Mangrove ecosystem in Kilim contains high biodiversity of fauna. Being an island ecosystem, it supports a rich and diverse community of coastal microinvertebrates that thrive within the mangroves. Some 34 species of mangrove fauna comprising mainly crustaceans and mollusks also support a thriving seafood-based industry for the local community. The more important crustacean fauna includes portunid and grapsid crabs, as well as bivalves and gastropods, such as Cerathidia obtusa, which are all harvested and consumed locally.
Over 84 butterfly species in 5 families that include Papilionidae, Pieridae, Nymphalidae, Lycaenidae, and Heperiidae have been recorded for Langgun Island and Kisap area. About 26% (22 species) of butterflies differed from all species known for Peninsular Malaysia, including Euploea spp. Species richness of Kilim is reflected by members of Nymphalidae with 29 species represented in Langgun Island and 30 species in Kisap, while Pieridae was represented by 10 species in the former and 14 species in the latter, respectively. Such richness is reflected by the richness of Kilim flora, which provide the host and food source for these species.
There are 79 species of herpetofauna, comprising 1 caecilian, 23 anurans, five tortoises, 17 lacertilians, and 33 snakes. Langkawi has 78% of the total herpetofauna found on Tioman Island with many more that remains to be discovered. Among the most visible large reptiles in Langkawi are the Water monitors (Varanus salvator) that inhabit the mangrove and rocky shores in Kilim area.
The vertebrate diversity of Langkawi includes 25 species of known mammals, such as Colugo or the Flying lemur (Galeopterus variegatus), Lesser Flying Fox (Pteropus hypomelanus), and the Three-striped palm civet (Arctogalidia trivirgata). A total of 238 species of birds or 32% of the total known bird species of Malaysia, are found in Langkawi that include rare species that can be seen in the Kilim area, such as the Brown kingfisher (Halcyon amauroptera), Green Imperial Pigeon (Ducula aenea), and Pied hornbill (Anthracoceros albirostris) among others. Within the coastal ecosystem, the abundant vertebrate life thrive upon the bountiful invertebrate community as their food sources within the coastal intertidal habitats of Kilim.