AbstractA viscous ocular secretion streams from the eyes of bottlenose dolphins,Tursiops truncatuss, removed from the water. The chemical composition and environmentally adaptive implications of this substance continue to perplex curators and scientists. Secretions from three dolphins were examined for deviations from literature values for normal human and terrestrial mammalian tear film components. Osmolality (x̄= 470 mOsm/kg), pH (x̄= 8.44) and glucose (x̄= 26.58 mg/100 ml) were significantly greater than human and terrestrial mammalian tear film values; while lysozyme (x̄= 0.005 mg/ml) and total cholesterol (x̄= 0.17 μg/μ1) were significantly less. Refractive index, sodium ion concentration, and potassium tear to plasma ratios in the dolphin ocular secretion did not deviate significantly from human or terrestrial mammalian tears. Electrophoresis of dolphin tears yielded four major protein bands (probably lactoferrin, serum albumin, teat specific prealbumin, and lysozyme) and high molecular weight glycoproteins similar to human tears. The chemical composition of theT. truncatusocular secretion suggests that the circumorbital conjunctival gland may be analogous (relative to refractive index, electrolytes, and component protein) to the terrestrial lachrymal gland. At the functional level theT. truncatusocular secretion may reduce hydrodynamic resistance on the cornea and protect it from bacterial in