Mt Cetaceo is one of the highest peaks in the northern Sierra Madre mountains in north-east Luzon. The IBA extends from near the Twin Peaks area southwards through eastern Cagayan Province to the border with Isabela Province. A large block of forest is shown there on recent forest cover maps. The IBA includes some areas of lowland forest below about 1,000 m, but these have been reported to be degraded. However, the extensive montane and mossy forests have been very little affected by human activities, and only a few hunting trails give evidence of the activities of the local Aetas people in the area. A survey in 1992 found that lower montane forest covered a steep ridge at 1,200-1,400 m below an extensively forested plateau. There were fair amounts of epiphytes, mainly orchids and ferns, and the undergrowth was dominated in several places by dense patches of ferns. Mossy forest was found above about 1,400 m, and was characterized by a low and entangled forest with a canopy height decreasing with elevation from 10 m to 3-4 m in the highest and more exposed areas. The trees were densely covered by mosses and contained an abundance of epiphytes such as orchids, pitcherplants Nepenthes sp. and ferns.
Many of the threatened and restricted-range birds of the Luzon Endemic Bird Area were recorded on Mt Cetaceo during surveys in 1992. These included most of the montane forest species characteristic of the EBA, including the threatened Flame-breasted Fruit-dove and Whiskered Pitta, and the extensive montane forests in this IBA are likely to support important populations of many of these birds. There were also records of several lowland species on the slopes of Mt Cetaceo, and the highly threatened Isabela Oriole has been recorded nearby. The extensive forests in this IBA are likely to support significant numbers of Philippine Eagle.
Non-bird biodiversity: This is the only known locality for the recently described endemic Sierra Madre Shrew-mouse Archboldomys musseri. Though incompletely surveyed for mammals, initial information indicates that it supports a high mammalian diversity, including populations of Luzon endemic species such as the Luzon Pygmy Fruit Bat Otopteropus cartilagonodus and Northern Luzon Cloud Rat Phloemys pallidus. Herpetofaunal surveys are still to be conducted on Mt Cetaceo, but this IBA may support a highly diverse and unique amphibian and reptilian fauna, like the adjacent Northern Sierra Madre Natural Park.
BirdLife International (2019) Important Bird Areas factsheet: Peñablanca Protected Landscape and Seascape. Downloaded from http://www.birdlife.org on 16/07/2019.