虎鲸对鳐鱼的猎食

虎鲸对鲨鱼的猎食

包括姥鲨， 双髻鲨， 礁鲨， 灰鳍鲨，柠檬鲨，蓝鲨，鲸鲨，白真鲨。

附加一则捕食目击报告
在场分别有A B C 以及一头幼崽，虎鲸A，B被认为6~7m长,C为5m
被杀的鲨鱼约1.5m，可能是柠檬鲨或牛鲨，该鲨鱼被认为先被虎鲸A杀死，而后被其他3条撕碎而后食用。
Killer whales (Orcinus orca) consume a large variety of prey: marine mammals,
fishes, seabirds, sea turtles, and cephalopods (e.g., reviews provided by
Martinez and Klinghammer 1970, Hoyt 1984, Perrin 1982, Jefferson et dl.
1991). However, elasmobranchs (sharks, skates, and rays) are found infrequently
in killer whale stomachs (Castello 1977), and few observations of killer
whale predation on elasmobranchs have been reported. We present an account
of a killer whale attack on an unidentified carcharhinid shark and a review of
killer whale predation on sharks and other elasmobranchs.
On 2 May 1992 at 0815, a group of four killer whales was sighted .4 km
from the mouth of Golfo Dulce (8
83
in the Pacific region of
southern Costa Rica. The sighting was made incidental to a study of bottlenose
dolphin (Tursiops truncatus) ecology in the area. Sunny weather with a Beaufort
sea state of 1 facilitated detailed observations of the event. The killer whales
were observed from a 5-m inflatable boat for one hour and were recorded on
8-mm video tape and 35-m***ide film. From their size relative to the observation
platform, the group was determined to consist of three subadult
males or adult females (whales A and B were an estimated 6-7 m long, whale
C was about 5 m) and one calf (about 3 m). Individuals were identified by
saddle patches and natural markings on their dorsal fins (Bigg 1982). Whale
A and the calf had an undetermined number of cirriped barnacles Xenobalanus
sp. attached to their dorsal fins, making for easy identification.
The whales were first observed milling within 10 m of each other, making
short duration dives (< 30 set) with rapid turns that created surface
foam. Although the whales, at that time, were not observed carrying anything
in their mouths, one female magnificent frigate bird (Fregata magnificens)
was seen dipping within 10 m of the whales. At 0819 whale A wasobserved holding a fresh, entire shark (about 1.5 m in length) in its mouth.
At 0826, whale A was observed carrying a mutilated portion of the shark.
At this time, the calf moved to whale A’s side and dove while whale A
remained at the surface. Twenty seconds later whale A was observed holding
a noticeably smaller portion of the shark. At 0829 the calf was observed
with shreds of shark flesh trailing from its mouth. The whales began a
pattern of separating (by as much as 50 m) and rejoining (< 10 m apart).
In this milling pattern the calf remained within 10 m of whale A or B.
The rapid turns at the surface observed earlier no longer occurred. On
several occasions, whale A remained at the surface for 3-5 set, while one
or two of the other three whales dove beneath or around it. Because of the
angle of view, it was not possible to observe the shark at this time. However,


at 0834 whale B was observed to have the posterior third of a shark, presumably
remains of the original one, in its mouth. At 0835 whale B moved
away from the three other whales (milling within 20 m of each other) and
remained more than 100 m from the subgroup. Whale A, which was originally
seen with the shark, had nothing in its jaws at this time. At 0842
whale C was observed for the first time with a portion of shark flesh. At
0846 the milling ended, and the three-whale subgroup moved towards
whale B, which was more than 100 m southwest of them. The whales were
last observed at 0915 approximately 2 km southwest of the location where
they were first encountered.
It is believed that one shark was captured by a single killer whale, presumably
whale A (this whale was the first one seen holding the shark while it was
still fresh and had the longest contact with the prey) and then subsequently
shared and consumed by all members of the group. The shark was determined
to be of the family Carcharhinidae, based on its rounded snout (Castro 1983).
Twelve carcharhinid species have been reported for the Pacific coast of Costa
Rica or neighboring countries (Lopez and Bussing 1982). It was not possible
to obtain detailed information on the fins of the shark; however, based on a
photograph of the underside of its head, coloration, and body size, it was
determined that the animal was either a bull (Carcharhinus leucas) or a lemon
(Negaprion brevirostris) shark. Blue (Prionace glauca), hammerhead (Sphyrna sp.),
Galapagos (Carcharhinus galapagensis), and an unidentified species of reef shark
were the only carcharhinids that killer whales were previously known to prey
upon (Table 1).
Although killer whales have been studied in many locations worldwide,
in some cases for longer than 20 yr (Bigg 1982), few accounts of killer
whale predation on elasmobranchs have been reported (Table 1). Since most
of these episodes appear to take place in the open ocean, the rarity of reports
may be related to the fact that few behavioral observations of killer whales
are made in those waters. For example, this is the first report of killer whales
in waters close to Costa Rica. Our review supports this line of reasoning
and suggests that elasmobranchs may be taken on more occasions than
originally considered.