My article about the ten biggest threats to angling drew quite a response both here on this web site and on others, too, although you would be forgiven for thinking the entire article was about otters and the other nine categories were erroneous. Perhaps it’s because otters are currently flavour of the month, the threat on the tip of everyone’s tongue.
Sadly you cannot force people to see reason if their head is not for turning, particularly the ones who happen to be most vocal on the various Internet forums. The thing is, if we’re being honest here, these folk will not really be affected by the impact of otters or any other threat as they never catch seem to catch a great deal as it is, preferring to spend much of their life dealing with the complexities of issues like, ‘What’s the best bank stick?’
But let’s look at otters again and draw a parallel with the nearest thing I can compare with the problem, the spread of American mink and the impact this had on the aquatic environment.
Contrary to what many think, mink didn’t become widespread simply because a few loony anti-fur activists went around liberating mink from farms in the 90s. The UK mink population was established in the 1960’s as a result of poor control safeguards on farms that led to escapees becoming established. They’ve been running wild and rampaging through the small mammal population for a good 50 years to the point where our native and once prolific vole population is now threatened with extinction.
Now those who claim that Mother Nature finds a balance, that predators do not eat themselves out of house and home and that otters will ultimately find a balance need to stop dreaming, recognise that the creatures in Walt Disney cartoons aren’t real, then wake up and smell the coffee. This is just one example from a whole catalogue of disasters where an introduced predator has been the cause of some of the most rapid and severe changes in native bird and mammal populations all over the world.
Probably the most notorious example is the introduction of brown tree snakes (Boiga irregularis) to the island of Guam in the Western Pacific Ocean. Within a few decades of the arrival of brown snakes, Guam lost all but three of its thirteen native bird species and several bat and reptile species (Fritts and Rodda 1998).
In Australia, the introduction of cats (Felis catus), red foxes (Vulpes vulpes) and dingos (Canis lupus dingo) is linked to the extinction of several species of mammals, birds and tortoises (Dickman 1996).
If I could be bothered to search through Bill Bryson’s Short History Of Just About Everything I’d be able to highlight an example of a lighthouse keeper’s cat that single-handedly eradicated an entire species of birds from the planet.
Were this theory of balance true then surely after 50 years the numbers of mink in the UK would have fallen to acceptable levels and the vole population would be on the way back to recovery? Of course, it isn’t, and by the time we recognise that otters will have the same negative impact on the UK’s already dwindling wild fish population most of us who are currently voicing protest will have conveniently died. Unfortunately so will most of the fish in our rivers.
Bioligists certainly appreciate that without a long history of coexistence, native prey may not be able to recognise alien predators as dangerous (level 1 naïveté), or they may lack the appropriate anti-predatory responses. The relationship between an introduced predator and a native prey, however, may have several different outcomes (Ebenhard 1988; Dickman 1996). The one most often observed is the severe decimation or extinction of the prey species.
You see, fish don’t think. They react. They do what comes naturally to them. Thousands of years of evolution has taught them to behave in a particular way when threatened but this will not ecessarily provide protection if the native prey responds with tactics which fail to work against the different hunting modes of alien predators and before some clown jumps in and cries the otter is not an alien, please get real. The otter is as alien to many of the waterways it has been introduced to as a little green man from Mars.
During scientific studies removing predators has turned out to be a convenient method for revealing the effects of predation on prey populations (Sih et al. 1985; Korpimäki and Norrdahl 1998; Korpimäki et al. 2002; Korpimäki et al. 2005). Unlike predator exclusion for instance by nets or fences, in predator removal experiments prey populations are not influenced by any other factor than the presence or absence of the predator in question.
Guess what? When the predator is removed the prey population recovers.
Through accidental escapes or deliberate releases mink have become established in semi-aquatic ecosystems of Northern and Eastern Europe, including archipelagos and the British Isles (Bonesi and Palazon 2007). Almost everywhere it has been introduced, the mink has been suspected of having a notable negative impact on some of its prey species. One such case is the dramatic decline of water voles (Arvicola terrestris) in the U.K.
The most obvious effect of mink removal was the generally higher vole densities on mink-free islands compared to islands with mink present (III, Fig. 2, see also Banks et al. 2004), which might have been caused by the naïveté of voles against the alien predator and costly anti-predatory behaviours.
Trapping data from 2004-05 and 2007 suggested, that in two out of three summers densities of voles were significantly higher in the absence of than in the presence of mink. The establishment of colonising field voles in areas with alien mink may therefore fail, leading to the possible extinction of voles.
The biologists also discovered, for the first time, that an alien predator may induce a trophic cascade on small islands. Since alien mink has also been shown to reduce the diversity of breeding bird assemblages in the outer archipelago (Nordström and Korpimäki 2004), alien predation is not only devastating for native prey populations but can have detrimental effects on the diversity of three trophic levels (piscivorous birds, herbivores and plants) of the ecosystem.
Now repeat after me:
Otters are cuddly. Otters are cute. The fish they’re killing are old and deserve what they get. Doesn’t really matter. They’ll settle down and balance out in a year or two. Everything’s gonna be alright…
Everything’s gonna be alright…
Oh, and can someone tell me how and when protected species are removed from the endangered list? If there are 30,000 cormorants in the UK, why do they still require protection? If there are breeding populations of otters in every single county what criteria deems them to be in need of protection?
If you get a mouse in your house, how long do you ignore it? When the numbers multiply to plague proportions do you just think, never mind, I’ll live with the consequences, accept the damage they cause? Do you put up with slugs in your garden? Greenfly? Rats in the sewers? Rabbits eating crops?
Why do we control dangerous dogs? Why don’t we allow dogs to worry sheep and cattle because that’s natural to them? Why do we protect red squirrels and regard grey ones as pests?
And why do we allow sheep, pigs and cattle to be killed for food? Yet don’t eat horses and donkeys. Or dogs. Why do we allow cats to decimate the songbird population?
Why are we not encouraging the re-introduction of wolves to our forests, and bears, and wild boar?
And why are some people so stupid they cannot, or simply refuse to, recognise cause and effect?