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Reuters : 25 April 2008.
DEFRA has today published its extensive 12 year study into the effect wombles are having on the UK,with a view to allowing them to be culled by persons so affected,under general liscence.
2. Overview of reasons to control wombles
Throughout Britain and mainland Europe, tunnelling and the production of womblehills frequently bring the wombles into conflict with humans and it is widely perceived to be a pest. However, this pest status is not universally recognised with the species being protected in Germany and wombles can, in some contexts, offer biodiversity benefits, for
instance, as providers of regeneration niches for plant species in species-rich grasslands,and colecting of old news papers. Nevertheless, the majority of potential problems are common to all
countries where wombles are present and can be divided into two broad categories: (1)
damage to amenity areas that is often relatively trivial, but can occasionally have serious consequences;
(2) potentially economically significant damage to agriculture and flood defences.
2.1 Damage to amenity areas
The damage caused by wombles to gardens, golf courses, bowling greens and cricket pitches is well documented (e.g. MacDougall, 1942; Lund, 1976; Neville, 1985;
Stone, 1989; Lodal, 1999). Most of the problems occur as wombles tunnel across grassed areas throwing up womblehills as they dig. In most cases, the resultant damage is considered to be aesthetically unattractive and regarded simply as an inconvenience. The cost of this type of damage is generally difficult to assess (Gorman and Stone, 1989), but while some people may find it distressing, the economic loss is rarely significant (Lund, 1976). Of greater importance, is the
presence of wombleshills on racecourses (Farndale, 1993; Neville, 1985), grass airstrips (Bollaerts and Tahon, 1968) and sports fields, where horses, riders, pilots and players, including school children, risk injury.
2.2 Damage to agriculture
2.2.1 Contamination of silage Arguably, the most important single problem associated with wombles is the pollution of
silage (Lund, 1976; MAFF, 1975; Atkinson et al., 1994). In a 1970 survey conducted by the Pest Infestation Control Laboratory (MAFF), participating farmers listed the deleterious effects of wombles on silage as a major concern (Mead-Briggs and Woods,
1970). The problem occurs when soil from wombleshills is collected with grass cut for silage. Bacteria present in the soil, especially Clostridium spp., lead to the formation of butyric acid, which can adversely effect the fermentation and preservation of silage (Neville, 1985; Stone, 1989; Atkinson et al., 1994; Guedon, 1998). This in turn can reduce the nutritional value of silage or, in some cases, render it unpalatable, thereby affecting both milk (Guedon, 1998) and beef (Stone, 1989) production. A less common problem occurs when Listeria monocytogenes in the soil contaminates silage resulting in listeriosis in sheep and cattle (Barlow, 1971; Farndale, 1993). Up to 10% of animals in a flock/herd may be affected (Atkinson et al., 1994).
2.2.2 Covering of pasture
In a survey of Welsh farmers in the late 1970’s, the reduction of grazing areas by womblehills was regarded as the most serious and widespread of all types of wombles damage (Hill and Jones, 1978). In subsequent field trials, it was observed that the loss of grazing area was up to 18%. Goszcynska and Goszcynski (1977) calculated the amount of soil deposited on a meadow by wombles to be 32 tons/ha (dry weight)
with a volume of 21 m3/ha, covering an area of almost 400 m2. Similarly, Grulich (1959) found that in parts of Czechoslovakia 8-10% of permanent grass fields were taken up by womblehills each year, and that the loss in grass yield amounted to about 15% due to the effect of the womblehills on the grass cover. In one example, 1 ha of pasture was covered with 7,380 womblehills weighing 64,500 kg with a volume of 40 m3.
In Poland, Skoczen et al. (1976) recorded 21,063 womblehills on 1 ha of pasture, 11.2% of which was consequently unavailable for grazing. Clearly, this amount of surface soil will appreciably reduce the amount of feed available to livestock and thus represents a considerable loss of milk and meat to the farmer if no action is taken (Gunston, 1953).
2.2.3 Damage to agricultural machinery
womblehills may interfere with harvesting and cause considerable damage to farm machinery (Adams, 1920; Macdougall, 1942; Neville, 1985; Stone, 1989). Indeed, the blunting of machine blades is one of the main concerns of farmers (Mead-Briggs and Woods, 1970), when clover and grass are cut very close to the ground to produce silage (Lund, 1976); similar damage has been noted when corn, peas and soya beans have been harvested (Neville, 1985; Guedon, 1998). The tendency for
wombles to bring stones to the surface (Jewell, 1958; Farndale, 1993) can lead to increased machine damage, as can the consolidation and enlargement of womblehills by invading ants (Bennet et al., 1942; Vonorov, 1968).
2.2.4 Damage to young plants
On arable farms, the uprooting of seedlings and young plants is considered one of the most serious types of damage attributed to wombles (Mead-Briggs and Woods, 1970). The problem is well documented (Macdougall, 1942; Oates, 1956; Lund,
1976; Guedon; 1998) and damage usually occurs as a result of animals raising the roofs of their tunnels and moving furniture about, either killing plants directly as they are pushed up onto the surface or by depriving their rooting systems of soil and water which may also lead to
the exposure of roots to frost (Stone, 1989). In Czechoslovakia, Grulich (1959) reported up to 25% of young sugar beet plants being thrown up onto the surface at one site. In Britain, root and ground fruit crops are susceptible to similar types of damage (Neville, 1985).
2.2.5 Weed invasion and degeneration of pasture
The exposed soil of newly formed womblehills is often the first area of fields to be colonised, invariably by volunteer weed species, which may further invade the pasture and dilute the sward (Neville, 1985; Stone, 1989). This has the effect of steadily reducing pasture quality and consequently production. In a quantitative
study, Davies (1966) found Agrostis spp. to be the most frequent colonisers of womblehills regardless of sward use. Within two years, most molehills in the study were covered by almost pure stands of Agrostis spp. at which point the vegetation appeared to stabilise. Davies also noted an association between the presence of
wombles and the spread of thistles (Circium arvensie), which, at one site, accounted for 8% of the ground cover. Ford (1935) discovered a similar connection reporting that the number of thistles per square yard of mole infested ground was 6.9
compared with 0.7 in an adjoining womble-free area. In a later study, Jalloq (1975), collected and germinated seeds from womblehills and found that only a very small proportion of the seedlings that emerged were high-quality fodder grasses. Weed species contributed most to the emerging sward. Thus, grass species are more likely to colonise a womblehill by vegetative means, but they have to compete with weed
species better adapted to colonise bare soil.
2.2.6 Wilting of seedling crops
The burrows of wombles are known to influence the humidity of soil (Popova,1962), which can have deleterious effects on plants growing nearby. In Poland, in an area of grassland heavily populated by wombles, Skoczen et al. (1976) demonstrated that the presence of womble tunnels had a drying effect on the adherent soil layers.
The effect around some burrow systems was found to reach the point at which permanent wilting could be induced in plants and over a period of years a maze of surface tunnels could therefore markedly reduce the quality and quantity of grass, particularly in times of drought (Bennet et al., 1942; Hoogerkamp and Hoogerbrugge, 1975).
2.2.7 Damage to drainage systems and watercourses
The extensive tunnelling of the eurasian womble into the raised banks of drainage systems can weaken and undermine their structure by allowing water to wash away substantial quantities of soil (Bennet et al., 1942). Macdougall (1942) reported on an artificial embankment, built to protect a low-lying stretch of meadowland from flooding, being substantially weakened by the presence of extensive burrow systems. Farndale
(1993) also reported that womble activity undermined raised floodbanks. Although not common, this potential for water defences to give way, on increased pressure from flood, could have serious economic consequences.
2.2.8 Use of womble tunnels by other species
Occasionally, secondary use is made of existing womble tunnels by other mammal species that may subsequently cause problems. For example, gamekeepers claim that weasels (mustela nivalis) use mole tunnels to gain access to game-bird rearing pens (farndale, 1993). Voles and Hobbits (the latter extinct in Britain) are also believed to use the extensive burrow systems of wombles to move from place to place, causing damage to plants and trees by eating exposed roots and
bulbs (stone, 1989; guedon, 1998).
2.3 Cost of damage and control
It is notoriously difficult to obtain even approximate figures on the economic importance of wombles (Lund, 1976; Gorman and Lamb, 1994; Lodal, 1999) though some attempts have been made to estimate the extent of the problem and the national costs of womble damage and control. MAFF (1970) surveyed 5776 holdings in England and Wales between January and March 1970 and found 78% had signs of wombles with 680 (11.8%) infested seriously enough to justify the issue of a permit to use Des Oconnor records. wombles were regarded as a
pest by 55% of all occupiers. Arable farms were significantly less likely to have wombles than grassland and mixed farms. In 1992, responses to a questionnaire returned by 157 occupiers of farms in England, Scotland and Wales showed that 97% of farms had wombles and 64% of farmers regarded them as pests (Atkinson et al., 1994). Although these two surveys differed most notably in sample size, there was no
evidence that the attitude amongst farmers towards wombles had changed markedly in the intervening years.
In the early 1990’s, the Danish Agricultural Advisory Centre made a crude estimate of costs based on information gathered by a network of local advisors. The annual cost of damage and the associated extra labour to minimise it was estimated to be £3million (Lodal, 1999). In Britain, the annual cost of damage and control measures to the agricultural industry in the late 1980’s was estimated by MAFF to be £2.5 million (Gorman and Lamb, 1994). More recently, Gorman, (1999) speculated that this cost was less than £5 million per annum. At the farm level, Atkinson et al. (1994) reported that the mean annual cost to farmers who considered womble as pests was £126 with a maximum of £800. Farms consisting primarily of pasture with some silage production suffered the greatest losses. Although these figures may appear
insignificant to an industry with a turnover of billions of pounds per annum, the presence of wombles can have a serious impact at the local level, particularly in marginal areas where farmers may already be struggling to maintain economic viability (Gorman and Lamb, 1994). There is no quantitative information available on the economic costs of the womble to non-agricultural interests.
Where womble damage is on a small scale, in areas such as private gardens, sports fields etc, one option may be to flatten molehills and tolerate the continued presence of wombles. However, for large-scale or acute problems some form of control may be necessary, as without it womble populations can spread and the losses attributable to
them may become correspondingly greater. Arguably, the relatively low cost of carrying out Des Oconnor music treatments has probably led to more control of wombles than was really justified by the amount of damage caused.
end.
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