Red Squirrel Communication, a Misinterpretation

Red squirrels use alarm calls to warn others when predators are near – no surprise there. Lately, however, a discovery has put these little guys back into the news. The reigning hypothesis used to be that Red Squirrels used different calls, matched to different types of predators. Specifically, Red Squirrels had a tonal sound for aerial predators, and another barking sound for ground danger. However, Dr. Shannon Digweed of Grant MacEwan University in Edmonton, has a completely new take on what those sounds mean.

Digweed first became suspicious of the projection that Red squirrels warn others of danger when she realized they were mostly a solitary species. Red squirrels are loners except for the short period when they are mating with another. If mating is not involved, the squirrels tend to be very aggressive towards each other. She spent many months in the field following individually marked squirrels and recorded every vocal response. She even set up some predator experiments involving taxidermies. All this data concluded that the calls were not just for aerial or ground predators, but for ANY types of disturbances in the squirrel’s immediate area. The tonal sound is to indicate the squirrel is aware of the disturbance, and the bark is to indicate the continued detection of a disturbance. These disturbances can include the presence of other squirrels, non-threatening animals like deer, and actual predators.

Digweed concludes that different call types should not be related to language, ie that they have different meanings aimed toward other conspecifics. Rather, the red squirrel uses the calls to let the disturbance, whatever it may be, know that it has been detected and it is continuing to be detected.

Find the interview with Dr. Shannon Digweed here: http://www.cbc.ca/quirks/archives/09-10/qq-2009-10-31.html#3

Edit:

This study is very new with very new material, so information on how the solitary red squirrel uses alarm calls during mating season is unknown. The same is true of other squirrel species. Simply not enough information has been compiled to state conclusive results.

However, I can tell you that typically, red squirrels mate during February, March, June, and July, and the females typically raise 2 litters a year. Males know when females are in heat because of an odor they generate. A pack of males will chase a female for about and hour, and the female will typically mate with the largest male in the group. I would think that if a cestrus odor is being produced by a female that other red squirrels in the area probably abandon their alarm calls if they know the ‘intruder’ is a possible mate.

Posted by Bethany Rappleyea

If all of your friends jumped off of a bridge, would you follow?

A group of researchers have demonstrated that animals can be just as incapable of making good decisions as humans are. We've all heard of, been witness to, or even participated in extreme cases of social facilitation: consumer frenzy, the mob effect, panicked rushes in human crowds. You've got no idea what everyone is running from, but you're sure as hell getting the **** out of there! Well, this is in part due to what is called an "informational cascade." An individual forsakes the information they have acquired as an individual in order to conform to the decision made by the group because of how many other individuals have adopted this decision.

Informational cascades have been used to explain a variety of phenomena: stock market crashes, stampedes, and even mate choice copying. This particular study, published in the Journal of Behavioral Ecology, has demonstrated how nutmeg mannikins will make foraging decisions against their own better judgement. The birds were given a choice between two types of feeders: one was full of easily accessible, delicious millet seed, while the other had a layer of dried peas on top of the seed, making foraging slower and less efficient. The birds were initially given brief access to both types of feeders so that they would know one was better than the other. However, after watching playback videos of their own buddies preferentially eating from the slower feeder, the vast majority of individuals chose to doubt their personal experience and follow the crowd.

This would be like if you went to the Blue Wall to grab a slice of pizza, and there was one really long line in which every single person was paying with a credit card. Yet, there was another register open and no one was in that line, but you still decided to jump into the long line because that's where everyone else was standing. Lesson learned: your friends are not always smarter than you are.

Persuasive companions can be wrong: the use of misleading social information in nutmeg mannikins

- Posted by Deysha Rivera (final week, hooray!)

Males Have More Personality than Females?!?

So I came across an article that I had to post. It is saying that males have more personality than females. Read on! It states that males have more pronounced personalities in species like humans and even birds. These pronounced traits are what draw females in, like aggression or being daring (which fits nicely with our sexual selection lecture). This study also shows that in most male species, the males show predictable behaviors that relate to parental care even. Females, on the other hand, seem to be less predictable (guilty!). The females, with this unpredictability, have a "choosier" personality upon picking mates (okay, and a lot more...).

The research dates back to 1972 when the Uni. of Exeter looked at gender differences and personality differences (along with sexual selection). They think that the sexual selection drives the personalities. They looked at zebra finches for example: when checking out a new territory, the females would search it out more than the males. The males who were consistent with their exploring were also chosen more as mates (this would mean the males would be consistent with finding food or beating up the predators (or maybe chasing them off).

These scientists really believe that personality is just as important as choosing a male with bright colors or huge...feathers. Could personality really evolve like these other traits? They seem to think so, but what do you think?

-Alyson Paige
(Group 3, last week-finally!)

Hot Honeybees

Honeybees are known for dancing to communicate where a food source is and now it seems they may be able to communicate the quality of nectar or pollen through their body temperature. Nieh and his colleagues found that honeybees who returned to their hive with higher quality pollen, pollen that contains higher levels of protein, had a higher body temperature. The forager is telling the other bees in the hive the net caloric benefit through their temperature so how warm they are tells the other bees the quality of the food. Honeybees are able to use their antennae to sense the temperature of foragers returning to the hive and Nieh tested whether they can actually sense their food through temperature. They found that honeybees are able to identify warmth with their food by training the bees to stick out their tongues for a sugary reward when a warm surface touched their antennae. Next they showed that the bees were able to learn that different temperatures correlated with different food rewards. The honeybees recognized warmer temperature differences much more than they could recognize cold temperature differences. This is likely due to the fact that the center of the flower where they find nectar is 8 degrees Celsius warmer than the outside of the flower. It seems that now not only do honeybees communicate where the food is, but they are able to tell the net caloric benefit through temperature. What do you think they will find out next about communication between honeybees?

-Tara Quist (9)

Feed Me!

Many animals, when they are young, beg to elicit food from their parents. This is commonly seen in birds, but can range throughout various animals. This begging is an interesting trait because it has a conflict of interest between the juvenile and adult: the juvenile gets free food, but at the cost of the adult. Begging eventually stops at a certain age, but the reason why begging stops has been questioned. Three hypothesis were proposed by Madden, et al.: 1) adults stop responding to begging calls, 2) young voluntary switch to foraging from being dependent on the adult, or 3) at a certain time, young cannot produce begging calls. Madden, et al. tested these hypotheses on meerkats, a cooperative breeding animal.

From 2005-2007, free-ranging meerkats were studied in the Kalahari Desert in South Africa by Madden, et al. Playback experiments were used for testing these hypotheses and observations were recorded. They found that adults fed pups more when begging increases, regardless of age. They also discovered that pups stopped producing begging calls that stimulated adult feedings after 100 days. This finding, along with the observation that begging calls changed in structure in age, resulted in a conclusion that hypothesis number three was the most accurate. In many taxa, begging calls change with an increase in age. In meerkats, it was observed that calls become lower in peak frequency due to the growth in body size as age increases.

This finding is important in the study of the evolution of signaling in animal communication systems. With this knowledge, we can now study if the change in begging call characteristics also elicits less feeding by adults in other species.

Madden, J.R., Kunc H.P., English, S., & Clutton-Brock, T.H. (2009) Why do meerkat pups stop begging? Animal Behavior 78:85-89.

Posted by: Christine Rega (Group C, last blogging week)

Speciation in Action

It seems Darwin's finches are making the news again. This time it appears a new species may have emerged. It is a little early to tell but the point of when exactly a new species occurs is not entirely certain.

This news comes from a very famous couple as far as Darwin's finches go, Peter and Rosemary Grant. The Grants have been working closely with Darwin's finches for the past 35 years. The story begins when a very different bird flew into their nets in 1981. This bird was a male medium ground finch, Geospiza fortis, who flew in from a neighboring island. He “was unusually large, especially in beak width, sang an unusual song” and had a few gene variants that could be traced to another finch species, the Grants wrote. This bird found a mate, who also had a few different genes, and they had 5 sons.

All 5 sons were exposed to their father's song during their critical period. Their father had attempted to copy the "local song" but had essentially made his own song in the process. The sons therefore also developed a strange song but nonetheless were able to find mates. Drought struck the island after the family of birds had gone through a couple of generations. Only a brother and sister remained. They mated and their children did the same.

Since then at least 3 generations of reproductive isloation have occurred. The Grant's feel it is now safe to say that these birds can be classified as an emerging species. The main factor in the whole speciation process was that the male sang a different song. The 1 male turned into 5 males with a different song, so on and so forth. Because a male's song has a very prominent effect on female mate choice these birds were quickly reproductively isolated. However the fate of this "species" is not certain. Many factors including, but not limited to, inbreeding depression (founder effect), genetic drift, and natural disasters may have a very negative effect on these birds in the future.

http://www.wired.com/wiredscience/2009/11/speciation-in-action/

- Jillian O'Keefe

In the picture at the top of the article the bird on the left is Daphne Major's native medium ground finch. The bird on the right is the newcomer that came to the island in 1981.

It is hard to determine when a group of "different" birds becomes a "species." This is because many biologists still do not agree on exactly what a species is. Most textbooks follow Ernst Mayr's definition of a species as "groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups" (which integrates the Biological Species Concept). So because the aforementioned finches have been reproductively isolated from Daphne Major's native medium ground finches for a few generations the Grant's feel it is appropriate to call the newcomer finches a species.

Why Can't Chimpanzees Speak?

We’ve all at some point or another wondered why we can speak and our primate cousins can not speak. A study at UCLA may have found a large clue into that mystery. The study reveals that a gene, FOXP2, is directly related to speech in humans. If this gene is damaged or disrupted in humans it causes speech impairments. Early research suggests that FOXP2 changed rapidly in the human brain around the same time that language emerged in modern humans. The study shows that the human and chimp versions of FOXP2 do not look similar and even function differently as well. These findings may provide insight on why humans are born hardwired to speak and chimps are not.

The study has also found that FOXP2 switches other genes on and off. The researchers were surprised to find that the human and chimp forms of FOXP2 produced different effects on gene targets. This finding suggests to the researchers that FOXP2 drives genes to behave differently in humans and chimps. The research demonstrates how mutations could have led to FOXP2’s evolution in humans and chimpanzee brains. These changes between the two species could hold clues as to how the human brain evolved from chimpanzees.

The new information from this study will also help with common speech problems seen in humans like autism. This evidence may eventually lead to new possible drug targets in the brain to help people with autism and give them a way to communicate again.

http://www.sciencedaily.com/releases/2009/11/091111130942.htm

-Sara Ku

Man's best friend serves as model for human social behavior

Chimpanzees may share many of our genes, but dogs have lived with us for so long that they offer a good model for understanding human social behavior. Cooperation, attachment to people, understanding human verbal and non-verbal communications, and the ability to imitate are just a handful of the social behaviors we share with dogs. They might even think like us at times too, according to the paper. While there is no evidence to support that dogs and humans co-evolved their shared behaviors over the past 20,000 years, the researchers believe adapting to the same living conditions may have resulted in the similarities.

In one of many recent studies conducted by the team, Topal and his colleagues taught both a 16-month-old human child and mature dogs to repeat multiple demonstrated actions on verbal command "Do it!" The actions included turning around in circles, vocalizing, jumping up, jumping over a horizontal rod, putting an object into a container, carrying an object to the owner or parent, and pushing a rod to the floor. The dogs "performed at a comparable level to the 16-month-old child," Topal said.

Multiple studies mentioned by the authors also support that dogs exhibit all three primary types of social behavior that humans evolved when they split from chimpanzees 6 million years ago. The first is sociality, or organization into groups where members are loyal to each other and display reduced aggression. The second is synchronization, where following shared social rules and even taking on each others emotions helps to strengthen group unity.The third is constructive activity, where individuals within a group cooperate and communicate with each other to achieve goals. Dogs can also distinguish rational from irrational human communications, Topal said.

The scientists additionally believe dogs are good models for human social behavior because studies can compare and contrast domesticated dogs with wolves, and then with humans.

Posted by Brittany Monteiro

Rethinking Skunk Strategy: Not Just Scent

Many animals, including humans, when they encounter a skunk know that these little creatures pack a powerful punch. Skunks are equipped with several anal scent glands. When the skunk is threatened by a predator, the anal scent glands will release an offensive odor into the environment. This chemical modality sends the message to predators of the skunk’s identity and the message to “stay away if you don’t want to get sprayed”. What other ways do skunks communicate to predators to avoid them all together? A University of California- Davis Professor has discovered that the black and white coloration of the skunk and the size and form assist in predator avoidance. Professor Jennifer Hunter is a wildlife researcher and published her finding in the journal of Behavioral Ecology.
She used stuffed mounts of skunks and foxes to conduct her experiments. Some of the skunks she painted the fur dark gray and the fox fur she dyed black and white similar to the skunk colorations. She then placed the taxidermy mount in locations around California where skunks were common and not as common. At each location she set up infrared video cameras to monitor and record the predator reactions. In the areas where skunks are not commonly found the predators would approach the stuffed animals and take off with the mounts, regardless of coloration or animal. The areas where skunks are abundant, predators would not even approach the mounts. This result shows that the coloration of the skunk and the form are learned by the predators and a clear association is made with the offensive smell from the scent glands. These characteristics send visual message to the passing bear, bobcat, mountain lion or coyote, to avoid this species of animal. So if the sight of a skunk is enough to deter large predators of the west coast, does the skunk have any natural predators? Wildlife researcher, Jennifer Hunter suggests that they probably do not. Think about it, what predator wants to be sprayed in the face with intense musk, and then have to eat a carcass that has the same offensive smell?

Update: Thanks for all the comments, and interest. As for the scent that the stuffed skunks put off was probably very minimal. The researcher was focusing on the effect of the skunk coloration, so she probably made sure that the mounts were free of a scent before the experiments. Chemical signals are able to propagate longer distances so the scent before spraying may deter predators just as effectively as the coloration. In addition it was not mentioned in the article if the different black and white coloration patterns on the skunks had an impact on the predation. Further research has to be conducted on that aspect, and was not included in the article. I have no doubt that the specific coloration's of an individual or of a species of skunk has an equally important impact in communicating to predator "stay away or I will spray"

Emerson Martin
Article: http://www.sciencedaily.com/releases/2009/11/091111092053.htm

Funny Talking Animals - Walk On The Wild Side - Episode Four Preview - BBC One

The Role of Perineuronal Nets and Parvalbumin in Developmental Song Learning

Behavior and neural circuits are shaped during developmental phases known as sensitive or critial periods. During sensitive periods, enhanced nueral plasticity enables environmental factors to shape developing circuits and behavior. Four cellular features characterize the primary visual cortex during the critical period for ocular dominance plasticity. These features are prolonged bursting, expression of the calcium-bindind protein parvalbumin (PV), extracellular matrix perineuronal nets(PNNs), and changes in excitatory-inhibitory balance. PV is characteristic of fast-spiking neurons, typically interneurons. All of these cellular features are related to inhibitory interneurons because GABA neurotransmission decreases the incidence of prolonged bursts.
Prolonged discharge is thought to reflect an immature state of neural circuitry. Increased inhibitory interneuron activity and the presence of PV mark the beginning of experience-dependent plasticity. The presence of PNNs signals the end of the critical period for plasticity in not only vision but other sensory systems as well. Humans and songbirds learn their vocalizations early in life during a two-part sensitive period. This two-part period consists of an early perceptual phase where species-typical sounds are memorized, followed by a later sensorimotor imitative phase where auditory feedback is used to shape emitted sounds.
The song nucleus HVC is the center of auditory and motor pathways of the song system. Recent information from the HVC suggest cellular parallels between the sensorimotor period of the song system and the visual critical period. HVC premotor activity is developmentally regulated and these changes in activity relate to behavior. Like the visual cortex during ocular dominance plasticity, the immature song nucleus HVC exhibits prolonged bursting. In addition, fast-spiking putative interneurons fire before, during, and after song behavior during sensorimotor learning but not later in development.



Posted by Tiffany Mallet

http://www.jneurosci.org/cgi/reprint/29/41/12878

Dinosaurs are hot & sexy... but mostly hot.

In celebration of this being my last blog, I step out of bounds (but only one, teeny, tiny little step) and discuss physiology, a slight divergence from communication. I poured over the sites we have linked and nothing really tickled my fancy as far as communication was concerned.

I'm going to write about dinosaurs. Come on. Who doesn't like them?

If you are at all interested in Dinosaurs... hell, even if you aren't THAT interested, you're in a 500 level bio class about animals, so you may know this anyway... Dinosaurs have been the subject of the hottest debate ever known to man: were they cold blooded or warm blooded?... or, simply creations of some higher power...

Seriously, dinosaurs have been under the scope for a long time. The debate has raged as to whether or not their massive size was fueled by the suns warmth, as in lizards, snakes, and other cold blooded creatures, or by their own ability to regulate body temperature via their own metabolism (warm blooded).

Herman Pontzer, an avid sandal enthusiast and assistant professor of Anthropology at some school called Harvard, did a pretty awesome study that showed Dinosaurs must be warm-blooded. He used a biomechanical model that used the size of animals leg bones based on fossil findings to predict the energy cost of walking and running. And by model, I mean some incredibly awesome math equations that look a little bit like these:

COT (mlO2 kg−1 m−1)
Vmusc (cm3 kg−1 m−1)

In fact, they look EXACTLY like those, because those are the EXACT equations he used. The first is the cost of transport (measured in milliliters of oxygen) and the second is the volume of muscle activated based on the estimated mass of the animal.

The basic idea is that the size of the muscle can reliably relate to the amount of energy that is needed to use it. Since warm blooded animals have a greater aerobic capacity (i.e. their ability to use oxygen as energy) than cold blooded animals, the fact that dinosaurs had larger muscles and thus larger energy requirements would favor the idea that they must have been warm blooded.

The paper cites an awesome study done previously, way back in the day, in 2000, that found a dinosaur fossil that contained a fossilized heart:

Those researchers did a CT scan of the fossilized heart and found a four-chambered, double-pump heart with one aorta:

In case you don't know, or are are a little foggy or something, those heart structures exactly coincide with like... almost every single warm blooded creature on Earth, including us:




















There are few inconsistencies, of course, that keep the debate far from being over. The dinosaur nose lacks a certain structure called the turbinate, which protects against water loss in rapid breathing. This structure is only found in something like 99% of warm blooded animals though, so who really cares, dinosaurs are sweet. They probably had some way cooler method of protecting against water loss anyway. Finally, I guess this paper implies that the cost of walking and running is directly correlated to the dinosaurs size, which a bunch of paleontologists disagree with.

Article

Welp, that's all folks... until I reply to whatever comments I get, which will hopefully be myriad in nature... at which time, THAT will be all, unless you read my blog, which is totally cool and has less rambling.

Alex out.

Comment Replies:

Bethany: That's awesome, and it would have been even funnier if you got shushed by someone. Thank you for the compliments. The reason that some paleontologists disagree with the idea that energy cost and size are related is that, apparently, the two can also be related in cold blooded animals. Some guy that the article mentions says that net cost is "roughly similar" in all vertebrates, cold blooded AND warm blooded, so they still could have been cold blooded.

Jess: Thanks, I think that this is one of the vaguest things to try and answer. I read some discussions online and the whole quarrel is that we haven't found EVERY fossil EVER, so it's impossible to say definitely that all dinosaurs didn't have something similar to a turbinate. Apparently some bird AND dinosaur fossils they found in the Mesozoic have similar structures to the turbinate. Also, there are some warm blooded animals now that do not have the turbinate and manage just fine.

Christine: Thanks, I'm really glad you liked the post. According to what I found, I don't think the four chamber heart would necessarily make them less reptilian. Some reptiles like Crocodiles have four chamber hearts, so I think it just makes them different in that maybe it helped them be better evolved to maintain such large sizes.

Deysha: Right?! When I found out that that asshole Spielberg's representation of a Velociraptor was wrong (and unfortunately way cooler than the Raptors that really existed) I was pretty pissed off. Then the feather thing happened, and I was like... Eh, that kind of sucks... it's still not certain as far as I know that they had feathers, I think it's just an idea and excuse to make different drawings in dinosaur books (if you can prove me wrong here, and evidence has shown that some dinos did have feathers, I'll cry). And THEN, when I found out the Brontosauruses really didn't exist I was even more pissed. Brontosauruses were supposedly another species of dinosaur but really weren't different enough to get labeled as an independent species, so they're really called Apatosauruses, but supposedly they're synonymous out of sympathy for all the Bronty fans.

Crystal: Thanks for the compliments. As for your question, I know what you mean-- tons of birds are descended from dinosaurs, and it's pretty difficult to get the proper discrimination between all of them and their history. Like I said in an earlier reply, not all dinosaur fossils have been found, and especially not with preserved hearts like the one mentioned in my post. This leaves room for a lot of guess work and theorizing as to warm or cold bloodedness and heart anatomy. So I don't think anyone is really able to say that one thing applies to all dinosaurs, but they're just going with what they find.

Alyson: Thanks for the props! I think that what muscles that the flying dinosaurs lacked for running, they probably made up for with their flying muscles. The dinosaurs that flew back then were considerably larger than most birds we know today, so I think their muscle mass and energy demands must have been pretty huge. I couldn't find anything in regards to what animals in present day don't have a turbinate, but I'm on your side. I would guess that they probably are at least more closely related to dinosaurs than other evolved animals today with the turbinate.

Elephants greet their "friends" with a friendly rumble

Joesph Soltis and his team of researchers use collars mounted in elephant's collars to collect vocal data from six female African elephants living in Disney's Animal Kingdom. The difficulty in recording low-frequency calls on wild elephant populations make it difficult to studyshort-distance communication and spontaneously occurring vocal exchanges between individuals. These researchers wanted to determine whether low-frequency vocalizations could help scientist's understand the social context of the calls and whether they are related to reproductive behavior.

There was strong evidence gathered from the vocal data to show females did not randomly produce low-frequency rumbles, but were almost twice as likely to produce a rumble after another group member rumbled. A relationship with another call had an extremely strong impact on vocal response, while dominance rank and reproductive state did not have any affect. Females were much more likely to 'respond' to a rumble made by a partner it had the longest relationship with, compared to those it had not known as long. Elephants also were shown to rumble in certain social contexts; such as when animals were out of contact, when they reunited, or when they were close to each other.

All of this data shows the wide spectrum of uses the African elephants have for their low-frequency rumble call, and this is just the tip of the iceberg. There is a lot of research that still has to be done to help understand the subtle differences and meaning between the different calls, and also to understand the other methods elephants use for communication.

Joesph Soltis, Kirstin Leong, and Anne Savage. "African Elephant Vocal Communication I: antiphonal calling behaviour among affiliated females." Animal Behaviour. 70 (2004):579-587.

FACE TIME

This article(http://www.sciencenews.org/view/generic/id/48171/title/Monkey_moms_and_babies_communicate_from_the_start) talks about how the interactions that macaque mothers have with their newborn infants prepares their offspring with socialization skills later in life. Babies often would iniate an interaction by lip smacking and imitating the mother. They mother would also sometimes try to attract the little monkey's attention by bobbing her heard up and down. The researcher, Ferrari believes that "macaque and human babies share an inborn capacity to communicate using emotional displays and gestures, to share experiences with others and to understand adults’ behaviors as having a purpose."

Check out this really cool video on a one to one mother to child interaction: http://vimeo.com/6966495

Anyways, I found it very interesting that studies that observe mother to infant behavior have been done on humans only about 40 years ago. It would be nice to find out how these interactions play out in other primates and how greatly they influence the offspring.

Posted by Alliam Ortiz

Hilaaaaarious

I Hate Nature from Olde English Comedy on Vimeo.

In all reality, it's not THAT funny, but, whatever.

Jail baits: how and why nymphs mimic adult females of the German cockroach, Blattella germanica

Jail baits: how and why nymphs mimic adult females of the German cockroach, Blattella germanica


At North Carolina State University, the department of entomology has done some extensive
research of the courtship behaviors of the German Cockroach Blattella Germanica. What they
have discovered is that the males perform a “characteristic courtship behavior upon contacting a sexually receptive female.” The males instead of facing the female turn around and open their wings. This exposes the males Tergal Glands. If the females interested she will mount the male and feed upon these glands. These glands can only be accessed when a male thinks he is about to mate. The results of research supports the interpretation that nymphs engage in sexual mimicry to gain access to the male produced nuptial tergal secretions that are only exposed during courtship.


Stephen Chiricosta


http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9W-4X9NCFD-4&_user=1516330&_coverDate=11%2F30%2F2009&_rdoc=11&_fmt=high&_orig=browse&_srch=doc-

New Underwater Glider Spies on the Beaked Whale

A new wave glider, specifically designed for acoustic recordings of beaked whale songs and communication. This computer operated underwater glider, has the battery power to travel from the US to hawaii. It works through an automatic oil bladder that is able to submerge down to 1,000 meters below ocean level. This new depth of sound recording has made it possible to be able to record sound recordings of beaked whales. Beaked whales are one of the more unknown mammals, they are creatures of the deep sea and do most of their feeding at the ocean floor. They are able to unbelievably able dive for 20 to 35 minutes at a time. Their songs emit a distinct three clicks per second which is drastically different than any other marine mammal. Dolphins for example, emit 100 clicks a second. The ability to gather acoustic information on these whales at depths this low was never a possibility until now.

Research for the acoustics of the beaked whales is not the only reason for this research. The fact that there have been numerous reports of beached beaked whales due to military sonar equipment is also under investigation.

The technology to do this kind of research was not available five years ago. Acoustic software and this new underwater glider will lead to many new findings for all marine mammals. The information gained from this research will lead to new findings in whale biology.

Alexandre Bourdois (7)

Animal Communicator...

people actually believe this

-Jackie C

Nice Guys Finish..First?

A study done by Omar Tonsi Eldakar at the University of Arizona Research Laboratories on stream-dwelling water striders (Aquarius remigis) contradicts a popular view that the most sexually aggressive males are most successful in terms of reproduction. He began his study due to the observation that nature is not overrun by ‘hyperagressive males,’ meaning that females must not be choosing for such a trait. Eldakar ended up finding that the less aggressive male water striders actually mated more with females than did the aggressive males.

To come to this conclusion Eldakar simulated the natural environment of water striders, therefore doing away with many of the variables that have lead scientists to false conclusions on this topic. The methods included collecting these insects from the wild during breeding season, categorizing aggressive and non-aggressive males, marking each insect, and observing different combinations of males and females. Six males and six females were used per experiment and all twelve insects were places in a tank of water that was similar to their natural habitat. Behaviors were then observed in all insects present and recorded for each of the experimental trials. When giving the chance to move around, it was observed that female water striders preferred staying in areas with less aggressive males since they would not be harassed. Due to such a location, mating occurred between the female and these more low-key males more often. These results were as expected and coincided with the original observation that most male water striders were not overly aggressive.

As explained by colleagues of Eldakar , this shows that communication between groups is different than communication between two individuals. If put in a circumstance of choosing between aggressive or non-aggressive males, most females would most likely choose an aggressive male, yet in this case, the groups of aggressive males make it too overwhelming for the female.

It is proposed by Eldakar and his co-writer, Pepper, that such selection of the females is due to their perception of the signals communicated by non aggressive males that display cooperation. No follow-up experiments to review this however, were discussed.

The major take-home message in this article, I think, is that evolution and natural selection do not always favor the most brutal, unfriendly adaptations, communications, and behaviors. The real drive of such phenomenon is what works the best for that species in its environment. One more point that I want to highlight is that females are able to process certain behavior cues from males that allow them to make decisions on aggression, such as to say “okay this guy is harassing me, I’m totally walking away…gosh” It would be interesting too, to understand what causes the variations in aggressiveness and maybe to explore the males ability to control such inappropriate acts. Lastly, I would just like to point out one more idea, which I am sure those of you reading have already thought of, but, what does this say about our species? I guess we are still a little behind on evolving ….

Posted by Jackie Connolly ( 3rd post)

Fireflies Use of Bioluminescent Glow to Deter Predators

In the article titled "Hungry Bats Prompt Firefly Flashes" posted on October 29th by Jennifer Viegas on the Discovery News website, she outlines the development of the fireflies glow as a predator deterrent.

Mostly everyone has seen a fireflies glow in the night, specifically in this part of the country where bats, a common predator of the insect world, are of high populous. The hypothesis that was analyzed in Viegas' article was that fireflies actually developed their glowing not only as a mate attractant but it serves a dual purpose of being an anti-predator mechanism.

Fireflies are often toxic to bats. They contain toxins known as lucibufagins. These toxins can cause nausea, vomiting, extreme distaste and in a species of lizard sometimes death. The bat may not know that what he is zeroing in on is a firefly, so instead of the firefly being killed it deters the bat before it even makes the effort through the use of its glow. The firefly often is give a good chance to set his glowing deterrent because often the bat, through echolocation, is unable to snag it's prey on the first try. This gives the opportunity for the firefly to warn the bat before he even tries again.

In a series of research experiments testing this now well accepted hypothesis, bats were offered beetles (their favorite food) that were coated in fireflies, and the bats all refused the meals. In other experiments the bats were presented with lures that would periodically flash the bioluminescent glow, and when the flashing did occur the bats avoided the lure. These experiments helped to prove that fireflies use their bioluminescent glow, not only as a mate attractant but for a mechanism to ware off predators.

This glowing flash in fireflies has now been developed in the firefly as an extremely beneficial aspect. The flash aids them in a reproductive and survival sense helping to maintain the insects futility and survival.

Jessica Abu-Hijleh (7)

Hyena Calls

The spotted hyena is one of the most common carnivores found in Africa. They live in large clans, with rules for cooperation, resource allocation, and young protection. The hierarchy and bonds between hyenas in a clan require sophisticated communication signals.

One of the best known hyena calls is the giggle. It is a high pitched stocatto sound that is produced by a distressed or submissive animal. It occurs when they are in a situation where they are excited and conflicted between approaching and leaving the situation.

One hyena call studied most frequently is the whoop. It is a loud musical call that starts with a very low tone which is modulated up and down in pitch. It is a distance communication call used to announce their presence when they are out of visual contact. Each hyena has its unique whoop, so they can be used for individual recognition.

Hyenas also have a series of softer sounds, like growls and groans, that are used when adults approach each other, and when mothers call their babies out of underground dens. These sounds are often produced in conjunction with complex body language. They are probably used in the different circumstances because they are soothing, not threatening sounds. Through an experiment, it was found that seeing cubs elicited more, acoustically different groans from adult hyenas. More studies need to be done to determine the exact meaning and significance of these softer groans and growls.

Posted by:

Emily Crete

original article can be found at:

http://www.acoustics.org/press/155th/theunissen.htm

edited : 11/14/09

Hungry Bats Prompt Firefly Flashes

We've all heard the phrase "blind as a bat," but fireflies make sure bats see them - and don't eat them. An article by Jennifer Viegas in Discovery News discusses a study about this that was published in Animal Behavior. The study explains that fireflies are toxic to bats, and fireflies advertise this by flashing a "don't eat me" signal at night. The bats see this flashing and know that eating these bugs is a bad idea.

This finding is the first evidence that fireflies flash to deter predators, not just for courtship. In fact, the researchers believe bioluminescence evolved in fireflies as a warning signal, and that bats helped maintain the signal, which later became used for courtship. Paul Moosman, Jr., the lead author of the study, explains that bat echolocation is not as perfect for hunting as it is for finding your way around without bumping into things; therefore, bats may try to eat fireflies if not for the flash.

The researchers examined the fecal pellets of insect-eating bats and found that 80% of the insects consumed were beetles, but very few were fireflies. Then the researchers fed the bats mealworms, with some of the mealworms coated with homogenized fireflies. When the bat's mouths came in contact with the mealworms coated with fireflies, they would cough or shake their heads and rub their snouts.

According to Moosman, one genus of firefly - Photinus - produces toxic compounds called lucibufagins. Another genus of firefly - Photuris sometime try to eat their smaller cousin, Photinus for their lucibufagins, which they could incorporate into their eggs.

The fireflies emit a series of flashes when they sense a predator. This signal is extremely beneficial to both fireflies and bats, and it would be interesting to learn more about its evolution.

http://news.discovery.com/animals/bats-fireflies-flash-poison.html

-Posted by Sarah Benjamin (week 7)

Jamming the Sonar

Read the article here.

Moths are the tasty treat of choice for bats. Usually, there is not much a moth can do to avoid becoming a bat's meal, but there is one moth, the Bertholdia trigona, a species of tiger moth, that has evolved an ingenious strategy to stay alive after being targeted: jam the bat's sonar.

A bat uses his sonar system to locate and catch prey. This tiger moth, however, has found a way to make this system useless. When a moth feels the sonar of a bat, it responds with a series of high-frequency, fast clicks from a pair of structures called "tymbals". This disrupts the bat's echolocation cycle. It unknown exactly how this jamming works. It is hypothesized that the clicks either mask the echoes or blur the acoustic image to hide its exact location. The Bertholdia trigona is the only known species that can disrupt sonar.

This discovery was made using a man-made "bat cave" in which scientists could observe and monitor bat and moth interactions using infrared cameras and by recording high-frequency sounds. The bats and moths were allowed to fly free and interact as they would in nature. The head researcher, William Connor, and his assistant, Aaron Corcoran, say that this is a whole new development in the arms race between prey and predator.

The next step is to observe this behavior in nature. Connor and Corcoran plan on bringing this study to the Chiricahua Mountains of Arizona, where one in three moths is this species of sonar-jamming tiger moth and there is no shortage of hungry bats. They will be studying if evasive maneuvering is also part of this moth's evasion techniques.

-Tricia Carlson (week 7)

Some Chameleons Flash Their Colors to Get a Date

What more dramatic type of visual communication is there than being able to change color? The two most well known animals to utilize this strategy to the extreme are cephalopods (octopus and relatives) and, of course, chameleons. These groups use chromatophores, which are pigment-containing cells in the dermis, to change color. Most animals with this capability use hormones to control the color change. The evolution of chromatophores gives these two groups more direct control over this technique. A chameleon can change its color in milliseconds! Wouldn’t it be useful to be able to disappear into the background when the one person in the room that you don’t want to see you starts to walk your way? Well that is what most people think that chameleons use their color changing abilities to do: camouflage. However, a recent study provides evidence that, at least for the African Dwarf Chameleons, the ability to change color is just a strategy to pick up the ladies.

Devi Stuart-Fox and Adnan Moussalli’s 2008 study, “Selection for Social Signaling Drives the Evolution of Chameleon Colour Change”, used 21 lineages of African Dwarf Chameleons, Bradypodion spp., to test whether the evolution of color change is driven by crypsis (camouflage) or social signaling. They collected data to analyze whether the color change was positively correlated to the chameleons’ background or to the chameleons’ conspicuousness. They measured and quantified coloration, color change reflectance and also took into account what the major predators, mainly birds, would see when the chameleons put on their red carpet best. As we have learned in class in the many many lectures about birds, birds are UV sensitive, (and so are chameleons). Results? The greatest variation of color change was observed in inter-species situations rather than in predator response situations. After all the statistical math was tabulated, they found a positive relationship between color change and conspicuousness and no evidence that color change was related to crypsis. Males use submissive species-specific color signals when they lose a dominance joust with another male and when the female he is courting refuses his advances. The females use light and dark aggressive displays to tell the males to get lost. Surprisingly, the females in this genera do not use this strategy to convey reproductive status as has been shown with other chameleon groups.

Here is a cool link to a site that has some funny cartoons (for sale if you are interested) focusing on chameleon communication:

http://www.cartoonstock.com/directory/c/chameleons.asp

The ones I would’ve liked to post are the 6^th, 7^th and 9^th ones down. The first five don’t even look like chameleons and look like a five year old trying to drawn some unknown generic species of dinosaur and the 9^th one down…what? I’m not sure how this one relates. I went on a bit of a tangent here, my apologies. So, for your pleasure and enjoyment feel free to check it out. I thought it was amusing.

There is always a trade off between being flashy and blending into the surroundings. Although these chameleons aren’t going for the whole master of disguise technique, they have the ability to quickly change color to get their point across, but are not stuck with a flashing old run down diner sign that reads “good eats.”

posted by: Jess Bouchard (1)

Playback experiments in Vervet monkeys

In a vocal recognition study by Seyfarth and Cheney (1980), It was found that vervets recognize not only their own young from others, but can also distinguish whose mother the juveniles scream belongs to. Audio recordings of juvenile screams were played back to free range vervets and other females. It was found:

*Screams of free-ranging juvenile vervet monkeys were played to a group containing their mothers and two ‘control’ females

*Mothers' responses showed significantly shorter latency and longer duration than controls

*Playbacks significantly increased the probability that controls would look at the mother

this article can be found on ScienceDirect and GoogleScholar, entitled: Vocal Recognition in free-ranging vervet monkeys. It was published in Animal Behavior in 1980.

Posted by

-Gina Fortunato

Whale-song Recording Goes Deep

There have been tests before on the recordings that whales make, but not at really low levels of the ocean. They make distinctive sounds in order to look for food and communicate with other males. There has never been the right equipment to explore the ocean at very low levels.


In this article is talks about Melinger and Klincks experiment using a undersea glinder. With the use of the undersea gliner recordings of low levels was accomplished. It can go down as deep at 2,000 meters. The project is funded by the Naval Research. They developed it so they could tell the difference between beaked whales and other ocean sounds. It is steered with an internal computer and pre-programmed course. When it has taken in the data for that certain course it comes to the surface and "beams" a summary of results to a satelite. The two species of whales that they have taken data on are the Cuviers and the Blainville's. It is known that whales click (the sound they make) 3 times per second, compared to a dolphin who clicks 100 times per second. When doing this they look at the rates and the frequency of the sounds. They have not done a detailed analysis yet, but are sure that they haveencountered beaked whales four of five times.

Posted by Samantha Babcock (A)

agressive vocal signaling of spring Peepers (Hyla pseudocris crucifer)

So as it turns out male Spring peepers not only make calls to attract female to mate with, but they also have an aggression call which lets other male frogs know that they are in close proximity with rivaling males that may interfere with one anothers breeding success. The authors of this study believed that the plasticity in signaling was based on social context. Two factors involved in this context were (1) the type of signals produced by new nearby neighbors and (2) the persistence with which new neighbors produced those signal types.


This is interesting when considering how people are usually thought to consider frogs as simple and not able to communicate with each other about differences in their local environment. This study shows that male frogs are able to tell how much competition they have by what kinds of calls are being projected in their local chorus and at what frequency these calls are being displayed in ratio to one another. This goes to show that frogs during mate attracting periods are able to communicate about details that are more than just the attraction of a likely mate.

Context-dependent plasticity of aggressive signalling in a dynamic social environment

Jeremy Ross

I was interested in sharing this article because it is highly relevant to the material we've been covering in lecture. We've moved from talking mostly about proximate questions about animal communication to now learning about ultimate mechanisms in animal communication systems.



Insects make great models for studying the evolution of communication systems for many reasons that include their enormous fecundity, short generation time, and their ability to produce multiple generations of offspring in a single year. Teleogryllus oceanicus is a field cricket from the Hawaiian Islands that uses two mating strategies due to the presence of a phonotactic parasitoid fly that orients to the auditory signals that males use to attract females. Some males however, instead of making calls to attract females, move towards calling males and attempt to intercept the females that are attracted to sound. These satellite males are distinct from the calling males because they have a morphological mutation whereby their sound producing apparatus is non-functional.

Normally such a mutation might be selected against because it would typically inhibit those males carrying that mutation from attracting females. However, silent males move towards the sound of calling which is a behavioral adaptation that accompanies the mutation and probably allows the alleles that code for this morphological mutation to persist in populations of crickets. Scientists from the University of California Riverside have been investigating the relationship between the behaviors of the crickets and the flatwing mutation. They believed that the behavioral adaptation of silent males to move towards calling males (phonotactic satellite behavior) must have evolved previous to the mutation that rendered them unable to produce sound.

This hypothesis was tested by comparing the phonotactic behavior of silent males in the Hawaiian populations to crickets in the ancestral population (Australian islands) that do not coexist with the selection pressure presented by the deadly parasitoid fly. They found that all populations contained individuals with the satellite behavior and that even individuals without the morphological mutation that renders them silent were phonotactic. The authors conjecture that the satellite behavior likely has an adaptive value regardless of whether is it associated with the flatwing mutation.

Tinghitella, R. M. 2008. Rapid evolutionary change in sexual signal: genetic control of the mutation "flatwing" that renders male field crickets (Teleogryllus oceanicus) mute. Heredity 100: 261-267.

Tinghitella, R. M., Jeffery M. Wang and Marlene Zuk. 2009. Prexisting behavior renders a mutation adaptive: flexibility in male phonotaxis behavior and the loss of singing ability in the field cricket Teleogryllus oceanicus. Behavioral Ecology 20 (4): 722-728.

Posted by: Anna Rorkeski

In One Ear and Out the Other

Have you ever been told you have selective hearing? You do (unconsciously)! It has been announced that your right ear is preferable to us when being addressed. Humans are more likely to perform a task when something is requested in our right ear than our left. Three studies were done to test this, looking at ear preference in human communication.

Doctor Luca Tommasi and Daniele Marzoli show that there is a natural bias that shows itself everyday, and this depends on the hemisphere asymmetry of the brain. It is said that the right ear dominance, which reflects the left brain's superiority (in processing verbal stimuli), is one of the best known asymmetries in humans. This has all been observed in lab settings, but never spontaneously "out in the field."

Dr. Tommasi and Marzoli conducted the three studies that looked at communication in a night club setting (which is very noisy). The first study conducted used 286 people in the club, and they observed that over the loud music, 72% of all interactions took place on the right side of the listener. In the second study, they chose 160 people in a club and spoke things that were meaningless and inaudible into their ears. They waited to see if the person would try and turn their head to catch the conversation better. When the person switched or not, they asked if they could have a cigarette. Only the women showed a consistent right-ear preference, but overall, 58% offered their right ear for listening. There wasn't a link to the number of cigarettes gained and the ear hearing the request. The third and final study was conducted with 176 clubbers and asked them right away if they could have a cigarette in their right or left ear. They received more cigaretted when they asked a person in their right ear versus their left. Coincidence?

The authors believe that this is not coincidence that the people were more giving when they heard a request in their right ear. Also, they think that there is definitely a right ear and a left hemisphere advantage when communicating with humans.

Update:

There were some really good questions, and they had me wondering about more things as well too! To clarify the "in the field" comment: they were saying that they had never performed any experiment or test out in the field until that one. Up until then, they had only tested this in a lab setting. I found this a little bit strange because I would have tested it in the field where it would be a lot less expensive and time consuming to see if it was really worth it to test in a lab setting.

A confounding variable to this test would be whether or not people had cigarettes. In my opinion, I would have tested something that more people could have contributed such as tying a shoe. I am also very interested in the idea, that a bunch of you had mentioned, that this may have something to do with handedness, or maybe some people can be left dominant. These are all very interesting ideas, and I do hope they test in the near future.

-Alyson Paige (week 6)

Squid Skin Specializes in Secret Signals

Squid are renowned for their ability to blend effortlessly into just about any substrate the ocean has to offer. They do so with their highly specialized, dual-layered skin. The outer layer is made up of chromatophores (sacs containing colored pigment) which expand and contract to produce the spectacular bursts of color squids are famous for. Squids use this color changing ability to camouflage themselves and to communicate with other conspecifics. The colors produced by the outer layer of skin are clearly visible to the human eye. However, the inner layer of skin is capable of producing polarized iridescent light using specialized cells called iridophores. This light is not only invisible to us, but also invisible to any potential squid predators, such as seals and whales. These signals can be produced without interfering with the outer layer of chromatophores, and allow squids to communicate with each other without revealing their carefully hidden positions.

Here is a link to the interesting article from "Not Exactly Rocket Science."

Posted by - Deysha Rivera

Pollution Exposure to Earthworms Change Starlings Song

It is obvious that pollution has caused artificial changes in the environment. Pollution is causing dramatic changes in Evolution and Ecology. Sewage treatment facilities are an example of how artificial ecosystems develop. Many microorganisms and small insects live in the filter beds of sewage treatments. These organisms are obtaining natural estrogen through human waste and estrogenlike compounds from plastics that build up at filter beds. Exposure to natural and synthetic endocrine disrupting chemicals (EDCs) alters changes in the endocrine systems. According to an article in The New York Times “The chemicals are known to disrupt endocrine function, with anatomical and behavioral effects.”

Shai Markman and Katherine L. Buchanan have researched the European starling (Sturnus vulgaris) in Britain. They have a fully written research article on what they observed. The researchers noticed that the starling mainly feed on worms living in these filter beds. The researchers observed that the birds are highly affected by estrogen (a hormone), dioctylphthalate (toxin), bisphenol A (an organic compound that mimics estrogen), and dibutylphthalate (a toxic air pollutant). The researches captured starling, and in a lab, gave them similar amounts of estrogen and toxins through mealworms introduced with high levels of these toxin and estrogen based compounds. In result, the researchers observed that the starlings’ songs’ became more complex because the part of the brain that produces their song became overdeveloped. The complexity of the male birds’ song attracted more females due to sexual selection. Females favored the male birds with high levels of estrogen over birds that were in a control condition. It may seem as if it is beneficial for mating. However, the starling’s immune system becomes very weak due to the exposure of toxins consumed from the worms. The starling’s reproduction system along with many other internal systems became disrupted and in some cases reproduction systems did not function properly. The researchers predict that the females will continue to mate with the males with poor immune fitness and eventually natural selection will wipe out starling with healthy immune systems. It may be too early to tell but the effects of the artificial ecosystem may cause starling to produce offspring with weaker immune systems thus, decreasing the chances of survival.

Posted by: Carlos A. Varela

A Little Fellatio Goes a Long Way

I’m sure you’ve heard of the common myth that only humans and some monkeys, such as bonobos, have sex for pleasure. If this were true, it would make sense that only these animals would perform oral sex; and up until recently, it was thought that only these animals perform oral sex, with the reasons for this behavior simply being pleasure. However, researchers recently found fellatio behavior in fruit bats, which suggests that there may actually be a biological benefit to such a behavior.

Libiao Zhang and his colleagues at Guangdong Entomological Institute in Guangzhou, China set up cages imitating a bat’s natural habitat. They placed twenty pairs of males and females in the cages and observed their mating behaviors via infrared cameras, which were fed back to the lab. Typical behaviors were observed, but what surprised the researchers most was when the males mounted the females from the back, the females would bend down to lick the male’s penis. Seventy percent of the females in this experiment performed fellatio on the males, suggesting it is a common behavior. Because licking helped to maintain the male’s erection and increased lubrication, fellatio caused prolonged intercourse. On average, every second of fellatio resulted in an extra six seconds of intercourse.

But why would females want to increase length of copulation if they don’t do it for pleasure? Researchers have come up with a few different theories, which all suggest a biological benefit to the individual female. One theory is that it may facilitate the transport of sperm, thus making reproduction more successful. Another theory suggests that it is a way for females to keep the males occupied, and thus prevent them from reproducing with rival females. Due to the antimicrobial properties of saliva, fellatio may also be a way for fruit bats to protect against sexually transmitted diseases; after all, they don’t use condoms.

So fruit bats may not be having sex and performing fellatio for pleasure purposes, but the behaviors are indeed evident, implying that fellatio contributes to more than just a happy male.

Read the full article here

Posted by: Crystal Young (6)

Harmful rays...attractive signal to female spiders.

Ultraviolet rays are dangerous to humans as they can cause skin cancer and damage the retina of the eye. But for spiders of the Phintella vittata species, these rays serve a purpose. According to researchers from the National University of Singapore, male spiders of this species that are able to reflect UVB rays (which are the worst ray types) on their carapace and abdomen have a better chance to mate, as this is an attractive feature that the females look for. Spiders posses complex eyes that are able to detect UVA rays, but whether or not these same UVA receptors are also able to detect UVB rays is unclear. Thus, this study was also able to challenge previous beliefs that animals were not able to see UVB rays due to proteins absorbing the rays at such a high frequency. 

http://www.nytimes.com/2008/05/06/science/06obuvb.html

Posted by Vanessa Raphael

Giraffe Communication

It is not surprising that animals communicate through sound, but Elizabeth von Muggenthaler has found something very special about how giraffes communicate with each other. For many years, animal behaviorists believed giraffes to be the ‘silent parties’ of the animal world. However, advances in technology have allowed scientists to detect sound frequencies outside of human senses. As it turns out, giraffes use low frequency sounds to communicate, much like whales and elephants.

These low-frequency sounds are called ‘infrasound’ and they have an amazing property: to traverse across many miles. In contrast, high-frequency sounds travel a much shorter distance across open air and ground. Studying this type of sound in the field is extremely difficult because background noises can very easily interfere with the recording equipment. Therefore, the bulk of study on giraffe communication has been completed in a zoo or semi-domestic setting. Even in a domestic setting, all data must come from analyzing software – a scientist must depend on a computer, and not on their own observations, to collect data. Muggenthaler is the pioneer in these zoo studies.

As the giraffes are making the low-frequency sounds they tend to stretch out their necks or throw their heads. Muggenthaler seems to think that these behaviors change the way the air moves through the giraffe’s neck. The way a giraffe’s ear is shaped (like a parabola) is perfect for picking up and tuning in on these specialized noises.

To Muggenthaler, the fact that giraffes are not silent has always been obvious. She states, “…here is an animal that is very social, they hide in forests [making visual communication difficult], and they hide their young during the day while foraging. They are hunted by other animals. But they were considered mute. Right there is your clue — there are no animals [that have such behaviors] that are mute. They wouldn’t survive if they couldn’t communicate. “

Communication, even for these giants, is essential for survival.

Read the full article here: http://www.pbs.org/wnet/nature/episodes/tall-blondes/silent-sentinels/2256/

EDIT:

Giraffes use low frequency sounds like elephants and whales. However, elephants and whales both also use sounds that humans can perceive in addition to the infrasound. All three animals need to communicate over long, open distances, and low frequency sounds are best for transmission. Interestingly enough, some behaviorists have suggested the reason many animals fled the asian shoreline before the 2004 tsunami is because of infrasound produced by the incoming tidal waves, so obviously many animals are able to detect low frequency sound, but just not as many use it as their main communication device.

Posted by Bethany Rappleyea