2012-02-05
The Zeitgeist, or spirit of the times, draws some people to make assertions which are not borne out by facts but rather prejudice or self-interest. There’s a tendency to present “New Zealand” fur seals as some sort of baddies, with the “Australian” sea lions being the good stuff. Well, these epithets should really be taken with a grain of salt, being more conventional tags than complete geographical descriptions.
There are three species of otarids hanging around Kangaroo Island. Here they are, genus name given then species (and sub-species) name, followed by their vernacular name:
— Neophoca cinerea, the “Australian sea lion”;
— Arctocephales forsteri, the “New Zealand fur seal”;
— Arctocephales pusillus doriferus, the “Australian fur seal”, a sub-species of the South African giant fur seal.
The attribution of a “NZ” tag to A. forsteri does not mean that it’s not a species native to Australia. It just happens to roam the oceans between Australia and New Zealand, while A. pusillus tends to roam the oceans between Australia and South Africa. The former is much more common on KI than the latter.
These three species have not, by far, returned to their original, large numbers before fur-sealers massacred them in the 19th century, and that is true even for the more resilient A. forsteri. In American River, American sealers killed the WHOLE community, to the last puppy, in 1803: this community has still not reconstituted to this day. The notion that seals could be over-eating fish does not stand up scientifically or ethically. That fishermen think they eat too much of “their” fish is a different matter, this is politics, not ecology. Same thing about accusing them of eating little penguins: that’s nature’s way… Penguins eat fish, seals eat penguins, sharks eat seals… And these days, thanks to the seal population returning to its pre-extermination level, some of the seals predators like the false killer-whales (Pseudorca crassidens) can be seen again surfing on the southern coast of the island. Stirring, impressive sight.
Out there, it’s wilderness, not a garden, and it’s normal for animal populations to fluctuate wildly: populations of both preys and predators do not, and cannot, evolve in a linear manner; rather, they coevolve according to the well known Lotka-Volterra model. So there is really no need to get unnecessarily indignant or anxious on these matters of ecology, and calmer and more informed spirits should prevail.
Dr Gabriel Bittar
An edited version was published in The Islander of 2012.02.09
On the same subject, see also
Penguins quite comfortably co-exist with their fury counterparts — Dr McKenzie, Jane, 2012-02-21