The role of canids in the dispersal of commercial and ornamental palm species

Abstract

Palms, like many plants, rely on frugivorous animals to disperse their seed. Large-scale human-mediated dispersal for their production and amenity values has seen the introduction of palms into a wide range of ecosystems where they subsequently have become naturalized. A wide range of native as well as exotic species has adapted to palm drupes as a food source and serve as dispersal vectors. Most canids are opportunistic generalist feeders that consume various quantities of fruit such as drupes of palms. This is the first comprehensive review examining the role of canids in the dispersal of ornamental palm species. It can be shown that the effectiveness of canids as vectors in the dispersal of Phoenix and Washingtonia palms is heavily dependent on a species’ ability to be sympatric with humans, whereby coyotes, golden jackals and red foxes have been shown to be particularly adaptable. The marking behaviour of canids, with its repeated defecation at the same locality, and long gastrointestinal transit times coupled with large home ranges as well as the improved germination rates following passage through the gut all favour a palm’s successful dispersal. Canids are particularly significant and effective dispersers over long distances and in spaces where perches (favoured by avian vectors) are absent. The review has shown some gaps in the literature and state of research: There is a lack of empirical data on gastrointestinal transit times among all canids bar domestic dogs and red foxes. Dietary studies often make little attempt at identifying and classifying the plant content of scats and stomachs. Wherein, studies consider the presence of palm seeds in scats, the quantity of seeds in a single scat is often not reported, nor is the state of the seed, such as the presence of chew or bite marks or the presence of exocarp fragments. Studies on home ranges are generally silent on actual linear travel distances which provide information on a vector’s capacity to disperse seed.