Beasts of the forest

The wood In keeping with this issue’s celebration of the small, Strathspey ant specialist Hayley Wiswell looks at the vital role of the wood ant.

f you are ever walking in found in Scots pine forest, birch One of the main things that make forest in north-east Scotland, you woodland and even non-native spruce wood instantly recognisable may notice some strange mounds plantation. They are dependent on is their nest - the wood ant nest is Iof pine needles in a sunny clearing on which feed in the tree canopy. a huge, complex structure. As well the woodland floor. Take a closer look If you study trees close to a nest, you as the visible mound, underground and you will notice a hive of activity will notice trails of ants wandering tunnels and networks can spread - these mounds are home to the towards the tree top. Once aphids outwards up to three metres away. charismatic wood ant. Wood ants are are located, they are farmed much The pine needle thatch on top of the a group of mound-building ants that like cattle and a sweet liquid that the mound is delicately constructed - the are found across . In the UK aphids produce (known as honeydew) layer of needles acts like an umbrella there are three , two of which is harvested and returned to the nest over the nest, allowing rain water to are found in Scotland: the Scottish inside the ant’s stomach. When there trickle away and is also a giant solar wood ant ( aquilonia) and the are larvae in the nest to feed during panel, absorbing the sun’s rays which hairy wood ant (). the summer, protein is essential keeps the nest and its inhabitants The third species, the red wood ant and one can often observe ants at warm. The nest is always kept (Formica rufa), is found in the south ground level carrying all manner of scrupulously clean in order to keep of England. prey back to the nest. Moth bacteria and fungi to a minimum. caterpillars are a favourite, but wood Wood ants foraging on pine trees Habitat ants are capable of over-powering a collect the sap that exudes from As their name suggests, wood variety of invertebrates, including wounds - this resin contains anti- ants inhabit woodland and can be spiders and large ground beetles. bacterial and anti-fungal agents which aids cleaning. p32 ISSUE 49 Reforesting Scotland SPRING/SUMMER 2014 Beasts of the forest

Biodiversity succeeding another) and contain tens The wood ant’s home is also a haven of thousands of individuals! for other - some insects actually invade nests and depend Wood ants are territorial and defend upon the wood ants for survival. their nests aggressively by biting For example, the shining guest ant intruders (including humans that get ( nitidulus) named after too close!). They spray formic acid its glossy exoskeleton, is a ‘guest’ and although not strong enough to inside the wood ant nest, having be very harmful, it can make the bite its own quarters and food supply. area sting and this spray can travel Research [1] has shown this little ant several centimetres. to be particular about the nest it inhabits, only choosing to live in ‘5 Keystone species star’ wood ant accommodation and Not only are wood ants fascinating quickly leaves if the nest conditions and beautiful insects in their own begin to deteriorate. The shining right, but they perform a number guest ant has a distasteful coating of important roles in the forest which prevents the wood ants from ecosystem, earning them the status of devouring it and because they do ‘keystone’ species. These are species little harm in the nest, the wood ants considered to play critical roles in ignore them. the structure of their ecological community, thus affecting many There are many other examples of other organisms belonging to ‘guests’ in wood ant nests, including different trophic levels in the food specialised wood lice, chafer beetles web. and even moths. Some are harmless to the ants, feeding on detritus and Wood ants interact with organisms waste inside the nest, while others in the soil, at ground level and all the such as small predatory rove beetles way up to the tree canopy, therefore feed on the larvae and the ants’ having an impact across the whole of private food supply. the forest. They could be considered to be the largest predator in the forest Reproduction due to their biomass - one nest can Common with most social contain 10,000 individuals and there (the insect group that could be several nests within a hectare includes bees, wasps and ants), queens of woodland. Because they feed on are much larger than her workers and aphids which in turn feed on tree spend most of their time deep inside sap, and predate on herbivores such the nest. A queen starts life much like as moth caterpillars, the ants affect any other ant larva, but is fed more tree growth and are thought to effect and of a higher quality of food than predatory insect communities within ants destined to be workers. When woodland. she emerges, the queen has wings which she uses to disperse away from Despite being a top predator, they her mother-nest to find a male from a are themselves a valuable food source neighbouring nest. Once mated, she for a variety of other in the finds somewhere to start a new colony forest including birds, badgers and and her wings fall off as she will not even capercaillie. Birds are also known need them again. This stage is when to utilise a defence mechanism of the she really comes into her own - this wood ants as a method of removing amazing individual is then responsible parasites. Birds can agitate the ants to for producing all the other ants (the spray formic acid which helps to repel workers) in the colony - all of these mites and lice. ants are female and are her daughters. Males are produced later in the year If that wasn’t enough, ants also and are only around for a short while distribute the seeds of plants in order to mate with new queens. throughout the forest, and influence Wood ant colonies are known to soil communities and nutrient stores have more than one queen inside within the soil. Once abandoned, a nest at any one time, sometimes the nest provides a rich source of several may be present. Queens have material to allow new plant growth to been known to survive for up to a establish. decade or more and a single colony can survive 50 years (with one queen

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Protection warmth from the sun. Once shaded wood ants, the narrow-headed ant Wood ants need continuous out, the colony often abandons the (Formica exsecta), is also present on woodland cover to survive, and nest and moves to a more suitable this list and the Scottish although they can inhabit non- area. The Scottish wood ant is List. This mound-building species is native woodland, the structure of the considered to be more shade tolerant considered endangered in the UK and woodland is important and dense, than its relative the hairy wood ant is dependent on open woodland and commercial plantations are not and can, therefore, survive canopy woodland edges and glades. suitable. An open woodland structure closure as long as sunny gaps remain. is key, as the ants The hairy wood ant is generally found References are sun-loving closer to the woodland edge or within 1. Ölzant, S. (2001) insects and younger, early succession forests. Freilandökologische untersuchungen require optimal an der Gastameise Formicoxenus temperatures Management of woodland containing nitidulus (NYLANDER1, 8 46) inside the nest wood ants requires careful planning, unter besonderer Berücksichtigund in order for the not only to prevent damage or er Nesttemperatur (Hymenoptera: brood inside disturbance to the nests but also to Formicidae). Myrmecological News. to develop ensure that sufficient trees remain to 4, 1-10. successfully. support each colony. Without - Such rich trees to provide the ‘fuel’ for the www.woodants.org.uk temperatures are wood ants, the colony cannot survive. only achieved Hayley Wiswell is an entomologist through Wood ants are no longer listed and Natural Heritage Officer for the sufficient on the Scottish Biodiversity List, Cairngorms National Park Authority although the shining guest ant is. and a member of the National Wood Previous page: Wood ant worker. Above: Workers Since this species depends entirely Ant Steering Group. A key to wood ants transporting pupa - workers will often bring larvae on wood ants for survival, wood and other ants of the Highlands can be and pupae to the surface of the nest on sunny days found through the Highland Biological to keep them warm. Opposite: Workers gathering ants should receive some kind of on the surface of the nest thatch on a sunny day protection. Wood ants are present Recording Group website www.hbrg. to warm themselves - they will transport this heat on the Cairngorm National Parks org.uk/Atlases.html down into the nest, keeping the nest warm enough ‘Nature Action Plan’ as key woodland for brood development. Photos by Hayley Wiswell. species. Another species related to

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