Molehill Mayhem A literature review on endogenous and exogenous mechanisms influencing activity in Talpa europaea and possible implications for future mole control measures
Bois, T.M.E. du
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Moles (Talpa europaea) largely go unnoticed as they live most of their lives in the subterranean. However, they are often perceived as a pest mammal because of their destructive digging activities. Shallow shafts and molehills may not only cause damage to aesthetics of gardens and golf courses, the heaps of dirt may also cause serious damage to agricultural equipment and crops. Fortunately, there are currently several methods available to control moles. The downside of these methods is that they are often found to be inhumane and the cost effectiveness is not always optimal. In order to control moles more effectively and use more animal friendly methods, it is important that more insight is gained in factors influencing activity. Therefore the main goal of this study is to assess how endogenous and exogenous mechanisms may influence mole activity and occurrence. The main findings are listed below: • Circadian rhythm: There is evidence that under some circumstances, mole activity follows a 24h rhythm. Available literature shows that mole activity is not random or solemnly revolved around external cues. It is shown that during periods in which food is not limiting (i.e. spring and autumn), mole activity may be orderly arranged over a 24h cycle. However, when environmental changes occur, the cycle becomes quickly more distorted. It remains therefore questionable to what extent daily activity under natural conditions is dictated by this, apparently fragile, 24h cycle. • Mating season: Literature shows that mole activity during spring may increase as a consequence of male moles that go in search of receptive females. However, predictability of the increased activity remains uncertain on mole level; it is believed that individual male moles will increase digging activity only for several days at the most. To conclude, when combining the information on circadian rhythm and activity during mating season it appears reasonable to assume that mole activity (and thus soil disturbance) is more pronounced during spring compared to other seasons. • Habitat preference: Although moles are often believed to be rather indifferent to the habitat in which it occurs, recent research has shown otherwise. The available literature suggests that mole occurrence in arable fields is made possible by the quality of field margins. If field margins are somehow less suitable for moles, mole occurrence in arable field is reduced as well. • Food availability: It is shown that moles are indirectly susceptible for changes in habitat. Earthworms are relatively susceptible for changes in soil types and soil conditions. If for some reason soils become unsuitable for earthworms, or unsuitable for certain species of earthworms, mole occurrence and mole activity tends to diminish as well. Particularly effective appear to be acid soils and certain grass species that are little nutritious and degrade slowly. The second goal of this study is to use the information gathered in the literature study to investigate the possibilities to improve effectiveness and increase animal-friendliness in mole control. Provided that more elaborate research is done, the findings in this study suggest that there are several non-lethal ways in which mole control can potentially be improved or cost effectiveness increased. For instance, trapping rate may increase if (live-) traps are set during periods when mole activity is generally higher (i.e. during spring). Also, literature suggests that manipulation of field margins may be a powerful tool in mole control in arable fields as it is both effective and easy manageable; desired effects may be realized by simply altering aspects of habitat such as grass species or acidity of soil.