204 N O T E S F R O M T H E M A M M A L SOCIETY-NO. 1 8

pleural effusion as a possible sequel to neoplastic diseases of the respiratory system, pneumonia, tuberculosis and mycoses. Primary pleurisy is rare in dogs and is usually secondary to pulmonary or mediastinal infection. Empyaema may follow a bacterial infection of these organs.

The prime symptom of exudative pleuritis (or empyaema) in the dog and cat is usually dyspnoea due to the pressure on the lungs. The coughmg of the fox may be attributed to dyspnoea due to this fluid pressure, to respiratory embarrassment induced by pneumonia and to obstruction of the respiratory tract with mucus. Death was sudden, a phenomenon commonly seen in the cat which may die during clinical examination and manipulation.

Despite the inconclusive histology, there seems little doubt that the fox cub was suffering from pneumonia with exudative pleuritis a sequel. The isolation of Pasteurella multocida may not be particularly significant since this organism is a common inhabitant of the respiratory tract. Smith (1955) examined 111 healthy dogs and obtained cultures of P. multocida from 54% of the tonsils and 10% of the noses. A large number of wild mammals have also been found to carry the organism. P. multocida is therefore a common finding in pneumonia in many species and although sometimes the causal agent, is also a common secondary invader. In this case no other bacteria nor fungi could be isolated but virology was not, unfortunately, attempted.

REFERENCES

Archibald, J. (1959). In Canine Medicine: 178-180. 2nd ed. Preston-Hoskins, H., Lacroix, J. D. & Mayer K. eds.

Smith, J. E. (1955). Studies in Pasteurella septica. I. The occurrence in the nose and tonsils of dogs. J. comp. Path.

Wilkinson, G . T. (1956). Exudative pleurisy in the cat. Vet. Rec. 68: 456457.

Santa Barbara, California: American Veterinary Publications Inc.,

65: 239-245.

M. H. WOODFORD, M.R.C.V.S. Nufield Unit of Tropical Animal Ecology,

P.O. Queen Elizabeth Park, Uganda,

East Africa

J. E. COOPER, M.R.C.V.S., D.T.V.M. Quantocks,

New Wokingham Road, Crowtliorne,

Berksli ire, England

AND

The distribution of badger sets in relation to the geology of the Chilterns

Introduction

It is a widely held assumption that badgers choose well-drained places for their sets. Although this assumption is sensible and is usually borne out by the position of sets we have been able to find only two published distribution surveys of badger sets which include

NOTES F R O M THE M A M M A L SOCIETY-NO. 1 8 205

negative evidence and which relate the location. of sets to the geology of the environment. That of Likhachev (1956) deals with an impermeable loam covered plateau scored with ravines in which sand is exposed; the Wytham Estate survey, Southern & Lynn (1964) concerns an area in which the alternatives are Oxford Clay, Calcareous Grit Sand and Corallian Limestone. The Chilterns provide an opportunity to introduce chalk to the record.

The area The area (about 100 km2) covered in this study is part of the backward slope of the

Chilterns, a terrain characterized by clay tops and chalk slopes descending usually into dry valleys. The only streams are the Misbourne which rises just north-west of Great Missenden and runs south-east through Amersham, and the Wye which follows a parallel course 10 km to the south. A small tributary of the Wye runs down the Hughenden Valley, joining the Wye in High Wycombe.

FIG. 1. Distribution of badger sets.

Geological information has been taken from the Geological Survey of Great Britain, 1922, reprinted with amendments on the one inch scale. The higher ground is covered by Clay with Flints and associated Pebbly Clay and Sand. Upper Chalk is increasingly ex- posed towards the south-east, giving way to Pebble Gravel and Glacial Gravel in the Beaconsfield area. To the north-west, in the valleys, Middle Chalk is exposed and the

206 N O T E S F R O M T H E M A M M A L SOCIETY-NO. 18

Upper Chalk crops out on higher, steeper slopes and therefore in narrower bands. In the Misbourne and Hughenden Valley bottoms thin strips of Alluvium and Flood Plain Gravel occur. In the sketch map clays are grouped together. Upper and Middle Chalk are separated by a broken line representing Chalk Rock. The map covers a representative 40 km2 (Fig. 1).

Fieldwork The time base for this study is the winter of 1966. During this and the following winter

we investigated the area thoroughly. All the woods have been walked and every farm visited. Gamekeepers have been approached with varying degrees of success and where they have been evasive means have usually been found to circumvent this difficulty. Rabbit Clearance Society warreners with detailed knowledge of the area have been extremely helpful, and individual officers of the Forestry Commission have provided valuable negative evidence. We have been fortunate in finding several interested observers who have been able to report on past activity and who now join in co-ordinated watches. The survey has been checked square by square on the six-inch Ordnance Survey.

Criteria of a set Foxes are common in the area and are sometimes found using the same holes as the

badger. Where sharing occurs the holes have been counted as badger sets. Where diggings bear no sign of occupation (e.g. footprints, dung pits, bedding-either fresh or used in spoil heaps, flies) the size and location of the hole has been the chief guide. In most cases where the hole was not less than ten inches in diameter a local person has stated that badgers have been known to use it. In cases where as many as 40 or 50 holes were scattered along a bank, for as far as 75 yards, or round a large dell, even where it is known that more than one family has been raised in a season, the whole complex has been counted as one set. This is an arbitrary method and is not intended as a definition. For the purpose of this survey it is adequate, since the type of soil preferred by badgers is its subject.

The sets It must be stressed that this paper is not concerned with an estimate of the present

population in the area, and it would be unwise to make any inferences from our count of sets on this score. There have been included in the count several sets which are now, and presumably for ever, abandoned; for instance where new building has occurred or where hedges have been ploughed over. In our experience of this area a single family will visit, during the summer, as many as eight different sets which may or may not have shown signs of occupation during the winter. 117 sets were found in chalk and one set on the clay plateau.

Further analysis of the sets in chalk gives 94 in Upper Chalk and 23 in Middle Chalk.

Discussion The preponderance of digging in the Upper rather than the Middle Chalk is not, ap-

parently, due to any intrinsic qualities of the two strata. When the band of Upper Chalk is traced over the six inch map it is found that where clay gives way to Upper Chalk on the upper shoulders of the valleys this line frequently coincides with the edge of a wood. In

NOTES F R O M T H E M A M M A L SOCIETY-NO. 1 8 207

many places the chalk rock line marks the lower edge of the wood. Following round the contours, therefore, one finds a succession of narrow woods almost exactly coinciding with the band of Upper Chalk. This is the result of farming practice over the years. The clay plateau is more fertile than the chalk slopes and these latter have been planted with trees, usually beech, or left as scrub or natural forest. Further, the top-soil tends to be washed down from the steeper slopes to the gentler slopes below, thus providing better fields where the Middle Chalk lies. It would appear, therefore, that it is the indirect influence of the geology through human control of the woods that explains the apparent preference for Upper Chalk. Both slopes and cover coincide with the Upper Chalk more often than with the Middle Chalk. (It should be added that there are woods on the clay plateau, with slopes in plenty; but no sets occur in them. Very few woods occur below the Chalk Rock line. Of the 23 sets found in Middle Chalk, 12 are in hedges.)

The absence of sets on the clay plateau is remarkable. The one set on the plateau is in an old pit and reaches down to chalk. The clay cap is not deep at this point. The whole Chilterns area has been rightly characterized (in an archaeological context) as almost waterless, and it is known that badgers dig in clay elsewhere. It seems that, in this area at least, where chalk is available badgers seek it out and avoid the clay.

As far as being undisturbed is concerned there is no reason to suppose that the woods and hedges on the chalk slopes are less frequented by man than those on the clay. It is interesting in this connection that Likhachev’s (1956) study of the distribution of sets in a government preserve forest in Russia should produce such similar results to ours in the most heavily populated part of the Chilterns. He found that in an area where the plateau, corresponding to our clay, was covered by a deep impermeable loam, and the ravines cut through to layers of sand, 93% of the sets occurred in the ravines and always where sand was available. Likhachev assumed drainage to be the vital factor.

In our area, although the band of Upper Chalk generally coincides with slopes, which are said to be preferred by badgers, sets are often situated on the floor of a wood where the slope is negligible. The preference for chalk overrides that for slopes.

As to ease of digging, it may be that chalk broken into lumps is more manageable for the badger than clay. The chalk, however, is frequently deeply scored by claw marks which indicates that dislodging it underground is often difficult. M. Dunwell was ac- companied on one field expedition by a geologist, specializing in Chalk Rock, when the spoil heap outside a set was found to be composed entirely of Chalk Rock. The set was an old one, and this prompted the idea that, once excavated, these sets might be very stable and secure.

We consider, therefore, that while cover and good drainage tend to coincide in this area, drainage appears to be the prime factor.

We are grateful to the Forestry Commission for permission to investigate woods under its ownership or management.

REFERENCES Likhachev, G. N. (1956). Some ecological traits of the badger of the Tula abatis broadleaf forests. In Studies in

Government preserves. Yurgenson, P. B. (ed.). Published and translated by the Israel Program for scientific translations for the National Science Foundation, Washington, D.C.

Southern, H. N. & Lynn, I. (1964). Distribution, range and habitat. In The handbook ofBritish mammals: 59-72. Southern, H. N. (ed.). Oxford: Blackwell.

20s NOTES F R O M T H E M A M M A L SOCIETY-NO. 1 8

Postscript

Since the submission of this paper a further 100 sets have been reported in the Chilterns over an area of approximately 250 km2. Tracings from the geological survey show that the distribution follows the same pattern in relation to chalk and clay.

M. R. DUNWELL The Danes,

Penn, Bucks

A. KILLINGLEY 2 West Wuye,

Brand’s Hill Avenue, High Wycombe,

Bucks

AND

Observations on food eaten by Wood mice (Apodemus sylvaticus) and Bank voles (Clerhrionomys gfweohs) in a hedge

During work on a hedge in the John Innes Estate, Hertfordshire, observations were made on hips and haws eaten by Wood mice and Bank voles.

The hedge was sited east-west and consisted mainly of hawthorn 2-3 m high. On the south bordering a field there were many rose bushes. In February 1968 the hedge was bulldozed up and burnt.

In December 1966 neat piles of rose carpels and flesh were observed chiefly at the east end, where the ground cover was less dense and 30 piles were collected. The carpels had been opened and the seeds eaten; the flesh had been bitten into small pieces but not much appeared to have been eaten. Altogether there were 620 pieces of carpel, this represents about 30 hips. The next day more piles were made in the same regions. It was assumed that these piles were left by mice. In November and December 1967 each trap was baited with three hips, two haws, as well as oats. Whole oats were used to make it easier to separate the pieces of carpel. The contents of the traps were tipped into bags and examined later. In every case it was found that mice opened the carpels and ate the seed and voles left the carpels whole (see Plate I). Mice bit the flesh into small pieces, voles appeared to have eaten some flesh and left the rest in large pieces. The haws in the traps had the flesh eaten but not the nut.

In 1967 high winds blew many hips onto the ground so the mice did not have to fetch so many from the bushes. The pieces of carpel were not in such neat piles as in 1966. In September 1968 control experiments were done with mice and voles in captivity, they were kept in separate cages and fed with hips and haws. The results were similar to those in the traps.

Investigation of the number of hips removed at different heights showed that the lower