The Role of Sensory Cues and Feeding Context in the Mediation of Pine-Needle Oil's Repellency in Prairie Voles

Pine-needle oil inhibits feeding in vertebrate species through sensory cues. Prairie voles (Microtus ochrogaster) significantly decreased their ingestion of raw apple pieces when pineneedle oil (10% vol/vol) was applied as a repellent coating. During single-choice tests, voles selected similar amounts of sunflower seeds from pine-needle oil-scented jars and vegetable oiltreated jars. However, when jars containing both stimuli were presented simultaneously, voles retrieved significantly more food from the vegetable oil-treated jars than the pine-needle oil-treated jars. Neonatal administration of capsaicin chronically depletes neurotransmitters in Cand A-a fibers greatly diminishing or abolishing pain transmission in the affected neurons (i.e., trigeminal nerve). Capsaicin-desensitized prairie voles decreased their ingestion of pine-needle oil-treated apples to the same extent as the sham-injected control group of animals, suggesting that pineneedle oil's repellency was not mediated by activation of pain fibers. In settings where alternative foods are available, and where minimal sampling of the product does not represent a hazard, Siberian pine-needle oil may be useful as a rodent repellent.