Long‐term effects of forest fire on habitat use by siamangs in Southern Sumatra

Abstract

Forest fires can cause direct mortality to wildlife, and the associated habitat damage can reduce carrying capacity and population densities. However, little is known about long-term responses of animals to fire in the wet tropics. From 2000-2015, we examined siamang ranging patterns in habitat damaged by fire to assess the effects on these arboreal frugivores. We mapped home ranges (HR) of seven siamang groups inhabiting contiguous HR 3-5, 10-12, and 17-18 years post-fire. We predicted that if habitat connectivity or quality improved over time in burned areas, HR should become larger and centroid locations should shift toward recovering areas. Since territoriality constrains siamang ranging, we examined effects of social and habitat factors on ranging. By 18 years post-fire, tree density in the burned area had returned to the 1997 baseline, but composite LandSat images indicated that tree species composition differed in burned and unburned forest. Our data and the associated models indicated that HR sizes in burned forest increased over time whereas those in unburned forest did not. Centroid locations moved little (15.5 ± 6.9 m y-1) and their movement appeared to be predominantly influenced by social factors, although HR centroids in burned habitat shifted further into the burned area while those in adjacent unburned forest did not. In a large burned area unused by siamangs before 2012, two new groups were observed 15-17 years post-fire, although one subsequently disappeared. This is the first study of the long-term effects of fire on small ape habitat use. By 18 years post-fire, siamangs had incorporated some burned areas into their HR, but did not use heavily damaged areas. Reduced frugivore densities in burned areas may inhibit forest regeneration by disrupting seed dispersal.

Population densities ofHylobates agilisin forests with different disturbance histories in Ulu Muda Forest Reserve, Malaysia

“…Population compression may increase intraspecific competition with negative consequences for recruitment and long‐term persistence unless habitat quality is restored. For example, S. symphalangus in fire‐damaged habitat on Sumatra had lower infant and juvenile survivorship for at least five years post‐fire (O'Brien et al, 2003) and had smaller home ranges than S. symphalangus in adjacent areas of undamaged habitat for ≥12 years post‐fire (Lappan et al, 2021). If habitat quality remains poor, degraded areas may become population sinks for small apes, resulting in long‐term population declines or local extinctions (O'Brien et al, 2003).…”

Primate conservation: Lessons learned in the last 20 years can guide future efforts

“…For example, in the Amazon, the basal area of fruiting trees decline by 29% after a single surface fire and 62% after a second fire 36,37 and this recurrent fire leads to the extirpation of many large frugivores 36 . Similarly, in Sumatra, siamangs ( Symphlangus syndactylus ) do not use heavily burnt areas even 18 years post‐fire 38 . On the negative side, the climatic events that aggravated the fires in 1997 and 1998 are increasing in frequency and intensity in association with climate change, thus they are no longer newsworthy.…”

Remote monitoring, personnel extinguishment or helicopter extinguishment? How to control forest fires more effectively

“…Forests provide a large number of raw materials such as wood and rubber for people’s production and life. Forest ecosystems are also natural habitats for wildlife [ 2 ]. It has played a huge role in protecting species diversity.…”

“…For example, forest fires can affect tree mortality [ 12 ]. Years after forest fires, although the number of trees can recover to the original level, tree species will decrease [ 2 ]. Multiple fires can lead to vegetation degradation [ 13 ].…”