Tuesday, May 26, 2015

A Few Words in Defense of Spiders

     I know, I know – you hate spiders. Spiders are the creepiest of all terrestrial life, you say. Spiders like to sneak into houses and bite unsuspecting children, you say. Spiders are as evil as snakes and - as everyone knows - snakes are pretty evil, you say. But allow me to posit this idea to you: You are wrong and unnecessarily burdened by cultural prejudices. In a country that takes great pride in its ideals of independent “free” thought, I see a lot of people who are slaves to unfortunate misconceptions.
     Let’s first consider an obvious undeniable fact. The existence of spiders is as valid as the existence of all other life forms, including human life. Does that seem like a rather cold view of the world? Not at all; I’m just not human-centric in my judgement of nature. All life on earth has evolved over the eons to arrive at this moment in time precisely as we see it (or, one could make the argument, as imprecisely as we see it). Tapeworms, wolves, nematodes, whales, humans, and spiders all have equal claim for their place on Earth.  
     Let’s also admit that we are apparently biased against spiders because most of them aren’t as pretty as, say, butterflies. If spiders had beautiful wings, would we be less inclined to squish them with a shoe? Most spiders are cryptic in coloration because they depend on stealth to capture prey. So, let’s agree not to judge them too harshly on aesthetics. Beauty, after all, is only skin deep.
     Besides the facts that spiders are a part of our evolutionary heritage and that we humans are easily manipulated by cultural prejudices, you might reasonably ask, “What’s so interesting about spiders?” My answer is, “Everything.”
There are almost 40,000 known species of spiders in the world. They vary in size from almost microscopic (Patu digua) to as big as a dinner plate (Theraphosa blondi – the goliath bird-eating spider). Most spiders are small with a body length not exceeding half an inch.
     Yes, it’s true that spiders aren’t vegetarians. They are evolutionarily obliged to kill things for their meals just like lions, lizards, and anteaters. Spiders don’t have a choice to eat vegetarian food like humans do. Almost all spiders are venomous (excepting feather-legged orb weavers) but very few have a bite that can harm humans. The venom is needed to quickly subdue prey. Keep in mind that most female wasps and bees are venomous too, thus the pain of the sting.
As pointed out above, spiders aren’t usually noted for their beauty, but there are certainly those that are arrayed in brilliant colors. Some tarantula species (Mygalomorphs) and many jumping spiders (Salticids) are flamboyantly decorated. (For jumping spiders, the colors serve a purpose in their mating rituals, but it is unclear what evolutionary advantage tarantulas get from being brightly decorated.) There are a few spiders – such as crab spiders – that can adjust their color from white to yellow to match the flower they’re on.

     Even though some spiders have exceptionally good eyesight (wolf spiders and jumping spiders), most have poor eyesight and depend primarily on “touch” for survival (another reason why color isn’t important to the majority of spiders). The hairs on their legs serve the same purpose as whiskers on cats – to feel the world around them. The webs built by many spiders also serve as an extended network of nerves that signal when prey has been snagged. 
      And those webs! Spiders spin silken threads from glands on the posterior end of their abdomens. This silk, in comparable thickness, is stronger than steel. Spiders use the silk for capturing prey, encasing their eggs, for temporarily tying down their mates, and for building a safe hideaway. Webs take on different shapes depending on which species makes them. For instance, if you see an orb web, you can be assured that a black widow - a cobweb weaver - didn’t create it.  The bolas spider (Mastophora spp.) captures moths by lassoing them with a strand of sticky thread. Diving bell spiders (Argyroneta aquatica) actually live under water in an air bubble held in place by silk. And let’s not forget the silk used for flying! Newly hatched spiderlings often fly to distant places by climbing to the tip of a leaf and releasing a long thread that allows wind to carry them aloft like a kite; it’s called “ballooning”. 
      Finally, here in Arizona we have many distinctive spiders. There are a few species of Loxosceles spiders that many people erroneously call “brown recluses”. (A brown recluse is Loxosceles reclusa and lives in Texas, east to Georgia, and up into Virginia. They do not naturally occur in Arizona.) Our Loxosceles species are supposedly less virulently toxic in their bites. We also have black widows (Latrodectus spp.) which have bites of “medical significance”, but usually stay in their webs unless molested by humans. Normally black widows are very shy spiders and will fall to the ground and play dead if humans try to capture them. One of the most interesting of the local spiders is the spitting spider (Scytodes sp.), a very small and slow-moving creature that captures prey by spitting a sticky venom. And, of course, we have desert tarantulas, the largest spiders in the United States. 
     Spiders are important for the fact that they eat mostly insects and other spiders (black widows, by the way, frequently eat scorpions!), thus keeping down populations of potentially harmful pests like mosquitos and flies. If a spider should be wandering around in your house, it is simply because it’s looking for prey. It is never in your house to attack you. Keep your house a little cleaner and clutter off the floor and you will see far fewer spiders.
     We as humans have a limited natural ability to study nature. Our unaided eyes can only see a small portion of the stars (and none of the billions of galaxies) in the Universe. Nor can our unaided eyes see the microverse of bacteria and viruses, etc. However, we do have the ability to take the time to pay attention to the smaller creatures around us and, in the process, learn something about ourselves and our place in Nature. Spiders are often maligned and needlessly killed due only to ignorance-driven fear. Much of that fear is culturally-based - a learned reaction rather than a natural response. Here we have an opportunity to reconsider these small animals and to marvel over the fascinating lives they live. More knowledge is always a good thing. 

-T. Stone
(If you are interested in this topic at all, come out to the BTA on Saturday, May 30th, to see a slide show presentation by T. Stone on the subject of spiders. Live specimens will also be presented and we’ll walk around a portion of the BTA to look at webs. Starts at 10 a.m.)

Sunday, May 17, 2015

The Cow Jumped Over the Moon

Yesterday, I came upon a small herd of range cows, maybe a dozen, who eyed me pensively as I jogged past. Some just looked at me, blankly, with that know-nothing sort of look that really doesn’t reveal what they’re thinking; I just know that they didn’t feel threatened enough to run. Others gave me a similar look but quickly turned tail, inciting a few of their nearby bovine compatriots to follow suit. It was two of these cows, trotting away from me with four stiff but rapidly moving legs, that did something I have never seen before.

I’m not a big fan of cows, particularly when I seem them in the mountains munching on what’s left of a grass depleted range, nor do I enjoy dodging the crusty piles of excrement that they leave behind. I don't eat their flesh, but I do wear the shoes made from their hides, so I have a grudging appreciation for their existence. This group of cows was on a private ranch, or, rather, they were supposed to be.

A typical cattle guard with a bypass gate--but is it jumpable?
When these two aforementioned cows ran from me, they headed down the same dirt road that I was using and never looked back. I rarely see them on this section of the road because a nearby cattle guard is supposed to impose a non-negotiable barrier. I have to cross the same cattle guard myself when I run this old road, and when I do, I always stop and walk across it, placing each of my feet across two rails at a time. After three or four careful steps, I’m safely on the other side.

For humans, this is a sure-footed way to cross a cattle guard, two rails at a time.

Those steps that I execute so easily are not supposed to be possible for cows. They have hooves, not $150 running shoes, and their bone hard feet don’t adapt well to the slick surface of the steel railroad rails that cattle guards are often made from.

The classic homemade design requires someone with welding skills and a dozen recycled steel rails. A frame of concrete is poured, then the freshly welded rack of rails is lowered in place by some sort of backhoe or tractor. Ideally, it should be installed so that the approach and exit from either end is no worse than a well- designed railroad crossing.

The rails are thin and the gaps are wide, so this combination is supposed to keep the cows in bounds, acting like a horizontal barbed wire fence, one that is easily driven over by a vehicle.  On the sides, a standard vertical fence of barbed wire usually extends off in both directions so that the cows cannot do an end run around the guard. Sometimes, there is a gate on one side that allows the rancher to allow the cattle through, should there be a legitimate reason to do so.

A neutral expression often belies the athletic intent of a heifer.
On this day, the cows that were running ahead of me were hemmed in by a vertical bank on one side of the road and a steep, brushy slope that led down to the creek on the other. Their flight (rather than fight) response was irrevocably engaged, so they trotted straight down the middle of the road, gaining momentum as they did.  It wasn’t stamped speed; there was no panic or desperation involved, just a shared commitment towards a common goal that could only mean one thing: they were going to cross that cattle guard.

As far as cars and trucks go, each cattle guard is unique, and locals usually know which ones they have to slow down for and which ones they can cross without hitting the brakes. Just east of the Arboretum, within fifty feet of Highway 60, there is a notorious cattle guard on the dirt road that leads to the historic wagon tracks. The smooth and level approach to the front of it belies the excitement that waits on the other side. The crossing is uneventful until the unsuspecting driver feels his car suddenly pitch downward when it drops off the far side. As the front tires hit the road below, so does the undercarriage make violent contact with the unforgiving rails of the cattle guard. With it comes the industrial scrap yard sound of crushing mufflers, perforating gas tanks, and twisting bumpers, sounds that only a tow truck driver can love. Word spreads quickly about such pitfalls; that’s why site seers with low clearance sedans are often seen parked on the highway side of that cattle guard.

As a bicycle rider, I have crossed far more cattle guards on two wheels than I have on two feet. There is virtually no way to "fall through the cracks" on a bicycle, yet, in the past few years, signs have appeared on cattle guards, particularly on back roads, that say, “BICYCLES CROSS WITH CAUTION.” It doesn’t make sense because a rider would have to intentionally turn his front wheel at a ninety degree angle to become entangled in one of these, and that would throw him off his bike in the best of circumstances.Where is the precedent here? I'd love to see that wreck.

But back to the cows. They were hell bent to get away from me, and though I half expected them to stop within inches of the cattle guard and decide what to do next, I knew that they wouldn’t.

Each of them, one after the other, without breaking the cadence of their trot, jumped over the cattle guard. Yes, with the same ease that you or I would jump over a rain filled puddle. They didn’t slow down, just made a graceful, low arc, easily clearing the last rail of the cattle guard with inches to spare. It was effortless but practiced, like a ballet leap, and, after landing, they trotted nonchalantly  into the pasture. It was obvious that they had mastered this technique, proven when I saw two more of them munching grass along the railroad tracks, a full half mile down the road on the wrong side of the cattle guard. I had no doubt that they had been here before.

Who, me?
According to Mother Goose, a cow has been known to jump over the moon, so it should come to no surprise that I watched two of them cross a diminutive cattle guard. To witness their next trick, I will no longer be watching a heifer munch grasses off in the mesquite brush, or watch a pair of brown and white cows slowly walk down the road together, their heads hung low with slow lethargic steps. No, when I see cows along one of my running routes, I won’t be checking out the cattle guards, I’ll be looking skyward. 

 Kim Stone