Chuang Ling-mu, a research assistant at the Hengchun research station of the Taiwan Forestry Research Institute (TFRI), says the warm winter caused trees to flower and fruit early, and the plentiful rainfall in May and June boosted plant growth. He speculates that these may have been "contributory factors" in the explosion in caterpillar populations.
林試所恆春分所助理莊鈴木也推測，暖冬讓綠樹提早開花結果，加上五、六月南部雨量充足，植物搶著長，可能是毛毛蟲數量爆發的「輔助因子」。