The striped-squirrel is a major mammal nectar-robber of the self-compatible shrub species, Alpinia roxburghii (Zingiberaceae). Previous study has found a significant decrease in the fruit-set of flowers in a congeneric ginger species, A. kwangsiensis robbed by the squirrel Tamiops swinhoei. The study showed that the nectar-robbing behavior of squirrels has decreased female reproductive success through direct floral damage. However, the net impact of squirrel nectar robbing on plant fitness has rarely been studied.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study in a monsoon evergreen broad-leaved forest in Caiyanghe Nature Reserve (22°30' N, 101°2' E; 1200 m asl), Yunnan Province, southwest China. They aimed to test the effect of squirrel nectar-robbing on A. roxburghii reproductive fitness, by using a fluorescent dye as a pollen analogue, and measuring fruit and seed output. They tried to seek how pollen transfer distance differed, and how fruit and seed production changed between robbed and unrobed plots. They further asked whether striped-squirrel robbing behavior significantly affected floral reproductive parts. They also studied how squirrel robbing behavior impacted plant fitness.
The researchers found that nectar-robbing by squirrels had both direct and indirect effects on male (pollen-flow distance) and female (fruit set) flowers thus influencing plant reproductive success. Pollinator visitation rate differed between robbed and unrobbed plots.They recorded the visitation frequence of two bee species (Bombus eximius and Apis cerana), the primary pollinators, for six consecutive days and found that the visitation frequency of Bombus eximius  was higher than that of A. cerana for both robbed and unrobbed plots. Pollen dispersal distance was lower in robbed than in unrobbed plots, indicating that nectar theft influences pollen flow activity. Similarly, fruit set significantly decreased in robbed plots whereas seed set was not significantly affected.
  Although squirrel-nectar robbing behavior directly damaged the floral parts of plants, that did not affect seed set and female reproductive fitness of intact flowers. The results revealed that striped squirrel nectar robbing behavior significantly impacted the male fitness of A. roxburghii flowers by negatively affecting pollen-flow distance.
The study entitled “Impact of Striped-Squirrel Nectar-Robbing Behaviour on Gender Fitness inAlpinia roxburghiiSweet (Zingiberaceae)” has been published in PLoS ONE.