tussenDuin & Dijk

Connection and defragmentation

Nature in Noord-Holland. Volume 17 3 ● 2018 Ecoducts, vital to soil fauna

● The tree-stumps on the Zandpoort, February 2016. Photo: M. Boeken.

Since 2014, researchers have been studying the use of wildlife crossings or ecoducts within the Zuid-Kennemerland National Park. From 2015, these efforts have included a study of the use of ecoducts by ground and other soil fauna. What has happened since and what are the first results?

● Figure 1. Location of the ecoducts within Zuid-Kennemerland national park.

18 ● 3 Ecoducts, Michiel Boeken ● Figure 2. Location of the ten series of traps on and around Ecoduct Zandpoort.

●  bipustulatus. Photo: M. Boeken.

Pitfall traps (4%) designed to kill and preserve Sample sites The first study into ’ use of the trapped animals quickly. The In order to get a good overview of the ecoducts in the Zuid-Kennemer- addition of some washing-up liquid the original species composition land National Park was initiated in will break the surface tension and and abundance, the decision was 2014 (Van der Spek et al., 2017; prevent the animals from escaping. made to place a series of traps on figure 1). In March 2015, a second This makes this method not very both sides of Ecoduct Zandpoort, in project studying the use of the then -friendly, but, between ani- non-degraded woodland or thickets 1-year-old Zandpoort ecoduct by mals eating the bait and escaping, (series 1 and 8) as well as in ex- ground beetles and other soil fauna ‘dry’ traps provide only anecdotal posed dune grassland (series 2 and went underway. According to what evidence. Furthermore, with this 7; figure 2). Additional series were is now considered a standardised method, the traps would have to be dug in on both access routes (series method, to this aim, five pitfall emptied at least once every week, 3 and 6) and on the ecoduct proper traps with a diameter of 8.5 cm are while traps with the fluid only need (series 4 and 5). From 2016, addi- dug into the soil across a more or to be emptied every two (or three) tional series were placed in the so- less homogeneous environment and weeks. In order to prevent verte- called ‘stobbenwal’ structures (with equipped with a roof to prevent the brates from getting caught in them wood and tree roots) that had been rain and wind from entering. as well, the traps are also covered created at that time (series 9 and The traps are positioned in a with pieces of chicken wire, which 10). At the request of the Province straight line at 5 m intervals, which keeps larger animals (e.g. adult of Noord-Holland and PWN, from should more or less even out any toads, mice, lizards) from falling the end of April, yet more series terrain variation. The containers into the fluid and climbing out of traps were positioned around are lined with a layer of formalin again. the sites of the future ecoducts of ▶

3 ● 19 ● Philoscia muscorum. Photo: Bert Pijs.

Duinpoort and Zeepoort. Similarly to the Zandpoort situation, here too on either side, a series of traps was put in woodland or thicket and an additional one in dune grassland. In 2017, the series around the Zee- poort were doubled to get a better sense of the initial situation, and, once it became possible (in early July), five series were placed on the new ecoduct: three in the bare soil and two in ‘stobbenwallen’. Every two weeks, all the traps were emp- tied and the captured animals for 70 each series collected and identified. 60 60 60 Ground beetles and more 55 49 The focus initially was on the 50 47 ground beetles that were caught. 42 42 39 38 38 But of course many more animals 40 36 2015 ended up in the traps, and it would 31 31 29 be a shame to throw these away 30 2016 25 26 unseen. Many of these other species 23 2017 can also provide information on 20 the impact and use of the ecoducts. That is why all woodlice (Isopoda) 10 have also been identified and count- ed, as were centipedes (Chilopoda), ferrugineus 0 millipedes (Diplopoda), harvestmen10 Oldoud SZ ecoductdek 8 stobben stobben ecod.+stobbendek+stobben oudold N ZandpoortZandpoort (Opiliones), wolf spiders (Lycosi 8 (1, 2) (3-6) (9, 10) (3-6, 9, 10) (7, 8) totaaltotal dae), ants (Formicidae), cock- 6 roaches (Blattodea) and other6 ● Figure 3. Number of ground beetles that were caught in the 2015 different sub-areas on and4 around Zandpoort in 2015-2017. groups of invertebrates. Additional4 - Numbers in brackets refer to the series of traps.. 2016 ly, as several experts were interested 2 2017 in material, for instance rove2 beetles (Staphylinidae), snout beetles0 0 (Curculionidae) and wasps (Hyme1 - 2 found3 4 quite5 6 generally7 8 9 or10 only occur1 2 mostly3 4 of5 use6 to7 the8 latter.9 10 To more noptera, a number of varieties) were locally. sensitive animals like collected as well. A large amount of On a new sand body such as the (Arthropoda) with all their senses, data has been collected in this way sand forming the base of the a strip of tarmac with a completely over the last couple of years. ecoduct, the first animals that are different temperature, humidity lev- expected to appear are beetles (Co- el and smell may easily become an Expectations leoptera) and of course especially insurmountable obstacle. In a frag- In this article we will focus main- the strong flyers among the species. mented area such as the Zuid-Ken- ly on the developments on the Among these may be species nemerland dunes, populations Zandpoort ecoduct, with the data without a clear preference for any of slowly spreading species may from the baseline studies around type of terrain, but also species easily face extinction if no recoloni- Duinpoort and Zeepoort being used that live on open sand specifical- sation can take place. These dunes to assess the variation in results ly. Non-flying species are usually feature some species that are very on both sides of the ecoduct. The more bound to a particular biotope rare in the rest of the . data from the other series of traps and would be expected to appear It is therefore important for any also serve to give an impression once more vegetation has sprung ecoduct to become an integral part of whether certain species are up. A wildlife crossing is therefore of the dune ecosystem and feature

20 ● 3 Leistus ferrugineus Panagaeus bipustulatus 10 8 Leistus ferrugineus Panageus bipustulatus 8 6 6 2015 4 4 2016 ● Masoreus wetterhallii. 2 2 2017 Leistus ferrugineus Panagaeus bipustulatus Photo: Udo Schmidt. 10 0 8 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 8 6

6 ● Figure 4. Catches for two types of ground beetles (left: 2015 Leistus ferrugineus, right: Panagaeus4 bipustulatus) that 4 use the tree-stumps (series 9 and 10) in 2015-2017. 2016 2 2 2017 0 0 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

the same variety of biotopes (open taking into account the dry and rela- not placed on open sand. A large sand, dune grassland, thickets). tively barren terrain. In comparison: number of species is restricted to Only that will allow the species in the whole Amsterdam Water this kind of open sandy habitat; in that would take several generations Supply Dunes area, about half of addition, beetles can walk much to cross the ecoduct (some smaller the more than 300 Dutch species faster on sparsely vegetated sandy ground species (Carabidae) were caught in the period between terrain, so they have a greater only travel 50 m per generation!) 1974 and 2005 (Baeyens et al., chance of ending up in a trap. Not to find food and the conditions they 2007), and these included a large surprisingly, many of the beetles need to reproduce. number of species that are only caught on the ecoduct were flying, found in humid surroundings. sand-loving species, such as the Results In 2015, more than a year after northern dune tiger beetle (Cicin- In the past three years, 70 species completion of the ecoduct, the dela hybrida). Still, nearly a third of ground beetles were caught on number of species caught on the of the number would have to have and around Zandpoort (figure 3). ecoduct was already significantly walked over to the ecoduct: species without wings or functional flight Some species do not need the tree-stumps muscles. The following year, the number of species on the ecoduct in their advance over the bridge. grew considerably, in particular due to the ‘stobbenwal’ (photo p.18). The pitfall traps around the two higher than what was caught in the In 2016 and 2017, various non-fly- other ecoducts caught an additional surrounding area. This is mainly ing species were caught in the stob- nine species in this same period. due to the fact that on both sides benwal that had not been found on This is a large variety of species, of the ecoduct, the traps were the ecoduct before. A nice example ▶

● Figure 5. Catches for Masoreus wetterhallii on and around Zandpoort in 2015-2017.

3 ● 21 ● Oniscus asellus. Photo: Bert Pijs. ● Pitfall trap with formalin and chicken wire to prevent vertebrate bycatch. Photo: M. Boeken. OniscusOniscus asellus asellus PhilosciaPhiloscia muscorum muscorum 60 60 Oniscus asellus 1400 1400 Philoscia muscorum 50 50 Leistus ferrugineus 1200 1200 Panagaeus bipustulatus 1000 1000 4010 40 8 2015 2015 800 800 2015 2015 308 30 6 2016 2016 600 600 2016 2016 206 20 2015 2017 20174 400 400 2017 2017 2016 104 10 200 200 02 0 2 0 0 2017 1 2 1 3 2 4 3 5 4 6 5 7 6 8 7 9 8109 10 1 2 13 24 35 46 57 68 79 8109 10 0 0 ● Figure1 2 6.3 Catches4 5 for6 two7 types8 9 of 10woodlice (left:1 common2 3 woodlouse,4 5 6 7right:8 com9 -10 mon striped woodlouse) that use the tree-stumps (series 9 and 10) in 2015-2017.

would be Leistus ferrugineus. In ecoduct from the same side. This and around Egmond). Zuid-Ken- 2015, this species was only found does not have to be the case: they nemerland was a well-known site in a sea buckthorn (Hippophae could also have come from the for this species in the last century, rhamnoides) thicket on the northern other side. To further investigate but it had not been found in the side of the ecoduct, and in 2016 it this, population genetic research much-studied AWD within the was encountered in the stobbenwal would be useful (see Oostermeijer 1974-2005 period (Baeyens et al., as well. In 2017, it was no longer et al., 2018, elsewhere in this 2007). And although this sizeable found in the buckthorn thicket, issue). beetle sports wings, there is some whereas in the stobbenwal it was There were also some surprising doubt as to whether it can actually present in relatively large numbers, finds. For example, in 2016, several fly (Turin, 2000). and also out on the ecoduct itself, in individuals of the species Dyschir- the traps closest to the section that ius angustatus were found at Other groups then sported the densest vegetation. different sites on the ecoduct. This What makes ground beetles such A similar development shows the (strong-flying) species had not been valuable ecological indicators is for spread of the striking Panagaeus seen in all of the western Nether- instance the great range of species bipustulatus (figure 4). lands, and is caught so rarely that and their widely differing habitat Some species do not need the its ecology is still little known (Tu- preferences. But more groups are stobbenwal in their advance over rin, 2000). This beetle was found on useful when it comes to investigat- the ecoduct. Masoreus wetterhallii, the ecoduct again in 2017. Another ing how dune connections are used another non-flying species measur- 2017 find that was at least as rare and what the impact of their layout ing about 5 mm that frequents dune was Harpalus serripes, caught is. Litter eaters such as woodlice grassland with open spaces, was both on and around the Zandpoort will not pop up on a barren ecoduct found on the ecoduct before it was as well as the recently completed en masse, and the seven species caught in the stobbenwal (figure 5). Zeepoort, with a kind of dry sandy that were found in this study are The distribution found in consecu- soil, which in this century had only certainly no rarities. But the pres- tive years would seem to suggest been caught in a few places in the ence of the stobbenwal does give that several species are crossing the dunes of Noord-Holland (Texel a clear impression of the ways in

22 ● 3 ● Series of traps on the Zandpoort. Photo: M. Boeken which such a structure can create centipede, and Vertigo substriata, a from the Province of Noord-Hol- new opportunities, and for instance whorl snail. All these species occur land and PWN. Without the support connect populations, as we have in areas adjacent to or even already and cooperation of the site man- seen here (figure 6). on the ecoducts themselves. agers and a number of experts, the Predators such as harvestmen For stenotopic species (which only results would have been a lot more also exemplify the effects of the tolerate a narrow range of environ- limited. stobbenwal. In addition to some of mental conditions) in the dunes, Annual reports for this study can be the larger species that are resistant of which this article features only accessed on www.pwn.nl. to dehydration, the dunes harbour a limited number of examples, quite a few smaller species that tend ecoducts therefore appear to have Michiel Boeken to keep to the shade. Actually, most a function, and such connections [email protected] of the fourteen species that were between fragmented habitats can be counted prevailed in the denser of vital importance. thickets: an average of ten. In the The results of the first three years dune grassland there were signifi- of research show that the Zandpoort cantly fewer (three to five), and on ecoduct is already being used by a the ecoduct itself usually only two large number of species, which start- Reference Literature ● BAEYENS, G., M. KONING, H.L. or three species are found, while ed only shortly after its construction. KONING-VAN VUUREN & H.L. TURIN, 2007. in the stobbenwal six to eight were This also includes species for whom Loopkeververkenningen in de Amsterdamse found in 2017. roads and railway tracks are a major Waterleidingduinen (1989-2001). Rapport obstacle. The same was observed in 07.011225, Waternet , Amsterdam. Conclusions the first few months after comple- ● OOSTERMEIJER, G., J. BRUGMAN, P. KUPERUS & M. BOEKEN, 2018. Natuurbrug- The dunes of Zuid-Kennemerland, tion of the Zeepoort. The stobben- gen en de genenuitwisseling van loopkevers. in addition to typical dune species, wal features also appear to have Tussen Duin & Dijk 17(3): 34-37. harbour a great many other species an important function, as a magnet ● TURIN, H., 2000. De Nederlandse loopke- that do not or hardly occur else- and in guiding species towards the vers, verspreiding en oecologie (Coleoptera, Carabidae). Nederlandse Fauna 3. NNM where in the country. This region ecoduct. The study will be continued Naturalis, KNNV Uitgeverij & EIS Nederland, is explicitly mentioned in the over the following years. Leiden. literature, for example, with regard ● VAN DER SPEK, V., D. GROENENDIJK, K. to unique varieties of Harpalus Acknowledgements LEVER & R. LUNTZ, 2017. Zandpoort komt xanthopus winkleri, a ground This study was made possible these over de brug. Tussen Duin en Dijk 16(4): 8-11. beetle, Lithobius subtilis, a small past few years with financial support

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