Weird and Wonderful Water

Water is the stuff of life. We can't live without it, and neither can the rest of the food chain. The search for extraterrestrial life hinges on whether or not a planet or moon contains liquid water, but that assumes that any life off Earth is the same as Earth-based life. This week we'll take a look about what makes water so special and how it keeps all of us alive.

Water, the most abundant substance on Earth.
Unless air is more abundant.

Water is unique among all chemicals (yes, it's a chemical) because it is the only one found in solid, liquid, and gas states naturally on Earth. While ice and water vapor aren't basic requirements for life, they are key components of the water cycle. Water stored as snow and ice in the mountains is slowly released during the dry summers in the American west, meaning a steady flow in rivers throughout the year. Clouds made of water vapor transport precipitation over long distances. On top of that, ice and steam make modern life more convenient- think food storage and electricity generation.

Winter snow waiting for the spring melt, March 2016

Typically, solids are more dense than liquids, which in turn are more dense than gases. Water flips this around, as ice is less dense than liquid water. If you freeze a container of water, you'll notice that the ice fills more of the container than the water did. This is why your frozen pipes burst in winter. The expansion of water as it freezes is a visual of the density decreasing. Because ice is less dense than water, it floats. Because ice floats, it forms on the surface of lakes and other bodies. This allows aquatic life to survive. If water froze from the bottom up, everything would either freeze in place, or eventually be exposed on the surface.

Molecular structure of liquid water and ice (Mountain Empire CC)

Water has adhesive and cohesive properties. Water molecules stick to each other (cohesion) and other substances (adhesion). Adhesion causes capillary action. This is the movement that is responsible for plants being able to absorb water in the ground through their roots, up the stem, and to the highest leaves. Cohesion also contributes to surface tension. Water molecules on the surface are more tightly packed and can resist pressure from outside forces. This allows objects to float. Water striders can stand on the surface because of surface tension.

Water strider striding water (National Wildlife Federation)

Water has a high specific heat. Specific heat is the amount of energy needed to raise the temperature of a gram of water by one degree Celsius. Because it takes a lot of energy (1 calorie per gram) to heat water, it takes a lot of heat to boil water. Ocean life appreciates not being boiled. Water also holds onto heat it absorbs and releases it slowly, moderating Earth's temperature and making the seasonal changes gradual.

Water dissolves more substances than any other. The polar structure of the water molecule. The positive hydrogen end will attract negative ions, while the negative oxygen ends attract positive ions. Water's solvency is important for plants and animals to absorb nutrients, and for animals to flush waste from their bodies. Nonpolar substances like fats do not dissolve. That's where the saying "Oil and water don't mix" comes from. Less dense fats will float on top of water, and with some skill they can be separated.

Next time you take a drink, raise a glass in appreciation of water. Without it, your drink wouldn't be here and neither would you. This week's information comes from USGS and Mountain Empire Community College.

South American Splendor

Hispanic Heritage Month is about to wrap up, and before it does let's celebrate by taking a look at some of the fantastic ecosystems south of the border. While the Amazon and Andes are the best known features of South America, there are many diverse habitats. This week we're exploring the Pantanal, the Pampas, and the Llanos, important natural features maybe you've never heard of.

The Pantanal is the largest wetlands in the world, located in Brazil, Bolivia, and Paraguay. Located just south of the Amazon, and in its shadow, the Pantanal actually has a higher concentration of wildlife than its more celebrated neighbor. This wetland is flooded by annual monsoon rains that leave behind pools of snacks for birds. Unlike the Amazon, the Pantanal is open, so ecotourism is easier. Not only are there better views of the wildlife and scenery, it's also more accessible because of the openness.

Pantanal (The Guardian)

The Pampas is a large grassland like the Serengeti or the Great Plains. It is in Argentina, Brazil, and Uraguay. It is flat and gently slopes toward the Atlantic. The western Pampas near the Andes is a dry section with brackish streams and ponds, but in the east it is more humid, better watered, and more fertile. While much of the land is still unchanged, large areas have been developed for agriculture.

Pampas (The South American Specialists)

The Llanos is a tropical grassland in Colombia and Venezuela. Wedged between mountains and highlands, the Orinoco River drains the region. Seasonal rains flood the plains, and after the rainy season it can be quite parched. The dryness had limited development in the past, but irrigation and mining activities are making it economical for people to live in the area.

Llanos (Latin America & Caribbean Geographic)

South America has so much more to offer than tropical rain forests and jagged mountain peaks. I hope this piqued your curiosity about these and other lesser known natural wonders. Information this week comes from National Geographic (Pantanal), Britannica (Pampas), and Geography (Llanos).

Nature Minute Book Club

Winter is my least favorite time to be outside. It's cold, dark, and precipitating. In fact, I'm expecting snow the day after tomorrow. It's a great time to grab a cup of tea and a good book. Here are some more suggestions for your reading pleasure.

Dolphin Diaries by Dr. Denise L. Herzing

Herzing spent a quarter century in the Bahamas, essentially living among the spotted dolphins, if only
during the summer. During her seasons there she was able to gain unprecedented access to their
behaviors, communications, and rituals. She was seemingly accepted into their society. This book
chronicles the amazing discoveries she made in her time with these fascinating creatures and will
challenge what you think about animal intelligence.

A Sting in the Tale by Dave Ghoulson

Learn about British bumblebees. Ghoulson recounts the history of bumblebees from their appearance
in natural history when dinosaurs roamed the Earth to their problems today. All this, of course, is
interspersed with his own humorous tales from a childhood fascinated with wildlife to his more recent
time in the field tracking down some elusive bees. Oh, and there’s pie.

The Invention of Nature, Alexander Von Humboldt's New World by Andrea Wulf

This biography of Humboldt explores his development from a dutiful son to the father of ecology, even
if the word didn’t yet exist. A contemporary of Darwin’s father, it was he who planted the seeds that
germinated into the theory of evolution. He even warned of human activities influencing the climate,
making him possibly the world's first environmentalist. We discover his intellectual, philosophical, and
artistic influences as well as tag along on his adventures around the world. 

Winter World by Berndt Heinrich

Heinrich is an entomologist by trade, but his keen eye for observation makes him a great naturalist as
well. Part science, part personal narrative and drawing on his own research and observations, in this
book he takes us for a walk through Maine woods to see how critters from flies to bears survive the
brutal Down East winters.

Changing Leaves

Fall is in full swing. The sun keeps the air warm, but it's chilly in the shade. Honking geese fly overhead and crickets chirp throughout the lengthening nights. Dried leaves swirls about in the breeze, while those still in the trees for a riot of color. What is going on inside the tree that causes the color change?
Trees are getting ready for a long winter's nap. Like animals going into hibernation, everything is slowing down. Trees have been gorging themselves on sunlight all summer, and now their metabolism is slowing down. The chlorophyll is breaking down and water uptake is stopping. Chlorophyll absorbs all wavelengths of light except green, which is reflected back to us. Without chlorophyll, we see other chemicals in the leaf.

A yellow sugar maple catches the late morning sun

The yellow leaf of a sugar maple

Xanthophyll colors the leaves of aspens, birches, and beeches a bright yellow. It's also found in corn.  Red and purple in red maples and scarlet oaks comes from anthocyanin, which is produced when the chlorophyll stops and the leaf metabolizes extra sugars. Carotene, the same as what you find in a carrot, gives trees like sugar maple and sassafras their orange leaves. Orange can also come from a leaf that is showing both xanthophyll and anthocyanin. Brown, such as in oaks, comes from tannins. Carotene and Xanthophyll are present all year in the leaves, but are overshadowed by chlorophyll.

Another sugar maple, this one decked out in red

This red sugar maple leaf fell of a Canadian flag

The brilliance of each color, as well as the amount of colors relative to each other, are dependent on the weather. If fall is sunny and dry, trees will produce more anthocyanin. Trees will be a more brilliant red. Other years, trees won't produce as much or even none at all and nearly all leaves will change to yellow.
But of course, each tree is an individual so it may change well before its neighbor or have different or more vibrant colors, even among the same species. I've seen red maples that look like traffic lights with red, yellow, and green leaves on the same tree. I've even seen multi-colored leaves.

Brown oak leaf, rich in tannin

Yet another sugar maple, this time in orange

Get out there and enjoy some biochemistry in action before it's too late! The leaves have been great this year, peaking in my area this week and next. Up north you may be past peak, and down south it's on its way! This week's information comes from SUNY College of Environmental Science and Forestry and Montana Natural History Center.

Yellow and brown hickories and oaks basking in late
afternoon sunshine

Be Bear Aware

With the arrival of fall and the approach of winter, food sources are becoming scarce for some animals. Bears spend the winter either hibernating or in torpor, a state of lowered metabolic and other bodily activities. To prepare, they begin gorging themselves this time of year so they can have enough calories to last through an extended period of not eating. While they generally try to avoid humans, now and when they emerge in spring (very hungry) are the most likely times you will encounter a bear. Here are some helpful tips on how to avoid or survive a bear encounter.

Don't let this happen to you! (US Forest Service)

Hungry bears are attracted to food and will follow their noses. When camping, store food, drinks, utensils, cookware, dishes, cosmetics, and hygiene products in a bearproof container, locked in a vehicle, or suspended 10-15 feet above ground and 4 feet on all sides from a climbable surface. Sleep in a tent or camper away from your cooking area. Don't sleep in clothes you cooked in. Don't set up camp near berry patches, carcasses, and bear signs. Avoid foods with a strong smell like bacon and fish, no matter how good they are. Sleep near your flashlight and bear spray. If you see a bear try scaring it away by making loud noises. If it is undeterred, move away to a safe area.

Ideal camp setup (WildAware Utah)

When hiking, if you see a bear that hasn't noticed you, move away quickly, quietly, and calmly. Never try to run from a bear. Running might trigger the chase instinct and the bear will always beat you in a race. If you see a bear and it notices you, let it know that you are human and  not food or another bear. Talk to it calmly, move your arms about, and keep an eye on it without making eye contact. Hopefully the bear will leave. If it does, walk away in a different direction. If it remains, back away slowly but keep making small talk. If the bear approaches you and is acting defensively- making loud noises moving its head around, or stomping or pawing at the ground, stand your ground. If the bear approaches, it's probably bluffing. Keep talking calmly to it, and start backing away when it stops coming at you. If it comes at you again, stop moving but keep talking until it stops again. If it attacks you, now is the time to play dead. Face down on the ground, keep your backpack on if you have one. If the bear rolls you over, keep rolling until you are face down again. Otherwise, don't move and don't make any sound until you're sure the bear is gone.
If you are faced with a quiet bear that won't leave, you'll probably have to fight the bear or at least make it think you want to. If backing away doesn't keep the bear from you and it is behaving calmly, act aggressively to let the bear know that you are not an easy meal. Yell at the bear, make yourself appear as large as possible, throw things at it, swing a large stick at it, and make eye contact. The idea is to make the bear think that since you are crazy enough to fight a bear, it probably shouldn't be messing with you. If the bear decides to attack anyway, fight back with a focus on its face. If you have bear spray, use in situations where the bear is aggressively approaching you. Make sure you are not spraying into the wind, and don't spray it on yourself as a repellent. Read the instructions.
The reason I chose bear safety this week is because I just had my first bear encounter while camping in Virginia. I was tent camping about 30 miles south of Washington, DC and while I got up to use the bathroom at 1 AM a bear took advantage of my absence and ransacked my campsite. It put some holes in my tent, knocked my cooler off the picnic table, and tipped over my folding chair. What did I do wrong? I had my alarm set for 5:30 AM so I could catch an early train into the city. To move more quickly, I had my next day's clothes and my toiletries in the tent with me. That was my first mistake. My second mistake was leaving the cooler in the open. I had 8 bottles of water and 3 glass bottles of root beer in there. I decided the ice would last longer in the woods than it would in the car when drove into civilization, where it's generally hotter. My third mistake, which wasn't really a mistake but just the circumstances, was not having safety in numbers. Bears don't like people; we have a bad reputation in the animal world. Being off-season in the middle of the week, the campground was pretty much empty. With no people around, maybe the bear felt like the campground was OK to stroll through, and the only tent around was an easy target.

Holes in the tent were on the right side, so I'm guessing
the bear moved right to left, swatting the chair over for
dramatic effect.

When I came back to the campsite, the bear was gone. The tent was a heap, so I spent the rest of the night in the car with the doors locked. Yes, I've seen a news article where a bear gets in a car and steals it.  After sunrise, I inspected the damage. There were holes in the tent, nothing too big but they'll only grow each time the tent is set up. None of the drinks were opened and the glass bottles didn't break. Despite their superhuman strength, bears still need you to open a bottle for them. The chair was fine, but I have no idea why the bear decided to flip it. With a damaged tent, I ended my trip a day early. This week's bear safety tips come from the Grizzly and Wolf Discovery Center right outside fabulous Yellowstone National Park.

Crickets

Fall has almost fallen. It's hard to believe summer was in full swing when you last read a fresh Nature Minute blog. Internet issues and life in general kept me from my regular schedule. Maybe where you are, the leaves are starting to turn, there's a bit of crispness in the air, mornings are full of fog, and nights are longer and full of chirping crickets.

Black field cricket Gryllus assimilis (Texas A&M) 

Here in Pennsylvania, crickets typically begin their nightly serenades in the late summer, continuing through the fall. Only the males chirp. They do so by rubbing their wings together, as a mating call for the females. They are most active at night, and even during daytime are hard to find. If they notice you getting close, they'll stop chirping so you really need to look hard if you want to find the source of the chirp. Warmer temperatures will produce more chirps, and the number of chirps drops with the temperature. I never counted chirps before, so I never noticed this.

Northern mole cricket Neocurtilla hexadactyla
(University of Florida)

Many people consider crickets to be a pest because the chirping gets annoying, but they are generally harmless. Since crickets favor loose soil, they are frequently found in flower beds, which are usually right under your bedroom window, giving you a front row seat. At the bottom of the food chain, in large numbers they have the potential to attract other unwanted guests to your home such as raccoons and spiders.

Carolina ground cricket Eunemobius carolinus
(Oklahoma Panhandle State University)

Nature Minute will return in October with more autumnal awesomeness. I'm taking a much-needed vacation. Until then, relax to the sound of the crickets. Don't let them drive you nuts. They'll only be around a few more weeks, and then it will be too cold to keep the windows open at night. This week's cricket facts come from Terro.

Sound of the Wild

Think about the sounds you typically hear over the course of a  normal day. It starts with the alarm clock and quickly fills with noise. The toaster, the hairdryer, the microwave, cars, cars, and more cars, people talking and shouting, buses, trucks, trains, planes, and of course your phone. If you're lucky you heard some birds singing on the way out the door. Other than the lawnmower, popcorn, and a log on the fire, my favorite sounds come from a land far from modern conveniences.
Next time you are out and about pay attention to what you hear. Insects buzzing, birds singing and calling, the wind in the trees (or your ears). In the mountains you might hear pikas and marmots barking, or larger animals like coyotes or wolves howling in the distance. In the fall, you might be treated to the eerie sound of bugling elk.

A not-so-distant coyote, not howling

Water is life, and it also provides a great soundtrack. I can listen to crashing ocean waves or a gurgling river all day long. Rain falling on surfaces other than pavement is a wonderful experience. The pattering on a tree canopy is soothing enough to forget about being soaked, and rain falling in a pond is a magical sound. In a naturally quiet environment like a cave, there's a good chance you'll hear only a single drop of water at a time, maybe a few seconds apart, maybe a few minutes. Even better than rain is the sound of thunder in the distance. This can be a bit worrisome if you're a long way from shelter.

The soothing sounds of the Firehole River

Late summer nights, if there is no thunder, fall asleep to the sound of the crickets. In the spring, fall asleep to the sound of the tree frogs. Another special spring sound, which I've only heard once, is the knocking sound the trees make after the thaw when they start absorbing water and their sap is flowing again. It took a while to figure that one out.

Pacific tree frogs, a sure sign of spring

Here is a link to a short video of some sounds recorded at Yellowstone National Park. Note that the pictures don't necessarily correspond to the sounds. See how many sounds you can figure out!

Species of the Month

We're still in Old Man Winter's icy grip for at least another month, so it's the perfect time to feature another critter that thrives in cold, snowy weather. This month we'll take a look at the elusive Canada lynx.

Canada lynx slinking among the vine maples

Scientific name: Lynx canadensis

Kingdom: Animalia (animals)

Class: Mammalia (mammals)

Order: Carnivora (carnivores)

Range: Circumpolar- Canada, northern US 

Habitat: Forest and tundra

Lifespan: Up to 14.5 years

Diet: Snowshoe hares, rodents, birds, fish, carrion

Predators: None known though bears and wolves may prey on kittens

Conservation Status: Listed as threatened under the US Endangered Species Act and endangered by the state of Michigan

The giant feet are visible in this shot (USFWS)

Other Information: The lynx is known for its intricate relationship with the snowshoe hare. The lynx population fluctuates in response to that of the snowshoe hare, with the lynx lagging by about a year in a nine year cycle of boom and crash. The lynx may as well be known as a snowshoe bobcat, as they are similar in appearance. The lynx has large feet that work as snowshoes, allowing it to hunt in the deepest snow. Another difference between the cats is the longer tufts of ear hair on the lynx. Litters are commonly two or three kittens, born April to June. They stay with the mother until the following mating season, almost a year later. Lynxes are solitary creatures, and are mainly nocturnal hunters. While smaller animals are their main prey, they will take a sick or injured deer if the opportunity presents itself.

This shot offers a better view of the ear hair (USFS)

This week's information comes from the University of Michigan's Animal Diversity Web.

Species of the Month

Winter returned with a vengeance this week as the temperature dropped to single digits with a wind chill in the minus zone. Arctic air pushed down and along with icicles and dreams of tropical paradise, it provided the inspiration for the species of the month, the Arctic fox. This cunning critter enjoys a polar vortex much more than I do!

Arctic fox (Environment and Natural Resources, Northwest Terr.)

Scientific name: Vulpes lagopus

Kingdom: Animalia (animals)

Class: Mammalia (mammals)

Order: Carnivora (carnivores)

Range: Circumpolar- Canada, Alaska, Greenland, northern Europe, northern Asia

Habitat: Arctic tundra

Lifespan: 3-6 years on average

Diet: Small mammals, birds, eggs, insects, berries, carrion, dung

Predators: Red fox, humans

Conservation Status: No special protection

Arctic fox (USFWS)

Other Information: Arctic foxes, unlike other canids, have furry feet. In the cold north, that is a valuable asset. Colors change seasonally, from a summer coat of gray to a white winter coat. They live in a family group in a den with multiple openings and a tunnel system. A breeding pair and a female offspring from the previous litter, plus the new pups, make up the family group. The older offspring helps raise her younger siblings as a tradeoff for food and shelter. This behavior is also seen in some bird species, and that female has been statistically shown to have a higher survival rate of her own future litters. Arctic foxes are opportunistic feeders, eating anything that comes along. Carrion feasts have been known to include seafood such as fish and seals. A favorite small mammal meal is the lemming. They are hunted for fur and as a livestock pest in Iceland.
This week's information once again comes from University of Michigan's Animal Diversity Web.

More Winter Adaptations

The dead of winter is nigh upon us. It had been relatively mild where I am, despite a colder fall than usual. Unlike this time last year, we are having some temperatures above freezing. I deal with the cold by putting on this flannel,

but how are some more of out animal friends coping?
The wood frog survives by going into suspended animation while buried in mud or leaf litter. For all intents and purposes, it is dead. It survives the cold (and insect-free) winter because it produces a natural antifreeze that keep the water in its cells from freezing and bursting.

Wood frog (MN Dept. of Natural Resources)

Deciduous trees also have to work around internal ice causing cells to burst. In late summer they prepare for winter by shedding their leaves, which reduces the surface area that snow and ice can accumulate on. That protects branches from breaking. They also drastically reduce water consumption. It won't be needed without photosynthesis happening, and less water stores in the trunk is less risk of water freezing and causing a rupture.

Leafless trees that gave up drinking

Snapping turtles survive by spending the winter underwater. Lucky for them, water freezes from the top down rather than from the bottom up. The cold water and lack of oxygen may seem less than ideal living conditions but somehow the turtles survive by changing their blood chemistry to compensate for increasing levels of acid.

Snapping Turtle (Missouri Dept. of Conservation)

Insects also are able to adapt to winter conditions. I always assumed they flew south ahead of the birds or just did when I was younger. Some use the same antifreeze method as the wood frog. Others allow themselves to freeze without becoming ice, a process known as supercooling. Supercooled fluids remain liquid at temperatures below freezing. But the risk is always there that a single particle could allow ice crystals to form. Once that happens it's game over.  The fluid instantly iced over, killing the insect.

Supercooled stonefly (Scientific American)

While you are enjoying the snow from inside your cozy house, just be thankful you don't have to rely on chemistry or dehydration to make it through the winter. And next time you need a snack, it probably won't be your last for a few months.
This week's information comes from the Minnesota Department of Natural Resources and Bernd Heinrich's book "Winter World".

Species of the Month

Halloween is right around the corner, so it’s time for another creepy crawly species of the month. We’ve covered bats and owls, so this year we’ll go to the spiders. Stop reading here if they creep you and come back next week. Grass spiders are a genus of several funnel weaving spiders, including the Pennsylvania grass spider. You’ll likely start noticing these robust spiders in your house as they venture inside to avoid the falling outdoor temperatures. We associate spiders with Halloween because they are at their biggest after growing all year.

Pennsylvania grass spider at my sister's house

Scientific name: Agelenopsis species

Kingdom: Animalia (animals)

Class: Arachnida (arachnids)

Order: Araneae (spiders)

Range: All of North America except Arctic areas

Habitat: Lawns, your house during fall

Grass spider in its natural habitat (Penn State)

Lifespan: One year

Diet: Insects

Predators: Birds

Conservation Status: No special protection

Grass spider in its web (Missouri Department of Conservation)

Other Information: Grass spiders build funnel or tunnel shaped webs in the grass, hence the name. Females lay eggs in sacs during late summer or early fall, with eggs hatching in spring. The eggs survive over the winter but adult spiders do not. Grass spiders are fast and typically avoid humans, but will occasionally bite with trapped and threatened. Information this week comes from Insect Identification, despite spiders not being an insect.

Firefly Watch

I participated in an ongoing citizen science project over the summer. Firefly Watch was formerly run by Boston’s Museum of Science, but was run by Massachusetts Audubon this summer, my first with the program. The goal is to monitor firefly populations by counting the number of flashes in three periods of ten seconds. Colors and flash patterns, as well as date, time, weather conditions, and site conditions are all recorded. I signed up for this because fireflies were always a highlight of the summer when I was a kid, and later when my own kid was little. 

Having been away from my ancestral home for a decade, I had no knowledge of local population trends other than my mom telling me she never sees fireflies anymore. That was disturbing to hear. So twice a week I went to my parents’ house starting in late May to see if they had any fireflies left. The first ones showed up on Memorial Day, right about when I remember them first arriving. They were few and far between for the first two weeks or so and peaked around the 4^th of July. I decided to keep up the watch until I had two consecutive shut outs, and expected to be done the first week of September. 

However, the last firefly I recorded was on September 24^th, later than I’ve ever seen one. In fact, I only remember seeing them in September once before, and they came a month late that year. To top it all off, I saw another on September 28^th during the day while away from home. However, to be consistent I only counted observations at one site. To me, it isn’t helpful to track population trends if I am not tracking at the same location, at least in this case. For something larger with a wider range I would, but these little guys don’t roam very far. Since this was my first field season I have no data to compare with, but I plan on being back. Hopefully all I’ll see is positive trends!

Feel free to sign up for Firefly Watch next year!

Deciduous Decisions

In the plant world there are two types of trees: deciduous and evergreen. Deciduous trees give us spectacular displays of fall color before shedding their leaves. Evergreens provide a shadow of summer with a splash of green during the bleak winter days. Both types of trees use the leaves (broad leaf or needle leaf) for photosynthesis, but obviously the deciduous tree evolved to opt out of photosynthesis during winter while the evergreens evolved to work a longer season. Which tree has the competitive advantage until the spring greenup?

Life in the wild is all about two things: making babies and being energy efficient. Depending on the environment and situation, being deciduous or evergreen offers a competitive advantage by saving energy, but of course it also comes at a price.

Deciduous trees typically live in areas with temperature fluctuations. Here in the northeast, we have a nice mix of deciduous trees: maples, oaks, hickories, poplars, and more. We also have four distinct seasons. Winters can be snowy, and for a tree that spreads it branches quite a distance from its trunk, not having leaves to catch a heavy snowfall could be the difference between losing limbs or not. Evergreens compensate for snowfall by having a conical shape and shorter branches, with the longest at the bottom. The branch structure allows snow to fall to the next level of branches relatively quickly.

Summer deciduous

While the loss of leaves saves branches, it costs the tree energy. A tree must have enough energy stored up for next spring’s new leaves by fall. Because photosynthesis uses energy (much like chewing and digesting your food burns calories), deciduous trees evolved to shed leaves when there is less sunlight, not enough to be worth the energy expense to generate some more energy. While the deciduous trees are standing idly through the winter, evergreens take advantage of their ever green leaves (either needles or broad leaves in the tropics) and photosynthesize for a longer season or year-round in the tropics. They gain a little more energy that way, and we’ll see why next.

Late fall deciduous

Those expendable deciduous leaves are fairly flimsy compared to a pine needle or palm frond, which are built to last. Less energy is required to build a full set of maple leaves than pine needles. More of the maple leaf is dedicated to photosynthesis than a pine needle, which needs more compounds for structure and defense. Unit for unit, a maple leaf generates more energy than a pine needle. Evergreens, conifers especially, use that conical structure to capture more sunlight to maximize energy production.

Summer evergreen conifers

Deciduous trees thrive in nutrient-rich soil. If there are plenty of nutrients to absorb, they can afford to shed leaves. They often draw remaining nutrients from the leaves back into the trunk before shedding leaves. They even contribute to the nutrient cycle with their fallen decaying leaves. Evergreens have adapted to nutrient-poor soil. They keep their leaves because of a lack of available nutrients. If you look at how green and full of life the tropical rainforests and dense forests of the Pacific Northwest are, you may be shocked at how poor the soil actually is. The nutrients are usually absorbed right out of the dead material into the upper layer of soil and into the living trees.

Winter evergreen conifers

The different leaf styles also lead to different strategies for water conservation. When stressed due to dry conditions, deciduous trees will shed their leaves early to stop water loss. During photosynthesis, water is drawn from the roots to the leaves to make it happen, and the trees exhale water vapor. Evergreens keep their leaves, but they have a waxy cuticle on them that helps prevent water loss.

Hopefully you have a better understanding of why trees do what they do. With fall here and winter on the way I think we can appreciate both leaf styles for the splashes of color they give us. How is the leaf situation in your neighborhood?
This week's information comes from an article by Frances C Smith in the journal Maine Naturalist. 
Frances C Smith: Smith, F. (1993). Evergreen vs. Deciduous Woody Plants: Which Wins Where. Maine Naturalist, 1(4), 205-212. doi:10.2307/3858181 

Migration

The days are getting shorter and cooler. Leaves are starting to turn and fall. Winter is approaching, and many animals are have already begun their seasonal migration. While some hibernate to avoid unfavorable seasonal habitat conditions, others move temporarily to more suitable habitat.

Migrations occur across all different animal classes: birds do it, and so do mammals, fish, insects, reptiles, amphibians, and crustaceans. Even some people do it. Florida and Arizona get plenty of snowbirds from up north every winter. More traditionally, nomadic tribes still exist in Africa and Asia living as they have for centuries.

We’re an ecology blog, not an anthropology blog so let’s forget about nomads for a minute. Perhaps the most visible migrations here in America are those of birds and monarch butterflies. Birds migrate to and from pretty much everywhere. Some stay within North America when migrating while others fly from pole to pole. Others, of course, are somewhere in between.

We’ll use the Baltimore oriole as an example of avian migration. They arrive in the eastern US from Central and northern South America in April and May. This is their breeding ground. They begin nesting right away and eggs usually hatch in June. Southern migration begins as early as July and has peaked by September.

Baltimore oriole (NPS)

Monarch butterflies journey to Mexico in a multi-generational migration. Northern monarchs go south to the oyamel fir trees in the mountains of central Mexico. Millions of them cover the trees. After winter, they head north again, laying eggs on milkweed plants. Caterpillars hatch in a few days and eat the plants before forming a chrysalis. A new butterfly emerges and continues the northward journey, stopping at milkweed to lay eggs and start the hatching and migrating process over again. The northernmost monarchs are able to return to Mexico in a single journey.

Monarch butterfly

The pronghorn in Wyoming migrates vertically. It moves from summer grounds in Grand Teton National Park about 150 miles south to lower elevation in the sagebrush habitats of the Green River area. This is North America’s longest mammal migration.

Pronghorn

Not all migration is seasonal. Zooplankton in the ocean migrate vertically through the water column on a daily basis. At night the move toward the surface, and by sunrise they are headed back to the briny deep. While a journey of hundreds or thousands of feet might not seem like much to you, keep in mind that these tiny critters probably can’t see as far as the other end of a yardstick.

Zooplankton (Nature International Journal of Science)

Fall migration is happening now. Who is moving through your neck of the woods?

This week's information comes from:

Journey North (Baltimore oriole)

National Geographic (monarch butterfly)

Wildlife Conservation Society (pronghorn)

Nature International Journal of Science (zooplankton)

Desert Life

This time of year, there’s usually no place in America that’s hotter than the desert Southwest. The region is known for its striking red sandstone formations, deep canyons, and ancient ruins. While the desert may seem like a barren wasteland to the casual observer, it is full of life. If you know where to look. The critters of the desert have evolved with special adaptations that allow them to survive in a harsh environment. Let’s have a look at some.

Extreme heat and scarce water are two hardships of the desert. Because of the second problem, sweating is an impractical solution to the first problem. As a workaround, the jackrabbit has large ears which are full of blood vessels. The blood vessels bring warmer blood away from the body core to cool. The large surface area of the ears also helps the cooling process (National Geographic).

Black-tailed jack rabbit (NPS)

The kangaroo rat has adapted to life without beverages. It can go an extended period without water, absorbing what it needs from its plant-based diet. Too keep cool, it lives underground and is nocturnal (Arizona-Sonora Desert Museum).

Stephen's kangaroo rat (Arizona-Sonora Desert Museum)

The various cactus species have evolved to avoid water loss. All plants lose water through their leaves in a process called transpiration. Cactus plants minimize the loss by having long, thin needles in place of the leaves we’re familiar with on trees and other leafy plants. They also have an extensive root system for maximizing water collection potential and a wide, hollow stem for water storage (BBC).

Saguaro cactus (US Forest Service)

Other desert plants have adapted as well. Shrubs and non-woody flowers survive by growing deep roots that can reach down into the water table. They have hardy seeds that can last for years before germinating. When the rare shower falls, these plants simultaneously burst to life in a brief but spectacular desert bloom (Science News for Kids).

Superbloom (National Park Service)

The Great Basin spadefoot toad has a cool adaptation for surviving in the desert. They burrow underground and remain in a state of suspended animation for years until rainfall brings it to the surface for mating and feeding. Mating pairs will lay and fertilize eggs anywhere water collects, then the race is on for the eggs to hatch and tadpoles to develop before the water evaporates. The tadpoles are cannibalistic, which might be an incentive to hurry up and grow (The Nature Conservancy).

Great Basin spadefoot toad (Idaho Fish and Game)

You probably don’t think of shrimp living in the desert. The fairy shrimp’s habitat is ephemeral (seasonal) pools that form in depressions in rock. They are tough little buggers, able to withstand extreme heat. Their eggs can survive desiccation for decades, using sugars instead of water inside the egg. The eggs can remain in place until rain activates it and it hatches, or they can be carried on the wind to a new location and hatch there when rain comes (National Park Service).

Fairy shrimp (National Park Service)

Next time you happen to be in the desert, look around for these and other fascinating critters. The desert is alive, if you look hard enough to see the life all around you.