DOI: 10.5061/dryad.8gtht76r7
title: Data for the article: Trophic niche partitioning between two prey and their incidental predators revealed various threats for an endangered species

description: Documenting trophic niche partitioning and resource use within a community
 is critical to evaluate underlying mechanisms of coexistence, competition
 or predation. Detailed knowledge about foraging is essential as it may
 influence the vital rates, which, in turn, can affect trophic
 relationships between species and population dynamics. The aims of this
 study were to evaluate resource and trophic niche partitioning in
 summer/autumn between the endangered Atlantic-Gaspésie caribou (Rangifer
 tarandus caribou) population, moose (Alces americanus) and their
 incidental predators, the black bear (Ursus americanus) and coyote (Canis
 latrans), and to quantify the extent to which these predators consumed
 caribou. Bayesian isotopic analysis showed a small overlap in trophic
 niche for the two sympatric ungulates suggesting a low potential for
 resource competition. Our result also revealed that caribou occupied a
 larger isotopic niche area than moose, suggesting a greater diversity of
 resources used by caribou. Not surprisingly, coyote consumed mainly deer
 (Odocoileus virginianus), moose, snowshoe hare (Lepus americanus), and
 occasionally caribou, while bears consumed mainly vegetation and, to a
 lesser extent, moose and caribou. As coyotes and bears also feed on plant
 species, we documented trophic niche overlap between caribou and their
 predators, as searching for similar resources can force them to use the
 same habitats and thus increase the encounter rate and, ultimately,
 mortality risk for caribou. Although the decline of the Gaspésie caribou
 population is mostly driven by habitat-mediated predation, we found
 evidence that the low level of resource competition with moose added to
 the shared resources with incidental predators, mainly bears, may
 contribute to jeopardize the recovery of this endangered caribou
 population. Highlighting the trophic interaction between species is needed
 to establish efficient conservation and management strategies to insure
 the persistence of endangered populations. The comparison of trophic
 niches of species sharing the same habitat or resources is fundamental to
 evaluate the mechanisms of coexistence or competition and eventually
 predict the consequences of ecosystem changes in the community.
description: We captured 44 caribou in the
 winter of 2013 and 2014 across the Gaspésie caribou range using a net gun
 fired from a helicopter. We collected caribou hair samples from the rump
 of the animal, and dried and stored it in paper bags at ambient
 temperature until processing. We used the same sampling and conservation
 protocol for hair samples collected from 90 moose, 127 coyote and 57 black
 bear carcasses across the three Wildlife Reserves that overlap the
 Gaspésie National Park (Fig. S1). Moose were harvested between September
 and October 2018 during the sport hunting season whereas coyotes and bears
 were trapped during the annual predator control program between June 2016
 and October 2018 across the Gaspésie caribou range. The capture and
 manipulation protocols were authorized by the Animal Welfare Committee
 [Université du Québec à Rimouski (hereafter UQAR) certificate
 #CPA-52-13-112; Ministère des Forêts, de la Faune et des Parcs (hereafter
 MFFP) certificate #CPA FAUNE 13-08].
 We collected samples
 opportunistically from all potential food sources consumed by moose,
 coyotes and bears to describe the composition of their diet. We collected
 hair samples from 22 individuals belonging to 6 different species that
 were accidentally trapped during the predator control program, including 4
 white-tailed deer (<em>Odocoileus virginianus</em>), 1
 snowshoe hare (<em>Lepus americanus</em>), 2 large rodents
 (groundhog, <em>Marmota monax</em>, North American
 porcupine, <em>Erethizon dorsatum</em>), 8 Canada lynx
 (<em>Lynx canadensis</em>) and 7 moose (<em>Alces
 americanus</em>). We also collected hairs from 22 individuals
 belonging to 6 species that were harvested by sport trappers or
 opportunistically collected in the ZEC Casault during summer, including
 five different species of rodents (1 red squirrel, <em>Tamiasciurus
 hudsonicus</em>, 2 common voles, <em>Microtus
 arvalis</em>, 5 deer mice, <em>Peromyscua
 maniculatus</em>, 6 Northern flying squirrels, <em>Glaucomys
 sabrinus</em>, and 1 pygmy shrew, <em>Sorex
 minutus</em>), and one species of large rodent (7 North American
 beaver, <em>Castor canadensis</em>). We also collected the
 feathers of 3 ruffed grouses (<em>Bonasa umbellus</em>) and
 hair from 4 snowshoe hares which were harvested by sport hunters in the
 ZEC Casault. We dried and stored hair and feathers in paper bags at
 ambient temperature until processing.
 Finally, in the study area in
 2017, we collected opportunistically six insects from three species
 belonging to the coleopteran (1 beetle) and hymenoptera orders (3 ants and
 2 wasps). We also collected plant samples in July 2017 belonging to 46
 different species in the montane boreal forest area of Mount Albert
 (<em>n</em> = 93) and Mount Logan (n = 72) in the Gaspésie
 National Park and of Petit Mount Ste-Anne (<em>n</em> = 53) in
 the Chic-Chocs Wildlife Reserves (see details in Appendix S1). Plant
 sampling was authorized by the Société des Établissements de Plein Air du
 Québec, which manages the Gaspésie National Park and the Chic-Chocs and
 Matane Wildlife Reserves [certificate #
 PNG-2017042703]. We randomly collected three replicates per
 species and froze them at -20°C until they were processed. We freeze-dried
 insect and plant samples for 48h, ground them into a fine powder using a
 CryoMill (Jardine et al., 2003), and stored them in a desiccator until the
 stable isotope analysis.
description: Please have a look at the ReadMe file joined.