COMMISSIONED REPORT

Commissioned Report No. 178 A review of wood ants (Hymenoptera: Formicidae) in Scotland

(ROAME No. F04AC319)

For further information on this report please contact:

Athayde Tonhasca Scottish Natural Heritage Great Glen House Leachkin Road INVERNESS IV3 8NW Telephone: 01463 725243 E-mail: [email protected]

This report should be quoted as:

Hughes, J. (2006). A review of wood ants (Hymenoptera: Formicidae) in Scotland. Scottish Natural Heritage Commissioned Report No. 178 (ROAME No. F04AC319).

This report, or any part of it, should not be reproduced without the permission of Scottish Natural Heritage. This permission will not be withheld unreasonably. The views expressed by the author(s) of this report should not be taken as the views and policies of Scottish Natural Heritage.

© Scottish Natural Heritage 2006

COMMISSIONED REPORT Summary

A review of wood ants (Hymenoptera: Formicidae) in Scotland Commissioned Report No. 178 (ROAME No. F04AC319) Contractor: Jonathan Hughes Year of publication: 2006

Background

This report provides an overview of the ecology, identification, distribution, conservation status as well as recommendations for monitoring and management of four species of wood ant in Scotland: Formica exsecta, Formica sanguinea, Formica aquilonia and Formica lugubris. Particular focus is given to the rare UK BAP species F. exsecta. Some thoughts on interpreting wood ants to the public are also provided.

Main findings

● Wood ants play a ‘keystone’ role in forest ecosystems in Scotland. ● Knowledge of the habitat requirements, distribution and status of F. exsecta in Scotland has increased significantly in recent years. ● Formica exsecta is almost certainly extinct in at least seven former known localities in England. ● The core population (over 80% of the UK total) of F. exsecta occurs within the forest complex of Abernethy-Glenmore-Rothiemurchus in Speyside. ● The majority of the UK F. exsecta populations appears to be P type (polygynous and polydomous) which may have developed in response to sub-optimal habitat conditions. ● The queens of F. exsecta have very poor dispersal capabilities and cannot cross patches of non-suitable habitat, therefore they probably are unable to adapt or disperse adequately in the face of rapid ecological change. ● There are at least eight current key threats to wood ants. Undergrazing, browsing and lack of woodland management are the most severe. ● There are at least seven key generic management operations and mitigation measures that will favour the survival and spread of wood ants. ● A monitoring programme is recommended for F. exsecta using line transects in three F. exsecta ‘conservation zones’ to assess population changes. ● Populations of F. aquilonia and F. lugubris appear to be relatively stable across Scotland because populations have disappeared from few sites. ● A survey of F. aquilonia and F. lugubris in northern Scotland in 2014 will provide valuable data on population change on a regional scale.

For further information on this project contact: Athayde Tonhasca, Scottish Natural Heritage, Great Glen House, Leachkin Road, Inverness IV3 8NW Tel: 01463 755243 For further information on the SNH Research & Technical Support Programme contact: The Advisory Services Co-ordination Group, Scottish Natural Heritage, 2 Anderson Place, Edinburgh EH6 5NP Tel: 0131–446 2400 or [email protected]

Scottish Natural Heritage Commissioned Report No. 178 (ROAME No. F04AC319)

Contents

Summary

Aims

1 INTRODUCTION 1

2 IDENTIFICATION 2

3 DISTRIBUTION 5

4 HABITAT PREFERENCES 8

5 COMMUNITY INTERACTIONS – ANTS 11

6 COMMUNITY INTERACTIONS – PREDATOR-PREY 12

7 REPRODUCTION, GENETICS AND NEST ESTABLISHMENT 14

8 THREATS 16

9 CONSERVATION MANAGEMENT – PAST AND CURRENT 18

10 RECOMMENDATIONS FOR FUTURE MONITORING 20

11 MANAGEMENT RECOMMENDATIONS 21

12 RECOMMENDATIONS FOR THE PROMOTION OF WOOD ANTS TO THE PUBLIC 23

REFERENCES 25

Scottish Natural Heritage Commissioned Report No. 178 (ROAME No. F04AC319)

Summary

This report provides an overview of the ecology, identification, distribution, conservation status as well as recommendations for monitoring and management of four species of wood ant in Scotland: Formica exsecta, Formica sanguinea, Formica aquilonia and Formica lugubris. Particular focus is given to the rare UK BAP species F. exsecta. Some thoughts on interpreting wood ants to the public are also provided.

Some of the main findings and recommendations are listed below:

All species

● Wood ants play a keystone role in forest ecosystems in Scotland, particularly for the composition of invertebrate communities in the canopy layer.

● There are at least eight current key threats to wood ants. Undergrazing, browsing and lack of woodland management are the most severe.

● There are at least seven key generic management operations and mitigation measures that will favour the survival and spread of wood ants, the most important being management of open spaces and harvesting operations.

● Populations of F. aquilonia and F. lugubris appear to be relatively stable across Scotland because colonies have been lost from relatively few sites.

● A survey of wood ants in northern Scotland in 2014 would provide valuable data on population change on a regional scale.

Formica exsecta

● Formica exsecta is almost certainly extinct in at least seven of previously known localities in England.

● Knowledge of the habitat requirements, distribution and status of F. exsecta in Scotland has increased significantly in recent years.

● The core population (over 80% of the UK total) of F. exsecta occurs within the forest complex of Abernethy-Glenmore-Rothiemurchus in Speyside.

● The majority of the UK F. exsecta populations appear to be P type (polygynous and polydomous) that may have developed in response to sub-optimal habitat conditions.

● The queens of F. exsecta have poor dispersal capabilities and cannot cross patches of non-suitable habitat, therefore they may be unable to adapt or disperse adequately in the face of rapid ecological change.

● A monitoring programme is recommended for F. exsecta using line transects in three ‘conservation zones’ in Abernethy Forest and Glenmore to assess population changes. Scottish Natural Heritage Commissioned Report No. 178 (ROAME No. F04AC319)

Aims

The aim of this review is to summarise the current state of knowledge on wood ants in Scotland (and in UK for F. exsecta) and make management recommendations to maintain and enhance current populations.

The long-term objective for wood ants in Scotland is twofold:

● securing viable, self-sustaining populations across the current range;

● expanding existing populations and the current range into new suitable forest and related open ground habitats.

In forests not managed for wood production, this will mean moving progressively away from intensive management to a situation where we allow natural processes and natural disturbance regimes to create conditions suitable for the persistence of viable populations over large areas of contiguous semi-natural habitat. In such ecosystems, we may eventually reach a point where no management at all is required. However, for F. exsecta, we need to manage the ‘transition period’ towards naturally sustaining ecosystems very carefully as local extinctions could occur without intervention (see below for more details on habitat preferences). In those forests actively managed for wood production, it will mean carrying out simple mitigation measures during harvesting operations to ensure the long term persistence of colonies. Scottish Natural Heritage Commissioned Report No. 178 (ROAME No. F04AC319)

1 INTRODUCTION

Why make the effort to conserve wood ants? Apart from having intrinsic value in their own right, the importance of wood ants to the forest ecosystem is well known. They affect the distribution and abundance of other ants and many other ground-dwelling, underground and canopy species, harbour a wide range or often specialist myrmecophilous invertebrates, provide an important food source for predators, disperse a significant number of seeds (particularly for ancient woodland plants), may affect the growth of trees, are vital element in nutrient cycling in forests and create physical disturbances to forest soils. Perhaps more than any above-ground woodland invertebrate, wood ants can be considered to be ‘keystone’ species in the forest ecosystem. The implications of this keystone role to conservation ecology are clear – woodlands and forests in Scotland without wood ants are lacking a vital ‘functional’ component of the ecosystem.

Two species of true wood ant (Formica rufa group) occur in Scotland: the northern or hairy wood ant Formica lugubris Zetterstedt and the Scottish wood ant Formica aquilonia (Yarr.). This paper also covers two species closely related to the wood ants: the slave-making ant Formica sanguinea Latreille and the narrow-headed ant Formica exsecta Nylander (Table 1). All four species are associated with a degree of woodland cover although the latter two species have a preference for open woodland and woodland-edge habitats.

Whilst there has been a general interest in the habits and ecology of wood ants in Britain since the Victorian period (eg Plant, 1844), their active conservation management is a relatively recent phenomenon. The cause of wood ants was given a significant boost in the 1990s with the publication of the first phase of the UK Biodiversity Action Plan (UK Biodiversity Group, 1994) which included the Red Data Book 1 species F. exsecta. Five years later the second phase (UK Biodiversity Group, 1998) included a plan for F. aquilonia and a species statement for F. lugubris. At present only F. sanguinea is not included on the UK BAP.

Table 1 Classification of ‘wood ants’ occurring in Scotland

Sub-family Subgenus Species Coptoformica Müller, 1923 Formica exsecta Nylander, 1846

Formicidae Raptiformica Forel, 1913 Formica sanguinea Latreille, 1798 Formica aquilonia Yarrow, 1955 The rufa species-group Formica lugubris Zetterstedt, 1838

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2 IDENTIFICATION

For many years the taxonomy of ants allied to Formica rufa where at “the centre of a colossal nomenclatorial tangle” (Yarrow, 1955). The confusion was solved in Britain, at least temporarily, by Yarrow’s (1955) revision of the British Formica rufa group, but probably further revisions will follow (see Seifert, 1991, for examples of phenotypic variation in the rufa group). The descriptions of the worker caste of F. aquilonia and F. lugubris in Table 2 are adapted from keys by Yarrow (1955), Bolton & Collingwood (1975), Collingwood (1979) and Agosti & Collingwood (1987). These keys also contain couplets to females and males, which often offer better diagnostic than workers.

Table 2 Key differences between the worker castes of F. aquilonia and F. lugubris

Formica aquilonia Formica lugubris

1. Long hairs on the mesopleuron almost entirely 1. Long hairs on mesopleuron arise over the whole restricted to lower anterior part so that when the surface so that when viewed from above the insect is viewed from above its sides do not sides of the insect appear very hairy. Hairs appear conspicuously hairy. Hairs shorter than longer and extending over the whole alitrunk in F. lugubris and mainly on the promesonotum. dorsum.

2. Dorsal surface of petiole without long hairs. 2. Dorsal surface of petiole with long hairs.

3. Temples usually with short outstanding hairs 3. Temples usually with copious long outstanding which rarely form a conspicuous fringe around hairs forming a conspicuous fringe which the back of the head and are sometimes extends forward beneath the eyes. wanting (smaller workers).

4. Workers are smaller and less polymorphic than 4. Workers polymorphic, generally larger and F. lugubris. often more aggressive than F. aquilonia.

5. In Scotland they tend to build larger, steeper 5. In Scotland they tend to build flattish, often mounds than F. lugubris, in denser shade. more loosely thatched mounds away from shade.

The five characteristics given in Table 2 are all variable and it is advisable to examine a number of workers (and queens and males if available) from the same colony. Examining several ‘fresh’ workers in the field with a x20 hand lens often offer a better diagnostic than examining one or two mounted ants under the microscope. The first character is the one I use to distinguish the two species. With a hand lens, examine the top of the thorax in profile against the light. Formica aqulilonia should have up to two short hairs whereas F. lugubris will always have more than two longer hairs. The fourth item in Table 2 is not particularly reliable because small F. lugubris and F. aquilonia workers often are similar, and is given here only as an aid to help distinguish the two species in the field. With some practice it is possible to use nest location and character as an aid to identification.

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Phillips (2000) provided some useful ‘notes’ on distinguishing the two species from his wood ant postal survey:

“a. crucial difference is the hair fringe around the back of the head

b. facial microsculpture is only obvious when one has a series of specimens to compare

c. the general appearance of F. aquilonia is ‘orange’ with light brown markings and larger specimens can appear almost hairless. Larger workers of F. lugubris are significantly hairier and generally darker in colour. The hairiest specimens of F. lugubris were from the Loch Sunart area.”

Formica sanguinea and F. exsecta are much more easily distinguished from each other and from both F. aquilonia and F. lugubris. Morphologically, F. sanguinea workers can be distinguished from the other three species by the presence of a distinctive ‘notch’ in the medial portion of the anterior clypeal margin (Figure 1).

Figure 1 Clypeal notch in a Raptiformica species (Formica wheeleri)

See http://www.myrmecos.net/formicinae/ForWhe1.html

In the field this species is quickly distinguished by the brighter red colour of the thorax, its larger size (particularly in relation to F. aquilonia) and its more aggressive nature. Furthermore, unlike the other three species, F. sanguinea is not a mound-building ant, preferring to nest in dry tree stumps, under stones and on sunny banks in open conditions. Formica sanguinea is a social parasite, or ‘slave-making’ species. The queen enters the nest of a Serviformica species (F. fusca and F. lemani in Britain), killing the host queen and appropriating worker pupae which hatch into ‘slaves’. Nests with F. sanguinea and F. lemani (or F. fusca in a few parts of Scotland) are therefore a useful way of identifying this species. Note though that the other species considered here are also known to employ temporary social parasitism to found new colonies so the presence of nests with mixed species does not necessarily mean the species is F. sanguinea. Formica exsecta is also readily identified in the field by the presence of a very deeply excised occipital margin of the head, which can be seen with a x10 hand lens (Figure 2). It is also distinctly smaller than the other species by around 1–2mm and very aggressive when its nest is disturbed.

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Figure 2 Excised occipital margin of head in a Coptoformica species (Formica exsectoides)

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3 DISTRIBUTION

Formica lugubris range extends from the Pyrenees throughout Siberia and northern European mountains to Japan. In Europe, it reaches from central Italy to northern Norway (Collingwood, 1979). It is an abundant species in Scandinavian boreal forests and in the UK is locally common in parts of northern England and Scotland. There are also a few colonies recorded from southern Ireland (Breen, 1977). It is classed as lower risk/near threatened on the IUCN’s Red List of Threatened Species. In Scotland, F. lugubris is less widely distributed than F. aquilonia. The majority of the population in Scotland is concentrated in a few key areas, all of which are associated with large, reasonably continuous, forest habitats. It is likely that F. lugubris has exploited new plantations contiguous with existing semi-natural woodland. Isolated plantations do not normally contain wood ants as their dispersal ability is limited. The strongholds for F. lugubris are in the Glenmore-Abernethy-Rothiemurchus forest complex, Deeside (extending into Mar Lodge Estate), Glen Affric and the woodlands around southwest Loch Ness, the north slopes of Loch Sunart and Culbin forest (Collingwood, 1961). Outside these core areas there are strong populations in Longart Forest near Garve and in the Black Wood of Rannoch. The long-term viability of populations outside these areas is questionable and will depend on factors such as climate, woodland management and forest expansion. Formica lugubris occurs far less frequently in small isolated semi-natural woodlands than F. aquilonia, suggesting it is less viable than F. aquilonia in severely fragmented landscapes in Scotland.

Formica aquilonia extends from the eastern European Alps to Siberia and from northern Italy to northern Norway. It is the commonest wood ant in the Scandinavian boreal forests but in the UK it is absent from England and Wales. It is classed as lower risk/near threatened on the IUCN’s Red List of Threatened Species. In Scotland F. aquilonia is widely distributed outside the central belt and the Borders and away from the east coast. It is known from Skye and Arran Islands and occurs as far north as west Sutherland. Like F. lugubris, F. aquilonia tends to form large, stable populations in large continuous areas of forest, notably in the Glenmore-Abernethy-Rothiemurchus forest complex, Deeside, Glen Affric, Culbin forest and parts of south Argyll. Elsewhere F. aquilonia can be found in small woodland fragments. Detailed field surveys from Ross-shire and Sutherland suggest that isolated woodlands that harbour F. aquilonia are almost always of ancient origin (Hughes, 1997a, 1999). Formica aquilonia appears to be more persistent in smaller isolated sites than F. lugubris, possibly because is more tolerant to climatic extremes or because of its higher tolerance to shade. Like F. lugubris, F. aquilonia will spread into plantation forests contiguous to relict populations and usually is associated with fragments of ancient semi-natural woodland.

Formica sanguinea is widely distributed across Eurasia from Portugal to Japan and Iran to arctic Norway. Its distribution is disjunct in Britain, with strongholds in Surrey, Berkshire and the Wyre Forest and the central Highlands of Scotland. It is not listed on the IUCN’s Red List of Threatened Species. Unlike the other species considered in this review, F. sanguinea is probably significantly under-recorded in Scotland. It occurs as far north as Glen Strathfarrar, East Inverness and Migdale in Sutherland (Hughes, 1994, 1997b) and there are pre-1960 records as far south as the Black Wood of Rannoch (Barrett, 1979). Again, Glenmore-Abernethy- Rothiemurchus forest complex and Deeside are its probable strongholds but it can also be found in suitable habitat in Culbin forest and Glen Affric.

Formica exsecta ranges from central Spain to the Urals, occurring as far as northern Norway and to the Apennines. In the UK it has a highly disjunct distribution, having never been recorded outside south and southwest England (where it is now largely extinct) or the Highlands of Scotland. It is not listed on the IUCN’s

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Red List of Threatened Species. In Scotland, F. exsecta is restricted to the Glenmore-Abernethy-Rothiemurchus complex, Carrbridge, Mar Lodge Estate and the Black Wood of Rannoch. Recent surveys (Hughes, 1997c) have failed to confirm 1954 and 1957 records from Amat and Plodda Falls in Glen Affric, respectively. In England, this ant has disappeared from numerous former localities, most of which are listed in Yarrow’s (1954) comprehensive paper on the status of F. exsecta. It now survives in only one locality in England, Chudleigh Knighton Heath in Devon, which is an SSSI, and a Devon Wildlife Trust reserve (Stradling and Hoy, 1991) (Table 3).

Table 3 The distribution and population status of F. exsecta

Locality of F. exsecta Current population size Historic and current sources

Scotland Mar Lodge Estate, Two or three nests. Probably under- Donisthorpe (1927) reported ‘two large nests near Braemar recorded in east Cairngorms near a path’; Hughes 1998 pers.obs. Carrbridge, Speyside More than 16 nests Collingwood, 1961; Scottish Wildlife Trust (SWT) surveys; eight-figure grid references surveys by Gus Jones from 1994 to present Glenmore- 110 to more than 130 nests, although Donisthorpe, 1911 from ‘Aviemore’; Harwood Rothiemurchus, many recorded are probably small from ‘Nethy Bridge’, 1921; Benson recorded Speyside ‘satellite’ nests males in the Lairig Ghru in 1952 (All listed in Yarrow, 1954); Beare, 1913; Hoare et al., 1996; Hughes, 1997c; 1995 SWT survey records Abernethy Forest, More than 150 nests although many are Post 1995 SWT survey records; RSPB survey Speyside probably small ‘satellite’ nests records; University of Aberdeen records Black Wood of Around six nests within a field at East Donisthorpe photographed a relatively large Rannoch, Perthshire Camghouran farm (possibly another six mound of F. exsecta in 1913 (Donisthorpe, un-mapped nests nearby) 1927); Collingwood reports that nests at the ‘far end of Loch Rannoch…near the road’ in the 1950s had disappeared by the mid 1990s (Collingwood in a letter to David Phillips, SNH, held by J. Hughes); Hughes (1997c); Gus Jones notes three to six nests in a nearby felled Sitka spruce area and some in an field on the other side of Camghouran wood (Anon, 2004) Plodda falls, Glen POSSIBLY EXTINCT Weatherill, 1939 Affric. Invernesshire Unconfirmed record with no specimens. Not confirmed by recent surveys Amat Forest, POSSIBLY EXTINCT L. Christie, 1954 (C. A. Collingwood, Easter Ross Confirmed record with specimen. pers.comm.) Not confirmed by recent surveys

England Bournemouth area EXTINCT F. Smith – first UK record of the species in (‘Poole-Ringwood- Seemingly thriving populations recorded 1865; Donisthorpe from 1905 and 1910 Boscombe triangle’) between 1865 and 1910. Last seen in (from Yarrow, 1954); P. Atewell from the area by P. Atewell in 1967 C. A. Collingwood, pers.comm. Lyme Regis, Dorset EXTINCT This record was questioned by Nevinson in Donisthorpe (1927) Yarrow (1954)

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Table 3 (continued)

Locality of F. exsecta Current population size Historic and current sources Woking, Surrey EXTINCT. Record from a specimen in the Crawley from 1913 ( J. Pontin, pers.comm.) Hope Museum, Oxford New Forest – EXTINCT A. N. Brangham, G. Nixon and D. Stanbury Brockenhurst, 1930s records suggest at least a small in Yarrow (1954); J. Pontin 1971 ( J. Pontin, Lyndhurst and near population in the New Forest. Last seen pers.comm.) Beaulieu road 1971 Parkhurst Forest, EXTINCT E. A Butler in Donisthorpe (1927) Isle of Wight Yarrow (1954) states ‘it seemed to be abundant’ in Parkhurst during the first decade of the 20th century Bewdley, Worcester EXTINCT Blatch in Donisthorpe (1927) No specimens taken, possibly a mis-identification for F. sanguinea which is abundant in the area Land’s End, Cornwall EXTINCT Isabel in Donisthorpe (1927) Suspect record based on the presence of the myrmecophilous beetle Dinarda hagensii Morewenstow, EXTINCT G. M. Spooner in 1960s (C. A. Collingwood North Cornwall Unknown population size pers.comm.) Bovey Tracey/Bovey EXTINCT Hamm in Donisthorpe (1927); G. M. Spooner Heath, Devon ‘Several nests’ in 1948 and 1949 had (1950) in Yarrow (1954); Perrett & Stradling dwindled to three nests in 1998. (1998); Stradling, 2004, pers.comm. Recently became extinct due to motorbike scrambling and competition with F. rufa Lustleigh, Devon EXTINCT Perkins from 1916 in Yarrow (1954) One nest last seen in 1960s by C. A. Collingwood Chudleigh Knighton 42 nests Perkins from 1953 in Yarrow (1954); Ramel Heath, Devon (1994); England (1996); Perrett & Stradling (1997).

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4 HABITAT PREFERENCES

There are a number of factors that affect the habitat or niche preferences of wood ants including:

● microclimate (relatively high levels of insolation are required to raise nest temperatures to levels required for successful brood rearing);

● food supply (particularly aphid-bearing trees);

● competition from other ant species;

● substrate character;

● type of social organisation (polycaly versus monocaly);

● dispersal capacity.

Evidence from numerous field surveys and studies (eg Kutter, 1965 for F. lugubris in the Alps, Hughes, 1975 for F. lugubris and F. rufa in N. Wales; Breen, 1979a for F. lugubris in Ireland; Hughes, 1997a and 1999 for F. aquilonia and F. lugubris in N. Scotland; Hoare et al., 1996 for F. exsecta in Scotland; Punttila, 1996 for wood ants in Finland) and more recently from modelling (eg Maggini et al., 2002 for F. exsecta in Switzerland and Dures, 2004 for F. lugubris and F. aquilonia in Scotland) has provided a reliable picture of the habitat preferences of each of the four species (Figure 3). Early successional forest, permanent open glades and forest edge tend to be colonised by the territorial species F. sanguinea and F. exsecta. These will only persist as long as the tree canopy remains open (Punttila et al., 1996). Formica lugubris also has the capability of colonising young forest but tends to thrive more when it has access to at least some larger trees. There is also some evidence from Finland that F. lugubris is dominant in fragmented woodland landscapes. This is probably due to the greater area of edge habitat. In a North England plantation forest, 76% of F. lugubris nests were found within 5m of the forest edge (Douglas and Sudd, 1978). This figure is probably lower in semi-natural woodlands because of its greater structural diversity but nevertheless provides a useful basis for qualitative observations.

Figure 3 Niche preferences for four wood ant species in Scotland

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Formica aquilonia tends to dominate in larger, continuous forests and can tolerate denser stands than F. lugubris (Punttila et al., 1994). The ability of F. aquilonia to withstand deeper shade is thought to be related to its polygynous (multiple queen) and polycalic (satellite nest structure) colony organisation (Rosengren & Pamilo, 1983). In northern Europe, the largely monogynous F. lugubris is less adapted to exploiting shady conditions but appears to have a competitive advantage over F. aquilonia when colonising wind-thrown or clear-felled areas. Large sized mated queens with relatively higher fat reserves (Keller and Passera, 1989) may be able to found colonies more rapidly than F. aquilonia through temporary social parasitism of Serviformica species. In Scotland, most or all F. lugubris colonies are polygynous (Collingwood, pers.comm.), so these effects from monogynous F. lugubris in Scandinavia may not be as pronounced in Scottish populations.

Forests of different age groups alleviate the effects of competition and allow persistence of the two early successional species F. exsecta and F. sanguinea, both of which are under-represented in Scotland. Conversely, dense regeneration or evenly-aged plantation forests tend to exclude early successional species and favour F. aquilonia, which may persist along the rides of plantation forests even after complete canopy closure (Hughes pers.obs.). In general the number of ant species is lower in mature and old growth stands and declines rapidly after canopy closure (Punttila et al., 1994). Conversely, clear-felled areas are also detrimental to wood ants as colonies lose their primary food source (aphid colonies on trees) and their orientation ability which is based on visual cues (Rosengren & Pamilo, 1978).

Nests or localised populations are often situated on south- southeast-facing grounds (Hughes, 1999 for F. aquilonia and F. lugubris in north Scotland; Dures, 2004 for wood ants in Glen Affric, Felber, 1997 for F. exsecta in Abernethy) due to relatively higher insolation levels. At the micro-geographic scale, all the species have a preference for sheltered, sunny hotspots (Klimetzek and Faas, 1994) and will move or abandon nests in search of illuminated spots – for example when a tree grows between the nest and the place illuminated by the morning sun. Nests will also be moved if shadowed by lower vegetation such as ericaceous shrubs or Pteridium, although Breen (1979a) reports incidences of nests actually being moved into patches of Pteridium, possibly for exploiting extra-floral nectaries. Turnover rates can be as high as 22% per year (Klimetsek, 1973 for F. lugubris) although Breen (1979a) reported a much lower turnover rate of 9% for F. lugubris in more uniform plantation forests in Ireland.

Formica exsecta requires nest temperatures of about 28–30°C for optimal brood development (Maggini et al., 2002). Unlike the true wood ants, F. exsecta cannot increase nest temperature by the production of metabolic heat (Seifert, 2000). It is therefore strongly associated with forest edges and has preference for dry sites where the underlying substrate heats up rapidly (Maggini et al., 2002). In Scotland, it can be found nesting in small mires within the Caledonian pine forests but this habitat is likely sub-optimal. Maggini et al., (2002) reported a preference for herbaceous vegetation of around 10cm in Switzerland, which provides ants with protection from wind and bird predation. In the same study, ants where largely absent from sites heavily grazed by red deer. Optimal habitat for F. exsecta appears to be open, well drained habitat on the edge or within forests containing scattered shrubs such as juniper, which appears to be particularly important in Scotland as a source of aphid honeydew (Felber, 1997). As open habitats yield to forests, insolation (and therefore brood rearing success) declines and competition from F. lugubris and eventually F. aquilonia is likely to increase.

In relation to other Coptoformica species, F. exsecta is considered by Seifert (2000) to be a generalist that will colonise a variety of “very different open or slightly shaded habitats, which must have medium term

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stability at least…sites with rapid plant succession, with high nitrogen input or sites within the inundation plans of rivers are not colonised”. In Scotland, F. exsecta and F. sanguinea tend to be associated with the lower slopes of the Abernethy-Glenmore-Rothiemurchus forest complex at elevations of around 200 to 400m. In Northern Scotland F. aquilonia and F. lugubris range between 15 and 300m and between 30 and 150m, respectively (Hughes, 1999).

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5 COMMUNITY INTERACTIONS – ANTS

A number of studies on ant communities in boreal forests have concluded that the mound building, territorial wood ants (in this case F. aquilonia, F. sanguinea and F. lugubris) have a major structuring force on ant assemblages (eg Savolainen & Vepsalainen, 1988, 1989; Savolainen et al., 1989; Punttila et al., 1996). These three species affect the distribution and density of the species subject to social parasitism (F. lemani, F. fusca) and may also displace or at least affect the foraging habits of other ant species.

The dominance hierarchies are often complex and depend on factors such as time of day and the type of habitat. For example, F. exsecta will reduce the presence of Myrmica species on baits but not their overall density in the area around the baits. Where F. exsecta is present, Myrmica species will shift their feeding times to evening and night-time when temperatures are lower and F. exsecta is less active. By occupying these different ‘temporal niches’, it seems that Myrmica species can co-exist with more aggressive wood ants (Vepsalainen & Savolainen, 1990). Similarly, “variability in openness, successional age and moisture in young forests…alleviate the effects of competition and slave making, enhancing the co-existence of species” (Punttila et al., 1996). Clearly, F. exsecta will suffer from competition from the larger wood ants where the habitat is suitable for all four species. This partly explains why populations of F. exsecta in Scotland are largely confined to larger open spaces or woodland edges. The other major factor is habitat availability and the need for relatively high rate of springtime insolation, independent of influence from competition by other ant species.

The ant community structure is further complicated by the fact that competition between top predators may actually benefit subordinate species, eg, F. lugubris displacing F. sanguinea can increase populations of F. lemani. Conversely, if F. sanguinea becomes established in early woodland successional habitat at the expense of F. lugubris or F. aquilonia, the population of F. lemani will decrease as a result of parasitism and colony destruction. As a knock-on effect, Lasius niger agg. may then increase around F. sanguinea nests as a result of decreased competition from F. lemani (Punttila et al., 1996).

Perhaps the most important inter-specific interaction for conservation ecology is between F. lugubris and F. aquilonia as these occupy the most similar niches. Where both species are present, adequate habitat heterogeneity (particularly diverse woodland structure) may be vital in preventing species displacement and causing local extinction. This is particularly the case in Scotland where suitable habitat is often scarce and the two species may be in direct competition. Even in large forested areas, the actual area of suitable habitat may be very low, due in large part to heavy shading caused by plantation forestry, forcing wood ants to use management access rides and the edges of occasional forest openings.

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6 COMMUNITY INTERACTIONS – PREDATOR-PREY

Studies on predator-prey interactions in wood ants in the UK have focused on Formica rufa in England. These have shown that wood ants play a significant role in shaping invertebrate communities in the tree canopy (Skinner and Whittaker, 1981; Whittaker and Warrington, 1985) and around the environs of the nests (Laakso and Setälä, 1998). The main effects are due to predation of a wide range of invertebrates and boosting populations of aphid species which form mutualisms with ants.

Because many of the insect preys are herbivorous, wood ants may promote the growth of trees due to reduction in defoliation (Ito and Higashi, 1991, Mahdi and Whittaker, 1993). In the UK, there is typically 5% less leaf area removed by phytophagous insects on ant-foraged trees (see Fowles, 1994). These effects on tree growth appear to be slight and are mainly manifested through greater elongation of shoots (Mahdi & Whittaker, 1993). The positive effects on tree growth may be offset by the extra sap intake from increased aphid populations tended by ants. For example, Mahdi and Whittaker (1993) showed that the aphid Symidobius oblongus is 82 times more abundant on birch trees attended by ants than those on trees not visited by ants and Periphyllus testudinaceus produced 400 times the quantity of honeydew on sycamores populated by wood ants. Punttila et al., (2004) have shown that the health of upland birchwoods in Finland is enhanced by the presence of wood ants due to their predation of autumnal moth (Epirrita autumnata) which in the absence of ants is more likely to defoliate and kill trees in years of high population levels. These findings suggest that the presence of ants can stabilise the forest ecosystem through vital ‘balancing’ effects.

Wood ants have mutualistic relationships with certain species of aphid, eg Cinara pinea on Scots pine, Cinara piceae on spruces (Figures 4 and 5), Periphyllus testudinaceus on sycamore, Betulaphis quadrituberculata, Glyphina betulae and Symidobius oblongus on birch and Lachnus roboris on oak (Breen 1979b). Casual observations in northern Scotland suggest that S. oblongus is a particularly important species in birch-dominated woodlands (Collingwood and Hughes, pers.obs.; Hughes, 1999) There is limited information on F. exsecta-aphid interactions, but these ants are known to utilise root aphids as well as canopy invertebrates. The ants tend the aphids and thereby afford them protection from predators. In exchange, the aphids produce honeydew which can account for around 70% of the food requirements of the colony at certain times of the year (Skinner, 1980).

Figure 4 Formica lugubris attending Cinara piceae on Sitka spruce. Photograph by John Breen from Kilcoran Wood, Ireland (see also Breen 1979b)

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Figure 5 Formica lugubris attending Cinara piceae on Sitka spruce. Photograph by John Breen from Kilcoran Wood, Ireland (see also Breen 1979b).

Aphids without mutualistic relationships with ants can often make up the main food items (Skinner, 1980) and occur in significantly lower numbers on ant-foraged trees (Mahdi & Whittaker, 1993). The aphid species used by wood ants in Scotland are probably similar to those in northern England although in Scot’s pine dominated areas Cinara pinea is probably preferred. More studies are needed on the species of aphids milked and predated on non-native conifers in Scotland. In northern England, the non-honeydew part of the F. rufa diet consisted mainly of the aphid Drepanosiphum platanoides and the lava of winter moth, Operophtera brumata, although other invertebrates, notably bibionid flies, were also taken (Skinner, 1980). However, Skinner (1980) noted that F. rufa is probably opportunistic in exploiting ‘upsurges in prey populations, or anomalies of abundance in special local habitats’. This suggests that type of prey may vary greatly between types of woodland, regions and years.

In the early 1980s, the potential of wood ants as biological control agents for tree pests was explored in a comprehensive study by the Italian Forestry Ministry. This involved lorry loads of wood ants being moved between forests in an effort to increase timber yields. Results were inconclusive and this novel technique is no longer practiced on a large scale.

Wood ants are a valuable food source for a number of predators, including many birds and mammals. Analysis of fragments of capercaille droppings from Abernethy has shown that F. sanguinea, F. aquilonia and possibly F. exsecta are eaten by the birds, along with Serviformica and Myrmicine ant species (Collingwood, 1998).

Recent research has shown surprising influences of wood ants on invertebrate assemblages in the soil around the nests. Laakso and Setälä (1997) showed that the biomass of earthworms was approximately seven times higher in nests than in the surrounding soil – probably due to favourable temperature, moisture, acidity and food supply. This suggests that where ant populations are abundant, soil invertebrate communities are significantly modified in the same way canopy communities are. However, Laakso (1999) concluded that the overall effects of wood ants on soil fauna are relatively weak as only some taxa are affected. Workers cannot effectively forage inside the humus and litter layers because of their relatively large body size (Laakso and Setälä, 1998, 1999).

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7 REPRODUCTION, GENETICS AND NEST ESTABLISHMENT

There is much research on this subject (see for example Pisarski, 1972; Dobranzska, 1973; Fortelius et al., 1987; Pamilo, 1991; Pitnick et al., 2001; Brown & Keller, 2002; Brown et al., 2002; Seppa et al., 2004), often using F. exsecta as the study organism, and only a brief summary of current state of knowledge can be given here. Table 4 summarises the colony structure and nest founding strategies of the four species. For F. exsecta, a detailed knowledge of the reproduction and colony structure in England and Scotland might aid us in the conservation of the species.

Table 4 Colony structure and dispersal strategies

Species Colony structure Dispersal strategy Nest founding Position in strategy dominance hierarchy F. exsecta Mostly polygynous Nest budding and Colony budding Subordinate to larger and polycalic (P type) nuptial flights or ground and social wood ants and but possibly some dispersal in P type parasitism of F. sanguinea. Dominant monogynous, monocalic populations. Nuptial queenless nests of over Serviformica colonies (M type) in flights or ground Serviformica species species Scotland (see Dallas dispersal in M type et al., 2001 for genetic populations evidence of social polymorphism in Scotland). Probably mainly P type in England F. lugubris Mostly polygynous Budding and limited Colony budding Co-dominant with (C.A Collingwood, dispersal of mated and temporary F. aquilonia. Possibly pers.comm.) and queens. Nuptial flights social parasitism of displaces F. aquilonia in weakly polycalic are rare, but on July Serviformica species ideal habitat but multiple 1996 at Kieldermorie niche availability Forest J. Hughes & appears to facilitate C. A. Collingwood co-existence in most observed numerous localities queens and males swarming on the ground in the vicinity of the nests. Breen (1979c) reported ‘flights’ of F. lugubris in southern Ireland while Pontin (1990) has observed intra-nest copulation in F. rufa in England. F. aquilonia Polygynous and Budding and limited Largely by budding. Co-dominant with strongly polycalic dispersal of mated Temporary social F. lugubris queens parasitism of Serviformica species may occur F. sanguinea Uncertain. Young nests Mated queens seek out Facultative social Dominant, although monogynous, old ones nests of Serviformica parasitism of populations in Scotland may be polygynous Serviformica species never large enough to displace wood ants

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Formica exsecta has two distinct types of colony: M type, monogynous with simple social organisation (normally monodomous nests with no satellite nests); P type, polygynous with complex colonial networks. The two colony types exist in sympatry but usually as separate sub-populations (Seppa et al., 2004). The ratio of the two types is affected by a number of complex factors, including the availability and quality of suitable habitat. Large P type populations occur in the Alps, whereas in south Finland, M type populations predominate (Seifert, 2000).

Dallas et al. (2001) used the genotypes of two microsatellites to infer the parentage of ten colonies of F. exsecta in Scotland. The results showed that social polymorphism (ie the co-existence of M and P type populations) appeared to be the norm, with the minimum number of parents of workers from each colony ranging from one to ten. However, they stressed that the minimum number of parents may have been underestimated (due to sampling design) and it is more likely that Scottish populations of F. exsecta are largely, or wholly, P type. Genetic differentiation between P type populations of F. exsecta has been shown to be high between ‘pastures’ (hot spots of suitable habitat separated by 1km of non-suitable habitat) (Liautard & Keller, 2001). This suggests that effective queen dispersal in P type populations of F. exsecta is poor at a microgeographic scale. Sundstrom et al. (2003) have also demonstrated that limited queen dispersal also occurs in M type populations. This is interesting in that monogyny is thought to be associated with extensive mating flights and high levels of gene flow. These findings have implications for the conservation of F. exsecta in the UK in two ways: a. The P type populations are likely to be expanding primarily by colony budding, ie, where a mated queen establishes a nest with a group of workers near to the parent nest. The existing colonies are therefore expanding relatively slowly at a local scale. They do not appear to have capability to disperse medium to long distances, or disperse through non-suitable habitat effectively. Their populations are therefore more susceptible to rapid changes in habitat structure eg rapid tree regeneration, scrub invasion. b. As most queens are recruited within their parental colonies, inbreeding depression is likely due to limited gene flow.

Research has also shown that P- type populations produce more males than females, at least until the number of queens in the polygynous colony reaches critically low numbers (queen replenishment hypothesis). These findings are supported by field observations in Scotland where almost all nests containing sexual forms, contained males only (Hoare et al., 1996). Males will disperse considerably further than queens (which may explain Benson’s 1952 records of males from the Lairig Ghru) but this does not appear sufficient to facilitate significant gene flow between metapopulations.

The predominance of polygyny in F. exsecta in the UK may be a response to sub-optimal habitat conditions due to the fact that independent colony founding associated with monogyny is a much riskier strategy in a ‘stressed’ environment (Keller, 1995). The probable rarity of M type populations in the UK suggests we need to expand the core area of suitable habitat or improve the quality of the existing habitat. The presence or absence of M type populations in the future would be a useful indicator of the success or otherwise of any habitat management for this species. Similar studies using polygynous colonies of F. lugubris in a fragmented landscape showed a lack of inbreeding and a high level of variability, mainly due to intensive but strongly male- biased gene flow (Gyllenstrand & Seppa, 2003).

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8 THREATS

The key threats to wood ants are listed below, in order of importance. These are based on observations from field surveys and known habitat requirements.

Undergrazing and/or lack of sufficient deer browsing

This is the main threat to F. exsecta and F. sanguinea in their core population areas around Speyside. In recent years, the reduction in deer populations through culling programmes has seen increasing levels of tree regeneration in the pine forests of the Glenmore-Rothiemurchus-Abernethy area. If unmanaged, this process will lead to loss of suitable habitat for F. exsecta and increased competition from the larger wood ant species. The effects of increasing regeneration has been offset in the last decade or so by extensive restoration of native pinewoods in the area – in effect the removal of non native conifers has created significant areas of temporarily suitable habitat for F. exsecta. These, and other open areas, may develop into ‘thicket stage’ growth and F. exsecta habitat may become scare for a prolonged period. In Devon, conservation grazing has been attempted but scrub encroachment remains a threat (David Stradling, pers.comm.).

Lack of woodland management

This is the main threat to F. aquilonia and F. lugubris but also to the open ground species that would benefit from reduced competition if woodland structure was more open. Thinning and ride management are vital operations, particularly within densely shaded spruce and fir forests where wood ants will not persist under the canopy. The decline of coppicing in the 20th century has been a major factor of decline in all species in Europe.

Climate change and annual weather patterns

Annual runs of wet springs are probably a factor for the severe decline in F. rufa population in the Lake District in the last 50 or so years (Robinson, 2001). C. A. Collingwood also believes that wet springs are a key factor in the health of wood ant populations, particularly those on the edge of their range. How climate change will affect ant populations in the long term cannot be predicted.

Habitat fragmentation

It is no coincidence that the most viable populations of all species occur in large contiguous forested areas with a high degree of semi-natural habitat heterogeneity. Formica lugubris appears to be more vulnerable than F. aquilonia to severe habitat fragmentation, but in general for all species the vulnerability to local extinction increases with increasing patch isolation and decreasing habitat size.

Insensitive clear-felling

Direct destruction of nests by harvesters and forwarders is a threat during forest operations. The complete removal of trees may threaten the survival of wood ants, particularly where subsequent regeneration is poor due to excessive browsing and grazing.

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Excessive grazing and browsing

This a problem for F. exsecta at Rannoch where it occurs in a severely overgrazed, cattle-trampled field. It is also a problem for F. aquilonia in upland birchwoods and pinewoods where young aphid-rich trees are absent due to excessive browsing. Ultimately, the long-term viability of some upland birchwoods containing F. aquilonia will depend on bringing deer populations to a level where some regeneration can occur.

Direct destruction of nests

This was one of the factors causing the disappearance of F. exsecta from Bovey Heath (in the form of motorbike scrambling) and recently there have been concerns that a proposed development near Carrbridge would destroy F. exsecta colonies. This threat is however far less severe or widespread than those listed above.

Diffuse pollution

Diffuse pollution from neighbouring farms and increased atmospheric nitrogen levels probably have detrimental affects on certain populations although the core areas seem not to be adversely affected. Intensive pheasant-rearing and the subsequent pollution from pheasant feed can severely impact wood ants (pers. obs. on the extinction of F. lugubris in pheasant woods in Yorkshire). More research is needed on the impact of pheasants on wood ants in Scotland.

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9 CONSERVATION MANAGEMENT – PAST AND CURRENT

There has been little recorded management targeted specifically at the conservation of wood ants. However, it is known from anecdotal evidence that certain woodland managers in conservation agencies and the Forestry Commission have at various times adapted management for ants or at least mitigated against damage. In recent years the profile of F. exsecta has risen considerably and many managers working in the Speyside area are at least aware of the habitat requirements of the species.

Specific management for F. exsecta and related open heath species has been occurring since 1996 at the Devon Wildlife Trust reserve at Chudleigh Knighton Heath where around 25 Soay sheep have been used to control scrub encroachment within a fenced enclosure. This practice coincided with a 33% decrease in the population of F. exsecta between 1997 and 1998 – in fact the areas which suffered the most marked decline were those subjected to a grazing management regime. Nests outside the grazed enclosure which remained stable during this period were those associated with large, lightly grazed (by wild deer only) grass tussocks. The authors of this work point out that the abnormally wet spring of 1998 may also have been a factor in nest losses (Perrett & Stradling, 1998). Table 5 summarises the monitoring and survey projects carried out to date on all four species.

Table 5 Wood ant survey and monitoring projects

Species Location Type of survey/ Author Repeatability monitoring F. exsecta Chudleigh Knighton Full census of all nests Stradling & Hoy, 1991; Easily repeatable Heath, Devon Ramel, 1994; England, 1996; Perrett & Stradling; 1997, 1998 F. exsecta Bovey Heath, Devon Full census of all nests Perrett & Stradling, Easily repeatable but 1997, 1998 now extinct at this locality F. exsecta Scotland Rannoch, Amat, Glen Hughes, 1997c Areas searched were Affric and Rothiemurchus marked on 1:25,000 were searched for maps so the survey could presence of ants. be repeated, although Found colonies were the intensity of search mapped and may differ significantly photographed. F. exsecta Scotland ‘Rannoch, Glenmore, Hoare et al., 1996 Repeat surveys would Inshriach, Dell Wood only be useful in and Abernethy. Nests obtaining a broad idea were measured, of population trends mapped and photographed F. exsecta Glenmore, Abernethy, Near complete census 1995 onwards ( Jones/ This survey is still Rothiemurchus, (ongoing). Most nests SWT with additional ongoing but now in a Carrbridge complex, marked, mapped and records from others, rather ad hoc manner. Scotland photographed RSPB and University of Provides invaluable data Aberdeen) on population patterns F. exsecta Glenmore, Abernethy, Monitoring transect Unknown Unknown Rothiemurchus, (commissioned by SNH Carrbridge complex, in 1997) Scotland

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Table 5 (continued)

Species Location Type of survey/ Author Repeatability monitoring F. lugubris Ross-shire and Site based survey Hughes & Collingwood, Would be simple to and Sutherland, Scotland (population estimated 1993–1996 repeat and would F. aquilonia at each locality) provide data on population changes at a regional scale All wood Scotland Postal survey. Phillips, 2000 Changes in populations ants Participants posted ants could be obtained from to be identified a repeat survey All wood Glen Affric, Loch Beinn Full census of 89 ‘wood Dures, 2004 Repeat survey would be ants a’ Mheadhoin ant’ nests but species of limited use because were not determined for species were not all nests determined F. lugubris Morrone Birkwoods Densities of nests in Hughes, 1997d A repeat survey might and NNR, Deeside, compartments based on provide insights into how F. aquilonia Scotland homogenous patches of changing vegetation vegetation (NVC) affects nest densities

Perhaps the two most useful surveys for monitoring long-term population changes are the site-based survey on F. lugubris and F. aquilonia carried out between 1993–1996 in Ross-shire and Sutherland (Hughes, 1997a), and the full census of F. exsecta in Devon (Stradling & Hoy, 1991). The second of these is effectively one large quadrat of the whole England population. Repeating these surveys would provide a picture of changing populations at a regional scale (northern Scotland) and a site scale (Chudleigh Knighton Heath). The records of F. exsecta in the Speyside area are perhaps of less value for long-term monitoring because they have been collected over a number of years and colonies tend to shift around within core population areas from year to year. However, this information is valuable for deciding where to best target habitat management.

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10 RECOMMENDATIONS FOR FUTURE MONITORING

Formica aquilonia, F. lugubris and F. sanguinea should be monitored at a national level through the continued collection and collation of site records. This will provide a crude but useful picture of persistence of the species in currently known localities. Newly established forests contiguous with existing known populations might also be checked to determine whether wood ants are spreading into new plantations. Any new records in isolated localities are not likely to be population expansions due to ants’ limited dispersal abilities. The survey of Ross-shire and Sutherland should be repeated in 2014 using the same methodology. This will provide data on changes to populations at a regional scale. The results should be made available to the UK wood ant SAP steering group and can be used as part of BAP reporting.

A full census every two years is recommended for the F. exsecta population in Devon due to its vulnerability. The same applies for the Rannoch populations in the field at East Camghouran. In Speyside, collection of data on the location of individual nests should continue on a casual basis and used to target management. A standardised, cost effective method of assessing changing populations of F. exsecta is also required in Speyside. It is recommended that three randomly placed line transects, each 1km long and 6m wide, are used within three ‘F. exsecta conservation zones’ (see below), two in Abernethy and one in Glenmore. Transects do not necessarily have to be a single 1km track (in fact this may not be possible in some zones) but could be split into 2–4 smaller transects totalling 1km. These should be repeated every three years due to the rapid pace of ecological change in the area.

In summary, monitoring of wood ants should continue through:

● Casual recording (6 or 8-figure grid references) of all species nationally, supplemented by visits to specific woodlands that have not been checked for a number of years. Particularly intensive surveying would be beneficial in the Speyside area, especially for F. exsecta, as this will help target management.

● Repeat the 1993–1996 survey of F. aquilonia and F. lugubris in Rosshire and Sutherland (Hughes, 1997a) in 2014.

● Full census of known populations at Rannoch and in Devon every two years.

● Three 1km long, 6m wide line transects, in three F. exsecta ‘conservation zones’ in Abernethy and Glenmore repeated every three years.

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11 MANAGEMENT RECOMMENDATIONS

Hughes et al., (2003) information and management guidance note lists simple operations managers can perform to encourage wood ants in woodlands. As long as the locations of nests are included in management plans, such generic recommendations are probably sufficient for F. aquilonia and F. lugubris:

● Try to mitigate direct damage when carrying out forestry operations, eg, by isolating key areas and avoiding running over nests with machines.

● Include areas of connected open spaces in new forests. When planting a new forest adjacent to known wood ant populations, keep some open space immediately adjacent to the existing nests.

● When clear-felling, retain individuals or groups of trees (say 8–12) near nest mounds as a habitat refuge for the ants – these can be immature trees, trees of poor growth form or non-crop trees.

● Maintain aphid-rich trees where possible.

● Maintain open tracks and rides, preferably through felling, coppicing or heavy thinning of self-seeded trees. Regular mowing of ride-sides is beneficial but can also cause physical damage to nest mounds.

● Encourage appropriate levels of grazing and browsing through appropriate stocking densities or deer control.

● On sites where nature conservation is the main objective, keep rides open and create temporary glades on the vicinity of wood ants.

● At a landscape scale, create and restore woodland in order to connect fragments and create semi- natural wood ant habitat networks.

Formica exsecta will require targeted management at all sites of occurrence, although only core areas of nests should be managed in Speyside with outliers at Carrbridge and Rothiemurchus left wholly or largely unmanaged (exceptions might be where volunteers might wish to ‘micro-manage’ around individual or small groups of nests). These areas where the conservation of F. exsecta takes priority over more general woodland management might be called ‘F. exsecta conservation zones’. Keeping these areas relatively open will also benefit other early successional species. Three such areas are marked on the accompanying maps, centred around two open/early successional areas in Abernethy, which main population concentration is in Glenmore. The management prescriptions recommended here should be kept under annual review. This is particularly important in relation to the required frequency of scrub and regeneration cutting, depending on levels of grazing and browsing.

Chudleigh Knighton Heath

Maintenance of open heath conditions with scattered scrub through a programme of scrub cutting (and burning if required). The aim should be to achieve 80% of open ground with 20% scrub or vegetation on first stages of regeneration distributed evenly across the site. Grazing may also be beneficial but should cease if there are continued declines in F. exsecta populations as reported in 1997–1998.

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Rannoch

Long-term reduction in cattle and sheep grazing is required at East Camghouran, if possible through Rural Stewardship Scheme agreement with the tenant farmer. Some grazing will almost certainly be beneficial as it will prevent invasion of pine seedlings but present levels are threatening F. exsecta nests through trampling, ground compaction and increased exposure to predators.

Formica exsecta conservation zone – Abernethy North

This is the largest and most stable population in the UK. Within the boundary of the zone, maintain 60% of the central area as contiguous open ground, 20% as young (up to 10 years old) trees and 20% as thicket or mature forest. This will require regular cutting or lopping of pines although the exact frequency of cutting will depend on red deer populations. All juniper should be retained.

Formica exsecta conservation zone – Abernethy North

Maintain 40% of the area as scattered open ground, 30% as young (up to 10 years old) trees and 30% as thicket or mature forest. This will require regular cutting or lopping of pine, although the frequency of cutting will depend on red deer populations. All juniper should be retained.

Formica exsecta conservation zone – Glenmore

Within the boundary of the zone, maintain 30% of the area as scattered open ground mostly around nests, 30% as young (up to 10 years old) trees and 40% as thicket or mature forest. This will require regular cutting or lopping of pine, although the exact frequency of cutting will depend on red deer populations. All juniper should be retained.

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12 RECOMMENDATIONS FOR THE PROMOTION OF WOOD ANTS TO THE PUBLIC

The profile of wood ants has been significantly raised over the last 15 years with numerous articles in newspapers and magazines. Specific articles on the plight of F. exsecta have appeared in the Press and Journal, the Scotsman and the Herald under headlines such as ‘Survival plan ready for rare ant species’, ‘Action to save forest ants’ and ‘Action to save rare ant’. In 2004, the BBC ran a series on ‘a year in the life of a wood ant colony’ on Radio 4. We can assume that many people that previously may have viewed wood ants as a pest now see them in a much more positive light. In 2003, ‘Information and management guidance note’ on wood ants in Scotland was distributed mainly to site managers and those working in forestry or nature conservation (Hughes et al., 2003). Wood ants have also appeared on interpretation boards and in visitor centres at various sites and there is now a great deal of information accessible on the internet, eg, SWT and Trees for Life websites. What has been missing are high quality photographs and artwork of the four species. These bring wood ants to life – and probably encourage people to pay more attention to the text! The ‘fascinating facts’ on wood ants provided below can be used on interpretation boards, displays, leaflets, etc.

Fact 1 – Large wood ant nests contain hundreds of thousands of worker ants. Queens and male ants remain in the nest and are tended by the workers. Unlike many British ant species, which have annual ‘marriage flights’ where the queens and males leave to nest to mate, wood ant sexual forms are rarely seen outside the nest mound.

Fact 2 – Wood ants queens and workers are known to raid the nests of other common black ants (F. lemani, F. fusca) where they then enslave workers, which eventually leave the nest or die out. This process is called ‘temporary social parasitism’ and is one method used to found new wood ant colonies. The blood-red slave- making ant (F. sanguinea), always founds its nests this way.

Fact 3 – There is a species of ant, wholly different in appearance to wood ants, which actually lives within wood ant mounds. It is called the ‘shining guest ant’ (Formicoxenus nitidulus) and cannot live outside wood ant nests. This ant is just one of a number of ‘myrmecophilous’ species which live exclusively within the nests of wood ants but are unharmed by their hosts.

Fact 4 – The presence of wood ants in a woodland can increase tree growth. The effects are normally slight and occur because wood ants prey upon insects that eat the leaves of the trees. This shows how ants are a ‘keystone species’ in the woodland food web.

Fact 5 – Wood ants obtain well over half their diet from ‘milking’ aphids that feed on trees and produce a sugary solution rich in sugar. In return the aphids are protected from predators by the ants.

Fact 6 – Felling trees can be good for wood ants. Wood ants require sunny gaps in the forest, and thinning and coppicing trees are generally beneficial to colonies because they mimic naturally occurring, small-scale disturbances. A note of caution though – large, unsustainable clear fells can be devastating, particularly where populations are small and vulnerable.

Fact 7 – Different wood ants have different fighting techniques. The rare narrow-headed ant (F. exsecta) is very aggressive and likes to amputate heads of other Formica species. The larger wood ants are slightly less violent and prefer biting off limbs than heads!

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Fact 8 – The formic acid produced by ants is an excellent repellent. Birds rub wood ants under their wings to help control parasites within their feathers. Enthusiastic birds will even ‘bathe’ in wood ants in an effort to rid themselves of irritating parasites.

Fact 9 – Wood ants have wars. These appear to be in response to limited resources and can be brutal affairs with corpses littering the ground in the aftermath of battle.

Fact 10 – Wood ants have few predators. However, many birds and mammals will ‘snack’ on wood ants. Analysis of capercaille droppings has shown that they feed on several ants, including wood ants.

Fact 11 – There are four species of wood ant in Scotland. The Scottish (F. aquilonia) and the Northern (F. lugubris) species are the ‘true’ wood ants of mound building fame. They prefer open woodland. The blood red slave making ant (F. sanguinea) and the narrow headed ant (F. exsecta) build much smaller nests and prefer open habitats adjacent to woodlands.

Fact 12 – Seeds of up to a quarter of ancient woodland indicator plant species are exclusively distributed by ants, including wood ants (Hermy et al., 1999). These plants are known as ‘myrmecochores’ and they usually contain external elaiosomes (structures containing sugary solution) on their seeds to attract the ants.

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REFERENCES

Agosti, D. & Collingwood, C. A. (1987). A provisional list of Balkan ants (Hym. Formicidae) with a key to the worker caste. II. Key to the worker caste, including the European species without the Iberian. Bulletin de la Societe Entomologique de Suisse 60, 261–293.

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