The taphonomic impact of scavenger guilds in southern Quebec during summer and fall in two distinct habitats

Abstract

Decomposition of human remains is a complex process impacted by many intrinsic and extrinsic factors. A less-studied extrinsic factor in forensic taphonomy are the scavengers that consume soft and hard tissue. Scavengers physically degrade and remove soft tissue, disperse, and destroy skeletal elements, which can make locating remains challenging. While invertebrate activity has been largely investigated, there is limited quantitative data available on vertebrate activity, particularly in Canada. This study aimed to determine which species (vertebrate and invertebrate) belong to the scavenger guilds in southern Quebec, and their potential taphonomic impact on the decomposition process. Two independent trials were conducted in 2020 using pig carcasses: one during summer in a forest habitat and one during fall in a grassland habitat. Each carcass was placed a minimum 100 m apart in semi-rural land. Vertebrate scavenger activity was recorded by continuous surveillance using trail cameras. Carcasses were also regularly visited to monitor the decomposition process and the activity of invertebrate scavengers. Overall, the vertebrate scavenger guilds included a narrow range of corvids, turkey vultures, coyotes, and skunks. The intensity of vertebrate scavengers was greater in the grassland habitat (fall), while the intensity of invertebrate scavengers was greater in the forest habitat (summer). With the exception of invertebrate scavengers, very few species visited during the fresh stage of decomposition, and the probability of body displacement increased as decomposition progressed. These results identify which scavengers have the greatest taphonomic impact and highlight the importance of incorporating scavenger impact when searching for human remains.

Seasonal impact of scavenger guilds as taphonomic agents in central and northern Ontario, Canada

“…However, further studies conducted in the cooler months are necessary to unravel these potential factors. Although very few forensically relevant scavenging studies have been conducted across multiple seasons, our findings are consistent with those reported for the Southern Ontario study in spring, summer, and fall [12], and the southern Quebec study in summer and fall [26].…”

“…Bald eagle, red fox, and pine marten were less prevalent and more intermittent in their scavenging behavior. It was originally hypothesized that the scavenger guild in central and northern Ontario would be distinct from that reported for Southern Ontario [12] and southern Quebec [26] as this region moves more into the boreal forest biome and has fewer urban centers. However, similar scavenger guilds were reported across all three studies.…”

“…All cameras were set to take a single photo following the detection of motion, with a 1‐min delay before subsequent images were taken. These settings were adapted from a prior study [26] and found to be suitable for the purposes of capturing optimal data, while balancing the requirements of SD card storage and battery life. Ambient temperature data were collected hourly at each site using an ONSET HOBO® Pendant data logger (UA‐002‐64), which allowed determination of the minimum, maximum, and average temperatures for each trial.…”

“…Although many of the abovementioned scavengers are found in Canada as well as the USA, the scavenging guilds across North America can vary considerably given the range of different environments. Within Canada, studies have been conducted in Central Alberta [24], Southern Ontario [12], and southern Quebec [26], but this encompasses only a small representation of Canada's many biomes. Even within specific regions, many variables can impact wildlife distribution including climate, habitat types, and proximity to urban centers [1].…”

“…However, it is possible that the vertebrate scavenging community will be different in other regions of Ontario, where larger mammals (e.g., coyotes, wolves, and black bears) are more commonly present. Furthermore, the presence and activity of scavengers-hence their taphonomic impact on human remains-is likely to change according to season and habitat [26].…”