Public concern about bats (Chiroptera) in Britain: An analysis of enquiries in 1982–1983

Biological Conservation 36 (1986) 3 15-328

Public Concern About Bats (Chiroptera) iu Britain: An Analysis of Enquiries in 1982-83

A. J. Mitchell-Jones, D. J. Jefferies Nature Conservancy Council, Northminster House, Peterborough PEl IUA, Great Britain

R. E. Stebbings& H. R. Arnold Institute of Terrestrial Ecology, Monks Wood Experimental Station, Abbots Ripton, Huntingdon, PE17 2LS, Great Britain

ABSTRACT The Wildlife and Countryside Act 1981 protected all species of bat and required that, in certain circumstances, advice be sought about them. Analysis of these enquiries produced data about their geographic distribution, the types of problem that arose, the acceptability of the advice provided, the species of bat involved and the organisations receiving the enquiries. The great majority of enquiries related to dwelling-houses and, of these, most resultedfrom the discovery of bats roosting in the roof The conservation organisations, mainly the Nature Conservancy Council, proved very successful in persuading householders to leave bats undisturbed; almost all colonies were permitted to remain temporarily and many were permitted to return in succeeding years. Repairs or remedial timber treatment to roofs used by bats were also important sources of enquiries and detailed advice was provided. Most enquiries came from southern England, with a sustained decline towards the north. Pipistrelles were the most common species, followed by long-eared bats. The other 13 species appeared to be involved in relatively few cases. 315 Biol. Conserv. 0006-3207/86/$03.50 0 ElsevierApplied SciencePublishers Ltd, England.

1986. Printed in Great Britain

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et al.

INTRODUCTION The British Wildlife and Countryside Act 1981 gives greater protection to all 15 species of native bats than to any other mammals. For a number of protected species of mammals (those on Schedule 5) it is now an offence deliberately to kill, injure or catch them and also intentionally to disturb or damage, destroy or obstruct accessto any structure or place used for shelter or protection. The only defencesat law, except for licensed activities, are that first, these protected species were killed, injured or disturbed or their sheltersobstructed or destroyed as an incidental result of an otherwise lawful operation which could not reasonably have been avoided, and second, shelters may be disturbed, destroyed or obstructed if they are in dwelling houses. However, for bats and bat roosts these two defences may only be relied on if the Nature Conservancy Council (NCC), the government’s official advisory body, has been consulted and allowed a reasonabletime to advise. The only circumstance to which this requirement for consultation does not apply is for bats present in the living area of a dwelling house. This does not include the roof void, cavity walls, between floors or exterior finish. The greater protection thus afforded is in recognition of the special requirements of bats, which are highly dependent on buildings for roosting and breeding. The concentration of mature females in nursery roosts at the time of parturition and rearing the young makes them particularly vulnerable to various catastrophes. Although the provisions of the Act relating to bats were not implemented until 28 September 1982, the wide publicity from the beginning of that year resulted in a great increase in the number of enquiries received about bats and bat roosts. An indication of public interest is that over 30000 copies of a booklet about bats were given away from May to December that year. In addition to this publicity, aimed largely at the general public, efforts were made to bring the provisions of the Act to the attention of local government departments and commercial companies whose activities are likely to affect bats. Before the 1981Act, when only two rare speciesof bat were afforded legal protection (Conservation of Wild Creatures and Wild Plants Act, 1975), enquiries about bats were dealt with on an informal basis mainly by three of the authors and, to a lesser extent, by regionally based staff of the NCC, museums, local natural history societies and interested amateurs. Now that there is a legal requirement for

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consultation, a greater number of enquirers consult the NCC, either directly or by referral from another organisation, and records are kept of all enquiries and the advice given. This provides an opportunity to analyse the types and distribution of enquiries and examine the attitude of the public towards bats, which have always been held in rather low esteem and sometimes fear. These enquiries also provide a unique opportunity to gather information on bat distribution, status and biology as well as the positions of sites requiring extra attention and conservation measures, e.g. for rarer species. An analysis is presented of the returns for the first 20 months of operation of the scheme from May 1982to December 1983.

PROCEDURE FOR DEALING

WITH ENQUIRIES

Nearly all enquiries were received by telephone. A form was completed at the time of reception recording the name and address of the roost owner and a brief description of the problem. Often this single contact was all that was required as many enquirer’s problems could be quite easily resolved. In cases where a personal visit was likely to prove helpful, either by reassuring the enquirer or in gathering further TABLE 1 Enquiries Received by Conservation Organisations from 23 May 1982 to 31 December 1983 and the number of Visits Made to Roosts

ITE NCC Naturalists Trusts/Bat groups Museums Local government authorities Independent experts National Park staff MAFF Others Totals Visits to roosts made by NCC staff Visits to roosts made by volunteers Totals

1982

1983

Total

%

149 422 14 27 5 4 2 1 6 630 193 100 293

140 960 157 36 1 24 1 1 16 1336 240 438 678

289 I 382 171 63 6 28 3 2 22 1966 433 538 971

14.7 70.3 8.7 3.2 0.3 1.4 0.1 0.1 1.1 44.6 55.4

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information, visits were frequently made by either NCC staff or one of the many local licensedvolunteers from county bat conservation groups (Table 1). A booklet (Stebbings & Jefferies, 1982)explaining the biology of bats, the seasonalityof any problems and the reasonsfor conservation was sent or given to all enquirers. A questionnaire was also sent to some roost owners who were not visited, to obtain more information about their bat roosts. Where advice was requested,it was given on the basis of information received or as a consequenceof a visit. The advice was intended to alleviate, as far as possible, any problems experiencedby the enquirer and to ensure that any operation, such as the exclusion of bats, would be done in an approved manner. Advice of this nature could only legally be given by staff of the NCC or one of the authors (R.E.S), who was specially empowered to give advice on behalf of the NCC.

RESULTS The results of enquiries received from the various organisations concerned are given in Table 1. After eliminating those enquiries which were of a general nature, the remainder were first divided into domestic (those to which the ‘dwellinghouse’ defence in the legislation could be applied) and non-domestic, with two further minor categories. Domestic enquiries were then further divided into: 1.

Householders with bat roosts who intended no action to harm or disturb their bats. Usually the householder wanted further information about them. 2. Householders who initially wanted to take action against the bats (usually exclusion) but were persuaded to leave them undisturbed and allow them to return in future years. 3. Those who could not be persuadedto leavetheir bats permanently undisturbed and were provided with advice, usually about exclusion at the end of the breeding season,as required by the legislation. 4. Those who had already taken action against their bats before seeking advice or who requested that the bats be excluded immediately, usually on grounds of mental stress.

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Consultations about housesused by bats where repairs or alterations, which might affect the bats, were intended. Consultations about houses due to receive pesticide treatment. This was usually to control wood-boring insects but a few cases involving cluster-fly Polleniu rudis are included.

Requests for advice about bats in non-domestic buildings such as factories, shops, schools and churches were less common and were subdivided into: 7 8. 9.

Buildings used by bats where the bats or their roost were likely to be affected as the incidental result of repairs, alterations or maintenance. Any enquiry about bats in a church, whether or not any sort of action which would affect them was intended. Consultations about bats in buildings, other than churches,where general advice about the management of the bats was required.

Two minor categories were: 10. Reports of bats found, alive or dead, which could not be related to a roost site in the vicinity. 11. Enquiries about bats in domestic premises which could not be further categorised, either because insufficient evidence was available or action about the site was still continuing. The number of enquiries in each category is shown in Table 2. Enquiries about bats in domestic premises formed the largest category (87.4%) of which only 18.8% were related to house repairs, alterations or pesticide application (Table 2). Of the 1251 households reporting bats (categories l-4), 27.9% intended to take no action against them, 37.2% originally wanted the bats removed or excluded but were persuadedto leave them, 32.0% could not be persuaded to leave the bats permanently, though they agreed to wait until the recommended time before excluding them and only 2.9% either disturbed the bats before seekingadvice or insisted on immediate action. The reasonsfor advice being sought A randomly selectedsample of 100 enquiries from categories 2 and 3 (Table 3) showed that bat droppings were the main cause for concern. The fitting of deflector boards ensuresthat they do not fall in doorways

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TABLE 2 Categorisation of the 1966 Enquiries Received (See text for more details of the categories. The figures for 1982 cover only the last 8 months of the year) Category 1. Domestic: No action against bats intended 2. Domestic: Persuaded to leave bats undisturbed 3. Domestic: Provided with advice under the 1981 Act 4. Domestic: Bats excluded/killed before or after advice 5. Domestic: Repairs or alterations 6. Domestic: Pesticide application 11. Domestic: Unclassified/unresolved All domestic enquiries 7. Non-domestic: Proposal to carry out lawful operation 8. Non-domestic: Church with bats 9. Non-domestic: Other enquiry All non-domestic enquiries 10. Bats found: dead or alive Totals

1982

1983

Total

%

120 174 107

229 291 294

349 465 401

17.75 23.65 2040

14

22

36

1.83

58 28 36 537

86 151 109 1182

144 179 145 1719

7.32 9.10 7.37 8744

12

16

28

1.42

29 29 70 23 630

44 38 98 56 1336

73 67 168 79 1966

3.71 3.41 8.54 4.02

TABLE 3 Analysis of Sub-sample of 100 Enquiries giving the Reason for Advice being sought by Householders about their Bats Reason Droppings inside the property Droppings outside the property Bats flying or crawling in the house General fear of bats Concern that bats were causing damage Fear of numbers increasing greatly Noise Smell Fear of disease transmission to humans

Number (%) 20 23 16 15 11 5 4 3 3

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or on windows, while goods stored in lofts can be protected by the use of plastic sheeting. There is no record of diseasesbeing transmitted to man by bats or their droppings in Britain or Europe. The appearanceof bats in the living area of a housecould be attributed either to the bats finding a hole between their roost area and the living area or to young inexperienced bats flying through open windows. The former problem can be solved by blocking holes, such as where pipes run through a ceiling or cavity wall, and the latter by the temporary provision of netting over the windows. Fears of damage by bats are groundless as, unlike birds or rodents, bats do not make their own entrance holes, gnaw or bring in nesting material. Noise and smell can be a problem with large colonies but the former is only temporary and the latter usually indicative of some building defect which allows the accumulated droppings to become damp. Genuine problems of this type are relatively rare. Fears about numbers of bats increasinggreatly stem from the common belief that bats are similar to rodents. It is widely believed that bats live in houses all the year round and breed rapidly. Information about the seasonalnature of most bat colonies, and the slow breeding rate of not more than one young a year, was generally successfulin calming these fears. The most difficult problem to counter is an irrational fear of bats, which we found to be very common. In such casesit was advisable to stress the temporary and seasonal nature of most bat roosts and the fact that the bats would disperse naturally within a few weeks. In general, the organisations consulted were successfulin persuading householders to leave the bats undisturbed. Of the 866 householders originally requesting their removal but asking for advice as required by the legislation, 53.7% were persuaded to leave them permanently undisturbed: the remainder were persuded to leave them until the end of the breeding season (usually by September) and were given advice on how to exclude them in the approved manner..Thus the breedingage females and the young of the year were safe to seek another roost. In many casesthis second category of roost owners did nothing about excluding their bats for further seasonswhen they left as we said they would (Watson, 1985). A further 36 householders had already taken action before seeking advice or were so afraid of bats that they had made themselves ill and requestedimmediate exclusion on medical grounds.

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58'

I-

52'

Fig. 1. The numbers of enquiries about bats receivedfrom each 10 km square (100 km*) of the British National Grid. An asterisk denotes squares with more than 9 enquiries; the maximum is 14. The right hand axis gives the distance from the origin on the National Grid at 100km intervals and the left hand axis the approximate latitude.

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Distribution of enquiries The total number of enquiries about bats and bat roosts for each 10km national grid square is shown in Fig. 1. The distribution is biased in favour of southern and eastern England with some dense areas in the north-west Midlands. A decline in density and speciesdiversity has been recorded towards the north (Arnold, 1984), and this is reflected in the relatively small number of enquiries received from Scotland. *

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Fig. 2. The density of enquiries, expressed as enquiries per 100km*, for successive 1Okm wide ‘slices’ across England and Wales. A three point running mean has been used to reduce variation. The X axis gives the distance north from the origin of the British National Grid (see Fig. 1).

From Fig. 2, it will be seen that the peak enquiry rate per IO-km square is at about latitude 51”20’. By latitude 51”50’ the rate has halved, and by latitude 53”20’ it has fallen to a quarter of its peak value. Above latitude 54”10’ very few enquiries were received. Seasonality of enquiries The number of enquiries received each week for the period of the analysis is shown in Fig. 3. There is considerable similarity between the data for the two years, with a steady rise in numbers from May, a peak

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et al.

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,981

-

1983

/ Month

Fii. 3. The total number of enquiries received per week in the two years 1982 and 1983. Weeks are defined as groups of 7 days starting from 1 January with leap years ignored.

in mid to late July and a slow decline continuing till November. This pattern coincides with the bats’ breeding season;the young are born in June and July and begin flying in July and August. Most enquiries concerned the pipistrelle Pipistrellus pipistrehs, the most common species,in which the females usually form nursery colonies in house roofs from June till August. The sharp rise in the rate of enquiries in early July coincides with the time when the colonies are at their most active as the young begin to fly. species involved

In the majority of enquiries, the species of bat involved was not identified, either becausethe roost was not visited or it was inspected during the day when the bats were inaccessible.Positive identifications are shown in Table 4. The Table is dominated by pipistrelles and longeared bats (almost certainly all Plecotus auritus, as P. austriacusis very

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TABLE 4 SpeciesInvolved in the 628 Enquiries which were Positively Identified Species involved

(where i&nti$ed)

Pipistrelle Pipistrellus pipistrellus Long-eared Plecotus sp. Serotine Eptesicus serotinus WhiskeredjBrandt’s Myotis mystacinusjbrandti Lesser horseshoe Rhinolophus hipposideros Natterer’s Myotis nattereri Noctule Nyctalus noctula Greater horseshoe Rhinolophus ferrumequinwn Leisler’s Nyctalus leisleri Daubenton’s Myotk daubentoni Barbastelle Barbastella barbastellus Total number of identifications

No.

%

361 191 23 20 11 9 2 2 1 1 1 628

584 30-4 3.6 3.2 l-8 1.4 0.3 0.3 0.2 o-2 0.2

rare) which together account for 89% of identifications. A single daytime visit to a roost or examinations for droppings were both likely to underestimate the frequency of speciesthat tend to roost in inaccessible parts of houses, notably pipistrelles, and overestimate those species, such as long-eared bats, that are more frequently encountered in lofts. There was also a tendency for roost visitors to look more closely if they suspectedthat one of the less common speciesof bat may have been present. Thus it is likely that the frequency of pipistrelle roosts was underestimated and that of the other species, including long-eared, overestimated. It is a reasonable supposition that almost all large bat colonies reported during the summer months are pipistrelles. The two most abundant speciesof bats, pipistrelle and brown longeared, show rather different seasonalpatterns (Fig. 4), the former being recorded in houses over a much shorter period of the year than the latter, which are occasionally recorded during the winter. Colony size The visitors to roosts were asked to count the numbers of bats in the colony whenever possible, and the questionnaire sent to many owners also requestedthis information. Information about numbers was often available even when species identifications had not been made. For pipistrelle colonies, where a count was available, the mean colony size

A. J. Mitchell-Jones et al.

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Fig. 4. The number of enquiries received each week for pipistrelle and long-eared bats, plotted as percentages of the total number received for that species over the study period. A percentage figure had been used as the sample sizesfor the two specieswere very different (see Table 4). Weeks are defined as in Fig. 3.

was 35.2 (SE 2.12) and for long-eared bats, 21-l (SE 5.6). The mean colony size for all colonies, identified or not, was 32.2 (SE l-04). This is close to the mean colony size for pipistrelles, the most abundant species. DISCUSSION Following the 1981Act, the greatest increase in the number of consulwas expected to come from the remedial timber treatment and building trades who are, on the whole, concerned to conform to legal requirements. At least 500000 properties are treated each year for woodboring insect infestations, so the small number of consultations in this category is surprising. However, the Act did not come into effect until 28 September 1982and it took some time to bring its provisions to the attention of the companies concerned.The great increasein the number of consultations in 1983 (Table 2) is an indication of the growing tations

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awarenessof these companies. This should reduce one of the greatest threats to bats roosting in housesas the insecticide most commonly used at present, lindane, otherwise known as gamma hexachlorocyclohexane (HCH) or gamma benzene hexachloride (BHC), is lethal to bats breathing the aerosol or resting against treated timbers (Racey & Swift, 1986). The NCC is now able to advise on the use of a less toxic insecticide, a synthetic pyrethroid, applied at the least damaging time, usually the spring or autumn. The opportunity for persuasion provided by the special clause in the Act resulted in many bats being allowed the continued use of their traditional roost sites. By using the figure for the mean colony size, it can be estimated that approximately 15000 bats were left permanently undisturbed, whilst another 13000 were permitted to dispersenaturally before their roost accesswas obstructed. In addition, many more bats were saved from the toxic effects of remedial timber treatment or f&m disturbance due to badly timed building or repair operations. The recording scheme has also collected much useful biological information, some of which could not easily be obtained in other ways. An additional 626 locality records for 11 specieshave beencollected for the mammals recording scheme together with information about the relative frequency of these speciesin houses. It is tempting to interpret the distribution of enquiries (Fig. 1) as reflecting accurately the density and geographic distribution of bats, but this is an oversimplification. The distribution map will also reflect the distribution and density of the human population and human attitudes towards bats, which may vary geographically, with perhaps greater concern about the imagined effects of bats on buildings in highly urbanised south-east England, where property prices are higher and the urban population is unfamiliar with bats. This may account for the high density of enquiries for the area immediately surrounding London. The centre of London itself shows up as a hole in this densearea. It is known to be inhabited by bats (Hooper, 1981)but the lack of enquiries is most likely due to a low number of continually inhabited domestic buildings, though a low bat density due to low insect biomass or pollution is possible. Other local features which do show up on the map are the relatively few enquiries from high ground in Wales and Devon, which may reflect both a low density of houses and bats and perhaps a tolerant rural community. From the biological point of view the most interesting

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feature is the rapid decline in enquiries north of the Mersey and Humber rivers. This cannot be due to a lack of houses as there are many areas of high human density in the north. It seemsunlikely that tolerance to bats would change so suddenly, so a sharp decreasein bat density seems a possibility at this point. Scotland is known to have fewer speciesof bats than either England or Wales (Arnold, 1984). ACKNOWLEDGEMENTS Studies of this nature are almost entirely dependent on information being collected and submitted by members of staff of the NCC and members of Bat Groups. We are grateful to the many people who have contributed in this way. We also thank John Line for drawing the di&ibution map. REFERENCES Arnold, H. R. (1984). Distribution maps of the mammals of the British ZsZes.Abbots Ripton, Huntingdon, Institute of Terrestrial Ecology. Hooper, J. H. D. (1981). The use of an ultrasonic receiver to obtain distribution data for pipistrelles and other bats within the London area. Lond. Nat., 60,4763. Racey, P. A. & Swift, S. M. (1986). The residual effects of remedial timber treatments on bats. Biol. Conserv., 35, 205-14. Stebbings, R. E. & Jefferies, D. J. (1982). Focus on bats, their conservation and the law. London, Nature Conservancy Council. Watson, A. P. (1985). Follow-up survey of 1983 bat enquiries. Peterborough, Nature Conservancy Council. (Unpublished report.)