A Master of Disguise (A Guest Post)

By Jake Klemm

Cephalopods are among the most intelligent of marine life. Their highly advanced nervous systems allow them to exhibit a complex array of behaviors (for example, camouflage). Within this array is a rather unique behavior observed in the cuttlefish Sepia pharaonis. These elegant beings are now known to… intensely flap their arms? These animals are truly graceful.

A lovely photo of S. pharaonis. Image by Silke Baron at Wikimedia Commons.

Researchers Kohei Okamoto, Haruhiko Yasumuro, Akira Mori, and Yuzuru Ikeda of the University of the Ryukyus in Okinawa, Japan observed this behavior on two separate occasions while studying S. pharaonis. The scientists had initially collected these cuttlefish with the intention of conducting other experiments but noticed this behavior while the cuttlefish were introduced to a large water-filled tank and while hunting prey. After noticing this wild arm-flapping behavior, the researchers turned their attention towards why the behavior was being displayed.

The researchers first observed this behavior in December of 2011. The cuttlefish were placed in a large, circular tank for conducting other experiments when a couple of them were observed to flap their arms. After the initial experiments were finished, a few of the cuttlefish were placed in the same sized tank and observations were recorded with a video camera over a period of five days. This behavior was revisited in 2013 for further observation. The cuttlefish they used were reared from eggs found in the same coastal waters of Okinawajima Island as the cuttlefish that were part of the 2011 experiments. Again, cuttlefish were placed in a large tank to observe the behavior with a video camera. The researchers counted each occurrence of the behavior and recorded the duration of each behavior. After observations were complete, the researchers performed experiments to observe the hunting ability of S. pharaonis. This arm-flapping behavior was observed unexpectedly while the cuttlefish hunted prey. The means of recording the behavior were the same as described above. In addition, the researchers recorded the number of prey caught between cuttlefish that did and did not display the behavior.

The researchers noticed variation in the frequency and duration of this behavior in the presence and absence of prey. When placed in a tank without prey, only a small number of cuttlefishes displayed this behavior. Of the cuttlefish that did flap their arms, the behavior lasted (on average) no longer than 37 seconds. However, the cuttlefish that were placed in a tank with prey, the behavior was displayed for at significantly longer period of time. In addition to that, more cuttlefish overall were seen flapping their arms in this second experiment. The cuttlefish that flapped their arms caught a significantly larger number of fish than the ones that did not flap their arms, despite being observed in the same tank and having access to the same number of prey animals. This observation led the researchers to believe that something about this unique behavior is helping the cuttlefish capture more prey.

A front view of a cuttlefish. Image by Stickpen at Wikimedia Commons.

The resemblance is uncanny! Image by Maximilian Paradiz at Wikimedia Commons.

What could this all mean? The researchers think that the cuttlefish may be mimicking another organism, specifically the hermit crab, to confuse the prey fish into thinking that they are another harmless animal. It is thought that the head of the cuttlefish resembles the shell of the hermit crab while the arms resemble the eyes and legs of the hermit crab. Posing as a harmless crab would allow the cuttlefish to get behind enemy lines and ultimately catch more prey. Further research will have to be done in lab as well as the field to see if this behavior is really that of mimicry. Other cephalopods are notorious for mimicking other animals, so it is not out of the realm of possibility. Studying this behavior would allow scientists to difurtveher into the evolutionary history of S. pharaonis. Until then, the graceful limb-flailing will remain an ever-tantalizing mystery.


References

Okamoto, K., Yasumuro, H., Mori, A., & Ikeda, Y., (2017). Unique arm-flapping behavior of the pharaoh cuttlefish, Sepia pharaonic: putative mimicry of a hermit crab. Journal of Ethology, 35(3), 307-311. DOI: 10.1007/s10164-017-0519-7

Tiny Ninjas, Big Bites (A Guest Post)

By Alexis Brauner

Venom isn’t just a weapon for snakes and spiders.

A smaller, more dangerous insect is in existence and falls into the realm of venomous creatures: the assassin bug. This little critter is part of a scientific family called Reduviidae, a group where all the members share the same characteristic of being an ambush predatory bug. They prey on invertebrates (animals that don’t have a spine), such as crickets and mealworms, by injecting venom into them.

An assasin bug. Source: Fir0002/Flagstaffotos at Wikimedia Commons.

Assassin bugs are believed to have two versions of venom – one for feeding and one for defense. Both types of venom are made up of more than 100 proteins, but what is unique about it is its ability to paralyze and liquify the inside of the prey. That’s right… liquify. The tissues of the prey turn into a jello-like substance that the assassin bug can then suck through a long tube on its mouth called the proboscis.

How is the venom able to do that?

First, let’s peek at the mechanisms that work to carry the venom through the body of the assassin bug and into its meal.

The venom apparatus of an assassin bug is made up of three main parts: secretory glands, a muscle-driven pump, and a venom channel. The three secretory glands (the anterior main gland, posterior main gland, and accessory gland) are in the thorax and abdomen of the assassin bug. These separate glands release a specific form of assassin bug venom depending on what situation the bug is facing. For example, the anterior main gland releases a form of venom that does not paralyze prey but is thought to be used as a defense mechanism, while the posterior main gland releases the deadly form of venom.

The venom apparatus of an assassin bug. Source: Walker, et. al, 2018, modified by Alexis Brauner

Once released, the venom then makes its way to a muscle-driven pump within the head of the bug. The pump fills with the available venom when the muscle contracts and is released once the muscle relaxes. Think of the venom pump as a clothes pin: when you push on the prongs, the pin opens, and you can put things in it to hold; once you let go of the prongs, the mouth of the pin closes, but now the prong end is open. In this example, your fingers are the muscle and the clothes pin is the pump with one end open at a time. The muscle relaxation releases the venom into the venom channel in the interlocking maxillary stylets (also known as the fangs) of the assassin bug. And then…

BOOM!

Venom is in the food or the foe.

And if it’s in the food, then the tissues of the prey turn into liquid. This liquification phenomenon is caused by enzymes in assassin bug venom called proteases. All enzymes catalyze, or speed up, chemical reactions; however, proteases are specialized enzymes that catalyze the destruction of proteins. This means that the assassin bug venom goes into the prey and the proteases are like Pac-Men with razor sharp teeth that grind up the primarily protein tissue at such a lightning fast speed that, within seconds, the prey is juice!

Scientists continue to research assassin bug venom to learn more about its components, but one thing is for sure: The extraordinary liquid weapon housed in such a small insect is why assassin bugs are tiny ninjas with big bites.


To learn more:

Walker, A., Madio, B., Jin, J., Undheim, E., Fry, B., King, G. (2017). Melt With This Kiss: Paralyzing and Liquefying Venom of The Assassin Bug Pristhesancus plagipennis (Hemiptera: Reduviidae). Mol Cell Proteomics, 16 (4), 552-566. DOI: 10.1074/mcp.M116.063321.

Walker, A., Mayhew, M., Jin, J., Herzig, V., Undheim, E., Sombke, A., Fry, B., Meritt, D., King, F. (2018). The assassin bug Pristhesancus plagipennis produces two distinct venoms in separate gland lumens. Nat Commun, 9, 755. DOI: 10.1038/s41467-018-03091-5

Exploring How Predators Hunt

By Jon Clark

A "Lion King" in his natural habitat. Photo by Jon Clark.

Predatory animals are a huge obsession for most children at some point. From that picture book about the cool T-Rex to watching “The Lion King” millions of times, we’re fascinated with the kings of the food chain. And let’s be honest, even as adults they’re still pretty neat to us. Why else take a grand safari adventure to see lions and other animals in their natural habitat? So to fuel that curiosity, below is a guide to how predators hunt. It might just help you understand animal movements and behavior for watching wildlife.

The basics of how predators hunt

Predators are, of course, animals that feed on other animals. These predators rely on the flesh of other animals as a resource for their survival and are highly skilled at finding and catching it. Predators sit at the top of a delicate food web, all components of which fit together to keep the environment balanced over time.

Different types of predators have four main hunting strategies for finding their prey. According to an article from Idaho Public Television, they are:

• Chase: Think of an eagle diving for a mouse. This is chase behavior in predators. This method requires a delicate balance of hunting down food that provides enough energy and nutrition to offset the energy cost of running that food source down.


• Stalk: For this method, think of an egret or crane standing motionless or walking slowly in water, and then lunging as a tasty morsel goes by. This method is a huge time sink for the animal as it moves from cover to cover getting incrementally closer to it’s prey. It also takes far less energy, however, as only a small burst of speed is required at the end. This means that these predators can often live off of smaller prey. 


• Ambush: Lion researcher, George Schaller, watched a group of gazelles in the Serengeti. In order to access water, there was a patch of thick brush they would need to cross. As the gazelles entered the brush, Schaller watched as the lions hiding in wait, instantly ambushed and ate one of the gazelles. Due to their long manes and tan color, lions are nearly undetectable in such cover. The ambush requires a great deal of time, as it relies on other animals to wander into the area. For predators that have the patience, the success rates are quite high.


• Teamwork: Think of wolves working as a pack to take down a deer. This is one of the most exciting ways of how predators hunt. Teamwork allows the animals to pursue large and fast prey, scoring large amounts of food for the group. This is arguably one of the most successful tactics as seasoned hunters can quickly steer their prey in the direction of the other party. Additionally, the energy required for the chase and kill can be dispersed across the collective group. 

Lions on the hunt

One of the coolest and most popular things to see on a safari is a lion in its own natural habitat. This mighty “King of the Jungle” hunts both independently and as part of groups. Lions hunt some of the fastest animals in the world, like the wildebeest, which can run at speeds of 50 mph. Lions themselves are not incredibly fast, so they’ve had to get smart through a variety of hunting strategies.

Because lions are also relatively lazy animals, they tend to eat larger animals – which sustain them for longer periods. These animals include antelopes, zebras and wildebeest.

A lioness. Photo by Jon Clark.

The female lionesses hunt the most often for both themselves and for the males. A lioness will stalk from cover to cover to get close to the prey animal, and then pounce at the last minute. Their prey usually has slower reaction times, so this is a solid method. If the prey sees them, the lion will act innocent by sitting up and staring off into the distance, as if to say, “I wasn’t doing anything.”

Another method lions use is to find a bush near where the prey goes often, like a watering hole, and wait until they can strike. Lions have been known to actually nap while awaiting their deadly ambush.

To catch large or fast prey, lions leverage their group numbers to help each other cut off the escape of fleeing prey. When lions decide to hunt in pairs and groups their success rate goes up from about 18 percent to 30 percent while hunting alone and in daylight, according to the African Lion & Environmental Research Trust.

When hunting in groups, lions stalk in a pattern to encircle the prey. Then some attack, driving the prey to other waiting lions. As the prey animal tires from the constant running, one or two lionesses will try to jump on the back of the animal or hang by their claws from a zebra's or gnu's or buffalo's back. This certainly makes it very hard for the poor animal to run away from the next lion, who goes for the throat to complete the hunt. It’s one of the smartest and most effective ways for how predators hunt.

Hungry cubs waiting for lunch. Photo by Jon Clark.

Lions are known for their advanced hunting skills and have mastered the art of teamwork in all of their hunting strategies, including chasing, stalking, and ambushing their prey. Embarking on an African safari will be your best chance to experience these master hunters in real life.

Let’s Hope She Doesn’t Have Twins! (A Guest Post)

By Eric VanNatta

Of all the oddball bird species in our world, the brown kiwi surly waddles in amongst the flock. Found only in the forests of New Zealand, this small flightless bird belongs to an ancient group of birds called the ratites. Joined by ostriches, emus, cassowaries and rheas, the ratites are all flightless and dressed in shaggy feathers. In addition, the ratites have all been linked to a common ancestor (simply referred to as the ratite) that was isolated after earth’s continents shifted apart some 300 million years ago.

A size comparison of the moa and kiwi.
Drawing by Josef Korenski (around 1901)
at Wikimedia Commons.

Originally found throughout the single landmass, future generations of ratites living in the places we now call South America, Africa and New Zealand experienced changing climates and new habitat types. Depending on individual traits, certain birds had better or worse success based upon their ability to survive and reproduce. Most of these species developed longer legs used for running and lost their large wings required for flight, as we can clearly see today in the ostrich and emu. In the islands of New Zealand, the ratite developed into a similar group of species we know as the moas. Similar to the emu and ostrich, the moa was a large bird with powerful legs used for running. Eventually, several million years later, the moa, too, continued to take advantage of different habitats within the island in the absence of mammalian predators. Of the handful of new species that the moa gave rise to, one of them actually began to shrink back down in size; we know it as the brown kiwi. Although moas and kiwis were both exceptional at surviving on the island, humans later drove moas to extinction through over hunting during early island colonization.

However, the unique ancestry of brown kiwis is not the only thing that granted them an oddball award. The size of their eggs and their properties is something that has inspired curiosity in us ever since humans discovered the island several hundred years ago.

Size comparison between an kiwi and its egg.
Photo taken by Hannes Grobe at the Kauri Museum in
New Zealand. Available at Wikimedia Commons.

For a bird that can weigh in between 1.5 and 3.3 kilograms (3-7 pounds), brown kiwis’ eggs are a whopping 0.4 kg (almost a pound)! Due to the tremendous size of the eggs, a female kiwi only has room for one egg at a time. On the extreme end, up to 20% of a female’s mass before laying her egg is from her egg. That’s equivalent to a human carrying a 30-pound baby before birth!

So why the heck do kiwis have such massive eggs? What good could this possibly be? Those are two questions William Calder III set out to ask in his research on kiwi eggs.

Before he started answering questions, he compiled many of the characteristics of kiwis and their eggs. In order to look at these differences, he compared kiwis to other bird species of similar mass (seabirds, chickens, etc.), and he compared kiwi eggs to similar sized eggs from other species (emus).


Size comparison between ostrich,
emu, kiwi, and chicken eggs. Photo
by Zureks at Wikimedia Commons.

To start the laundry list of unique observations, the yolk itself is as large as that of an emu, the equivalent of about 11 chicken yolks. This gives a developing chick plenty of nourishment, and upon hatching it still has excess yolk to last 10 days without the need to forage for food. Incubation time for a kiwi egg takes 75-84 days, which is double the amount of time as comparably sized eggs. This has been hypothesized to be a result of lowered incubation temperature, since kiwis have a lower metabolism and body temperature compared to other birds, but there has been no formal investigation of this. The eggs themselves also appear to have an excess of antifungal and antimicrobial properties to endure the 3-month incubation period.

After comparing these characteristics and taking into account their unique ancestry, Calder supported the scientific understanding that kiwis’ large eggs are simply relics from their past. Generations of the moa likely decreased in size after smaller individuals took advantage of eating small prey and living in forest understory habitats. Although these resources allowed for a change to smaller physical size, there was no reason for their eggs to reduce their size. In fact, fossil collections have shown that kiwi eggs are nearly the same size as those from the 12-kilogram (26 pound) moa. Kiwis historically never had to worry about nest predators entering their burrows since there were none on the islands. Their only predators were large flying birds, so it was advantageous to keep chicks in eggs for a longer amount of time until they were more developed. The large yolk reserve also allows chicks to stay hidden during their first days of exploration, and not have to worry about eating.

Talk about an odd reproductive system and a unique lineage! Who knows, maybe future environments will present opportunities for kiwis to increase their number of offspring. As human development encroaches valuable forest ecosystems, it would be beneficial to increase the odds of the species’ survival. Surely any chance of this will take thousands of years of environmental opportunities, as have the changes from their ancestors, but it wouldn’t be the first time the bird has surprised us!


References: Calder, W. (1979). The Kiwi and Egg Design: Evolution as a Package Deal BioScience, 29 (8), 461-467 DOI: 10.2307/1307538

Body Armor is Not Always for Protection

When we see an animal covered in scales and plates, we assume that it has this armor to protect itself from predators. It seems obvious, which is probably why scientists had not really tested it… until now. And they found that it is not necessarily true.

An armadillo girdled lizard has some impressive body armor, but does it do what we think it does?
Image by Handre Basson at Wikimedia Commons.

Today at Accumulating Glitches, I talk about new research on the functions of plates and scales in cordylid lizards. Check it out here.

And to learn more, check this out:

Broeckhoven, C., Diedericks, G. and le Fras Mouton, P. What doesn’t kill you might make you stronger: functional basis for variation in body armour, Journal of Animal Ecology, 84, 1213–1221 (2015). DOI: 10.1111/1365-2656.12414.

Komodo Dragons: Their Bite is Worse than Their Bark (A Guest Post)

By Shelly Sonsalla


Komodo Dragon.
Image by Arturo de Frias Marques on Wikimedia.

Komodo dragons are the world’s largest living lizard and can be found only on select islands in the Indonesian archipelago. These massive lizards can grow to be 10 feet in length and up to 150 pounds! Their natural prey includes wild boars, deer, and water buffalo—animals which may outweigh them by several hundred pounds. So how does a lizard, even such a large one, manage to take down prey so much larger than them? The answer lies in their bite.

Komodo dragons’ mouths are a complex interplay of force, toxins, and bacteria. A study by Brian Fry and his colleagues at the Howard Florey Institute in Australia determined the amount of force that a komodo dragon could generate with its bite. What did they find the answer to be? Not much. They found that a komodo dragon’s bite was 6.5 times less than that of an Australian saltwater crocodile. That’s comparable to a 3.5 pound fennec fox! Obviously, this means that the komodo dragon couldn’t possibly bring down such large prey by strength alone. Luckily for them, there are two more factors at play.


Size comparison between a komodo dragon and a fennec fox.
Computer Rendered by Michelle Sonsalla.

The first is venom secreted by a number of venom glands found on the lower jaw. The amount of venom that can be held in these glands totals less than half a teaspoon! This venom has a number of properties meant to kill its prey, properties which prevent the prey’s blood from coagulating and cause painful cramping in the intestines, paralysis, and loss of consciousness. These effects alone would be enough to bring down most prey, but in case they aren’t, there is a final piece of the puzzle—bacteria.

All living things have a multitude of bacteria and fungi that are naturally present on their skin and in their digestive system, but the bacteria found in the mouths of komodo dragons are specialized. According to Joel Montgomery, a researcher at the University of Texas at Arlington, there are 54 species of bacteria found in the mouths of komodo dragons which cause illness and 1 species which has been found to be lethal to mice. These bacteria enter the prey’s bloodstream through its bite and work to infect the creature slowly, causing severe infection within days or weeks.

All three factors of a komodo dragon’s bite work together to take down its prey efficiently and effectively. The bite, though weak, is enough to open the skin and allow the venom and bacteria into the prey’s bloodstream. Once in the bloodstream, the venom works to weaken the animal, which in turn allows the bacteria to gain a foothold to infect, and eventually kill, the victim. These factors allow this large, magnificent lizard, this dragon among beasts, to take down prey much larger than themselves and have helped them survive the extinction of the past’s other great lizards.


References:

Christiansen P, & Wroe S (2007). Bite forces and evolutionary adaptations to feeding ecology in carnivores. Ecology, 88 (2), 347-58 PMID: 17479753

Fry, B., Wroe, S., Teeuwisse, W., van Osch, M., Moreno, K., Ingle, J., McHenry, C., Ferrara, T., Clausen, P., Scheib, H., Winter, K., Greisman, L., Roelants, K., van der Weerd, L., Clemente, C., Giannakis, E., Hodgson, W., Luz, S., Martelli, P., Krishnasamy, K., Kochva, E., Kwok, H., Scanlon, D., Karas, J., Citron, D., Goldstein, E., Mcnaughtan, J., & Norman, J. (2009). A central role for venom in predation by Varanus komodoensis (Komodo Dragon) and the extinct giant Varanus (Megalania) priscus Proceedings of the National Academy of Sciences, 106 (22), 8969-8974 DOI: 10.1073/pnas.0810883106

Merchant, M., Henry, D., Falconi, R., Muscher, B., & Bryja, J. (2013). Antibacterial activities of serum from the Komodo Dragon (Varanus komodoensis) Microbiology Research, 4 (1) DOI: 10.4081/mr.2013.e4

Montgomery JM, Gillespie D, Sastrawan P, Fredeking TM, & Stewart GL (2002). Aerobic salivary bacteria in wild and captive Komodo dragons. Journal of wildlife diseases, 38 (3), 545-51 PMID: 12238371

Vole Pee: An Epiphany (A Guest Post)

By Nate Kueffer

You’re driving down the road, looking out the window, and you see a large raptor hovering above a field. Have you ever wondered what exactly the raptor could see that you couldn’t? Well, it is thought that raptors may be able to sense ultraviolet light and use it to track voles through urine and feces trails.

A hovering kestrel, possibly tracking a vole. Photo by Mark Likner at Flickr.

Ultraviolet light is a non-detectable form of radiation by the human eye and is similar to X-rays and gamma rays. However, with the help of a black light human eyes can see different materials that we couldn’t see in visible light. The objects that humans can typically see under a black light are fluorescent. This means that the object has the ability to soak up ultraviolet light and then emit the light it took in and produce a light frequency that humans are able to detect.

Jussi Viitala from the University of Jyvaskyla in Finland, and Erkki Korpimäki, Päivi Palokangas (now Lundvall) and Minna Koivula from the University of Turku in Finland set out to find more conclusive evidence on raptors using ultraviolet light to hunt. The four researchers tested the hypothesis that in order to find prey patches, Eurasian kestrels, a species of raptor, look for vole scent marks visible in ultraviolet light. The voles’ scent marks are their urine and feces droppings, which show up under ultraviolet light. The researchers set up experiments in the field and in a laboratory setting.

Kestrel with a captured vole after a successful hunt. Photo by Eugene Beckes at Flickr.

In the laboratory setting, wild captured kestrels were released into a large area made up of four different arenas. All arenas were different, but did not allow any external visual cues. One arena had vole trails in ultraviolet light, another was clean with ultraviolet light, a third arena had visible light and vole trails, and the final arena was clean with visible light. The kestrels were then measured by their time spent over each arena. The kestrels in the laboratory seemed to prefer the arena with ultraviolet light and vole trails. The clean, ultraviolet-lit arena had the least amount of scans and time spent over that arena compared to the other three arenas. The kestrels had no preference over either arena with visible light.

The field setting had 3 experimental groups for 45 kestrel nest boxes: the first had artificial vole trails with urine and feces, the second had artificial vole trails, but no urine or feces, and the last was the control with no vole trails, urine, or feces. The 45 boxes were observed over 24 mornings when the researchers recorded the number of kestrels near each nest and their behavior (hunting, paired, or resting). For the field experiment, 27 of the 45 nest boxes attracted kestrels near them. The most commonly used nest boxes were near artificial trails with urine and feces. The kestrels avoided the other two nest box areas: the one with trails, but no urine, and one with no trails and no urine. This showed that the trails weren’t used as hunting cues. Paired or hunting kestrels preferred to spend time hunting near trails with urine or feces, and resting kestrels were seen evenly in all three areas. Also, four rough-legged hawks were seen hunting near the trails with urine and feces.

Both experiments showed kestrels using trails with markings from voles suggesting that the vole markings may be used to select hunting and nest sites. The researchers propose that the kestrels, in fact, use vole scent markings as visual cues. Kestrels and other predatory birds may use the ultraviolet light from vole markings to scan over large areas new to them before deciding to hunt or nest in the area. The next raptor you see out of your car window could be tracking its prey’s markings using ultraviolet light.


References
Olson, V. (n.d.). Raptor Vision. Retrieved December 10, 2014, from http://www.moremesa.org/wordpress/raptor-vision/

Q & A: Why does a black light make objects glow? (2007, October 22). Retrieved January 21, 2015, from https://van.physics.illinois.edu/qa/listing.php?id=1913

Viitala, J., Korplmäki, E., Palokangas, P., & Koivula, M. (1995). Attraction of kestrels to vole scent marks visible in ultraviolet light Nature, 373 (6513), 425-427 DOI: 10.1038/373425a0

Collective Personality and Our Environment

We are all familiar with the concept of the personality of an individual. We are less familiar with group- or collective personalities (although most teachers can tell you at length about the personalities of each of their classes). The concept is the same: whereas an individual personality relates to an individual’s consistent behaviors across time and contexts, a collective personality relates to a group’s consistent behaviors across time and contexts. Collective personalities can be strongly influenced by the composition and size of the animal group, but also by the environment.


A social spider web by Harvey Barrison at Wikimedia Commons.

This week at Accumulating Glitches I talk about how the environment influences group personalities in social spiders. Check it out here.

And to learn more, check this out:

Modlmeier, A., Forrester, N., & Pruitt, J. (2014). Habitat structure helps guide the emergence of colony-level personality in social spiders Behavioral Ecology and Sociobiology, 68 (12), 1965-1972 DOI: 10.1007/s00265-014-1802-z

Crocodilians Hunt With Tools!

A crocodile lures in birds with sticks that would make a nice nest.
Photo by Dinets published in Ethology, Ecology & Evoluton 2013.

What would happen to mankind if crocodiles and alligators were to develop enough intelligence that they could hunt with tools? Would we see the rise of new dominant species as in Rise of the Planet of the Apes?

Well, shudder in your boots, people, because we are already there!

This week at Accumulating Glitches I talk about the discovery of how at least two species of crocodilians use tools to lure in prey. Check it out here.

And to learn more, check this out:

Dinets, V., Brueggen, J.C.. and Brueggen, J.D. Crocodilians use tools for hunting, Ethology Ecology & Evolution, (2013). DOI: 10.1080/03949370.2013.858276.

Real Zombie-Making Parasites Among Us

The mummified cat and the rat in the crypt of Christ Church in Dublin.
Photo by Adrian Grycuk at Wikimedia Commons.

The Happening, M. Night Shyamalan’s worst panned movie of all time, is a science fiction thriller about people going into a mysterious trance and committing suicide as a result of other mind-hacking species. One of the leading criticisms raised against this movie is the ridiculousness of the premise. One species can’t cause another to willingly commit suicide! …Or can they?

Toxoplasma gondii (we’ll call it T. gondii) is a protozoan parasite that has developed just such mind-hacking abilities! As far as we can tell, T. gondii only reproduces in the digestive tract of cat species, where it lays fertile eggs that are pooped out into the environment. From there, T. gondii eggs can contaminate any number of things that are consumed by other animals, such as rodents, birds, or even humans. When cats eat prey animals that are infected with T. gondii, another generation of parasites is now positioned to reproduce and the cycle continues.

However, prey animals can be pretty good at avoiding cats, in part by avoiding the smell of cats. This is a problem for the reproductive plans of T. gondii. The tiny protozoan has responded to this problem with remarkable biological sophistication: They alter the behavior of their rodent hosts so that the infected rodents find the smell of cat urine so irresistible that they run straight towards their predators! Now, researchers have found that T. gondii-infected rats don’t only like the smell of cat urine, but they even prefer the smell of wild cat urine over the smell of urine of weaker domesticated cats.

A rat checks out odor-soaked papers
in a Y-shaped apparatus. Image from
Kaushik, et al. (2014) in
Integrative and Comparative Biology.

Maya Kaushik, Sarah Knowles and Joanne Webster at the School of Public Heath at the Imperial College of London compared the responses of rats that were either infected with T. gondii or not to urine produced by domestic cats or wild cats. To do this, they put infected or uninfected rats into a Y-shaped apparatus. For each trial, tissue paper soaked in domestic cat urine or wild cat (cheetah or puma) urine was placed in two of the three arms and nothing was placed in the third arm. The researchers then measured how much time the rats spent in each of the three arms and how much they moved.

As expected, the T. gondii-infected rats avoided the cat-urine-soaked arms less than the uninfected rats did. Furthermore, when presented with a choice between arms with wild cat urine versus domestic cat urine, the infected rats (but not the uninfected rats) preferred the smell of the predatory wild cats over the domestic cats! Infected rats also moved more slowly around the wild cat urine compared to domestic cat urine, as if just begging any wild cats that may be around to eat them. It appears that T. gondii have developed a mechanism to turn rats into mindless zombies that practically run into the mouths of the nearest, most vicious cat they can find.

These mind-hacked rat-zombies may not be the only victims of T. gondii. People (particularly those that change their kitties’ litter boxes) can also become infected with the parasite. Some estimates suggest that nearly one-third of all people are already infected! Furthermore, people that test positive for T. gondii infection find the smell of cat urine more attractive than people who test negative! Although we are not likely to run to be eaten by our house-bound kitties, we may be more likely to change the litter box (or get more cats and become a crazy cat lady). So it looks like many of us are mind-hacked zombies too!

Want to know more? Check this out:

Kaushik, M., Knowles, S., & Webster, J. (2014). What Makes a Feline Fatal in Toxoplasma gondii's Fatal Feline Attraction? Infected Rats Choose Wild Cats Integrative and Comparative Biology, 54 (2), 118-128 DOI: 10.1093/icb/icu060

Is That Lizard Possessed!? (A Guest Post)

By Tawny Liebe

Image from Chuck Heston on Flickr.

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


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

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

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

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

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

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

References:

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

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

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

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

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

Caught in My Web: What Your Dog Really Thinks About You, Understanding Gestures, Camera Traps and Pruney Fingers

Image by Luc Viatour at Wikimedia Commons.

This week in Caught in My Web, I share what I found when pondering interactions between humans and animals, what we have learned from camera traps, and what our pruney fingers in the bath may have to teach us about our animal nature.

1. Greg Berns, a psychiatry professor at Emory University, set out to use an fMRI scanner to learn more about what dogs think about their humans. Read his story here at Psychology Today. And check out this video describing The Dog Project:

2. Although dogs may be “man’s best friend”, they have failed numerous tests in understanding our gestures, such as pointing, without training. Even chimpanzees require training before understanding the meaning of human pointing. But elephants are now the first non-human species that seems to innately understand human pointing, naturally investigating objects pointed to (comparable to a 1-year-old human). Jack Flanagan discusses this research at NewScientist.

3. At The Thoughtful Animal, Jason Goldman discusses camera traps (weather-resistant cameras that use motion detection sensors to photograph wildlife) and how they are used in animal research. He also reveals the secret ingredient to luring jaguars to the cameras at You’ll Never Guess How Biologists Lure Jaguars To Camera Traps.

4. While we’re talking about camera traps, Siberian tiger researchers set up camera traps in southeastern Russia. One of their cameras took a series of 3 amazing pictures of a golden eagle attacking a sika deer. Check out the pictures at National Geographic.

5. Ever wonder why your fingers get pruney in the bath? Maybe it is a primate adaptation! Mark Changizi explains why at TEDEd:

Hiding in Plain Sight



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.

Sometimes the best place to hide is right under everybody's nose. If you look like you are innocuous and you belong there, every so often you can get away with trouble.

The bluestriped fangblenny, a coral reef fish in Australia and Indonesia, takes this mimicry strategy to a whole new level. The bluestriped fangblenny doesn't simply look like another species, but it can change its look to resemble any of three different species, depending on who happens to be around! When surrounded by olive-colored damselfish, they take on an olive hue. When surrounded by yellow anthias, they turn orangey-yellow. But their most impressive costume is that of the black and blue striped juvenile cleaner wrasse. And when they are not around a species they mimic, they revert to a brown shade and hide.

This week at Accumulating Glitches I talk about how the bluestriped fangblenny uses mimicry of juvenile cleaner wrasse to sneak up on an bite their predators! Check it out here.

And to learn more, check these out:

1. Cheney, K.L. (2013). Cleaner fish coloration decreases predation risk in aggressive fangblenny mimics Behavioral Ecology, 24 (5), 1161-1165 DOI: 10.1093/beheco/art043

2. Cheney, K.L., Skogh, C., Hart, N.S., & Marshall, N.J. (2009). Mimicry, colour forms and spectral sensitivity of the bluestriped fangblenny, Plagiotremus rhinorhynchos Proceedings of the Royal Society B, 276, 1565-1573 DOI: 10.1098/rspb.2008.1819

Cicadian Rhythms: Why Does The 17-Year Cicada Emerge Like Clockwork?

Does your back yard look like this?
This swarm of periodical cicadas was photographed by Greg Hume at Wikimedia.

The 2013 Swarmageddon is here! After years of their absence, cicadas are overrunning parks, forests and communities all across the central-eastern United States. Periodical cicadas (from the genus Magicicada) are known for their synchronized emergence at 13- and 17-year intervals. Simply the fact that they can live this long is extraordinary: periodical cicadas have the longest life span of all insect species! But their precise 13- and 17-year emergence cycles have long been an evolutionary enigma.

Today I am over at Accumulating Glitches talking about periodical cicadas! I ponder questions like: How do periodical cicadas know when to emerge (and where are they before that)? How did different species living in the same regions get synchronized to the same cycle? And what evolutionary pressures led to life cycles that are precisely 13- and 17-years long?

Check it out here!

And to find out more, check these out:

1. Koenig, W., & Liebhold, A. (2013). Avian Predation Pressure as a Potential Driver of Periodical Cicada Cycle Length The American Naturalist, 181 (1), 145-149 DOI: 10.1086/668596

2. Koenig WD, Ries L, Olsen VB, & Liebhold AM (2011). Avian predators are less abundant during periodical cicada emergences, but why? Ecology, 92 (3), 784-90 PMID: 21608486