YAPHANK - A Suffolk County sheriff's deputy today came across a 3-foot alligator abandoned on the side of the Long Island Expressway. The unexpected discovery was made by Sgt. John Rung a mile and half past exit 68 on the eastbound side of the roadway. He says when he tapped the amphibian with his baton, the gator whipped around and bared its teeth. "I jumped back and I was surprised that it was still alive and that it was very aggressive," Rung says. Suffolk SPCA Chief Roy Gross says the animal could have posed a threat to small children or house pets if it managed to make it into a residential area.Gross suspects someone picked up the gator as a pet and then dumped it by the side of the road when it got too big. He says gators of this kind can be purchased legally in Pennsylvania, or illegally on the black market. According to Gross, the gator will be sent to an animal sanctuary in the South. Meanwhile, the Suffolk SPCA is offering a $1,000 reward for information leading to the arrest of the person who abandoned the alligator.