DOI: 10.5061/dryad.d51c5b06t
title: Severe environmental conditions create severe conflicts? A novel ecological pathway to extreme coyote attacks on humans

description: 1) Identifying the circumstances and causes of carnivore attacks on humans
 is important for prevention of future incidents as well as employing
 effective wildlife management strategies. Cape Breton Highlands National
 Park (CBHNP) in Nova Scotia has experienced multiple attacks by coyotes
 (Canis latrans) on humans, including a fatal attack on an adult in 2009.
 2) Here we use a combination of data on space use and diet collected from
 2011–2013 to reveal that limited resources and a reliance on a large
 ungulate (moose, Alces americanus) as the mechanism leading to aggression
 by coyotes in CBHNP. 3) Resident coyotes exhibited large home range sizes
 (mean=77.5 km2) indicative of limited resources and spatiotemporal
 avoidance of human activity. Carbon (d13C) and nitrogen (d15N) isotope
 values of sub-sampled coyote whiskers (n=32), which provide a longitudinal
 record of diet over the months before collection, revealed little intra-
 and inter-individual variation with nearly all individuals specializing on
 moose, a pattern that agrees with indices of natural resource
 availability. Specifically, stable isotope mixing models show that moose
 was the most important prey for most coyotes (25/32), representing between
 41% and 78% of dietary inputs. Only four coyotes exhibited use of
 anthropogenic resources (food), and only one of seven coyotes involved in
 attacks on people had been consuming human foods before the attacks. 4)
 Synthesis and Applications: We have described a unique ecological system
 in which a generalist carnivore has expanded its niche to specialize on a
 large prey species, with the unfortunate consequence of also expanding
 pathways to conflicts with people. Our results suggest extreme unprovoked
 predatory attacks by coyotes on people are likely to be quite rare and
 associated with unique ecological characteristics. Extreme management
 actions such as bounties are unnecessary, but managers may need to employ
 hazing or lethal removal earlier in the conflict process than under normal
 circumstances. Also, users of these areas should be made aware of the
 risks coyotes pose and encouraged to take precautions. 
description: We analyzed vibrissae from 32 (17 F, 15 M) coyotes (Table S3),
 including 19 whiskers from coyotes that were live-captured and
 radiocollared, 5 from the 2009 lethal attack including 2 that were
 confirmed to be involved in the attack, 4 from coyotes lethally removed
 following human-coyote incidents including attacks, and 4 from unmarked
 individuals captured during trapping or recovered as roadkill. We also
 opportunistically collected hair from potential coyote prey items that
 occur in the study area during 2012–2014 for stable isotope analysis
 (Table S4), including southern red-backed voles (Myodes gapperi; n=27),
 shrews (Sorex spp.; n=49), snowshoe hare (Lepus americanus; n=17),
 white-tailed deer (Odocoileus virginianus; n=20), and moose (Alces
 americanus; n=21).  Red-backed voles and shrews were grouped as small
 mammals because they had statistically indistinguishable δ13C and δ15N
 values. Samples were collected during unrelated small mammal surveys or
 from roadkill animals within the study area. We also analyzed the isotopic
 composition of local human residents to serve as a proxy for a consumer of
 anthropogenic resources that could be directly compared to measured coyote
 isotope values; human hair samples were collected opportunistically from
 local barbershops. Keratin samples from coyotes
 (vibrissa), potential prey (hair), and humans (hair) were rinsed in 2:1
 chloroform:methanol solution to remove surface contaminants. Hair samples
 were homogenized with surgical scissors and vibrissa were sub-sampled into
 0.2–0.3mg segments using nail clippers; this weight range represents the
 lowest weight for which we can reliably generate δ13C and δ15N data for
 keratin. δ13C and δ15N values were measured with a Costech 4010 elemental
 analyzer (Valencia, CA) coupled to a Finnegan Delta Plus XL isotope ratio
 mass spectrometer at the University of Wyoming Stable Isotope Facility
 (Laramie, WY). Isotopic results are expressed as d values: δ13C or δ15N =
 1000* [(Rsample - Rstandard / Rstandard) – 1], where Rsample and Rstandard
 are the 13C/12C or 15N/14N ratios of the sample and standard,
 respectively; units are parts per thousand or per mil (‰). Analytical
 precision was determined via repeated analysis of internal reference
 materials calibrated to international standards; within-run standard
 deviation of an acetanilide standard was ≤0.2‰ for both δ13C and δ15N
 values. We applied tissue-specific δ13C and δ15N trophic discrimination
 factors (TDF) of 2‰ and 3‰ (Fig. 3) respectively reported for captive
 wolves (Canis lupus; Derbridge et al. 2015) to directly compare isotope
 values of keratin tissues from coyotes (vibrissae) to that of potential
 prey (hair); we also used these TDFs in the mixing model analysis (see
 below). Lastly, experiments on captive canids and other mammalian
 carnivores show that vibrissae growth rates likely scale with body mass
 (Hirons et al. 2001, Robertson et al. 2013, Tyrrell et al. 2013, Stanek
 2014). Based on these studies, we assume that coyotes (15–20kg) will have
 mean vibrissae growth rates in the range of 8–12 cm/year. Since the mean
 (±SD) length of a vibrissa collected from the CBHNP was 6.2±0.5 cm, we
 estimate that our sub-sampling approach produces a ~6- to 9-month
 longitudinal record of dietary information for each individual coyote but
 acknowledge that seasonal variation in vibrissae growth rates (McLaren et
 al. 2015) could impact this estimate.