Ecological Effects of a Declining Red Wolf Population

Abstract

Carnivores, especially wolves (Canis sp.), have profound impacts on their ecosystems, affecting the abundance and behavior of prey and competitors, but this has not been examined for red wolves (C. rufus). We studied a population of red wolves that was reintroduced to eastern North Carolina in 1987, initially thrived, but experienced a population crash in 2014. We evaluated changes in the relative abundance of prey and competitor species during the red wolf decline with 25 camera traps run in the Red Wolf Recovery Area from 2015 – 2021. If red wolves were having an ecological effect on the mammal community, we expected this effect would decline as the wolf population waned, resulting in increases in prey and competitor populations. Supporting this, we found that relative abundance increased for most prey and competitor species including American black bear (Ursus americanus), bobcat (Lynx rufus), Virginia opossum (Didelphis virginiana), and Northern raccoon (Procyon lotor). For all species this increase was most notable after spring 2018, the first season without wolf reproduction. For some species, the increase was dramatic, with a doubling of the detection rate for raccoon, bear, and bobcat in the spring of 2021 compared to the spring of 2018. Our results support the hypothesis that red wolves had a strong effect on their ecosystems by suppressing prey and competitor populations when they were at their peak. The delay between the wolf decline and ecosystem response suggests that there could be a 2–3-year time lag in the effects of the wolf population on the species around them and/or that the ecological release was only notable when the wolves reached their lowest population size and failed to breed. This study shows that reintroduction of large predators can play important ecological roles, but their effects decline if their numbers dwindle to critically low numbers.