Two bat schemes that didn’t make it

NL 1990-1999

Rombout de Wijs

Schemes for monitoring bats

• Hibernacula

• Colonies/summer roosts

• Point & line counts for passing bats

• Transect counts advertising bats

Schemes for monitoring bats

• Hibernacula

• Colonies/summer roosts

• Point & line counts for passing bats

• Transect counts advertising bats

Point/line counts

• transects non-random selected (near home)

• 1 main type of habitat

• 4 km (walk) to 15 km (bike)

• 20 points and 20 lines in between

• minimum distance between points 200m (walk) or 400m (bike)

• points close to water if possible

• at least some suboptimal points

Transect 7: Schaep & Burgh

Point/line counts

• detector tuned to 42 kHz• 3 minutes at points• variables at each point/line:

– presence– maximum– total # passes

• start at 1-1.5 hr after sunset• temperature > 8°C

Point/line counts

• counting each month April-September

• in middle of month (10-20th)

• since 1997 only in May, July and August and only at points

• 17 transects in total

• mainly central NL

km bike walk urban agric. wood water1 Almere Stad + Haven 13,5 + + + +2 Almere Lepelaar + Vaart (15 pnt) 15 + + + + +3 Almere Buiten eo. ? + + + +4 Harderwijk A, bebouwde kom ? + + +5 Harderwijk B, westkust ? + + +6 Leuvenumse Bos 9 + + +7 Schaep&Burgh,Bantam,Boekesteyn 5,8 + + +8 Vlaardingen 8,8 + + + +9 De Ruyven 8 + + + +

10 Ackerdijkse Plassen 4 + + + +11 Rottemeren (15 pnt) 7 + + +12 Overijssels Kanaal 12,4 + + +13 Zoetermeer (16 pnt) 11 + + +14 Haagse parken 3 + + +15 Culemborg 14 + + +16 Singraven 5,5 + + +17 Spaarnwoude 16,5 + + +

1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 n1 6 4 6 6 6 6 6 3 3 3 102 5 4 5 5 5 6 4 3 2 93 5 4 24 5 6 5 6 2 55 5 6 1 2 1 56 5 6 5 6 2 57 6 6 6 3 3 3 68 5 7 4 4 3 59 6 5 210 6 6 6 311 7 6 6 3 3 512 2 2 3 313 4 5 3 3 414 5 4 3 315 3 3 216 2 117 3 1

2 2 6 6 10 13 11 10 9 2

• Number of counts/year

Mmys Mnat Mdau Mdas Ppip Pnat Nnoc Eser Paur n1 + + + + + + 62 + + + + + + 63 + + + + + + 64 + + + + + + + 75 + + + + + + 66 + + + + + + + + 87 + + + + + + + + 88 + + + + + + 69 + + + + 410 + + + + + 511 + + + + 412 + + + + + + + + 813 + + + + + + 614 + + + + + + 615 + + + + + 516 + + + 317 + 1

3 1 12 12 17 16 14 15 5

• Species observed at transects

More details methodology (results from the 1999 paper)

• variables strongly correlated, but sum of passes showed much variation. Risk of saturation in presence

• results points and lines strongly correlated, but variation lower at points

• no difference in indication value of mean and maximum value per season

• species showed different seasonal variation, therefore 3-6 counts necessary: later analysis showed 3 counts sufficient

• number of transects needed is 100 for detecting differences between years of 20-40%, but rule of thumb CBS adopted: 25-50 transects for detecting trends over 5-10 years (for each stratification layer)

• Trends 6 species using model TRIM and using variable Presence

0

50

100

150

200

250

300

92 93 94 95 96 97 98

Mdau

Ppip

Pnat

Nnoc

Eser

Mdas

Why giving up?

• insufficient # transects• insufficient # volunteers, in spite:

– much effort to arouse interest (newsletter, talks)– making field work easier: only in 3 months (was

6) and only at points (was including lines)

• financing stopped

Scheme abandoned

Schemes for monitoring bats

• Hibernacula

• Colonies/summer roosts

• Point & line counts for passing bats

• Transect counts advertising bats

Schemes for monitoring bats

• Hibernacula

• Colonies/summer roosts

• Point & line counts for passing bats

• Transect counts advertising bats

Transect counts advertising bats

• non random selected (near home)• 2.5 - 8.0 km• walking or cycling at 5km/hr• 6 counts 15 Aug. - 30 Sept. • start 1 hr after sunset • temp. > 8°C• detector tuned to 20-25 kHz, Pnath checked at 40 kHz

(for 2nd part of call)• observations drawn on maps

Transect counts advertising bats

• end of season: clustering observations to “territoria”

• when flying: different individual when >100 m

• variables: – maximum at 1 count during season– mean of counts during season

• 41 transects in total

• 23 counted 3 years or more

• mostly transects• 3 area’s• mostly urban

km line area urban wood park1 Almere-Haven 3,8 + +2 Schaep & Burgh, Boekesteyn 3,6 + +3 Geleen-Zuid 6,3 + +4 Harderwijk 1: Slingerbos 5,7 + + +5 Harderwijk 2: Tweelingstad 5,6 + +6 Harderwijk 3: Stadsweiden 5,4 + +7 Harderwijk 4: Zeebuurt 5,7 + +8 bebouwde kom Dongen 5,5 + +9 Vlijmen-dorp 5,0 + +

10 Oudere en minder oude nieuwbou 4,6 + +11 Hellingbos 2,5 + +12 Leersum 6,2 + +13 Wageningen + +14 Renkum 2,7 + + +15 Ziekenhuis Duin en Bosch (NH3) 2,4 + + +16 Epe + +17 Brummen + +18 Schagen I 6,5 + +19 Wageningen C + +20 Wageningen A + +21 Wageningen B + +22 Schagen II (NH9) 2,2 + +23 Schagerbrug (NH11) 3,1 + +24 Egmond a/d. Hoef (NH5) 2,9 + +25 Bergen-Zuid (NH1) 2,1 + +26 Bergen-Centrum (NH4) 3,4 + +27 Spanderswoud-Zuid (NH34) 1,9 + +28 Spanderswoud-Midden (NH35) 1,6 + +29 Bussum (NH40) 3,8 + +30 Ilpendam (NH25) 2,1 + +31 Muiderberg (NH45) 2,9 + + +32 Muiden (NH46) 3,6 + + +33 Oldenaller 50,0 + +34 Landgoed de Braak 30,0 + +35 Kwadendamme 2,6 + +36 Dorp Beetsterzwaag 8,0 + + +37 Horst 4,0 + +38 Kasteelse Bossen 4,0 + +39 Plantage Culemborg 2,5 + + +40 Zeeheldenbuurt + +41 Bergum 8,0 + + +

• first 2 years experimental• several 1-2 years only

1990 1991 1992 1993 1994 1995 1996 1997 1998 19991 1 5 6 6 6 5 4 4 2 2 102 4 4 5 4 3 2 63 27 8 5 4 5 54 6 6 6 5 5 4 4 75 6 6 6 5 5 3 4 76 6 6 6 5 5 4 4 77 6 6 6 5 5 3 4 78 4 4 4 3 4 59 6 6 4 4 4 510 4 6 6 5 4 4 4 5 811 4 7 5 5 5 4 612 6 113 6 114 3 6 215 4 13 4 4 4 4 5 716 3 117 4 118 4 119 19 5 220 7 121 3 122 4 6 4 5 423 4 4 4 424 4 1 4 2 4 525 4 2 2 3 426 4 3 2 3 427 3 3 3 328 3 3 3 329 5 130 1 1 6 331 3 3 232 4 2 233 4 134 8 135 3 136 6 4 7 337 3 3 238 4 139 6 6 6 340 6 3 3 5 441 4 5 2

2 10 16 18 24 22 17 16 13 6

0

10

20

30

40

Pspec Ppip Pnat Nnoc Eser Paur

• species present in 41 transects

0

20

40

6080

100

120

140

92 93 94 95 96 97 98 99

Ppip n=32

SE+

SE-

• results from Pnath and Nnoc inaccurate

• results from Ppip better

• trends similar to PLC

0

50

100

150

200

250

300

92 93 94 95 96 97 98 99

Pnath n=23

SE+

SE-

0

50

100

150200

250

300

350

92 93 94 95 96 97 98 99

Nnoc n=12

SE+

SE-

Why giving up?

• insufficient # Nnoc

• insufficient # volunteers

• does not add much to PLC

• financing stopped

Scheme abandoned

Should we restart “PLC”?

• need of monitoring data on Nnoc and Pnath

• need of data other species in summer, especially when not counted in colonies

• in 1996

Hib Col Adv.m. Point/line TotalRhinolophus ferrum-equinum 1 1Rh. hipposiderosMyotis mystacinus/brandtii 165 4 2 171M. emarginatus 22 1 23M. nattereri 92 1 93M. bechsteiniM. myotis 13 13M. daubentonii 242 4 11 257M. dasycneme 36 22 11 69Pipistrellus pipistrellus 23 127 19 14 183P. nathusii 1 14 14 29Nyctalus noctula 5 6 11 22N. leisleriEptesicus serotinus 5 61 14 80Vespertilio murinusBarbastella barbastellusPlecotus auritus 255 19 4 278P. austriacus 1 3 4

Hib = wintercensus hibernaculaCol = colonie countsAdv.m.= counts of advertising malesPoint/lines = counts on routes with

points and lines

Better prospects now?

• Atlas project longer ago, so more motivation?

• better awareness of need of data??

• better methods?– easier, so more volunteers?– less variation, so less counts needed?– better equipment, automatic registration?

New methods, new discoveries?Let’s face the challenge of a new start!