Wire fences run all the way round the island above the high-water line, and trenches have been dug there too. According to Cheng Yi-chun's interviews with garrison members, when turtles crawl further from the shore and approach these defenses they are sometimes caught under the wire so that they can move neither forward nor back, or they may fall into the trenches.
據受訪的駐軍表示，由於全島周圍在高潮線都已架設貼地的鐵絲網和挖了壕溝，綠蠵龜若爬得離岸較遠，深入這些工事附近，會被鐵絲網卡住進退不得，或跌入壕溝。