This study aimed to determine whether bats using frequency modulated (FM) echolocation signals adapt the features of their vocalizations to the perceptual demands of a particular sonar task. Quantitative measures were obtained from the vocal signals produced by echolocating bats (Eptesicus fuscus) that were trained to perform in two distinct perceptual tasks, echo delay and Doppler-shift discriminations. In both perceptual tasks, the bats learned to discriminate electronically manipulated playback signals of their own echolocation sounds, which simulated echoes from sonar targets. Both tasks utilized a single-channel electronic target simulator and tested the bat's in a two-alternative forced choice procedure. The results of this study demonstrate changes in the features of the FM bats' sonar sounds with echolocation task demands, lending support to the notion that this animal actively controls the echo information that guides its behavior.

This article uses a procedure developed by Melichar to classify 124 New England dairy farms according to their financial performance. Logit regression is then used to estimate a model that seeks to explain the variation in observed financial performance. It was found that 80% of the farms in the sample were in good financial position in 1984. The results of the logit regression suggest that production per cow, farm operating expense per cow, milk price, non-milk sources of farm income, farm size, farm location, and land purchases in the last five-year period are statistically significant determinants of financial performance. Surprisingly, operator education is not statistically significant.It is well known that many agricultural producers experienced financial dificulties in the mid-1980s. According to Melichar,] 17% of the nation's farmers were showing signs of financial stress in 1985; and, although this has been a national problem, producers of some commodities have been more vulnerable than others.For instance, Gabriel2 found that, except for poultry production, dairy farmers have experienced more financial difficulty than producers of other agricultural commodities. The size and importance of the nation's dairy industry underscore the seriousness of the financial stress problem in this sector. For example, in The authors gratefully acknowledge helpful comments received from R. Leonard, S. Seaver, E.

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