228 N O T E S O N B R I T I S H M A M M A L S - N O . 1 2

R E F E R E N C E S

Chitty, D. (1937). A ringing technique for small mammals. J. Anim. Ecol. 6 : 36-53. Chitty, D. (1952). Mortality among voles (Microtis agrestis) at Lake Vymwy, Montgomeryshire in 1936-39.

Jewel], P. A. (1964). An observation and breeding cage for small mammals. Proc. zool. SOC. Lond. 143: 363-364. Leslie, P. H., Chitty, D. & Chitty, H. (1953). The estimation of population parameters from data obtained by means

of the capture-recapture method. 111. An example of the practical application of the method. Biornetrika

Phil. Trans. (B) 236: 505-552.

40: 137-169. Linn, I. & Shillito, J. (1960). Rings for marking very small mammals. Proc. zool. SOC. Lond. 134: 489-495. Shillito, J. F. (1963). Field observations on the growth, reproduction and activity of a woodland population of the

Smyth, M. (1965). Harvest mites on bank voles that have lost a leg. J. Zool. 147: 221-222. Southern, H. N. (1964). The handbook of British mammals. Oxford: Blackwell.

common shrew, Sorex araneus L. Proc. zool. SOC. Lond. 140: 99-113.

P. J. FULLAGAR Royal Veterinary College, London University

Present address :-- Division of WiIdIife Research, C.S.I.R.O., Canberra, Australia and

P. A. JEWELL WelIcome Institute of Comparative Physiology,

Zoological Society of London, Regent’s Park, London, N . W.2

Notes on the red fox (Vulpes vulpes) near Braemar, Scotland

In Lowland Britain, fox-hunting affords the red fox some protection but in the Scottish Highlands game-preservers and farmers look upon it as a pest. The species is trapped and shot throughout the year but nevertheless persists sometimes at high densities.

Near Braemar, foxes are most vulnerable during April and May when the cubs are born and the vixen is suckling. At this time, stalkers and gamekeepers visit all the known dens and look for new dens in order to kill both the cubs and the vixen. This paper describes observations made during the three years 1959 to 1961 when I accompanied the stalkers of the Braemar area on their visits to the dens.

Description of area

The study area covers over 87 square miles in North-West Aberdeenshire and comprises some of the most mountainous country in Scotland from 1100 to 4296 feet. The two private estates of Mar and Invercauld are within the area and the eastern half of the Cairngorms National Nature Reserve is contained within Mar. Most of the land is deer forest with barren expanses of scree on the high hills and heather and grass-covered hills lower down. There are many peat bogs and few trees. In April, corries and hollows as low as 2000 feet are filled with drifts of hard-packed snow. Snow, sleet and rain with cold winds are usual during this month.

NOTES O N BRITISH M A M M A L S - N O . 12 229

Methods

The den was approached quietly and a terrier dog released into the entrance. If the vixen was with her cubs the terrier might make her bolt when she was shot (six instances). If the vixen was caught in a dead-end, the terrier either killed her (two instances) or enticed her out by retreating to the entrance where it was immediately signalled away by its owner. If this happened, the waiting men stood where the vixen could neither scent nor see them. Usually the vixen followed the terrier to the entrance and in a moment bolted from the den. In one instance the vixen stayed with her cubs and had to be trapped. With a well-trained terrier it is possible to kill and collect the cubs.

Throughout much of the year, in addition, gamekeepers set spring traps in likely places in order to catch adult foxes.

I weighed the dead foxes on a spring balance to the nearest $ lb (converted Kg in Table l), measured them with a steel tape (cm), examined them for disease and parasites and found the number of placental scars in the uteri. I collected and analysed the stomach contents and made notes about prey at the dens and the dens themselves.

Weights and body size

The total length of an animal was measured from the tip of the nose to the tip of the tail with the tape running along the back of the animal over the curves, the animal being stretched out on the ground. Vixens varied between 76 and 107 cm in total length (including the tail) and their tail lengths varied between 30.5 and 39 cm. They weighed between 9 and 17 Ib (4, 74 kg). The only dog fox measured weighed 149 lb (64 kg), and was 118.5 cm long of which 42 cm was tail (Table I).

Behaviour at the den

The den may be near houses or in remote places. It may be in rabbit burrows (Oryctolagus cuniculus), peat holes or deep in great mounds of boulders locally known as a rock cairn. A sand hole, however, is preferred until the cubs outgrow it and are moved to a rock cairn and thence to a peat hag. Of 52 dens for which I have records, 39 were sand holes, seven were rock cairns and six were in peat. A south aspect occurred most frequently, followed by eastern, northern, western and all-round aspect in that order.

The dog fox seems to do most of the house-hunting and cleans out several likely places but the vixen seems to make the final choice. Sometimes the prospective den is under snow and the fox tunnels down to the entrance. The den may be dry but if not or if the den is disturbed the vixen will move to another site. A dry den within reach of adequate food and water is essential. If disturbed after parturition she quickly carries the cubs to another den. Probably the dog fox helps with this, for, if the vixen is killed at the den, the dog fox will move the cubs to safety if he can reach them. He will certainly bring food to them but unless they are weaned (i.e. over one month old) they do not survive.

I recorded the presence or absence of the pair at dens I visited and this is summarized in Table 11. Vixens are much more vulnerable to capture at the den, as might be expected.

230 N O T E S O N B R I T I S H MAMMALS-NO. 12

Dens were situated at from 1300 to 2550 feet In 1959 the height of dens ranged from 1300 to 2040 (average 1623), in 1960 from 1300 to 2275 (average 1800) and in 1961 from 1525 to 2550 feet (average 1950 feet). Presumably, the higher dens are not so popular in a late spring, and in fact 1961 was an early spring.

TABLE I Data from adult female foxes and one male killed at dens from 1959-61

Young

Young

Young Young

Mature

Young

Young

Mature Old

Old

Young

Young

Young

Mature

Young

Old

Young (male)

6.5

4.1

5.5 5.2

7.7

7.0

7.0

6.3 7.0

6.8

5.4

6.3

5.9

1.7

6.1

6- 1

6.5

Total length (cm) __

105

107

102-5 111

99-3

107

104.5

76.4

100.1

107

82.7

118.5

Tail Parasites in Stomach (cni) Condition a t contents

35.5

38

31 373

38.1

38.1

38.1

35.5

305

38.1

39.4

42

Fair Nematodes

Fair, injured None found kidney

Good Good

Very good

Very good

Good

Good Good

Good

Good

Good

Good

Very good

Good

Good

Good

None found None found

None found

None found

Light infestation of cestodes

None found Heavy infestation

of cestodes Heavy infestation

of cestodes Heavy infestation

of cestodes Heavy infestation

of cestodes Heavy infestation

of cestodes Heavy infestation

of cestodes Heavy infestation

of cestodes One cestode

Heavy infestation of cestodes

Mountain hare, deer carrion, beetles

Deer carrion, beetles, frog, vole

Empty Deer carrion, small

bird, voles Deer carrion, lamb,

mice, red grouse Deer carrion, black

grouse, vole Voles, red grouse

Empty Deer carrion, red

grouse Deer carrion

Deer carrion

Deer carrion, voles

Deer carrion

Rabbit

Deer carrion, red grouse, voles

Deer carrion, beetles, red grouse

Deer carrion, beetles

In general, the more regularly used dens are extensive and deep with many exits, Usually only one entrance is used until the cubs begin to appear above ground when the den becomes untidy with the remains of prey. The cubs wear small paths in the surrounding vegetation as they venture outside to explore and play and there is always a well-worn track to the nearest water.

N O T E S O N B R I T I S H M A M M A L S - N O . 12 23 1

About this time, they leave their first home which is now filthy with decaying food and droppings. The next den is a rock cairn or a peat hag and both give much more room for the family to play and shelter.

TABLE I1 The presence or absence of adult foxes at the dens visited

Female Male

Animal was in den 15 0 seen in the distance 4 3 absent 4 20

Total 23 23

Breeding season and sex ratio of cubs The earliest litters were born about 9 April. With a gestation period of about two months

(Sandars, 1936) the date of conception would be early February. This is later than Lowland Scotland and much later than the south of England where Sandars (1936) states that cubs have been born in early January.

In 1959, the first cubs were born about 14 April and the last about the 26th; in 1960 the respective dates were 9 and 29 April; and in 1961, 17 April and 3 May.

During the three years’ study, 82 cubs were examined. The sex ratio was different each year with an excess of females in 1959 and 1960 and an excess of males in 1961 (Table 111).

TABLE 111 The number of each sex, adult and young, killed ar dens I95941 t

Adult Young Year Female Male Female Male

1959 1960 1961

5 0 4 0 7 1

Total 16 1 45 (54%) 39

t Note: the sex ratio of foxes killed outside the breeding season away from dens in 1960-61 was 11 females to 12 males

In 1961, foxes were more numerous than in the previous two years after a mild winter and an early spring.

16

232 N O T E S O N B R I T I S H M A M M A L S - N O . 12

Growth of cubs

New-born cubs have a blue-grey woolly coat with a white tip to the tail. At three days, the coat shows brown on the head and this gradually increases until at three weeks it covers head and shoulders. By four weeks the coat is a dark fawn-brown changing to a yellowish brown at six months; the legs have black “stockings”.

The cubs are born blind, and their eyes open at about eight days. At birth they weigh no more than 4 oz (1 13.6 g) but subsequently the weights of members of a litter become increasingly divergent depending partly on sex and partly on the distribution of food to the litter. Table 1V shows the range of recorded weights of cubs whose ages were estimated from accumulated field experience.

TABLE IV The growth of cubsfrom birfh to 28 days

Approximate age Range Average No.

(days) (9) weighed

Birth 114 114 6 3 228-242 232 5 5 383-456 449 9 7 426483 454 8

14 767-9 12 824 9 21 568-753 662 12 28 795-1 107 1057 10

The change to a flesh diet begins slowly at 21 days when the cubs suck flesh. I believe that the vixen may regurgitate food to the cubs at this time for the stomachs of two 21-day old cubs I examined contained half-digested voles, Microtus ogrestis, and milk. Two other members of the litter contained only milk and one was empty. At four weeks the cubs eat flesh, voles being their main diet.

A male cub, about 13 weeks old and shot on 13 July 1960 provided the following information: total length, 81.3 cm; tail, 27.0 cm; weight. 3.2 kg; condition, good; stomach contents, voles and deer carrion.

At 13 weeks, the cubs are still being fed by the parents.

Food eaten

The stomach contents of 15 adult females and one adult male were examined during April and May when the dens were visited and were, in order of frequency (Table I): red deer (Cervus elophus) carrion, 13 stomachs; voles (Microtus agrestis), seven stomachs; red grouse (Lugopus scoticus), five stomachs ; water and ground beetles, four stomachs; black grouse (Lyrurus tetrix), mountain hare (Lepus timidus), frog, small bird, lamb carrion, rabbit and roe deer (C. cupreolus) all occurred once.

N O T E S O N B R I T I S H M A M M A L S - N O . 12 233

Disease and mortality Some of the foxes examined were thin, some very fat but most were in good condition

(Table I). One had an enlarged kidney in a haemorrhagic condition. Few had many internal parasites. One fox had recovered from mange.

Foxes do not recover from serious injuries as easily as, say, red deer. Shotgun wounds, and the loss of a limb by a trap usually result in death during the following winter. Reports of three-legged foxes are not uncommon but the small proportion that are subsequently caught suggests that they die in concealed places.

1 have arbitrarily grouped the foxes into three age classes based on tooth wear as follows: young, teeth clean and sharp, mask youthful; possibly one year old; mature, some tooth wear, body “mature looking”, possibly two to four years old; old, teeth well worn, body “heavy looking”, possibly five to six years old.

In addition, I have occasionally seen very old animals emaciated and grizzled with the teeth worn down to the gums. None of the fourth category was seen during the study.

Of 17 vixens examined at dens in April and May, 60 % were “young”, 20 % mature and 20% old. Evidently the turnover is rapid, unless older animals avoid capture.

As already mentioned (see Table 11) the vixen is much more vulnerable at the den than the dog fox and this is confirmed (Table 111) since 16 vixens were destroyed for one male. At other times of year, however, (footnote to Table 111) more males are destroyed than females. Over the whole year twice as many females as males were killed by fox hunters. One wonders what effect this has on breeding rate and whether the fluctuating sex ratio (Table 111) could be a compensation for this biased destruction.

Summary Game-preservers and farmers in the Scottish Highlands regard the fox (Vulpes vulpes) as

a pest and shoot and trap it throughout the year. During the breeding seasons 1959 to 1961, I accompanied stalkers on their visits to dens in an area of over 87 square miles of mountainous country in North-West Aberdeenshire. The use made of terriers to bolt and kill foxes is described.

The size and weight of adults varied widely. The breeding season, in every year later than in other parts of Britain, was rather different in each of the three years. The growth and sex ratio of cubs is described and the altitude and aspect of dens discussed. The food is varied and includes red deer carrion, voles and red grouse. The population turnover is rapid, 60% of adult females killed at dens in spring being young animals.

I acknowledge gratefully the co-operation of stalkers R. Scott, A. Rae, and A. Dempster of Mar estate and C. MacIntosh, D. MacDonald and D. Campbell of Invercauld estate. Captain Ramsay and Captain Farquharson, owners of Mar and Invercauld respectively, gave permission for me to accompany the stalkers on their visits to the dens and the Nature Conservancy granted time from my duties as warden for the study. I am also grateful to J. Grant Roger and Dr J. D. Lockie for guidance and encouragement.

REFERENCE Sandars, E. (1936). A beast book for the pocket. Oxford: Univ. Press.

M. J. W. DOUGLAS Forest Research Institute, P.O. Box 106, Rangiora, New Zealand

16*