Bald Eagle Predation on Harbor Seal PupsAuthor(s): James L. HaywardSource: Northwestern Naturalist, Vol. 90, No. 1 (Spring, 2009), pp. 51-53Published by: Society for Northwestern Vertebrate BiologyStable URL: http://www.jstor.org/stable/20628115 .

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Spring 2009 General Notes

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35 Cronkhite Road, Whitehorse, YT, Y1A 5S9, Can ada. Submitted 12 September 2008, accepted 27 Oc tober 2008. Corresponding Editor: Paul Cryan.

NORTHWESTERN NATURALIST 90:51-53 Spring 2009

BALD EAGLE PREDATION ON HARBOR SEAL PUPS

James L Hayward

Key words: Bald Eagles, Haliaeetus leucoce

phalus, Harbor Seals, Phoca vitulina, pups, pre

dation, Protection Island, Washington

Bald Eagles (Haliaeetus leucocephalus) are pri

marily scavengers but also prey on a variety of

animals including fish, seabirds, and mammals

(Stalmaster 1987). Diet is largely a matter of

availability (Grubb and Hensel 1978). Bald Ea

gles in coastal regions of the Pacific Northwest

frequent seabird nesting colonies and Harbor

Seal (Phoca vitulina) haulout sites where they prey on eggs, adult seabirds, juvenile birds,

seal afterbirths, and scavenge dead seal pups

(Hayward and others 1977; Degrange and Nel son 1982; Thompson 1989; Parrish and others 2001; Galusha and Hayward 2002).

During the 1993-1995 breeding seasons, Gal

usha and Hayward (2002) observed Bald Ea

gles feeding on seal afterbirths and dead seal

pups on Violet Point, Protection Island, Wash

ington. They reported seeing eagles "standing

near pups that appeared sickly'' but never saw

eagles disturb live pups. Here I report 1 in stance of predation and 2 instances of attempt ed predation on live seal pups on Protection Is

land in 1998, 2000, and 2001. All 3 observations were made through a 20x-60x spotting scope from a high bluff above the west end of Violet Point. To my knowledge, these are the first re

ported instances of predatory behavior by Bald

Eagles on Harbor Seals.

At 14:15 on 12 August 1998, a pup on the south beach of Violet Point appeared ill and weak. An adult eagle had stood within a few meters of the pup for at least 1 h. Several times over a 30-min period, the eagle placed a talon on the pup's head and hopped on top of the

pup's back and head and struck the pup with its bill. The pup responded with a vigorous flexing of its body. The eagle began taking bits of flesh, at times flapping its wings to maintain balance on the pup. Intermittently for 15 min

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52 NORTHWESTERN NATURALIST 90(1)

the pup continued to flex its body, but its re

sponses became progressively weaker. The ea

gle began taking larger pieces of flesh from the head and the flexing stopped.

At 12:10 on 19 July 2000, a juvenile eagle stood beside an apparently healthy seal pup high on the north beach of Violet Point at low tide. The pup moved toward the water and the

eagle followed. When the pup stopped, the ea

gle walked around the pup and moved its head toward the pup's hindquarters. The pup re

sponded by lunging toward the eagle, which

jumped back. The pup then continued to move toward the water and the eagle followed. At one point the eagle contacted the pup's hind

quarters with its talon and the pup quickly turned toward the eagle, which jumped back.

At 13:41, the pup entered the water and swam

away. At 19:30 on 14 June 2001, a seal pup was born

on the north beach of Violet Point. One juvenile and 2 adult eagles devoured the afterbirth. At

21:20, the apparently healthy pup, with part of its umbilicus still attached, was alone on the

beach. An adult eagle landed and hit the pup with its talon. The pup recoiled from the blow. The eagle looked down at the pup, covered the

pup's head with its talon and squeezed. The

pup jerked away and the eagle retracted its tal on. The eagle continued to reach toward the

pup with its talon and twice flew up over the

pup as if to alight. For the first few minutes the

pup remained close to the eagle and even

moved toward it. Eventually, however, the pup, with mouth wide open, lunged toward the ea

gle, which backed away. At 21:27, the pup be

gan to move toward the water. The eagle re

sponded by repeatedly flying up and alighting on the pup's back. Even after the pup was com

pletely submerged, the eagle held on to the pup until the eagle's legs were nearly covered by water. At that point the eagle released the pup, which swam to deeper water.

From June to August, during seal pupping season on Protection Island, eagles frequently feed on dead seal pups. The proportion of pups actually killed by eagles is unknown, but tem

porarily or permanently abandoned pups often

are seen along beaches in the region and are

vulnerable to eagle predation. If an eagle ap

proaches a pup close to its mother, however, the

mother chases the eagle away (Kroll 1993; Gal usha and Hayward 2002).

A somewhat analogous situation occurs on

Amchitka Island, Alaska, where Bald Eagles feed on Sea Otter (Enhydra lutris) carcasses. Ea

gles there also have been observed flying with live Sea Otter pups in their talons (Sherrod and others 1975), although this would be an impos sible feat with the much larger Harbor Seal

pups. The presence of hematomas around al

most all the puncture wounds of dead Sea Otter

pups on Amchitka suggests that eagle preda tion on otter pups is common (Sherrod and oth

ers 1976). Golden Eagles (Aquila chrysaetos), Crowned Eagles (Strephanoaetus coronatus), and

members of other eagle species prey on mam

mals as large as reindeer fawns and antelope

(Tjernberg 1981; Skorupa 1989; Norberg and others 2006; Johnsen and others 2007).

Between 1980 and 1998, numbers of nesting Bald Eagle pairs in Washington increased at a mean rate of 10.1%/y. The largest concentra

tion of these birds occurs in the Salish Sea re

gion of northwestern Washington (Watson and

others 2002). During this same time interval,

numbers of Harbor Seals also increased in

Washington (Jeffries and others 2003). Now that both Bald Eagle and Harbor Seal numbers are high, predatory behavior by eagles on seal

pups may be relatively commonplace.

Acknowledgments.?We thank the US Fish and

Wildlife Service for permission to work on Protection

Island, Joe Galusha and Rosario Beach Marine Sta

tion of Walla Walla University for logistical support, Andrews University for faculty grant support, and

Shandelle Henson for comments on the manuscript.

Literature Cited

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Galusha JG, Hayward JL. 2002. Bald eagle activity at a gull colony and seal rookery on Protection Is

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Spring 2009 General Notes

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harbor seals, Phoca vitulina, during the breeding season at Protection Island, Washington [thesis].

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Biology Department, Andrews University, Berrien

Springs, Michigan 49104 USA. Submitted 12 Sep tember 2008, accepted 20 November 2008. Corre

sponding Editor: Clayton Apps.

NORTHWESTERN NATURALIST 90:53-55 Spring 2009

KLEPTOPARASITISM OF A COYOTE (CAMS LATRANS) BY A GOLDEN EAGLE (AQUILA CHRYSAETOS) IN

NORTHWESTERN CANADA

Thomas S Jung, Kristoffer T Everatt, and Leah M Andresen-Everatt

Key words: kleptoparasitism, interference

competition, Golden Eagle, Aquila chrysaetos,

Coyote, Canis latrans, Yukon

Most kleptoparasitism by raptors occurs on

other birds, whereas incidents of birds stealing food from mammals has rarely been reported

(Brockmann and Barnard 1979). Bald Eagles (Haliaeetus leucocephalus) and Golden Eagles (Aquila chrysaetos) are well known for stealing food from other birds, but not mammalian car

nivores (Brockmann and Barnard 1979). In one

rare report, Watt and others (1995) occasionally observed Bald Eagles stealing prey from Sea Otters (Enhydra lutris) in coastal Alaska, but noted that it was rare despite the numerical

abundance of both species in their study area

and their intensive observations of Sea Otter

foraging. Similar observations are difficult to

find in the literature. Here, we report an obser

vation of a Golden Eagle stealing a dead Snow

shoe Hare (Lepus americanus) from a Coyote

(Canis lair ans). Our observation occurred in Takhini Valley,

a broad semi-arid river valley bisected by the Alaska Highway immediately north of the Coast Mountains in southwestern Yukon, Can

ada. The area where our observation occurred

is comprised mostly of open-canopy stands of

boreal mixed-wood, with an overstory domi

nated by mature White Spruce (Picea glauca) and Trembling Aspen (Populus tremulodies), and an understory dominated by graminoids and herbs. Much of the valley, however, burned in

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