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By far the most common and least disruptive way of estimating bat numbers in summer roosts is to count the bats leaving the roost at sunset. The most successful period over which to make counts so that yearly comparisons can be made is when the colony is at its most stable. Maternity colonies continue to grow into early June as pregnant females arrive from pre-maternity roosts. Later in the summer young bats begin flying and counts at this time will include both adults and young. Just prior to birth of the young, a peak in adult female numbers is reached and many or all of the adult females emerge every night. In general, young are born between mid- to late June inmost species, although there is variation from year to year. Counts in late
May to mid-June are likely to reflect the most

stable numbers. This is the time that is recommended by the National Bat Monitoring Programme (see
Walsh et al., 2001; Appendix When attempting to count a colony for the first time, it is important to establish the number and location of access holes and this may require several people surrounding the roost. Once all access point have been discovered then fewer surveyors maybe required for future counts. Assign observers to a specific exit or field of view because often two exits close together maybe counted simultaneously.
Be in position at the roost about 15 minutes before sunset (earlier on overcast evenings) and listen for the sound of bats moving at access holes or for squeaks as bats jostle for position. Poor weather conditions with overcast skies and rain may delay emergence and particularly bad conditions should be avoided in case bats choose to abandon foraging and remain inside the roost. Remain counting until at least 10 minutes after the last bat has emerged.
As a general guide, bats may begin emerging from just before sunset onwards. The noctule is an early emerging species, whilst Natterer’s and long-eared bats are late emerging (up to 40 minutes after sunset).
Do not shine white lights directly on the roost exit because this can often delay or prevent emergence.
Excess noise, particularly ultrasound from keys,
coins or nylon jackets, may disturb bats and inhibitor delay emergence. Emergence counts are most effective when departing bats are silhouetted against alight background (normally a clear sky or sometimes alight coloured wall. It is best to observe from the side of the emergence point(s),
rather than from in front. Sometimes the structure of the roost and behaviour of the bats means this is not possible and the additional use of a bat detector is always recommended.
The behaviour of bats at emergence varies between species. Some, such as noctules, tend to fly off fast and direct to foraging grounds while others, such as the horseshoe and Natterer’s bats, may exit and reenter the roost several times before departing for foraging grounds (called light sampling’
behaviour), which makes counting more difficult.
In all cases, a running total of both exits and entries should be recorded so that a final net emergence figure can be calculated. This is essential when several exits are being counted simultaneously, so that bats that emerge from one and subsequently
re-enter at another maybe properly accounted for.
A small tally counter is useful for clicking up bats as they emerge. Automatic counting equipment or video equipment at roost exits can be a useful substitute for observers, although even the most sophisticated systems have their problems. Most automatic counting systems are based on one or more infrared light beams that are broken as a bat emerges from the roost. A single beam is unable to distinguish between emerging and returning bats but beam breaks should be proportional to the number of bats emerging/returning and so could be calibrated by combining beam counts with observer counts. More sophisticated systems use two sets of beams so that emerging and reentering bats can be counted separately. Both types of system are unable to cope with bats that emerge without breaking the beams or when two bats break the beam simultaneously.
Problems also arise when two or more species are using the same roost or if insects fly close to roost access points. When using automatic systems results must be crosschecked with simultaneous visual checks to identify errors or consistent biases. Counts of bats within summer roosts are generally more difficult, cause more disturbance and are less accurate than emergence counts. One or two visits to a breeding roost in a season would probably be acceptable provided that every care was taken to keep the disturbance to the minimum. The exception to this is for counts of nonflying young, which maybe counted on a weekly basis once all the adults have left to forage. This method is mainly applicable to horseshoe bats.

Health and safety in bat work
Catching bats
Ringing and marking
Public relations
Conserving and creating bat roosts
Bat workers manual 09acknowledgements
Bats and the law
Law enforcement – gathering evidence
Convention on the conservation of
Public inquiry confirms importance of lesser horseshoe bat roost
Taking bats into captivity
Advice to the public who find grounded bats
Advice on bats and rabies
Dust and insulation
Wasp, bee and hornet nests
Survey and monitoring
Day surveys of potential roost structures
Case study – bats in barns survey
Case study – the bats in churches project
Bats and echolocation
Bat detectors
Basic equipment required:
Sonogram analysis
Extraction from hand-nets
Figure 4.1hand-nets. polythene around the lip prevents bats climbing out.figure 4.3
Single-pole flicking
Chapter 4 c atching bats44two-pole flicking
Chapter 4 c atching bats463
Testicular descent
Chapter 5 examining bats50figure 5.1
Parturition and lactation
Fur colour and texture
Wing span, and head and body length
Mites, including ticks (acari)
Bat-bugs (hemiptera, cimicidae)
Fleas (siphonaptera, ischnopsyllidae)
Bat-flies (diptera, nycteribiidae)
Rabies surveillance
Chapter 5 examining bats56sending dead bats by post
References and further reading
Handling, releasing and keeping bats
Moral considerations
Adultstemporary debility or injury likely to heal
Permanent captives
Bat conservation trust - guidelines on bats in captivity
Insects and substitutes
Vitamins and minerals
Weaning and rearing orphaned bats
The role of a bat group
The bat conservation trust
Bats on the internet
Bats in the living area
General fear of bats
Damage to buildings
Transmission of disease
Interior design fora huge roost of (smelly) bats
Legal position (simplified)
Outside the breeding season
Insects in droppings
Speciesnumber of roosts
Summary – exclusion of bats
Summary – visit to householders who have discovered bats
Security alarm systems in buildings
Timber treatment, pest control
During breeding season
If bats are torpid
Fungicidescommon name
If bats are active
Outside breeding season
Fusible link shutters
Case study - window and lintel replacement
Case study - roof refurbishment
Case study – timber treatment and roof renovation
Excessive disturbance
Destruction, maintenance or change of use
Chapter 11 conserving and creating bat roosts112figure 11.1
Grade b sites without protection.
Grade 4 (many sites)
Grade 1 (fewer than 10 sites)
Railway tunnel enhancement
Cave construction
Manipulation of airflow and temperature
Reopening of blocked sites
Provision of additional roosting points
Chapter 11 conserving and creating bat roosts122figure 11.5
Figure 11.5 (continued)
Converting a pillbox for bats
Bat conservation code
Wildlife and countryside act 1981 &
Tree preservation orders
Maintaining roosts
Creating roosts
Case histories of bridge maintenance works
Examples of roost creation within bridges
Appendix 1140figure a1.1
Appendix 1142figure a1.1
Appendix 3 9
Grid reference.
Biological records centre single species card
Monitoring methods
Hibernation counts
Bat speciessc
Appendix 4150participation and experience required
A selected bibliography
A european bats – identification,
C children’s books
Appendix 5154d journals, magazines and newsletters
Bat research news
Useful names and addresses
The environment and heritage service
Department for environment, food and rural
Non governmental organisations
National association of mining history
The national trust
Subterranea britannica
Equipment suppliers
Pettersson elektronik ab
Bernies cafe and caving supplies
Watkins and doncaster
Holohil systems ltd
Titley electronics
Jacobi jayne & co
Mealwormslive foods direct ltd
Bat workers training syllabus
Circumstances requiring consultation
Licensinglicensable activities
Appendix 7164other licences
Bat biology and ecology
Basic ecology
Bat conservation
Persecution and intolerance
Presenting bats to the public
Safety underground
Appendix 7168training checklist
Model risk assessment for entry into disused mines (cont)
Model risk assessment for initial entry into derelict and dilapidated buildings and structures
Model risk assessment for initial entry into derelict and dilapidated buildings and structures (cont)
Model risk assessment for entry into confined spaces
Model risk assessment for entry into confined spaces (cont)
Health and safety at work etc act 1974
Health and safety legislation
The carriage of dangerous goods
References legislation
Appendix 9178for laboratory use only

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