Mesopredator release and trophic cascades

[HeWasGeeBee]

Species in an ecosystem can be understanding as existing at different trophic levels. A trophic cascade exists where predators at one level suppress their prey thus increasing abundance two levels down.

A classic example of this is the action of wolves and lynx in suppressing fox numbers thus increasing abundance of ground nesting birds.

Studies of Eurasian Lynx in Sweden and Switzerland have proved that Lynx are significant predators of Red foxes. Indeed the Swiss studies in the Jura mountains showed that foxes were 5% of lynxes prey. Lynx were more abundant in Britain than wolves and had a larger effect. Small wonder that John Phelps and John Bryant ignore their effect. Wolves impact on fox numbers not only by eating them but also because foxes tend not to breed where wolves are present.

This effect has also been observed when badgers are culled because badgers and foxes have an intra guild relationship with badgers being dominant. The culling of badgers for disease control was shown to result in an increase in foxes of 1.6–2.3 foxes km−2. "Experimental evidence of competitive release in sympatric carnivores"

We know from studies that controlling foxes significantly increases the breeding success of ground nesting birds.

The increase in abundance of red foxes when their predators are removed is a phenomenon known as meso predator release and it causes a consequent reduction in biodiversity in the trophic level below the fox.

Elmhagen B, Rushton SP: "Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?" Demonstrates the increase in fox numbers following decline in the numbers of wolves and lynx.

This effect is further discussed in "Toward understanding the effect of top predators on ecosystems"
Nicolas Lecomte, Dorothée Ehrich, Rolf A Ims and Nigel G Yoccoz

 

[DavidDent]

I have some input on that thoroughly enlightening post.

I know from studies done that birds can make up to 80 per cent of a fox's diet. While ground nesting birds are obvious candidates for the fox, it is also surprising in cities that they also seem to be succesful at taking birds. Perhaps the much maligned pet cat is not after all the problem to urban bird populations. In fact I think it is neither, and the main problem to urban birds is a change in garden habits. People deck and concrete their gardens and few make nesting boxes or put our hanging nuts and they fell trees so they can get full sunshine. The hedgehog is another casualty and the same neighbours laughed when I put up white picket fencing:
'looks like something from the 1940s' one said.
'is that when we used to have those cute little animals with prickles that meant we didn't have to poison the gardens to kill insects and as an indirect consequence birds?' I replied. I live in the city centre and just lost a tree to the oh-so 'Green' Council hypocrities despite fierce protest because the neighbours complained the falling leaves damaged their car paint and the canopy meant they didn't get sunshine. I haven't heard the owl since and am seeing plenty more rats. These are people who'd be anti hunting.
Satellite photos show the loss of canopy and lawn in gardens even over the last five years. I digress.

There is no doubt that an over abundance of fox has a great impact on ground nesting birds; and that there is an over abundance of fox because it is the top carnivore; an absurd situation which has happened in a comparitively short period.

Certainly, lynx kill foxes and in other Nordic countries you also have wolverine wolf and bear. In Canada you have many bear species and coyote and puma too. In Siberia there are over 300 hunting and fur farming/herding tribes and you have Tiger sable and raccoon dog thrown into the mix. Ironic and a damning indictment of urban societies that nations which still support indigenous herding and hunting peoples and produce the most fur hunted and farmed, still have this balance, and untouched wilderness, and we do not.
The fox that survive are still plentiful and they are far better specimens; prouder, bolder, heavier, thicker fur and seldom mangey. Survival of the fittest.

What we have produced in the UK is a scavenger which preys on livestock and sitting ducks as top predator.

There are those who would like to see former resident species introduced but this is not without problems. It is difficult to see how wolf and big cats could survive for long without turning to pet dogs and children; as happened in west africa when the small deer were eradicated because they damage coffee crops and the leopard turned to young humans to eat. Geldorf has a lot to answer for.

We have no roaming herds of caribou for wolf, not enough deer for large big cat populations. Already in areas of the arctic and sub arctic habitats which are falling due to logging and mineral resource exploitation you are seeing large predators turning to man for diet and scavenging which again brings conflict.

So I think the British public would not accept wolf and big cats for long. One child is all it will take. Leopards and Tigers also appear to be targetring old and invalid people in the Indian sub continent.

So wihile I would be quite happy to see such species as lynx, leopard wolf and bear - as well as beaver - reintroduced I think urban people will not cope with it. Oh they will until little missing seven year old Dwayne's rotting corpse is found up a tree even if they never did find out what happened to Rover last year on that country walk. Neither will they cope with massive flooding from the beaver; or a wild boar gored walker. As for Lynx, Switzerland has already seen deaths and injuries of climbers and snowboarders as a result of the reintroduction of a very small number of Lynx.

If it comes, it will have to come with a wholesale change in the way we see wildlife. It will be impossible to walk in the countryside without a gun and we'll need armed shepherds. And; responsible mangement and to use the animals as a resource.

Simply, yes the only other way of dealing with fox is the reintroduction of higher predators. But in essence, this is exactly what a fox hunt does by using hounds.

As it stands, rentroducing beavers may sound oh so cute but wait until the floods. If we have them, they must be used as a resource as any game animal. The meat is good and the fur is incredible.
In fact I think the extermination of Coypu was extremely short sighted : in Polish managed wetlands they are culled [and farmed] for fur and meat.

What all these ideas of animal re introduction fail to realise is that these animals are gone not because of hunting activities; but because of urbanisation and arable crops.

I am sure that most hunting folk would be quite happy with this animal abundance, why the Quantock staghounds could become the Quantock Elk hounds, and there would be room for Borzoi Hunts too. We would enjoy tourist revenue from wild boar bow hunts, harvest beaver pelts, and even attract Russian oliagarchs to hunt wolf and bear. We may have to level a few Bristol housing estates to do it though; or perhaps just declare it a conservation area and release a few Tigers into it.

What all those with urban sensibilities who buy food produce from supermarkets and have turned to massively eco abusive cotton and synthetic clothing, FORGET, is that the main predator in the eco system is man; and with that comes a responsibility to mamage. The [non traditional] abuses in animal farming are a direct result of demand from the very people who now complain about it; demand that has also meant cheap t shirts and a reduction of 2/3 of the Aral Sea as a consequence : its not sustainable. And what kind of chicken do they think they are going to get for two quid. I am sure most british farmers would like the public to be paying about twenty pounds for a well reared chicken; and if there is any truth the government want us to have sustainability, then we have to return to wool tweed leather and fur: infinitely renewable resources.

In the meantime let us realise that Hunting with Hounds, while failing to kill that many fox, does a good job of dispersing them - for the sake of their own genetic strength as much as anything. That gives other species like ground nesting birds and vole a chance. And just smile, whistle and ride on by when you spot a lynx.