Gull (Laridae) Taphonomy at Shoals Marine Laboratory, Maine, USA

Abstract

A fundamental question for any outdoor forensic scene that has undergone scavenger dispersal is how far recovery teams must search in order to collect all possible human remains. While dispersal patterns and direct damage to bone from feeding have been studied for terrestrial mammals and inland avian species, very little attention has been paid to marine shore contexts and the role that sea birds play in dispersal of bones. The Shoals Marine Laboratory is located on Appledore Island, ME, USA, which also is home to large colonies of seasonally nesting gull (Laridae) species, primarily herring gull (Larus argentatus) and great black backed gulls (L. marinus). These species are known scavengers that have been little studied for their direct effects upon large vertebrate remains. The island setting allows for studies that isolate the behavior of avian species due to the lack of any large terrestrial scavengers, especially canids, thus preventing the need for samples to be placed on platforms, within fences, or other artificial scavenging scenarios. A pilot project in 2021 determined that both species fed upon and dispersed isolated, fresh cattle (Bos taurus) cervical vertebrae an average distance of 10 m and a maximum of 85 m.

The proposed research will examine the dispersal and feeding damage caused on large vertebrate remains in five overlapping stages: (1) scavenging upon fresh, isolated nonhuman long bones and crania; (2) scavenging upon introduced whole pig (Sus scrofa) carcasses; (3) scavenging upon naturally occurring harbor seal (Phoca vitulina) carcasses; (4) collection of nonhuman bones scavenged from human-generated trash on the mainland and transported to the island by the gulls to provision their young; and (5) GPS tracking of adult gulls to determine their foraging distances and locations, including near and within urban areas, in this coastal environment. These results will be compared with previous research on avian feeding and dispersal in an inland terrestrial environment in Holliston, MA. It is hypothesized that Laridae species will disperse bone at greater distances than inland avian species due to their aggressive flocking behavior and vocal signalling of other birds upon the discovery of food sources. It is also hypothesized that the damage patterns caused by gull feeding can be distinguished from the taphonomic effects of other scavenging species and from human-caused trauma. The dispersal results will be used to formulate best search and recovery practices for dispersed human remains in coastal environments. CA/NCF