Archive for the 'Mammals' Category

Oct 30 2013

Hanging On By His Thumbs

Published by under Mammals

Spix's disk-winged bat (photo by Alan Wolf via Creative Commons license)

Here in eastern North America we’re gaining a new appreciation for bats, not just as Halloween symbols but as insectivores, because several of our species are threatened with extinction due to white nose syndrome.  The bats most at risk are those that roost in caves where cool moist temperatures allow the Pseudogymnoascus destructans fungus to grow and infect them.

Spix’s disk-winged bat (Thyroptera tricolor) is far removed from this danger because he lives in the tropics and roosts inside curled leaves.  He recently made news in the journal Nature because scientists discovered he uses the curled leaves as an ear trumpet.

Leaf roosting has made him unusual in other ways, too.  Most bats roost head-down but this species roosts head-up so it can exit the leaves quickly.  Leaves are smooth and slippery so the bat has evolved suction cups on his wings and feet.   These cups look like disks, hence his name.

Above, the bat is showing off his wing disks but his arms look really weird and stubby.  To understand this it helps to know a little about bat-wing anatomy.

Bats’ wings are made of skin stretched from their armpits to their fingertips. Their four fingers, encased in thin skin, have evolved to be very long to give the wings their breadth.  Bats’ thumbs, however, are not inside their wings and their thumbs are short.

Bat wing showing thumb sticking up (from a photo on Wikimedia Commons)

In the photo above you can see the attic bats’ long fingers.  The joint of the wing is at the bat’s hand/wrist.  I’ve circled the tiny thumb. This one has a claw but Spix’s disk-winged bats have a suction-cup there instead.

When bats roost, they close their fingers to fold their wings.  Most bats grab a perch with their feet but Spix’s uses suction cups to latch onto the inside of the leaf.

Suction cups on his feet alone are not enough.  This bat is hanging on by his thumbs.

 

(photo of a Spix’s disk-winged bat taken near Golfo Ducle, Costa Rica by Alan Wolf.  Bat wing from Wikimedia Commons. Click on each photo to see the original.)

p.s. Thanks to Peter Bell for alerting me to this fascinating bat.

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Oct 16 2013

Deer Among The Dead

Published by under Mammals

 

On Monday I described how American Indians shaped the landscape before European arrival.  We shape it too, though we don’t always realize how.  Case in point: There are more deer in North America now than there were before Columbus landed in 1492.

Because deer are a prey species, their abundance is tied to their predators.  When American Indians ruled the continent they hunted deer for food and to control the population so the animals would not decimate their crops.  They knew that either no deer or too many deer meant less food.

European Americans are still figuring out how to balance the deer population.  We overdid it a century ago by uncontrolled hunting that killed all the deer in Pennsylvania.  Uh oh!  Pennsylvania passed hunting laws and imported deer from Virginia to repopulate our state.

Now we’ve erred on the other side.  We’ve eliminated the deer’s other predators and protected them from hunting so well that their population has exploded into every nook and cranny including city neighborhoods.

Sharon Leadbitter spends a lot of time photographing nature at Allegheny Cemetery in the city’s Lawrenceville district.  Deer are often her photo subjects because they’re everywhere.  In a conversation with the president of the cemetery she learned that about 300 deer live there in three herds.  This is way too many deer for the land to support so they move throughout the neighborhood eating gardens, shrubs, flowers and handouts.

Since most of the “inhabitants” are dead and the living come quietly to pay their respects, the cemetery’s deer are almost tame.  Sharon says this is both a blessing and a curse, “Some of the blessings are that the deer will eat out of your hand if they know you. The curse would be this great interaction. People feed all manner of things to these animals. White bread, cereal, I’ve even seen a candy bar being fed. It only takes once for someone to be bitten or kicked. These are not pets but because the animals have lost most of their healthy fear, people don’t realize that they are still semi-wild.”

Deer browse and gambol among the headstones, unconcerned by living visitors.  Sharon filmed a fawn playing among the tombstones last June while his mother watched.

“The cemetery is a great place to have some quiet time and reconnect with nature,” says Sharon. “Come check it out but always maintain a respectful distance, or even better stay in the car”  when you visit the deer among the dead.

(video by Sharon Leadbitter)

11 responses so far

Oct 09 2013

Cute, Curious, Combative

Published by under Mammals

Red squirrel (photo by Shawn Collins)

So cute!  But watch out, he’s fierce.

His small size, soft red fur, fluffy tail and big eyes are certainly cute but the red squirrel is also curious and combative.  I think his food habits made him that way.

Unlike gray and fox squirrels, red squirrels (Tamiasciurus hudsonicus) don’t bury one nut at a time.  Instead they gather food in a big cache called a midden in a hollow tree or underground.  This takes a lot of time and effort:  climb the trees, walk the branches, bite off the green cones, watch them fall, scurry down later and collect the cones, repeat the process. Along the way they pause to eat at the same prominent locations leaving debris piles, also called middens, that seem to say “I am here!”

The red squirrel defends a 1 – 8 acre territory against everyone, especially other red squirrels.  He’s curious about new arrivals but then, watch out!

First line of defense?  Shout at the competition!  Burst into a sudden loud chatter that slows to a wheezy hiccup.  Really mad?  Jerk your tail and stamp your feet.  Really, really mad?  Chase!

In coniferous forests that’s usually another red squirrel but in mixed forests gray squirrels also get a verbal beating and relentless pursuit.  Though the red squirrels are only 1/2 to 1/3 the size of the grays, the red ones always win.

I, too, have been ejected from a red squirrel’s territory.  He used his voice.  Click here to read about it.

Now that winter is coming the red squirrels are changing into their drabber winter coats and rushing to increase their middens.  They have no patience for anyone.

Cute… ?

Don’t push me!

(photo by Shawn Collins)

5 responses so far

Aug 30 2013

Head-to-Head in Elk County

Published by under Mammals

Bull elk sparring (photo by Paul Staniszewski)

Looking for some excitement?  Want to see large animals go head to head this fall?

This week Paul Staniszewski of Elk County reminded me that the elk rut has begun.  He wrote:

Labor Day usually marks the end of summer. For the Pennsylvania elk herd the shortening length of daylight hours each day triggers an annual event known as the “rut”. The rut usually lasts from late August until mid-October.  … A lot of sparring between bulls takes place that makes for dramatic photographing opportunities.

Male elk bugle and spar to establish dominance in the mating hierarchy.  They’re so preoccupied that Paul has captured some great photos, especially near the Visitor Center on Winslow Hill Rd in Benezette.

Benezette is a 2.65-hour drive from Pittsburgh so you might want to make a weekend of it.  Plan your trip and learn more about the elk here.

(bull elk sparring by Paul Staniszewski)

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Aug 05 2013

Every Dolphin Has A Name

Published by under Mammals

A Bottlenose Dolphin plays in a boat's wake (photo from NASA archive via Wikimedia Commons)

We’re used to the notion that we name dolphins (remember Flipper?) but did you know that dolphins name themselves and call each other by name?

Last month in the Proceedings of the National Academy of Sciences, researchers from the University of St. Andrews in Scotland published a study of bottlenose dolphins (Tursiops truncatus) that explains how dolphins communicate by name.

Using underwater microphones they recorded dolphins’ voices and discovered that each one had his own unique whistle, a signature sound.  Having matched the signatures to individuals they then played back the sounds, one at a time.  The dolphin who “owned” the sound responded.

This is just like what humans do.  If you call out “Kate,” I’ll respond — if I hear you.

Hearing is probably the reason why dolphins have named themselves.  They live in a world where it’s hard to see but easy to hear (sound travels better in water than in air).  They also live in a social group that’s always on the move.  When a friend has swum out of sight they call him and the friend answers.   This makes it easy for the group to stay together.

Researcher Vincent Janik points out that individual communication is also important for mothers and calves. Baby dolphins rely on their mothers’ milk until they are three years old yet they’re just as mobile as their mothers.  What an advantage that they can call each other by name!

Read more about the study and see a video of the research at this link at BBC News.

 

p.s.  This confirms my belief, garnered from T. S. Eliot’s Old Possum’s Book of Practical Cats, that many animals have their own secret names.  We just don’t know what they are.

(photo from Wikimedia Commons. Click on the image to see the original)

One response so far

Jun 25 2013

They’re Off the Clock

Published by under Bird Behavior,Mammals

Svalbard reindeer (photo from Wikimedia Commons)

Last Friday the solstice set our annual biological clocks.  Every day the sun triggers our circadian rhythm. But what if we lived where the sun never sets?  How would we synchronize our daily internal clocks?

In the arctic where day and night last for months a circadian rhythm would be annoying if not a handicap.  Since “day” has no meaning, arctic reindeer solved the problem by turning off their internal 24-hour clocks.

In mammals the circadian rhythm causes melatonin levels to rise at night and fall during the day.  This happens whether or not the sun gives us a cue.

Scientists studying reindeer in Norway (Rangifer tarandus, the same species as caribou) found that they have no rhythmic melatonin cycle.  Instead their melatonin rises or falls abruptly in response to light.  On or off.  No daily clock.

Reindeer need to know the time of year so they can synchronize migration and breeding, but this is easy to do at the equinox when the sun rises and sets.

On Svalbard where this reindeer lives, the sun rose on April 16 and won’t set until August 27.

No wonder he doesn’t care what time it is.  Some days I wish I didn’t care either.

Read more about this study in Science Daily, March 2010.

 

(photo of a Svalbard reindeer, a subspecies of Rangifer tarandus, from Wikimedia Commons. Click on the image to see the original)

One response so far

Jun 19 2013

I’m a Porcupette

Published by under Mammals

Porcupine youngster, Lycoming, May 2013 (photo by Meredith Lombard)

When I saw this cute photo by Meredith Lombard I knew I had to write about baby porcupines but I soon learned that the truth about these rodents is stranger than fiction.

For starters, baby porcupines are called porcupettes.

Each porcupette is a precocial only child, born with open eyes, well formed teeth, a full coat of fur, and able to climb trees a few hours after birth.  In only two weeks he eats green plants.  In three months, he’s weaned.

Like his parents he has three kinds of fur: a wooly undercoat, long coarse guard hairs, and sharp hollow quills with barbs at the tip that slant backward.  When born his quills are soft and harmless (good thing for his mother!) but within half an hour they’ve stiffened into the protective coat that saves his life.  The only place he doesn’t have quills is on his belly — just like his parents.

Neither he nor his parents “throw” their quills but the quills are so loosely attached that they stick easily to any critter that comes close.  That includes dad when he approaches mom to conceive a porcupette. Needless to say copulation is a very careful business.  No hugs are involved, but there’s a lot of courting to get her in the mood.   Dad whines and dances on three legs, showing her his equipment.  When she says “You’re the one” he showers her with urine.  Then they mate.

I’m not kidding.

All of this happens in October or November.  Seven months later: a porcupette.

(photo by Meredith Lombard)

3 responses so far

Jun 13 2013

Deer Are Not Vegetarians

Published by under Mammals

While hiking in the Laurel Highlands several weeks ago I heard a hooded warbler alarm call.  I looked for the bird and discovered a large deer browsing in the area of the warbler’s voice.

Though I couldn’t see the warbler I knew why he was upset.  Deer eat birds’ eggs, baby birds and any small bird that can’t fly away.  The deer was as big a threat to his nest as a bear.

Years ago at Powdermill Banding Station I learned that deer are one reason they’re careful to quickly retrieve birds from the mist nets.  If they delay, deer eat the birds trapped in the nets.

In the video above two parent birds try to drive off a buck who’s browsing in the vicinity of their nestling.  The nestling tries to escape but cannot fly well.  The parents’ efforts were to no avail.

Deer are so omnivorous that trail-cam studies have shown they’ll readily eat from carcasses of their own species.

Nature is full of surprises.  Deer are not vegetarians.

(video from YouTube)

 

7 responses so far

May 14 2013

Not Tame, But Trusting

Published by under Mammals

Doe and fawn (photo by Sharon Leadbitter)

It used to be that wild animals avoided human contact but that’s not true in Pittsburgh anymore.  We have hawks, wild turkeys, foxes and deer in the city.  Not every animal can cope with city life but the individuals who can tolerate close human approach are doing quite well in our parks and cemeteries.

Sharon Leadbitter visits Allegheny Cemetery often and frequently saw this doe and fawn last summer.  They weren’t tame but they learned that Sharon isn’t dangerous. This was reinforced for the fawn every time it met a human and Mom said “It’s ok.”

Fawns are born in May in Pennsylvania so by now this baby is an adult and it’s mother has a new fawn.  I’ll bet this doe will let Sharon meet her new fawn, too.

And there will probably be four deer this year.  This doe plus her new fawn, and this fawn (now an adult) plus her fawn.  That’s how easy it is to end up with a lot of deer.

(photo by Sharon Leadbitter)

6 responses so far

Apr 11 2013

Raccoons Getting Active

Published by under Mammals,Schenley Park

After a quiet winter this week’s warm weather has brought out the raccoons.

On Monday I heard a strange noise above my head in Schenley Park.  Two raccoons were arguing high in a tree.

Then late at night I heard the scratchy sound of raccoons disagreeing in my back yard.  Safe indoors, my cat looked in the direction of the sound but was unimpressed.

Fortunately we don’t have a cat door or we might have had a visitor like the one in this video… !

 

(video from YourDailyFunny on YouTube)

2 responses so far

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