The rabbit in continental Europe




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Fig. 3.16 Diets of foxes in two areas of France (Fragner et al. 1990). Touraine is 200 km SW of Paris.


The rabbit in continental Europe 49

Table 3.16 Number of predator species in various parts of the rabbit's range worldwide

Class

Australia

New


Zealand

UK

France

Spain


Mammals

3

3

10

10

17


Birds

14

1

7'

13

19

Reptiles

6

0

0

7

4

Totals

23

4

17

30

40


Source: Soriguer (1981a), Soriguer and Rogers (1981) except Australia (Myers et al., Chapter 5) and UK (Thomp- son, Chapter 4).


3.6 Myxomatosis (see also Chapter 7)


3.6.1 Incidence
The rapid spread of myxomatosis throughout Europe, starting from Dr Delille's estate near Paris in June 1952, has been well-documented, but substan- tial study of the disease in wild rabbits in continental Europe did not begin until 20 or so years later. Up to the 1970s we have data only from domestic rabbits. In France, the number of domestic rabbits with the disease climbed to a peak in 1955, and in 1960 stabil- ized at around 100 000 cases a year (Fig. 3.17). A clear seasonal pattern became established, in which incidence ranged from a maximum in August-Sep- tember to virtually zero from December to May-June (winter to early summer), although spring epizootic were not unknown (Fig. 3.18; Joubert et al. 1972).

Data on myxomatosis in wild rabbits are now avail- able from different parts of France (Table 3.17),

including the Camargue, the Vaucluse, and the Ile-de- France. In the Camargue, epizootics recur regularly every summer, and in the Vaucluse, every autumn. In Ile-de-France, however, myxomatosis may break out at any time. In the Isere, near Lyon, the timing of epizootics is also variable, although it is usually in late spring or early summer (Fig. 3.19; Gilot and Joubert

1980). In the north, epizootics last about 3 months, often longer than in the Camargue and significantly longer than in the Vaucluse (2 months).

In southern Spain, July to September/October

used to be the usual period for epizootics, but since

1977 they have been most frequent in winter-spring, lasting 6 months in 1976 and 10 months in 1977,
although some years are without the disease al- together (Soriguer 1980a, 1981a). More recently the highest mortality has been from July to October (Soriguer 1981a; Soriguer and Rogers

1981). The mean interval between successive epi-

zootics is the same (9-10 months) in the three

regions for which we have data, but is most vari- able in the north, where it may be anything from

4 to 24 months.

Estimated mortality, calculated from the ratio of acute to total cases including recoveries, varies from

39 to 61 per cent with little difference between years. The highest mortality is in summer epizootics (43 per cent over 6 months), lower in autumn (13 per cent over 2.3 months), and lowest in winter epizootics (6 per cent in 4.5 months). There is, nevertheless, great variability in mortality rates between areas, and again the most variable region is Ile-de-France. In both the Camargue and the Vaucluse, total losses per epizootic are similar, 32 and 36 per cent respectively. The short autumn epizootics in the Vaucluse seem to be especially intense, affecting some 83 per cent of the juveniles and sub-adults but total losses are few. Many young rabbits there exhibit high levels of resistance to myxoma virus in the laboratory (no deaths out of 11 young rabbits tested in the Vaucluse compared with 5 deaths out of 7 young rabbits tested in Ile-de-France; Arthur, Gaudin and Guenezan, unpublished data).

The proportion of rabbits affected varies with age- class, region and year (Table 3.18). In southern Spain




Fig. 3.17 Numbers of domestic rabbits with myxomatosis in France,

1953-56 (after Joubert et al. 1972).


Fig. 3.18 Annual changes in myxomatosis rates in wild and domestic rabbits in France, 1959-66 (after Joubert et al. 1972).




Vaucluse n=3


Camargue n=5


Paris region n=9


1.

Duration (months)

2.2 ± 0.6




3 ± 1


3.1 ± 1.9

2.

Interval between two









3.


epizootics (months) Proportion of animals

9.8 ± 0.4

9.7 ± 0.6

9.4 ± 6.5




affected (% cumulative)

83 ± 29'

59.9 ± 27'

41 ± 31

4.

Estimated mortality (%)

39 ± 10

61 ± 10

54 ± 13

5.

Population losses (%)

32 ± 8 b

36 ± 11"

22 ± 20

6.

No. of epizootics in













spring

0

0

3




summer

0

5







autumn

3

0







winter

0

0

2



Table 3.17 Characteristics of myxomatosis epizootics in three sites in France

4

Only juveniles, immatures and sub-adults were affected.



h Losses were from the young of the year only.

3. = proportion of infected animals, summed monthly.

4. = proportion of animals with acute and severe clinical sign. n = number of epizootics observed.

Source: Paris-Arthur (1988); Camargue-Rogers (1979), Vandewalle (1986) Vaucluse-Arthur and Gaudin (in

press).



the proportion of juvenile rabbits found with clinical signs is low because, we suspect, they succumb to the disease quickly, often before showing any exter- nal sign; the proportion of juveniles with antibodies (13 per cent) is about half of that in adults (Soriguer and Lopez, in press). In the Camargue and the Vaucluse few juveniles are diseased, whereas in Ile- de-France juveniles represent 19 per cent of affected animals. In the north, 33 per cent of adults captured showed clinical symptoms, whereas in the Camargue and the Vaucluse almost no adults are affected.

3.6.2 Epidemiology
Many of the different regional characteristics of the disease reflect variation in transmission routes and in the immunological status of the populations. The relationship between rabbits and myxomatosis has also changed over the years.

In France and Spain, as elsewhere, there are two

known vectors, fleas and mosquitoes. Their relative

importance and specific roles vary from one region to another. Rabbits in Spain support at least 22 genera of ectoparasites, versus 8 in Australia, all but one of which are also recorded from Spain (Table

3.19).

In the Camargue at least 12 species of mosquito



bite rabbits from late March to end-October; they are especially active in May and October, when they may inflict 1200 bites per rabbit per day. Although mosquitoes are relatively uncommon in July- August, when epizootics of myxomatosis are usually at their height, each rabbit is still bitten 60 to 300 ti mes a day during the months that mosquitoes carry the virus. Some 20 to 30 per cent of mosquitoes are carriers, and 50 per cent in A edes detritus and A . cas- pius, the two species most attracted to rabbits (Legrand 1986). The proportion of mosquitoes which are carriers reduces gradually through the season, to nil in October. In contrast, in the Isere some 10 species of mosquito bite rabbits from the beginning of May to the beginning of October, averaging only

40 bites/rabbit/day. In Ile-de-France only 5 species




52 P. M. Rogers, C. P. A rthur, and R. C. S origuer



Table 3.18 Percentage of rabbits captured (numbers in parentheses) having clinical sign of myxomatosis during epizootics in France (years pooled) and Spain
Vaucluse Camargue Ile-de-France Spain
1976 1977

Juveniles (<500 g)


1.8



(648)

1.9

(321)

19.1



(833)


0.0

(130)



9.6


(52)

I mmatures and sub-adults

47.7

(235)

62.8

(137)

35.4

(768)

8.2

(49)

38.9

(36)

Adults

0.0

(83)

6.0

(73)

32.8

(481)

4.0

(228)

17.6

(131)

Source: Arthur (1988); Soriguer (1980a).



Table 3.19 Genera of ectoparasites found on rabbits in Spain and Australia
Spain Australia
A mblyoma B dellonypsus B oophilus Cheyletiella Caenopsylla Echidnophaga Cheyletiella Haemadipsus Chorioptes Haemaphy salis Ctenocephalides L istrophorus Dermacentor Spilopsyllus Desmodex X enopsylla Haemadipsus

Haemaphy salis

Hyaloma

Ixodes

L inguatula

L istrophorus

Notoedes

Odon topsyllus Pulex Psoroptes Rhipicephalus Sarcoptes Spilopsyllus

X enopsylla
Source: Soriguer (1980b).

bite rabbits, from May until September, and the maximum number of bites per rabbit per day is 12 in July (Vandewalle 1981).

The abundance of fleas, at least on French rab-

bits, varies inversely with that of mosquitoes. In both the Camargue and Vaucluse the average num- ber of fleas per rabbit (adults and sub-adults) is greatest from March to April (Camargue, 20-30 fleas per rabbit; Vaucluse, 40-60 fleas per rabbit), and is virtually zero during the season of epizootics. In Ile- de-France rabbits carry the most fleas, 60 to 120 per rabbit, from February to May. In summer the num- ber is still 10 to 20 (Launay 1980; Fig. 3.20).

The virus is present on the mouth-parts of fleas throughout the year in all three areas studied in France. That is, while fleas are proven carriers

Fig. 3.20 Monthly numbers of fleas on rabbits in France. (a) Camargue (Vandewalle unpublished), (b) Vaucluse (Arthur and Gaudin unpublished), (c) Paris (Launay and Arthur unpublished).
during epizootics, they also carry the virus even when no disease is evident among the rabbits, also in May even in the absence of any sign of the disease (Gourreau et al. in preparation). The presence of the virus on known vectors apparently in the absence of


Fig. 3.21 Proportion of juvenile and adult rabbits with myxoma antibodies, Camargue, southern France, 1984-7 (after

Vandewalle, unpublished).




any clinical sign of disease is puzzling, and raises important questions about, among other things, the immunological status of the rabbit population.

In the Camargue there is a clear seasonal cycle in

the proportion of rabbits with antibodies (Vande- walle 1986). All adult rabbits have antibodies after an epizootic (usually in late August or early September) (see also Chapter 7). They all continue to carry anti- bodies until January-February, when the proportion gradually decreases to 20-30 per cent in April-May, just before the start of the next epizootic. A variable proportion (0 to 25 per cent) of juveniles carry anti- bodies until the age of 2 months, but during an epizootic the proportion of juveniles climbs quickly to reach 100 per cent by the end of August (Fig. 3.21). Thereafter they follow the adult pattern.

In the Vaucluse all adults have antibodies from October to June, after which the proportion de- creases to about 50 per cent in August. From Sep- tember, stimulated by the appearance of a new epizootic, the proportion climbs back to towards 100 per cent. Again, some 10 to 50 per cent of young rab- bits carry antibodies until the age of 2 months. By June-July usually less than 10 per cent of young still have them, but the proportion rises to 50-60 per cent by the end of October, and 90-100 per cent in Janu- ary (Fig. 3.22; Arthur and Gaudin, in press).

Results from Spain confirm this pattern. After an outbreak over 90 per cent of rabbits carry antibodies,

declining to 50 per cent five months later. Mortality particularly affects juveniles and sub-adults, because



40 per cent of young rabbits (up to 800 g) do not

carry antibodies (Soriguer 1980a, 1981a).

In the Ile-de-France, there are two different cycli- cal patterns. When there is no autumn or winter

epizootic, the 50 to 60 per cent of adults which have detectable antibodies in May declines to 10-20 per cent by January-February. During the summer, 15-

20 per cent of young (up to 2 months) have maternal antibodies, but in August-September they lose their

antibodies, and from October-November, when the young of the previous season make up three-quar- ters of the total population, the proportion with detectable antibodies stays at zero until the onset of the next epizootic. After a new epizootic, the propor- tion of surviving rabbits carrying antibodies increases rapidly the following spring, according to

the intensity of the outbreak, to stabilize by August at 60-70 per cent. About 30-40 per cent of the young of the year have antibodies.

The second type of cycle starts after an autumn or

winter outbreak, and its effect is to stimulate a higher level of resistance in winter and spring. After an autumn epizootic, 70-90 per cent of adults and young are carriers by November; or 30-40 per cent by February-March after a winter epizootic, the majority of them being young of the previous season (Arthur, unpublished data).




Fig. 3.22 Changes in the proportion of juvenile and adult rabbits with myxoma antibodies, Vaucluse, south- central France, 1985-7 (after Arthur

and Gaudin in p ress).




3.7 Viral haemorrhagic disease


Viral haemorrhagic disease (VHD) was first de- scribed in domestic rabbits in China. The cause was a small (28-33 nm diameter) round icosahedral virus, without envelope. The nucleic acid is single-strand RNA (Liu et al. 1984). The virus could agglutinate erythrocytes in the blood of sheep, poultry and humans (type 'O'). The incubation period for the dis- ease was 48-72 hours, with death from several hours to one or two days later. The typical symptoms was epistaxis, although often no clinical sign was

observed. Characteristic pathological changes included punctate haemorrhage in the respiratory and digestive systems, the spleen, cardiac muscles, and occasionally the kidneys. A rabbit tissue vaccine of virus inactivated with 0.4 per cent formaldehyde was developed with satisfactory results; later modifi- cations improved its efficiency (Arguello 1989; Pages

1988).


A few years after Liu described it in China, the same disease appeared in Europe, under several



aliases: virus 'x', hepatosis, rabbit haemorrhagic disease, haemorrhagic septicemia syndrome,viral haemorrhagic disease. It caused high mortality in domestic and wild rabbits, and also hares, in Italy (Cancelloti et al. 1988), France (Morisse 1988), Spain (Arguello etal. 1988), Germany (Loliger et al. 1989), Austria (Nowotny et al. 1990). VHD is similar to another disease of hares, European brown hare syn- drome, which produces VHD-like lesions. VHD can be transmitted to hares, experimentally at least, and in Czechoslovakia hares have been found with VHD antibodies (Morisse et al. 1991).

VHD was first detected in Spain in the spring of

1988, in both domestic and wild rabbits from two widely separated areas, Asturias in northern Spain and Almeria in the south-east (Arguello 1989). A little more than a year after these first two foci were detected, only the south-west parts of the country were VHD-free. The disease was recorded in the adjacent region of Murcia, at Sucina in December

1988, and at Lorca in April 1989 (Leon Vizcaino,

unpublished); one year later the first rabbit with VHD was found in Donana National Park. In only two years the virus had spread throughout the whole of Spain.

In France, the first outbreak of VHD was recorded in the summer of 1988, in several small rabbitries in the north-east (Haute-Saone, Vosges, Cote d'Or). The deaths were so unusual and unexpected that they were at first attributed to radiation from Cher- nobyl or some other environmental pollution. Their infectious origin was not discovered until the end of the year (Morisse 1989). Of over 100 dead rabbits

taken from all over France in 1989, about half had died from VHD (ONC 1990). By the end of 1991 VHD was established in 56 out of the 95 departements of France.

In parts of France (in the Camargue, Vaucluse,

Herault) several VHD epizootics break out each year.

Their effect on wild rabbit populations, although largely unquantified, has often been dramatic. Soriguer and Cooke (unpublished) observed one of the initial outbreaks of VHD in wild rabbits at El Alquian (Almeria, Spain) in June-July 1988. Because the disease progresses so rapidly, some rabbits died while trying to escape them, yet without showing any external symptom. There were many more dead rabbits on the ground than the predators and scavengers could remove (Leon Vizcaino, Cooke and Soriguer, personal observations). In Donana National Park, where systematic observations had been made for some years, VHD was associated with an additional mortality of 60 to 70 per cent or more (Villafuerte and Moreno personal communication). On a reserve in the Vaucluse, the reduction in popu- lation was estimated at 70-80 per cent (Gaudin, personal communication).

From an ecological point of view in the predator- rich community of the Mediterranean, VHD repre- sents a catastrophic event. Studies now in progress show that rabbits have begun to develop some genetic resistance to the disease, although annual outbreaks are normal. It is still too soon to make any predictions, but we expect that some equilibrium between the VHD virus and the rabbit will develop eventually, as with the myxoma virus.



3.8 Conclusion


The picture of the rabbit in Europe which emerges from this review is that of a biological opportunist bound by ecological constraints. Like any mammal, the rabbit needs high quality food for reproduction and growth. Its reproductive strategy is flexible enough to allow exploitation of favourable periods of plant growth-indeed it has evolved physiological links with photoperiods to enable it to predict them. Its habitat requirements are not too specific, some- where to dig a hole and food nearby. Given its requirements the rabbit's productivity is proverbial

(see, for example, Thompson and Worden 1956; or

Sheail 1971).

There must, however, be constraints to hold such

potential in check. In southern Spain, which is per- haps the nearest contemporary equivalent of the rab- bit's ancestral home and where we have relatively undisturbed study sites, there seem to be three groups of constraints: terrain, climate, and preda- tion. The same three reappear in the south of France as part of the recurring theme of latitudinal trends. Terrain determines the security of the burrows.



While it is not uncommon for some rabbits to live above ground, whole populations thrive only where the soil is suitable for building burrows, or where some substitute is available (some thriving popula- tions in Spain use gaps between rocks, where it is impossible to burrow). Climate limits the reproduct- ive season of the rabbit, via its effects on vegetation, quantity in winter, and quality in summer. But even so the rabbit might be able to outstrip its resources but for the third and final constraint, predation. In many places today this may be imposed by shooting, but an impressive variety of natural predators depends on rabbits, especially in the south. Many translocation/reintroduction efforts fail in Spain because predators kill the rabbits before they can establish stable burrows in their new home. The rabbit has also managed to come to terms with catastrophic events such as the arrival of myxomato- sis and VHD. Such ecological adaptability allows a stability in southern rabbit populations that is not to be found further north.

Historical changes in land use allowed the rabbit to extend its range northwards. It was a serious pest

of agriculture in the north of France by the sixteenth century. But the damage it did was outweighed by its value as a game species, and from the end of the nineteenth century active management by game- keepers encouraged the rabbit to attain very high

population densities between 1920 and 1940. The introduction of myxomatosis was a spectacular set- back, but recovery began quickly and continued throughout Europe until 1970. Since 1980, further changes in land use and the appearance of new epizootics have reduced the numbers of rabbits available:for shooting. The efforts of hunters in the south to augment game populations have been copied in the north. Conservationists also work to maintain rabbit populations, in order to protect the many Mediterranean predators that depend largely on rabbits-some exclusively, such as Bonelli's eagle Hieraetus f asciatus during its nesting season (Iborra et al. 1990). The same is true for the Spanish lynx Lynx pardina and the imperial eagle A quila adalberti (A . heliaca), two of the most endangered species in Europe.

The biology and ecology of the rabbit in Europe, from Sweden where it is an introduced species to its

ancestral home in the south of Spain, show a tremendous range which spans the differences measured in other parts of the world. In its ancestral home the rabbit is an essential part of a complex natural environment. Only when it is removed from the demands and constraints of that environment does the ecological opportunism, which allows it to survive at home, turn it into a pest elsewhere.




3.9 Summary


Ory ctolagus, first known from the Miocene in south- ern Spain (5-7 million years ago) is of uncertain ancestry. Of its three known species (lay ensis, lacosti, and cuniculus) only one is extant, O. cuni- culus. It was first found in southern Spain in the mid-Pleistocene and co-existing with the other extant lagomorph, L epus. Over the last 15 000 years O. cuniculus has become smaller. Today it also exhibits a latitudinal gradient in body size, rabbits in the north of Europe being some 50 per cent larger than the south.

Genetics and ectoparasites indicate 3 groups of rabbits. In southern Spain, their presumed ancestral home, they have been separate from those of south- ern France (and of northern Spain) for over 50 000 years. Northern European rabbits represent a third

distinct group to which domestic rabbits and those introduced elsewhere are most closely related.

Rabbits spread through Europe in the last 10 000 to 20 000 years from the Mediterranean. Their domestication by monks in France in the Middle Ages, where rabbits have long been managed for food or as game, is well documented. Population numbers gradually increased until the 1920s, much higher in the north than the south, staying high until the introduction of myxomatosis in 1952 near Paris. The disease spread throughout most of Europe in little more than a year, decimating populations. After

4 or 5 years, numbers gradually increased until the

early 1970s, and more rapidly thereafter.

Inherent population cycles, disease, and climate

may all influence changes in population numbers.






Terrain characteristics and changes in land use are also important. The rabbit has the status of game throughout most of Europe, and open seasons and hunting methods are strictly controlled. In France and elsewhere, rabbits (wild-type and crosses) are bred for restocking wild populations. Releases of alien species, notably Sylvilagus spp. have occurred, but with little success, and are illegal. Conflict between farmer and hunter is reduced by compensa- tion systems, but not in Spain, where rabbits are not officially regarded as a pest.

Extensive studies show that rabbit diets in Europe reflect landscape and climate. Grasses and forbs are preferred, and a small number of plant species may make up a large proportion of the diet. Exclosure experiments have emphasized the role of rabbits as primary consumers, and in changing floristic com- position. Rabbits may have an important, so far unmeasured, role in seed dispersal especially in the south of Spain.

The length and timing of most reproductive parameters also show strong latitudinal trends. Northern rabbits starting breeding older, later, and for longer than their counterparts in the south and produce more young per year. In Mediterranean areas breeding is extremely variable. In southern Spain male reproductive cycles can be predicted

mainly from the climate, particularly radiation and temperature; climate is also important for females, but less so than food quality. These characteristics reflect the opportunist strategy of rabbits, a response to the variability of Mediterranean weather patterns.

Survival rates of young rabbits in southern Spain are much lower than in France. Conversely, survival rates of adults are much higher in Spain. Causes of mortality include hunting, predation, often in com- bination with disease, and injuries from farm machinery. In the west Mediterranean the number of predator species is high. Rabbits are important in most predators' diets, especially in southern Spain, where all medium and large predators except wolf rely largely on rabbits, and some exclusively during breeding.

Both myxomatosis and viral haemorrhagic

disease are endemic in Europe. Genetic resistance to myxomatosis is well-established, and resistance

appears to be developing to the latter. Both have an extensive influence on population numbers.

In its ancestral home the rabbit is an essential part of a complex natural environment, valued by hunters and conservationists alike. The demands and con- straints of that environment have prevented it becoming the pest that it is elsewhere.




Acknowledgements


The authors are grateful for financial support from the Fondation Tour du Valat and the National Research Council of Canada (to PMR), the Office National de la Chasse (to CPA) and the Consejo Superior de Investigaciones Cientfficas (to RCS). Much of PMR's input is derived from work done at the Station Biologique de la Tour du Valat from

1975-9. CPA was employed by the Office National

de la Chasse whilst collecting the date used in this chapter. Section 3.1 was written with N. Lopez Martinez, Universidad de Madrid and E. Bernaldez, EstaciOn Biologica de Donana, CSIC, Sevilla, and

0. Lopez Ribeiro, Portugal. PMR and RCS also wish to acknowledge a debt of gratitude to Dr Ken Myers for support, guidance and fruitful collaboration over many years-no Ken, no chapter.



References


Andersson, M., Dahlback, M., and Meurling, P. (1979). The biology of the wild rabbit, Oryctolagus cuniculus, in southern Sweden. I. Breeding season. V iltrevy, 11, 103-27.

Arguello, J. L. (1989). Ovejero (Spain) develops vaccine for a new disease in rabbit. A nimal Phar- macology,

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