Ant Talk

Apr 19 2011 Published by under Biology & Environment

Ant on a mustard flowerWhen a wood thrush flew by the Trailhead mound carrying a grasshopper to her own nest and dropped part of the crushed insect to the ground, a patrolling worker found it in less than a minute and triggered a chain action. The worker examined the grasshopper, tasted it briefly, then ran back to the nest entrance. On the way, she touched the tip of her abdomen repeatedly to the ground, laying down a thin trail of chemicals. Entering the nest, she rushed up to each nest mate she passed, brushing her face close to theirs. With their antennae, her nest mates detected both the trail substance and the smell of grasshopper. The signals now proclaimed, Food. I have found food. Follow my trail! Soon a mob of ants ran out, followed the trail, and gathered around the delicious grasshopper haunch.
~ From E.O. Wilson's "Trailhead"

When I think of ants it's with a mixture of fascination and loathing.

Loathing because of the seemingly constant battle required to keep them from taking up residence in my kitchen. It's not just the unpleasantness of having to remove all the contents of my cabinets to figure out how the ants are getting in.  It's the lingering sensation after handling ant-covered bowls and plates or wiping down ant-strewn counters that the little buggers are still crawling on me.  Intellectually I know it's unlikely they can cause any real harm, but just thinking about it gives me the creepy-crawlies.

But out in the wild - or at least my back yard - ants are really interesting to watch, especially when scouts lead their colony-mates to a food source or mobilize when their colony is in danger. Clearly while not particularly clever as individuals, communication between colony members allows them to function effectively as a group.

Evolutionary biologist E.O. Wilson is one of the world's leading experts on ants. Here he explains at World Science Festival how ants use chemical signals communicate:

The quote at the beginning of this post is from E.O. Wilson's history of an ant colony - "Trailhead" - published in the New Yorker. Wilson's anthropomorphic descriptions of ant communication work pretty well as fiction, but he may be oversimplifying what happens in an ant colony.

For more detailed look on the complexities of how an ant colony functions check out Stanford biologist Deborah Gordon's TED talk about her research on harvester ant colonies in the Arizona desert:


(note: you can view the video with captions on the TED talk page)

The "haphazard" interactions she's observed sound a lot messier as a form of communication than the chemical "statements" described by Wilson.

Why does that matter? Figuring out the details of how ants are directed to perform specific tasks could be used to develop ways of naturally controlling invasive ant populations or preventing home invasions with some sort of "Danger, keep out!" signal. That's a result I'd like to see.

Top Image: ant on a mustard flower by me

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The Christmas Bird Count

Dec 07 2010 Published by under Biology & Environment

For over a century the Audubon Society has organized a massive citizen science undertaking: The Christmas Bird Count. Tens of thousands of volunteers help take a census of the bird populations of Canada, the United States, Mexico and Central and South America.

Data from the annual surveys has provided biologists and conservationists a picture of long term changes in the distribution of North American bird populations.

For example, analysis of data collected over the past 40 years shows that the the winter range of many bird populations - 177 of the 305 species examined -  has shifted north, in some cases hundreds of miles. The shift correlates with an increase in mean January temperatures of almost 5 degrees during that period, and it's likely that climate change is at least partially responsible. Based on that data, the Audubon Society's report on birds and climate change (pdf) concludes that "ecological disruptions that threaten birds, other wildlife and human communities [due to climate change] are likely already in motion".

The Christmas Bird Count has also helped identify common bird species - from  meadowlarks to hummingbirds -  that "have taken a nosedive" over the past 40 years.

On the other hand, doves and pigeons have expanded their ranges along with growing urban and suburban development.

It's data that would be difficult to collect without an army of volunteers.

If you'd like to participate, this year's Christmas Bird Count begins on December 14th and runs through January 5th.  You'll need to register for a count:

There is a specific methodology to the CBC, but everyone can participate. The count takes place within "Count Circles," which focus on specific geographical areas. Each circle is led by a Count Compiler. Therefore, if you are a beginning birder, you will be able to join a group that includes at least one experienced birdwatcher. In addition, if your home is within the boundaries of a Count Circle, then you can stay home and report the birds that visit your feeder once you have arranged to do so with the Count Compiler. There is a $5 fee to participate in the CBC for all field participants aged 19 or older.

Find a count circle near you (unfortunately only searchable by state or province).

Even if you can't participate in the Christmas Count, you might be interested in similar bird observation projects:

Images from  from Our Winter Birds: How to Know and How to Attract Them by Frank M. Chapman (1918).  Chapman, an ornithologist with the American museum of Natural History and officer in the Audubon Society, proposed the first Christmas Bird Count in 1900. Top image: Tree Sparrow. Bottom Image: Northern Shrike.

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Good news, everyone! Brown widow spiders have arrived

Oct 06 2010 Published by under Biology & Environment

Black widow hanging out on my planter

I don't like spiders. I know, deep down, that they are unlikely to hurt me, and that they eat flies and other pesty insects.  Even so, I have a visceral reaction when a  spider crawls into my vicinity. I'm pretty much OK with spiders that stay outside (although stumbling on a big one, like the one Zuska found on her rain barrel might cause me pause1).

But black widow spiders (Latrodectus hesperus) are another  story. They are indeed venomous and their bite is supposed to be quite painful. Just reading about the symptoms makes me cringe:

Severe muscle pain and cramps may develop in the first two hours. Severe cramps are usually first felt in the back, shoulders, abdomen and thighs. Other symptoms include weakness, sweating, headache, anxiety, itching, nausea, vomiting, difficult breathing and increased blood pressure.

But no one in the U.S. has died from a black widow bite in over a decade, so it's not that bad, right?

Fortunately, black widows rarely end up inside the house. Instead they make their webs in dark nooks and crannies, usually only coming out after dark or if they are disturbed.  Their amorphous webs - straight from a haunted house - are pretty easy to spot and sweep away.  They leave me alone and I pretty much leave them alone.

Brown is apparently the "New Black"

But then one of the local newspapers had to run an article ensured to freak me out a bit: "Brown Widows Now in Inland Area"

Brown widows (Latrodectus geometricus) are cousins to the  black widow. They are more drably colored than the black widow, with brown bodies and an orange or yellow hourglass on the abdomen.  Brown widows are originally from  South Africa, and have been working their way west from Florida for the past 10 years or so. Only recently have they appeared in Inland Southern California.

How do brown widow spiders compare to black widows? According to the article:

  • Brown widows are more abundant than black widows. According to Rick Vetter, who studies spiders at UC Riverside, "Where you might find six or seven black widows in a backyard, now you find 100 brown widows."
  • Brown widow venom is twice as toxic as black widow venom.
  • Brown widows live in more open locations - such as under patio chairs and in chain link fences - than black widows

They sound pretty nasty, right?  I'll admit I went out to my patio and made sure there weren't any webs on my plastic patio chairs shortly after reading the article.

But the real story - easy to overlook among all the scary-sounding description2 - is that brown widows are much less likely to bite than black widows, and when they do, they don't inject as much venom. That means that they aren't actually considered to be dangerous.

As the UCR Spider Research site explains:

A South African medical journal reports on the bites of 15 brown widows in humans (Muller 1993) . Only two symptoms of brown widow envenomation were reported in the majority of bite victims: 1) pain while being bitten and 2) a mark where the bite occurred. That's it. Not much more. The bite of the brown widow is about the same as any non-poisonous spider. It hurts and leaves a little mark on the skin. It is no big deal. There are none of the serious, protracted symptoms that one would exhibit when bitten by a black widow.

So the appearance of the brown widow really is good news, at least from the public safety perspective, because they may be displacing the black widow, which is dangerous.

I'll still be happier if I never run in to one.

If you want to help track the spread of the brown widow spider in California, you can mail any brown widows you find outside of San Diego, Orange, or Los Angeles County to Rick Vetter at UC Riverside.

If you are in Los Angeles County, you can also participate in the Los Angeles Spider Survey, sponsored by the Natural History Museum of Los Angeles.

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1. Where "pause" means that I get my husband to move it away from any outdoor equipment I want to use.

2. Especially when the article concludes with advice from an entomologist with the National Pest Management Association who advises (not surprisingly) dusting with pesticides or calling an exterminator. "Kill them all" seems a bit over-the-top advice for non-dangerous spiders.

Top image: By me.

Bottom image: thumbnail of graphic from the Press-Enterprise article "Brown Widows Now in Inland Area". Click the thumbnail to see the full-sized image.

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Backyard Fauna: Western Fence Lizard

Aug 13 2010 Published by under Biology & Environment

Western Fence Lizard

Living in the 'burbs there aren't many native animals that appear in my back yard other than birds and bugs.

The exception is the Western Fence Lizard - Sceloporus occidentalis - which pretty much have the run of the place.

The lizards spend most of their time sunning themselves on walls or fences. However, occasionally they do pushups, which serves as a message to others of their kind, either as territorial challenge or part of a courtship display (I can't tell the difference, but presumably the other lizards can). You can see that behavior in this video:

Western Fence Lizards sunning themselves.

They  reduce the population of unpleasant backyard critters by eating on crickets, spiders, ticks and scorpions. They even reduce the risk of Lyme disease, because the lizards' blood carries a factor that kills the disease-causing bacteria in the gut of ticks that bite them.

I just wish our next door neighbor's cat would stop hunting them, at least on our side of the fence.

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