Looking for bat roosts in trees Marc Van De Sijpe Natuurpunt vzw vleermuizenwerkgroep

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1 Looking for bat roosts in trees Marc Van De Sijpe Natuurpunt vzw vleermuizenwerkgroep Methods and materials Ear Eye Batdetector Night vision Thermal imaging Torch Tree cam Endoscope Telemetry 1

2 Ear audible sounds of bats Audible - High pitched - Shrill, scraping noise Noisy - Audible from distances >20 m (Noctule) Who? - Noctule - Daubenton s bat - Others? When? - Early morning - During the the day - Late evening Bats silent? Knock on the trunc and they will shout back to you! Audible sounds of Noctules in a red oak. Recording around sunrise when all bats are returned to the roost 15 khz 15 khz Noctules Noctules Noctules Noctules Noctules khz Songbirds Songbirds Noctules 5 khz Songbirds Songbirds Songbirds Songbirds Songbirds Cock-crowing Crows Cock-crowing Crows 2

3 Eye visual traces of bats Dark stripes - Excess excrements from large bat roosts Be careful! Many dark stripes are in fact rotten debris Bat droppings Adhering to bark and leaves below the entrance Bitten moth wings Accumulating below the roost (Long-Eared bats) Swarming Late species: in midsummer between 5:00 and 6:00 Batdetector ultrasonic sounds of bats Commuting - Evening : upstream - Morning : downstream Swarming - Early species (4 AM) - Late species (5 AM) - Midnight (e.g. noctules) Bats in the roost - Afternoon detector survey - Daubenton s bats (25 khz) Identification - Heterodyne / Time exp - Mixed roosts! 3

4 Tracking Daubenton s bats with a batdetector Commuting routes & swarming at the roost Night vision visual observations of bats in the dark Types - Active infrared - Image intensifier Zoom - Morpohology of the bat - Surveying remote spots Performance - Viewing in the darkness - Viewing in twilight Accessories - Tripod mount - Video output Use - Bat behaviour - Discovery of the entrance - Counting bats 4

5 Brown long-eared bats emerging from the roost in a natural cavity in an oak. (colony size: 9 bats height ca 6 m) Noctules emerging from the roost, a woodpecker hole in an oak. (colony size : approx 20 bats height ca. 6 m) 5

6 Noctule emerging from the roost, snapshots from a video recording Brandt s bat emerging from the roost behind loose bark of a dead oak. (colony size : 19 bats height ca 3 m) 6

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8 Thermal imaging heat sources from bats Heat radiation - Through the entrance - Through the bark Weather - Overcast & cool weather = best result - Beware of sudden changes of ambient temperature Where? - Cavities in living trees - Cavities in dead trees - Behind loose bark Use - Detecting roosts during the day - Counting emerging bats Daubenton s bats roosting during the day in a woodpecker hole in a beech (colony size : 91 bats height ca 3 m) Thermal image taken at a moment when there are no bats present Thermal image taken at a moment when the bats are in the roost. Heat radiates through the entrance 8

9 Daubenton s bats emerging from the roost, a woodpecker hole in a beech (colony size : 61 bats height ca 3 m) Daubenton s bats roosting in the afternoon in a woodpecker hole in a red oak (colony size : 39 bats height ca 8 m) Thermal image taken a distance of 20 m. Heat dissipates through the entrance. Cool afternoon (10 C) in the middle of May. 9

10 Daubenton s bats roosting in the afternoon in a woodpecker hole in a red oak (colony size : 39 bats height ca 8 m) Noctules roosting during the day in a woodpecker hole in a dead oak (colony size : 23 bats height ca 8 m) Thermal image taken at sunrise (20 C ambient temp) Thermal image taken at sunset (25 C ambient temp). 10

11 Heat radiation from a woodpecker hole in a red oak in January (temp -12 C). The heat probably came from a woodpecker roosting in the hollow tree. We have not yet found hibernating bats in trees with thermal imaging. Brown long-eared bats roosting in a woodpecker hole in a dead alder (colony size : 12 bats height ca 5 m) 11

12 Roost of 24 Brandt s bats and 1 Nathusius pipistrelle behind loose bark of a dead oak on a rainy day. Colony present behind the bark No bats behind the bark anymore Solitary Barbastelle roosting behind loose bark Pictures : Alex Lefevre The heat of the bat seen from below, the heat source was also visible from the side, through the bark 12

13 Torch looking in tree cavities Use - Fissures in trees - Behind loose bark Example - Hibernating Daubenton s bats and Longeared bats in a fissure in a beech Tree camera looking into tree cavities System - Camera pointing upwards - Visible light or infrared - Monitor at ground level - Extended pole Use - Inspection of tree cavities - Detecting bat roosts - Species identification 13

14 Observing a summer roost of 41 noctules in a red oak, a woodpecker hole at a height of 8 m Video : Bob Vandendriessche Working with a tree cam in winter Pictures : Erik Naeyaert 14

15 Endoscope looking into tree cavities System - Manual inserting camera in cavity - Visible light Use - Inspection of tree cavities - Detecting bat roosts - Species identification Telemetry tracking individual bats System - Catching the bat - Attaching a transmitter to the bat - Release of the bat - Tracking the bat with receiver/antenna Use - Day roosts - Temporal night roosts - Species identification 15

16 Picture : Pieter Blondé 13/12/2014 Capturing bats in mist nets Identifying species, sex, age Pictures : Bram Conings & Luk Dombrecht Tracking bats with antenna and receiver Bat equipped with transmitter Picture : Daan Dekeukeleire 16

17 Example : Hoge bos (Ypres), 45 ha Predominanty oak, red oak and beech Between 2001 and 2014, 15 roosts were found of Noctules, Daubenton s bats, Brandt s bats, Brown Longeared bats & Nathusius pipistrelle Woodpecker hole Loose bark Natural tree hole Roost found with batdetector (swarming) Roost found with thermal imaging Roost found with unaided ear (audible sounds) Advantages and disadvantages of the various methods Picture : Rollin Verlinde 17

18 Price Efforts * Ear * Eye * Torch * Batdetector * Endoscope * Night vision * Thermal imaging * Tree camera * Telemetry * Ear * Eye * Thermal imaging * Night vision * Batdetector * Torch * Endoscope * Tree camera * Telemetry Disturbance Identification * Ear * Torch * Telemetry * Ear * Eye * Endoscope * Tree camera * Eye * Batdetector * Tree camera * Endoscope * Thermal imaging * Night vision * Telemetry * Torch * Bat detector * Thermal infrared * Bat detector * Night vision Large areas Daytime work * Telemetry * Ear * Eye * Torch * Batdetector * Endoscope * Night vision * Thermal imaging * Tree camera * Ear * Eye * Thermal imaging * Torch * Endoscope * Tree camera * Telemetry * Batdetector * Night vision Weather independency Hibernating bats * Ear * Eye * Torch * Tree camera * Endoscope * Telemetry * Batdetector * Night vision * Thermal imaging * Torch * Endoscope * Tree camera * Ear * Eye * Thermal infrared * Night vision * Telemetry * Batdetector 18

19 Solitary bat * Telemetry * Thermal imaging * Ear * Eye * Torch * Batdetector * Endoscope * Night vision * Tree camera Combining different methods Choice depending on the field situation Look for other methods Thank you for your attention! Special thanks to: Natuurpunt Michel Barataud Vleermuizenwerkgroep Provinciebestuur West-Vlaanderen Sylvie Giosa Agentschap voor Natuur en Bos Alex Lefevre Bob Vandendriessche Paul Voet Erik Naeyaert Dieter Vandenbogaert Daan Dekeukeleire Wout Willems Johan Duyck Frank Van Gorp Rollin Verlinde Bram Conings Joachim Calcoen Jan Ranson Olivier Dochy Floris Verhaeghe Erwin Verfaillie Erik Malfait Mario Manhaeve Daan Verschelde Joost Vandenberghe Luk Dombrecht Kristof Goemaere Pieter Blondé Paul Wittewrongel Pierre Hubau Kristof De Ketelaere Hub Goertz 19