Reindeer Games: 8 Surprising Facts About Reindeer

A reposting of an original article from December, 2017.

A Swedish reindeer watches you. Photo by Alexandre Buisse at Wikimedia Commons.

1. Reindeer are caribou (kinda): Reindeer are the same species as caribou (with the scientific name Rangifer tarandus), but the terms are not completely interchangeable. Rangifer tarandus is a species of deer that is native to Northern regions of Europe, Siberia and North America, which includes many different habitat types, like arctic, subarctic, tundra, snow forest and mountains. These variations in harsh environments have led to variations among populations, resulting in multiple subspecies. The Rangifer tarandus subspecies that live in North America are commonly called caribou and the subspecies that live in Europe and Siberia are commonly called reindeer. We also often refer to domesticated populations as reindeer, regardless of where they are.

A map of reindeer and caribou distributions. Image by TBjornstad at Wikimedia Commons.

2. Rudolf’s red nose was an adaptation: Technically, reindeer don’t have red noses, but they do have lots extra blood flow in them. The inside of their noses are twisted and vascularized so the warm blood can heat up the frigid Arctic air before it gets into the lungs.

3. Santa’s reindeer were probably girls: Not only do reindeer have the biggest antlers of all deer species (relative to body size), but they are the only deer species in which both males and females grow antlers. Both males and females use their antlers to scrape through the snow and look for food, but males also use their antlers to compete with one another and impress the ladies during the breeding season. Unlike horns, antlers shed and regrow every year, and this process is regulated by sex hormones. When the new antlers grow in spring, they are made up of cartilage and lots of blood vessels and are covered in a furry skin called velvet. The blood carries lots of calcium into the antlers, which helps them to grow and harden into bone. When testosterone levels drop in males at the end of their breeding season in early December, their antlers fall off. Females, however, generally keep their antlers until March or April. So, if Santa’s reindeer had antlers at the end of December, they were probably female!

4. If you’re going to pick an animal to travel the world in one night, reindeer are a good choice: Some North American caribou migrate over 3,000 miles a year (more than any other land mammal). They can run up to 50 miles per hour and swim over 6 miles per hour. Migration herds can be up to 500,000 animals and baby reindeer learn to run within two hours of birth!

A swimming caribou herd. Photo by Lestar Kovac at Wikimedia Commons.

5. Reindeer eat weird stuff: Like cows, reindeer are ruminants, which means their stomachs have multiple compartments, some of which specialize in maintaining microbial communities to help them digest. Unlike cows, reindeer predominantly eat lichen, which are combinations of algae and fungi that are typically high in carbohydrates and low in proteins. To make up for this low amount of protein in their diet, reindeer may occasionally eat rodents and bird eggs.

6. They have the coolest feet: Their hooves have four toes: two that splay out like snow shoes and two dew claws. Their hooves have sharp edges to dig for food and are paddle-shaped for swimming. Their hooves even change with the seasons to provide the best traction, being softer in the summer when the ground is soft and hard in the winter to walk on slippery snow and ice.

7. Some reindeer use clicking knees to communicate: Some subspecies have knees that click when tendons slip over bone extensions in their feet. They use this sound to stay with their herd, even when weather conditions limit visibility. But because larger reindeer have larger legs and therefore make louder knee-clicks, they also use these sounds to establish dominance.

8. Reindeer are the only mammals that can see UV light: They have a reflective layer in the back of their eyes that is golden in summer and blue in winter. When it is blue, this allows reindeer to see contrasts in UV light, such as lichen (which absorbs UV) versus snow (which reflects UV).

Reindeer Games: 8 Surprising Facts About Reindeer

A Swedish reindeer watches you. Photo by Alexandre Buisse at Wikimedia Commons.

1. Reindeer are caribou (kinda): Reindeer are the same species as caribou (with the scientific name Rangifer tarandus), but the terms are not completely interchangeable. Rangifer tarandus is a species of deer that is native to Northern regions of Europe, Siberia and North America, which includes many different habitat types, like arctic, subarctic, tundra, snow forest and mountains. These variations in harsh environments have led to variations among populations, resulting in multiple subspecies. The Rangifer tarandus subspecies that live in North America are commonly called caribou and the subspecies that live in Europe and Siberia are commonly called reindeer. We also often refer to domesticated populations as reindeer, regardless of where they are.

A map of reindeer and caribou distributions. Image by TBjornstad at Wikimedia Commons.

2. Rudolf’s red nose was an adaptation: Technically, reindeer don’t have red noses, but they do have lots extra blood flow in them. The inside of their noses are twisted and vascularized so the warm blood can heat up the frigid Arctic air before it gets into the lungs.

3. Santa’s reindeer were probably girls: Not only do reindeer have the biggest antlers of all deer species (relative to body size), but they are the only deer species in which both males and females grow antlers. Both males and females use their antlers to scrape through the snow and look for food, but males also use their antlers to compete with one another and impress the ladies during the breeding season. Unlike horns, antlers shed and regrow every year, and this process is regulated by sex hormones. When the new antlers grow in spring, they are made up of cartilage and lots of blood vessels and are covered in a furry skin called velvet. The blood carries lots of calcium into the antlers, which helps them to grow and harden into bone. When testosterone levels drop in males at the end of their breeding season in early December, their antlers fall off. Females, however, generally keep their antlers until March or April. So, if Santa’s reindeer had antlers at the end of December, they were probably female!

4. If you’re going to pick an animal to travel the world in one night, reindeer are a good choice: Some North American caribou migrate over 3,000 miles a year (more than any other land mammal). They can run up to 50 miles per hour and swim over 6 miles per hour. Migration herds can be up to 500,000 animals and baby reindeer learn to run within two hours of birth!

A swimming caribou herd. Photo by Lestar Kovac at Wikimedia Commons.

5. Reindeer eat weird stuff: Like cows, reindeer are ruminants, which means their stomachs have multiple compartments, some of which specialize in maintaining microbial communities to help them digest. Unlike cows, reindeer predominantly eat lichen, which are combinations of algae and fungi that are typically high in carbohydrates and low in proteins. To make up for this low amount of protein in their diet, reindeer may occasionally eat rodents and bird eggs.

6. They have the coolest feet: Their hooves have four toes: two that splay out like snow shoes and two dew claws. Their hooves have sharp edges to dig for food and are paddle-shaped for swimming. Their hooves even change with the seasons to provide the best traction, being softer in the summer when the ground is soft and hard in the winter to walk on slippery snow and ice.

7. Some reindeer use clicking knees to communicate: Some subspecies have knees that click when tendons slip over bone extensions in their feet. They use this sound to stay with their herd, even when weather conditions limit visibility. But because larger reindeer have larger legs and therefore make louder knee-clicks, they also use these sounds to establish dominance.

8. Reindeer are the only mammals that can see UV light: They have a reflective layer in the back of their eyes that is golden in summer and blue in winter. When it is blue, this allows reindeer to see contrasts in UV light, such as lichen (which absorbs UV) versus snow (which reflects UV).

Fatal Attraction: Praying Mantises (A Guest Post)

By Britta Bibbo

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

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

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

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

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

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

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

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

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

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

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

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

Literature Cited:

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

Why This Horde of Idiots is No Genius

A modified reposting of an article from May, 2012.

At first look (in Part 1 of this post), swarm theory seems to predict that the larger the social group, the better the resulting group decisions and behaviors. Then, with over 300 million of us in the U.S., shouldn’t we only be making brilliant decisions? And with over 7 billion worldwide, shouldn’t we have already prevented all international conflicts, cancer, and environmental destruction?

A riot in Vancouver, Canada after the Vancouver Canucks lost the Stanley Cup
in 2011 left the city with scars. Photo by Elopde at Wikimedia Commons.

Many large groups of people make incredibly stupid decisions. Like proverbial lemmings (a hoax perpetuated by Disney), large groups of people have caused incredible damage to their community after their hockey team lost the Stanley Cup, quit their jobs and given away all of their possessions believing the end of the world was coming on May 21, 2011 (ehem… we’re still here), and insisted that wearing baggy pants around the thighs is a reasonable thing to do even though it is not sexy and it trips you when you try to run. Where are we going wrong?

Tom Seeley at Cornell University has gained tremendous insight into effective group decision-making from his years observing honeybees, which he shares with us in his book, Honeybee Democracy. (By the way, this is also one of the best books out there for painting a picture of the life of a behavioral biologist).

Honeybees live in swarms of thousands. When the hive becomes overcrowded, about a third of the worker bees will stay home to rear a new queen while the old queen and the rest of the hive will leave to begin the process of finding a new home. During this time, the migrants will coalesce on a nearby branch while they search out and decide among new home options. This process can take anywhere from hours to days during which the colony is vulnerable and exposed. But they can’t be too hasty: choosing a new home that is too small or too exposed could be equally deadly.


This homeless honeybee swarm found an unconventional "branch". They'd better
decide on a new home before the cyclist gets back!  Photo by Nino Barbieri at Wikimedia.

Although each swarm has a queen, she plays no role in making this life-or-death decision. Rather, this decision is made by a consensus among 300-500 scout bees that results after an intense “dance-debate”. Then, as a single united swarm, they leave their branch and move into their new home. At this point, it’s critical that the swarm is unified in their choice of home site, because a split-decision runs the risk of creating a chaos in which the one and only queen can be lost and the entire hive will perish. This is a high-stakes decision that honeybees make democratically, efficiently, and amazingly, they almost always make the best possible choice! How do they do that? And how can we do that?



Each dot represents where on the body this dancer
was head-bumped by a dancer for a competing site.
Each time she's bumped, she's a little less
enthusiastic about her own dance. Figure from
Seeley, et al. 2012 paper in Science.

The honeybee house-hunting process has several features that allow them as a group to hone in on the best possible solution. The process begins when a scout discovers a site that has potential for a new home. She returns to her swarm and reports on this site, using a waggle dance that encodes the direction and distance to the site and her estimate of its quality. The longer she dances, the better she perceived the site to be. Other scouts do the same, perhaps visiting the same site or maybe a new one, and they report their findings in dance when they return. More scouts are recruited and the swarm breaks into a dancing frenzy, with many scouts dancing for multiple possible sites. Over time, scouts that are less enthusiastic about their discovered site stop dancing, in part discouraged by dancers for other sites that head-bump them while beeping. Eventually, the dancing scouts are unified in their dance for what is almost always the best site. The swarm warms up their flight muscles, and off they go, in unison to their new home.

What can we learn from this process? Tom has summarized his wisdom gained from observing honeybees in the following:

Tom Seeley’s Five Habits of Highly Effective Hives

1. “Group members share a goal”.
This is easy for honeybees, but not as much for us. All of the honeybees in a swarm share the same goal: Find the best possible home as quickly as possible. People are not always similar in our goals, needs and wants and one person’s goals are sometimes in direct conflict with another person’s goals. The trick here is finding common ground.

2. “Group members search broadly to find possible solutions to the problem”.
Seek out information from as many sources as you can. Be creative. Use your personal experience. And if the group is diverse, there will be a broader range of personal experience to harness. Diversity increases the ability of a group to make the best decisions.

3. “Group members contribute their information freely and honestly”.
This requires a welcoming and supportive environment that withholds judgment of the individuals for the ideas expressed. You don’t have to agree with an idea to respect and listen to the person expressing it.

4. “Group members evaluate the options independently and they vote independently”.
Just as scout bees don’t dance for a site they have not visited and assessed themselves, we should not advocate possible solutions or candidates that we have not ourselves looked into and thought critically about. A group can only be smarter than the individuals in it if the individuals think for themselves.

5. “Group members aggregate their votes fairly”.
Everyone gets a vote and each one counts equally. ‘Nuff said.

We can learn a lot from these honeybees. Even when the stakes are high, we can make good decisions for our group if we are open, honest, inclusive, fair and think independently.


Want to know more? Check these out:

1. Seeley, T., Visscher, P., Schlegel, T., Hogan, P., Franks, N., & Marshall, J. (2011). Stop Signals Provide Cross Inhibition in Collective Decision-Making by Honeybee Swarms Science, 335 (6064), 108-111 DOI: 10.1126/science.1210361

2. List, C., Elsholtz, C., & Seeley, T. (2009). Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honeybee swarms Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1518), 755-762 DOI: 10.1098/rstb.2008.0277

3. Honeybee Democracy by Thomas Seeley

4. The Smart Swarm by Peter Miller

5. The Wisdom of Crowds by James Surowiecki

The Biology of Nagging

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

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

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

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

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

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

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

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

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

Want to know more? Check this out:

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

Miss Behavior’s Picks of 2013



Image from freedigitalphotos.net.

2013 is quickly drawing to a close and we find ourselves in a time of reflection and reminiscences of the last twelve months. Science blogging continues to grow and our many talented and experienced science writers are finding themselves joined by a new cohort of young energetic writers bringing new perspectives. This is an exciting international community of passionate thinkers, debaters, and science communicators. These are my picks for The Top 5 Animal Physiology and Behavior Blog Posts of 2013 (not including The Scorpion and the Frog posts and in no particular order).

On the new blog, Viruses 101, Julia Paoli, a high school student and talented science writer discusses a scientific estimate of how many unknown viruses lurk within our fellow mammals in Mammals Harbor At Least 320,000 Undiscovered Viruses.

Natalie Wolchover at Quanta Magazine pondered the value of partial honesty among animals from a game theory perspective in Hunger Game: Is Honesty Between Animals Always the Best Policy?

We all carry communities of microbes within our bodies that have now been found to be involved in our health and behavior in ways we never previously imagined. In Inspiring Science, Sedeer el-Showk talks about research linking differences in our microbiomes to hormone levels and disease resistance in Sex, Hormones, and the Microbiome.

On EveryONE by PLOS Blogs, Alex Theg tells the story of a jumping spider species that uses multiple deceptive tactics. Read about the spiders that use visual mimicry to trick predator spiders and chemical mimicry to trick predator wasps in Ant-Mimicking Spider Relies on a “Double-Deception” Strategy to Fool Different Audiences.

Felicity Muth discusses animal homosexuality in her blog, Not Bad Science. Check out her article Homosexuality in Female Beetles, and What We Can Learn from It.

Merry Christmas and stay curious!

The Craptastic Conversations of the Black Rhinoceros

What are you saying with your smells? Image by freedigitalphotos.net.

Animals communicate in all kinds of ways: with vocalizations, body language, vibrations, and even odors. In fact, compared to most species, we are pathetic in our abilities to communicate with body odor. With just a whiff of eau de crotch, many animals can decipher that individual’s species, sex, age, health status, reproductive status, emotional state, and dietary history. Some species can go so far as to make out that individual’s exact identity (*Sniff Sniff* Oh! Hi Mike!).

There are a lot of advantages to using odors to communicate. For one thing, messages sent by smell are more likely to be honest than messages sent by other means. (You might be able to do a pretty good Shakira impersonation, but you can’t hide the fact that you had a tuna sandwich for lunch and haven’t brushed your teeth since). Another advantage is that unlike other signal types, an odor signal can be left behind, kind of like those sticky-notes you leave on your food in the fridge.

How do scientists know which species use odors to communicate and what information these signals contain? This investigatory process involves a lot of reasoning.

A solitary black rhino. Photo by John and Karen Hollingsworth
at the US Fish and Wildlife Service.

Wayne Linklater, Katha Mayer and Ron Swaisgood, an international team of researchers associated with Victoria University of Wellington in New Zealand, Nelson Mandela Metropolitan University in South Africa, University of Potsdam in Germany, and the San Diego Zoo Institute for Conservation Research in California, set out to test whether black rhinoceros use odor to communicate. Although rhinos lack the specialized scent glands that many smell-communicating species have, there are many reasons to suggest that they are a likely species to communicate this way.

A photo of field assistant Brayden
Crocker with rhino dung scrape mark.
Photo by Wayne Linklater.

Black rhinos are solitary. Females often have overlapping ranges, but males’ territories only overlap at their boundaries. This means that they would rarely encounter one another and would benefit from a means to leave “sticky-notes” behind to indicate where their territories are. Furthermore, despite their poor eyesight, male black rhinos have a poop-ritual in which they scrape at the ground and spread their dung. Although female rhinos don’t spread their poo, they do spray their pee when they are ready to mate.

Between 2004 and 2006, the Ezemvelo KwaZulu-Natal Wildlife Veterinary and Game-Capture Team captured a number of black rhinoceros from the Ezemvelo KwaZulu-Natal Wildlife Reserves in South Africa in order to relocate them to other reserves for conservation purposes. At this time, Wayne, Katha, and Ron collected dung from rhinos with known sexes and ages. They stored the dung in labeled plastic bags and froze them to preserve the odor freshness for a series of experiments to explore the extent of the black rhinos’ abilities to communicate with their bodily waste.

In one experiment, the researchers asked whether black rhinos could differentiate between the dung of males and females and between the dung of adults and immature subadults. They presented rhinos with the dung of young males, young females, adult males and adult females, and then measured how many times they sniffed each and how long they spent sniffing. The rhinos spent more time sniffing male dung than female dung. This means that rhino poop likely communicates the sex of the pooper. Rhinos also responded differently to adult and subadult poop, suggesting that they can tell whether the pooper is an adult or not.

In order to test whether rhinos may be able to tell the individual identity of the pooper, they did a habituation-dishabituation test. Habituation is when an animal gets used to something that happens repeatedly and stops responding to it. For example, the first time you heard Gangnam Style, you probably stopped what you were doing and maybe even learned the dance. But now it has been so ridiculously over-played that when you hear it, you just ignore it. Dishabituation happens when an animal is exposed to something slightly different and has a heightened response again. Kind of like the excitement over Psy’s new song, Gentleman, even though it sucks.

A photo of rhino performing flehmen, a behavior that helps
waft odors for better odor detection. Photo by Wayne Linklater.

Wayne, Katha, and Ron exposed rhinos to the same individual’s dung three times to see if their interest in it waned. With each presentation, the rhinos spent a little less time sniffing it. When the researchers put poop from a different rhino (that was the same sex and age as the first pooper) in front of them, their interest returned. This suggests that rhinos can tell the individual identity of the pooper from his/her poop.

But can rhinos use their poop like “sticky-notes”? The researchers aged dung for 1, 4, 16 and 32 days and put them in front of rhinos to smell. Their response was the same, no matter how old the dung was. This indicates that rhinos can spread their poop to leave an “I was here” message for at least a month.

As fun as it may be to spend years studying rhinoceros poop, there are some important uses for research like this. Black rhinos are critically endangered, largely due to hunting, poaching and habitat loss. In fact, Mozambique's Limpopo National Park declared the last of their rhino population killed as recently as last month. Conservation efforts such as captive breeding programs and reintroductions have helped in several areas, but have not been enough to sustain the populations. Conservationists could apply this knowledge of how rhinoceros use dung odors to communicate to these breeding and reintroduction efforts in order to make them considerably more successful.


Want to know more? Check this out:

Linklater, W., Mayer, K., & Swaisgood, R. (2013). Chemical signals of age, sex and identity in black rhinoceros Animal Behaviour, 85 (3), 671-677 DOI: 10.1016/j.anbehav.2012.12.034

Political Animals

Now that we are finally on the other side of one of the longest, most expensive political campaign seasons of United States history, we find ourselves with a new mixed-bag of leaders. Our nation’s decision-makers include career politicians and new freshman politicians; they include lawyers, military members, doctors, businessmen, farmers, ministers, educators, scientists, pilots, and entertainers; they include Protestants, Catholics, Jews, Quakers, Mormons, Buddhists and Muslims; they include white Americans, African Americans, Asian Americans, and Hispanic and Latino Americans; they include men and women; they include straight and gay people; and oh yeah, they include Republicans and Democrats. With so many differences that generate so many viewpoints, how will they ever find common ground to make the kind of decisions that will move our nation in a positive direction?

Hey, Look guys! We make a peace sign! Image from Wikimedia.

Research into group decision-making in social animals has shown that ants, fish, birds, and bees have all discovered strategies to make intelligent group decisions. If they can do it, we can do it, right? What can we learn from these critters about harnessing the knowledge in all of us to move our whole group in the best possible direction? We will explore these insights in this post, which is a mash-up of two previous posts. To see the originals, check out Can a Horde of Idiots Be a Genius? and Why This Horde of Idiots Is No Genius.

Jean-Louis Deneubourg, a professor at the Free University of Brussels, and his colleagues tested the abilities of Argentine ants (a common dark-brown ant species) to collectively solve foraging problems. In one of these studies, the ants were provided with a bridge that connected the nest to a food source. This bridge split and fused in two places (like eyeglass frames), but at each split one branch was shorter than the other, resulting in a single shortest-path and multiple longer paths. After a few minutes, explorers crossed the bridge (by a meandering path) and discovered the food. This recruited foragers, each of which chose randomly between the short and the long branch at each split. Then suddenly, the foragers all started to prefer the shortest route. How did they do that?

This figure from the Goss et al 1989 paper in Naturwissemschaften shows (a) the design of a single module, (b) ants scattered on the bridge after 4 minutes (I promise they’re there), and (c) ants mostly on the shortest path after 8 minutes

You can think of it this way: a single individual often tries to make decisions based on the uncertain information available to it. But if you have a group of individuals, they will likely each have information that differs somewhat from the information of others in the group. If they each make a decision based on their own information alone, they will likely result in a number of poor decisions and a few good ones. But if they can each base their decisions on the accumulation of all of the information of the group, they stand a much better chance of making a good decision. The more information accumulated, the more likely they are to make the best possible decision.

In the case of the Argentine ant, the accumulated information takes the form of pheromone trails. Argentine ants lay pheromone trails both when leaving the nest and when returning to the nest. Ants that are lucky enough to take a shorter foraging route return to the nest sooner, increasing the pheromone concentration of the route each way. In this way, shorter routes develop more concentrated pheromone trails faster, which attract more ants, which further increase pheromone concentration of the shortest routes. In this way, an ant colony can make an intelligent decision (take the shortest foraging route) without any individual doing anything more intelligent than following a simple rule (follow the strongest pheromone signal).

Home is where the heart is. Photo of a bee swarm by Tom Seeley

Honeybee colonies also solve complicated tasks with the use of communication. Tom Seeley at Cornell University and his colleagues have investigated the honeybee group decision-making process of finding a new home. When a colony outgrows their hive, hundreds of scouts will go in search of a suitable new home, preferably one that is high off the ground with a south-facing entrance and room to grow. During this time, the house-hunters will coalesce on a nearby branch while they search out and decide among new home options. This process can take anywhere from hours to days during which the colony is vulnerable and exposed. But they can’t be too hasty: choosing a new home that is too small or too exposed could be equally deadly. Although each swarm has a queen, she plays no role in making this life-or-death decision. Rather, this decision is made by a consensus among 300-500 scout bees that results after an intense “dance-debate”.

If a scout finds a good candidate home, she returns to the colony and performs a waggle dance, a dance in which her body position and movements encode the directions to her site and her dancing vigor relates to how awesome she thinks the site is. Some scouts that see her dance may be persuaded to follow her directions and check out the site for themselves, and if impressed, may return to the hive and perform waggle dances too. Or they may follow another scout’s directions to a different site or even strike out on their own. Over time, scouts that are less enthusiastic about their discovered site stop dancing, in part discouraged by dancers for other sites that bump heads with them and beep at them in disagreement. Eventually, the majority of the dancing scouts are all dancing the same vigorous dance. But interestingly, few scouts ever visit more than one site. Better sites simply receive more vigorous “dance-votes” and then attract more scouts to do the same. Like ants in search of a foraging path, the intensity of the collective signal drives the group towards the best decision. Once a quorum is reached, the honeybees leave their branch as a single united swarm and move into their new home, which is almost always the best site. 

Each dot represents where on the body this dancer was head-bumped by a
dancer for a competing site. Each time she's bumped, she's a little less enthusiastic
about her own dance. Figure from Seeley, et al. 2012 paper in Science.

But groups can develop better solutions than individuals even without communication. Gaia Dell’Ariccia at the University of Zurich in Switzerland and her colleagues explored homing pigeon navigation by placing GPS trackers on the backs of pigeons and releasing them from a familiar location either alone or in a group of six. Because they were all trained to fly home from this site, they all found their way home regardless of whether they were alone or in a group. But as a flock, the pigeons left sooner, rested less, flew faster, and took a more direct route than did the same birds when making the trip alone. By averaging the directional tendencies of everyone in the group, they were able to mutually correct the errors of each individual and follow the straightest path.

What can we learn from these examples? Like individual congressmen and senators, in each of these examples each individual has limited and uncertain information, but each individual has information that may be slightly different than their neighbors’. This diversity can be our congress’ greatest asset, if they use it in the same way so many animals naturally do. Tom Seeley summarized these approaches based on his insights from years of watching honeybees:

Tom Seeley’s Five Habits of Highly Effective Hives

1. “Group members share a goal”.
This is easy for honeybees, but not as much for us. All of the honeybees in a swarm share the same goal: Find the best possible home as quickly as possible. People are not always similar in our goals, needs and wants and one person’s goals are sometimes in direct conflict with another person’s goals. The trick here is finding common ground.

2. “Group members search broadly to find possible solutions to the problem”.
Seek out information from as many sources as you can. Be creative. Use your personal experience. And if the group is diverse, there will be a broader range of personal experience to harness. Diversity increases the ability of a group to make the best decisions.

3. “Group members contribute their information freely and honestly”.
This requires a welcoming and supportive environment that withholds judgment of the individuals for the ideas expressed. You don’t have to agree with an idea to respect and listen to the person expressing it.

4. “Group members evaluate the options independently and they vote independently”.
Just as scout bees don’t dance for a site they have not visited and assessed themselves, we should not advocate possible solutions or candidates that we have not ourselves looked into and thought critically about. A group can only be smarter than the individuals in it if the individuals think for themselves.

5. “Group members aggregate their votes fairly”.
Everyone gets a vote and each one counts equally. ‘Nuff said.

We can learn a lot from these honeybees. Even when the stakes are high, we can make good decisions for our group if we are open, honest, inclusive, fair and think independently.

Want to know more? Check these out:

1. Couzin, I. (2009). Collective cognition in animal groups Trends in Cognitive Sciences, 13 (1), 36-43 DOI: 10.1016/j.tics.2008.10.002

2. List, C., Elsholtz, C., & Seeley, T. (2009). Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honeybee swarms Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1518), 755-762 DOI: 10.1098/rstb.2008.0277

3. Seeley, T., Visscher, P., Schlegel, T., Hogan, P., Franks, N., & Marshall, J. (2011). Stop Signals Provide Cross Inhibition in Collective Decision-Making by Honeybee Swarms Science, 335 (6064), 108-111 DOI: 10.1126/science.1210361

4. Dell'Ariccia, G., Dell'Omo, G., Wolfer, D., & Lipp, H. (2008). Flock flying improves pigeons' homing: GPS track analysis of individual flyers versus small groups Animal Behaviour, 76 (4), 1165-1172 DOI: 10.1016/j.anbehav.2008.05.022

5. Honeybee Democracy by Thomas Seeley

6. The Smart Swarm by Peter Miller

7. The Wisdom of Crowds by James Surowiecki

Snakes Deceive to Get a Little Snuggle

A lone red-sided garter snake.
Photo by Tracy Langkilde.

The red-sided garter snake is a small snake species with the largest and most northern distribution of all reptiles in North America. These northern ranges can get quite cold for any animal, let alone a reptile. Like most reptiles, they are ectotherms, meaning they regulate their body temperature largely by exchanging heat with their environment. If an animal gets almost all of its body heat from a cold environment, its body is also going to be cold… So what is a poor red-sided garter snake to do?

Red-sided garter snakes that live in the northern end of their range in Manitoba, Canada spend their cold-season (6-8 months of it) hibernating in underground dens called hibernacula. Tens of thousands of snakes may share a winter den and every spring, they emerge to mate and eat and do all the other fun things that snakes do when they’re awake. (If you would like to witness the spectacular sight that is the emergence of the garter snakes, it is occurring this month in the world-famous snake-watching Interlake region of Manitoba).

A whole lotta red-sided garter snakes in a spring-mating
frenzy. Photo by Tracy Langkilde.

When a snake first emerges from its groggy hibernation state its body is cold and movements are sluggish, which puts it at a high risk of predation from animals like crows and weasels. Females are generally at less risk of predation at this time because emergence-time is also sexy-time for this species and females generally find themselves in the middle of a writhing ball of already-warmed-up male suitors (appropriately called a mating ball). For the female, this both increases her body temperature faster (which will allow her to move faster sooner) and provides any would-be predators with many other snakes to choose from.

Female red-sided garter snakes produce a male-attracting pheromone (a chemical released by an animal that affects the physiology and/or behavior of other individuals of the same species). Researchers Rocky Parker and Robert Mason at Oregon State University found that the amount of pheromone females produce increases as the females hibernate from fall to spring. This pheromone is a blend of saturated and unsaturated methyl ketones (molecules responsible for many natural odors and flavors) and males are more strongly attracted to the unsaturated components. The chemical composition of the female pheromone also changes from fall to spring, such that female spring pheromones are dominated by these highly attractive unsaturated pheromone components. Presumably, the sexier the pheromone, the more suitors are attracted and the more benefits a recently-emerged female can acquire.

It seems that this smell-sexy-and-create-mating-ball strategy is a useful solution for recently-emerged females, but what about recently-emerged males? Parker and Mason collected courting male red-sided garter snakes and brought them into the lab. Then they either implanted them with estrogen (a sex hormone strongly involved in female sexual physiology and behavior) or did not (as a control group). Males with estrogen implants produced more pheromones, had higher ratios of unsaturated pheromone components to saturated pheromone components, and were more attractive to courting males. When the researchers removed the estrogen implants from some of the males, they became less attractive again. So in the lab, estrogen treatment of males makes them produce more female-like pheromones that other courting males respond to. This shows that males are capable of using this smell-sexy-and-create-mating-ball strategy, but do they use it in nature?

This graph shows the amount of courtship
received by females, "she-males", and "he-males"
when either cold or hot. Figure from Shine,
Langkilde and Mason's Behavioral Ecology
and Sociobiology Paper (2012).

Robert Mason at Oregon State University and Rick Shine and Tracy Langkilde at the University of Sydney, Australia collaborated to explore this relationship between temperature and male production of female-like pheromones. It turns out, male red-sided garter snakes in nature can and do produce female-like pheromones when they emerge from their den. Shine, Langkilde and Mason collected some of these males that were being courted by other males (the researchers refer to them as “she-males”). They also collected some males that were courting females (they called them “he-males”) and some females. They then exposed the snakes to different temperatures for 15-minute intervals and tested their attractiveness to other courting males. 

This graph shows the amount of courtship received
by "she-males" when cooled (open circles) and
heated (filled circles) for 15-minute intervals.
Figure from Shine, Langkilde and Mason's Behavioral
Ecology and Sociobiology Paper (2012).

 The researchers found that females were courted the most, “he-males” the least, and “she-males” were courted an intermediate amount. Interestingly, “she-males” only attracted courtship when they were cold (and their chances of survival could be improved by a mating ball) and their attractiveness shifted with every 15-minute shift in temperatures. How did they do this? 15 minutes is probably not enough time for a hormonal change to alter the pheromone composition enough to change attractiveness so drastically.

An important clue comes from the composition of the pheromones themselves. Remember that red-sided garter snake pheromones are a blend of saturated and unsaturated methyl ketones and males are more strongly attracted to pheromones that have a high ratio of unsaturated components to saturated components. Well, saturated and unsaturated fats respond differently to cold: Unsaturated fats (like cooking oil) remain a liquid at cooler temperatures, whereas saturated fats (like margarine) become solid. Solids are less volatile than liquids, which makes them not smell as much. Shine, Langkilde and Mason hypothesize that the ratio of unsaturated to saturated ketones is lower in “she-males” than in females. In the cold, the high amount of saturated components of the “she-male” pheromone is turned off, which raises the ratio of unsaturated to saturated ketones, making them attractive. As the snake warms up, the saturated components of the “she-male” pheromone is turned on, which lowers the ratio of unsaturated to saturated ketones, making them unattractive.

Remarkably, male red-sided garter snakes can change their pheromones to mimic or not mimic females in response to brief changes in temperature. How cool is that?

Want to know more? Check these out:

1. Shine, R., Langkilde, T., & Mason, R. (2012). Facultative pheromonal mimicry in snakes: “she-males” attract courtship only when it is useful Behavioral Ecology and Sociobiology, 66 (5), 691-695 DOI: 10.1007/s00265-012-1317-4

2. Parker, M., & Mason, R. (2012). How to make a sexy snake: estrogen activation of female sex pheromone in male red-sided garter snakes Journal of Experimental Biology, 215 (5), 723-730 DOI: 10.1242/jeb.064923

3. Parker, M., & Mason, R. (2009). Low Temperature Dormancy Affects the Quantity and Quality of the Female Sexual Attractiveness Pheromone in Red-sided Garter Snakes Journal of Chemical Ecology, 35 (10), 1234-1241 DOI: 10.1007/s10886-009-9699-0

4. For an awesome blog about social snakes from a researcher’s perspective, go to http://blog.socialsnakes.org/ (or http://www.public.asu.edu/~mamarell/ for more information)

Why This Horde of Idiots is No Genius

At first look (in Part 1 of this post), swarm theory seems to predict that the larger the social group, the better the resulting group decisions and behaviors. Then, with over 300 million of us in the U.S., shouldn’t we only be making brilliant decisions? And with over 7 billion worldwide, shouldn’t we have already prevented all international conflicts, cancer, and environmental destruction? And why the heck is Snooki still everywhere we look?!

A riot in Vancouver, Canada after the Vancouver Canucks lost the Stanley Cup
in 2011 left the city with scars. Photo by Elopde at Wikimedia Commons.

Many large groups of people make incredibly stupid decisions. Like proverbial lemmings (a hoax perpetuated by Disney), large groups of people have caused incredible damage to their community after their hockey team lost the Stanley Cup, quit their jobs and given away all of their possessions believing the end of the world was coming on May 21, 2011 (ehem… we’re still here), and insisted that wearing baggy pants around the thighs is a reasonable thing to do even though it is not sexy and it trips you when you try to run. Where are we going wrong?

Tom Seeley at Cornell University has gained tremendous insight into effective group decision-making from his years observing honeybees, which he shares with us in his book, Honeybee Democracy. (By the way, this is also one of the best books out there for painting a picture of the life of a behavioral biologist).

Honeybees live in swarms of thousands. When the hive becomes overcrowded, about a third of the worker bees will stay home to rear a new queen while the old queen and the rest of the hive will leave to begin the process of finding a new home. During this time, the migrants will coalesce on a nearby branch while they search out and decide among new home options. This process can take anywhere from hours to days during which the colony is vulnerable and exposed. But they can’t be too hasty: choosing a new home that is too small or too exposed could be equally deadly.


This homeless honeybee swarm found an unconventional "branch". They'd better
decide on a new home before the cyclist gets back!  Photo by Nino Barbieri at Wikimedia.

Although each swarm has a queen, she plays no role in making this life-or-death decision. Rather, this decision is made by a consensus among 300-500 scout bees that results after an intense “dance-debate”. Then, as a single united swarm, they leave their branch and move into their new home. At this point, it’s critical that the swarm is unified in their choice of home site, because a split-decision runs the risk of creating a chaos in which the one and only queen can be lost and the entire hive will perish. This is a high-stakes decision that honeybees make democratically, efficiently, and amazingly, they almost always make the best possible choice! How do they do that? And how can we do that?



Each dot represents where on the body this dancer
was head-bumped by a dancer for a competing site.
Each time she's bumped, she's a little less
enthusiastic about her own dance. Figure from
Seeley, et al. 2012 paper in Science.

The honeybee house-hunting process has several features that allow them as a group to hone in on the best possible solution. The process begins when a scout discovers a site that has potential for a new home. She returns to her swarm and reports on this site, using a waggle dance that encodes the direction and distance to the site and her estimate of its quality. The longer she dances, the better she perceived the site to be. Other scouts do the same, perhaps visiting the same site or maybe a new one, and they report their findings in dance when they return. More scouts are recruited and the swarm breaks into a dancing frenzy, with many scouts dancing for multiple possible sites. Over time, scouts that are less enthusiastic about their discovered site stop dancing, in part discouraged by dancers for other sites that head-bump them while beeping. Eventually, the dancing scouts are unified in their dance for what is almost always the best site. The swarm warms up their flight muscles, and off they go, in unison to their new home.

What can we learn from this process? Tom has summarized his wisdom gained from observing honeybees in the following:

Tom Seeley’s Five Habits of Highly Effective Hives

1. “Group members share a goal”.
This is easy for honeybees, but not as much for us. All of the honeybees in a swarm share the same goal: Find the best possible home as quickly as possible. People are not always similar in our goals, needs and wants and one person’s goals are sometimes in direct conflict with another person’s goals. The trick here is finding common ground.

2. “Group members search broadly to find possible solutions to the problem”.
Seek out information from as many sources as you can. Be creative. Use your personal experience. And if the group is diverse, there will be a broader range of personal experience to harness. Diversity increases the ability of a group to make the best decisions.

3. “Group members contribute their information freely and honestly”.
This requires a welcoming and supportive environment that withholds judgment of the individuals for the ideas expressed. You don’t have to agree with an idea to respect and listen to the person expressing it.

4. “Group members evaluate the options independently and they vote independently”.
Just as scout bees don’t dance for a site they have not visited and assessed themselves, we should not advocate possible solutions or candidates that we have not ourselves looked into and thought critically about. A group can only be smarter than the individuals in it if the individuals think for themselves.

5. “Group members aggregate their votes fairly”.
Everyone gets a vote and each one counts equally. ‘Nuff said.

We can learn a lot from these honeybees. Even when the stakes are high, we can make good decisions for our group if we are open, honest, inclusive, fair and think independently.


Want to know more? Check these out:

1. Seeley, T., Visscher, P., Schlegel, T., Hogan, P., Franks, N., & Marshall, J. (2011). Stop Signals Provide Cross Inhibition in Collective Decision-Making by Honeybee Swarms Science, 335 (6064), 108-111 DOI: 10.1126/science.1210361

2. List, C., Elsholtz, C., & Seeley, T. (2009). Independence and interdependence in collective decision making: an agent-based model of nest-site choice by honeybee swarms Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1518), 755-762 DOI: 10.1098/rstb.2008.0277

3. Honeybee Democracy by Thomas Seeley

4. The Smart Swarm by Peter Miller

5. The Wisdom of Crowds by James Surowiecki