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MOLES OF BROOK MEADOW

THURSDAY 10 FEBRUARY, 2005

Molehills

Molehills are springing up everywhere in Brook Meadow. Gardeners would be dismayed if this happened on their treasured lawn, but in Brook Meadow they are a welcome indication of the health of one of our mammals. Yesterday I actually watched a molehill being formed near the signcase at the south gate. I waited for a mole to emerge, but nothing happened. They are, in fact, rarely seen on the surface of the ground where they would be easy prey for predators.

This is a highly active season for moles when tunnel systems are being enlarged in preparation for the breeding season. The tunnel system, which is the permanent habitation of the mole, acts as a food trap, constantly collecting invertebrate prey such as earthworms and insect larvae. As they move through the soil, invertebrates fall into the mole run and often do not escape before being detected by the patrolling resident.

Although moles dig actively throughout the year once a mole has established its burrow system, there may be little evidence above ground of its presence. The exceptions to this are the onset of the breeding season, when males greatly extend their tunnels, and during periods of cold weather. Thus fresh mole-hills are commonly seen during periods of frost and snow, which we witnessed on Brook Meadow recently.

 

Molehills survey

I decided to do another count of the molehills on Brook Meadow as a follow-up to the count I conducted on 7 January when I counted a total of 528 with 216 in the North Meadow, 274 in the Centre Meadow and 38 in the South Meadow. This time I also plotted the main clusters of molehills on a map of Brook Meadow. These were fairly clearly defined groups of molehills with gaps between the groups with no hills. The results were as follows.

North Meadow: 10 clusters, 120, 30, 20, 40, 60, 130, 120, 40, 10, 20. Total = 590.

Centre Meadow: 5 clusters, 90, 50, 120, 100, 10. Total = 390.

South Meadow: 4 clusters, 10, 30, 20, 10. Total = 70.

Two areas of woodland were not counted last time.

Palmer's Road Copse 1 cluster, 10. Total = 10.

Lumley Road copse: 1 cluster, 50. Total = 50.

There were none on the Seagull Lane patch.

Grand total for Brook Meadow = 1,110 in 21 clusters.

Map of Brook Meadow showing the clusters of molehills

This represents a doubling of molehills from the previous count, clearly indicating an increase in mole tunnelling activity with the onset of the breeding season. There was also some indication of one or two of the large molehills, called "fortresses" , which moles build over a nest site. One on the east side of the Centre Meadow measured 120cm across.

Very large Molehill (120cm across) on Brook Meadow - 10.02.05

 

 How many moles are there on Brook Meadow?

There appears to be no simple formula for calculating the mole population from the number of molehills. I have looked in books by David Stone and searched the internet in vain. The problem is that moles vary in their activty and in the number of hills they produce. However, let us assume each cluster of molehills in the present survey represents one mole's activity then we could have 21 active moles on the Brook Meadow site. In fact, this figure could be higher, since mole territories overlap and there could be more than one mole per cluster of molehills.

This calculation fits reasonably well with the density figures provided by R David Stone in "The Mole", Shire Natural History. He gives 3,000 square metres for males (rising to 7,000 square metres in the breeding season) and about 2,000 square metres for females. The Brook Meadow site covers roughly 45,000 square metres which would, in theory, give 20 moles 2,250 square metres each. Since territories overlap, this figure is probably too low.