Effect of diphacinone on blood coagulation in Spermophilus beecheyi as a basis for determining optimal timing of field bait applications

The effect was determined of a single dose of 2 mg kg-1 diphacinone on three blood-clotting parameters Prothrombin Time (PT), Partial Thromboplastin Time (PTT), and Protein Induced by Vitamin K Absence or Antagonists (PIVKA)] over a 120-h period in California ground squirrels, Spermophilus beecheyi. Diphacinone resulted in elevated PT, PTT and PIVKA within 24 h of squirrels receiving the dose. The most significant change was observed 72 h after dosing. As time following diphacinone dosing increased, there was higher individual variation in blood-clotting time. We suggest that increasing the interval between field bait applications should still result in squirrel mortality but reduce the potential for secondary hazards that may occur when squirrels have the opportunity to consume more than one lethal dose of diphacinone.