Overlapping Habitat between Presbytis sumatrana and Trachypithecus cristatus in Martabe Gold Mine Area, South Tapanuli

Abstract

Habitat overlap frequently occurs when species share resource preferences. This overlap can lead to interspecific competition, particularly when resources are limited. In this study, we examined the habitat overlap and potential competition between the endangered and endemic Presbytis sumatrana and the vulnerable Trachypithecus cristatus, both of which inhabit the same forest areas adjacent to industrial zones in Batang Toru, South Tapanuli. Data collection was conducted using scan and ad libitum sampling methods. The results indicated that the home ranges of both species overlapped by more than 50%. Both P. sumatrana and T. cristatus predominantly occupied the same canopy height of 6-20 m, classified as stratum A. Although 15 of the 31 food species were utilised by both species, the Pianka index, which measures dietary overlap, did not indicate a significant overlap. P. sumatrana primarily consumed fruits, whereas T. cristatus mostly fed on leaves. While clear evidence of interspecific competition was not observed, langur species frequently used man-made substrates and exhibited a high tolerance for human presence. These results suggest that forest enrichment is critical for future conservation efforts to ensure continued coexistence.

Tumpang-tindih habitat terjadi ketika spesies memiliki kemiripan preferensi sumberdaya sehingga menempati area yang sama. Hal ini dapat berujung pada kompetisi antarspesies, terutama ketika sumberdaya tersebut terbatas. Pada studi ini, tumpang-tindih habitat dan potensi terjadinya kompetisi diukur pada Presbytis sumatrana, salah satu spesies endemik terancam punah, dan Trachypithecus cristatus, spesies terkategori rawan, yang menempati satu hutan yang juga bersisian dengan area industri di Batang Toru, Tapanuli Selatan. Pengambilan data menggunakan metode scan sampling dan ad libitum. Hasil penelitian menunjukkan bahwa lebih dari 50% habitat kedua spesies tumpang-tindih. P. sumatrana dan T. cristatus juga menggunakan ketinggian kanopi pohon 6-20 m, yang terkategori sebagai strata A. Meskipun 15 dari 31 spesies pohon pakan digunakan keduanya, Pianka indeks, yang mengukur tumpang-tindih pakan, tidak menunjukkan nilai signifikan. P. sumatrana paling sering mengonsumsi buah sedangkan T. cristatus paling sering memakan daun. Meskipun kompetisi antarspesies tidak teramati, kedua spesies seringkali menggunakan substrat buatan dan menoleransi kehadiran manusia. Hasil-hasil ini mengindikasikan pentingnya pengayaan hutan untuk konservasi di masa depan demi koeksistensi berkelanjutan mereka.