Going to Bat for Nature
by Thomas Gomersall
Bats have long been given a bad rap, whether it’s their mythical association with vampires or more realistically, as disease reservoirs, particularly given the ongoing coronavirus pandemic.
Nevertheless, these flying mammals provide vital services within their ecosystems and even to humans, including in Hong Kong where almost half of all mammal species are bats. Fruit bats act as pollinators and seed dispersers for more than 300 plant species and are crucial players in reforestation efforts. Meanwhile, the smaller insectivorous species can catch hundreds of flying insects per hour — including mosquitoes and major crop pests — keeping their populations in check (Shek, 2006, p. 17, p. 81).
Wetlands represent particularly important habitats for bats due to their high insect densities, which are sometimes even higher than those of non-wetland areas (Stahlschmidt et al, 2012). Studies elsewhere in the world have found that many bats frequently forage above water and that bat species richness is positively linked to the presence, size and quality of wetlands (Russo & Jones, 2003; Straka et al, 2016). While studies on bat ecology are much more limited for Hong Kong, these patterns also appear to be true here. Mai Po Nature Reserve supports 13 of Hong Kong’s bat species and several species like the Horsfield’s bat and the lesser yellow bat are known to forage above water (Shek, 2006, p. 161, p. 205).
However, like all animals, bats need safe places to rest, breed and hide from predators. Trees such as the Chinese fan palm provide roosts for species like the short-nosed fruit bat. But for many smaller species in wetlands, including Mai Po, roosts are few and far between.
What’s limiting [bats] in the wetland areas are roosting opportunities,” says David Stanton, ecologist and director of the independent ecological consultancy, AEC Ltd. “There’s not a lot of big trees with cavities or fissures they could utilise.”
To address this, WWF has installed wooden bat boxes in several locations around Mai Po to provide extra roost sites for bats, a measure that has proved helpful for bat conservation in wetlands (Flaquer et al, 2006). The bat boxes supplement existing ones already installed by the Agricultural Fisheries and Conservation Department in the early 2000s as part of its bat-monitoring programme. In total, 13 bat species have been recorded in the reserve, the most abundant of which are the Japanese pipistrelle and least pipistrelle.
A full list of all mammals found in Mai Po is available here.
References
· Flaquer, C., Torre, I. and R. Ruiz-Jarillo. 2006. The value of bat-boxes in the conservation of Pipistrellus pygmaeus in wetland rice paddies. Biological Conservation, vol. 128: 223pp.–230pp.
· Russo, D. and Jones, G. 2003. Use of foraging habitats by bats in a Mediterranean area determined by acoustic surveys: conservation implications. Ecography, vol. 26(2): 197pp.–209pp.
· Shek, C.T. 2006. A field guide to the terrestrial mammals of Hong Kong, Agriculture, Fisheries and Conservation Department, Hong Kong SAR Government, Hong Kong. 17pp., 81pp., 161pp., 205pp.
· Stahlschmidt, P., Pätzold, A., Ressl, L., Schulz, R. and C.A. Brühl. 2012. Constructed wetlands support bats in agricultural landscapes. Basic and Applied Ecology, vol. 13: 196pp.–203pp.
· Straka, T.M., Lentini, P.E., Lumsden, L.F., Wintle, B.A. and R. van der Ree. 2016. Urban bat communities are affected by wetland size, quality and pollution levels. Ecology and Evolution, vol. 6(14): 4761pp.–4774pp.
