August is Ocean Life Appreciation Month at Next-Door Nature… this week, a sea turtle chillin’ in the coral reef of Shoreditch, London, UK (photo: maureen barlin, cc by-nc-nd 2.0)
August is Ocean Life Appreciation Month at Next-Door Nature… this week, a sea turtle chillin’ in the coral reef of Shoreditch, London, UK (photo: maureen barlin, cc by-nc-nd 2.0)
Temperatures across the southern half of the U.S. are soaring into triple digits, so I was trying to think of creative solutions to beat the heat when it hit me—why not become cold-blooded!
Alas, my brain must have overheated. Once air conditioning allowed a cooler head to prevail I realized that what seemed like a brilliant idea while baking beneath a blazing sun is absolutely, completely, utterly impossible… and not simply because mammals cannot will themselves to undergo metamorphosis.
You see, technically there’s no such thing as a cold-blooded animal (unless you’re speaking metaphorically about someone who lacks emotion or empathy). Or a warm-blooded animal, for that matter. Both terms are shorthand for the ways in which body temperature (aka thermophysiology) is controlled in different types of organisms.
Most mammals and birds are classified as endotherms (Greek: endon = within; thermē = heat). For these critters thermoregulation is an inside job, primarily by way of metabolic processes. Under extreme environmental conditions some physical mechanisms come into play, but not solar energy (at least, not directly). If the mercury plummets and the body’s core temperature begins to drop, muscles shiver to create warmth; if the core temperature starts to rise the body perspires to cool via evaporation. No sweat glands? Pant like a dog… or birds. All evidence to the contrary, since humans are mammals, swimsuit-clad sunbathers dozing in rows on a beach or poolside with icy drinks standing at the ready are, in fact, capable of maintaining a relatively constant body temperature.
When an animal’s body temperature is strongly influenced by ambient conditions it’s an ectotherm (Greek: ektós = outside). Fish, amphibians, reptiles, and invertebrates rely on external heat sources to get their juices flowing, especially during the chillier seasons or cooler times of day. That’s why these animals can be seen basking on rocks, roads, and any other warmth-radiating surface. Then, when they can’t stand the heat they get out of the kitchen, retreating into shade, water, or underground to cool off (Sound familiar? We really are more alike than different).
Take-home message: mammals and birds are endotherms; invertebrates, fish, amphibians, and reptiles are ectotherms.
Except when they aren’t.
It’s the exceptions that make the rule, right? Let’s begin with the usual ectotherm suspects. According to one source, 2% of invertebrates are endothermic. Regrettably, the informant failed to name names but, in spite of the fact that spineless animals are not my strong suit, I did managed to chased one down—snails and slugs (Oops, that’s two… and “chased” may be overstating things). Fish, being vertebrate species, are my regular beat so I can state with certainty that billfish (e.g., sailfish, marlins), tuna (Scombridae), one family of sharks (Lamnidae, including makos and whites), and one species of mackerel (Gasterochisma melampus) are endothermic… at least to some degree. I’ve yet to find a reliable report of an endothermic amphibian, but among the reptiles sea turtles exhibit both ecto- and endothermic traits.
Moving along to the endothermic exceptions… Hummingbirds (Trochilidae), swifts (Apodidae), and common poorwills (Phalaenoptilus nuttallii) all experience periods of lower body temperature and metabolic rate; therefore, some biologists argue they have ectothermic traits. Additionally, there are mammals—certain rodents, a couple of lemurs, and many bats—that enter hibernation or estivation in response to low temperatures or drought, respectively. Then there’s the echnidna (Tachyglossidae), a “primitive” mammal from Australia that’s an ectotherm eleven months of the year and an endotherm during the month when it lays its eggs (Yes, eggs. If you like rule-breakers Australia is your Mecca. In the interest of time and space, though, we’ll have to save monotremes for another day).
What I’ve presented above is a fairly simplistic description of thermophysiology. Why stop there? Because a more thorough treatment would require a good deal of nuance and a complicated discussion of sub-categories, not to mention a stiff drink (the current temperature is 99°F and rising—make mine a frozen margarita). But since it’s so hot I’ll go ahead and venture past a toe in the water… up to my knees, but no further.
One subset of the endotherms are tachymetabolic (Greek: tachy = quick), organisms with a consistent and extremely high metabolic rate. Shrews (Soricidae) are a perfect example—diminutive beings with massive appetites, their metabolic rate is at least five times that of similarly sized ectotherms. Being able to snack non-stop and still rock a bikini probably sounds too good to be true. It is. Finding a constant supply of calories without access to fast food and grocery stores is no picnic. Bradymetabolic (Greek: brady = slow), which could easily be mistaken for bipolar disorder, is no bed of roses either. These organisms swing wildly between a high (when active) and low (when resting) metabolism, usually based on either external temperatures or food availability. (If you think someone else has got it better, rest assured you probably don’t know the whole story.)
As biologists refine our understanding of how bodies work, language evolves and once popular terms like cold-blooded fall from favor. Popular stereotypes suggest otherwise, but scientists are not completely immune to trends. When I was an undergrad, for example, the preferred word for organisms influenced by changes in ambient temperature was poikilotherm (Greek: poikilo = varied, irregular). Although still useful for making distinctions between types of ecotherms, the term is used less frequently now and may be on it the way out.
C’est la vie. Styles change, in both the lab and on the beach (Thankfully. I’m old enough to remember when Speedos were all the rage in men’s swimwear). I’d be willing to bet, though, that most Earthlings won’t give up sun worship any time soon. Chillin’ in a sunbeam feels too good, whether you need it or not (at least as long as there’s a pool nearby).
Ever dreamed of going on a safari? Then fasten your seat belt, start the engine, and hit the road. Any road. I’ll bet you dollars to donuts—take the time to look and you’ll spy enough wildlife to satisfy, Bwana.
Sure, some of the creatures will be easier to spot than others… for the simple reason they’re no longer moving. But I’m not proposing a road-kill road-trip. Trust me, the city streets, shady neighborhood boulevards, highways and byways offer plenty of opportunities for wildlife watching. Naturally, the species on display depend on the size of the road, its location, the season, time of day, and the speed limit.
Let’s say your motoring down a divided highway, a conduit to and through the all-American suburbs. The big stuff (aka megafauna), such as deer, elk, moose, bears, and even coyotes, can be seen at 65+ mph (although not always in time to either admire or avoid them). Certain birds of prey, red-tailed hawks in particular, can be seen at both speed and distance due to their habit of hanging out high on handy utility poles to scout for snacks. Anything more petite will be visible only if it’s on the shoulder or trying to cross the road. Scavengers looking for a free lunch can be seen out on the open road day (crows, ravens, vultures) and night (opossums, coyotes). That meal ticket can quickly turn the diner into dinner for someone else… and so on.
Beyond mowed blacktop borders, in the woods and taller grasses, you’ll find rabbits, foxes, raccoons, skunks, and groundhogs. Based on my own non-scientific observation, to improve your chances of seeing these meso– (medium-sized) species as well as small but brightly colored male songbirds in situ you’ll have to ease up on the gas pedal and let the speedometer drop to 35-45 mph, tops.
A bicycle (or even a horse if you have access to one) would probably set the right pace for a rider to notice mice and voles, lizards, turtles, frogs and toads, as well as female songbirds (who tend to have less flashy wardrobes than their ready-for-the-disco menfolk). The truly diminutive critters—insects, spiders, snails and slugs—are hard to spot at more than arm’s length so it’s best to set off on foot and plan for a leisurely pace if spineless quarry is your goal. A general rule: the slower you go, the more you’ll see—that’s what makes the backroads more appealing for this kind of trip than a superhighway.
In poetry, novels, song, and cinema people often speak of the allure and romance of roads—the ones that calls us, the ones less traveled, the ones that go on forever, choosing between high ones and low ones. Wild animals rarely have access to books and mp3 players and RedBox kiosks, though, and I’ve never found them to be all that interested in popular culture… so what’s the attraction?
To build a road through a previously undeveloped area, the first thing that happens is clearing a swath of the existing plant community, be that trees and shrubs or grasses or cacti. Once the project is completed (or even while it’s still in progress) new plants begin to colonize the bare soil, creating a plant community that’s different from the surrounding landscape along with an edge where new and old meet. Disturbing the soil stimulates the germination of seeds that may have sat dormant for a long time waiting for the right conditions. Soil may be brought in from somewhere else as part of the construction process along with seeds from plants that are completely novel in this setting.
Since the plants predict what kind of animals will be found in any ecosystem, the new habitat creates opportunities certain wildlife species will exploit… but in most cases it won’t be the species that were living happily in the pre-construction habitat. Edge species will colonize the area, often using the right-of-way as a travel corridor before and after the road is completed. Some organisms will hitchhike to their new home on and in the bodies of larger animals or even motor vehicles. Birds, bats, and flying insects will drop in from above. Wild things are always jockeying for space and there’s no such thing as a vacant lot in nature—at least, not for long.
Make no mistake—roads are a significant cause of habitat loss and their presence is detrimental to many types of wildlife. For others, though, the resulting edge provides exactly what they need to thrive. This includes our most familiar next-door nature species. In fact, the reason blue jays, robins, white-tailed deer and other edge-loving species are so common in human communities is because Homo sapiens is also an edge-loving species. Our roads are simply one very conspicuous example of that fact.
The natural world is never static; it’s always in flux and each day there are new winners and losers. Are roads good or bad for wildlife? It depends on the species. But there’s no doubt they are a boon for wildlife watchers.
© 2012 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work. Just ask first.). Thanks to these photographers for making their work available through a Creative Commons license: Colleen Greene (black bear); e_monk (black vulture); Matt Reinbold (groundhog); MoDOT Photos (edge habitat); Allan Harris (pronghorn).
The holidays are well behind us now. Shorter days and Jack Frost nipping at your nose have lost their novelty. It’s the start of a more serious season, filled with snowplows, tire chains, and 10-pound sacks of litter that will never feel a kitty’s caress. In many parts of the northern hemisphere, it’s a long slog through snow, sleet, and freezing rain to get from January to jonquils.
Understandably, we look to Nature for role models. Native people aren’t unique in their ability to draw a connection between human and non-human animals—Madison Avenue is especially canny at choosing charismatic creatures to impersonate our enviable and endearing (or at least humorous) characteristics. Particularly at this time of year, when the mercury can’t seem to bootstrap its way past 32°F, you’ll find a lot of furry salespeople pitching warm and cozy wares in magazines and newspapers, on television and online. I assume the general idea behind this trend is that raw, gray days bring out the hibernator in all of us mammals.
Not to split hairs, but that’s not technically correct. Humans don’t hibernate. That’s not to say we don’t go through some behavioral changes at this time of year—we do (at least so far as jobs, school, and the other routines and rituals of modern life allow)—but those cold weather coping strategies look strangely… reptilian.
See for yourself—next time the Weather Channel predicts a cold front, with or without a “wintery mix,” ask yourself if the people peeking out from fleece hoodies, swaths of scarves, turned up coat collars, and balaclavas as they hunch toward the warmth of home look more like bears… or tortoises.
Now, there’s a bit of Class warfare at play here, because homeothermic (body temperature largely uninfluenced by the surrounding environmental) hominid mammals aren’t often flattered by comparisons to scaly, poikilothermic (body temperature influence by the surrounding environment) cold-bloods. Knowing this, and well aware that my claim will face considerable skepticism, I’ll use an example to back it up: a familiar and easily identifiable semi-aquatic turtle called the red-eared slider (Trachemys scripta elegans).
Even nature neophytes will immediately recognize this species, a common resident of lakes and ponds in urban and suburban parks, as well as in pet stores. Shell, legs, head and tail are inscribed with stripes and nested ovals of green and yellow, the “elegant script” referenced in its Latin name (although the vibrant colors do tend to fade somewhat with age and a thick coat of algae). The red “ear” on either side of the head distinguishes the slider from all other North American turtle species and allows for a quick and definitive ID as they sunbathe on stones and logs. “Quick” being the operative word here; sliders don’t hear well, but they are very sensitive to vibrations that alert them to the presence of potential predators, and they can slip back into the safety of the water with surprising speed.
In the wild, the slider’s life cycle begins with courtship and mating as early as March or as late as July, depending on the region and the weather. Subsequently, the female heads for dry land to deposit a clutch of eggs, excavating with her hind legs to create a nest in the soil. Then she turns for home with nary a backward glance, and the turtles-to-be she leaves behind are on their own from that point forward. Two or three months later, depending on the average ambient temperature, hatchlings emerge from the nest and set out to conquer the world.
Most of them don’t make it past the first year—such is Testudine life… and death. Those who live to see their 2nd birthday, however, can reasonably expect a couple decades of celebrations, getting bigger with each passing year (females reach 10-13 in (25-33 cm), while males max out at 8-10 in (20-25 cm)).
In addition to predation, winter is one of the biggest barriers to longevity that young turtles must navigate in the wild (HA! I’ll bet you thought I’d lost my original train of thought, didn’t you?). No one expects to see a slider in a snowstorm, so it’s natural to assume they use sleep as a survival strategy. Hey, it works for two of the most diverse Orders on Earth—Chiroptera (bats) and Rodentia (rodents), so why not?
But reptiles take a different road. Brumation is a period of decreased activity, but it doesn’t involve the extreme metabolic changes that occur during hibernation. ‘Round about October, as temperatures dip below 50°F, sliders begin to settle in at the bottom of their preferred body of water, or in some cases under stream banks and tree stumps, and just… hang out. They’re less social, they move a little more slowly, sleep a little later, watch more television (I’m sure there must be a turtle equivalent), and generally feel lethargic and unmotivated. On warmer days, they’ll drag themselves up from the depths to stretch their limbs, have some lunch, and catch some rays with a few friends… but as soon as old Sol goes into hiding they follow suit, retreating into their shells to become stick-in-the-muds until spring.
Social commentators have come up with any number of marketable catch phrases to describe the human desire to turn our backs on a less than hospitable world—cocooning, burrowing, vegging out, even hibernating. The admen (and women) may argue that it doesn’t have the same sizzle, but what we’re really talking about here is brumating.
Sound like anyone you know?
Sometimes you just need to shut out the world for a while, you know?
If you can’t relate, I know the eastern box turtle (Terrapene carolina carolina) certainly can. Whether the threat is carnivores or towers of cardboard boxes and a demanding career, there are times when nothing beats a little self-imposed solitary confinement.
Carrying your own personal isolation chamber on your back means sensory deprivation can be achieved in mere seconds. No need to call ahead for an appointment at the local day spa. Don’t bother dimming the lights, closing the blinds, and turning off your cell phone. Just pull in your extremities and slam your hinged shell shut—a little privacy, if you don’t mind!
Is it any coincidence that box turtles are one of our longest-lived species, with well-documented cases of individuals reaching the half-century mark and beyond? Stress reductions, in the form of a room of one’s own, may well be the key to attaining a ripe old age.
We shouldn’t dismiss the importance of wise food choices either—lots of lean protein, in the form of earthworms, snails, slugs, and insects, as well as fruits and veggies such as berries, grasses, and flowers. Turtles have another favorite food that may contribute to overall longevity—they’ve been known to consume poisonous fungi, causing anyone who dines on their flesh to sicken, or worse. Of course, someone has to kill and eat said turtle, and suffer the consequences, which may not seem like much of a survival benefit unless you consider it from the standpoint of the population rather than the individual. See, all it takes is one or two bad meals and, ever after, turtles become a much less appealing meal for that particular consumer and his or her community. The technical term is adverse conditioning—that’s a polite way of saying animals (both human and non-human) tend not to keep eating things that make us vomit.
Now, it’s unlikely that turtles have any particular strategy in mind when eating wild mushrooms. Then again… certain “magical” fungi have been credited with providing, among other things, an increased sense of well-being and decreased anxiety levels. Perhaps they are self-medicating with the Terrapene equivalent of Xanax®.
One of six subspecies of the common box turtle (T. carolina), the eastern, like all its kin, has a highly domed carapace (the upper portion of the shell) and a hinged plastron (the lower half of the shell). What sets each subspecies apart is distribution and habitat, as well as certain physical characteristics. T.c. carolina, found from southern Maine to southern Florida and as far west as central Texas, is known for colorful keeled carpaces that feature diverse combinations of spots, bars, and radiating lines.
Color provides a clue to more than a box turtle’s species. It can also help us determine the gender of that lurching, resolute reptile we stop to help cross the street. If the eyes (irises) are bright orange or red, you’re holding a male; females have brown or light orange eyes. What if, in response to your good deed, the turtle has gone into hiding, making eye contact a moot point? Simply turn the creature over; females have a flat plastron, males are slightly concave. (Think about it. Birds do it, bees do it…).
The hinged plastron is what caused taxonomists to create a separate genus for North America’s box-top reptiles, and what allows the eastern and it’s relatives to retreat into a kind of biological fortress. And for most of their history, this survival strategy worked quite well—against coyotes, raccoons, and skunks, that is. Sadly, it doesn’t provide the same level of protection from every threat.
Box turtles are still relatively common throughout much of their range, but not even the most tightly closed shell can shield this species from the impacts of habitat loss and other interactions with Homo sapiens. These are slow moving, slow growing creatures with delayed sexual maturity and low reproduction rates, all of which puts them at risk. A female may produce hundreds of eggs during her lifetime, but less than a dozen offspring can be expected to survive to adulthood. It’s hard to even begin to estimate how many turtles are hit attempting to cross roads every year, and there are plenty of other hazard against which withdrawing into your shell is of little use—trains, lawn mowers, tractors, and bulldozers, to name but a few. Then there’s the capture of turtles for the pet trade. In many states, this practice is completely unregulated, with devastating impacts on wild populations.
Even so, there are times when coming out of your shell is the better choice. Especially for humans. Solitary confinement is used as a punishment because, unlike turtles we are social mammals. We need companionship, conversation, to touch and be touched. Hard to get any of those needs met when you retreat to your shell.
Unless, of course, you invite someone to join you there.
“Here’s a question for you… turtles and armadillos both have shells, so are they related?”
Whenever people gather for some kind of social event, the subject naturally turns to work. As in, “what do you do for a living?” In my case, what happens next is that the words “wildlife biologist” are out barely of my mouth before questions are spread before me like an appetizer tray. It’s a pop quiz every time you meet someone new, with no idea what subject the test will cover. Just when I think I’ve heard every possible query, I’m reminded once again that the natural world is far too diverse to ever allow humans to run out of questions, much less find all the answers.
Turns out, this particular gentlemen had just returned from a trip to Texas, so naturally he had ‘dillos on his mind.
If you look at them from the right perspective, turtles and armadillos do have some surface similarities. But turtles, as most people know, are reptiles; armadillos are mammals. Surprised? If so, you’re not alone. An armadillo just doesn’t fit the mammal profile. Where’s the hair… the teeth… the charisma?
Armadillos do have hair. It’s just that most of it isn’t in a form we recognize. The hard, shell-like covering is actually modified hair, with traditional strands between the jointed plates that allow the animal to curl up in a ball, protecting the vulnerable belly. Armadillo armor is similar to your fingernail, and at birth the shell is soft and pliable (a trait for which I’m sure Mom is grateful!), becoming harder as the young ones mature. Armadillos have teeth, but like their close relatives, the sloths and anteaters, they are small and peg-like. As for personality… I’ll admit, they may not be as winsome as an otter or as sleek and athletic as a cougar. But I’ve found them to be inquisitive and surprisingly nimble for a creature who lives life on the half-shell.
A turtle’s shell, on the other hand, is made of bony plates that have fused together and are connected to the ribs and spine. The shell is actually part of the skeleton, so that old Saturday morning cartoon trick, in which the turtle slips out of its shell, is possible only through the magic of animation. Of all the animals on Earth, only turtles and tortoises wear their hips and shoulders inside their ribcage. The shell continues to grow throughout the turtle’s life, and on some species you can actually see growth rings on each of the plates.
Even though they aren’t kin, armadillos and turtles do share one interesting characteristic: both are able to walk underwater along the bottoms of streams, ponds and lakes.
Why walk when you could swim? Great question, but one that will have to wait until the next party. I’m going to stroll on over to the buffet table and dive into the dip.