Zoological Studies

Vol. 59, 2020

(update: 2020.10.27; 11.30)

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

Norman T-L. Lim1,2,3,*, Douglas A. Kelt2, Kelvin K.P. 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, Faculty of Science,  National University of Singapore. 2 Conservatory Drive, Singapore 117377, Singapore. E-mail: kelvinlim@nus.edu.sg (KKP Lim)
4Institute for Tropical Biology and Conservation, Universiti Malaysia Sabah. 88400 Jalan UMS, Kota Kinabalu, Sabah, Malaysia.
E-mail: hbtiandun@gmail.com (Bernard)

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]) in oil palm plantations in Sabah (East Malaysia), and the existence of spillover effect whereby additional vertebrate scavengers from adjacent forest patches result in greater disease control in 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 the carcasses 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 in which STEC counts were marginally higher in plantation sections near forest patches, and human hunting along the forest-plantation boundaries could explain this. We propose that making oil palm plantations scavenger-friendly could yield great human health benefits for the millions of workers employed in this rapidly-expanding industry, without drastically changing 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 diarrhea-causing bacteria in tropical plantations. Zool Stud 59:63. doi:10.6620/ZS.2020.59-63.