Dominic Couzens: The extraordinary (and overlooked) water shrew

water shrewAsk most people whether they have heard of a water shrew and they’ll shake their head. If you tell them that there are 1.9 million water shrews in Britain and that they have a poisonous bite, then those same people are likely to raise their eyebrows, amazed they have never heard of it. The water shrew (not a water vole or a “water rat”) manages to keep a remarkably low profile for the extraordinary creature that it is.

Shrews are the mammals that look superficially like mice—they are small, brown and furry—yet are quite unrelated to them. They are flatter-bodied than mice and don’t hop, and have long snouts that move around in a somewhat robotic, mechanical fashion as they seek food. With small eyes (they are related to the almost-blind moles) and small ears, shrews lack the features that give mice and voles an easy identity to humankind. Shrews don’t live indoors or steal our food, either; they subsist on a diet of insects and other small living things. So shrews aren’t exactly on our doorsteps, asking to be noticed.

But shrews cross our paths alright, even if we aren’t looking. They are among the most abundant of all our mammals. Aside from the water shrew, there are 42 million common shrews and 8.6 million pygmy shrews in Britain; a veritable army of voracious insect- and worm-guzzlers living at our feet. They prefer to live in long grass, dense shrubbery, and other places where it’s easy to hide.

And, of course, they choose the waterside, too. The water shrew, the largest and best-turned out of our three common species, with its smart white underside contrasting with business-suit-black above, is the most aquatic of the three. Although it is perfectly at home in undergrowth away from water, its signature hunting method is to immerse in still or slow-flowing water, diving down to depths of 2m or more for up to 30 seconds, to snap up crustaceans, insect larvae, snails, worms, and small vertebrates such as newts, frogs, and fish. It is the only British mammal adapted to tap into this underwater niche of small freshwater life.

As it happens, the water shrew can also tackle prey larger than itself, by means of its remarkable venomous saliva, which immobilizes frogs or fish. The venom is a neurotoxin, causing paralysis and disorders of the blood and respiratory system. It is toxic enough to be a very unpleasant skin irritatant in humans that may take days to subside.

The water shrew has several adaptations to its preferred aquatic lifestyle. The surface of each foot is fringed with stiff hairs, increasing the area of the limb, like a flipper, allowing this mite to swim efficiently. The tail also has stiff hairs on the underside, making it act like a rudder, for steering. The hairs on the body also trap a layer of air, keeping the shrew warm underwater, even in the middle of winter.

Shrews, although small, don’t hibernate. Instead they must remain active throughout the winter, requiring a meal at least every two hours, day and night. It isn’t easy to sustain, and many shrews don’t survive. In fact, almost every adult dies after a single breeding season, meaning that only the juveniles born during the spring and summer survive to the next season—just another extraordinary aspect of this overlooked animal’s life.

Dominic Couzens is one of Britain’s best-known wildlife writers. His work appears in numerous magazines, including BBC Wildlife and BBC Countryfile, and his books include Secret Lives of Garden Wildlife and Britain’s Mammals: A Field Guide to the Mammals of Britain and Ireland.

Peter Ungar on Evolution’s Bite

UngarWe carry in our mouths the legacy of our evolution. Our teeth are like living fossils that can be studied and compared to those of our ancestors to teach us how we became human. In Evolution’s Bite, noted paleoanthropologist Peter Ungar brings together for the first time cutting-edge advances in understanding human evolution and climate change with new approaches to uncovering dietary clues from fossil teeth to present a remarkable investigation into the ways that teeth—their shape, chemistry, and wear—reveal how we came to be. Ungar recently took the time to answer some questions about his new book.

Why do paleontologists care so much about teeth? What makes them so special?

PSU: Paleontologists care about teeth because oftentimes, that’s all we’ve got of extinct species to work out details of life in the past. Teeth are essentially ‘ready-made fossils,’ about 96% mineral, so they survive the ages much better than other parts of the body. They are special because they come into direct contact with food, and can provide a bridge to understanding diet in the past. We can tease out the details by studying their size, shape, structure, wear, and chemistry. Teeth connect us to our ancestors, and them to their worlds. I like to think of nature as a giant buffet of sorts. I imagine animals bellying up to the sneeze guard on this biospheric buffet with empty plate in hand. Teeth can teach us about the choices they make; and it’s those choices that help define a species’ place in nature. As the old adage goes, you are what you eat. Teeth are important because they can help us understand relationships between animals in the past and the worlds around them, and about their—and our—evolution.

Why do we have so many problems with our teeth today? Why do we get cavities, require braces, and have impacted wisdom teeth?

PSU: Think about how extraordinary your teeth are. They have to break food, without being broken themselves, up to millions of times over your lifetime. And they have to do it built from the very same raw materials as the foods you are eating. Nature is truly an inspired engineer, and it’s remarkable they last as long and function as well as they do. But they’re not perfect. Most of us today get cavities, and many of us have crooked front teeth, and impacted wisdom teeth. This is largely because of our diets. We eat mostly soft foods, loaded with highly-processed carbohydrates, especially refined sugars. Cavities form by erosion from acids produced by plaque bacteria. Feeding those bacteria diets high in carbohydrates, especially sugars, means more cavities. Also, when we eat soft foods as children, we don’t exercise our jaws enough to stimulate the growth they need to make room for all our teeth. The result is crowded lower incisors, uppers that jut out over the lowers in the front of the mouth, and impacted third molars in the back. It’s not that our teeth are too big for our jaws, it’s that our jaws don’t grow long enough to accommodate all our teeth. Most traditional foragers that eat tougher or harder foods have longer jaws, and so don’t suffer the sorts of orthodontic problems the rest of us have.

Do other species have these problems? If not, why are we so different?

PSU: I’ve seen cavities and evidence for gum disease in some non-human primates, particularly in species that eat a lot of fleshy, sugary fruit, but they’re much rarer than in us. There are very few early human fossils that provide evidence of dental disease in our distant past either. Again, it seems to be a mismatch between our diets today, and the foods that we evolved to eat. Our teeth are not designed for hamburgers and French fries, nor to be bathed in milkshake. If you want to see evidence of that mismatch, just smile and look in a mirror.

What was your motivation for writing a popular science book?

PSU: My PhD dissertation was 654 pages, mostly focused on a quarter of a square millimeter of the surface of some incisor teeth. Most academics are so narrow in their research focus that it can be difficult to see the forest for the trees. I wrote this book to give myself the big picture, to give me an appreciation of the larger context into which my own work fits. Also, no more than half a dozen people actually read my dissertation cover to cover, and that includes my mother. Academics often feel like they’re speaking, but no one is listening. I wanted to reach a larger audience. This book at first glance seems to be about teeth – but it’s really about the biospheric buffet, and how environmental change over deep time swapped out items and choices available to our distant ancestors. The take-home message is that large-scale climate swings winnowed out the pickier eaters among us, and drove our evolution. Teeth are our window through which to see it. The most important message here is that climate changes, and species have to change to accommodate or die. That’s why we’re here. It’s a timely, important lesson.

As a scientist who has spent the last three decades studying evidence for the evolution of human diet, what do you think of today’s “Paleolithic diet” trend? And what was the ancestral human diet, anyway?

PSU: I’m not a fan. I like pizza and bagels too much. Still, there’s little doubt that our ancestors did not eat such things; so it makes sense that a discordance between the foods we evolved to consume and what we fuel ourselves with today can wreak havoc on our bodies. Try putting diesel in a car built to run on regular gasoline (actually, don’t). And people do lose weight when they cut refined carbohydrates and processed sugars from their diets. We could well benefit from eating more like our Stone Age ancestors, with menus like those in some popular diet books—you know, spinach salads with avocado, walnuts, diced turkey and the like. I am not a nutritionist, and cannot speak with authority about the nutritional costs of benefits of Paleolithic diets—but I can address their evolutionary underpinnings. Think about it this way. Any diet that drains the body of fat reserves means not meeting daily caloric needs. It is difficult to believe that nature would select for us to eat only foods that don’t provide the nutrients required to maintain the body. In fact, the whole idea of the Paleolithic diet is problematic. Even if we could (and we can’t) reconstruct the glycemic load, fatty acid, macro- and micronutrient composition, acid/base balance, sodium/potassium ratio, and fiber content of foods eaten at a moment in time in the past, the information would be meaningless for planning a menu. All these nutrients varied with food availability over space and time, as items on the biospheric buffet table were swapped in and out, so focusing on a single point in our evolution is futile. We’ve been a work in progress for millions of years. What was the ancestral human diet? The question itself makes no sense.

Peter S. Ungar is Distinguished Professor and director of the Environmental Dynamics Program at the University of Arkansas. He is the author of Teeth: A Very Short IntroductionMammal Teeth: Origin, Evolution, and Diversity and Evolution’s Bite: A Story of Teeth, Diet, and Human Origins.

A giveaway for the Kentucky Derby

Horses of the World by Élise Rousseau and illustrated by Yann Le Bris is a beautiful, detailed guide to the world’s horses. It covers, for the first time ever, all 570 breeds of domestic and extant wild horses, including hybrids between the two and between domestic breeds and other equids, such as zebras. In honor of the Kentucky Derby coming up on Saturday, May 6, we’re giving away five copies via Goodreads. Enter for a chance to win this must-have guide for all the horse-lovers out there.

 

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Élise Rousseau is a freelance writer and author of a number of adult and children’s books on horses. She is an avid equestrian and has traveled all over the world to document rare breeds. Yann Le Bris has been a professional artist for eighteen years and has illustrated numerous books.

 

Anurag Agrawal: Monarchs vs. Milkweed

by Anurag Agrawal

Coevolution is a special kind of evolution. And monarchs and milkweeds exemplify this special process. In particular, what makes coevolution special is reciprocity. In other words, coevolution is one species that evolves in response to the other, and the other species evolves in response to the first. Thus, it is a back-and-forth that has the potential to spiral out of control. In some arms races, the two organisms both benefit, such as that between some pollinators and flowering plants. But coevolution is more common among antagonists, like predators and their prey.

When biologists first described coevolution, they likened it to an arms race. An arms race, such as that between political entities, occurs when two nations reciprocally increase their armament in response to each other. So how does an arms race between monarchs and milkweeds, or between cats and mice, or between lions and wildebeest, or between plants and their pathogenic fungi, proceed? When coevolution occurs, it proceeds with “defense” and “counter defense.” And one of the few rules of coevolution is that for every defense that a plant or prey mounts, the predator mounts a counter defense, or an exploitative strategy to overcome the defense.

Once a monarch butterfly lays an egg on a milkweed plant, the natural history of coevolution unfolds. For every defense that the plant mounts, milkweed mounts a counter defense. Once the caterpillar hatches, it must contend with a bed of dense hairs that are a barrier to consumption of the leaf. But monarchs are patient, and have coevolved with the milkweed. So their first strategy is to shave that bed of hairs such that the caterpillar has access to the leaves that lie beneath.

Agrawal

For every defense there’s a counter defense. But next, when the monarch caterpillar sinks its mandibles into the milkweed leaf, it encounters a sticky, poisonous liquid called latex. In this video we will see how the monarch caterpillar deactivates the latex bomb that the milkweed puts forward.

And so the arms race continues, with reciprocal natural selection resulting in coevolution between monarchs and milkweeds. In my book, Monarchs and Milkweed, I outline the third level of defense and counter defense between these two enemies. Milkweed next mounts a remarkable and highly toxic defense chemical called a cardiac glycoside. But, yes, again the Monarch has evolved the means to not only not be poisoned by the cardiac glycoside, but to sequester it away and put it to work in defense of the Monarch itself from its enemies, such as predatory birds. For more on the Monarch – Milkweed arms race see this video, filmed in Ithaca, New York outside of Cornell University where we conduct our research.

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

Celebration of Science: A reading list

This Earth Day 2017, Princeton University Press is celebrating science in all its forms. From ecology to psychology, astronomy to earth sciences, we are proud to publish books at the highest standards of scholarship, bringing the best work of scientists to a global audience. We all benefit when scientists are given the space to conduct their research and push the boundaries of the human store of knowledge further. Read on for a list of essential reading from some of the esteemed scientists who have published with Princeton University Press.

The Usefulness of Useless Knowledge
Abraham Flexner and Robbert Dijkgraaf

Use

The Serengeti Rules
Sean B. Carroll

Carroll

Honeybee Democracy
Thomas D. Seeley

Seeley

Silent Sparks
Sara Lewis

Lewis

Where the River Flows
Sean W. Fleming

Fleming

How to Clone a Mammoth
Beth Shapiro

Shapiro

The Future of the Brain
Gary Marcus & Jeremy Freeman

Brain

Searching for the Oldest Stars
Anna Frebel

Frebel

Climate Shock
Gernot Wagner & Martin L. Weitzman

Climate

Welcome to the Universe
Neil DeGrasse Tyson, Michael A. Strauss, and J. Richard Gott

Universe

The New Ecology
Oswald J. Schmitz

Schmitz

Oswald Schmitz: Reflecting on Hope for Life in the Anthropocene

This post by Oswald Schmitz, author of The New Ecology, was originally published on the March for Science blog. On April 22, PUP’s Physical and Computer Sciences editor Eric Henney will be participating in a teach-in the National Mall, focusing on the social value of direct and engaging scientific communication with the public. 

Springtime is a welcome reprieve from a prolonged cold winter. It is a time of reawakening when all kinds of species become impatient to get on with their business of living. We hear the trill of mating frogs, see leaves unfurl from their quiescent buds, and behold forest floors and fields unfold rich color from a dizzying variety of blossoming wildflowers. The energetic pace of life is palpable. It is only fitting, then, that we dedicate one spring day each year – Earth Day – to commemorate the amazing variety of life on this planet, and to take stock of the human enterprise and reflect on how our behavior toward nature is influencing its sustainability.

For many, such reflection breeds anxiety. We are entering a new time in Earth’s history—the Anthropocene—in which humans are transitioning from being one among millions of species to a species that can single-handedly determine the fate of all life on Earth. Many see the Anthropocene as a specter of doom, fraught with widespread species extinctions and loss of global sustainability, and attributable to humankind’s insatiable drive to exploit nature.

This view stems from the conventional idea that all living beings on Earth represent a heritage of slow evolutionary processes that occurred over millennia, culminating in the delicate balance of nature we see today. Many despair that humans are now jeopardizing the balance, as species will necessarily be incapable of coping with the onslaught of ever-new and fast-paced changes.

Iguana

An Aegean Wall Lizard, so named because of its evolved habit to live and hunt in rock walls constructed around crop fields in Greece. Individuals living on the walls have different limb morphology and mobility than counterparts of their species that are found within their original sandy habitats, demonstrating their capacity to adapt and thrive in human developed landscapes. Photo courtesy of Colin Donihue.

As an ecologist, I am torn by the changes I see. I have a deep and abiding respect for the amazing diversity of living organisms, their habits and their habitats. This ethic was shaped during my childhood when I was free to wander the natural environs of my hometown. I could go to those places any time of day, during any season: breathing, smelling, listening, observing, touching and tasting to discover nature’s wonders. That sense of wonder has endured. It’s what keeps me asking the probing questions that let me learn scientifically how species fit together to build up and sustain nature. It thus saddens—sometimes even maddens—me to see nature’s transformation in the name of human “progress.”

But as a scientist, I must admit that these changes are also fascinating. It turns out that rapid human-caused changes present much opportunity for new scientific discoveries. They force me to see and appreciate the dynamism of nature from fundamentally new vantage points. I find that nature can be more resilient than we often give it credit for, a fact that should inspire hope for a bright, sustainable environmental future in the Anthropocene.

Changing the mindset from despair to hope requires letting go of a deeply held notion that nature exists in a fragile balance, and that humankind has a persistent habit of disrupting that balance. Nature is perpetually changeable, with or without human presence. Life’s energetic pace, and the primal drive of all organisms to survive and reproduce, is what builds resilience in the face of change. We are learning how nutrients are perpetually transformed and redistributed by plant and animal species to sustain myriad ecological functions. These functions ensure that we have ample clean and fresh water, deep and fertile soils, genetic variety to produce hardy crops, the means to pollinate those crops, and the capacity to mitigate impacts of gaseous emissions, among numerous other services that humans rely on to sustain their health and livelihoods. Many species also can rapidly acclimate and even evolve within a mere span of a couple of human generations to cope with significant and rapid environmental change. Such adaptability allows many ecological systems to recover from human-caused disturbances and damages within the short time span of a human lifetime, no less.

This capacity for resilience is perhaps our most important evolutionary heritage. It is what gives hope for a sustainable future. The challenge of sustainability, then, is to engage with nature without eroding this capacity. The emerging science-based ethic of earth environmental stewardship can help on this front. It sees humans and nature entwined, where humans have obligations to one another mediated through their mutual relationships with nature.

Earth environmental stewardship strives to sustain nature’s resilience by protecting the evolutionary and ecological interdependence of all living beings and the physical environment. It strives for continuous improvement of environmental performance and human wellbeing through a commitment to use nature’s resources wisely and efficiently as dividends of resilient ecosystem functions. This means protecting entire ecosystems, not just their parts, and ensuring the development of sensible environmental policies and regulations to ensure that ecosystem services benefit all living beings now and in the future.

Effective earth environmental stewardship requires that we take deliberate interest in becoming scientifically informed about how our needs and wants are linked to our local environment and the larger world beyond. So on this Earth Day, it is perhaps fitting to reflect on and celebrate our amazing scientific achievements to understand the durability of nature and the wealth of opportunity it offers for a sustainable future in the Anthropocene.

Oswald J. Schmitz is the Oastler Professor of Population and Community Ecology in the School of Forestry and Environmental Studies at Yale University. His books include Resolving Ecosystem Complexity and The New Ecology: Rethinking a Science for the Anthropocene.

Celebrate Sophie Glovier’s new book with a geocaching adventure around Princeton

Glovier

Walk the Trails in and around Princeton by Sophie Glovier is an attractive, pocket-friendly guide to walks on sixteen of the best trails through preserved open space in Princeton, New Jersey and its neighboring towns. The guide includes detailed color maps of the trails, directions on how to get to them and where to park, recommendations for the most scenic routes, and more.

To celebrate the arrival of spring trail-walking weather and the book’s release, we’ve geocached four copies of the book in hidden locations on the trails. Using the coordinates and clues we’ll be posting to Instagram, Twitter, and Facebook in the coming days, we invite you to lace up your hiking boots and use your skills to find them. Be sure to exercise caution when venturing off the beaten path!

The four geocaches are hidden on the following trails:

The Poetry Trail (Trail 3 in Walk the Trails)

Greenway Meadows along the Stony Brook (Trail 4 in Walk the Trails)

Princeton Battlefield (Trail 5 in Walk the Trails)

Updike Farmstead in Washington’s Footsteps (Trail 6 in Walk the Trails)

Once you find the geocache, feel free to take the book but please leave the box. Use the notebook and pen to write your name, the date, the time, and the condition of the box. Feel free to take a trinket or leave one. Please secure the top and place the box where you found it. If you can’t find the box or if you find it and there is no longer a copy of the book inside, let us know on Instagram, Twitter, or Facebook using the hashtag #PUPTrails. When searching for the geocaches, please be careful with the wildlife, including plants and trees.

Clues for the first geocache on The Poetry Trail will be posted to social media tomorrow morning. Good luck and happy hunting!

Anurag Agrawal: The oldest butterflies?

by Anurag Agrawal

It’s unclear when humans became humans. Presumably it was a gradual growth of our consciousness over the eons. There are some things, however, that appear to distinguish us from most other animals. For example, our artistic depictions. From the deepest, darkest caves have emerged pictures of humanity from thousands of years ago. And in an Egyptian tomb, that of Nebamun, on a painting called “Fowling in the marshes” (from around 1350 BCE) comes one of the oldest human depictions of butterflies. It happens to be of the African Monarch, Danaus chrysippus, sometimes called the plain tiger, a close relative of our beloved North American Monarch butterfly, Danaus plexippus.

Agrawal
I stumbled on this lovely scrap of history when a friend and colleague, Harry Greene, gifted me a book: Nabokov’s Butterflies (2000), a collection of unpublished and uncollected writings. Some explanation is in order. Harry is an extraordinary naturalist and big thinker in ecology and evolution. Like many senior scholars, his predicament was the lack of shelf-space in his office. And so I was the beneficiary of Nabokov’s Butterflies. Vladimir Nabokov, a Russian-American author, and noted entomologist, was most famous for his writings, for example, Lolita, and his celebrated translation of Pushkin’s novel in verse, Eugene Onegin. His ideas about biology were diverse, he was a passionate lepidopterist, and he often intermixed his literary writing and entomological excursions. Lolita is said to have been written primarily on butterfly collecting trips in the American west. Nonetheless, Nabokov also clung on to other ideas that held little merit in the scientific sphere. Most prominently, Nabokov rejected evolution by natural selection as a driver of certain organismal traits that he deemed ‘coincidental, miraculous, or too luxurious.’

Agrawal

Nabokov was a professor at my own Cornell University in the decade following WWII. Although he taught literature and had well-known students at Cornell (including U.S. supreme court justice, Ruth Bader Ginsburg), his entomological interests continued. In fact, after he retired from Cornell in the mid-1960s, Nabokov had sketched out an outline of a book: The Butterflies of Europe. And although the book never came to be, the outline was recapitulated in Nabokov’s Butterflies. Flipping through the book, I stumbled on his entry for Danaus in which he wrote, “This butterfly has the distinction of being the oldest known to have been represented by man. Seven specimens of it (with typical white-dotted Danaus body but somewhat Vanessa cardui like wingtips) are shown flitting over the papyrus swamp…” (page 603).

Agrawal
I later asked another friend, Harvard’s Lepidopterist, Naomi Pierce: did Nabokov have it right? On the money, she independently pointed to the similarity of Danaus chrysippus and the painted lady, Vanessa cardui, wondering if the butterflies on this three thousand year old tomb painting were Danaus or Vanessa. She concluded, as did Nabokov, that the African Monarch ruled. Detailed assessment of the color patterns on the wings were informative to both entomologists. The oldest human depiction of a butterfly? Perhaps not. Naomi mentioned some evidence of butterflies in Minoan artifacts from Crete, a thousand years earlier than Nebamun, and likely in Pyrenees cave paintings, some 10-30 thousand years earlier!

Of course, there is nothing special about being the oldest depiction of a butterfly by Homo sapiens. But suffice it to say, butterflies, metamorphosis, wing patterning, and the beauty of nature have been on our minds for a very long time. Thanks Harry and Naomi! And thanks Nabokov. Who knows what becomes of those side hobbies and obsessions we all hold.

Nabokov

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

A sneak peek at BIG PACIFIC, companion to upcoming PBS series

The companion five-part series on PBS: Big Pacific will air Wednesdays on PBS, June 21-July 19, 2017

The Pacific Ocean covers one-third of Earth’s surface—more than all of the planet’s landmasses combined. It contains half of the world’s water, hides its deepest places, and is home to some of the most dazzling creatures known to science. The companion book to the spectacular five-part series on PBS produced by Natural History New Zealand, Big Pacific by Rebecca Tansley breaks the boundaries between land and sea to present the Pacific Ocean and its inhabitants as you have never seen them before.

Illustrated in full color throughout, Big Pacific blends a wealth of stunning Ultra HD images with spellbinding storytelling to take you into a realm teeming with exotic life rarely witnessed up close—until now. Providing an unparalleled look at a diverse range of species, locations, and natural phenomena, Big Pacific is truly an epic excursion to one of the world’s last great frontiers. Take a sneak peek here:

 

 

Anurag Agrawal: The migration patterns of the monarch butterfly

by Anurag Agrawal

The plight of monarch butterflies if often in the news: many scientists around the world are working hard to understand their annual migratory cycle. How do the monarchs produced during summer in the northern reaches of America contribute to the overwintering population in Mexico? The origin of monarch butterflies that make it to Mexico has been hotly debated because it has profound consequences for how we approach monarch conservation.

A new study is remarkable in its use of historical collections over the past 40 years and modern isotopic analysis. The scientists address the most important regions in the U.S. for producing monarch butterflies that actually make it to Mexico. This sort of data has been very difficult to come by and there has been a lot of speculation. As outlined in my new book from Princeton, the midwest has dominated discussions as being the most important region in the U.S. for monarchs. In the study, the authors find that the Midwest contributes a whopping 38% of the butterflies that make it to Mexico.

Monarchs

The regions studied by Flockhart et al. separated to highlight their relative areas

I would add two points for discussion. The first is that the areas of land that the authors designated as Midwest, Northeast, etc., seemed totally reasonable, but also somewhat arbitrary. In particular, an issue arises when you consider that, as designated in the paper, the Midwest is about 2.5 times as big as the Northeast. It is therefore not surprising that the Midwest produces about 2.5 times as many butterflies that make it to Mexico (38% vs 15%). In other words, the butterflies that make it to Mexico have about an equal probability of coming from the Midwest and the Northeast when land area is considered. Yet another way to think about this is that two states that are about equal sizes in the two regions (for example, Indiana and Maine) will on average produce about the same number of butterflies that make it to Mexico.

Monarch2

The annual migratory cycle of the monarch butterfly from Monarchs and Milkweed. In my past research, we have opted for a three simple regions defined by the butterfly generations.

Quite interestingly, the North Central area (including my home in the Finger Lakes region of NY) is slightly more important for butterfly production given its size. When you factor out the area of the Great Lakes (where there are no monarch caterpillars), the area of North Central is small (36% of the size of the Midwest). Thus, about 20% more butterflies per square mile come out of the North Central than the Midwest or Northeast. Where does this leave us?  The agricultural Midwest is certainly important, but perhaps not as important as previously thought.

The other point worth thinking about is that the Southwest (read: Texas) comes out as big in terms of area (equal to the Midwest) and relatively less important in terms of contributing butterflies (11% of the total).  The critical importance of the Gulf States including Texas, however, is not in the last generation of butterflies produced in fall that migrate south, but rather in the first generation of butterflies that are produced in spring and that migrate north to the Midwest and Northeast.  In other words, the Gulf States are absolutely critical for the annual migratory cycle, even if that is not where fall migrants are produced.  Without a spring generation there, the Midwest and Northeast would be empty!  In chapter 9 of the book, I summarize the critical importance of Gulf States not only for the spring, but also in providing floral resources for fall migrating butterflies.

I hope we see more studies like this in the future, as it provides new important information and was inspiring to read.

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

Anurag Agrawal: Monarch overwintering

by Anurag Agrawal

The estimates of the monarch butterfly overwintering population were announced February 9th by WWF Mexico. The butterflies are so dense at their dozen or so mountain-top clustering sites that overwintering butterflies cannot be individually counted. Instead, the area of forest that is densely coated with butterflies (at about 5,000 butterflies per square meter looking up into the canopy) is estimated as a measure of monarch abundance. Butterflies arrive in Mexico around early November and stay until March.

butterflies

This winter season (2016-2017), there were approximately 2.9 hectares of forest occupied with dense monarchs (somewhere in the neighborhood of 300,000 million overwintering butterflies). This estimate is down 27% compared to last year. Nonetheless, the previous two years were a 600% increase over the all-time low recorded in the winter of 2013-2014.

butterflies

Where does this leave us? This year’s population was higher than predicted by many. The season started with a late spring storm that killed an estimated 5-10% of monarchs in March 2016, and many reported low numbers of adults last summer. Nonetheless, the lower numbers this season compared to last are within the range of year-to-year variation, and overall, the population seems to be relatively stable over the past decade. With these 24 years of data, there are various ways to plot and assess the trends. Below I have plotted the four year averages for six periods beginning in 1992. Any way you slice it, the trend has been negative, and the population is not nearly what it once was. Nonetheless, the downward trend seems to have lessened this last period. Is this the new norm? How dangerously low are these numbers? And what can we do to reverse the trend?

butterfly

AgrawalAnurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.

 

 

 

butterfly

Anurag Agrawal on Monarchs and Milkweed

AgrawalMonarch butterflies are one of nature’s most recognizable creatures, known for their bright colors and epic annual migration from the United States and Canada to Mexico. Yet there is much more to the monarch than its distinctive presence and mythic journeying. In Monarchs and Milkweed, Anurag Agrawal presents a vivid investigation into how the monarch butterfly has evolved closely alongside the milkweed—a toxic plant named for the sticky white substance emitted when its leaves are damaged—and how this inextricable and intimate relationship has been like an arms race over the millennia, a battle of exploitation and defense between two fascinating species. Check the PUP blog each Monday for new installments in our “Monarch Monday” blog series by Anurag Agrawal.

What makes monarchs and milkweeds so special?

AA: Monarchs and milkweed are remarkable creatures, they’re on a wild ride! From the monarch’s perspective, its only food as a caterpillar is the milkweed plant. This makes them highly specialized, highly evolved, and very picky eaters indeed. They’re actually not that unique among butterflies, but they are extreme. Milkweed does everything in its power to defend itself against being eaten by monarchs. They make sandpapery leaves, toxins that can stop a human heart, and a thick poisonous goo that can glue an insect’s mouth shut. Again, although milkweed is not unique among plants, it is extreme. In what is called a coevolutionary arms race, monarchs and milkweed have been continually evolving over the eons to keep up with each other. As such, they have a lot to teach us about the way nature works, the way plants and animals interact, and about the various paths that evolution can take different species. And this is all to say nothing of the monarch’s spectacular annual migration, often over 3,000 miles flown by individual butterflies, using the sun to navigate, and having stored away milkweed’s poisons to protect themselves from being eaten by birds. Monarchs and milkweeds are royal representatives of all interacting species.

Why did you write this book?

AA: After studying monarchs and milkweed myself for over 15 years, I felt like I had a lot I wanted to share, especially with non-scientists and nature lovers. Monarchs and milkweed are such fascinating organisms, and yet so much of their beautiful biology is not widely known. I also wrote the book because there are areas of my own knowledge about monarchs and milkweed that I wanted to immerse myself in, but that I had not yet done any research on. So as an author, getting to visit the overwintering sites in Mexico, to study the population decline of monarch butterflies, and to understand their mating rituals were all fascinating detours from my everyday research life at Cornell University. The book was incredibly fun to write, and getting to work with artists and historians made it all the more rich. I hope that anybody that has an appreciation for nature, an interest in science, or just a curiosity about the ecology of plants and butterflies will enjoy this book. Working on this project has surely altered the course of my own research, the classes I teach, and how I see the natural world.

Why have you highlighted some of the personalities of the scientists studying monarchs and milkweeds in this book?

AA: One of the most amazing things about monarchs and milkweeds is the scientists who have studied them. They were such remarkable characters, especially those pioneering studies back in the 1950s: tremendously creative, sometimes competitive, and with some of their discoveries worthy of a Nobel prize. Getting to know them, both from their discoveries and their personalities, and how they interacted, has enriched my appreciation for how science is done. It also highlights the meandering and sometimes serendipitous nature of discoveries. I wanted to share the thrill of science, its ups and downs, and the process by which it is done with the curious reader.

Can you share one of your ah-ha! moments from studying monarchs and milkweeds?

AA: One of my favorites was from when I was an assistant professor at the University of Toronto. One day I was eating lunch by myself in a small downtown garden. Just by chance, I happened to sit on a bench beneath a very tall milkweed plant that had a very large monarch caterpillar feeding away. Without giving away all the details, that one hour encounter, in the middle of a city with 3 million people, changed my perspective on monarchs and milkweed forever. It was so unlikely an event, perhaps 1 in a 1,000 that a butterfly had been flying by and happened to lay an egg on this Toronto milkweed, and then a further 1 in 100 chance of that egg hatching and surviving to be that large caterpillar that I could watch it. And probably a 1 in a million event that I would happen to be eating lunch there, that day, to observe the events. In biology one has to work hard, be patient, and occasionally get very lucky! Throughout my studies on monarchs and milkweed, I have had tremendous luck in encountering wonderful biology that has had profound consequences.

Is the monarch butterfly going extinct?

AA: The answer to this very important and timely question is both simple and complex. On the simple side, there is no way the monarch butterfly is going extinct anytime soon. Having said that, the butterfly, and especially the long-distance migration that occurs every fall from Southern Canada and the USA, all the way to Mexico’s highlands in Michoacán, is indeed declining at a rapid pace, and we should all be worried about the sustainability of the annual migration. There’s so much information and misinformation floating around in the news these days about the causes of the monarchs decline. What I’ve tried to do in the book is outline the best knowledge that we have to date and to examine the facts critically, so we can really understand what might be going on. Unfortunately, we don’t have all the answers, but we can reject some of the most prominent explanations for the population decline of the monarch butterfly. As I argue in the book, planting milkweed certainly won’t hurt, but it is unlikely to save the monarchs annual migratory cycle. It is perhaps ironic that I spend eight chapters of the book discussing and detailing the importance of milkweed for monarchs, and nothing could be more true than their intertwined and intense evolutionary battle, but at this stage, and thinking about their conservation, it does not appear that milkweed is what is limiting the monarch’s population. Monarchs will persist for a very long time, but given that they are migratory butterflies that taste their way across North America, their declining population is something we must try to understand. Much more than the monarch is at stake, these butterflies are sentinels for the health of our continent!

Anurag Agrawal is a professor in the Department of Ecology and Evolutionary Biology and the Department of Entomology at Cornell University. He lives in Ithaca, New York. He is the author of Monarchs and Milkweed: A Migrating Butterfly, a Poisonous Plant, and Their Remarkable Story of Coevolution.