Zoological Studies

Vol. 59, 2020

(update: 2020.10.27)

Vertebrate Scavengers Control Abundance of Diarrheal-causing Bacteria in Tropical Plantations

Norman T-L Lim1,2,3,*, Douglas A Kelt2, Kelvin KP Lim3, and Henry Bernard4


1National Institute of Education, Nanyang Technological University. 1 Nanyang Walk, Singapore 637616, Singapore. *Correspondence: E-mail: norman.lim@nie.edu.sg (Lim). Tel: +65-67903882. Fax: +65-68969414.
2Wildlife, Fish, & Conservation Biology, University of California, Davis. One Shields Avenue. Davis, CA 95616, USA. E-mail: dakelt@ucdavis.edu
3Lee Kong Chian Natural History Museum, National University of Singapore. 2 Conservatory Drive, Singapore 117377, Singapore. E-mail: kelvinlim@nus.edu.sg
4Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah. 88400 Jalan UMS, Kota Kinabalu, Sabah, Malaysia. E-mail: hbtiandun@gmail.com

Received 18 May 2020 / Accepted 26 September 2020
Communicated by Benny K.K. Chan

Scavenging is a common phenomenon, particularly amongst carnivorous vertebrates. By consuming carrion, vertebrate scavengers reduce resource availability for both pathogenic bacteria and their insect vectors. We investigated the ability of wild vertebrate scavengers to control agents of human diarrheal diseases (specifically Salmonella spp. and Shiga toxin-producing Escherichia coli [STEC]) at oil palm plantations in Sabah (East Malaysia), and the existence of spillover effect whereby additional vertebrate scavengers from adjacent forest patches resulted in greater disease control at plantation sections near these forest edges. Experimental carcasses were removed by common scavengers (Varanus salvator, Canis lupus familiaris, and Viverra tangalunga) at different time points, and this determined the length of time that carcass persisted in the environment. The amount of pathogenic bacteria on the surfaces of filth flies collected above the experimental carcasses was positively correlated to the duration of carcass persistence, and reduction in pathogenic bacterial abundances was largely due to carcass consumption by these vertebrate scavengers. Instead of a predicted positive spillover effect (greater scavenger activity near forest edges, hence reduced pathogen abundance), we detected a weak inverse spillover effect where STEC counts were marginally higher at plantation sections near to forest patches, and we suspect that human hunting along the forest-plantation boundaries could be a potential reason. We propose that making oil palm plantations scavenger-friendly could yield significant human health benefits for the millions of workers employed in this rapidly-expanding industry, without drastic changes in current management practices.

Key words: Carcass removal, Filth flies, Salmonella, Shiga toxin-producing E. coli, Spillover effect.

Citation: Lim NTL, Kelt DA, Lim KKP, Bernard H. 2020. Vertebrate scavengers control abundance of diarrheal-causing bacteria in tropical plantations. Zool Stud 59:0uu. doi:-.