The most extensive rainforest formations present in the Selai side of Endau-Rompin is the lowland dipterocarp forest. Dominated by towering trees of the Dipterocarpaceae family, this forest is among the most species-rich terrestrial ecosystems on earth.
Riparian habitats alongside the rivers possess a distinct plant community rich in herbaceous and epiphytic plants. The Pelawan, a relative of the Australian gum tree is one of the most recognizable trees here with its beautiful grey-white peeling bark. Semi-aquatic plants known as rheophytes occupy the mist-laden areas around waterfalls, the banks of fast-flowing streams and rocky islands on the rivers.
Lower montane forests occupy the park’s granitic peaks at elevations of around 1,000 m above sea level. Here, the dipterocarps give way to oaks, chestnuts and conifers while gnarled, twisted trees with flat crowns and leathery leaves such as the Gelam Bukit and Rhu Bukit occupy the exposed, windswept summits.
Being the largest protected area in southern Peninsular Malaysia, the park plays a key role in the conservation of globally-threatened large mammals, including the Malayan Tiger, Asian Elephant, Malayan Tapir and Sunbear. The tiger’s preferred source of nourishment, the Sambar deer is present in the park, together with the barking deer and two species of mousedeer – the smallest hoofed animals in the world.
Johor is the only part of the peninsula where populations of the Bearded Pig still persist. This species is larger, lighter in color and reputedly less aggressive than the more widespread Eurasian Wild Pig.
Monkeys are represented in the park by the Long-tailed and Pig-tailed macaques plus two species of langurs. The more often seen Dusky Langur is distinguished by the spectacle-like rings around its eyes, whereas the Banded Langur has black fur with white bands on the underside of its body and limbs.
The park is also an important habitat for a few other globally-threatened mammals such as the Sunda Pangolin, White-handed Gibbon and Sunda Slow Loris, as well as many other smaller mammals including civets, squirrels and treeshrews.
The park, together with the adjacent Endau-Rompin State Park in Pahang was listed as an Important Bird & Biodiversity Area (IBA) in 2003 by BirdLife International. At least ten globally-threatened birds have been recorded in the IBA, including the Helmeted Hornbill and Straw-headed Bulbul.
Over 100 species of fish have been recorded in the park; the most abundant being the cyprinids, loaches and catfishes. Predatory fishes sought after by sports fishermen, including the Malayan Mahseer (Kelah), Flower Snakehead (Toman Bunga), and Hampala Barb (Sebarau) lurk in the deep pools (lubuk) along the rivers. While permits are given for angling at certain spots, the key spawning sites are strictly off-limits.