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Data from: Dingoes dining with death

Citation

Newsome, Thomas; Spencer, Emma (2021), Data from: Dingoes dining with death , Dryad, Dataset, https://doi.org/10.5061/dryad.rfj6q57b4

Abstract

Dingoes (Canis dingo) are known for hunting and killing animals to meet their energetic requirements, but like almost all predators they also scavenge animal remains. To improve our understanding of dingo scavenging ecology, we investigated the role of abiotic and biotic factors in shaping carcass utilisation by dingoes and further determined whether dingo scavenging influenced carcass persistence in the landscape. To do so, we monitored visitation and scavenging by dingoes using remote cameras positioned on 119 kangaroo carcasses in open and closed canopy habitats and in warm and cool seasons. The carcasses were monitored across multiple study sites, which incorporated forest, alpine and desert ecoregions in Australia. We found that season played an important role in shaping carcass utilisation by dingoes, as well as carcass persistence. Warmer seasons increased the rate of carcass discovery 6.3-fold in the Forest study site and 4.8-fold in the Alpine study site, and also increased the time dingoes spent feeding on carcasses in the Alpine study site. Further, across all study sites, carcasses persisted at least 4.7 times longer in cool compared with warm seasons. On the other hand, carcass utilisation by dingoes was not influenced by habitat, although carcasses were more likely to persist in open compared with closed canopy habitats in the Alpine study site. Finally, our study showed that dingo scavenging may contribute to substantial carcass removal in certain contexts. Indeed, decreased carcass persistence in the Forest study site was evident in the cool season, when dingo scavenging occurred during the first two weeks of monitoring. The variability in results highlights the complexity of patterns in dingo scavenging and, more broadly, of vertebrate scavenging. It emphasises the need to consider multiple abiotic and biotic factors to properly understand the functional roles of different scavenger species. Longer-term studies with additional seasonal replicates may also yield a more detailed picture of the role of dingoes as apex scavengers.

Methods

Study Sites

Our study sites cover two locations in New South Wales and one in Queensland, Australia. These sites were selected as they are home to a moderate-sized population of dingoes and represent diverse habitats. In particular, research was undertaken in the Wolgan Valley in the Blue Mountains, eastern New South Wales (NSW) (“Forest” study site; between August 2017 – February 2018), on the Snowy and Botherum Plains in Kosciuszko National Park, southern NSW (“Alpine” study site; between March 2018 – January 2019) and at Ethabuka Reserve in the Simpson Desert, western Queensland (“Desert” study site; between June – November 2018; Figure 1).

Carcass Monitoring

In each study site, we distributed 20 kangaroo carcasses in both cool (winter and autumn) and warm (summer, spring) periods, with half placed in open and half placed in closed canopy habitats. Our study sites included a mix of grassland (open) and woodland (closed) habitats in the Forest and Alpine study sites, and dune crest (open) and valley (closed) habitats in the Desert study site. Open canopy habitats lacked canopy cover and were at least 50 m from any densely forested or vegetated land. Closed canopy habitats had more than 20% canopy cover. We tried to ensure that these closed canopy sites were at least 50 m from any open space; however, this was not possible in the Desert study site due to the general sparsity of trees.In each season, carcasses were separated by at least 1km to mitigate scent travel between carcasses. We used dead, adult eastern grey kangaroos (Macropus giganteus; Forest and Alpine study sites) or dead adult red kangaroos (Osphranter rufus; Desert study site) sourced from nearby management culls. Any carcasses displaying evidence of disease (e.g. heavy parasite loads), were not used. Each carcass was placed into the field without freezing within 24 hours (warm period) or 36 hours (cool period) of collection. Scientific licenses/permits were obtained to relocate the kangaroo carcasses (SL 101901 and SPP WA0006737) and research was approved by the University of Sydney Animal Ethics Committee (Project number: 2017/1173).

To allow for ongoing monitoring and detection of dingoes visiting and feeding on each carcass, we fastened a Reconyx PC800 Hyperfire™ camera trap (Professional Reconyx Inc., Holmen, WI, USA) to a free-standing star picket, approximately 3–4 m away from each carcass. Each camera was programmed to take continuous photographs when triggered by thermal movement around the carcass (rapidfire, no wait period). To prevent complete removal of the carcasses from the remote camera monitoring frame, each carcass was secured to the ground by wire attaching the neck and achilles tendon of the animal to two metal stakes spaced ~0.6 m apart. Cameras were used to monitor carcasses until only skin and bones remained (< 4 months); however, at the Alpine study site carcasses were monitored for only 30 days due to the high risk of camera theft.

All photographs were tagged according to each new visitation event by one or more dingoes to a carcass, the number of dingoes present, whether the dingoes engaged in scavenging behaviour or not, and the date and time that the observation was recorded. A visitation event was considered new if it occurred ≥ 10 min from the previous visitation event by the same dingo. Different individual dingoes were identified using markings, size and sex. We then extracted four values from the images that we tagged including: “presence”, “scavenging”, “discovery time” and “total feeding time”. Presence was calculated as the number of carcasses that dingoes were recorded visiting, and scavenging was the number of carcasses where they were recorded feeding. Discovery time was calculated in decimal hours as the time between when the carcass was first positioned and the arrival of the first visiting dingo. Total feeding time was calculated as the sum of all feeding events at a given carcass for all dingoes. We calculated the duration of a given feeding event by subtracting the time at the start of the visit from the time at the end of the visit. We rounded all feeding visits to the closest minute; however, for visits less than 30 seconds, we considered the species present for 1 min rather than 0 mins. Using a combination of in-person visual inspection of the carcasses and inspection of camera images, we determined the number of days until complete carcass consumption. A carcass was defined as completely consumed when only skin, hair and/or bone remained.