Effect of aging on spatial learning and running speed in the shrew (Cryptotis parva)

Abstract

This study examined spatial-learning ability of the least shrew, Cryptotis parva, in a complex maze and the effects of senescence on spatial learning and maximal running speeds. This represents the 1st such study on these parameters for soricids. Shrews from 3 age groups, juvenile (20-23 days old), young but sexually mature (50-54 days), and senescent (20 months), were tested in a maze containing 5 blind alleys. The number of blind-alley errors was recorded during a 10-day training period. On the 1st day of training, there was a significant difference in performance between senescent (123.4 errors ± 14.1 SE) and young (68.9 ± 5.8 errors) shrews and between senescent and juvenile shrews (74.3 ± 7.2 errors). During the 10-day period, there was a significant decrease in mean number of errors: from 74.3 to 3.3 for juvenile shrews, 68.9 to 2.4 for young shrews, and 123.4 to 16.6 for senescent shrews. There was no significant difference in decrease in errors between juvenile and young shrews. Young shrews had significantly higher maximal running speeds (15. 3 km/h ± 3.2 SE) in a racetrack as compared with senescent shrews (8.8 ± 2.7 km/h). These results demonstrate for the 1st time that aging impairs running speed and spatial-learning ability in C. parva and that these 2 parameters may be related.