Peran seruan panjang (long call) orangutan jantan berpipi dalam organisasi sosial orangutan Sumatera (pongo abelii) di stasiun penelitian ketambe, Taman Nasional Gunung Leuser, Aceh Tenggara = The roles of flanged male s long call in the social organization of the sumatran orangutan pongo abelii in ketambe research station gunung leuser national park Southeast Aceh - Tatang Mitra Setia, supervisor (2015)