YOMIURI SHIMBUN (Tokyo, Japan) 06 September 05 Big, scary yamakagashi snake is really a not-so-bigscaredy-cat
The other day, I was out for one of my typical late-afternoon country walks. These sojourns usually take me along narrow farm roads that border rice paddies. This day I had chosen a lonely gravel road near the narrow head of a valley. I was admiring the fat grains of rice, already so heavy they were pulling the stalks over, and for a while I didn't even notice a big snake sunning itself in the grass along the paddy dikes.
When I did notice it, I jumped back two steps and rubbed my eyes. Only the head and 10 or 20 centimeters of the neck were in clear view, but the snake was easily as thick as my forearm! Based on abundant experience with snakes, my mind did an automatic extrapolation of length and thickness, and came up with a critter four or maybe five meters long.
"Run for it!" was what my instincts were telling me, and my body was already starting to turn back the way I came. But in a few nanoseconds my rational mind took over. "There's just no way, Kevin" it reasoned, "that a four-meter snake can be sitting right there on that paddy dike!"
True. The largest snake in the Kanto region, and in all Japan for that matter, is the aodaisho rat snake, and even those never grow longer than three meters. Also, as I calmed down enough for my brain to correctly process the data coming in from my eyes, I could see that this snake was no aodaisho at all. From the beautiful red and black markings on the neck I knew it had to be the yamakagashi, Rhabdophis tigrinus.
I had seen this snake often before. In fact, the yamakagashi feeds heavily on frogs, and I usually keep an eye for them while walking along the paddies. The problem was that this snake was far thicker than any specimen I had ever encountered before.
Now fully recovered, I pulled my digital camera out of its cushioned hip bag. Kneeling, I began snapping pictures as I slowly moved in. As I did this, the snake reared up a little higher, and I could see that the coils below the neck were much thinner. It was then I realized that this yamakagashi was just trying to put one over on me.
The snake had obviously become aware of me long before I came aware of it. Wanting to make a strong initial impression, the yamakagashi had lifted up its head and spread the skin on the back of its neck out in what amounted to a semi-hood. By keeping the spread part pointed at me, the snake was able to make itself appear much thicker than it actually was.
It was an excellent performance, and might have worked had I been a tanuki or a weasel. (It would also have worked perfectly on some people I know!) But we naturalists are a bit tougher to fool. I continued closing in. Suddenly the snake gave up the game, and darted away into the rice paddy. The whole show had been nothing more than a big bluff!
The yamakagashi, sometimes called a Japanese keelback or tiger keelback, is a common resident of the rice paddy countryside. It is truly a beautiful snake, with superb black, red and yellow markings. Usually, an animal that shows these classic warning colors is either dangerous, or mimicking a dangerous species. The yamakagashi may be a good bluffer when it comes to size, but when it comes to being dangerous it has no need to mimic. In fact, this species is armed with one of the most deadly poisons imaginable.
Still, the yamakagashi is basically a scaredy-cat. When bluffing doesn't work it quickly retires, always anxious to avoid a confrontation. The main reason for this is that although this snake has some potent poison, it lacks an efficient delivery system. The poison glands are located way in the back of the mouth, and the delivery fangs are relatively short. Thus the yamakagashi has to bite deep and hold on while the poison slowly works its way in through the wounds. This means that although it may win in the end, it will certainly get seriously banged up in a fight with any good-sized critter.
Although I have never seen it in actual use myself, the yamakagashi also has another backup defense system. In addition to the poison that releases into the mouth, this species has separate poison glands located on the back of the neck near the head. This is a snake's most vulnerable spot, and snake predators such as weasels, tanuki, cats and dogs instinctively try to sink their fangs in right here. When this happens, the yamakagashi squirts the poison right into the predator's mouth!
Even without the faking, the yamakagashi I met that day was big and beautiful. I was so impressed I somehow let it get away without catching and measuring it, but I'm sure it was close to a meter and half long, which is near the maximum size for this species.
It did my heart good to meet such a large, mature specimen of this spectacular species. A snake this big means that the surrounding paddies must support a large population of frogs. This in turn tells me that the water quality must be good, and that the rice is being farmed organically or at least with reduced levels of insecticides. In other words, the snake told me that the local habitat is in excellent ecological condition.
Instead of scaring me off, he had invited me back!
Big, scary yamakagashi snake is really a not-so-bigscaredy-cat