In the experimental analysis of behavior, response allocation is typically studied under concurrent interval schedules, with two response alternatives, in a static environment. The natural environment of the unfettered organism, however, is dynamic insofar as even frequently visited environments are rarely identical from encounter to encounter. Additionally, natural environments usually offer more than two concurrently available behaviors that are often scheduled for reinforcement contingent on rate of responding. The purpose of this study was to determine how the addition or removal of a third response alternative affected response allocation between two topographically dissimilar operants on independent concurrent ratio schedules in a dynamic environment. Results indicate that the addition of the third operant served to temporarily suppress response rates of the first two operants but had no or only minor and inconsistent effects on relative allocation. The reintroduction of the third operant in a new location again suppressed response rates in three of four subjects and slightly shifted response allocation for one subject. Highly individual anecdotal patterns could be seen in tangential observations of each of 4 subjects. The results suggest the possibility that new alternatives have temporary effects on response bias, and that these effects may be variable and dependent on details of individual history and stimulus control.