Rana sylvatica tadpoles have been shown to alter their oral structures in response to increased competition. The placement of mirrors on tank walls has previously been used to simulate increased density and to induce phenotypic changes in tadpole size and timing of metamorphosis. Here, we examine the effects of simulated overcrowding, induced with mirrors, on the oral structures of R. sylvatica tadpoles. Our data suggest that, although phenotypic changes caused by visually simulated competition are not as drastic as those produced by actual competition, they do occur. These alterations manifest in a failure to develop specific tooth rows.