Archive for the ‘Biology’ Category

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The Amazing Ant Lion

January 1, 2018

Someday, in your travels, you might spot a small round hole in the dirt, about the size of a drinking straw.

And even better, surrounding the hole, there might be a downward pointing cone of dirt or sand, maybe several inches across, leading down into the hole.

If you see both of these, you may have found the dwelling of an Ant Lion, or as it is sometimes spelled, Antlion!

antliondigP1050931V4

(The cones in this image are about 2 inches across)

Given the size of the hole, you may suspect this creature is not really a lion, and you would be right.

But it is not an ant either! To the regret of nearby ants.

In fact, to an ant, it must seem as fierce and deadly as a lion! Because the whole point of the hole in the ground and the slippery-slope funnel-cone leading down to it is to trap ants, which will then be grabbed by the horrific looking jaws of the Ant Lion, injected with venom and enzymes, and sucked completely dry of life!

Yiiiiikes!

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Crazy-ferocious Ant Lion, photo courtesy of Phil Meyers

It sounds like something from a horror movie! So much so, in fact, that the Ant Lion was used as a model for a sand-dwelling monster in the movie Dune!

Like many other insects, Ant Lions go through several surprising life stages. As adults, Ant Lions look like frail dragonflies, who fly around for a few days, then lay eggs and die.

The eggs eventually hatch and grow into larvae, what we usually think of as worms or grubs. Ant Lion grubs are certainly remarkable looking, with those immense jaws, sticking out front like lobster claws. Their bodies, generally an inch long or less, are covered with dark hairs and bristles, adding a wild and wooly look to their ferocity.

And here’s another clue—near the sand-funnel with the hole at the bottom, you may notice a meandering trail in the dirt, like a little ditch. And this wandering line, which looks something like a doodle you might draw on paper, gives the Ant Lion its other name—the Doodlebug!

But why do they do the doodling they do?

Well, look at the size of their jaws! Because their jaws are so enormous compared to their body size, they have to walk around backwards! You would probably meander too, if you had to walk around backwards all the time.

Ant Lions are so clever that they are found all over the world, so you can look for them even if you are not in the desert. And, given how many kinds there are, when being formal, we will not be specific, but just call them by their family name, Myrmeleontidae.

So watch for, and warn any ants, if you see the signs of these remarkable predators!

 

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Who made a saguaro hole in one?

March 26, 2017

Out in the desert, you may hear a loud “Chirrr” sound. Look up, and you may see a flash of black and white wings, then see a brown-headed individual running or hopping up the trunk of a tree, if there are any trees around, or a cactus. If it’s a cactus, that’s got to be a fairly death-defying move, navigating among the thorns.

When you see all of these clues together in southern Arizona or northwestern Mexico, it’s quite likely you have spotted a Gila Woodpecker.

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You can recognise Gila Woodpeckers, Melanerpes uropygialis, both male and female birds, from the thin vivid black and white bars across their wings and back, and their brown heads. In addition, the male has a red patch on his forehead. And, as well as their distinctive “Chirrr” call, they also make loud peeps.

In an unusual and clever tactic, they use their tails to prop them up vertically as they locomote, hunting for insect meals on bark or cactus skin, or when they hammer out nests.

The big black holes you see in the sides of many saguaros? Credit goes to these folks!

They use their strong beaks on their well-cushioned heads to whack nest holes into the sides of saguaro cacti, and if they can find any, other tall woody plants of the desert, including cottonwoods.

The nest holes they excavate in saguaros, which are often used by other birds, eventually harden into “saguaro boots.” These woody, rounded, boot-shaped forms remain even after the saguaro dies, and have been used as containers by humans since the olden days.

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See nictitating membranes in action!

March 24, 2016

There’s a great nature event happening right now. Biologists have set up video cameras to watch a growing bald eagle family in the US National Arboretum in Washington DC, and anyone with an internet connection can watch them at any time.

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You can visit the DC EagleCam, 24 hours a day, at  http://dceaglecam.eagles.org

Even though this is the east coast, bald eagles also winter in the desert, usually in the high country. But the relevant  feature right now is that sometimes you can get a glimpse of the eagle’s nictitating membranes at work.

Here’s how. It’s best to watch in the day time. Click on one of the two cameras so you can more easily see the adult eagle’s eye, and enlarge the image, by clicking the bracket-box at the lower right corner of the video.

You will most often just see the eagle blinking–but every so often, you get to see the “third eyelid” swipe part way or all the way across the eye, starting from the corner nearest the beak. Wow!

And if you get so busy watching the adults and chicks and their activities you forget the third eyelid, that’s OK too!

…..Image taken April 6 2016 from dceaglecam.eagles.org © 2016 American Eagle Foundation, EAGLES.ORG

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Check out the nictitating membranes!

February 20, 2016

If you had to make your living in a desert, or under water, or by sticking your head into a rotting carcass to get your food, you’d probably appreciate a handy combo of goggles and windshield wipers.

And that’s what many creatures, including Turkey Vultures, have.

But instead of using the awkward term “combo-goggles-windshield-wipers,” we use the sleek and easy to remember name, “nictitating membranes.”

Uh huh!

Nictitating membranes are also called third eyelids, and are often translucent, so the eyes get protection while allowing some vision.

Sometimes these thin membranes rest under the lower eyelid, and rise from there, but more often, they are tucked into the corners of the eyes nearest the nose, and move back toward the sides of the head when in operation.

It can be unnerving the first time you see them in motion, a space-alien moment. But when the membrane is closed, it often just looks like a gray or white eyelid.

Here’s a Turkey Vulture doing a demo for you!

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First picture, nictitating membrane is open, and in the second, the translucent membrane is covering the eye.

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Who’s standing tall and alone?

December 19, 2015

A striking sight in the Sonoran desert is a lone saguaro cactus.P1150608.jpeg

Saguaros (Carnegiea gigantea) provide food and shelter to a surprising number of creatures. This includes humans, who harvest their fruit, and use their skeletons for fences and construction.

These cacti have an amazing variety of adaptations to the desert.

First, check out the color of the stems, a pale green, indicating they contain chlorophyll. Since saguaros do not really have leaves, the stems have to do the work of photosynthesizing and producing food. The pale color keeps the plants from absorbing too much hot sunlight and getting burned.

If you look closely, you will see lines of defensive thorns on vertical accordion ridges. The whole plant can expand to hold more water after a good rain, then accordion back in as it uses the water

What you can’t see is the root structure. Instead of sending down a big tap root, like many plants, they send out numerous very long horizontal roots near the surface, to better gather any moisture nearby.

That’s why they’re lonesome looking—they need to grow far apart. And that’s why, in the old days before we realized it was unethical, (now it’s also illegal) people would dig them up in the desert, transplant them, and they would die, because the majority of  the root structure was left behind.

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Did You Hear a Droplet?

December 17, 2015

Sometimes in the desert, you may hear a loud and distinct sound like a very large droplet of water dropping into a pool.

The droplet-dropping sound is actually the call of a Curved-billed Thrasher, a brown bird with a distinguished down-curving bill and surprising orange eyes.

Curved billed thrasher

The Cornell bird labs characterize the call as a sharp, whistled “whit-weet”at their website www.allaboutbirds.org

Perhaps it only sounds like water to parched desert dwellers.

These birds, relatives of mockingbirds, live in the southwestern United States deserts and through much of Mexico.

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Wildlife Rescue Open House

November 13, 2015

If you are near the Phoenix, Arizona area next weekend, you have an opportunity to meet and learn about some of the cool creatures of the hot desert.

The open house is on November 21 and 22, 2015, at the Adobe Mountain Wildlife Center.

www.azwildlifecenter.net/events.asp

Because this is a wildlife rescue station, the population changes all the time. Depending on who is recovering there, you may see eagles, desert tortoises, bobcats, falcons, or ringtails.

Or maybe even the creative and industrious packrat!