Large Marsh Grasshopper

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

1. Contents

1. Contents
2. Summary
3. Survey aims
4. Background
5. Collating existing information
   1. Number of sites and populations
6. Methods
7. Results
   1. Records of LMG
   2. LMG population assessments in 2017
   3. Habitat assessments in 2017
   4. Habitat management issues
   5. LMG behavioural observations
   6. LMG colour variation
8. Conclusions
9. Acknowledgements
10. References
11. Appendix 1: Sites surveyed in 2017
12. Appendix 2: Changes in recorded distribution at 1km square level
13. Appendix 3: Species photos
14. Appendix 4: Site maps and photos

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

2. Summary

1. The Large Marsh Grasshopper, Stethophyma grossum (Linnaeus, 1758) is the largest of the UK’s native grasshoppers (Orthoptera: Acrididae), and one of the rarest, currently known in the UK only from the New Forest and a small area of Dorset.
2. This project aimed to survey known and potential sites for Large Marsh Grasshopper (LMG) on land managed by Forestry Commission under the Higher Level Stewardship Scheme (HLS) in the New Forest. Presence or absence was recorded, and an assessment was made of the status of the populations and habitats found.
3. Sites were targeted based on prior records and previous survey reports. Data was collated from all available sources, in order to prioritise 50 sites that had recent records of LMG and/or that were thought to contain suitable habitat. Of these, 30 were sites that had been surveyed in the previous (1997–98) New Forest surveys.
4. Sites from the previous surveys were digitised within a GIS. Sites visited in 2017 have also been digitised, along with the records from 2017 and all available prior records.
5. The surveys produced 60 individual records of LMG, and 25 further new records of LMG were collated by the authors from records provided by other New Forest naturalists.
6. Of the 50 sites surveyed in 2017 LMG was found at 25 sites; records in 2017 were reported to the authors for a further two sites, and at 23 sites no LMG could be found (although LMG was only judged likely to be absent at 19 of those).
7. Four sites were assessed as supporting a “Strong” population, with another 15 suporting a “Moderate” population. For the 30 sites that had also been surveyed in the 1990s there was little change, with only two sites having apparently gained LMG and two having apparently lost LMG in the 20 years between the two survey periods.
8. An assessment was also made of potential habitat suitability at each site, based on the presence of suitable mire habitat and associated plant species. Eight sites were assessed as having “High” potential for providing suitable LMG habitat, with 25 at “Moderate” potential and 17 at “Low” potential. Of those habitats assessed as being of low potential, the causes were most often that the sites appeared too dry and lacking in Sphagnum, and/or in some cases that growth of Bog Myrtle, Purple Moor-grass and/or scrub invasion was becoming too dense.
9. Overall the results present an encouraging picture of LMG populations in the New Forest. There are few signs of change over the last 20 years, and populations remain widespread over much of the Forest area. Some of these populations are small, and there is good reason to regard them as vulnerable to habitat change, e.g. if water levels were to diminish and/or bogs were to become increasingly overgrown with Bog Myrtle, Purple Moor-grass or scrub and trees. But there is no sign at the present time of decline within the New Forest as a whole, and with mire restoration work taking place in the Forest there is the potential for LMG to strengthen its populations in future.

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

3. Survey aims

The main aims of this survey were to visit known and potential sites for Large Marsh Grasshopper on land managed under the Higher Level Stewardship Scheme (HLS) in the New Forest; to record its presence or absence at these sites, and to provide an assessment of the status of the populations and habitats found.

4. Background

The Large Marsh Grasshopper, Stethophyma grossum (Linnaeus, 1758) is the largest of the UK’s native grasshoppers (Orthoptera: Acrididae), and one of the rarest. In the rest of this report the species is abbreviated as LMG. See photos in Appendix 3.

In the UK, LMG is now known only from wet, Sphagnum-dominated mires on heaths in the New Forest and in Dorset (Poole basin area), having been lost from former sites in Cambridgeshire, Norfolk, Somerset and Surrey (Sutton et al. 2017). It is resident in western Ireland. Elsewhere in Europe it is widespread but uncommon, and is found in a wider range of damp habitats including wet grassland (Benton 2012). There is some evidence of a recent range expansion in Germany, for which climate change is seen as the likely driving force (Trautner and Hermann 2008).

LMG is an herbivorous insect, feeding on grasses, rushes and sedges. Eggs are laid in late summer at the bases of grass tufts, where they remain until hatching the following May or June. (Benton 2012.)

Cheesman and Brown 1998 provided a detailed analysis of the habitat associations of LMG at one New Forest site, Upper Crockford Bottom (SZ3499). They noted that LMG is found in sites that typically contain a mosaic of dry heath, wet heath and mire, and that “the highly localised arrangement of [LMG] colonies [within] these habitat mosaics is suggestive of a high degree of fidelity towards a particular set of ecological conditions”. Their study looked at numbers of LMG in relation to various habitat features along a transect from wet mire to dry heath, and largely supports the more general habitat associations in the literature. LMG is strongly associated with open areas that are dominated by Sphagnum moss (typically described as bogs or quaking bogs), and is negatively associated with higher levels of heathers and other ericoids and small shrubs. Within the Sphagnum bogs a positive association with areas of small open water bodies was found.

Edwards (2002, and quoted in Miller 2017) gives descriptions of similar habitat associations in Dorset: “Observations from this and previous surveys suggest it prefers permanently wet sites with Erica tetralix, Narthecium ossifragum, Eriophorum angustifolium, Rhynchospora alba and Molinia caerulea over a well-developed Sphagnum carpet, particularly S. papillosum and S. pulchrum. Other species forming a significant part of the vegetation at some sites include Erica ciliaris and Schoenus nigricans.”

Dorset surveys by Edwards (2002) and Hunnisett, Allen and Edwards (2006) associated LMG occurrence with the NVC (National Vegetation Classification) community M21a (Narthecium ossifragum – Sphagnum papillosum valley mire; Rynchospora alba – Sphagnum auriculatum sub-community); community M14 (Schoenus nigricans – Narthecium ossifragum mire) was also a common component of the habitat.

Miller (2017) reviewed European literature on LMG and provides a detailed overview of habitat use at different life stages (but this is in part based on research carried out in habitats that differ from those in the New Forest).

LMG was given a conservation status of “Vulnerable” in the insect Red Data Book (Shirt 1987), and has been the subject of a Species Recovery Programme under the auspices of Natural England (formerly English Nature). The conservation statuses of the Orthoptera have been recently reviewed (Sutton 2015), and LMG is now assessed as follows:

• Threat status: “Near Threatened”, meaning the species has “been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is likely to qualify for a threatened category in the near future” (IUCN 2001).
• Rarity status: “Nationally Rare”, a category for “native species recorded from 15 or fewer hectads [10km squares] of the Ordnance Survey national grid in Great Britain since 31st December 1989 and where there is reasonable confidence that exhaustive recording would not find them in more than 15 hectads.”

In addition, LMG is listed as a Species of Principal Importance under Section 41 of the Natural Environment and Rural Communities Act 2006, which includes species that are “of principal importance for the purpose of conserving biodiversity” and therefore need to be taken into consideration by a public body when performing any of its functions with a view to conserving biodiversity.

Of the remaining UK populations of LMG most are found in the New Forest, where this large and colourful grasshopper can be considered a flagship species for the conservation of its mire habitats. Most of its New Forest populations are on land managed by the Forestry Commission.

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

5. Collating existing information

Information on previous sites and records was collated from these sources:

• Orthoptera and Allies Recording Scheme (ORS, the national recording scheme covering grasshoppers) (number of records = 124).
• Records available via the NBN Atlas (https://species.nbnatlas.org/species/NBNSYS0000006834) (excluding those already in the ORS dataset; n = 76).
• Reports from previous New Forest surveys of this species, carried out by Oliver Cheesman and Val Brown (Brown and Cheesman 1997, Cheesman and Brown 1998) (n = 28).
• Records from Hampshire Biodiversity Information Centre, provided by Forestry Commision (n = 17).
• Records for year 2000 provided by Richard Reeves (n = 10).
• Observations on the iSpot website (https://www.ispotnature.org/communities/uk-and-ireland/species-dictionary/NBNSYS0000006834/stethophyma-grossum/observations) (n = 5).

Species records from these sources were combined into an Access database and processed to remove duplicate records, and then analysed using QGIS. Site boundaries from Brown and Cheesman 1997 and Cheesman and Brown 1998 were digitised in QGIS, following the hand-drawn boundaries in the reports as closely as possible.

One record in the ORS dataset requires a correction to its grid reference: this is a record from S. Currie on 26 July 2009 at Acres Down (BRC unique ID 343_17_1197), which in the ORS data is located at SU2608 – the grid reference should be SU27040857 (S. Currie pers. comm. to P. Brock).

5.1 Number of sites and populations

The above records for LMG were plotted at 1km square level. This produced a list of 62 squares (Table 1) within the New Forest that have had at least one LMG record, of which 20 squares have records since 2000 (and 17 squares have no record since 1980). A further 10 squares were listed in the 1990s survey reports as worthy of investigation but with no known LMG records.

It was not possible to visit all 72 of the 1km-squares listed above within the time available during this contract, so priority was given to sites with recent records and that had been identified as having suitable habitat.

The digitised boundaries from the 1997-98 survey reports were used to help target areas within the 1km squares.

6. Methods

From the prioritised list of 1km squares, 50 sites were visited between 28 July and 15 September 2017, and are listed in Appendix 1 (see also Figure 2 in Section 7.2 below). Of these, 30 were sites that had previously been surveyed in 1997-98 by Brown and Cheesman.

At each site surveys were carried out in favourable weather conditions as far as possible – for the most part surveys were carried out in warm, sunny conditions, but some survey visits had to take place on cloudier days. Weather conditions and temperature measurements were recorded (see Appendix 1).

LMG was surveyed using direct searching in suitable habitats, and listening for calling males (the call is a distinctive ‘ticking’ sound). Target notes were recorded for each site, and an assessment was made of the strength of the LMG population present, and of the potential for the habitat to support LMG.

7. Results

7.1 Records of LMG

From the site visits, 60 individual records of LMG were made, and 25 further new records of LMG were collated by the authors from records provided by other New Forest naturalists. In addition, 57 records of ten other species of Orthoptera and allied groups were made during LMG fieldwork. Details of all these have been supplied as a spreadsheet and GIS layer to FC, and as a spreadsheet to the national recording scheme (see also Figure 2 below).

The new records for 2017 add substantially to the total number of records for this species in the New Forest. Figure 1 shows the total number of records of LMG in the New Forest per decade, based on all the data available (see section 5 above). LMG and other Orthoptera species do vary in apparent numbers in the New Forest from year to year, no doubt reflecting variations in weather, but the numbers recorded are heavily influenced by recording effort (number of people seeing them and sending in their records) as well. For instance, much of the apparent peak in the 1980s results from the collation by A.R. & N.I. Welstead of data from many recorders for their privately published Orthoptera of the New Forest and its environs 1980 to 1988. Clearly, the number of records on its own does not provide a good measure of population trends for LMG in the Forest.

Hornet Robberfly observations

Hornet Robber-fly Asilus crabronifornis is a Species of Principle Importance (NERC Act) and is uncommon in the open Forest, but was noted three times during the LMG survey:

• Beaulieu Heath, towards Peaked Bottom, 10 August 2017, SZ35819916
• Hardley Bridge area, 15 August 2017, SU42400451
• Vales Moor, 27 August 2017, SU18960402

It has also been seen near Bagnum Bog in 2014 (PB). Lucas (1920) referred to Hornet Robberfly carrying off a male LMG as prey.

7.2 LMG population assessments in 2017

Where populations are strong and weather conditions are suitable, LMG can be readily found within its preferred habitat. However, there are some difficulties with surveying for this species that need to be born in mind when interpreting the survey results:

• The preferred habitat of wet ‘quaking’ bog can be difficult and in some cases dangerous to access, and at many sites survey has to be concentrated around the edges of the bogs. This can lead to a degree of under-recording of abundance at sites where it is known to occur, and may contribute to it being missed when present at low density.
• LMG is most active in favourable weather conditions (sheltered, warm and sunny), when males are calling and both sexes will be visible in the vegetation and may fly. As soon as weather conditions become less ideal the grasshopper will shelter deeper in the vegetation, becoming less active and much less apparent to the observer. Surveys in 2017 took place in favourable conditions wherever possible, but the weather was not ideal in all cases (see site visit notes) and may have contributed to under-recording in some sites.

Consequently it is difficult to get objective measures of population size for this species, and it is hard to prove that it is absent from a site. The assessments given below of site suitability and population size are based on the authors’ interpretation of the numbers of LMG found, taking into account habitat and weather conditions.

In total, of the 50 sites surveyed in 2017 (see list in Appendix 1 and maps and photos in Appendix 4), the authors found LMG at 25 sites, 2017 sightings were reported to the authors at a further two sites, and for 23 sites no LMG could be found. Estimates were made of the strength of population at each site, based on the numbers seen and with allowance for weather conditions and habitat suitability (Table 2). Although LMG was not found at 23 of the sites, it was only judged likely to be absent at 19 of those: in four cases the apparent absence may have been due to relatively poor weather, and these were judged as potentially supporting weak populations.

Four sites were assessed as having a “Strong” population: Bagnum Bog area; Shoot Wood area, Burley; Roman Bridge, Bramble Hill/Warwickslade; Matley Bog A. In addition, Cranes Moor was assessed as “Moderate to strong”.

Figure 2. Sites surveyed in 2017

There is no obvious geographical pattern to the distribution of populations (Figure 2). The strongest populations are in the centre and west, but other categories are well spread across the Forest. There are two clusters of sites (in the east and in the west) where the populations were apparently absent in 2017, but we don’t believe that significant conclusions can be drawn from this. The difficulty of locating small populations of LMG in less than perfect weather conditions means that it is hard to know with certainty that they are in fact absent. The authors are not aware of any habitat changes in these two cluster areas that might suggest a widespread reduction in populations.

Of the 50 sites visited in 2017, 30 had been surveyed as part of the work by Brown and Cheesman in 1997-98, and there little overall change in occupancy from that time (Table 3). The two sites where LMG had been present but was not recorded in 2017 (Holmhill Bog and Dibden Inclosure Valley) both retain suitable habitat, and it is considered likely that LMG could still be present, especially at Holmhill Bog.

Of the 20 sites surveyed that were not included in the 1997-98 surveys, 12 sites were supporting LMG, an additional site was reported to have had LMG present in 2017, and there were seven sites where LMG could not be found.

7.3 Habitat assessments in 2017

Cheesman and Brown (1998) referred to a pilot scheme at Upper Crockford Bottom and “confirmed the localisation of the species within Sphagnum mire or mire/wet heath transitional habitat, and its apparent exclusion from wet heath per se and dry heath habitat. Strong positive correlations were found between [LMG] activity and percentage cover of Sphagnum, Rhyncospora alba, and areas of exposed surface water. Grasshopper activity negatively correlated with percentage cover of ericoids/sub-shrubs and Molinia caerulea.” The overall report conclusion was reached (at least in the New Forest) that LMG is confined to open Sphagnum dominated areas (i.e. ‘bogs’ or ‘quaking bogs’), and that surface water is important with work undertaken showing “a positive correlation between grasshopper activity and surface water which was stronger than the correlation with Sphagnum.” The study also suggests that the presence of Rhyncospora alba (White-beaked Sedge) is a good indicator of area favourable for LMG.

The 2017 fieldwork found the same type of sites favourable i.e. a mosaic of heathland habitats, with open wet mires supporting LMG (Photo 1). Ideal areas have a range of plants associated with the best bogs, with Purple Moor-grass Molinia caerulea (LMG feeds on blades and stems), Bog Myrtle Myrica gale, Cross-leaved Heath Erica tetralix, Sphagnum mosses, Broad-leaved Cotton Grass Eriophorum latifolium and White-beaked Sedge Rhyncospora alba.

Photo 1: good habitat at Hinchelsea Bog, open with plenty of Sphagnum

At these sites, Bog Bush-cricket Metrioptera brachyptera tends to occur as well (sometimes also Long-winged Conehead Conocephalus fuscus) – Bog Bush-cricket was recorded at virtually all sites LMG was seen [and others], usually around the edges in tussocks and sometimes extending into drier heath surrounding mires. Rhyncospora alba does not occur at all the sites at which LMG occurs, and Myrica gale is scarce at some.

Even small bogs may have small populations of LMG but Sphagnum carpet is often important. Larger bogs can have good populations of LMG if conditions are suitable, although they may be concentrated in parts of the area. LMG tend to prefer areas with carpets of Sphagnum. In some cases these areas are sheltered by small hills and surrounding vegetation, such as woodlands.

For each site visited, the potential of the habitat to support LMG was assessed (Table 4).

Of those habitats assessed as being of low potential, the causes were most often that the sites appeared too dry and lacking in Sphagnum. Dense growth of Bog Myrtle, Purple Moor-grass and/or scrub invasion were apparent at a few of the Low or Moderate sites. Bog Myrtle is a feature of many of the LMG sites but in a few has become so dense as to limit the more open Sphagnum areas that LMG is most strongly associated with. Young pine trees were invading one site (Shatterford/Stephill Bottom). Two of the Moderate sites (Matley Bog B and Shatterford/Stephill Bottom) showed signs of heavy grazing pressure, with short vegetation, trampling of the muddy pools and dung deposition in the bog habitat, but this is not a problem for most of the sites, where grazing animals largely avoid the wettest parts of the mires.

The most important factor in maintaining LMG in the New Forest will be the continued maintenance of open bog habitats, and consequently any loss through drainage or other changes in water level, or through afforestation or succession to scrub, should be avoided. The mire restoration work currently under way in the Forest should provide opportunities to expand the potential habitat for LMG and other bog species.

Where areas of mire are close (within c. 500 metres) but are separated by trees or scrub it may be beneficial to create corridors through any trees/scrub to allow dispersal of LMG.

7.4 Habitat management issues

Potential habitat management issues were noted at the sites in Table 5.

Photo 2: Bog Myrtle and heathers getting too tall and dense at Clumber Inclosure

Photo 3: Bog Myrtle becoming too dense at Wilverley Bog West

7.5 LMG behavioural observations

Males fly readily when treading in the vicinity, sometimes landing 10 to 20 metres away. The larger females tend to move slightly on the ground or through the vegetation. One needs to look carefully as there can be several in close proximity.

When observing specimens resting on vegetation, they turn away if they realise there might be danger, sometimes walking backwards to the protection of the undergrowth below. Stridulation is often heard on sunny, warm days, caused by males resting on vegetation flicking a hindleg (sometimes both) against a wing tip. This is often several bursts at a rate of two or three a second, a sound quite unlike other British grasshoppers. Both sexes may produce this sound when threatened.

No egg-laying was observed, but it is reported that up to 14 eggs are laid in an elongated pod at the base of grass tufts, where they overwinter until spring. Mating pairs are apparently rarely seen and none noted during the fieldwork. Benton (2012) and Miller (2017) summarise the latest research.

7.6 LMG colour variation

LMG is a variable insect. It is usually olive-green (sometimes brownish), shading to yellow laterally. Females are sometimes greyish brown and various authors refer to an ‘uncommon’ female purple form. Several of our UK grasshoppers have a pink or purple colour form, usually in both sexes. However, in adults they are only known in female LMG and are thought to be linked to genetics. There is, for example, references to erythrism, a little-understood genetic mutation caused by a recessive gene. This is not a convincing argument and in need of further research.

A simpler explanation is likely. The wide variation in colours of even our British grasshopper species, indicates they are often simply matching their surroundings, presumably for camouflage. Purple colour forms of the LMG are well hidden in areas near flowering heather. The purple forms appear to the human eye to be conspicuous when seen against green backgrounds, but possibly does not stand out to potential predators, and may be well camouflaged against some of the red/brown forms of Sphagnum.

In certain Australian pest phasmids (stick insects), when large populations occur, a changed colour phase for some females may help them survive predation (an adaptation known as kentromorphism; Key 1957). Kentromorphism is little known but a change brought about by environmental stimuli (high population density) cannot be ruled out in LMG. The limited data on purple form LMG (see below) certainly links in with some of the better sites, but kentromorphism is considered unlikely, as purple forms do not appear to occur in all the strong populations, being unrecorded at sites such as Matley Bog and surrounds.

Purple form, females noted in 2017:

• Bagnum Bog SU18780213 [Paul Brock, 10 August 2017 – edge of bog between heather and mire]
• Bagnum Bog SU18740210 [Paul Brock, 26 August 2017 – edge of bog between heather and mire, opposite side of bog, clearly a different specimen]
• Bagnum Bog approx. in areas above x 3 [Bjorn Beckmann, Paul Brock & Martin Harvey, 15 September 2017] – one only showing minor purple marks on face and laterally on thorax
• Peaked Bottom SU36019974 [Leanne Sargeant, 8 August 2017 – interface between heather and mire]
• Shoot Wood area SU23490325 [Richard Reeves, 13 August 2017]
• Shoot Wood area SU23420327 x 5 [Richard Reeves, 13 August 2017 – more in wetter area, away from heathers]

Also recorded in the past:

• Bagnum Bog SU18740213 [Dave Browne 6 September 2014, Paul Brock, 15 September 2014]
• Hincheslea Bog [Richard Reeves, date(s) and exact grid references not specified, said to be pinkish/red unlike purple specimens west of Burley]
• Moonhills SU409025 [Tara Dempsey, 11 August 2010]
• Strodgemoor Bottom SU187037 [Tara Dempsey, 12 September 2010]
• New Forest [reported by Lucas, 1920]
• New Forest, locality not disclosed [Collins, 1993 - pink male and female nymph collected and reared. Male and offspring normal colour form, even if pink as nymphs - only the females remained pink in adult stage]

Some areas, including those beyond Lyndhurst, only appear to produce normal colour forms (observations by Brock and Reeves, pers. comm.).

8. Conclusions

Overall the results present an encouraging picture of LMG populations in the New Forest. There are few signs of change over the last 20 years, and populations remain widespread over much of the Forest area. Some of these populations are small, and there is good reason to regard them as vulnerable to habitat change, e.g. if water levels were to diminish and/or bogs were to become increasingly overgrown with Bog Myrtle, Purple Moor-grass or scrub and trees. But there is no sign at the present time of decline within the New Forest as a whole, and with mire restoration work taking place in the Forest there is the potential for LMG to strengthen its populations in future.

Past records show that LMG remains under-recorded unless targeted surveys are promoted. It would be worth investigating the potential for further volunteer involvement with this species, to confirm its presence at the full range of sites and/or to monitor its numbers at particular sites. Miller (2017) outlines a transect methodology that could be applied to individual sites, with the four strongest populations being the highest priorities for longer-term monitoring of this kind. However, the nature of these mire sites makes them hazardous to access and any volunteer programme would need careful planning and support.

9. Acknowledgements

Thanks to: Leanne Sargeant at Forestry Commission for setting up the project, and providing data along with much useful information about the sites; Helen Brock for assistance with fieldwork; Bjorn Beckmann of the national Orthoptera and Allies Recording Scheme for providing data, references and joining a site visit; Jacqui Miller of RSPB for providing additional references and a copy of her very informative report (Miller 2017); Richard Reeves and Colin Easton for providing unpublished records from 2017 and 2000 and for information on sites likely to support good LMG habitat; Martin Noble for discussion over potential habitat changes.

10. References

• Benton, T. 2012. Grasshoppers and crickets. Collins New Naturalist.
• Brown, V.K., and Cheesman, O.D. [Assumed as 1997.] English Nature Species Recovery Programme – Large Marsh Grasshopper (Stethophyma grossum): 1997 pre-recovery project report.
• Cheesman, O.D., and Brown, V.K. [Assumed as 1998.] English Nature Species Recovery Programme – Large Marsh Grasshopper (Stethophyma grossum): 1998 pre-recovery project report.
• Edwards, B. 2002. The current status of the Stethophyma grossum L. Large Marsh Grasshopper in Dorset. Dorset Environmental Records Centre.
• Hunnisett, J., Allen, T., and Edwards, B. 2006. A Survey of Selected BAP Invertebrates in South Wessex Area (Dorset). Environment Agency.
• Key, K.H.L. 1957. Kentromorphic phases in three species of Phasmatodea. Aust. J. Zool., 5, 247–284.
• Lucas, W.J. 1920. A Monograph of the British Orthoptera. Ray Society, London.
• Marshall, J.A., and Haes, E.C.M. 1988. Grasshoppers and allied insects of Great Britain and Ireland. Harley Books, Colchester.
• Miller, J. 2017. Habitat Management and Survey Methods for Large Marsh Grasshopper Stethophyma grossum L. Sabbatical Report for RSPB.
• Shirt, D.B. 1987. British Red Data Books: 2. Insects. Nature Conservancy Council, Peterborough.
• Sutton, P. 2015. A review of the Orthoptera (Grasshoppers and crickets) and allied species of Great Britain. Natural England Commissioned Report NECR187.
• Sutton, P.G., Beckmann, B.C., and Nelson, B. 2017. The current status of orthopteroid insects in Britain and Ireland. Atropos 59: 6–59.
• Trautner, J., and Hermann, G. 2008. Die Sumpfschrecke (Stethophyma grossum L., 1758) im Aufwind – Erkenntnisse aus dem zentralen Baden-Württemberg. Articulata 23 (2): 37–52.

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

Appendix 1: Sites surveyed in 2017

These details have also been supplied as a spreadsheet and GIS layer. Strong and Moderate populations are highlighted.

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

Appendix 2: Changes in recorded distribution at 1km square level

These maps show all available records plotted as 1km grid squares. There is clearly variation between the decades, but much of this is due to variation in recording effort, and no overall trend in species distribution is apparent. However, it is reassuring that the total range within the Forest does not appear to be reducing.

Before 1950:

1950s:

1960s:

1970s:

1980s:

1990s:

2000s:

2010s (including current survey):

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

Appendix 3: Species photos

All photos by Paul D. Brock.

LMG female, Crockford, 10 Aug 2017

LMG female, purple form, Bagnum 26 Aug 2017

LMG male, Bagnum Bog, 26 Aug 2017

LMG male, Bagnum Bog, 22 Aug 2017

Large Marsh Grasshopper: New Forest survey 2017 – Harvey and Brock

Appendix 4: Site maps and photos

Aerial photo maps are provided below for all sites surveyed in 2017 where LMG was found, or where the habitat was assessed as being of at least ‘moderate’ potential. The sites mapped are:

The following sites were also visited in 2017 but are not mapped as LMG was not found and conditions appeared unsuitable. Boundaries for these sites have been provided to FC as GIS data.

The red polygons shown on the aerial photos are indicative of the areas surveyed, but do not provide a detailed representation of the extent of the LMG populations, not of the extent of apparently suitable habitat. In view of the LMG’s use of the edges of mires, where they start to grade in to drier heath, and also of the difficulty of access to some parts of the mires, it was not possible to provide a hard boundary to the sites assessed. The white squares are locations where LMG was seen and/or heard, based on GPS references.

Checked various areas, concentrating on Bagnum Bog SU18780213 with plenty of singing, found them all along bog edges from SU18840208 to SU18720212. Terrain difficult to access in parts, population restricted by size of boggy areas but at Bagnum alone (a small site) potentially low hundreds with sparser populations elsewhere in the vicinity. At least three purple form females noted.

Bagnum Bog area, showing good habitat with wet mire in the centre, grading to drier heathland, and well-sheltered:

Found at SU18740380, also SU18780302 but weather mixed. A purple form reported in 2010 indicates a reasonable population size.

First find SU19560260 and singing. Bulk around SU194027 [by Colin Easton] once a route was worked out on 27/08. Terrain difficult, likely to be plenty more grasshoppers in the areas of shorter vegetation. Reported population size [1997 report] looks exaggerated - populations can be very localised and numbers vary from year to year

Found at SU19510350 but weather mixed. Past records indicate a reasonable population size, although it is difficult to access some areas, it is likely there are a number of populations in the area

First find SU19430397, also SU19000400. Believed to be in low numbers from past experience of the site

Reported by Richard Reeves at SU20391175, typical bog vegetation on a sphagnum carpet. 2 recorded at the same site by Colin Easton 28.08.2017 at 22C, indicating just a weak, isolated population

Found at SU22220151. Difficult to access centre of bog; likely to be low population

Grasshoppers well spread at this little known site pointed out by Richard Reeves with all bog vegetation and good sphagnum carpets. Good population concentrated on SU23660325, including purple form females at SU23490325 and SU23420327. Plenty heard singing, particularly SU23420323 to SU23420327

Found at SU23170159. Some sphagnum but a lot dried up. All bog vegetation present, some Bog Myrtle. Wet areas by bridge productive, but fairly overgrown

Good patches of sphagnum, particularly around pools SU25160204 and SU25150294; access difficult in parts so mainly concentrated on more straightforward areas. Singing heard. Specimens found at various spots SU25220219 along edges of the bog to SU25150204. Reported at SU25640265 by Richard Reeves on 05.08.2017 in mixed weather

Duckhole Bog:

Very wet, mixture of bog plants with much sphagnum. Found at SU26840185. Richard Reeves recorded 2 at 'Redhill Bog' on 05.08.200 at SU268020

Shorter vegetation than some surrounding bogs. A likely small to modest population, but none found this survey - although present at nearby sites e.g. towards Duck Hole. Richard Reeves found 'lots' at SU267027 and SU265025 on 12.08.2000

Found at SU26560330 and SU26440315. Assessed as weak population due to the large size of the site, which is getting overgrown with Bog Myrtle. Little sphagnum

Found at much the same spot as in 1983, site with plenty of sphagnum, shorter grasses and small areas of Bog Myrtle

Found at SU27560053, SU27660050 to SU27770049, with singing in several areas. 1997/8 report suggested 'low density', but this is a large site, part of it in much better condition for Large Marsh than most bogs. With singing insects, easily in double figures in areas sampled c.15, making it one of the better sites

Hinchelsea Bog, good habitat:

Typical wet bog including sphagnum. Found at SU27480673 and many others to SU27550679. Across the other side of the track the population was sparse, with some dry sphagnum, but still found at SU27410693 and SU27400693. Access difficult, so actual population likely to be c.100 in a modest size area of habitat - also visited 19.08.2017 at 17.5C and none seen or heard in mixed conditions.

Warwickslade area, supported a strong population:

Found at SU27700820, close to a report of one by Colin Easton on 13.08.2017. Richard Reeves noted 2 at SU27030858 on tussocks in mire, on 01.08.2017. Mixed weather probably paid a part in lack of further sightings and indications are they are sparsely populated across these bogs. Records received from Dave Browne from August 2015 at SU27520893 and SU27390869

Matley Bog B: Lots of White-beaked Sedge, quite a lot of Sphagnum, some small pools of water; signs of recent heavy cattle grazing. No evidence of LMG but weather was poor.
Matley Bog A; Typical wet bog habitat for Large Marsh including sphagnum; the terrain is difficult in places. Always well recorded here as this is a popular site with naturalists, most activity from SU33450699 to SU33460708, including singing. The site is known to extend to others nearby such as SU3407 (Phil Budd, 1987), SU3208 (Simon Currie, 2010) & Fort Bog SU334083 ('lots' recorded by Richard Reeves 09.08.2000) - potentially a large population in an area of difficult terrain. The population size varies from year to year

Matley Bog A, good quality habitat:

Heavy grazing pressure; some taller vegetation - pines growing in the area require removal.

Found at SU35720193 and SU35790197. Report by Simon Currie 08.2017: heard singing at SU35880191. Richard Reeves recorded 3 in Little Wood Bog SU357019 on 10.08.2000 (1990s records were allocated to SU3502 but were only metres away from 2017 records

Small isolated bog, all typical bog plants present but sphagnum rather limited. Found at SU36670228

Some dry areas in a moderate size bog. Three females found in a minute at SU3646 0470, SU3665 0474 & SU3645 0469 in indifferent weather indicate that there are at least sparse populations, hence an assessment of a moderate population