vṛṣāyamāṇau - becoming like bulls; nardantau - making roaring sounds; yuyudhāte - both used to fight; parasparam - each other; anukṛtya - imitating; rutaiḥ - with cries; jantūn - the animals; ceratuḥ - used to play; prākṛtau - ordinary boys; yathā - just like.

“Acting just like ordinary boys, They played like roaring bulls as They fought each other, and They imitated the calls of various animals.”