Pulau Jawa merupakan habitat bagi 6 spesies primata. Lutung budeng (Trachypithecus auratus) merupakan salah satu primata endemik pulau Jawa yang memiliki ukuran tubuh sekitar 517 mm dengan panjang ekor rata-rata 742 mm. Persebaran lutung budeng di Jawa Barat tercatat di 12 lokasi, termasuk Taman Nasional Gunung Ciremai dan Taman Nasional Gunung Gede Pangrango. Namun, studi mengenai populasi lutung budeng di kedua taman nasional tersebut masih kurang. Berdasarkan hal tersebut, maka dirumuskan penelitian ini dengan tujuan untuk mengetahui ukuran populasi, kepadatan populasi, dan laju perjumpaan lutung budeng di kedua kawasan taman nasional tersebut. Ukuran populasi lutung budeng yang teramati tidak memiliki perbedaan jumlah individu di dalam kelompoknya. Kepadatan populasi lutung budeng tertinggi berada di Gunung Putri, sedangkan yang terendah di Cilengkrang. Laju perjumpaan lutung budeng tertinggi terdapat di Palasari dan terendah di Cilengkrang. Kehadiran lutung budeng dipengaruhi oleh tingginya persentase tutupan kanopi dan tingkat aktivitas manusia di jalur pengamatan. Selain itu, faktor cuaca, jarak pandang pengamat, dan kemampuan pengamat dalam mendeteksi keberadaan lutung budeng juga memengaruhi data yang dihasilkan.

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Java Island is a habitat for 6 primate species. Ebony leaf monkey (Trachypithecus auratus) is one of the endemic primates in Java, which has a body size of about 517 mm with an average tail length of 742 mm. Distribution of ebony leaf monkey in West Java is recorded in 12 locations, including Mount Ciremai National Park and Mount Gede Pangrango National Park. However, there is a lack of studies of ebony leaf monkey population in those two national parks. Based on this, this study was formulated with the aim of knowing the population size, population density, and the encounter rates of ebony leaf monkey in those two national park areas. The observed population size of ebony leaf monkey did not differ in the number of individuals in the group. The highest population density of ebony leaf monkey is in the Gunung Putri, while the lowest is in the Cilengkrang. The highest rate of encounter with the lutung budeng was on the Palasari and the lowest was on the Cilengkrang. The presence of the ebony leaf monkey is influenced by the high percentage of canopy cover and the level of human activity in the observation path. In addition, weather factors, observer visibility, and observer ability to detect the presence of ebony leaf monkey also affect the resulting data.