Research Article |
Corresponding author: Andrew J. Cherrill ( acherrill@harper-adams.ac.uk ) Academic editor: Tim Gardiner
© 2018 Richard G. Selman, Andrew J. Cherrill.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Selman RG, Cherrill AJ (2018) The lesser mottled grasshopper, Stenobothrus stigmaticus: lessons from habitat management at its only site in the British Isles. Journal of Orthoptera Research 27(1): 83-89. https://doi.org/10.3897/jor.27.15123
|
The lesser mottled grasshopper, Stenobothrus stigmaticus, occurs at a single site in the British Isles. This paper describes the history of site protection and management over 30 years including the introduction of conservation grazing management. Successes have been limited, but this has been due largely to issues around recreational access and stakeholder engagement rather than lack of ecological understanding. Despite severe challenges, sufficient experience has been gained to be confident that grazing by sheep can assist in re-establishing the grasshopper over areas of a protected site from which it is now absent or present in only scattered colonies. The grasshopper requires a short, open grassland and pockets of such vegetation occur naturally because of rabbit-grazing and thin, nutrient poor, free-draining soils around rocky outcrops. These small areas have proved to be critical to the species persistence and provide a nucleus from which spread can occur. Grazing management has involved complex negotiations with multiple stakeholders, including landowners, their agents, the landowners’ tenants, and the tenants’ graziers. Public access, cases of dogs worrying grazing livestock, and objections over the introduction of fencing in a once open landscape have made negotiations more difficult. Future success requires that these issues be addressed. Observations on a golf course within the site, with a remnant population of the grasshopper, suggest that winter-cutting of grassland may be a useful supplement to grazing management while such difficulties remain.
dogs, golf course, grazing, heathland, Isle of Man, mowing, protected area, recreation pressure, sheep worrying
The lesser mottled grasshopper Stenobothrus stigmaticus (Rambur) (Orthoptera: Acrididae: Gomphocerinae) is widespread in western, central and eastern Europe, but is often locally uncommon and declining because of habitat loss and abandonment of grazing on its favored agriculturally marginal habitats (
Throughout its range, S. stigmaticus is restricted to semi-natural habitats which have not been subjected to agricultural improvement through re-seeding or addition of artificial fertilizers (
The habitat of S. stigmaticus has been described variously as heath and dry grassland (
The habitat of S. stigmaticus on the Isle of Man accords with that reported elsewhere in Europe. The population occurs at greatest densities in areas with short grassland, heath, and well-drained maritime grassland on rocky cliff tops (
Livestock grazing is important in maintaining habitat for S. stigmaticus, although at some sites grazing by wild deer and rabbits appears to be sufficient (
Langness Peninsula in July 2006: A. and B. Short grassland supporting S. stigmaticus, M. maculatus and C. brunneus around rocky outcrops above the shore (with AJC taking notes); C. short grassy heath supporting S. stigmaticus near the mid-line of the peninsula; D. tall grassland and gorse near the mid-line of the peninsula with scarce S. stigmaticus restricted to short grass close to rocks and C. brunneus throughout; E. a path with S. stigmaticus occurring immediately adjacent and C. brunneus extending into the taller grassland beyond; and F. a patch of semi-rough (with RGS inspecting a grasshopper) and a grassy mound supporting S. stigmaticus and C. brunneus within the golf course.
The population of S. stigmaticus on the Langness Peninsula represents the species’ northernmost outpost in Europe and is the species’ only known location in the British Isles (
The Langness Peninsula is approximately 2.5km long and 0.5km wide, and is formed from a rocky islet connected to the main island by a sand tombolo (Fig.
The southern (seaward) end of the peninsula has a rocky shoreline on all aspects. Maritime grassland, with scattered heath, occurs near the shore. Inland is unimproved grassland, heathland around scattered rock outcrops, and a ploughed field (which has been cultivated in recent years for cereals grown under organic principles and to promote rare arable weeds after many years of abandonment). Until 1987 the southern end of the peninsula was grazed by sheep and cattle on an extensive basis (
The grasshopper was present at a small number of scattered locations within the golf course in 1964 and this has remained the case, but since discovery its main distribution has always been in the less intensively managed southern part of the peninsula (
The following sections focus primarily on grazing management in the southern half of the peninsula, although lessons arising from mowing within the golf course are summarized. The article is based mainly on unpublished reports (
Following limited survey work in the early 1960s (
Away from the shore, S. stigmaticus appeared to be even more dependent on localized rabbit grazing and the presence of thin, free-draining soils around rock outcrops. The species had declined more sharply than seen near the shore, and was restricted to patches of short grassland associated with rock outcrops (Fig.
Aerial photograph of Langness, showing the area covered by the golf course (light green), the distribution of S. stigmaticus in August 1964 (vertical hatching), 1990 (horizontal hatching), and sites occupied from 2002 in the absence of grazing (dark green) and sites occupied from 2002 where grazing had been reintroduced (red) (based on mapping by Mr. J. F. Burton reported in
By 2000, and the designation of the ASSI, it was already apparent that a re-introduction of grazing was desirable. DAFF established a Management Agreement with the owners of land in the south of the peninsula to run from 2001. A key aim was to bring habitat back to suitable condition for S. stigmaticus. This was facilitated with an annual payment to compensate for the challenges of conservation grazing and payment of the costs of fencing.
The fencing was put up in 2002/3, but there was outrage reported in local newspapers against the aesthetic impact, and because fences blocked the routes of some of the paths used by local people for recreation, though access was retained across the area (except the arable field) (
There was sheep grazing from 2002 to 2004, but then a change of land ownership necessitated renegotiation of the Management Agreement and sheep worrying issues started in 2005, which made this more challenging and added to the access discussions. As a result, grazing was not re-established until 2007, when a Management Agreement was made with the new owners specifying stocking rates equivalent to approximately 4 to 5 sheep per ha for a minimum of eight months per year. The agreement permitted the use of cattle as an alternative, but it was sheep grazing that was taken up. Grazing by sheep then continued until 2009, but because of the dog attacks the full eight-month prescription was achieved in only one of those three years. Between 2005 and 2009, around a dozen lambs and ewes were killed outright, chased over cliff edges to their deaths, or had to be euthanized after being mauled by dogs or injured on the rocks.
Despite these problems, grazing had some positive impacts on the grassland structure. Surveys in 2006 and 2009, showed the extension of S. stigmaticus from remnant colonies at the heads of gullies above the shore, into grassland towards the center of the peninsula where the species had been recorded in 1990 but not in 2002. In 2006, this was evident in one area even though the area had been ungrazed for the two years previous, but having received sheep grazing for two years before (
In limited areas, grazing created a structure that allowed the spread of S. stigmaticus from isolated remnant colonies, but this never reached the level necessary to have an impact on the distribution of S. stigmaticus across the whole site. Fundamentally, there were too few sheep for too short a period each year.
With continued problems around public access and dog attacks, there was again no grazing in 2010 and only brief grazing by a couple of horses in 2011, with little effect on the habitat. From the start of the dog issues there had been discussions regarding the need for livestock that would accept rough herbage, be robust against dogs, yet be safe around walkers. Highland cattle were favored but unfortunately were not available. Some provisions for cattle grazing had been provided in the Management Agreement from the start of the project, but cattle were eventually brought to the site as an alternative to sheep grazing, when four 8-month old heifers of modern breeding were introduced in 2012-2013. Survey in 2014 found S. stigmaticus in the center of the field, away from the coastal remnant colonies, but not across large areas of it, due to the grazing intensity remaining too low (
As with discussions around the access issue, progress with grazing has been hindered by long lines of communication between the officers of DEFA, the landowners, their agents, the tenant, and the tenant’s grazier. This produced complex and slow negotiations around issues arising. Moreover, no one lives permanently on the peninsula who can address issues as they occur.
Overall, the Management Agreement failed to deliver the desired outcomes at a large scale due to the prescription not being delivered fully, but did demonstrate that improvement in habitat suitability and population size of S. stigmaticus are achievable if grazing is managed effectively.
In 2015, the relocation of a golf course fairway was accompanied by ecological mitigation work agreed with DEFA as part of planning consent. An area of 2.5 ha was targeted for the clearance of gorse from around rocky outcrops known to have supported a single S. stigmaticus on a tiny rabbit-grazed patch in 2002. After gorse was removed the area was fenced off and grazed with barren ewes at a stocking rate of approximately 13 ewes per ha for several months in spring, and then again in the autumn. These were then replaced with similar numbers of yearlings (born that year and just weaned) which have grazed each year from September/October to May/early June in both 2016 and 2017. By the summer of 2017, the site was looking ideal for S. stigmaticus with short grass, outcropping rocks and a south-facing slope at the head of a gulley leading down to the shore (Fig.
Preliminary observations suggest that on the course, S. stigmaticus is restricted to grassland similar in structure to its habitat elsewhere on the peninsula. In the summer, fairways and the semi-roughs (between fairways and roughs) are cut weekly to about 10 mm and 16 mm respectively. S. stigmaticus is absent from fairways, but occurs in some areas of semi-rough. It is unclear whether S. stigmaticus survives mowing or if semi-rough represents a sink-habitat for grasshoppers dispersing from adjacent rough where scattered colonies occur. In the roughs, S. stigmaticus is found on mown areas, and on unmown but dry free-draining mounds of semi-natural grass (Fig.
Mowing in summer can be highly damaging for nymphs and adult grasshoppers (
Over 25 years of observations at Langness suggest that re-introducing grazing will allow S. stigmaticus to spread beyond its current strong-holds around rocky outcrops where grass is naturally short and sparse as a result of thin soils, salt spray and rabbit grazing. Overall, these observations accord with those from elsewhere in Europe. In the Netherlands, the population density of S. stigmaticus was found to increase in response to grazing of tall grasslands by cattle (
Since 2002 there have been some beneficial changes in management for S. stigmaticus at Langness, and an improved local recognition of the areas of importance for this species and its requirements, but there have also been some challenges and the beneficial effects have mostly been localized. The major management problems encountered have been socio-economic, resulting from difficulties in sourcing suitable livestock and the unintended consequences of fencing and recreational activity, rather than shortfalls in ecological knowledge. Grazing remains the preferred solution for achieving suitable habitat, but mowing in winter may need greater consideration because of continued problems in integrating livestock with public access.
Conservation action for S. stigmaticus has, in summary, now included species protection (1990), site protection (2000), distribution mapping (1964 onwards), management agreements for fenced grazing funded through agri-environment payments (2001–2012), consented grazing (discussion ongoing post-2012), and gorse clearance with fenced grazing facilitated as mitigation for development (2014 onwards). This has achieved a level of confidence that key areas can be retained in future and has had success in improving S. stigmaticus habitat in some areas, but not on the scale hoped for.
Key lessons are to: a) minimize restrictions on grazing, stating what habitat structure we need rather than prescriptive management techniques, as we have not experienced overgrazing but have frequently encountered undergrazing, so a flexible approach to grazing opportunities may be necessary; b) attempt the simplest agreement and communication route between the paying organization and the grazier; c) consider setting up a public forum for management discussions, if the landowners are happy to do this, with the benefits of encouraging public buy-in to a management strategy and the potential for minimizing problems arising from recreational access with dogs; d) consider winter cutting techniques outside of the golf course, that avoid significant risks to grasshoppers but which might allow management in areas where grazing is not currently possible; and e) continue to explore opportunities for small-scale targeted scrub control, particularly around rock outcrops, followed by grazing, where practicable, though rabbits can also help control scrub following cutting.
We thank the various owners at different times, Mr. G. Ferguson-Lacey, Mr. S. Riggall and the late Mr. J. Riggall, Mr. P. Vermeulen and Mr. J. and Mrs. F. Clarkson for permission to work at Langness, the graziers involved, Mr. P. and Ms. K. Kermode and Mr. Gelling, and especially those of them who have worked with us to introduce conservation grazing, despite sometimes trying circumstances. We also thank the late Dr. L. Garrad (Manx Museum and National Trust) for assistance with the original field survey on which this work builds, Ms. A. Thomas for information on the management history, extensive negotiations of agreements and site checks, and Mr. M. Kitching and Mr. J. Woodward, the golf course head groundsmen for two periods, for discussions on course management and local history.