Sunday, 27 October 2013

CaRT going Ratty?

In a press release from CaRT 'Help us protect water voles' which you can view here. Click Me CaRT are seeking a donation around £25,000. On the face of it, the project seems to be quite laudable. However, there is a caveat. Such a project needs two things if it is to prove successful. The first is that it has to be an open ended project. It's never going to be successful as a short term project. It has to have a plan for the long term future built in. This is going to require money year on year for the foreseeable future. The second problem is one for the voles and the conservationists. North American Mink  are now more widespread than ever. 

I worked as a volunteer on a wildlife reserve (250 acres, which has since been doubled in size) which was bordered on one side by a river. The reserve had a small population of water voles. When mink started to turn up on the reserve, the voles and large numbers of chicks were soon wiped out. We started trapping Mink, and we were getting 1 or 2 every day. The numbers started to drop after a while to 2 or 3 a month. Then a family of foxes moved into an artificially created Otter halt and soon afterwards a second family of foxes arrived within the same area. The numbers of mink trapped fell further. I think this was due to territorial pressure more than anything else. 
The mink have to be constantly controlled for a period of time before re-introduction of voles. The pressure on the control of mink has to be kept up constantly afterwards. We knew we were winning when we stopped catching young mink (even at the end of the breeding season) and only trapping adults that were moving into the area. The chick mortality fell drastically, but the voles have never naturally recolonised. Mink will travel along any water course and will cross open land quite happily at night. With no top predator to keep them in check trapping is the only way.

The Water Vole Steering Group published more than a decade ago 'Without strategic mink control being carried out in combination with habitat enhancement, we will lose the water vole from the vast majority of the British countryside in our working lifetimes.' I hate to say it - but that is exactly what has come to pass.

It's known that Otter numbers are on the increase naturally and through reintroduction. There is some crossover in habitat and food sources between the two species. I suspect that the Otter is a formidable opponent to the opportunistic Mink, but I suspect that its habitat pressure because both are territorial. Rather than one being a predator on the other that makes the difference. However, the mink continues to spread further and further north and the change in habitat is closer to its natural habitat range. Mink are at home in more climates than most mammalian predators on the globe.

Mink have been living and breeding in the wild since the 1930's. They have gained a real foothold since the 50's. Nationally there is very little in the way of effective control measures other than advice being offered. So its down to localised control to protect specific areas. Wild life sanctuaries with on-site wardens, river keepers and game such as Pheasant and the associated gamekeeper come to mind.

There have been ideas floating around such as developing a virus that targets Mink.  Similar to Myxomatosis, a disease that affects rabbits. That idea seems to have dropped out of favour. I shudder at the thought of reverting to such drastic measures. Which I think is just as bad as some other ideas such as introducing non native insects to control other alien species such as Japanese Knot Weed.

The little lovable vole was immortalised for ever by the misnamed character of 'Ratty' in The Wind in the Willows. Somehow if a toad can drive a car. Why not a Water Vole in a boat with an outboard motor.

On a slightly more serious note, I found this quote from Alastair Driver, Environment Agency national conservation manager and chairman of the UK water vole steering group. He said: 'Creating new habitat helps protect our native species, like water voles and otters, and helps tackle climate change. The Environment Agency has created nearly 5,000 hectares of wetland and river habitats in the last 10 years and we hope to double this in the next 10. Added to this, our rivers are at their healthiest for over 200 years, but control of the American mink is essential if water voles are to benefit from these healthier rivers and new habitats.'
Mink are strictly carnivorous, preying on a wide variety wildlife. Mink love the water and much of their prey can be found in and around water. The mink's diet includes fish, shellfish, crayfish, frogs, snakes, large insects, small rodents, rabbits, rats, waterfowl, upland birds and eggs. Mink will also feed on carrion but prefer fresh kills. Mink will prey on animals much larger than themselves, latching on to anything they can get their jaws locked on to. Birds as large as geese are occasional victims.

Part of the problem is that mink love the thrill of the kill and will hunt for sport, killing far more than they could ever consume.

Mink prefer to hunt in familiar territories around 3 miles long. These territories  hug water systems and natural drainage channels. Mink don’t have permanent dens, the only time they den up for more than a day or two is when they raise young in the late spring and early summer. Most of the year mink are on the move, spending up to half of their time in the water probing every little hole in the bank in search of prey. Mink hunt day and night, usually resting only after they have made a kill. Mink will often spend time in the dens of their prey while they feed on the carcass of the last tenant. While mink can be seen crossing expanses of land far from water, creeks and rivers are the mink's favourite areas. Mink have no natural predators and have a fierce, aggressive style of defence.

Questions that still need answering include: ‘How much control of mink numbers is needed to preserve biodiversity?’ and ‘How much control is actually possible and sustainable?' As well as 'what will it cost year on year?’

Everyone knows that leaving the mink uncontrolled, in a reintroduction, is in reality just providing water voles as a small snack for the mink. Spending money on re-introducing voles and providing habitat without maintaining the habitat and controlling mink is a waste of time, effort and money.

There is some evidence that the reintroduction of Otters can also help to reduce mink numbers within an area. Click Me Once again, I think this was due to territorial pressure as much as anything else. But if CaRT were to spend the money on habitat creation and  introducing Otters. Then I could see a much more positive outcome for water vole reintroduction  than the existing plan.

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