At this time, "play behaviors" are not documented in any amphibians.
Toys may be used for behavioral enrichment which encourages natural behaviors; however the behavior being encouraged needs to be evaluated for impact on the animal (for example, items that encourage territorial displays, or aggressive attacks should not be used as the stress caused by the items may be sufficient to depress the immune system).
The use of items that encourage normal foraging behaviors is a well documented and accepted as long as the food items are not added in quantities that either harass or predate on the animal (as has been documented with crickets) or pollutes the enviroment, or increases the caloric content of the diet to the point of causing obesity then this can be considered a postive effect (however sometimes satiation occurs and the animal no longer demonstrates any interest in the item).
Ed
(Message edited by Ed on December 18, 2005)