Near and Distant

[Photo: Steven Crane, CCL]

African elephants (Loxodonta africana) aren’t usually considered an urban wildlife species but I’d come a long way and wanted to see them while I was in South Africa. The built environment just doesn’t have the amenities Earth’s largest living terrestrial mammal needs to feel at home.  Africa’s elephants prefer dense forests, woodlands, deserts, and even the transition zones between these biomes to urban canyons and suburban savannah. Lucky for me, this study abroad excursion included several days at the Shamwari Game Reserve near Port Elizabeth in the Eastern Cape.

[© Gil Sinclair 2013, used with permission]

I also had the good luck to meet some relatives of the elephant while in Cape Town.  The rock hyrax (Procavia capensis) has found it much easier to adapt to city living than its country cousin.  I suppose concrete looks pretty familiar when boulders are your preferred abode. It also helps when you look much less threatening to the human neighbors throughout the hyrax’s Middle Eastern, sub-Saharan, and southern African range than their towering relatives.

Up on Table Mountain, which overlooks the city, hyraxes were everywhere: scampering along the pathways, basking on benches, happily whistling to one another, and enjoying the sunset from rocky precipices. Ignoring humans while living alongside them can be a good survival strategy for urban wildlife, and the hyraxes showed little interest in the two-footed visitors… unless some tourist with a camera decided to force the issue. Attempts to get the affable-looking creatures to pose were met with low “bug off!” grunts.

[© Gil Sinclair 2013, used with permission]

The family resemblance certainly isn’t obvious at first sight but keep in mind that the genealogical tree branched out millions of years ago.  Let’s start with stature:   adult elephants stand 10-13 ft (3-4 m) tall at the shoulder and may weigh over 8 tons, while an adult hyrax measures up at about 8-12 in (20-30 cm) and tips the scales at a whopping 8-9 lbs (4 kg).

Elephants have very little hair while hyraxes are covered in short taupe fur and long guard hairs that function like a cat’s whiskers.  With their small round ears it’s easy to see how they could be mistaken for a large guinea pig (rodent) or pika (cousin to rabbits and hares). Maybe that’s why they have so many aliases; in South Africa they are called dassie (Dutch for badger) or klipdas (Afrikaans for rock badger), Swahili speakers know them as pimbi, and in the King James Bible they’re referred to as coney (Middle English and Anglo-French). Even “hyrax” is misleading, originating from the Greek word “hyrak” or shrewmouse.

Taxonomists know you shouldn’t judge a book, or a beast, by it’s cover. Look beneath the binding and you’ll find a different tail. Make that tale.  For example:

  • [Photo: Andy Withers, CCL]

    Hyraxes don’t have trunks but they do have small pointed tusks and can deliver a ferocious bite when cornered.
  • Like elephants, hyraxes have flat, hoof-like toenails rather than curved claws.
  • Both are social mammals; elephants live in herds of up to 100 individuals, hyrax colonies can have up to 50 members.
  • Both have long gestation periods (22 months for elephants, 7-8 months for hyraxes) and offspring are slow to reach maturity.
  • Elephant and hyrax newborns are precocial, relatively mature and mobile shortly after birth.
  • Both species employ cooperative care for raising young. Elephant calves are tended from birth by both their mothers and other females in the herd; and hyrax pups are greeted and sniffed by the entire colony the day after they’re born.
  • Females stay with the group their entire life; males disperse.
  • Male elephants and hyraxes don’t have a scrotum; their testes remain in the abdomen even after sexual maturity.

The differences between elephants and hyraxes are more than skin deep, too.

  • Elephants must drink up to 50 gallons of water per day; rock hyraxes can survive for long periods on just the water they obtain through their food (although they dehydrate quickly in direct sunlight).
  • Neither animal is a ruminant, but hyraxes have a complex three-chambered stomach; elephants have a simpler but less efficient digestive system.
  • Hyrax stomaches are filled with symbiotic bacteria that help break down plant material; elephants have to consume up to 300 lbs of food per day, in part because they aren’t able to extract much nutritional value from what they eat.
  • [Photo: Abri du Plessis, CCL]

    An elephant spends a good portion of each day filling its stomach with food and water; rock hyraxes are world-class loafers who are inactive 95% of the time.
  • Hyraxes have poorly developed thermoregulation compared to other mammals so they need to sunbathe for several hours each morning to warm up and won’t venture out of their shelters on cold or rainy days. Elephants have to work at staying cool; they don’t sweat or pant but their large ears help to dissipate heat and they’ve developed a temperature regulation strategy that involves storing heat during the day and releasing it at night, similar to camels and desert rodents.
  • Elephants have a sixth “toe” and their feet have large subcutaneous cushions that distribute weight and absorb mechanical forces; hyraxes have a more flexible foot with a rubbery pad in the center that can be raised to create a suction-cup for clinging to rocks and moving across slick surfaces without slipping.
  • African elephants have no natural predators as adults (they have a decided size advantage) but their calves are vulnerable to attack by lions, crocodiles, leopards, and hyenas. Hyraxes have many predators and, as such, they feed in a circle formation, heads facing outward, eyes scanning for danger.

I’m told that most tourists who have a safari on their bucket list focus on the iconic African Big Five — elephant, rhinoceros, Cape buffalo, lion, and leopard.  I’d be the first to agree they’re all worth seeing in their natural environment, with no bars or moats to limit your view. Or theirs. 

But I find celebrity tours less interesting than exploring on my own.  I like to switch to hyrax-time, wander through neighborhood, sit at a sidewalk cafe or bask on a park bench and watch the residents, human and non-human alike, go about their day. Taking note of what makes us different and all the ways we’re related, despite the distance. 

© 2017 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work  but please ask).

Size matters

Next-Door Nature, toucan, song sparrow, beak size

When you’re trying to stay cool without air conditioning, it helps to carry a radiator on your face, large or small (Photos: Ame Otoko and Cephas, Creative Commons license).

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A scientists’ work is never done.

That’s because there’s always another layer to peel away, another stone to turn, another angle from which to view the situation.  Case in point—nearly 200 years ago, Charles Darwin made the connection between the size and shape of a finch’s beak and the availability of the seeds they eat; to this very day, no one has been able to produce evidence that undermines his observation and the conclusions he drew from them.

But what if there’s more to a beak than meets the eye?

That’s the question raised by Russell Greenberg of the Smithsonian Conservation Biology Institute. His theory—that beak size may also be an adaptation to temperature regulation and water conservation—has been bolstered by data from two recently published studies.  [Data collected, in part, by a newly minted PhD named Ray Danner. Ray just happens to be a member of my own adopted extended family, and if that name sounds vaguely familiar… well, regular NDN readers may remember that not too long ago I was bragging about another member of this ornithological power couple, Ray’s wife, Dr. Julie Danner.]

black-tailed jackrabbitSome years back, Greenberg noticed a difference in size between the beaks of sparrows living in salt marshes and those of sparrows settled just a kilometer or two further inland. Then a paper published in 2009 reported toco toucans (Ramphastos toco) may lose as much as 60% of their body heat through their long bills, based on thermal imaging and similar to the role played by the large ears of both elephants (Elephantidae) and jackrabbits (Lepus spp.). While many ecologists assumed toucans were a special case, Greenberg wondered—might other birds have evolved larger or smaller beaks to discharge or conserve heat as well?

He chose to test his hypothesis by applying thermal imaging to a subject with a much less prominent proboscis—the song sparrow (Melospiza melodia).  Native to North America, everything about these feathered minstrels is miniature compared to their South American kin. The toucan weighs in at 1-2 pounds (the large bill doesn’t actually tip the scale as much as you might think since it’s mostly hollow) while at 0.4—1.9 ounces the song sparrow is definitely a featherweight.

In the first study, two subspecies were examined. On average, the beak of an Atlantic song sparrow was found to have 17% more surface area than that of the eastern song sparrow, although both birds have similarly sized bodies. Based on the Greenberg team’s calculations, the Atlantic sparrow loses 33% more heat than it’s inland neighbor. The finding suggests beaks may play a role in thermoregulation for a wide variety of bird species.

The ability to stay cool when the ambient temperature rises is critical to survival, but how one gets rid of the excess heat is just as important.  Birds don’t sweat—they pant… and lose not just heat but water in the process. This summer, residents across the U.S. have been reminded just what a precious resource water can be, and never more so than for all the creatures without easy access to a faucet.  Greenberg and his colleagues suggest that a bird’s beak can function like a radiator, releasing heat without losing water. The Atlantic sparrow’s larger bill saves the bird about 8% more water than the smaller beaked eastern sparrow. That may not sound like much but during a hot, dry summer it could be a significant survival advantage.

The second study examined museum specimens of song sparrows collected on the other side of the continent, along the California coast. Sure enough, as maximum temperatures increase, so did beak size… with one caveat.  When the maximum temperature was higher than 98°F (37°C) beaks got smaller… just as was predicted by the original hypothesis. You see, if you took a song sparrow’s temperature the thermometer would read about 105°F (41°C). When the air temperature exceeds the bird’s own temperature, as it does in some regions, a larger beak could actually begin to absorb heat.

While the Smithsonian group has demonstrated a connection between climate and beak size, there’s still plenty of work to be done. For the new hypothesis to garner support, scientists need to see data that ties survival of wild birds to beak size-related heat dissipation.

Meanwhile, the fact that diet influences beak size and shape hasn’t changed—Darwin can continue to rest in peace. But as so often is the case, the more we discover the more we realize just how rich and complex this world and its inhabitants are … even an Earthling as seemingly plain and simple as a sparrow.

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love-earthThis blog, like so many activities that foster support and appreciation of the natural world, is a labor of love. If you’ve enjoyed learning about the creatures who share our built environment, consider becoming an NDN Benefactor with a donation of any amount you’re inspired to give. If you’d like to find a little Next-Door Nature surprise in your inbox just click the Subscribe!  button in the upper right-hand corner of this page and receive notifications of new posts!

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© 2012 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work; all you have to do is ask). Thanks to these photographers for making their work available through a Creative Commons license: [from the top] Ame Otoko (toco toucan); Cephas (song sparrow); James Marvin Phelps (black-tailed jackrabbit); Mr. T in DC (house sparrow on drinking fountain); David Craig (song sparrow in hand).

Hot and cold

next-door nature, urban wildlife, fence lizard

Everyone, even fence lizards and other ectothermic creatures, are feeling the heat these days (Photo: Bandelier National Monument, Creative Commons license)

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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!

next-door nature, urban wildlife, fox squirrelAlas, 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 next-door nature, urban wildlife, sunbathersconditions 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.

next-door nature, urban wildlife, gray treefrogWhen 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.

next-door nature, urban wildlife, echidnaMoving 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.

next-door nature, urban wildlife, elephant shrewOne 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.

next-door nature, urban wildlife, crocodilesC’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).

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© 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: Bandelier National Monument (sunning fence lizard); Michael V. Flores (fox squirrel cooling down); Nick Papakyriazis (sunbathers); geopungo (gray treefrog); BohemianDolls (elephant shrew); and Jess Loughborough (basking crocodiles).