Coyote, Canis latrans , Predation on a Bison, Bison bison , Calf in Yellowstone National Park

Abstract

We observed a single adult male Coyote (Canis latrans) kill a Bison (Bison bison) calf in Yellowstone National Park. The predation is, to our knowledge, the only direct and complete observation of a lone Coyote capturing and killing a Bison calf. The bison calf had unsuccessfully attempted to ford a river with a group and subsequently become stranded alone in the territory of a six-year-old alpha male Coyote.

Full text

260
In the Yellowstone ecosystem, Coyote spring/sum-
mer diet consists of small mammals and ungulate
neonates, primarily American Elk calves (Cervus ela-
phus), but also Pronghorn (Antilocapra americana)
calves and the fawns of Mule Deer (Odocoileus
hemionus) and White-tailed Deer (O. virginianus)
(Murie 1940; Gese and Grothe 1995; Gese et al. 1996).
Bison (Bison bison) appear to be a rare food source
for Coyotes. Murie’s (1940) analysis of 5086 Coyote
scats showed a percentage occurrence of 0.20% Bison,
and Murie found it unlikely that Coyotes would kill
Bison calves, recording that anecdotal reports of the
same “lacked proof” (page 117). More recently, a study
of Coyote predation on large ungulates in Yellowstone
found that both White-tailed Deer and Elk were killed
by packs of Coyotes hunting together in winter (Gese
and Grothe 1995). No predation on Bison was record-
ed in either of these Yellowstone Coyote studies. Cir-
cumstantial evidence at kill sites in Yellowstone has
suggested that predation on Bison calves by groups of
Coyotes may occur, but no report has been published.
A single instance of cooperative hunting by a Wolf
(Canis lupus) accompanied by a pack of four Coyotes
resulted in a Bison calf mortality (Smith et al. 2001).
However, successful solo predation by a Coyote on a
Bison has not, to our knowledge, been previously
observed. An instance of predation on a calf after sep-
aration from the herd was observed in Elk Island
National Park, Canada (Lu Carbyn, personal commu-
nication); however, a fence served to trap the calf. Our
observation therefore extends what has been known
about the predatory capacity of Coyotes with regard
to large ungulates.
The observers (GR, ACB, and KL) arrived at a van-
tage point on the Lamar River, Yellowstone National
Park (44°54′48.774'N, 110°16'28.28'W) on 28 May
2009 at 1825 h. Yellowstone cinematographer Bob
Landis reported (personal communication) that, at ap-
proximately 0700 h, a cow-calf herd of Bison swam the
river from south to north, northeast of the observers’
vantage point. During the crossing, a calf was washed
300–500 m downriver from the main group, emerg-
ing on the northern bank 100 m east of the vantage
point. The Bison herd proceeded southward, leaving
the calf behind on the opposite side of the river. By
1600 h, the Bison calf had bedded down west of the
vantage point and the Coyote was present approxi-
mately 10 m from the calf. When GR, ACB, and KL
arrived, the Coyote had already attacked the calf once,
according to observers already present.
The Coyote, M361, was radio-tagged in October of
2004 (capture weight 13.2 kg) and had been monitored
continuously since then. At the time of the event, he
was the six-year-old alpha male of the Paradise Park
pack, occupying a known home range which encom-
passed the kill site. The mean weight of Bison calf
neonates is ~23 kg (Mattson 1997), thus the calf out-
weighed Coyote M361 by a factor of two.
The following observations were recorded on 28
May 2009:
1939 h M361 approached the bedded Bison calf from the
rear and bit repeatedly at the hind legs. The calf stood up
kicking, striking M361 in the head. This interaction lasted
approximately 30 seconds, after which M361 moved to a
position 10 m from the calf and bedded down. The calf
remained standing.
2014 h The calf lay down approximately 10 m away from
M361.
2132 h M361 stood up and attacked the calf. The calf stood
up and kicked at M361 as he bit at the calf’s back legs.
M361 then bit the neck of the calf and pulled the calf to
Notes
Coyote, Canis latrans, Predation on a Bison, Bison bison, Calf in
Yellowstone National Park
J. W. SHELDON, GREGORY REED, A. CHEYENNE BURNETT, KEVIN LI, and ROBERT L. CRABTREE
Yellowstone Ecological Research Center, 2048 Analysis Drive, Bozeman, Montana 59718 USA
Sheldon, J. W., Gregory Reed, A. Cheyenne Burnett, Kevin Li, and Robert L. Crabtree. 2009. Coyote, Canis latrans, predation
on a Bison, Bison bison, calf in Yellowstone National Park. Canadian Field-Naturalist 123(3): 260–261.
We observed a single adult male Coyote (Canis latrans) kill a Bison (Bison bison) calf in Yellowstone National Park. The
predation is, to our knowledge, the only direct and complete observation of a lone Coyote capturing and killing a Bison calf.
The bison calf had unsuccessfully attempted to ford a river with a group and subsequently become stranded alone in the
territory of a six-year-old alpha male Coyote.
Key Words: Coyote, Canis latrans, Bison, Bison bison, predation, Yellowstone.

2009 NOTES 261
the ground. The calf struggled for approximately two
minutes as M361 continued to hold onto its neck.
2134 h The calf stopped moving. M361 lay down next to the
calf.
2138 h M361 began feeding on the calf.
The predation sequence, which began before 1800 h,
was concluded at 2134 h, an elapsed time of 3.5 hours.
This “slow-motion” predation method has been
observed in other ungulate encounters between Coy-
otes and Elk and White-tailed Deer: Gese and Grothe
(1995) observed predation sequences by Coyotes last-
ing up to 21 hours. Prey may undergo physiological
shock and/or become stiff during the extended inter-
action, providing a strategic advantage for the Coyotes.
The extent to which shock/hypothermia resulting from
the Bison calf’s river crossing effort contributed to its
vulnerability is unknown.
Coyotes are opportunistic predators capable of kill-
ing ungulate prey, usually hunting in packs. However,
Bison embody a formidable set of anti-predator adap-
tations, including well-developed maternal guarding
behaviors (Carbyn and Trottier 1987, 1988), general
herd behaviors of cow-calf groups, and size constraints
that regulate prey acquisition by the relatively small-
framed and light-weight Coyote. The cost of predation
attempts on ungulate neonates is demonstrably high:
an alpha female Coyote with pups in the den was killed
during a predation attempt on an Elk calf (unpublished
data; this study; 2005), with her post-mortem indicat-
ing blunt-force trauma as the cause of death. Certainly,
predation attempts on ungulate neonates are a high-
risk activity for Coyotes. Notably, in eight out of nine
predation attempts on large ungulate prey, the alpha
male led the attack (Gese and Grothe 1995), as was
also the case in our observation. In this instance, the
stranding of the Bison calf was a causal factor lead-
ing to its death.
The observed successful kill by a single adult male
Coyote shows that predation on Bison calves may be
possible under certain, albeit rare, conditions involving
separation of a calf from its mother. It also shows that
the size/weight limit of prey for adult Coyotes may be
revised slightly upward. The ecological context for
the observed predation suggests that it may be part of
a larger prey-switching phenomenon accompanying
changes in spring use areas by ungulate prey, prima-
rily Elk (Garrott et al. 2007). Our observation is of
additional interest because the Yellowstone ecological
community embodies the southernmost outpost of an
intact and functioning ungulate-predator system in
North America, surrounded by areas of increasingly
intensive human activity.
Acknowledgments
We acknowledge and thank the Yellowstone Cen-
ter for Resources, Yellowstone National Park, the
Yellowstone Ecological Research Center, and Bob
Landis. Observers were Gregory Reed, A. Cheyenne
Burnett, and Kevin Li.
Literature Cited
Carbyn, L. N., and T. Trottier. 1987. Responses of bison
on their calving grounds to predation by wolves in Wood
Buffalo National Park. Canadian Journal of Zoology 65:
2072-2078.
Carbyn, L.N., and T. Trottier. 1988. Descriptions of wolf
attacks on bison calves in Wood Buffalo National Park.
Arctic 41: 297-302.
Garrott, R. A., J. E. Bruggeman, M. S. Becker, S. T.
Kalinowski, and P. J. White. 2007. Evaluating prey
switching in wolf-ungulate systems.Ecological Applica-
tions 17: 1588-1597.
Gese, E. M., and S. Grothe. 1995. Analysis of coyote preda-
tion on deer and elk during winter in Yellowstone National
Park, Wyoming. American Midland Naturalist 133: 36-43.
Gese, E.M., R. L Ruff, and R. L. Crabtree. 1996. Foraging
ecology of coyotes (Canis latrans): the influence of extrin-
sic factors and a dominance hierarchy. Canadian Journal
of Zoology 74: 769-783.
Mattson, D. J. 1997. Use of ungulates by Yellowstone griz-
zly bears Ursus arctos. Biological Conservation 81(1-2):
161-177.
Murie, A. 1940. Ecology of the coyote in the Yellowstone.
National Park Service Fauna Series, Number 4. U.S. Gov-
ernment Printing Office, Washington.
Smith, D. W., L. D. Mech, M. Meagher, W. E. Clark, R.
Jaffe, M. K. Phillips, and J. A. Mack. 2000. Wolf-bison
interactions in Yellowstone National Park. Journal of
Mammalogy 81: 1128-1135.
Smith, D. W., K. M. Murphy, and S. Monger. 2001. Killing
of a Bison, Bison bison, calf by a Wolf, Canis lupus, and
four Coyotes, Canis latrans, in Yellowstone National Park.
Canadian Field-Naturalist 115: 343-345.
Received 6 July 2009
Accepted 11 May 2010