Dung Beetle Navigation

Dung beetles- Wikimedia

Many mammals and even the lowly box turtle can navigate by memory of the territory.  Some birds can even navigate by the stars. But dung beetles using the Milky Way?  Now that is an amazing story, as told in the New Yorker.

It begins with a dung beetle which shape its new found treasures into a ball and then laboriously rolls it away to an ideal place of burial.  There the female deposits a single egg in the dung which will serve as nourishment as well as home until the larva reaches adulthood.  I can only imagine its relief as it steps into the fresh air, but likely the beetle doesn't mind either way.

It has long been noted that dung beetles steer a perfectly straight course, a matter of efficiency as well as reducing the time they are exposed to competition for their prize or danger from a predator.  Just why any thing would want to eat a beetle rolling a ball of dung is a matter of conjecture.  Here we will concentrate on its navigation ability.

In the daytime, the beetles use the sun for their straight line navigation.  Sunlight is polarized and the beetles have special receptors that read the polarization.*  In 2003, Eric Warrant, a biologist at Lund and his colleagues determined that nocturnal dung beetles could navigate by the polarized light of the moon.  They also noticed that the beetles traveled relatively straight on moonless nights as well.  Since the beetle's compound eye could not detect a single star, the answer must have been the Milky Way.

A team led by Marcus Byrne, a zoologist at University of Witwatersrand studied the beetles on a box-like table which obstructed the view of trees etc.  Then they ran them with either clear or tiny black hats which blocked the view of the sky (I am not making this up) and showed that they navigated only when the sky was visible.  Finally they took them to a planetarium.  The beetles were lost when exposed to only the 18 brightest stars but were back on track when using the artificial Milky Way!  More detail in the New Yorker article.

Research like this might sound like a worthless study worthy of the Golden Fleece awards given to science that initially seems without merit.  Once again, there can be a practical application to pure research.  In this case, it comes from learning more about beetle vision.  Researchers are developing a few devices modeled on the talents of lowly insects. 

Nature.com shows how the compound eye of beetles have inspired a new type of camera, miniaturization including a large assembly of independent lens that keep objects in focus as they move away.  Another group shown at this site has developed a tiny flybot, a flying robot with flapping wings like its fly namesake.  You can watch it fly at this at NPR.org.

Flybots- NPR, Kevin Ma, Pakpong Chirarattananon/AAAS/Science

* Incidentally, polarized light is used on digital camera LCD screens.  If you are wearing polarized sunglasses and turn your camera 90 degrees, the screen appears black.  You aren't going blind, just a victim of modern technology.  Digicamhelp.com.
 

A Ballooning Risk

Virtually every aspect of our society has some downside risks to nature, not all of them obvious.  Most of you are familiar with the risk that birds face from wind farms, cars, windows, cats and even rice at weddings.  Jet engines are a risk to birds and vice versa.  But balloons?  It turns out that the release of balloons, both individually and in large numbers at events present a risk to our feathered friends.  A story in Birding/ About.com explains.

1. Balloon fragments and deflated balloons are a choking or intestinal obstruction hazard to birds that mistake them for something edible.
2. The strings and ribbons tied around a balloon present the risk of tangling their feet, similar to the problem with fishing line.  Tangle injuries can occur to nestlings when these materials have been incorporated in the nests.
3. There is an indirect effect of expanding rubber plantations which displace diverse habitats.

We commonly find balloons and fragments out in the wild where they have landed or tangled in our trees.  This form of litter joins "Walmart balloons," i.e. airborne plastic bags on a windy day, as an environmental eyesore.  In 2008 Walmart announced their commitment to reducing the number of plastic bags used.  We have long suspected that their switch from distinctive blue bags to glaring white bags blowing in the fields around your nearest Supercenter was to hide their source.

It turns out to be more complex than that.  The white bags are also less recyclable.  Colored bags can be made with more recyclable material than white bags according to earth911.com.

"Essentially, the darker a bag is, the more recycled content it can contain. A white plastic bag can only contain about 10 percent recycled content, which is typically only post-industrial, not post-consumer, waste. A blue bag can contain about 35 percent post-consumer recycled content, with gray bags moving closer to 40 percent. "  earth911.com

So why are there so many white bags around?  Like Mr. Robinson's whispered answer "Plastics" in The Graduate, the secret word here is marketing.  Simply put, store logos don't show up well on gray or blue bags.  How important is that?  Probably not very, but tell that to the person getting big bucks to promote your store.

The good news is an estimated 45-60% of plastic bags get re-purposed by consumers, lining trash cans and picking up dog poop.  A bigger disappointment is the volume of bags actually recycled.  With available techniques, they can get close to 100% recyclable materials in a plastic bag but that doesn't help if the bag doesn't get recycled.  Once again, the weak link in the recycling chain is between the consumer and the availability of convenient recycling options.

Pollination Season

Nectaring Bat- TED Video

Watching zebra swallowtails nectaring on the tiny flowers of early spring reminded me that we are entering the big pollination season.  Not only are the bees and butterflies out, but flies are starting to warm up to the brown flowers, drawn by the false smells of dead stuff.  In the words of our friend Sarah, they flowers use insects as their sexual servants.

This beautiful TED video will get you ready for summer, seeing natures wonders closeup as only modern cameras can.  It is a reminder of the broad array of creatures which pollinate our plants and the complex web of nature.

Darya's Anna's Hummingbird

Click to enlarge

Our nine year old granddaughter Darya who lives in Berkeley, California recently sent us a little research she undertook after reading up on Anna's hummingbirds.  Her mother took the pictures and here is the story in Darya's own words.

"While my mom was pruning our Angel's Trumpet tree, she discovered something on the Chinese bell hanging on a low branch. At first she wasn't sure about it, but then she found out it was a hummingbird nest.  In addition to the nest there were two small baby hummingbirds. She called me and my sister over and we looked at it for a while.  I felt excited and happy because last year we had a hummingbird nest in our "fruit salad" tree in the front yard. It's not every day that you see a hummingbird nest in somebody's yard."

"We were excited to show others.  My dad suggested to do some research on the hummingbirds.

I started to chart how long the mother bird fed her babies and how long she was gone between feedings.  Based on what I read, a mother hummingbird spends about twenty minutes between feedings. I decided to put up a hummingbird feeder and test if the time between feedings became shorter. Because hummingbird mothers make a slurry of bugs and nectar to give more protein to their young, my guess was that it would still be around twenty minutes between feedings because she would still have to catch insects."

Researcher recording observations

She sat patiently timing the intervals between feedings and the time in seconds the mother spent in feeding the babies.  She then put up a hummingbird feeder nearby and timed the intervals again, to see the effect of nearby food on intervals between feeding.  As the babies were nearly full grown, she only got to time a few feedings with the feeder present before the babies fledged.  Afterward the mother returned and started salvaging parts of the former nest.  Darya's conclusions follow.

"Our limited observations showed that when the feeder was present the time between feedings was shorter (22 minutes versus 24.2 minutes) but I only got to observe the birds for a few feeding times after we put up the feeder. It's hard to say that if I had watched longer, I might have got different results. It does seem that the average time between feedings I observed was very close to the 20 minutes we read about."

 

Editor's note:  This study was published entirely on its own merits, ignoring the fact that the author was our granddaughter Darya..... more or less.  The original report is reproduced here.

Invasives From Nowhere

Autumn Olive

Invasive species seem to arrive from nowhere.  A pleasant hike around our pond, looking for amphibian eggs was interrupted when Steve and Amy identified a healthy autumn olive growing on the bank.  This was a long way from nowhere, apparently arriving by airmail in the intestinal tract of an unwitting bird.

I wasn't aware of the identifying features but once you see them they become obvious.  Steve pointed out the silvery green underside of the leaf with its distinctive silver scales.  distinctive if you know what to look for.  The twigs are light brown with prominent silver and brown scales.  The older, thicker branches are armed with sharp thorns.

Note brown scales, thorns

Silver scales- Click to enlarge

Autumn olive or autumnberry, Elaeagnus umbellata, is part of a long line of "it seemed like a good idea at the time" plantings such as sericea lespideza that were touted as excellent sources of erosion control as well as good for wildlife.  It is true that some species of birds eat the berries, but the bad outweighs the good.  

"It was studied in the 1940s by the Soil Conservation Service, and the strain 'Cardinal' was released in 1963 for commercial propagation. In the eastern and central United States, autumn olive was planted to provide food and cover for wildlife, as screens, windbreaks and barriers along highways, to stabilize and revegetate road banks, and to reclaim mine spoil. For some years after planting the plant seems contained, but then it suddenly becomes invasive and difficult to control."  MDC

These invaders spread rapidly, grow into dense bushes or small trees and shade out native species.  By suppressing diversity, they choke out many native species which are also insect host plants.  Insects are important links in the food chain.  A dense field of autumn olive can reduce the species of butterflies, moths and their caterpillars plus other species that insectivorous birds that depend upon.  Its ability to fix nitrogen, somewhat unique among shrubs, is another negative as many native species in prairies, savannas and woodlands don't tolerate large amounts of nitrogen in the soil.

Some sources tout the "autumnberry" as a food source.  We are proponents of eating garlic mustard in salads and sandwiches, obtained as we pull the invaders out of the ground.  My concern with autumnberry is the fact that harvesting the berries does little to control the spread.  People developing a taste for them may be tempted to protect their source rather than destroy it, or worse yet, plant it.  What ever they taste like, it can't make up for the damage to our Ozark environment.

Treatment of our autumn olive shrub started with my trusty Stihl, followed by Barb's loving application of concentrated Vitamin G glyphosate) on the cut stumps.

This MDC site has comprehensive information about control.

Bombardiers, True and False

One advantage of country living is that you don't always have to go out to find nature - sometimes it comes in to find you.  Last Friday I saw this ground beetle crossing the living room floor, intent on finding safety under the couch.  It wasn't too happy to end up in the box, but at least it didn't let fire its defenses at me.

This is a false bombardier beetle, most likely Galaretia bicolor or possibly G. janus.  The two species are both common and similar in appearance.  The head and pronotum shapes are somewhat different, but I don't have the ability to separate them without a key and a lot more knowledge.  My guess is G. bicolor but go to bugguide.net and make your choice.


Galaretia are said to be found in forested areas, in or under decaying or rotting timber.  This didn't give me much confidence in our cabin flooring until I found a number of sites recording finding them in houses and basements.  They are carnivorous predators, eating primarily caterpillars and other insects.  I imagine they think they are in a cafeteria in our creek house which is seemingly porous to all invertebrates (and a few vertebrates of mouse-like inclinations). 

False bombardier beetles demonstrate that chemical warfare is nothing unique to humans.  It has glands on the abdomen which produce formic acid with a little acetic acid thrown in for good measure.  This produces a noxious odor, discouraging predators and can cause a burning sensation on the skin.  They have two side-by-side glands and nozzles and can selectively spray the side that is being attacked, such as holding a leg with tweezers.  They hold the other side's gland in reserve and can administer 6 doses before running dry.

With armament like that, you might ask "then what does a true bombardier beetle have up its abdomen?"  The true bombardier beetles are smaller but don't let that fool you.  Their weapons are much more powerful, with separate chambers holding hydroquinones and hydrogen peroxide, suddenly mixed together with oxidative enzymes just as they are fired.  The chemical reaction heats the spray to near boiling temperature and the gas powers the spray.  To quote the Bug Lady, "drop for drop, the chemical is more potent than skunk spray, and a toad that is sprayed in the mouth gags, sticks out its tongue and rubs it against the ground."

"Just chillin' out"

Like many other insects, these beetles don't like having their picture taken.  Many species will fly away just before you finishing focusing on them.  In this case, Galaretia seldom fly but scamper about quickly.  After an hour in the refrigerator slows them down for several minutes there is enough time for taking their portrait.  The insects aren't harmed, escape once they warm up and any goose bumps they have don't show at this magnification.

Toad Song

Amplexis- they "toadly" ignored me as they mated

Two years ago we described toads reproduction in Toads In Love.  I wasn't aware at the time that not every toad on toad encounter is boy-girl. In fact a male toad is likely to mount anything that resembles a toad, including other male toads and even similar sized frogs.  You might think that this would be embarrassing to the "mounter," but there are no studies to confirm this.  It does however generate a release call from the "mountee."

"A release call is produced by a male toad or an unreceptive female toad when a male toad or other animal gets on its back and grabs its sides in the position used for mating or amplexus. It's a toad's way of saying "Get off my back! Let go!" It is also used to call attention to a male's territory, and a male amplexing a female will produce the call when another male tries to interfere with the amplexus."  californiaherps.com

You can hear the subtle release call simply by picking up a toad and gripping it firmly but gently along the sides of its abdomen.  Both sexes will produce this subtle sound, more a gentle warning than a complaint.  Or for the wart free version listen to the release call here.  Caution: toads don't produce warts but they may pee on you.

Much more familiar is the advertisement call.  The advertisement call of the eastern American toad is a long musical trill lasting from 6 to 30 seconds.  It is a common sound around any body of water in the spring, regardless of size, as the male toad tries to attract females for breeding.  It also serves to warn other males that "I am the biggest, baddest guy around so find your own darned pond."  They call mostly in the evening and into the night, but may extend it into daytime when desperate.  Advertisement call heard here.

Toad eggs sticking together

Once mounted (amplexus), the male fertilizes the eggs as the female releases them into the water.  The result it a rather distinctive set of two spiral strings of eggs generally along the waters edge.  Soon the eggs develop into tiny black tadpoles with gold specks, which then lose their tails as legs develop, morphing into toadlets, ready to hit the land.

American toad eggs in pond- note spiraling pair of strands

If you haven't heard this restful sound this year, you need to get outside more often in the evening.  The advertisement call is frequently misidentified as a cricket.  If you want to impress your friends, just keep in mind that crickets call in the fall, so the sound of a "cricket" in spring is likely a toad looking for love.

Herpnet is an excellent resource.
fcps.edu has more pictures and information.
You can hear the pond side calls at this site.
Much more than you ever want to know is at amphibiaweb.org