Rapport Natuurpunt Studie
Newt research
LIFE
Green Valleys
nr 6 I 2020
Natuurpunt Studie contact: studie@natuurpunt.be Coxiestraat 11 • 2800 Mechelen • Belgium studie@natuurpunt.be • www.natuurpunt.be
Newt Research LIFE Green Valleys
The nature reserves of Green Valleys are part of the Natura 2000-network of European important nature reserves and receive financial support of the LIFE-fund of the European Union.
TERREINWERK Sam Van de Poel, Saskia Ribbens & Jens d’Haeseleer
TEKST Sam Van de Poel
EINDREDACTIE Jorg Lambrechts (jorg.lambrechts@natuurpunt.be)
Wijze van citeren:
Van de Poel S., 2020. Newt Research LIFE Green Valleys. Rapport Natuurpunt Studie 2020/6, Mechelen.
Content
1. Introduction ... 4
2. Method ... 7
3. Results ... 9
Pikhakendonk ... 9
Hellebos ... 14
Torfbroek ... 16
Floordambos ... 17
Silsombos ... 20
Kastanjebos ... 23
4. Conclusion ... 25
5. References ... 25
1.Introduction
The Great crested newt is the largest indigenous newt occurring in Belgium. From March till June, adults are present in the breeding habitat which contains a variety of waterbodies like ponds, drinking pools, bomb pits, abandoned meanders, … Waterbodies with stagnant, quite nutrient rich water. More than the other newt species, the Great crested newt prefers direct radiation of the sun reaching the surface of the water and a well‐developed underwater vegetation for the deposition of its eggs.
Degradation of its breeding (and hibernation) habitat resulted in a general decline of the species throughout Flanders. Therefor the species was included on the list of species that needed protection under the Bern Convention (Appendix II) that was implemented in 1990. Two years later, in 1992, this was confirmed in the Habitat directive, both on Appendix II and IV. This means that both, the specimens and the habitat where the specimens are occurring, are protected on the highest level possible.
Nowadays in Flanders, the Great crested newt has a quite large but localized (fragmented) distribution (Lewylle et al. 2018). Based on research and the long‐term monitoring of populations, the knowledge of the species and its needs has increased strongly during the latest decennia. More and more populations are managed using this new knowledge and so positive population trends are heeded. But these positive messages mainly are originating from populations that are housed within nature reserves where special measures are taken. And since only 36% of the known populations are located within SBZ‐H (Paelinckx et al. 2009) and less than one quarter of the populations is located within nature reserves, the Great crested newt is far from being saved.
The project areas of LIFE Green Valleys in Flanders contains only one area (Pikhakendonk) that is located within the areas assigned to the Great crested newt by the Species Protection Programme that is approved by the Flemish minister of environment at the end of 2019 (Figure 1). On the north side, the rest of the project areas is surrounded by the areas selected for the Great crested newt.
Figure 1: Visualisation of the project areas relative to the areas assigned to the Great crested newt by the Species Protection Programme.
Investigation of these project areas will in the first place give more information about the distribution of the species within ‘the triangle of difficult barriers’ (Figure 2). This triangle exists of a highway, a national airport, railroads with few migration options, a provincial national road and a canal. These are major migration barriers that are not likely to be crossed by newts. Only on the edges of this triangle there are a few observation of the Great crested newt.
Figure 2: Visualisation of the Great crested newt observations between 2010 and 2018 (source: www.waarnemingen.be) surrounding the project areas and the demarcation of the ‘triangle of difficult barriers’.
Furthermore, investigation of the project areas will give additional information about the distribution of the other newt species. The amount of newt observations within the project areas between 2010 and 2018 is quite low (Figure 3). Only 36 observations of the Alpine newt and 25 of the Smooth newt were registered in Waarnemingen.be. There were two observations of the group ‘Smooth or Palmate newt’, but based on the distribution pattern of the Palmate newt, it is most likely that both observations are Smooth newts.
Figure 3: Observation of newts within the project areas between 2010 and 2018. Only the Alpine newt and the Smooth newt were found yet (source: www.waarnemingen.be).
2.Method
The occurrence of the Great crested newt in the project region is investigated by standardized monitoring of adults with the help of fykes (type Vermandel) and for larvae with the aid of landing nets (type RAVON).
In addition, each pool is described using a standard form with a series of characteristics. All results were registered using the special project module for fyke and landing net research within Waarnemingen.be.
Based on the baseline measurement (T0) that took place in 2019, advice on action C5, the restoration of aquatic habitats, can be formulated. But even if the Great crested newt was not found during the fieldwork, the creation of suitable conditions for this species will be beneficial for a whole range of fauna and flora.
In the spring of 2019, we went a few days into the field as an exploration of the various project areas.
During this exploration, we looked for interesting waterbodies and clues to the presence of Common toads and Common frogs in the form of eggs and larvae. The presence of these species already gives a good indication of the potential of the waterbody for newts later in the year. During each visit, the route was registered using the mobile application of Waarnemingen.be, Obsmapp. For example, the Pikhakendonk project area was visited on 29 March 2019 (Figure 4), in the middle of the breeding season of the Common toad and the Common frog. Most of the visits were guided by trainee Saskia Ribbens who was a welcome help because of her excellent knowledge of the project areas.
Figure 4: Pikhakendonk project area (oranje) was visited on 29 March 2019 for exploration. The road followed (red dotted line) was planned in such a way that it passed along the bulk of the waterbodies.
After the inspection round, the fykes were placed to investigate the presence of adult newts. Fykes were placed in the water, checked the following day and immediately placed in new waterbodies in the area.
On average we always place two fykes in every waterbody, but depending on the water surface this could be some more or some less. Since we tried to make an inventory for all the project areas within this LIFE project, every waterbody was examined once with these fykes. Here too, Saskia Ribbens helped with the fieldwork as part of her internship. The trapping took place between the beginning of April and the middle of May 2019, the breeding period of the newts during which adults can be found in the water. Later on it is more useful to do more trapping events within the same waterbodies to get more information about the present populations.
To minimize the chance that pathogens are transferred from one place to another, the hygiene protocol was taken into account. When fykes were placed from one waterbody to another, within the same area, no disinfection of the fieldwork material was done. But when transferring from one area to another, the fykes, the landing nets, the plastic aquariums and our boots were disinfected using Virkon S (http://virkon.com/products‐applications/disinfectants/virkon‐s‐tablets/).
3.Results
The traps were placed in 30 waterbodies spread over the different project areas, that seemed interesting during the inspection round earlier that year (Figure 5). During these catches, the majority of the trapped specimens were Alpine newts (Ichthyosaura alpestris) (239 adults). But also 45 adults of the Smooth newt (Lissotriton vulgaris), a few thousand larvae of the Common frog (Rana temporaria) and a few dozen Ticklebacks. By surprise, we could also catch a Great crested newt (Triturus cristatus) male in one of the abandoned meanders in Pikhakendonk. And a few days later a different male was found in the same waterbody. Until the inventories for this project, the presence of the Great crested newt was not known for this area (Figure 3).
Figure 5: Visualisation of the investigated waterbodies, spread over the different project areas.
Pikhakendonk
The investigation round in project area Pikhakendonk took place on the 29th of March 2019. Based on the results of this inspection, a few waterbodies were selected for later investigation using fykes. But when this fieldwork was about to get started in the beginning of May, a lot of the selected waterbodies did already run dry or were about to run dry in the upcoming days/weeks. This phenomenon was caused by an extremely dry and warm 2018 when the groundwater level dropped very deep. This deficit could not completely be restored during the winter from 2018 to 2019 so that a large amount of waterbodies started the spring of 2019 with quite low water levels. Since the spring of 2019 was classified as ‘normal’, the general loss of water by the end of spring resulted in waterbodies that already ran dry.
Five of the selected waterbodies could be investigated (Table 1).
Only a few Alpine newts and one Smooth newt could be found. These results were unexpected low.
Waterbodies 85 and 86 were excavated in October 2018 and were therefore not suitable for newts yet.
The lack of any trapped newt in waterbody 72 was not expected and no obvious reason could be found for this. Further research will be needed to explain this phenomenon. We also expected more from waterbody 38 (Figure 7), a 500 meters long elongated abandoned meander where during the inspection round several spawn clumps of Common frog and strands of Common toad were found along the banks.
Based on the amount of grass at the bottom of the meander and the prevailing climatic conditions, we assume that it ran dry in 2018 (no fish). More trapping events were planned in for this waterbody, with success. On two out of five extra trapping events one Great crested newt could be found. This was the first time that the Great crested newt was found in project area Pikhakendonk. The bellies of both males showed two different patterns, so these were two unique specimens. Based on the catch effort, we can conclude that the present population is very small. Some weeks later, the abandoned meander ran dry (Figure 8). It can be assumed that in this waterbody no reproduction could be accomplished this year.
Figure 6: Visualisation of the location of the investigated waterbodies in project area Pikhakendonk.
Waterbody # fykes
Great crested newt
Alpine newt
Smooth newt
Palmate newt Fish
Boortmeerbeek – Hever – Poel 72 6 0 0 0 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 4 0 10 1 0 0
Boortmeerbeek – Boortmeerbeek – Poel 85 1 0 0 0 0 0
Boortmeerbeek – Boortmeerbeek – Poel 86 1 0 0 0 0 0
Boortmeerbeek – Boortmeerbeek – Poel 87 2 0 0 0 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 4 1 2 1 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 6 0 18 3 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 6 0 10 4 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 6 0 7 2 0 0
Boortmeerbeek – Boortmeerbeek – Poel 38 6 1 5 2 0 0
Figure 7: Abandoned meander in project area Pikhakendonk during the inspection round at the 29th of March 2019.
Figure 8: Abandoned meander in project area Pikhakendonk on a later fieldtrip at the 23th of May 2019, completely run dry.
This project area is, as for the Great crested newt, the most promising of all the project areas since it can be characterised as bocage landscape with sunlit meadows, hedges and woodlands. Sunlit waterbodies are present but need some improvements. The area is located within the valley of the Dijle river, between Mechelen and Leuven, along which several other Great crested newt populations are located (Figure 9).
With this discovery, another link is known in the chain of Great crested newt populations in this valley.
Figure 9: Visualisation of the position of Pikhakendonk within the valley of the Dijle river.
A number of measures (especially water management) could make project area Pikhakendonk extremely suitable for a large metapopulation of Great crested newts. The construction of a number of well‐located, fish‐free and climate proof pools is necessary for this. Optionally, a redesign of the abandoned meanders that are spread across the project area could aid in those needs.
But, in the first instance, the abandoned meander where the Great crested newts were found needs some urgent improvements. We advise a fragmented excavation of several parts of the meander so that these parts of the waterbody will hold the limited amount of water somewhat longer (Figure 10). In March 2019 (inspection round) the water level was approximately 1 meter deep at the deepest point. This is too shallow for the Great crested newt. The excavation of an extra 0.5 meter should be enough. We advise against a complete excavation because then the present vegetation, hiding places, egg depositing places,
… will all be removed at once. Since the eastern part of the meander is not sunlit because of the adjacent forest and parts of it are completely overgrown by the forest, it would be advantageous to make a dam near the location of the transition to the forest (Figure 10). This dam will divide the waterbody so that the water containing all the fallen leaves from the nearby forest, will not mix into the sunlit parts of the meander.
Figure 10: Advise on the partial excavation (0.5 meter) of the abandoned meander where Great crested newt was found (purple) and the location where a dam should be build (yellow).
The waterbody in between the ends of the meander is too eutrophic (livestock drinking pool and connected with the forest) to hold any newts. Because of its shallowness, it ran dry quite early in 2019.
Hellebos
The inspection round in project area Hellebos told us that only two waterbodies were worth inspecting for newts (Figure 12). But since these are pools located in the forest, no Great crested newts were expected.
The large ponds in the south‐western parts of the project area are deep ponds with steep banks and fish in it (Figure 11). If managed in an amphibian friendly way, these ponds could be very interesting because of the potential to manage the water level. Nowadays no newts are expected. The few waterbodies in the northeast are not interesting for newts, but the Common frog uses these pools to deposit their eggs.
Figure 11: One of the large ponds in the south‐western part of the project area, near castle of Ribaucourt.
Several Alpine newts and a few Smooth newts were found during the trapping events in the two selected waterbodies (Table 2). Several measures could be taken to improve the habitat for newts like making the waterbodies sunlit, excavating the sludge and partial removal of the water vegetation, but the gain of these measures will always be quite low in comparison with the cost (financial and ecological). More interesting would be to create sunlit pools in meadows nearby the (southern) edges of the forests. This would be more cost efficiently and the ecological profit at the long term would be much higher.
Figure 12: Visualisation of the location of the investigated waterbodies in project area Hellebos.
Table 2: Results of the trapping events in the selected waterbodies from Hellebos.
Waterbody #
fykes
Great crested
newt Alpine newt Smooth newt Palmate
newt Fish
Kampenhout ‐ Berg ‐ Poel 25 2 0 10 2 0 0
Kampenhout ‐ Berg ‐ Poel 26 1 0 0 3 0 0
Kampenhout ‐ Berg ‐ Poel 25 6 0 2 1 0 0
Torfbroek
Project area Torfbroek houses a number of large ponds that contains thick layers of sludge, very few water vegetation and fish (Figure 13). There were no expectations at all when the fykes were placed in the three ponds (numbers 1, 2 and 10). The results were therefore as expected, no newts were detected (Table 3).
Only by the removal of the fish and large earthworks, these ponds can be made suitable for newts. But this is not the priority for these ponds within the LIFE project.
Only waterbody number 12 seemed to have some potential. Therefore, two fykes were placed in this ditch.
Seven Alpine newts and one Smooth newt were found. To improve the conditions in favour of the newts,
Figure 13: Visualisation of the location of the investigated waterbodies in project area Torfbroek.
Table 3: Results of the trapping events in the selected waterbodies from Torfbroek.
Waterbody # fykes Great crested
newt
Alpine newt
Smooth newt
Palmate newt Fish
Kampenhout ‐ Torfbroek ‐ Poel 1 2 0 0 0 0 0
Kampenhout ‐ Torfbroek ‐ Poel 2 2 0 0 0 0 0
Kampenhout ‐ Torfbroek ‐ Poel 10 2 0 0 0 0 0
Kampenhout ‐ Torfbroek ‐ Poel 12 2 0 7 1 0 0
The pond complex in the east of waterbody 12 is an old fishpond complex, characterised by deep ponds with thick layers of sludge, no water vegetation, steep banks and the presence of fish. Since these are very bad conditions for newts, no samples were taken. Here as well, large earthworks would be needed to transform the fishponds into amphibian friendly ponds. But when this should be done, this could be a large asset for the project area.
Floordambos
Project area Floordambos consists mainly of forested area, but there are also some meadows, a few large waterbodies and some ditches/depressions in the forest. No interesting waterbodies were found during the inspection round across this project area. The depressions in the forest are used by Common frogs for the depositing of their spawn clumps, but run dry quite early in spring what makes them not useful for the
reproduction of newts. Only in one small pool at the edge of the forest we placed a fyke, but as expected, no newts could be detected (Figure 14, Figure 15 & Table 4).
Figure 14: The small pool at the edge of the forest that was investigated using a fyke.
Figure 15: Visualisation of the location of the investigated waterbody in project area Floordambos.
Table 4: Results of the trapping events in the selected waterbody from Floordambos.
Waterbody # fykes Great crested
newt
Alpine
newt Smooth newt Palmate
newt Fish
Steenokkerzeel ‐ Floordambos‐
Peutiebos ‐ Poel 1 1 0 0 0 0 0
The two large ponds, west and north of the investigated pool, are two private fishponds that are, in the present conditions not suitable as water habitat for newts. The large sedimentation basin south of the investigated pool could not be investigated because of the steep banks and the thick layers of sludge that needs to be crossed to reach the water surface. But no newts are expected to be found here because of the bad water conditions. Several things indicate that the water that is temporary stored in this basis has a chemical composition that is not preferred in a healthy environment.
The meadows north of the investigated pool are a potential place to excavate a complex of, for example, three pools with variating depths (climate proof). By decreasing the steepness of the banks of the pools, even these banks can be mown by the tractor that is mowing the meadows. So almost no manual labour is needed to keep the banks optimal. The forest surrounding these meadows will act as perfect land habitat where the newts will hibernate.
Silsombos
Nine waterbodies were investigated in project area Silsombos (two of them were investigated twice) (Figure 16). No high expectations were set here since most of the waterbodies are part of a ditch system, are old fish ponds or are completely embedded in the forest. The trapping events resulted in the finding of only a few Alpine newts (Table 5).
Figure 16: Visualisation of the location of the investigated waterbodies in the northern part of project area Silsombos.
Table 5: Results of the trapping events in the selected waterbodies from the northern part of project area Silsombos.
Waterbody # fykes Great crested
newt
Alpine
newt Smooth newt Palmate
newt Fish
Kortenberg ‐ Silsombos ‐ Poel 2 1 0 0 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 3 1 0 0 0 0 42
Kortenberg ‐ Silsombos ‐ Poel 6 1 0 1 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 7 2 0 0 0 0 10
Kortenberg ‐ Silsombos ‐ Poel 9 1 0 0 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 10 1 0 7 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 11 1 0 0 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 12 1 0 5 0 0 0
Kortenberg ‐ Silsombos ‐ Poel 13 1 0 0 0 0 4
Waterbodies 2, 3, 7 and 13 are connected to each other via a complex of small ditches and brooklets so that the fish that is present in one of the waterbodies, can migrate to the next. No newts can be expected in this type of system and it is not desirable to change the hydrology in this system since it is characteristic for the project area. Waterbodies 6, 9 and 11 are all ditches/depressions in the landscape. Depending on location, hydrology and status they can be used by newts, but since these are not in best conditions, no high amounts should be expected when searching for newts. These ditches ran dry quite early in 2018 and 2019, too early for newts, but ideal for Common frogs. Forest pool 10 houses a population of Alpine newts.
When possible, a partial removal of the sludge would improve the water habitat. Waterbody 12 is a reed field that completely covers the water surface. Newts will use this waterbody, but the vegetation is too dense to trap newts using fykes. The creation of some open water surface would benefit the newts.
Better than spending time and money at these secondary habitats, we advise to create new optimal habitat in the grasslands within the project area. By constructing clusters of pools spread over the grasslands and near the forest edges, the Alpine newt population will flourish, as well as the Smooth newt population of which only a few observations are known in the project area. Since these grasslands are wet and parts of it are flooded frequently, a mound must be constructed around the pools to prevent fish from entering the pools when the surrounding is flooded. These mounds can be constructed using the ground that is set free during the excavation of the pool. By making them wide and flat, one can mow the mound when mowing the rest of the grassland and manual labour is minimized.
The southern part of this project area is located in the valley of the Molenbeek. Here as well we selected some waterbodies that should be investigated using fykes (Figure 18). Pool ‘Rotte Gaten 1’ is a typical forest pool that is partially overgrown by Common alder and willows. Only a small amount of newts could be detected (Table 6). Partial removal of the sludge would increase the productivity of this pool, but it is not possible to approach the pool with an excavator because of the dense forest surrounding it. Some cuttings to hold the forest from overgrowing the pool will benefit as well.
Pools 16 and 17 are located in a swampy area with shallow and somewhat deeper water (Figure 17). In spring it is a real hotspot for Common frogs and later on also the Alpine newt is doing good here. That was shown when emptying the fykes at location 16 (Table 6). Ninety Alpine newts were trapped using two fykes! Currently there is no urgent need to do large works in this swampy area as regards to newts. But in time there will be the need to reopen the canopy so that in some parts the water remains sunlit. Otherwise the populations of Common frogs and Alpine newts will decrease.
Kortenberg pool 1 is a very large waterbody where the trapping of newts with a few fykes is always very difficult. Some Smooth newts were found, but this amount is not representative for the whole waterbody.
No measures are needed to be taken here. At locations 44 and 45, some Alpine newts and a Smooth newt were found. These are small ditches that hold some water. The partial excavation of these depressions would make them more climate proof and will benefit the newt species at the long term.
Figure 17: The swampy area near pools 16 and 17.
Figure 18: Visualisation of the location of the investigated waterbodies in project area Molenbeekvallei..
Table 6: Results of the trapping events in the selected waterbodies from the Molenbeekvallei.
Waterbody # fykes Great crested
newt
Alpine newt
Smooth newt
Palmate newt Fish
Herent ‐ Veltem‐Beisem ‐ Poel 44 1 0 3 1 0 0
Herent ‐ Veltem‐Beisem ‐ Poel 45 1 0 4 0 0 1
Kortenberg ‐ Meerbeek ‐ Poel 16 2 0 90 12 0 0
Kortenberg ‐ Meerbeek ‐ Poel 17 1 0 0 0 0 0
Kortenberg ‐ Molenbeekvallei
Kortenberg ‐ Poel 1 6 0 0 4 0 0
Kortenberg ‐ Rotte Gaten ‐ Poel 1 2 0 1 3 0 0
Kastanjebos
The last project area where fieldwork was conducted is the Kastanjebos. This is a quite dry area with only a few waterbodies. Two waterbodies were selected here, pool 46 and 47 (Figure 19). Both were excavated quite recently at the end of 2017. The following years were very dry so that the development of these pools and its water vegetation was somewhat counteracted. But based on the findings during this fieldwork it was shown that both pools contained already normal amounts of Alpine newts. It will be interesting to investigate these pools the following years, especially because at the east‐end of the forest,
just outside the project area, a population of Great crested newts is located. Therefore it would be very advantageous to create some additional pools in the meadows in the southern edge of the project area.
Figure 19: Visualisation of the location of the investigated waterbodies in project area Kastanjebos.
Table 7: Results of the trapping events in the selected waterbodies from the Kastanjebos.
Waterbody #
fykes
Great crested
newt Alpine newt Smooth newt Palmate
newt Fish
Herent ‐ Veltem‐Beisem ‐
Poel 46 2 0 28 0 0 0
Herent ‐ Veltem‐Beisem ‐
Poel 47 2 0 11 0 0 0
4.Conclusion
The absolute highlight of the conducted fieldwork was, without a doubt, the discovery of the Great crested newt in the abandoned meander in project area Pikhakendonk. Since only two adult males were found over several trapping events, it is most urgent to take some measures in improving the water habitat for the species. Pikhakendonk is also the most promising project area to build a large metapopulation that is a part of the chain of Great crested newt populations in the valley of the Dijle river between Mechelen and Leuven. The coming years, this population should be followed closely.
Some waterbodies can be improved by doing some small interventions. But throughout the different project areas there is a large amount of pools and ponds that are completely surrounded by forest or where large earthworks would be needed to improve the situation for newts. The work (and money) needed to improve these existing waterbodies can, in many cases, better be used to create new clusters of pools at promising locations within the project areas.
5.References
Lewylle I., Van de Poel S., Engelen P., Vantorre R., Hoeymans B., Alles P.‐J., Soille R., Huygen D., Smeyers N., De Smedt E., Teugels W., De Smedt P. & K. Lambeets. 2018. Boomkikker en Kamsalamander in Vlaanderen. Eindelijk van de ondergang gered? Rapport Natuurpunt Studie 2018/11, Mechelen.
Paelinckx D., Sannen K., Goethals V., Louette G., Rutten J. & Hoffmann M. (2009). Gewestelijke doelstellingen voor de habitats en soorten van de Europese Habitat‐ en Vogelrichtlijn voor Vlaanderen.
Mededelingen van het Instituut voor Natuur‐ en Bosonderzoek INBO.M.2009.6, Brussel, 669 pp.
