Age‐related variation in the trophic characteristics of a marsupial carnivore, the Tasmanian devil Sarcophilus harrisii

Abstract

Age‐related changes in diet have implications for competitive interactions and for predator–prey dynamics, affecting individuals and groups at different life stages. To quantify patterns of variation and ontogenetic change in the diets of Tasmanian devils Sarcophilus harrisii , a threatened marsupial carnivore, we analyzed variation in the stable isotope composition of whisker tissue samples taken from 91 individual devils from Wilmot, Tasmania from December 2014 to February 2017. Both δ 13 C and δ 15 N decreased with increasing age in weaned Tasmanian devils, indicating that as they age devils rely less on small mammals and birds, and more on large herbivores. Devils <12 months old had broader group isotopic niches, as estimated by Bayesian standard ellipses (SEA B mode = 1.042) than devils from 12 to 23 months old (mode = 0.541) and devils ≥24 months old (mode = 0.532). Devils <24 months old had broader individual isotopic niches (SEA B mode range 0.492–1.083) than devils ≥24 months old (mode range 0.092–0.240). A decrease in δ 15 N from the older whisker sections to the more recently grown sections in devils <24 months old likely reflects the period of weaning in this species, as this pattern was not observed in devils ≥24 months old. Our data reveal changes in the isotopic composition of devil whiskers with increasing age, accompanied by a reduction in isotopic variation both among population age classes and within individuals, reflecting the effect of weaning in early life, and a likely shift from an initially diverse diet of small mammals, birds, and invertebrates towards increasing consumption of larger herbivores in adulthood.

Isotopic niche variation in Tasmanian devils Sarcophilus harrisii with progression of devil facial tumor disease

“…For the individual longitudinal study, we included individuals based on three constraining factors, where individuals must have been free from clinical signs of DFTD when the first whisker was sampled, at least 18 months old at the first sampling occasion to reduce likelihood of age effects masking variation (Bell et al., 2020), and the two whiskers must have been sampled at least 6 months apart, to maximize the likelihood of independence of the two time points. In total, 18 individuals were selected; 10 had DFTD when sampled on the second occasion, while 8 “control” individuals were free of tumors on both sampling occasions.…”

The Macroscopic and Radiographic Skull and Dental Pathology of the Tasmanian Devil (Sarcophilus harrisii)

“…However, a lack of definitive demographic data of these specimens limits the capacity to draw meaningful conclusions regarding precise sex-specific or age-related anatomical and pathological findings. Sexual dimorphism in size in the extant Tasmanian devil is well-documented in the literature, with the male being larger than the female with regards to overall body weight and dimensions ( 1 – 5 , 8 , 9 ). Greater skull size has been documented in Tasmanian devils up to 30 months of age, as well as in males for the extinct dasyurid Sarcophilus laniarius ( 23 , 30 ).…”

“…The Tasmanian devil (Sarcophilus harrisii) is the largest extant carnivorous marsupial in the world (1)(2)(3)(4)(5). While its range historically extended throughout continental Australia, it is now only found in the wild inhabiting the island state of Tasmania, located south of mainland Australia across the Bass Strait (1,3,4).…”

“…While its range historically extended throughout continental Australia, it is now only found in the wild inhabiting the island state of Tasmania, located south of mainland Australia across the Bass Strait ( 1 , 3 , 4 ). Weighing ~8–10 kilograms for males and 6–7 kilograms for females, the Tasmanian devil is a pounce-pursuit predator, forager, and facultative scavenger ( 1 , 5 , 6 ). While younger devils favor a diet of smaller mammals, birds, amphibians, reptiles, and insects, as individuals age their diet shifts to primarily macropods such as Red-necked wallabies ( Notamacropus rufogriseus ) and Rufous-bellied pademelons ( Thylogale billardierii ), both as carrion and live prey ( 1 , 2 , 4 , 5 ).…”

Whisker growth in Tasmanian devils (Sarcophilus harrisii) and applications for stable isotope studies

“…We therefore propose an annual growth period, similar to other mammals: the harbor (Hirons et al 2001, Zhao andSchell 2004), gray (Greaves et al 2004), southern elephant (Beltran et al 2015), and leopard (Rogers et al 2016) seals. Bell et al (2020) estimated that Tasmanian devil whiskers grow for 5-9 months; however, they used a different approach to our work and did not look at the entire growth of a whisker to establish the k value. They measured growth between two points (via application of a single dose of fluorescent marker) assuming that growth was linear.…”