Variation in peccary populations: landscape composition or competition by an invader?
2000
Gabor, Timothy M. | Hellgren, Eric C.
A fundamental challenge in population ecology is determining the causes of variation in animal abundance. Biological invasions by nonnative species are increasing, especially due to anthropogenic influences. Introduced species alter factors that influence populations, including resource distribution and abundance, predation, and competition. Feral pigs (Sus scrofa), the most widespread exotic ungulate in the world, have had an adverse effect on most ecosystems where they have been introduced. In the United States, the range of feral pigs overlaps with collared peccaries (Tayassu tajacu) in the thornscrub savanna of southern Texas, presenting the possibility of competition between these ecologically similar species. We studied two adjacent peccary populations, one sympatric with feral pigs and one allopatric to pigs, to determine the influence feral pigs have on native collared peccaries. Demography and landscape use of peccaries were compared between treatments. The peccary population on the pig‐absent site had 5–8‐fold higher densities, larger herd and group sizes, and smaller range and core area sizes than the population on the pig‐present site. Reproductive rates and habitat selection did not vary between populations. These differences suggested negative competitive influences of pigs on peccaries. However, differences at the landscape scale, i.e., fragmentation, between treatment areas suggested an alternative, or compounding, factor affecting population variability in collared peccaries.
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