DNA metabarcoding reveals a broad dietary range for Tasmanian devils introduced to a naïve ecosystem

Top carnivores are essential for maintaining ecosystem stability and
biodiversity. Yet, carnivores are declining globally and current in situ
threat mitigations cannot halt population declines. As such,
translocations of carnivores to historic sites or those outside the
species’ native range are becoming increasingly common. As carnivores are
likely to impact herbivore and small predator populations, understanding
how carnivores interact within an ecosystem following translocation is
necessary to inform potential remedial management and future
translocations. Dietary analyses provide a preliminary assessment of the
direct influence of translocated carnivores on a recipient ecosystem. We
used a metabarcoding approach to quantify the diet of Tasmanian devils
introduced to Maria Island, Tasmania, a site outside the species’ native
range. We extracted DNA from 96 scats and used a universal primer set
targeting the vertebrate 12S rRNA gene to identify diet items. Tasmanian
devils on Maria Island had an eclectic diet, with 63 consumed taxa
identified. Cat DNA was detected in 14% of scats, providing the first
instance of cats appearing as part of Tasmanian devil diets either via
predation or scavenging. Short-tail shearwaters and little penguins were
commonly consumed, corresponding with previous surveys showing sharp
population declines in these species since the introduction of Tasmanian
devils. Our results indicate that the introduction of carnivores to novel
ecosystems can be very successful for the focal species, but that commonly
consumed species should be closely monitored to identify any vulnerable
species in need of remedial management.