SB 10.43.34

nityaṁ pramuditā gopā
 vatsa-pālā yathā-sphuṭam
vaneṣu malla-yuddhena
 krīḍantaś cārayanti gāḥ
Word for word: 
nityam — always; pramuditāḥ — very happy; gopāḥ — cowherds; vatsapālāḥ — tending the calves; yathā-sphuṭam — obviously; vaneṣu — in the various forests; malla-yuddhena — with wrestling; krīḍantaḥ — playing; cārayanti — they graze; gāḥ — the cows.
Translation: 
It is well known that cowherd boys are always joyful as they tend their calves, and that the boys playfully wrestle with each other while grazing their animals in the various forests.
Purport: 

Here Cāṇūra explains how the two brothers came to be expert at wrestling.