Wildlife at Treborth

Over 100 species of bryophytes have been documented, with the richest diversity found in the damp, wooded areas of the botanic garden and in the calcareous flushes along the Menai Strait shoreline. The Paxton Cascade, a natural waterfall enhanced by 19th-century landscaping, supports several thalloid liverworts, including Pellia epiphylla, P. endiviifolia, Conocephalum conicum, and C. salebrosum. Notably, the tiny leafy liverwort Colura calyptrifolia, a southern species now expanding its range, is found on old apple trees.

Another leafy liverwort, though much larger, Plagiochila asplenioides, forms a lush, emergent carpet beneath willow and birch in the wet woodland at the heart of the wooded area. The widespread presence of epiphytic pleurocarpous mosses throughout the woodland reflects its consistently humid conditions. Hookeria lucens, a delicate moss resembling a liverwort with its large, translucent leaf cells visible to the naked eye, is commonly found in damp, shaded areas. Additionally, small colonies of Sphagnum palustre have been observed, and the hornwort Phaeoceros laevis is known to colonise moist, gravelly patches near the glasshouses. The floating thalloid liverwort Riccia fluitans, a relatively recent arrival, appears in substantial quantities during certain years in the original garden pond.

Treborth also boasts a rich diversity of epilithic lichen species, with an especially good representation of the Parmelia genus. While fruticose lichens are less common, the presence of vibrant Usnea colonies on select trees adds notable interest. Some of the best lichen habitats include the bark of trees lining the main drive, particularly ash, cherry, and sycamore, as well as the upper canopies of mature ash trees in the ancient woodland. Additionally, several old, well-established hazel trees in the woodland provide excellent conditions for a variety of crustose lichens.

The Botanic Garden is a haven for fungal biodiversity, thanks to its mix of woodland habitats, mature specimen trees, deadwood and meadows. From late summer onwards the familiar mushrooms and toadstools start to appear; they are easily noticed growing under the specimen trees of birch and hornbeam and you might see the notorious greenish Deathcap (Amanita phalloides), and Lactarius circellatus, which is specific to hornbeam. In the woodlands themselves the oak, birch and beechwoods have different fungi associated with them. A wide range of soil types further enhance the fungal diversity, with the Deathcap preferring the more calcareous soils while the gaudy Fly Agaric (Amanita muscaria) is associated with the more acidic soils under birch.

The Garden’s diverse soil types further enrich its fungal life. The Deathcap thrives in calcareous soils, while the striking red Fly Agaric (Amanita muscaria) prefers the acidic ground beneath birches.

Even the glasshouses reveal fungal surprises. Saprophytic fungi like the vivid yellow Leucocoprinus sulfurii, the star-shaped Geastrum striatum, and the curiously named Stinking Slime Truffle (Melanogaster ambiguus) can all be found here.

The Garden’s fungal flora, or mycota, is among the best documented in North Wales. Fungal forays have taken place here for over 30 years, offering an opportunity for experts and novices alike to discover a dazzling array of mushrooms, puffballs, brackets, jelly fungi, and stinkhorns. Since 2013, these forays have coincided with National Fungus Day in October, each year uncovering exciting finds. In 2013, Callistosporium pinicola was discovered growing on decaying pine, previously known from only one other site in Britain!

And still, countless small, overlooked species await discovery. Who knows what the next foray might uncover?

43 species are resident and breed on site, including:

• Grey Heron
• Little Egret
• Shelduck
• Sparrowhawk
• Buzzard
• Tawny Owl
• Raven
• Great-spotted Woodpecker
• Treecreeper
• 5 species of finch
• 4 species of tit
• and 3 species of thrush
• The presence of such variety provides students with plenty of opportunity to compare and research many aspects of bird behaviour especially foraging techniques.

Regular migrants which breed at Treborth include:

• Blackcap
• Whitethroat
• Chiffchaff

Three species of tern use the adjacent Menai Strait in summer and Common and Arctic Terns breed in small numbers on some of the islands there.

In winter good numbers and variety of waders and wildfowl gather along the shoreline and in the open waters of the Swellies including:

• Oystercatcher
• Curlew
• Redshank
• Dunlin
• Teal
• Mallard
• Wigeon
• Shelduck
• Red breasted Merganser
• Greylag and Canada Geese

These in turn attract Peregrine Falcon which breeds on the Britannia Bridge some years.

Redwing populate the garden in large numbers in winter along with Blackbirds and Song Thrushes from eastern Europe and Fenno-Scandinavia.

Occasional visitors include:

• Hobby
• Osprey
• Goshawk
• Lesser spotted Woodpecker
• Green Woodpecker
• Brambling
• Waxwing
• and Great Northern Diver

Among the garden’s standout contributions is its exceptional moth recording effort. Since 1989, a Robinson Light Trap has been operated nightly, producing one of the most comprehensive datasets of its kind in the UK. Over 400 species of macromoths and around 100 micromoths have been documented, with more than 350,000 individual moths recorded to date, a remarkable legacy now digitised by Dr Pat Denne.

The nightly trap has revealed fascinating population trends. Some species, like the Large Yellow Underwing and Heart and Dart, appear in impressive numbers, up to 500 per night in midsummer. In contrast, others, including nationally scarce species such as Brussels Lace and Blomer’s Rivulet, occur in small but significant numbers. Several lichen-feeding moths, like Buff Footman and Dingy Footman, have increased since the 1990s, and range expansions have brought in new species, such as Blair’s Shoulder-knot (first seen in 1996), Lime Hawkmoth (2001), and Black Arches, which is now a regular late-summer visitor.

Changes in vegetation are reflected in the moth fauna we see in the garden. Pretty Chalk Carpet, for example, has become more frequent, likely aided by the spread of its larval food plant, Traveller’s Joy (Clematis vitalba), which now climbs the garden driveway and nearby railway embankment. But not all trends are positive. Some once-common species have declined dramatically or disappeared altogether. The striking Garden Tiger has suffered a nationwide decline, as has the industrial-era icon, the melanic form of the Peppered Moth, which is now virtually extinct.

Twenty-nine species of butterflies have been recorded at Treborth, including some notable highlights. The delicate Small Pearl-bordered Fritillary has become very scarce, and both Dark Green Fritillary and Silver-washed Fritillary are now very rare and only sporadically recorded. Scarce grassland specialists such as Dingy Skipper, Wall Brown, and Small Heath are still occasionally seen, while the beautiful migrant Clouded Yellow appears very rarely during certain influx years. In woodland areas, Purple Hairstreak flits through the oak canopy each July, and White-letter Hairstreak may still cling on among the site’s remaining elms.

More familiar species, such as Meadow Brown, Gatekeeper, Comma, Peacock, and Common Blue, remain widespread and visible throughout the summer months, providing colour and movement in the meadows and along woodland edges.

Several common British bumblebees are regular visitors to Treborth’s flower-rich areas, including the Buff-tailed, Red-tailed, Common Carder, Garden, Tree, White-tailed, and Vestal Cuckoo Bumblebees. Together, they form an essential part of the site's pollination network.

The garden also supports a wide range of solitary bees: Mining bees, Leaf-cutter bees, and Nomad bees are regularly seen, with the latter parasitising the nests of other species. The Wool Carder bee, often seen defending patches of mint or Lamb’s Ear (Stachys byzantine), uses plant hairs to line its nest. These bees make use of a variety of habitats, from bare soil and flower borders to dead wood and old walls.

Wasps are also well represented, including the impressive common hornet (Vespa crabro) and the jewel-like Ruby-tailed wasps (Chrysis spp.), which parasitise solitary bee and wasp nests. A range of ichneumonids and other parasitoid wasps can also be found, playing a quiet but vital role in pest control and the broader ecological balance of the garden.

Beyond Lepidoptera and pollinators, Treborth teems with all manner of invertebrate life. In 2019, two species of woodlouse recorded at the garden were firsts for the county: Porcellionides pruinosus, found in large numbers in the compost heap, and Haplophthalmus montivagus, a surprising discovery from the limestone rockery (Hughes & Hill, 2020).

The garden’s pond and wetland margins are active in summer with dragonflies and damselflies, representing multiple species that breed or forage on site. Beetles, ranging from colourful ladybirds to less conspicuous ground beetles, are well represented. Grasshoppers are common in sunny, grassy areas, and crab spiders can often be found lurking on flower heads, waiting to ambush unsuspecting prey. The pond also supports a small but thriving population of freshwater leeches, providing evidence of the site’s clean and well-oxygenated aquatic habitats.

Together, these species form an intricate web of life, supported by Treborth’s diverse habitats and our ongoing commitment to wildlife-friendly management. From nationally important moth recording efforts to incidental sightings, the garden continues to serve as a living laboratory for observing ecological change, and a reminder of the rich biodiversity that can flourish when habitats are protected and celebrated.

References

Hughes, T.D. & Hill, D.G. (2020). The discovery of Haplophthalmus montivagus Verhoeff, 1941 (Isopoda: Oniscidea) at Treborth Botanic Garden, North Wales. Bulletin of the British Myriapod & Isopod Group, 32, pp. 65-67.

Red Squirrel (Sciurus vulgaris)
Habitat: Mature woodland, conifer stands, tree canopies, gardens
Status: Endangered in the UK; locally rare but of high conservation priority
Notes: Once native and widespread, red squirrel numbers have declined due to competition and disease carried by grey squirrels. They were first seen at Treborth in 1976 after crossing the Menai Strait from Anglesey. Evidence of breeding in the garden has been recorded, and research using hair tubes has been undertaken to monitor their distribution in the garden. The EU-funded LIFE 14 project, Red Squirrels United, supported grey squirrel control in the area to allow red squirrels to recolonise.

Grey Squirrel (Sciurus carolinensis)
Habitat: Deciduous woodland, gardens, and parks
Status: Non-native; subject to culling due to the threat posed to red squirrels
Notes: Introduced from North America, they outcompete red squirrels for food and habitat and spread squirrelpox. Once common at Treborth, numbers declined sharply after control measures began in 2006.

Bank Vole (Myodes glareolus)
Habitat: Dense ground vegetation in woodland and hedgerows
Status: Common
Notes: A key prey species for owls and carnivores, bank voles are small, chestnut-brown rodents active both day and night. They can often be heard scurrying and squeaking in the undergrowth.

Field Vole (Microtus agrestis)
Habitat: Long grass, rough grassland, and meadow
Status: Common
Notes: Abundant in the garden. The field vole is a vital food source for predators like raptors, corvids and foxes.

Wood Mouse (Apodemus sylvaticus)
Habitat: Woodlands, gardens, scrub, and rough grassland
Status: Common
Notes: Agile climbers and prolific breeders, they are common across the garden.

House Mouse (Mus musculus domesticus)
Habitat: Buildings and other man-made structures
Status: Common; recorded in small numbers around the garden
Notes: Thrives around human habitation; occasional individuals seen in sheds and around the main buildings.

Brown Rat (Rattus norvegicus)
Habitat: Anywhere with cover and food; compost areas, buildings, hedgerows
Status: Common; numbers may fluctuate but present throughout the garden
Notes: Often misunderstood, rats are intelligent and adaptable. Treborth supports low populations likely regulated by predators.

Rabbit (Oryctolagus cuniculus)
Habitat: Short grassland, woodland edge, meadows
Status: Introduced but naturalised; common, some years abundant
Notes: A familiar sight on lawns and meadows, they occasionally cause damage to ornamental planting.

Brown Hare (Lepus europaeus)
Habitat: Grassland and open farmland 
Status: Protected under the Wildlife and Countryside Act, 1981. Scarce at Treborth; not recently reported
Notes: Larger and faster than rabbits, hares rely on speed and open ground for evasion. Nationally declining, with the intensification of agriculture playing a major role.

Common Shrew (Sorex araneus)
Habitat: Woodland floor, undergrowth, grassland
Status: Common and protected under the Wildlife and Countryside Act, 1981
Notes: Small but fierce insectivores, they need to eat ~90% of their body weight daily to survive. Easily overlooked due to their tiny size and secretive habits.

Mole (Talpa europaea)
Habitat: Lawns, meadows, woodland
Status: Common
Notes: Rarely seen above ground, but their presence in the garden is indicated by molehills. Moles help to aerate the soil while hunting earthworms in intricate tunnel systems.

Hedgehog (Erinaceus europaeus)
Habitat: Gardens, hedgerows, woodland edge
Status: Protected under the Wildlife and Countryside Act, 1981. Listed on IUCN Red List as near threatened and declining. 
Notes: Formerly common at Treborth, now only rarely reported. Threatened by habitat loss, habitat fragmentation, lack of food from pesticide use and road deaths.

Noctule (Nyctalus noctula)
Habitat: Roosts in trees, hunts over open ground and woodland edges
Status: Protected under the Wildlife and Countryside Act, 1981. Regularly seen flying over the garden. 
Notes: The UK’s largest bat, often emerging just after sunset. Their fast, high-flying silhouettes are visible above the canopy.

Common Pipistrelle (Pipistrellus pipistrellus)
Habitat: Gardens, woodland edges, farmland, hedgerows
Status: Protected under the Wildlife and Countryside Act, 1981. Widespread in the UK; difficult to distinguish from soprano pipistrelle.
Notes: One of the UK’s most numerous bats and was only identified as a separate species from the soprano pipistrelle in the 1990s.

Soprano Pipistrelle (Pipistrellus pygmaeus)
Habitat: Frequently found near water, woodland edges and gardens
Status: Protected under the Wildlife and Countryside Act, 1981. Likely the commoner of the two pipistrelle species at Treborth.
Notes: One of the UK’s most numerous bats. They formerly summered in the roof of the main building.

Brown Long-eared Bat (Plecotus auritus)
Habitat: Roosts in barns, churches, trees, caves and tunnels
Status: Protected under the Wildlife and Countryside Act, 1981. Infrequent; a few records in the main garden
Notes: Known for their large ears and hovering flight, they can glean insects off leaves and bark. Particularly susceptible to pesticides.

Red Fox (Vulpes vulpes)
Habitat: Woodland edge, meadows, gardens, urban areas
Status: Widespread and common, but not in large numbers at Treborth
Notes: A highly adaptable omnivore, foxes are our only wild canid. They play an important role in rodent control.

Badger (Meles meles)
Habitat: Woodland, farmland, grassland
Status: Protected under the Wildlife and Countryside Act, 1981. Status uncertain at Treborth; occasional, unsubstantiated reports from members of the public
Notes: Social and burrowing animals, badgers leave clear signs like setts, latrines, and tracks. They are the UK’s largest terrestrial predator.

Otter (Lutra lutra)
Habitat: Riverbanks and coastal waters, including the Menai Strait
Status: Protected under the Wildlife and Countryside Act, 1981. Near threatened
Notes: Once almost extinct in Wales, otters are now recovering. Spraints and food remains found along the Strait-side cliffs suggest their presence near to the garden.

Stoat (Mustela erminea)
Habitat: Hedgerows, grassland, meadows, woodland
Status: Common but only occasionally recorded at Treborth around meadow plots
Notes: Agile and ferocious predators, stoats are recognised by their bounding gait and black-tipped tails.

Weasel (Mustela nivalis)
Habitat: Hedgerows, grassland, meadows, woodland
Status: Common but only occasionally recorded at Treborth around meadow plots
Notes: The UK’s smallest carnivore. Their small size helps them pursue prey into burrows and crevices.

Polecat (Mustela putorius)
Habitat: Woodland, farmland, grassland, wetlands
Status: Protected under the Wildlife and Countryside Act, 1981.
Notes: Once persecuted, now recovering but road deaths are a major threat. Has a distinctive ‘mask’ marking on the face. Five were live trapped 300m south of Treborth in c.2005, and some road casualties have been noted along Treborth Road (2000-2010).

Feral Ferret (Mustela furo)
Habitat: Similar to the polecat, which is the ancestor of the domestic ferret; likely escaped pets
Status: Non-native
Notes: Occasional sightings in the 1990s; they can hybridise with wild polecats and produce fertile offspring

American Mink (Neovison vison)
Habitat: Waterways, shorelines, farmland, wetlands
Status: Invasive, non-native
Notes: An invasive species that poses a serious threat to native fauna. Excellent swimmers. A few records from the Menai Strait.

Bottlenose Dolphin (Tursiops truncatus)
Habitat: Marine
Status: Protected under the Wildlife and Countryside Act, 1981 
Notes: Occasionally seen in local waters over the past 40 years in the Swellies and east of the suspension bridge. Treborth offers vantage points for occasional sightings.

Harbour Porpoise (Phocoena phocoena)
Habitat: Marine
Status: Protected under the Wildlife and Countryside Act, 1981
Notes: Smaller and shyer than Bottlenose dolphins, porpoises will generally avoid boats and other marine traffic. More easily seen in calm conditions. Occasionally seen in the Menai Strait.