Date of this Version
General Motors and the A C. Rochester Company, a subsidiary of General Motors (GM), has found that the robber diaphragms on automatic speed control mechanisms (servos) were gnawed by unknown rodents. House mice (Mus musculus), Peromyscus spp., and eastern chipmunks (Tamias striatus) were used to test gnawing behavior on 4 kinds of diaphragms. Diaphragms with or without a rodent proof cure formula, which are used by GM, did not influence the gnawing of all test rodent species. Diaphragms with a lubricant (Paricin) were more attractive to gnawing by house mice than diaphragms without a lubricant. Five objects with different texture were used to detect gnawing preference of house mice and 3 objects were used on Peromyscus. The textures of diaphragms and nylon discs were not significantly preferred by house mice compared to the textures of corks and wood blocks. Rubber stoppers were gnawed less than wood blocks and corks by house mice and Peromyscus, but the differences were not significant. Results indicate that the presence of a rigid and protective edge on the diaphragms was a critical factor in attracting rodent gnawing. To test this possibility, diaphragms on servos supported by aluminum piston heads with 3 different beveled edges were presented to captive Peromyscus. The amount of gnawing was not significantly different among the diaphragms supported by the different piston heads. Once the gnawing was initiated, continued gnawing was thought to be dependent on the texture of objects.