During the Halloween season, we find ourselves surrounded by monsters in movies, stores and decorations. We laugh at the ridiculousness of it all, oblivious to the fact that there are true monsters on our planet today! Mind you, these are not monsters in that they are evil, but they do have many of the same abilities and inclinations of our own mythical werewolves, vampires, zombies and shape-shifters.
Werewolf birds:
A Barau's petrel. Photo by SEOR
available at Wikimedia Commons.
Barau’s petrel is a migrating sea bird that is most active during nights with a full moon. Researchers tied bio-loggers on the birds’ feet to track their activity levels and found that under the full moon, the birds spent nearly 80% of these moonlit nights in flight! It is thought that since these birds migrate longitudinally (parallel with the equator), they can’t use changes in day length as a cue to synchronize their breeding, so they use the phases of the moon instead.
Vampire bats:
Three different bat species feed solely on blood: the common vampire bat, the hairy-legged vampire bat and the white-winged vampire bat. Feeding on blood is not uncommon – The actual term for it is hematophagy, and it is common in insects (think of those pesky mosquitos) and leeches. Although we don’t commonly think of it this way, blood is a body tissue and, like meat, it is rich in protein and calories. The reason it has not become a more popular food source among mammals is probably because it is so watered down (literally) compared to meat, that it can’t provide enough nutrition to sustain a large warm-bodied mammal. This is where our little vampire bat friends come in… small, stealthy, and with specialized saliva that prevents their victims’ blood from clotting, these guys are able to take advantage of this abundant resource, drinking up to half of their body weight in blood every night.
Zombees:
Scientists have recently discovered some strange honey bees: They mindlessly leave their hives in the middle of the night and fly in circles, often towards lights. It turns out that these honey bees are being parasitized by a species of phorid fly called the zombie fly. Female phorid flies lay their eggs inside the abdomens of honey bees, where the eggs hatch into larvae. The larvae feed on the insides of their bee hosts until they are mature enough to leave through the poor bee’s neck (the honey bee is generally dead by this time). Once out, the zombie flies develop into adults so they can breed and start the cycle anew with a new bee host. This phenomenon is still in the early stages of discovery, so if you would like to get involved in this project by watching honey bees in your area, check out ZomBee Watch, a citizen science project to track this zombie infestation.
Shape shifters:
The mimic octopus is a small harmless octopus that lives on the exposed shallow sandy bottoms of river mouths. To avoid its many predators it has developed an amazing strategy: it pretends to be something else, morphing its body into new shapes, like the shape of a deadly lion-fish, a poisonous flatfish, a venomous banded sea-snake, or any number of other animals that live in the area. Not only does the mimic octopus change its shape, it also changes its behavior to match its “costume” to convincingly fool predators. Most cephalopods, which include octopuses, are well-known for their ability to change the color, pattern and texture of their skin to blend in with rocks, coral and plants. Furthermore, octopuses do not have rigid skeletal elements, which allows their bodies great flexibility in the forms they imitate. But this ability to change both physical appearance and behavior to switch back and forth among imitations of multiple species is unique to this astounding shape shifter.
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!
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!
Democracy is hard. And slow. And complicated. But if it is done well, it can result consistently in the best decisions and courses of action for a group. Just ask honeybees.
When a honeybee hive becomes overcrowded, the colony (which can have membership in the tens of thousands) divides in what will be one of the riskiest and potentially deadliest decisions of their lives. About a third of the worker bees will stay home to rear a new queen while the old queen and the rest of the hive will leave to establish a new hive. The newly homeless colony will coalesce on a nearby branch while they search out and decide among new home options. This process can take anywhere from hours to days, during which the colony is vulnerable and exposed. But they can’t be too hasty: choosing a new home that is too small or too exposed could be equally deadly.
Our homeless honeybee swarm found an unconventional "branch". We'd better
decide on a new home soon! Photo by Nino Barbieri at Wikimedia.
Although each swarm has a queen, she plays no role in making this life-or-death decision. Rather, this decision is made by a consensus among 300-500 scout bees after an intense “dance-debate”. Then, as a single united swarm, they leave their branch and move into their new home. At this point, it’s critical that the swarm is unified in their choice of home site, because a split-decision runs the risk of creating a chaos in which the one and only queen can be lost and the entire hive will perish. This is a high-stakes decision that honeybees make democratically, efficiently, and amazingly, they almost always make the best possible choice! How do they do that? And how can we do that?
The honeybee house-hunting process has several features that allow them, as a group, to hone in on the best possible solution. The process begins when a scout discovers a site that has the potential to be a new home. She returns to her swarm and reports on this site, using a waggle dance that encodes the direction and distance to the site and her estimate of its quality. The longer she dances, the more suitable she perceived the site to be. Other scouts do the same, perhaps visiting the same site or maybe a new one, and they report their findings in dance when they return. (Importantly, scouts only dance for sites that they have seen themselves). As more scouts are recruited, the swarm breaks into a dancing frenzy with many scouts dancing for multiple possible sites. Over time, scouts that are less enthusiastic about their discovered site stop dancing, in part discouraged by dancers for other sites that head-bump them while beeping. Eventually, the remaining dancing scouts are unified in their dance for what is almost always the best site. The swarm warms up their flight muscles and off they go, in unison, to their new home.
Each dot represents where on the body this dancer
was head-bumped by a dancer for a
competing site.
Each time she's bumped, she's a little less
enthusiastic about her own dance.
Figure from
Seeley, et al. 2012 paper in Science.
What can we learn from these democratic experts? As much as I would love to see Congress in a vigorous dance-debate head-butting one another, I don't think that is the take-home message of choice. Tom Seeley at Cornell University has gained tremendous insight into effective group decision-making from his years observing honeybees, which he shares with us in his book, Honeybee Democracy. Tom has summarized his wisdom gained from observing honeybees in the following:
Members of Highly Effective Hives:
1. share a goal
2. search broadly to find possible solutions to the problem
3. contribute their information freely and honestly
4. evaluate the options independently and vote independently
5. aggregate their votes fairly
All of these critical guidelines can be encapsulated with a single objective: The decision-making body needs to objectively consider a range of information from individuals with diverse backgrounds, expertise, and knowledge. We can apply this to our own human decision-making: It means that we all need to vote objectively and honestly and independently. This means casting votes that are consistent with our own information and judgements, even when they are not consistent with the policical party we may align ourselves with. It also means that if you don't agree with the decisions of your School Board, Town Board, City Council, County Legislature, State Legislature, or National Legislature, then your background, expertise and knowledge are likely missing from the deciding body. Yes, you can write and call your representatives and provide them with part of your knowledge, or you can run for office yourself and make people with your background truly included in the decision-making process.
Many feel that our hive has been homelessly clinging to our exposed branch for too long. If we are going to make good, well-informed, effective, and efficient decisions, we need open and respectful communication across diverse backgrounds. Independent thinking and diversity improves the quality of the decisions that affect us all. If honeybees can do it, so can we.
2. Seeley, T., Visscher, P., Schlegel, T., Hogan, P., Franks, N., & Marshall, J. (2011). Stop Signals Provide Cross Inhibition in Collective Decision-Making by Honeybee Swarms Science, 335 (6064), 108-111 DOI: 10.1126/science.1210361
3. List, C., Elsholtz, C., & Seeley, T. (2009). Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honeybee swarms Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1518), 755-762 DOI: 10.1098/rstb.2008.0277
It seems like everyone is racking their brains to come up with a great Halloween costume. But we’re not the only ones to disguise ourselves as something we’re not. Many animals put on costumes just like we do. Take this gharial crocodile for example (do you see him?), covering himself in parts of his environment to hide.
Other animals, like this tawny frogmouth below, develop physical appearances that help them blend in with their surroundings. When threatened, these birds shut their eyes, erect their feathers and point their beak in such a way to match the color and texture of the tree bark.
Image by C Coverdale at Wikimedia Commons.
Rather than hide, some animals have a physical appearance to disguise themselves as other species that are often fierce, toxic or venomous. This type of mimicry is called Batesian mimicry, named after Henry Walter Bates, the English naturalist who studied butterflies in the Amazon and gave the first scientific description of animal mimicry. This plate from Bates’ 1862 paper, Contributions to an Insect Fauna of the Amazon Valley: Heliconiidae, illustrates Batesian mimicry between various toxic butterfly species (in the second and bottom rows) and their harmless mimics (in the top and third rows).
This plate from Bates’ 1862 paper, Contributions to an Insect Fauna of the Amazon Valley: Heliconiidae is available on Wikipedia Commons.
The bluestriped fangblenny takes its costume another step further, by changing its shape, colors, and behavior to match the company. This fish changes its colors to match other innocuous fish species that are around so it can sneak up and bite unsuspecting larger fish that would otherwise bite them back! Learn more about them here.
The fish on the far left is a juvenile cleaner wrasse in the act of cleaning another fish. The two fish in
the middle and on the right are both bluestriped fangblennies, one in its cleaner wrasse-mimicking
coloration (middle) and the other not (right). Figure from the Cheney, 2013 article in Behavioral Ecology.
But the Master of Disguise title has got to go to the mimic octopus. This animal can change its color, shape and behavior to look and behave like a wide range of creatures, including an innocuous flounder, a poisonous lionfish, or even a dangerous sea snake! Check it out in action:
Vampire mythologies have been around for thousands of years, terrifying the young and old alike with stories of predatory bloodsuckers that feed on our life essences. You may not believe in vampires, but they are all around us. In fact, you may have some in the room with you right now! You just don’t notice them because they are not human, or even human-like.
Vampires feed on the blood of their victims in order to sustain their own lives. This phenomenon, called hematophagy, is more common than typically occurs to us at first. Just take mosquitoes and ticks as examples. Once we’ve opened our minds to the idea of bloodthirsty arthropods, we quickly think of many more: bedbugs, sandflies, blackflies, tsetse flies, assassin bugs, lice, mites, and fleas. In fact, nearly 14,000 arthropod species are hematophages. We can expand our thoughts now to worms (like leeches), fish (such as lampreys and candirús), some mammals (vampire bats), and even some birds (vampire finches, oxpeckers, and hood mockingbirds). We’ve been surrounded by vampires our whole lives, we just never sat up to take notice!
Hematophagous animals are not as scary as mythical vampires, in part because they don’t suck their victims dry – they just take a small blood meal to sustain their tiny bodies. Hematophagy is not, in itself, lethal. However, the process of exposing and taking the blood of many individuals transmits many deadly diseases, like malaria, rabies, dengue fever, West Nile virus, bubonic plague, encephalitis, and typhus.
Because blood feeders do not kill their meals, feeding can be even more dangerous for them than for traditional predators. As a result, many hematophagous animals have developed a similar toolkit. Many have mouthparts that are specialized to work as a needle or a razor and biochemicals in their saliva that work as anticoagulants and pain killers. Their primary skill, however, is their stealth: they can sneak up on you, eat their meal, and be home for bed before you even notice the itch.
Although a few species, like assassin bugs and vampire bats, are obligatory hematophages (only eat blood), most hematophages eat other foods as well. Somehow, Dracula is not quite so intimidating when you imagine him drinking his morning fruit juice, like many mosquitoes do.
Why drink blood in the first place? Blood is a body tissue like any other, and it contains a lot of protein and a variety of sugars, fats and minerals, just like meat. However, blood is mostly water, which means that a blood meal contains less protein and calories than the same weight of meat. Because you need to consume so much more to get enough protein and calories out of a meal, large animals and animals that generate their own body heat can't usually rely on blood meals alone. So much for human-like vampires that only live off the blood of their victims.
A deadly vampire spreading malaria. Photo by the CDC available at Wikimedia.
So true vampires are everywhere, but they are small, take small blood meals, don't generally kill their hosts, and often use blood to supplement their other meals. Not so scary any more, are they? ...Although, about 3.2 billion people (about half the world's population) are at risk of contracting the deadly disease, malaria, from these bloodsuckers... so maybe you aren't scared enough. Bwaa-haha!
For the iconic monarch butterfly, the shorter days in fall mean it’s time to pack up and head south to a warmer climate! Just like clockwork, the Eastern population of monarch butterflies makes a 2000 mile journey to their winter paradise roosts in central Mexico. The journey in itself is one of the greatest migrations among all animals.
But here’s the catch: none of these butterflies has made this trip before. Several generations of monarchs have come and gone over the course of a summer, but the generation born in late August and early September are genetically prepared for months of survival without feeding or breeding. But their predecessors didn’t exactly leave them with a map. How do they know where to go? Do they have a map and compass inside their heads? The answer: yes! Well, sort of…
Think about this: if you were lost in the woods and needed to find south, what would you do? Here’s a hint: look up! The sun can be a great resource when you’re lost, and I’m not talking about just asking it for directions. As the Earth rotates on its axis throughout the day, the sun appears to travel overhead. By knowing approximately what time of day it is, you can determine the cardinal directions. Monarchs use specialized cells or organs called photoreceptors that respond to light to establish the position of the sun.
Representation of time compensated sun compass orientation used by monarchs;
Image created by Anna Schneider.
Until recently, it was thought that monarchs simply used the photoreceptors on the top portion of their compound eyes, called the dorsal rim. Past studies have shown that the signals are passed from the photoreceptors on to the “sun compass” region in their brains and the butterflies change direction based on that information. Like most animals, it was assumed that their internal clock was located inside their brains. However, recent research has demonstrated that individuals whose antennae have been painted or removed altogether become disoriented when placed in flight simulators. These monarchs do not adjust for the time of day when trying to fly south. When those same antennae that were removed were placed in a petri dish, they continued to respond to light and showed signs that they continued the pattern of time. This indicates that antennae and the brain are both needed for the monarchs to correctly determine their direction.
Diagram of features on the head of a monarch butterfly; Image created by Anna Schneider.
Now, estimating which way is South might be fine and dandy on a bright sunny day, but what happens when it’s cloudy? Not a problem for these super-insects! In another recent study, researchers tethered monarchs to flight simulators and altered the magnetic field conditions to see what would happen. When the magnetic field was reversed so magnetic North was in the opposite direction, the butterflies altered their bearings and flew exactly opposite as well. This suggests that monarchs could have some sort of way to detect the earth’s magnetic field, called magnetoreception, which could enhance the photoreception capabilities.
Many of the mechanisms behind the migration of these incredible creatures are yet to be discovered, but much progress has been made in the past decade. So next time you see a monarch butterfly, take a second look. There is more than meets the eye.
Sources:
Gegear, R., Foley, L., Casselman, A., & Reppert, S. (2010). Animal cryptochromes mediate magnetoreception by an unconventional photochemical mechanism Nature, 463 (7282), 804-807 DOI: 10.1038/nature08719
Guerra, P., Gegear, R., & Reppert, S. (2014). A magnetic compass aids monarch butterfly migration Nature Communications, 5 DOI: 10.1038/ncomms5164
Merlin, C., Gegear, R., & Reppert, S. (2009). Antennal Circadian Clocks Coordinate Sun Compass Orientation in Migratory Monarch Butterflies Science, 325 (5948), 1700-1704 DOI: 10.1126/science.1176221
Steven M. Reppert. The Reppert Lab: Migration. University of Massachusetts Medical School: Department of Neurobiology.
Sex is a dangerous, but necessary, part of life. Across the animal kingdom, there are a multitude of things that can go wrong. You could be injured in a fight by someone who wants to steal your mate, or maybe your partner eats you because you’re taking too long. Either way, nature must have a pretty good reason for the traumatizing effects of sex.
A male bed bug traumatically inseminates a female. Image by
Rickard Ignell at the Swedish University of Agricultural Sciences
posted at Wikimedia Commons.
Bed bugs have a particularly risky way of having sex. When a male bed bug wants to mate, he will pierce the female’s abdomen with his penis (called a lanceolate) and release sperm directly into her body cavity. Talk about forceful! This mode of reproduction in bed bugs is known as traumatic insemination; aptly named.
With what seems like a horrific way of reproducing, it’s hard to imagine that there are any benefits for the female. I’m sure you can come up with a plethora of things that could go wrong: infection, damage of major organs, bleeding, even death. Researchers Ted Morrow and Göran Arnqvist with Uppsala University in Sweden, argue that the female has a counter-adaptation to this antagonistic strategy. The area of the abdomen that the male pierces has been modified into a pocket lined with specialized tissues to prevent serious damage to the female. This area is termed the spermalege. Edward and Göran hypothesized that sex is not harmful to the female if the spermalege is punctured, but can be dangerous if any other area is pierced. They also hypothesized that more mating occurrences and improper punctures would reduce the lifespan of the female.
To test their hypotheses, Edward and Göran observed the number of times a female was inseminated and where she was pierced (on the spermalege or somewhere else). They had two set-ups to observe mating rate: (1) a female was placed with four males where lots of mating would take place and (2) a female was placed with four males, three of which had their penis glued to their abdomen so that they could not mate. These two set-ups allowed the researchers to observe the differences in female life span between those who had a high mating rate and those who had a low mating rate. Then, the researchers wanted to see where the female was being pierced and how that affected her life span. In addition to traumatic insemination by male bed bugs, the researchers used a pin to pierce the spermalege or an area outside the spermalege and then compared the damage.
The study produced two big results. First, females who mated more had a shorter lifespan than those who mated less. This was because the sperm and other fluids deposited caused an immune response as they were seen as foreign objects; too much of these foreign substances can have negative effects on the organism. Second, females that were pierced through the spermalege lived longer than those who were pierced outside the spermalege, suggesting that the spermalege functions to reduce damage and/or infection during insemination.
So what are the benefits of traumatic insemination and how does the spermalege reduce the costs to the female? Well, there is a lot of paternal ambiguity in the animal kingdom. The direct deposition of sperm into the abdomen may ensure paternity by getting the sperm as close to the ovaries as possible before another male bed bug can mate with her. This method also reduces courtship time and avoids female resistance, meaning that other males may not have the chance to steal the female away. The spermalege protects females from traumatic insemination by localizing damage to one area that can easily repair itself. Since the spermalege is lined with cuticle, it prevents the leakage of blood and sperm from the wound. The spermalege may also function to prevent entry of pathogens into the bloodstream. In the end, this traumatic insemination is no more dangerous than any other kind of sex, however painful and horrible it sounds. It may even be less risky if done correctly.
For more information, check out:
Morrow, E., & Arnqvist, G. (2003). Costly traumatic insemination and a female counter-adaptation in bed bugs Proceedings of the Royal Society B: Biological Sciences, 270 (1531), 2377-2381 DOI: 10.1098/rspb.2003.2514
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
Spiders creep most of us out. But let’s face it: they are pretty darn amazing! For this edition of Caught in My Web, we appreciate our 8-legged friends.
2. And lace sheet weaver spiders make optical illusion webs to lure nocturnal moths.
3. Even our run-of-the-mill spiders are pretty amazing, when you really look at them. Watch this amazing timelapse of a garden orb web spider building a web:
4. Portia, the spider-hunting spider, is a genius with super-powers:
Summer is a time of backyard bar-b-ques, camping, baseball games, beer, and mosquitoes. Ugh, mosquitoes! Have you ever noticed that when a bunch of us are hanging out together outside, some of us get eaten alive by those pesky buggers while others are hardly touched at all? It turns out, differences in how much alcohol we have imbibed may be a factor.
An Anopheles gambiae mosquito ready for a meal. Photo by James D. Gathany
at the Public Health Image Library at Wikimedia Commons.
“No! Say it ain’t so!”
I hate to be the bearer of bad news, so I’ll let the scientific evidence speak for itself.
A research team from the French Research Institute for Development, including Thierry Lefèvre, Louis-Clément Gouagna, Eric Elguero, Didier Fontenille, François Renaud, Carlo Costantini, and Frédéric Thomas, and Kounbobr Roch Dabiré, from the Institute for Research in Health Sciences in Burkina Faso set out to test whether people were more attractive to female mosquitoes after drinking a beer compared to beforehand. They only tested females because only female mosquitoes bite, requiring extra protein for their eggs.
The researchers put groups of 50 hungry female mosquitoes into the end of a special Y-shaped maze that let them fly in the direction of one of two odors. At the end of one arm of the Y-maze was a fan, simply blowing outdoor air through a tent and into the apparatus. At the other end of the Y-maze was a fan blowing air through a tent past a shirtless man and into the apparatus. This shirtless man had either not had anything to drink recently, or had recently drunk either a liter of beer or a liter of water. Between the starting chamber and both ends of the arms of the Y-maze were traps that would capture mosquitoes that had chosen to head that direction (lucky for the shirtless men). The number of mosquitoes caught in both traps combined (compared to the total of 50 that was initially released) was called mosquito activation, and reflected how many mosquitoes were motivated to take off and fly upwind. The proportion of mosquitoes caught in the volunteer-bated trap compared to those caught in both traps combined was called mosquito orientation, and reflected the attractiveness of the volunteer’s odor compared to the control odor.
Image A shows the two tents: one in which the man-bait sat (having consumed beer or water), and the other with no one in it. Air from each tent blew threw a tube (seen in picture B) and then into the building, past the traps and into the downwind box, where the mosquito starting-line was located (seen in picture C). Photos from Lefèvre et al., 2010.
The mosquitoes significantly increased both activation and orientation in response to the beer-drinking volunteers, but not in response to the water-drinking volunteers. That is to say, that the smell of someone that has had a beer motivates more mosquitoes to actively pursue them, and makes them more of a focused target of the mosquitoes.
The researchers believe there is an interaction between how our bodies naturally smell and how our bodies break down beer that increases the attractiveness of our odors to mosquitoes. People that were more attractive to mosquitoes before they drank were also more attractive to mosquitoes after they drank. But interestingly, people that were warmer or gave off more CO2 were not more attractive to mosquitoes.
You should know that this research is much more important than just being a drag on your summer bar-b-que. The particular mosquito species that these researchers studied was Anopheles gambiae, the primary vector for malaria in Africa. They did this study in Burkina Faso, a country in West Africa with a high rate of malaria, using a local beer called dolo. Dolo, a fermented sorghum beer with low (3%) alcohol content, is the most common alcoholic beverage in Burkina Faso. So if you are in a place with a high rate of malaria, knowing that you should take extra precautions against mosquitoes when you drink could be a life-saver.
Want to know more? Check this out:
Lefèvre, T., Gouagna, L.C., Dabiré, K.R., Elguero, E., Fontenille, D., Renaud, F., Costantini, C. and Thomas, F. (2010). Beer consumption increases human attractiveness to malaria mosquitoes. PloS one, 5(3), e9546.
Man, is it hot out there! While I tuck away in my cool, air-conditioned office, I think about those incredible animals that beat the heat with their own bodies and strategies. It turns out, there are only four major ways to exchange heat with your environment: conduction, convection, radiation and evaporation. The animals that are best equipped for a hot summer are those that take creative advantage of these mechanisms of heat transfer.
"My, what big ears you have!"
"The better to thermoregulate with, my dear!"
Photo by Bernard DUPONT at Wikimedia Commons.
We all exchange heat with our environment wherever our body comes in contact with the environment, namely, across our skin. Animals can increase the rate of this heat-exchange by having a larger surface area relative to the volume of their heat-containing bodies. Big, round animals have a particularly hard time dispersing excess heat, because they have a lot of heat stored in their big bodies, and proportionally not much surface area for the heat to leave from. You may think elephants have such big ears for hearing, but the truth is that they are major temperature-regulation organs. Big, flat body structures provide that added surface area for excess heat to dissipate from. Elephants have large ears with lots of large blood vessels, so they can pump hot blood from the body out to the ears, where they are closer to the cooler environment to dissipate by conduction and convection. The cooler blood then returns to the body core to cool it down.
Built for a life in the cool underground.
Photo by Ted M Townsend at Wikimedia Commons.
Reptiles use a different approach to take advantage of principles of conduction and convection, by burrowing. Burrows create a layer of insulation (usually soil and plant matter) that slows heat exchange and keeps the area below ground a more constant temperature. This means that, compared to the outside, burrows remain cooler in the summer and warmer in the winter. Many reptiles go into their summer burrow in the heat of day and emerge during cooler times of day. Blind lizards, however, take this burrowing idea to an extreme. Blind lizards are a family of legless lizards found in tropical forests. They are small, skinny, and have narrow heads, which make them look more like an earthworm than a lizard, but it also gives them great burrowing efficiency to stay underground and avoid the heat.
A dragonfly exposing as little of his body to the sun
as possible. Photo by Raphael Carter at Wikimedia Commons.
On a hot summer day, we all seek out the shade. This is to reduce the heat we absorb through radiation, and most of this radiation comes from the sun. But what do you do if you can’t find shade? Some dragonflies and damselflies raise their abdomens to aim their rear-ends towards the sun so they can shield themselves from the full-on intensity of the sun’s rays. This body position is called the obelisk posture, because when the sun is directly overhead, the insect’s handstand looks like an obelisk.
Really? Crapping on my own feet?
There has GOT to be a better way.
Photo by Rob Schoenmaker at Wikimedia Commons.
Evaporation is the most efficient way to dissipate heat. Some animals swim, some animals sweat, some animals pant, but vultures and storks win the cooling efficiency award. Vultures and storks. . . poop on their own legs and feet. With this approach, called urohydrosis, the animal releases a mixture of urine and poop through their single excretory hole, called a cloaca, onto their legs and feet. The subsequent evaporation from the high surface area of their long legs helps them to cool off.
So what can we learn from these heat-beating experts (without pooping on ourselves)? If you are hot, spread your body out, stay in the shade, and wet an area of your body with high surface area and exposed blood vessels (namely, your inner wrists and forearms). I’d use water though.
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
Moms are really important to life on Earth, as evidenced by the fact that maternal care is fairly common across the animal kingdom. In most species, females produce fewer, larger, and costlier eggs than males do sperm. Therefore, it is usually beneficial to females to maximize the possible success of each one, sometimes by gestating them inside their own bodies (as mammals do), or incubating the eggs until they are ready to hatch (as birds do), or by providing prolonged protection, food and training until they are ready to take on the world for themselves. But there is still a lot of variation in how and how much each mother gives to her offspring. Here are some of the best moms in the animal kingdom:
1. The Endurance Prize goes to orangutans: Orangutan infants cling to their moms’ bellies non-stop for the first four months of their life and they continue to completely depend on their moms for the first two years for food and transport. Their moms will continue to carry them often until they are five and will sometimes continue to breastfeed them until they are eight! After that, the young still stay close to mom, learning from her and helping her until they are sometimes in their teens.
An orangutan mama and toddler. Photo by Mistvan at Wikimedia Commons.
2. The Provider Prize goes to the crab spider, Diaea ergandros: These crab spider moms create a brood chamber and nest out of eucalyptus leaves. They guard their eggs and then spiderlings, providing protection and prey for food. These moms also make extra eggs, just for their babies to eat, and finally, they give themselves… quite literally! The babies eat their mothers completely in a rare behavior called matriphagy.
3. The Pregnancy Prize goes to elephants: Elephants are pregnant for about 22 months… nearly two years! And a baby elephant is not light to carry around… by the time it is born, it will weigh nearly 250 pounds! Just the thought of it makes me uncomfortable. So why would elephant moms need to gestate their young for such an incredibly long time? It is thought that the long gestation is needed for the proper development of their brains, so they are born with the complex cognitive and social skills needed to survive in their herd.
An African elephant family plays in the hot sun. Photo by Bernard Dupont at Wikimedia Commons.
4. The Brooding Prize goes to a deep-sea octopus: Two years is a very long time to carry a developing baby inside your body, but some animals care for their developing empryos ouside of their bodies with a behavior called brooding. Although brooding may sound easier than pregnancy, it is not for the faint of heart. A deep-sea octopus was observed brooding her eggs in the Monterey Submarine Canyon off central California for 53 months… That is nearly 4 and a half years! And that whole time she did not eat, but instead guarded and aerated the water around her precious eggs.
A deep-sea octopus. Photo by NOAA at Wikimedia Commons.
5. The Multi-Generational Prize goes to humans: Many human moms are not only good mothers, but also good grandmothers. Grandparenting is extremely rare in the animal kingdom (the first documented case of grandparenting in non-humans was as recent as 2008) and human females excel at it. They provide care, advice, resources, lessons and hugs to increase the success of their offspring and grand-offspring… It’s amazing other species haven’t picked up on this amazing secret yet!
The best moms in the animal kingdom. Photos by Sarah Jane Alger.
