Diets of Norway Rats, Rattus norvegicus, on Langara Island, Queen Charlotte Islands, British Columbia: Implications for conservation of breeding seabirds
Mc. Drever et As. Harestad, Diets of Norway Rats, Rattus norvegicus, on Langara Island, Queen Charlotte Islands, British Columbia: Implications for conservation of breeding seabirds, CAN FIELD-N, 112(4), 1998, pp. 676-683
Diets of introduced Norway Rats (Rattus norvegicus) on Langara Island, Quee
n Charlotte Islands (Haida Gwaii), British Columbia, were investigated in M
ay-June 1995 to evaluate the role of rats as predators of breeding Ancient
Murrelets (Synthliboramphus antiquus). We examined the contents of 80 stoma
chs collected from rats trapped in three areas of the island. Items occurri
ng in high percent volumes (> 50%) and with highest frequency included plan
t shoots, Salal berries (Gaultheria shallon), amphipods (Arthropoda: Amphip
oda), and tissues of Ancient Murrelets. Occurrence and volume of each food
type varied positively with their apparent availability on the island. Rats
near the coast fed primarily on marine invertebrates, fruits and seeds, wh
ereas rats in interior habitats fed primarily on terrestrial invertebrates
and plant shoots. Tissues of Ancient Murrelets occurred with highest freque
ncy (53% of stomachs examined, n = 19) and volume (mean percent volume of s
tomach: mean = 41 +/- 11% (SE) in diets of rats trapped in the Ancient Murr
elet colony. Along with previous findings of dead adult Ancient Murrelets e
xhibiting wounds typical of rat predation on seabirds, and murrelet bones f
ound in almost 30% of breeding murrelet burrows, this study implicates intr
oduced Norway Rats as important predators of Ancient Murrelets.