Board Thread:Naruto Discussions/@comment-24847491-20140921145042/@comment-4728499-20140922123838

Jiraiya still had the ability to enter Sage Mode on his own, the toads were gathering and transfering Natural energy to him since he couldn't stay still during his fight with the 6 paths. Kabuto used Sage Transformation to gather Natural energy to let him stay in Sage Mode indefinitely.