By Jud Pyle, CFA, chief investment strategist for the Options News NetworkShares of heavy-equipment maker Caterpillar ( CAT) are currently trading around $31.20, up about 2% in today's trading. This rally comes after CAT announced earnings this morning before the market opened. CAT announced per-share results of 39 cents, easily trumping analysts' consensus expectations of four cents per share. Clearly, that headline number seems very bullish for the shares. But comments from CAT that earnings for the rest of the year would be closer to $1.25 than the $1.77 analysts expect has dampened investor enthusiasm today. We also saw some put activity hit the tape, which could suggest investors are seeking some protection in case of a potential pullback in CAT shares. Looking at the CAT August 20 puts -- out-of-the-money by more than 35% -- we see that more than 40,000 have traded today, after an earnings release! The puts are currently trading for around $1, with the stock near $31.20. Current open interest in the puts prior to today's trading action was just 2,184, according to the Sidewinder report at www.onn.tv. So it's apparent that today's volume will translate into new open interest come tomorrow. The August 17.5 puts are also seeing large volume, with more than 20,000 contracts hitting the tape at a price around 65 cents. Open interest at that strike, however, is much higher, at 10,935. What is interesting about this activity is that the bulk of the put volume has been dominated by buyers, which has served to push up the implied volatility of the puts. In other words, the bears are out in full force even though earnings have already hit the wires.