Deal.

4. Writing for The Verge, Angela Chen explains how we discovered that bonobos prefer to befriend bullies in For Bonobos, Nice Guys Finish Last.

5. In Those Lying Apes, Dale Peterson of Psychology Today discusses chimpanzee deception.

Sound familiar?

Mind-Manipulating Slave-Making Ants!

A reposting of an article from October 10, 2012.

An entire colony enslaved by an alien species to care for their young. Slave rebellions quelled by mind manipulation. It sounds like science fiction, right? But it really happens!

Myrmoxenus ravouxi (called M. ravouxi for “short”) is a slave-making ant species in which the queen probably wears a chemical mask, matching the scent of a host species in order to invade their nest without detection. Once inside, she lays her eggs for the host species workers to care for. Armies of M. ravouxi workers then raid these host colonies to steel their brood to become future slave-laborers to serve the needs of the M. ravouxi colony.

A M. ravouxi queen throttling a host queen. Photo by Olivier Delattre.

Enslaved worker ants could rebel: They could destroy the parasite brood or at least not do a good job caring for them. But to selectively harm the parasite brood without harming their own nests’ brood, the host ants would have to be able to tell them apart. Ants learn the smell of their colony in their youth, so any ants born to an already-parasitized colony would likely not be able to tell apart parasite ants from their own species. But what about ants that were born to colonies before they were invaded?

Olivier Delattre, Nicolas Châline, Stéphane Chameron, Emmanuel Lecoutey, and Pierre Jaisson from the Laboratory of Experimental Ethology in France figured that compared to ant species that were never hosts to M. ravouxi colonies, ant species that were commonly hosts of M. ravouxi colonies would be better able to discriminate their own species’ brood from M. ravouxi brood. Host species may even be better at discriminating in general.

The researchers collected ant colonies from near Fontainebleau and Montpellier in France. They collected M. ravouxi colonies and colonies of a species that they commonly parasitize (but were not parasitized at the time): Temnothorax unifasciatus (called T. unifasciatus for “short”). The researchers also collected T. unifasciatus that were parasitized by M. ravouxi at the time. Additionally, they collected colonies of T. nylanderi and T. parvulus, two species that are never parasitized by M. ravouxi. (Sorry guys. All these species go by their scientific names. But really, that just makes them sound all the more mysterious, right?). The researchers took all their ant colonies back to the lab and housed them in specialized plastic boxes (i.e. scientific ant-farms).

On the day of the tests, the scientists removed a single pupa (kind of like an ant-toddler) from one nest and placed it into a different nest of the same species or back in its own nest. They did this for colonies of both non-host species and for colonies of host species T. unifasciatus that were not parasitized at the time. Then they counted how many times the workers bit the pupa (an aggressive behavior) or groomed the pupa (a caring behavior).

Workers from all three species bit the pupa that was not from their colony more than they bit their own colony’s pupa. But the T. unifasciatus (the host species) were even more aggressive to foreign pupa than the other species. And only the T. unifasciatus withheld grooming from the pupa that was not from their colony compared to the one that was from their colony. Although all three species seemed to be able to tell the difference between a pupa from their own nest versus one from another nest, only the species that is regularly enslaved by M. ravouxi decreased care to foreign young. So that is what these ants do when they are not enslaved. How do you think enslaved ants respond to their own species’ young compared to M. ravouxi young?

A 1975 cover of Galaxie/Bis, a French science
fiction magazine, by Philippe Legendre-Kvater.
Image from Wikimedia.

The researchers repeated the study using enslaved T. unifasciatus, placing either a pupa of their own species from a different nest or a M. ravouxi pupa in with their brood. Even though prior to M. ravouxi takeover the T. unifasciatus bit foreign pupa more than their own, after M. ravouxi takeover they didn’t bite foreign pupa of their own species or M. ravouxi pupa very much. Not only that, but they groomed the M. ravouxi pupa more than the pupa of their own species! Ah hah! Mind control!

This, my friends, is the kind of truth that science fiction is made from.

But how might this work? Ants born to an enslaved colony would be exposed to both their own odors and the M. ravouxi odors. Because ants learn the smell of their colony in the first few days after they emerge from their eggs, these enslaved ants would have a broader set of smells that they may perceive as being “within the family”. That would explain why the enslaved T. unifasciatus ants didn’t attack either the foreign-born T. unifasciatus or the M. ravouxi young, but it doesn’t explain why the enslaved ants provided more care to the M. ravouxi than they did to their own species. One possibility is that the M. ravouxi produce more or especially attractive odors to encourage the host workers to take care of them.

There is still more to learn about this system: How exactly may the M. ravouxi be hijacking the pheromonal systems of their host species? How are the host species protecting themselves from exploitation? I guess we’ll have to wait for the sequel.

Want to know more? Check this out:

Delattre, O., Chȃline, N., Chameron, S., Lecoutey, E., & Jaisson, P. (2012). Social parasite pressure affects brood discrimination of host species in Temnothorax ants Animal Behaviour, 84, 445-450 DOI: 10.1016/j.anbehav.2012.05.020

Fatal Attraction: Praying Mantises (A Guest Post)

By Britta Bibbo

We all know the character: an incredibly beautiful woman that seduces the rough-and-tumble action hero, only for him to later find himself chained up over a lava pit with sharks in it! …Or something like that. A “femme fatal” is the idea of a beautiful woman who leads men to their demise. None are more perfect for this role than the female praying mantis. Praying mantis females practice the art of deception through sexual cannibalism. It’s exactly how it sounds: the male is attracted to the female and tries to make some babies, but instead ends up being devoured. Sexual cannibalism hardly seems like a good strategy for keeping the mantis population up, but some argue it’s merely females taking advantage of every scrap of food they can find… even if it’s a loving male.

False garden mantis (Pseudomantis albofimbriata). Image by Donald Hobern from Wikimedia Commons.

When male mantises encounter a female in the wild they only have one thing on the brain, while a female may be more interested in self-preservation. If she hasn’t encountered food for a few days she will be VERY hungry and not all that interested in mating; in many species of mantises it is known that female mantises will eat males, even while having sex! So how do female mantises attract males?

For most insects, females are able to attract males with pheromones, chemicals released from an individual that affect other individuals of the same species. For instance, females can emit pheromones that will be telling of their age, reproductive status, and body condition. Males are able to detect pheromones from great distances and these pheromones play a role in allowing a male to determine how attractive a female could be. Before any sexy time can begin, females have to show that they are open to male advances. Showing a male you’ve never met before that you’re interested can be a difficult task- so females typically emit pheromones that are known as honest signals. These signals accurately convey female interest in mating, as well as her reproductive status, age, and body condition. Because the majority of females are being honest, males don’t have to think twice about their mate’s intentions. This is where female deception comes into play. If a female takes advantage of the lack of male wariness, she could end up with an easy meal. This deception by the females is what scientists know as the Femme Fatale hypothesis. This hypothesis explains that female mantises are naturally selected to deceive male mantises, and exploit them as food. This idea hasn’t had much backing evidence until Dr. Kate Barry of Macquarie University in Sydney, Australia sought to test this hypothesis with the false garden mantis (Pseudomantis albofimbriata).

After considering the test subjects and how the mantises communicate, Kate expected one of three possible outcomes:

1. There will be no pattern between female hunger and male attraction (if female false garden mantises are not femme fatales and false garden mantis pheromones do not communicate feeding-related information).

2. The well-fed females will attract the most males, while hungry females will attract the fewest males (if female false garden mantises are not femme fatales and females are always honest about their quality and willingness to mate).

3. The hungriest females will attract the most males, while well-fed females will still attract some males (if female false garden mantises are femme fatales and females are dishonest about their quality and willingness to mate when they are hungry).

To test her expectations, Kate gathered juvenile mantises that were close to their adult forms to have many male and female mantises that have no previous mating experience. Once the mantises were adults, females were given different feeding regimens to have a range of hunger. Categories included Good (well-fed), Medium (slightly less fed), Poor (hungry), and Very Poor (very, very hungry). Adult mantises were housed in a circular cage that separated each female individually around the edge, while the males were kept in the center.

Diagram of cage experiment was conducted in. Image by Britta Bibbo.

To allow the males to smell the female pheromones, researchers separated males by special walls that the males could not see through, but could still detect the pheromones given off by a female. The number of males on a female’s side of the cage was used to measure how attractive her pheromones were to the males.

The results of this study concluded that pheromones produced by the females that were very hungry were the most attractive to males. Through deception, the hungriest females are seen as sexier than well-fed, healthy females that are willing to mate! This result is surprising; normally females that are well-fed are seen as “sexier” because they have more nutrients available to them, making them more fertile. Hungry females have fewer nutrients available to them, making them less fertile, and therefore not as “sexy”. These hungry female mantises are advertising themselves as well-fed, fertile, and ready to rock when really, they’re not. Simply put, these results show that males are being catfished, and then consumed. Whether hungry females are actively trying to deceive males or if it’s just coincidental still needs to be looked into, but for now, be thankful for a partner who will see you as more than just a piece of meat!

Literature Cited:

Barry, K. (2014). Sexual deception in a cannibalistic mating system? Testing the Femme Fatale hypothesis Proceedings of the Royal Society B: Biological Sciences, 282 (1800), 20141428-20141428 DOI: 10.1098/rspb.2014.1428

Bottlenose Dolphins: The Ultimate Sea Bully? (A Guest Post)

By Kayla Fuller

Imagine this situation: you’ve brought your favorite lunch to work. Everyone is jealous of your food, continuously eyeing it up. A few coworkers, who have brought in disappointing lunches in comparison, approach and demand that you hand it over. After you refuse, they beat you until your body lies lifeless and they take your lunch anyway.

Woah, woah, woah… that took a dramatic turn!

Photo of a harbour porpoise, taken by AVampireTear (Wikimedia Commons)

But for harbour porpoises in the northeastern Atlantic, this fight for food has become a reality, and bottlenose dolphins are the suspected culprit. In 1996, Harry M. Ross (SAC Veterinary Services, U.K.) and Ben Wilson (University of Aberdeen, U.K.) documented fractured rib cages, damaged internal organs and joint dislocations of deceased harbour porpoises in the northeastern Atlantic. Why would bottlenose dolphins be causing such damage? Who could ever associate such a cute and cuddly creature with a horrific crime like this?

Photo of a bottlenose dolphin, taken by NASA (Wikimedia Commons)

Researchers Jérôme Spitz, Yann Rousseau, and Vincent Ridoux with the Center for Research on Marine Mammals: Institute for Coastal and Environmental Research at the University of La Rochelle in France become the judge and jury in this trial. Jérôme, Yann, and Vincent obtained 29 harbour porpoises and 25 bottlenose dolphins that had been beached and died in the Bay of Biscay (between Spain, France, and England). At the time of the study, more harbour porpoises were being found dead in the bay than in previous years. They hypothesized that bottlenose dolphins and harbour porpoises may have had similar enough diets to cause competition and violence between the two species.

Photo of a harbour porpoise that received injuries thought to be from a
bottlenose dolphin before death (circled), from Ross and Wilson (1996)

The researchers’ goal was to analyze stomach contents to directly see what each mammal was eating at the time of their death. To do this, Jérôme, Yann, and Vincent removed the stomachs from the harbour porpoise bodies and weighed them with all contents included. After weighing stomach casings separately, they calculated total weight inside of the animals’ stomachs. Then, they washed stomach contents through a filter to separate out larger matter. Now, if you have a weak stomach, this probably wouldn’t be the job for you. Jérôme, Yann, and Vincent separated food items within the stomachs into identifiable categories. It could sometimes be difficult to recognize whole animals in a stomach due to breakdown, so methods like pairing dismantled eyes or counting fish bones was necessary to identify them! This same process was repeated for bottlenose dolphin carcasses. From there, the scientists compared specimens for prey presence, abundance, mass, and size to see if there was overlap between diets of the harbour porpoises and bottlenose dolphins.

So what did they find? More food mass, a greater number of species, and a more diverse size range of prey was found in the stomachs of bottlenose dolphins in comparison to harbour porpoises. Although bottlenose dolphins have a habitat that includes more deep-ocean areas while harbor porpoises inhabit coastal surroundings, certain prey species were eaten by both. Since bottlenose dolphins are bigger and hunt in larger groups, they would logically be more dominant in a face-off over a common prey item. Why are they fighting more over the same foods? This shift could be a result of humans harvesting species from the ocean that are diet items for bottlenose dolphins. It could also be a result of warming ocean temperatures that could be changing the dwelling places of available food for bottlenose dolphins. This would explain why more habour porpoises are being attacked by these marine tyrants moving into shallower waters.

Poor porpoises, all they want to do is eat their lunch in peace. Who knows, maybe in the next few million years, we’ll see highly evolved harbour porpoises covered in spikes to ward off the dolphins. That’ll teach those bullies!


References:

Ross, H., & Wilson, B. (1996). Violent Interactions between Bottlenose Dolphins and Harbour Porpoises Proceedings of the Royal Society B: Biological Sciences, 263 (1368), 283-286 DOI: 10.1098/rspb.1996.0043

Spitz, J., Rousseau, Y., & Ridoux, V. (2006). Diet overlap between harbour porpoise and bottlenose dolphin: An argument in favour of interference competition for food? Estuarine, Coastal and Shelf Science, 70 (1-2), 259-270 DOI: 10.1016/j.ecss.2006.04.020

The Complexities of “The Love Hormone”

New York street art. Photo in
Wikimedia Commons posted by Pedroalmovar.

Oxytocin, commonly known as “the love hormone”, is a small chemical that is produced in the brain of mammals, but can both act as a neurotransmitter and enter the blood stream and act as a hormone. It has long been heralded for its role in both maternal and romantic love, but more recent research is showing us just how complicated the physiology of love can be.

Oxytocin is released in mammalian mothers after birth. It promotes nursing and bonding between a mother and her young. As children grow, oxytocin is involved in how both mothers and fathers “baby-talk” and mirror their children. It is involved in pro-social behaviors in both young and adults: trust, generosity, cooperation, hugging, and empathy. And of course, oxytocin promotes positive communication and pair bonding in romantic couples. Countless studies have found these relationships between affiliation and oxytocin in many mammalian species, giving oxytocin its commonly used nickname “the love hormone”.

But more recent studies show that it’s not so simple.

In a number of recent studies, people have been given oxytocin nasal sprays and tested for various behavioral effects in different contexts… and the context really seems to matter. Oxytocin increases trust, generosity, cooperation, and empathy towards people we already know and like. But it decreases trust, generosity, cooperation, and empathy towards strangers. When we play games with strangers, oxytocin makes us more jealous when we lose and it makes us gloat more when we win. It also seems to enhance many attributes relating to ethnocentrism: It increases our ability to read facially-expressed emotions in people of our own race while making it harder to read facial expressions of people of a different race. When forced to choose between being nice to a stranger of our own race versus a stranger of another race, oxytocin makes us more likely to choose the person of our own race. In studies of both people and rodents, oxytocin decreases aggression towards our families and friends, but increases aggression towards strangers.

Oxytocin is not the universal love hormone we once understood it to be. It helps us direct our positive support towards our “in-groups” (our family and friends) and defend them from our “out-groups” (individuals we don’t know). It is a delicate balance: Too little of it can cause social impairment and make it difficult to connect with loved-ones; Too much of it can increase our anxiety towards strangers and racist tendencies. And to make things more complicated, each of us has a slightly different oxytocin system: sex, gender, social history, history of childhood trauma or neglect, psychiatric illnesses and genetic variations all have profound effects on the oxytocin system.

There is much we don’t know about the role of oxytocin and love. But they are a good fit, because both, it seems, are complicated.


Want to know more? Check these out:

Shamay-Tsoory SG, & Abu-Akel A (2016). The Social Salience Hypothesis of Oxytocin. Biological psychiatry, 79 (3), 194-202 PMID: 26321019

Zik JB, & Roberts DL (2015). The many faces of oxytocin: implications for psychiatry. Psychiatry research, 226 (1), 31-7 PMID: 25619431

Are Territory Disputes Between Male Butterflies Influenced by Motivation?

By Nick Gremban

Male speckled wood butterflies will “perch” on leaves
and ends of twigs to look out over their territory for females.
 However, they have been known to be quite aggressive
with any intruding males! Photo by Alvesgaspar at
Wikimedia Commons, modified by Nick Gremban.

Think about any territorial animal. Now think about its aggressiveness while it is defending its territory. Was your animal a butterfly? No? You mean the colorful wings and the natural association with flowers doesn’t strike a fierce image of aggression in your mind? Well, the truth is some butterflies are very territorial and aggressive toward one another, contrary to what we expect.

Male butterflies do not have physical means to inflict harm to one another when it comes to territorial disputes. Instead, two or more males may stage “contests” with each other which often involve elaborate aerial chases. For example, a male that flies into the territory of another male will set off a pursuit by the resident male, resulting in both flying in circles around each other until one eventually gives up and is chased out of the territory. Normally, winners of the contests are the males that are able to endure the longest flights. An example of what these competitions look like can be seen from this video:

Researchers have been puzzled by what determines which male butterfly wins a contest. Some researchers have thought body size should determine who wins the contest. After all, isn’t being bigger always better? Turns out for many butterflies, it’s quite the opposite, with smaller butterflies of some species winning contests more. What about age? Shouldn’t the most experienced butterflies have better odds at winning? Again, the opposite is often true, with some studies finding younger males having better odds at winning competitions. How about motivation? Could some male butterflies be motivated by something that gets them revved up? Researchers from Stockholm University in Sweden seem to think so!

In a study conducted by Martin Bergman, Martin Olofsson, and Christer Wiklund from Stockholm University, male speckled wood butterflies were tested by observing the number of contest rematches won by males that were subject to a source of motivation: a female speckled wood butterfly. Females are a primary purpose to why males hold territories, so interactions with them before a contest was thought to serve as motivation.

The researchers staged their experiment in a series of steps. The first step consisted of introduced contests between two male speckled wood butterflies over a territory, or in this experiment, a sunspot. In total, 60 pairs of males were used to conduct this experiment. Males that won five consecutive contests were considered “winners” and given the status of being the resident male over the sunspot. Afterwards, winners were temporarily removed from the sunspot they just previously won.

Get out of my sunspot! Photo by Martin Bergman.

All males that lost the contests were considered “losers” and were split in to two groups. The first group was allowed to interact with a female for 30 minutes. Males in the second group were placed alone in a cage for 30 minutes. Afterwards, each male was allowed back to the sunspot, now vacant of the winner. After each of the losing males took over the sunspot, therefore claiming themselves as the new resident male, the winners were then returned to the sunspot. The return of the winners allowed rematches of contests. Researchers recorded contest duration and if the males that lost the first round of contests won their rematches.

Loser males that had the chance to interact with a female won 53% of rematches while loser males placed alone only won 17% of rematches. In other words, males that interacted with a female endured longer flights to win their rematch. Furthermore, these same males were more likely to claim the vacant sunspot.

Male speckled wood butterflies
will “fight” over a female (such
as this one)…doesn’t this
concept sound familiar? Photo by
Mark Colvin at Wikimedia Commons.

Overall, the researchers suggested that the males which had interacted with a female had an increased motivation to fight harder on the rematch to win the sunspot. Just like with many other animals, male butterflies are willing to compete for the girl! The presence of a female may serve as a cue for the males that a particular territory is worth fighting for. After all, isn’t reproduction the name of the game?

Butterflies prove to be more mysterious and complex than we typically expect. Not only can they express territoriality without true physical means to harm each other, but they appear to be influenced by motivation! So, next time you see two butterflies fiercely circling each other in flight, you now know they mean serious business.


References

Bergman, M., Olofsson, M., & Wiklund, C. (2010). Contest outcome in a territorial butterfly: the role of motivation Proceedings of the Royal Society B: Biological Sciences, 277 (1696), 3027-3033 DOI: 10.1098/rspb.2010.0646

Steroids Won't Help if You're a Loser

The more we study physiology and behavior across groups of animals, the more we find we have in common in the types of behaviors we express and the biological machinery of how our bodies influence what behaviors are expressed and when. But similarity does not mean the same. Sometimes seemingly small physiological differences can have big behavioral consequences.

A snuggly California mouse pair. Photo from the Marler lab.

A loner white-footed mouse. Photo by the National Park Service.

Today I am thinking about a story of two very closely related and similar species of mice and how their personal experiences make all the difference in how testosterone affects them. Check it out here.

Song Battles With Other Species Can Change Your Tune

Many animals defend territories from members of their own species for mating, breeding, and finding food and they often use species-specific vocalizations to do this. Defending a territory can be risky and costly in both energy and time, so even territorial animals generally don’t waste this effort on other species that do not share their same food and breeding needs. But what do you do if you live around another very similar species that has the same needs that you do? Can two species learn to speak each other’s languages to live in territorial harmony?


A common nightingale.
Photo by Frebeck at Wikimedia Commons.

A thrush nightingale.
Photo by Locaguapa at Wikimedia Commons.

Today at Accumulating Glitches, I tell the story of two species of nightingales and how they are learning to sing each other's songs to defend their territories! Check out the article here.

Choosing Mates Wisely Is All The More Important When They Try To Eat You

A praying mantid pair.
Photo by Oliver Koemmerling
at Wikimedia Commons.

Choosing our mates is among the most important decisions of our lives. We agonize over finding "the one", and for good reason. If we are going to spend the rest of our lives with one person and depend on that person to help create and raise our children, the stakes of choosing that person well are high. But at least we don't have to worry that if we choose wrong our partner will bite our head off... not literally, anyway.

Today at Accumulating Glitches, I talk about sexual cannibalism in praying mantids and how it has led to males now choosing less aggressive mates. Check out the article here.

War and Peace



A group of Gelada baboons in Ethiopia.
Photo by A. Davey at Wikimedia Commons.

Syria and Iraq. Ukraine. The Gaza Strip. People are dying in large numbers at the hands of other humans, and for what? Land and resources? Is it really worth it? It is often said that humans are the only species so horrific as to kill its own species in war. But the fact is, we are not alone in what was previously thought to be a uniquely human trait. In many animal groups, individuals will band together in collective defense of territory and resources.

This week at Accumulating Glitches I talk about how group size influences the ability of primate groups to hold their territories. Check it out here.

And to learn more, check this out:

Willems, E.P. Hellriegel, B. and van Schaik, C.P. The collective action problem in primate territory economics, Proceedings of the Royal Society B, 280: 20130081 (2013). DOI: 10.1098/rspb.2013.0081.

Is That Lizard Possessed!? (A Guest Post)

By Tawny Liebe

Image from Chuck Heston on Flickr.

A creature straight from the depths of hell… or at least as close as you can get on this planet. The Texas horned lizard or “horny toad” is found in the deserts of the southwest United States and has an unusual adaptation to deter predation exclusively from a few species of canines. When threatened by coyotes, foxes, and dogs, the horned lizard squirts blood from its eyes to hit targets up to three feet away! A total of six species of horned lizard have been proven to respond this way to canine attack, while none have responded this way to other predators, such as the grasshopper mouse or the roadrunner. So what is the deal? How do they do this and how does it work as predator defense?


Veins have one-way valves
to prevent backflow.
Drawing by Tawny Liebe.

Before we get to that, there are a few things you need to know. First of all, the circulatory system includes a network of arteries and veins. Arteries carry blood full of oxygen to body tissues while veins carry blood that lacks oxygen from the rest of the body back to the heart. This means that for the blood, in someone’s foot for instance, to get all the way back to the heart through the veins, the blood must work against gravity. When you (or this lizard or many other species) move, blood is propelled from one chamber in the vein to the next until it reaches the heart. The blood is prevented from flowing back into the previous chamber by one-way valves, causing the blood to pool.

In order to squirt blood from their eyes, horned lizards manipulate the network of veins in their head so that they build up pressure, like a volcano getting ready to blow. By constricting a pair of throat muscles unique to reptiles, they effectively close their jugular veins and increase the blood pressure in their head. This is thought to be enhanced by another pair of muscles between the jugular veins and the eyes that help increase the blood pressure in the head even further, causing the blood to move into the sinuses of the eyes. The pressure continues to build until the blood breaks through the wall of the eye socket into the eyelids where it is forced into the tear duct and erupts like a Mentos in a Coke bottle all over whatever is chomping at the poor little lizard.

As if these lizards couldn’t get any more amazing, recent studies have shown that it is actually a compound in their blood that canines don’t like. Scientists have also found that this chemical is in their circulating blood, not just the blood that is squirted from their eye, rejecting an earlier hypothesis that the chemical is picked up in the tear duct. To top off all of this awesomeness, the chemical may be acquired through its main food source- harvester ants, which are venomous. These ants aren’t actually a requirement of the horned lizard’s diet and yet they are specialized to eat them. The horned lizard’s blood plasma binds to the venom, which neutralizes its toxicity and the resulting compound may be what deters these canines.

Now that we know how horned lizards are capable of this type of defense and how they most likely make their blood so undesirable, what is it about this chemical that is so appalling to these predators? It appears that the target area of the blood is the mouth since the horned lizard only squirts the blood when the canine begins to bite down on its head. This suggests that it may be the taste of the blood that prevents the horned lizard from becoming that coyote’s tasty snack.

The horned lizard’s ability to squirt blood at canines to prevent their untimely death is truly amazing and complex and there is still much to learn about it. Their ability makes me wonder how many other cool anti-predator adaptations there are out there in the animal and even the plant kingdom! Below is a video that will allow you to appreciate the full effect of this awesome defense strategy, enjoy!

References:

Heath, J.E. 1966. Venous shunts in the cephalic sinuses of horned lizards. Physiological Zoology 39(1): 30-35.Middendorf, G.A. and Sherbrooke, W.C. 1992. Canid elicitation of blood-squirting in a horned lizard (Phrynosoma cornutum). Copeia 1992(2): 519-527.

Middendorf, G.A. and Sherbrooke, W.C. 1992. Canid elicitation of blood-squirting in a horned lizard (Phrynosoma cornutum). Copeia 1992(2): 519-527.

Middendorf, G.A. et. al. 2001. Comparison of blood squirted from the circumorbital sinus and systemic blood in a horned lizard, Phyrnosoma cornutum. The Southwestern Naturalist 46(3): 384-387.

Middendorf, G.A. and Sherbrooke, W.C. 2004. Responses of kit foxes (Vulpes macrotis) to antipredator blood-squirting and blood of Texas horned lizards (Phrynosoma cornutum). Copeia 2004(3): 652-658.

Sherbrooke, W.C. 1992. Chiricahua Mountains Research Symposium. Horny “toad” tales from the Chiricahua mountains as, told by a biologist. Southwest Parks and Monuments Association, Tuscon, AZ. 78-80.

Personality and the Spread of Disease

This image was provided by the CDC and the Partnership, Inc.
Available at Wikimedia Commons.

Studies of the spread of infectious diseases have shown that behavior plays a strong role in which individuals are more likely to be infected and which ones aren't. For example, sexually transmitted diseases (STDs) are more commonly diagnosed in people that have more sexual partners. But despite our understanding of how diseases are spread among people, we know very little about the spread of diseases among wild animals. Do their personalities play a role in the spread of wildlife diseases?

This week at Accumulating Glitches I talk about personalities in deer mice and the role they play in the spread of hantavirus. Check it out here.

And to learn more, check this out:

Dizney L, & Dearing MD (2013). The role of behavioural heterogeneity on infection patterns: implications for pathogen transmission. Animal behaviour, 86 (5) PMID: 24319292