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!

Can Animals Sense Each Other’s Wants and Hopes?

A repost of an original article from November 13, 2013.

Is the ability to empathize uniquely human? This question has long been pondered by philosophers and animal behaviorists alike. Empathy depends in part on the ability to recognize the wants and hopes of others. A study by researchers at the University of Cambridge suggests that we may not be alone with this ability.

A male Eurasian jay feeds his female mate. Photo provided by Ljerka Ostojić.

Ljerka Ostojić, Rachael Shaw, Lucy Cheke, and Nicky Clayton conducted a series of studies on Eurasian jays to explore whether male jays could perceive changes in what their female partners desired. Eurasian jays are a good species with which to explore this phenomenon because males routinely provide food to their female mates as a part of their courtship. The researchers wanted to know if males would adjust what food items males offered their mates depending on what food type the females wanted more.

In order to make a female prefer one food type over another, the researchers fed each female one of two food types (wax moth larvae and mealworm larvae) until they were full. But being full of one type of food doesn’t mean you can’t find room for desert, right? So when the researchers then offered the females access to both wax moth larvae and mealworm larvae, those that had previously eaten wax moth larvae now preferred mealworm larvae and those that had previously eaten mealworm larvae now preferred wax moth larvae. But could their male partners tell what they preferred at that moment?

In order to test whether male jays were sensitive to their partners’ desires, the researchers fed the females either wax moth larvae or mealworm larvae until they were full. They did this while their male partners watched from behind a transparent screen. They then removed the screen and gave the males 20 opportunities to choose between a single wax moth larvae or mealworm larvae to feed their partner. In this context, males usually chose to share with their mates the food that their partners preferred rather than the food their partners had already been fed! But are the males responding to their mate’s behavior or are they responding to what they saw when the females were eating earlier?

This video (provided by Ljerka Ostojić) shows the experimental process
in which the male chooses a food type and then shares it with his mate.

The researchers repeated the study with an opaque screen so the males could not see their mates while the females gorged on one particular food type. Without the ability to see the mate eating beforehand, males chose both food types equally and did not attend to their mate’s preferences. Because the females still had a preference for the opposite food type but the males were not adjusting for that preference, this means that the males are not responding to their mate’s behavior in this experiment or the previous one. This suggests that if male Eurasian jays see what their mates are eating, then somehow they have the ability to know to give their mate the opposite food type!

Whether this process involves the males having an understanding of their mate’s desires or some other mechanism is not fully known. But male Eurasian jays are certainly adjusting what they give their mates according to what she wants. Now if we can only teach human males to do that!

Want to know more? Check this out:

Ostojić, L., Shaw, R.C., Cheke, L.G., & Clayton, N.S. (2013). Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays PNAS, 110 (10), 4123-4128 DOI: 10.1073/pnas.1209926110

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?

The Love Chemical Pageant of 2018

A modified repost of an original article from February 15, 2012.

Hello and welcome to the Love Chemical Pageant of 2018! I’m your host, Miss Behavior, and YOU are the judges.

Since the beginning of…well, social animals, many hormones and neurotransmitters have been quietly working in their own ways to fill our world with love. Lately (over the last few decades), some of them have been brought out of the background and into the limelight, credited with every crush, passionate longing, parental hug, embrace among friends, and cuddle between spouses. But who truly deserves the title of The Love Chemical?

Let’s meet our contestants!

Let’s first meet our reining title-holder, Dopamine! Dopamine is a neurotransmitter produced in the brain. Sex increases dopamine levels in both males and females and blocking its effects during sex can prevent prairie voles (a monogamous species often used to test questions on pair bonding) from forming preferences for their own partner. Dopamine also plays a role in maternal and paternal behaviors.

But dopamine is not just involved in love. It has a wide range of known functions in the brain, involved in everything from voluntary movement, mood, motivation, punishment and reward, cognition, memory, learning, aggression, pain perception and sleep. Abnormally high levels of dopamine have been linked to schizophrenia and psychosis. And dopamine is especially well-known for its role in addiction... in fact, many researchers believe that we may even be addicted to our own romantic partners.

Now let’s meet Dopamine’s partner, Opioids! When natural opioids are released in the brain, they can cause a rewarding feeling that often cause us to seek more of it. When prairie voles are given drugs that prevent opioids from acting on a particular opioid receptor type (mu-opioid receptors) in a particular brain region (the caudate-putamen), they do not form pair bonds with sexual partners. Interestingly, people that see the faces of their loved ones experience lots of activity in the caudate-putamen region of the brain, especially if they rate their relationship with that person as very romantic and passionate. The caudate-putamen region of the brain also uses dopamine, so the two chemicals appear to work together there to promote the feelings of romantic love.

Please welcome Oxytocin! Oxytocin is a peptide hormone, most of which is made in the brain. Some of this oxytocin is released into the blood and affects body organs, such as the uterus and cervix during child birth and the mammary glands during breast feeding. But some of it stays in the brain and spinal cord, acting on neurons with oxytocin receptors to affect a number of behaviors. Released during child birth and nursing, oxytocin is important for helping mammalian mothers behave like moms and in species in which both parents raise young, it helps fathers behave like dads. Also released during sex, oxytocin plays an important role in pair bonding in prairie voles (particularly in the female of the pair). In humans, people given oxytocin nasal sprays have been reported to have less fear, more financial trust in strangers, increased generosity, improved memory for faces, improved recognition of social cues, and increased empathy.

But before you fall head-over-heels for oxytocin, you should know a few more things. For one thing, oxytocin isn’t exclusively linked with feel-good emotions; It has also been associated with territoriality, aggressive defense of offspring, and forming racist associations. Also, oxytocin doesn’t work alone. It has been shown to interact with vasopressin, dopamine, adrenaline and corticosterone and all these interactions affect pair bonding.

Next up is Vasopressin! Vasopressin is closely related to oxytocin. Like oxytocin receptors, vasopressin receptors are expressed in different patterns in the brains of monogamous vole species compared to promiscuous vole species. Released during sex, vasopressin plays an important role in pair bonding in monogamous prairie voles (particularly in the male of the pair). If you block vasopressin in the brain of a paired male prairie vole, he will be more likely to prefer spending time around a new female rather than his mate. On the flip side, if you increase vasopressin activity in specific brain regions of an unpaired male prairie vole or even a promiscuous male meadow vole and introduce him to a female, he will prefer spending time with her than other females. Vasopressin may also make male prairie voles more paternal.

But vasopressin does a lot of things. In the body, its primary function is to regulate water retention. In the brain, it plays a role in memory formation and territorial aggression. And even its role in monogamy is not exclusive: Vasopressin interacts with oxytocin and testosterone when working to regulate pair bonding and parental behavior.

Look out for Cortisol! Cortisol is produced by the adrenal glands (on top of the kidneys) and is involved in stress responses in humans and primates. Both men and women have increased cortisol levels when they report that they have recently fallen in love. Many studies have also found relationships between cortisol and maternal behavior in primates, but sometimes they show that cortisol increases maternal behavior and sometimes it prevents it. In rodents, where corticosterone is similar to cortisol, the story is also not very clear. Corticosterone appears to be necessary for male prairie voles to form pair bonds and it plays a role in maintaining pair bonds and promoting paternal behavior. But in female prairie voles, the opposite seems to be true! Corticosterone in females appears to prevent preference for spending time with their partner and pair bond formation.

Put your hands together for Testosterone! Testosterone is a steroid hormone and is primarily secreted from the gonads (testes in males and ovaries in females). Frequently referred to as “the male hormone”, both males and females have it and use it, although maybe a little differently. Testosterone is associated with sex drive in both men and women. But men who have recently fallen in love have lower testosterone levels than do single males, whereas women who have recently fallen in love have higher testosterone than single gals.

This is Estrogen! Estrogen is another steroid hormone, frequently referred to as “the female hormone”, although again, both males and females have it. Estrogen also seems to play a role in sex drive in both men and women. The combination of high estrogen levels and dropping progesterone levels (another steroid hormone) is critical for the development of maternal behavior in primates, sheep and rodents. But look closer and you will find that the activation of estrogen receptors in particular brain regions is associated with less sexual receptivity, parental behavior, and the preference for spending time with the mate.

So let’s have a round of applause for this year’s contenders in The Love Chemical Pageant! Now it is your turn to voice your opinion in the comments section below. Vote for the neurochemical you believe deserves the title The Love Chemical. Or suggest an alternative pageant result!


Want to know more? Check these out:

Burkett, J.P. and Young, L.J. (2012). The behavioral, anatomical and pharmacological parallels between social attachment, love and addiction. Psychopharmacology, 224:1-26.

Fisher, H.E. (1998). Lust, attraction, and attachment in mammalian reproduction. Human Nature, 9(1) 23-52.

Marazziti, D. and Canale, D. (2004). Hormonal changes when falling in love. Psychoneuroendocrinology, 29, 931-936.

Van Anders, S.M. and Watson, N.V. (2006). Social neuroendocrinology: Effects of social contexts and behaviors on sex steroids in humans. Human Nature, 17(2), 212-237.

Young, K.A., Gobrogge, K.L., Liu, Y. and Wang, Z. (2011). The neurobiology of pair bonding: Insights from a socially monogamous rodent. Frontiers in Neuroendocrinology, 32(2011), 53-69.

Let’s Talk Turkey: 8 Surprising Facts About Turkeys

A reposting of an article from November 24, 2014.

A wild male turkey struts his stuff.
Photo by Lupin at Wikimedia Commons.

1. Turkeys are all-American. The modern domesticated turkey is descended from the wild turkey of North America, which is essentially a pheasant.

2. Domestic turkeys can’t fly or have sex. Domestic turkeys have been bred to have enormous breast muscles for our dinner tables. Their breast muscles have become so large that these top-heavy birds have lost the ability to fly and even to have sex! Domestic turkey eggs now have to be fertilized by artificial insemination. Wild turkeys with their functionally-sized breast muscles, however, can fly up to 55 mph for short distances and have sex just fine.

3. Male turkeys (called toms) are courtship-machines. Wild turkey males are substantially larger than females, and their 5,000 to 6,000 feathers have red, purple, green, copper, bronze, and gold iridescence. Like peacocks, male turkeys puff up their bodies and spread their elaborate feathers to attract mates and intimidate rivals. In comparison, female wild turkey feathers are duller shades of brown and grey to better hide from predators. And as if their flashy feathers weren’t enough, toms also have fleshy body appendages called snoods (the fleshy snotsicle that hangs over their beak) and wattles (the thing that looks like a scrotum under their chin). When the male is excited, the snood and wattle fill with blood and turn bright red. Sexy!

4. Turkeys are intelligent animals. They even have the ability to learn the precise details of a 1,000-acre area. And no, turkeys will not drown if they look up into the sky during a rainstorm.

5. Turkeys are social animals. They create lasting social bonds with each other and are very affectionate. Turkeys can produce over 20 different vocalizations, including the distinctive gobble (produced only by males), which can be heard up to a mile away! Individual turkeys have unique voices that they use to recognize each other.

6. Female turkeys (called hens) are good moms. Wild turkey babies (called poults) are precocial, which means that they hatch out of their eggs already covered in fluffy down and able to walk, run and feed themselves. They stick close to their mother for protection from predators, but unlike many other species of bird mothers, she doesn't have to feed them. Although wild turkeys roost in the trees at night to avoid predators, poults are unable to fly for their first few weeks of life. The mother stays with them at ground level to keep them safe and warm until they are strong enough to all roost in the trees with her.


A wild turkey mom and her poults. Photo by Kevin Cole at Wikimedia Commons.

7. Ben Franklin wanted the turkey to be America’s national bird. Benjamin Franklin famously argued that the wild turkey, not the bald eagle, should be America's national bird. In a letter to his daughter, he wrote, "For my own part, I wish the bald eagle had not been chosen as the representative of our country; he is a bird of bad moral character; he does not get his living honestly...like those among men who live by sharping and robbing...he is generally poor, and often very lousy. Besides, he is a rank coward; the little king-bird, not bigger than a sparrow, attacks him boldly and drives him out of the district...For in truth, the turkey is in comparison a much more respectable bird, and withal a true original native of America. Eagles have been found in all countries, but the turkey was peculiar to ours...".

8. Turkeys were once endangered. Although millions of wild turkeys used to live across the Americas, they were almost completely wiped out due to a combination of over-hunting and habitat destruction. Thanks to strong conservation efforts that included better hunting management, habitat protection, captive breeding, and reintroduction into the wild, wild turkey populations are now healthy and found in all of the lower 48 states.

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

Can You Feel the Love Tonight? (A Guest Post)

A reposting of an article by Maggie Nannenhorn from March 14, 2016.

If you’re like me, you never truly realize how quiet winter is until all the sounds of spring come back in a chorus of celebration. Between the birds, crickets, and frogs, you can really hear the love in the air. So you can hear the love, but can you feel the love?

Wood frogs are known for their chorus of calls that sound like a duck laughing. Seriously, tell a duck a good knock-knock joke and that is what a male wood frog sounds like when trying to attract a mate. He makes the call by expanding his two vocal sacs, membranes of skin underneath the neck, forming a bubble-like appearance. When a female surfaces, drawn to the call, the male frog clasps onto her, causing her to lay her eggs. The male frog then externally fertilizes the eggs. This form of mating is termed amplexus. The use of the call in the reproduction ritual is well studied. However, it is possible the small ripple formed in the water from the expanding vocal sack is relaying information that influences the mating behavior of these frogs.

Male wood frog resting on the water surface. Image by Maggie Nannenhorn.

Male wood frog calling with vocal sac expanded.
Notice the ripple it creates in the water. Image by Maggie Nannenhorn.

In 2010, Gerlinde Höbel and Robb Kolodziej from the University of Wisconsin-Milwaukee conducted an experiment that explored the use of water surface waves in wood frog reproductive behavior. They hypothesized male wood frogs use ripples in the water to find female wood frogs to mate with, while female wood frogs use ripples in the water as indicators of harassing males.

Video of a wood frog calling by Maggie Nannenhorn.

Wood frogs have a very short mating period: only 1 to 3 days per year! This study occurred on April 1st - 2nd, which corresponded with the wood frogs’ natural mating period. The first component of the study was the observation of a pond containing more than 500 wood frogs in amplexus. Amplexus was determined by the presence of males clasping on to the backs of female frogs in the water. They learned males approach surface waves on the water and clasp onto the frog that caused the ripple. However, females move away from surface waves on the water and dive downward.

After preliminary observations, they developed an experiment to cause rippling of the water. The first experiment tested the effect of stimulation (dipping a wooden probe into the water) near male wood frogs. The males tested were randomly assigned to either a control group or an experimental group. The 34 males in the control group were simply observed, and the direction and pattern of movement was recorded. For the experimental group, a long wooden probe was dipped in and out of the water 25 cm away from a male frog for 10 seconds. The resulting ripple was meant to mimic a ripple caused by a female frog moving in the water. Based on the hypothesis, the male wood frogs should approach the ripple hoping to find a female to mate with. Of the 60 males in the experimental group, half were stimulated from the right and half were stimulated from the left. A circle diagram (depicted below) was used to map the direction the males moved.

Video of a wood frog approaching ripples by Gerlinde Höbel.

This figure shows: a) the control group and b) the experimental group.
A circle diagram representing the reproductively driven movement direction
of wood frogs (Lithobates sylvaticus) in a laboratory pool as a result of
stimulated surface waves on both the left and right sides.
Figure from: Höbel, G., & Kolodziej, R. C. (2013). Behaviour, 150(5), 471-483.

The females are difficult to observe in the field since they prefer to stay beneath the surface. So, the researchers set up a tank to test 4 breeding pairs of wood frogs. They tested the females both while in amplexus and while alone. They dipped wooden probes into the water to stimulate the females on both the left and the right side in turn. Their positions and directions were also recorded using a circle diagram.

So, what did they find? It turns out, their predictions were correct! The males would approach the ripple caused by the probing. This is likely because the ripple may indicate a competing male they want to drive away or a female they want to mate with. The females moved away from the ripples by either swimming away or diving underneath the water surface. This may reduce the amount of harassment they receive from males. If a female becomes the center of attention for too many males, she may drown from the weight of them all attempting to grab her. Besides, if a male is fit, he will likely be able to catch up to her and successfully mate with her despite her swimming away.

The mating calls and movement of the wood frogs affect the surface waves, and these waves are used to make sexual behavior choices. This spring, the chorus of love will still ring out through the reeds, and I encourage you to take a moment to stop and listen. When you’re stopped, take a moment to notice the waves of love bringing these wood frogs together. Hopefully this spring, we will all be feeling the love.



Reference:

Höbel, G., & Kolodziej, R. (2013). Wood frogs (Lithobates sylvaticus) use water surface waves in their reproductive behaviour Behaviour, 1-13 DOI: 10.1163/1568539X-00003062

Can You Feel the Love Tonight? (A Guest Post)

By Maggie Nannenhorn

If you’re like me, you never truly realize how quiet winter is until all the sounds of spring come back in a chorus of celebration. Between the birds, crickets, and frogs, you can really hear the love in the air. So you can hear the love, but can you feel the love?

Wood frogs are known for their chorus of calls that sound like a duck laughing. Seriously, tell a duck a good knock-knock joke and that is what a male wood frog sounds like when trying to attract a mate. He makes the call by expanding his two vocal sacs, membranes of skin underneath the neck, forming a bubble-like appearance. When a female surfaces, drawn to the call, the male frog clasps onto her, causing her to lay her eggs. The male frog then externally fertilizes the eggs. This form of mating is termed amplexus. The use of the call in the reproduction ritual is well studied. However, it is possible the small ripple formed in the water from the expanding vocal sack is relaying information that influences the mating behavior of these frogs.

Male wood frog resting on the water surface. Image by Maggie Nannenhorn.

Male wood frog calling with vocal sac expanded.
Notice the ripple it creates in the water. Image by Maggie Nannenhorn.

In 2010, Gerlinde Höbel and Robb Kolodziej from the University of Wisconsin-Milwaukee conducted an experiment that explored the use of water surface waves in wood frog reproductive behavior. They hypothesized male wood frogs use ripples in the water to find female wood frogs to mate with, while female wood frogs use ripples in the water as indicators of harassing males.

Video of a wood frog calling by Maggie Nannenhorn.

Wood frogs have a very short mating period: only 1 to 3 days per year! This study occurred on April 1st - 2nd, which corresponded with the wood frogs’ natural mating period. The first component of the study was the observation of a pond containing more than 500 wood frogs in amplexus. Amplexus was determined by the presence of males clasping on to the backs of female frogs in the water. They learned males approach surface waves on the water and clasp onto the frog that caused the ripple. However, females move away from surface waves on the water and dive downward.

After preliminary observations, they developed an experiment to cause rippling of the water. The first experiment tested the effect of stimulation (dipping a wooden probe into the water) near male wood frogs. The males tested were randomly assigned to either a control group or an experimental group. The 34 males in the control group were simply observed, and the direction and pattern of movement was recorded. For the experimental group, a long wooden probe was dipped in and out of the water 25 cm away from a male frog for 10 seconds. The resulting ripple was meant to mimic a ripple caused by a female frog moving in the water. Based on the hypothesis, the male wood frogs should approach the ripple hoping to find a female to mate with. Of the 60 males in the experimental group, half were stimulated from the right and half were stimulated from the left. A circle diagram (depicted below) was used to map the direction the males moved.

Video of a wood frog approaching ripples by Gerlinde Höbel.

This figure shows: a) the control group and b) the experimental group.
A circle diagram representing the reproductively driven movement direction
of wood frogs (Lithobates sylvaticus) in a laboratory pool as a result of
stimulated surface waves on both the left and right sides.
Figure from: Höbel, G., & Kolodziej, R. C. (2013). Behaviour, 150(5), 471-483.

The females are difficult to observe in the field since they prefer to stay beneath the surface. So, the researchers set up a tank to test 4 breeding pairs of wood frogs. They tested the females both while in amplexus and while alone. They dipped wooden probes into the water to stimulate the females on both the left and the right side in turn. Their positions and directions were also recorded using a circle diagram.

So, what did they find? It turns out, their predictions were correct! The males would approach the ripple caused by the probing. This is likely because the ripple may indicate a competing male they want to drive away or a female they want to mate with. The females moved away from the ripples by either swimming away or diving underneath the water surface. This may reduce the amount of harassment they receive from males. If a female becomes the center of attention for too many males, she may drown from the weight of them all attempting to grab her. Besides, if a male is fit, he will likely be able to catch up to her and successfully mate with her despite her swimming away.

The mating calls and movement of the wood frogs affect the surface waves, and these waves are used to make sexual behavior choices. This spring, the chorus of love will still ring out through the reeds, and I encourage you to take a moment to stop and listen. When you’re stopped, take a moment to notice the waves of love bringing these wood frogs together. Hopefully this spring, we will all be feeling the love.



Reference:

Höbel, G., & Kolodziej, R. (2013). Wood frogs (Lithobates sylvaticus) use water surface waves in their reproductive behaviour Behaviour, 1-13 DOI: 10.1163/1568539X-00003062

Caught in My Web: Funky "New" Species

Image by Luc Viatour at Wikimedia.

Given the rate of extinction of creatures great and small, you may be surprised to learn that we discover about 18,000 new species every year! For this edition of Caught in My Web, we explore some of these new-to-us species.

1. Jessica Schmerler explains how animals are classified and named and has a fun slideshow of 2014's top 10 interesting animals at Scientific American.

2. Jane Lee at National Geographic talks about a newly discovered deep sea anglerfish with big teeth, spikes on its snout and a crazy-looking lure on the top of its head!

3. Justine Alford at IFLScience! shows us a newly discovered species of peacock spider.

The male dons a blue mask is is about as cuddly as a spider gets. Check out his dance here:

4. Stephanie Pappas at livescience shows us an adorable newly discovered jelly-bean sized masked frog.

5. Against conventional wisdom, a newly discovered species of frogs gives birth to live young! Dr. Dolittle at ScienceBlogs tells us all about it.

Let’s Talk Turkey: 8 Surprising Facts About Turkeys

A wild male turkey struts his stuff.
Photo by Lupin at Wikimedia Commons.

1. Turkeys are all-American. The modern domesticated turkey is descended from the wild turkey of North America, which is essentially a pheasant.

2. Domestic turkeys can’t fly or have sex. Domestic turkeys have been bred to have enormous breast muscles for our dinner tables. Their breast muscles have become so large that these top-heavy birds have lost the ability to fly and even to have sex! Domestic turkey eggs now have to be fertilized by artificial insemination. Wild turkeys with their functionally-sized breast muscles, however, can fly up to 55 mph for short distances and have sex just fine.

3. Male turkeys (called toms) are courtship-machines. Wild turkey males are substantially larger than females, and their 5,000 to 6,000 feathers have red, purple, green, copper, bronze, and gold iridescence. Like peacocks, male turkeys puff up their bodies and spread their elaborate feathers to attract mates and intimidate rivals. In comparison, female wild turkey feathers are duller shades of brown and grey to better hide from predators. And as if their flashy feathers weren’t enough, toms also have fleshy body appendages called snoods (the fleshy snotsicle that hangs over their beak) and wattles (the thing that looks like a scrotum under their chin). When the male is excited, the snood and wattle fill with blood and turn bright red. Sexy!

4. Turkeys are intelligent animals. They even have the ability to learn the precise details of a 1,000-acre area. And no, turkeys will not drown if they look up into the sky during a rainstorm.

5. Turkeys are social animals. They create lasting social bonds with each other and are very affectionate. Turkeys can produce over 20 different vocalizations, including the distinctive gobble (produced only by males), which can be heard up to a mile away! Individual turkeys have unique voices that they use to recognize each other.

6. Female turkeys (called hens) are good moms. Wild turkey babies (called poults) are precocial, which means that they hatch out of their eggs already covered in fluffy down and able to walk, run and feed themselves. They stick close to their mother for protection from predators, but unlike many other species of bird mothers, she doesn't have to feed them. Although wild turkeys roost in the trees at night to avoid predators, poults are unable to fly for their first few weeks of life. The mother stays with them at ground level to keep them safe and warm until they are strong enough to all roost in the trees with her.


A wild turkey mom and her poults. Photo by Kevin Cole at Wikimedia Commons.

7. Ben Franklin wanted the turkey to be America’s national bird. Benjamin Franklin famously argued that the wild turkey, not the bald eagle, should be America's national bird. In a letter to his daughter, he wrote, "For my own part, I wish the bald eagle had not been chosen as the representative of our country; he is a bird of bad moral character; he does not get his living honestly...like those among men who live by sharping and robbing...he is generally poor, and often very lousy. Besides, he is a rank coward; the little king-bird, not bigger than a sparrow, attacks him boldly and drives him out of the district...For in truth, the turkey is in comparison a much more respectable bird, and withal a true original native of America. Eagles have been found in all countries, but the turkey was peculiar to ours...".

8. Turkeys were once endangered. Although millions of wild turkeys used to live across the Americas, they were almost completely wiped out due to a combination of over-hunting and habitat destruction. Thanks to strong conservation efforts that included better hunting management, habitat protection, captive breeding, and reintroduction into the wild, wild turkey populations are now healthy and found in all of the lower 48 states.

The Biology of Nagging

A female pied flycatcher can't feed herself sufficiently
while she incubates her eggs and newly-hatched
chicks. Photo by Alejandro Cantarero.

I have been blessed with the fortune of not just having two healthy and happy babies, but being able to spend much of the spring and summer nurturing them and watching them develop and grow. But it has not been all roses: their smiles beam through the fog of my sleep deprivation and exhaustion. Their tears are met with my own. Our clothes are stained in a rainbow of bodily fluids. Now I am back at work trying to remember how my life used to be and how to meet my obligations to countless people, all while trying to keep up with the ever-changing needs of my daughters. Luckily, I am not alone. The girls have a rotating schedule with their grandparents one day, with their dad another, at daycare for a few days, and with me on weekends and evenings. But as the expectations on me grow heavier, I find myself pushing my husband harder to do more with the girls and around the house. Now it seems like every time I open my mouth, I am accused of “being a nag” and “for no reason” no less. The truth is, nagging has a deep biologically-based reason and may even be critical to species survival.

We are not the only species that nags, although in other species these vocalizations are often called “begging signals”. Begging signals are commonly heard in bird species in which the female does most or all of the egg and chick incubation. Because these females cannot sufficiently feed themselves while ensuring the survival of their brood, their male partners need to spend extra time foraging for the females in addition to foraging for the chicks and themselves. There is an inherent conflict between how mated males would prefer to spend their time (feeding themselves, maintaining their dominance status, and flirting with females) and how their female partners want them to spend their time (providing as much as possible for the family). The male response to this conflict is often to see how little he can get away with contributing while he sneaks off to spend his time as he wishes. The female response is to produce loud, juvenile vocalizations and gestures until he brings food to the nest. Is this really necessary though? Maybe she is just being manipulative to try to get him to do more than he really needs to.

Alejandro Cantarero, Jimena López-Arrabé, Antonio Palma, and Juan Moreno from the National Museum of Natural Sciences in Madrid, Spain and Alberto Redondo from the University of Córdoba in Spain set out to test whether the begging signals made by female pied flycatchers were an honest signal of need or were just obnoxious melodrama. They predicted that if the females’ begging calls were an honest reflection of how much help they needed, then begging calls would increase as energy needs increase.

The researchers studied 71 pied flycatcher nests in a forest in central Spain. Behaviors were observed by nest-mounted video cameras five days after the females finished laying their clutches of eggs. Two days later, each female was caught and measured, fitted with an identifying leg band, and had her wings clipped. About half of these females had their primary feathers clipped at the base to impair their ability to fly (these females are called the “handicapped” group). The other half had their primary feathers clipped at the tip so that their ability to fly would not be affected (these are the “control” females). When the females were released, they all returned to their nests. Their behaviors were measured again three days later.

Females in the handicapped group lost weight and begged significantly more after their wings were clipped, whereas the control females did not. This suggests that females are adjusting their begging rates to accurately reflect their needs. Furthermore, male partners of the handicapped females fed their partners more after the wing-clipping, whereas the male partners of the control females did not. This shows that the males are responding to either their partners’ increased begging or increased need or both. Revealingly, the amount that females begged was positively correlated with the amount that the males fed them, even when the researchers statistically controlled for whether their wings were clipped or not. This means that males were feeding females more because they begged more (and not simply because they needed more, which was also true).

This nagging female gets exactly what she needs.
Video by Alejandro Cantarero.

So, at least among pied flycatchers, females don’t “nag for no reason”, but because they genuinely need the help to keep their bodies and families healthy and safe. And males respond to the calls for help by increasing their contributions. But the graph that shows that males feed females more because they beg more also reveals that males would not help enough if females did not beg enough. Nagging is an adaptive strategy that females must engage in to meet the needs of the family.

Is someone nagging you too much? If we are like our pied flycatcher friends, than if you meet that person’s needs, the nagging should stop.

Want to know more? Check this out:

Cantarero, A., López-Arrabé, J., Palma, A., Redondo, A., & Moreno, J. (2014). Males respond to female begging signals of need: a handicapping experiment in the pied flycatcher, Ficedula hypoleuca Animal Behaviour, 94, 167-173 DOI: 10.1016/j.anbehav.2014.05.002

Can Animals Sense Each Other’s Wants and Hopes?

Is the ability to empathize uniquely human? This question has long been pondered by philosophers and animal behaviorists alike. Empathy depends in part on the ability to recognize the wants and hopes of others. A new study by researchers at the University of Cambridge suggests that we may not be alone with this ability.

A male Eurasian jay feeds his female mate. Photo provided by Ljerka Ostojić.

Ljerka Ostojić, Rachael Shaw, Lucy Cheke, and Nicky Clayton conducted a series of studies on Eurasian jays to explore whether male jays could perceive changes in what their female partners desired. Eurasian jays are a good species with which to explore this phenomenon because males routinely provide food to their female mates as a part of their courtship. The researchers wanted to know if males would adjust what food items males offered their mates depending on what food type the females wanted more.

In order to make a female prefer one food type over another, the researchers fed each female one of two food types (wax moth larvae and mealworm larvae) until they were full. But being full of one type of food doesn’t mean you can’t find room for desert, right? So when the researchers then offered the females access to both wax moth larvae and mealworm larvae, those that had previously eaten wax moth larvae now preferred mealworm larvae and those that had previously eaten mealworm larvae now preferred wax moth larvae. But could their male partners tell what they preferred at that moment?

In order to test whether male jays were sensitive to their partners’ desires, the researchers fed the females either wax moth larvae or mealworm larvae until they were full. They did this while their male partners watched from behind a transparent screen. They then removed the screen and gave the males 20 opportunities to choose between a single wax moth larvae or mealworm larvae to feed their partner. In this context, males usually chose to share with their mates the food that their partners preferred rather than the food their partners had already been fed! But are the males responding to their mate’s behavior or are they responding to what they saw when the females were eating earlier?

This video (provided by Ljerka Ostojić) shows the experimental process
in which the male chooses a food type and then shares it with his mate.

The researchers repeated the study with an opaque screen so the males could not see their mates while the females gorged on one particular food type. Without the ability to see the mate eating beforehand, males chose both food types equally and did not attend to their mate’s preferences. Because the females still had a preference for the opposite food type but the males were not adjusting for that preference, this means that the males are not responding to their mate’s behavior in this experiment or the previous one. This suggests that if male Eurasian jays see what their mates are eating, then somehow they have the ability to know to give their mate the opposite food type!

Whether this process involves the males having an understanding of their mate’s desires or some other mechanism is not fully known. But male Eurasian jays are certainly adjusting what they give their mates according to what she wants. Now if we can only teach human males to do that!

Want to know more? Check this out:

Ostojić, L., Shaw, R.C., Cheke, L.G., & Clayton, N.S. (2013). Evidence suggesting that desire-state attribution may govern food sharing in Eurasian jays PNAS, 110 (10), 4123-4128 DOI: 10.1073/pnas.1209926110