Gulls, Larifdae, are
exceptionally flexible predators found in coastal, inland and open
marine habitats throughout the world. They are highly opportunistic,
typically having diets that alter throughout the year as different
food sources become available, and adapt rapidly to new food sources
when they become available. The Kelp Gull, Larus dominicanus,
is considered particularly flexible even for a Gull, being found
across most of the Southern Hemisphere from the shores of Antarctica
to the southern tropics, and being able to consume a diet that ranges
from small invertebrates to beached Sharks and Whales; there have
even been reports of them attacking surfacing Southern Right Whales
Eubalena australis, tearing chunks of flesh from the Whales
and consuming it.
In a paper published in
the African Journal of Marine Science on 14 August 2015, Austen Gallagher of
the Leonard and Jayne Abess Center for Ecosystem Science and Policy
at the University of Miami, the Rosenstiel School of Marine and Atmospheric Sciences and Beneath the Waves Incorporated, Erica Staaterman
of the Rosenstiel School of Marine and Atmospheric Sciences and
Beneath the Waves Incorporated and Naude Dreyer of Sandwich Harbour 4×4
report the first recorded instance of predation by Kelp Gulls of the
pups of Cape Fur Seals, Arctocephalus pusillus pusillus.
The Seals observed were
at a breeding colony at Pelican Point in the Dorob National Park to
the west of Walvis Bay. This colony was reduced by hunting to under
100 individuals in 1995, but since then the species has been
protected, and a successful ecotourism industry developed, and
between 20 000 and 80 000 individuals can be found at the site each
breeding season.
The Gulls targeted
newborn pups that had strayed from their parents, or older juveniles
that were sleeping, initially attempting to remove and consume the
eyeballs. In about 50% of observed attacks this initial assault was
successful, and followed up by further attacks on other areas of soft
tissue, such as the underside and anus region, invariably leading to
the death of the Seal. In the remaining 50% of instances the Seal was
able to escape, sometimes with the assistance of other Seals.
Eamples of Kelp Gull
predatory behavior on Cape Fur Seals in southern Namibia: (a) Gulls
approach small, weak, or wandering juvenile or newborn Seals; (b)
gulls first target the ocular regions of live or dying Seals; (c)
still-alive Seal pup with its right eye ripped out by a Gull attack.
Naude Dreyer in Gallagher et al.
(2015).
Over the course of 15
years about 500 attacks on Seals by Gulls were observed at Pelican
Point; many more dead Seals were observed with their eyes pecked out,
including newborn pups, juveniles and adults, however Gulls will also
feed on Seals that have died of other causes, with the eyeball being
a preferred item, and have also on occasion been seen feeding on
Seals that have survived Shark attacks but been badly wounded.
Nevertheless the attacks appear to be a new form of behavior, having
not been observed at the site before 1998 and recorded nowhere else
in the shared range of the two species. The behavior has apparently
been driven by the recovery of the Seal colony, which has provided a
new food source for the Gulls in the form of Seal cubs, though the
Gull population has also risen sharply in recent years, which would
be predicted to drive the Gulls to seek novel food sources.
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