Snails Are Eating My House

The Garden Snail, Helix aspersa

With spring approaching fast, thoughts turn to the garden, specifically what vegetables to plant. Lettuces are always a good bet, some nice butterhead and iceberg, as they always get used. The trick is to sow them in a staggered fashion, avoiding them all coming good at the same time and having to find a plethora of lettuce recipes. Thoughts of planting them though also induces mild panic at the prospect of controlling their mollusc pests. One of the greatest of these is the Garden Snail (Helix aspersa, synonym: Cornu aspersum), a generalist herbivore that will also attack other crops as well as ornamentals in the garden (1). With its marbled brown and black shell to maintain, H. aspersa needs to take in a diet rich in calcium and its preferred diet shows plants rich in this mineral (2). Analysis of faecal matter has shown one of the most popular of these to be stinging nettles (Urtica dioica), a plant with a high calcium levels (3).
Areas with poor soil condions results in plants with low calcium levels, so H. aspersa has turn to other sources. Remarkably in 1999 damage to the paint work on houses in parts of Britany in France were shown to be the result of H. aspersa's feeding action (4). Further investigation showed that snails presented with 16 different watercolour paints showed a preference for those with higher calcium content (5).

References:

1. Capinera, 2001. Handbook of Vegetable Pests p. 570
2. Chevalier et al., 2003. Malacologia 45 pp. 125-132
3. Chevalier et al., 2001. Comptes Rendus de l'Académie des Sciences - Series III - Sciences de la Vie 324 pp. 979-98
4. Chevalier and Charrier, 1999. Rapport de Contrat pour la SOGEFI p. 42
5. Charrier, 1999. Peintures, les escargots attaquent, que choisir pp. 46-47

Guillemots and the Climate Change Mistake

Its nearly February and the weather persists in being unseasonably mild. A cold snap is forecast in the next few days but, touch wood, it shouldn't go near matching the bitterness of our previous two Irish winters. The consequences of this warm weather, garden bulbs in full bloom, frogs spawning early, may bring delight to us in banishing the darkness of winter from our minds, but they also serve to remind us of the ever present problem of climate change. It is fact that birds are breeding and singing earlier, migrant birds are arriving earlier, butterflies are appearing earlier and plants are shooting earlier (1). This blog has reported on dragonfly species increasing their European range northward into Ireland. The effects of climate change on fish species in the oceans is one of the most worrying, due to its knock on effect on other associated species and on the consequences it holds for commercial fisheries. In the North Sea, cod, anglerfish and snake blenny have all shifted their ranges further northwards (2).
 

Common Guillemots, Uria aalge, during breeding season

However, there is a risk in attributing too much to climate change and not recognising the effect humans activity may have directly in changes to species distribution and behaviour. An example of this is the virtual extinction of the Common Guillemot (Uria aalge) in Atlantic Iberia. This wonderful, chocolate-brown coloured auk numbered c. 20,000 individuals in Atlantic Iberia in the first half of the 20th century, the largest population of any seabird in the area. By 2004 it was considered quasi-extinct, with no no breeding attempts recorded since 2003 (3). Such a dramatic decline was thought to be a result of climate change as the Iberian population was at the southern most limit of the species, and thus prone to extinction under natural conditions. A reexamination of the data from the extinction however, revealed that climate change was not to blame. The largest population crash occurred from 1960 to 1974, when annually there was a decline of 33.3%. This period saw good climate conditions and higher or sustained availability of pelagic prey fish, but also marked a rapid shift away from using vegetal based nets in commercial fishing to those constructed from synthetic materials (3). This points the finger directly at another human-mediated extinction. It also shows how easy it is to attribute much to climate change without assessing the role we have directly in the survival of other species.

References:

1. Walther et al., 2002. Nature 416 pp. 389-395
2. Perry et al., 2005. Science 308 pp. 1912-1915
3. Munilla et al., 2007. Biological Conservation 207 pp. 359-371

The Many Patterned Cuckoo-Spit Froghopper

Two Cuckoo-Spit Froghoppers, Philaenus spumarius, mating

Philaenus spumarius, the Cuckoo-Spit Froghopper, is one of the commonest bugs in Irish hedgerows and gardens, especially from June to August when the green-ish nymphs are quite conspicuous due to their habit of hiding in a mass of spit-like bubbles which shield them from predators (1). The adults remain well hidden though, thanks to their excellent camouflage. However the pattern of this camouflage is highly variable, so variable in fact that it has led to up to 50 different synonyms being used for P. spumarius (2).

Cuckoo-Spit Froghopper nymph

Polymorphism such as this is common in many other animal species and while the mechanisms controlling it has been much source of debate, it is accepted that control is genetically based on alleles of gene loci (3). Although P. spumarius is of holartic distribution, levels of polymorphism have been found to be highest in the Mediterranean, now thought to be the point of origin for the species (4). Here, polymorphism is selected for based on visual selection, specifically to avoid predators during the long obligatory period of aestivation that P. spumarius undergoes. Since vegetation on which the eggs are layed and development takes place soon vanishes in the harsh weather of the Mediterranean, individuals soon have to move to other hosts, various shrub and tree species. 

The Cuckoo-Spit Froghopper, Philaenus spumarius

However, in more northern parts of Europe, vegetation cover remains ever-green meaning movement is not needed and removing the visual selection for polymorphisms. Yet it does occurs in these areas too, most probably due to gene flow drift (4).

The Cuckoo-Spit Froghopper, Philaenus spumarius

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 132
2. Nast, 1972. Palaearctic Auchenorrhyncha (Homoptera), an annotated Checklist
3. Halkka and Halkka, 1990. Evolutionary Biology 24 pp 149-191
4. Drosopoulos et al., 2010. Zoosystematics and Evolution 86 pp. 125-128

Oysters Hitch a Ride

Common Saddle Oyster, Anomia ephippium

Unlike most other bivalves, the Common Saddle Oyster (Anomia ephippium) does not bury itself in the sand or mud of the sea bed. Instead they cement themselves to rocks or other hard substrates by chalky byssus threads that grow through a hole in the lower shell (1). They are experts at early colonisation of a substrate, and are often the among the first organisms to do so at a new location (2), something which is evident from the pictures included here, showing colonisation of an abandoned water drum by many A. ephippium individuals. So quick are they to colonise in fact, that smaller individuals can be seen growing on some of the larger ones. Unfortunately for them the drum had washed quite far up a beach and partially filled with sand, making a return to the water unlikely. Growing up to 6 cm across, younger, smaller individuals can appear almost translucent with older examples being white to pale brown in colour (1).

A water drum, washed up a a beach with Common Saddle Oyster, Anomia ephippium growing on the surface

 

References:

1. Challinor et al., 2003. A Beginner's Guide to Ireland's Seashore p. 123
2. Bramanti et al., 2003. Italian Journal of Zoology 70 pp. 175-178

Winter Feeding by the Goldfinch

Goldfinch, Carduelis carduelis

While some of the Irish population of Goldfinch (Carduelis carduelis) migrate in the winter, the majority are present all year round (1). The bulk of C. carduelis diet in the summer and autumn is comprised of seeds of various plants, various thistle species in particular (2). The unavailability of these in the spring and winter has resulted in C. carduelis being a common visitor to bird feeders in suburban gardens. However, as these are not the most reliable of food sources, C. carduelis relies on insects throughout the lean months to feed. At this time of the year it is common to see flocks of C. carduelis alighting on trees throughout the country to feed on insects present among the branches, as is evident in the picture below and above. Behaviour of the bird will change with the sizes of these flocks. Individual birds in larger flocks become less alert and consume up to 20% more food (3). However, travelling time to the nest feeding spot is also increased as is the likely hood of a larger flock attracting predators.

Goldfinch, Carduelis carduelis

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife
2. Glück, 1985. Ibis 127 pp. 421-429
3. Glück, 1987. Ethology 74 pp. 65-79

Lichen Photobionts

Photobionts in a lichen get a raw deal in the naming department. The algal or cyanobacterial partner in the relationship may do all the hard work of using light to make glucose but lichens are named after their fungal component This might seem an unfair outcome until one considers that there are c. 15, 000 fungal species described for lichens but only c. 100 photobiont species (1). So its not taxonomic snobbery, its a case of the fungal partner being the more distinguishing of the two. However, although they may not be distinguishing, I do feel that they are rather distinguished. Below are examples of genera of two of the more common photobionts isolated from their respective partners:- Trebouxia (an algae and termed a phycobiont) and Nostoc (a cyanobacteria and termed a cyanobiont). While many lichens have both phyco- and cyanobionts, one dominates and is termed the primary photobiont (2). 90% of lichens contain phycobionts, the remaining 10% having cyanobionts (1).

Trebouxia sp. (centre) isolated from Ramilia fraxinea

Nostoc sp. (chain of cells in centre) isolated from Collema cristatum

References:

1. Lücking et al., 2009. American Journal of Botany 96 pp. 1409-1418
2. Whelan, 2011. Lichens of Ireland pp. 4-5

Fighting Infection the Apine Way

Common Carder Bee, Bombus pascuorum

This is the time of the year for getting sick. That's not a statistic, its just personal experience. The cold and dark days mean we spend more time cooped up in close proximity to others: others who are sick. And so it spreads to us, whatever it may be, laying us low till our immune systems kick in and get us back on the road. Yet if being close to other, infected individuals is a risk of disease, it must be hell for bees. Take the Common Carder Bee, Bombus pascuorum. A eusocial bee, it nests on the ground in colonies of up to 200 individuals (1). Break out the cough syrup, bee sized spoons.
 

Common Carder Bee, Bombus pascuorum

However, B. pascuorum has a sophisticated defence system for dealing with infection. A tough, outer cuticle must first be breached by invaders (2). If they are successful in getting past this first line of defence, a complex interaction of innate humoral and cellular immune reactions are activated in both the bee's tissues and haemocoel (2). Probably the best characterised of these responses is the synthesis of antimicrobial peptides. B. pascuorum produces a defensin, an apidaecin, an abaecin and an N-terminally blocked molecule which provides the bee with antimicrobial activity against fungi, Gram-positive and Gram-negative bacteria (2).
 

Common Carder Bee, Bombus pascuorum

Such a sophisticated defence system does have its drawbacks. Parasitism of B. pascuorum by species of Conopid fly is common (3), but often the hosts show no obvious effect due to the action of the defensive system. Activation of this system is quite energy expensive and under limiting food conditions (which is increasingly becoming the norm for bee populations in Ireland and Europe as a whole(4)) leads to significant decrease in survival (5).

References:

1. Chinery, 2004. Collins Gem Insects p. 251
2. Rees et al., 1997. Insect Biochemistry and Molecular Biology 27 pp. 413-422
3. Moret et al., 2000. Science 290 p 1166-1167
4. Brown and Paxton, 2009.  Apidologie 40 pp. 410-416
5. Moore, 2002. Parasites and the Behaviour of Animals p. 209

An Unwelcome Antarctic Visitor

Despite our increasing knowledge of the risks of introducing alien species into the Irish environment, the numbers of records of priority invasive species, new to Ireland has increased steeply over the past ten years. 

Graph of Invasive Alien Species Number in Ireland from 1800 to 2010 (data source, see reference 1)

Over half of these priority invasives are plants, but there are increasing number of alien marine animals being recorded. Few of these have come as far as the Orange Tipped Sea Squirt, Corella eumyota, which is native to the cooler waters of the Southern Hemisphere. Here, it has a circumpolar distribution within the temperate and sub-polar regions (Chile, Antarctic Peninsula, South Africa, Australia and New Zealand) (2). It was first recorded off the coast of France in 2002, and has been since recorded in Spain in 2003 and England in 2004 (3, 4). C. eumyota was first recorded in Ireland in 2005 and 2006 (5), and while it is not yet considered as a potential invasive here, this may soon change.
 

Orange Tipped Sea Squirt, Corella eumyota

C. eumyota is a solitray ascidian that attaches itself flat to a substrate. Adults range in size from 2 – 4 cm, but larger individuals are common (2). Colouration is variable, but an orange tinge is often common, lending it its common name. Shape is variable, depending on the shape of the substrate, but given a flat substrate, a oval form is the most common. The main risk posed by C. eumyota is that of biofouling, clogging up pontoons, nets and cages in harbours (2). This also poses a risk to mussels and oyster farming, as C. eumyota has been found associated with these and other bivalves in Spain (2,5). Large aggregates on commercial mussel beds would reduce their productivity dramatically (2). C. eumyota also threatens native ascidians through competition, where clumps of them growing together can reduce water flow (2).

References:

1. http://apps.biodiversityireland.ie/InvasivesBrowser/
2. Nagar et al., 2010. Aquatic Invasions 5 pp. 169-173
3. Arenas et al., 2006. Journal of the Marine Biological Association of the United Kingdom 86 pp. 1329-1337
4. Varela et al., 2008. JMBA2 – Biodiversity Records 1: e59
5. Minchin, 2007. Aquatic Invasions 2 pp. 63-70

Alien Legacy of the Building Boom in Ireland

Winter Heliotrope, Petasites fragrans

This unseasonably warm winter has seen the blossoming of crocuses, daffodils and snowdrops in gardens throughout Ireland a lot earlier than usual. It makes a change from the previous two years, when this blog noted that daffodils had yet to bloom by March. One plant that will flower earlier than all of these regardless of the weather is the Winter heliotrope (Petasites fragrans). A native of the Mediterranian, it was seemingly introduced from Naples to gardens in France at the end of the 18^th century by Dominique Villars (1). Its flowers have a sweet, vanilla perfume, emerging from January to March (2) and it soon became a favourite. Populations produce either male or female flowers, with some florets of the opposite sex intermixed in the flower spikes (sub-dioecious) (3). It was introduced to England in 1806 (where, as in Ireland, only male flowers are found), where it was favoured as an ornamental in gardens and made its way to Ireland by about 1835 (4). Soon becoming naturalised, P. fragrans is now established and common throughout Ireland, and has proved to be , according to botantist Tony O'Mahony, the “greastest, single, alien plant threat to wildlife habitats in Ireland” (5).

Winter Heliotrope, Petasites fragrans, entirely covering a riverside verge

Growth and spread is by underground rhizomes and colonisation of new ground is swift. The round leaves remain on the plant all year, creating a blanket coverage of habitats and giving it a competitive advantage over most native shrubs (4). It is especially quick to colonise newly disturbed ground, something the building boom of the 2000s in Ireland provided in abundance. Embankments of new roads, riverbanks and banks throughout the country are now dominated by P. fragrans. Yet while it has been identified as a real and present threat to Irish native plant species (6), so far no legislative action has been taken to tackle the problem (4).

References:

1. Hogg and Johnson, 1864. The Wildflowers of Great Britain
2. Phillips, 1977. Wildflowers of Britain p. 26 
3. Toman, 1983. Folia Geobotanica 18 pp. 433-437  
4. O'Mahony, 2009. Wildflowers of Cork City and County pp. 348-350
5.  Killick, 2002. New Atlas of the British and Irish Flora 
6. Dolan, 2004. The Effects of Human Transport on Ecosystems: Cars and Planes, Boats and Trains pp. 15-62

Kicking it: Leg Defence

Lesser Magpie moth, Anania hortulata. Note the tibial spurs on both mid-and hind- legs.

While most moths in Ireland employ excellent camouflage to avoid predation, the Lesser Magpie seems to flaunt itself. Its head and thorax are boldly coloured black and yellow, as is the abdomen, black with yellow bands (1). The wings are no less demure; snowy white, outlined black they proudly display a delightful series of brown markings. The Lesser Magpie should well be so bold as it posses a nasty surprise for any potential predators. Elongated tibial spurs on both the midleg and hindleg, being especially pronounced on the latter.

Lesser Magpie moth, Anania hortulata

The binomial name of the Lesser Magpie has recently been in flux, with many synonyms being used in the past (the most common being Eurrhyparra hortulata). However in 2005 the genera Algedonia, Ebulea, Eurrhypara, Opsibotys, and Perinephela from the pyraustine family were synonymised with Anania and the species is now known as Anania hortulata (2). A widepread moth in Ireland, it flies from June to August, the individual pictured being spotted at the end of June last year.

References:

1. Atay and Can, 2007. Journal of Entomology 4 pp. 479-483
2. Tränkner et al., 2009. Nota Lepidopterologica 32 pp. 63-80

Colonisation of Europe by the Collared Dove

The Collared Dove, Streptopelia decaocto

The story of the colonisation of Europe by the Collared Dove (Streptopelia decaocto) is a truly remarable one. The bird was restricted to South Asia in prehistoric times, from where it spread to north China and the Middle East, partly with human help. It had spread to Syria and Turkey by the 16th century and had reached the borders of Europe by 1900 (1). Colonisation of Europe initially progressed along three routes; along the Adriatic into nothern Italy, northeastwards into Hungry and northweastwards through Central Europe (2). The first two of these routes were aborted, with colonisation into Central Europe continuting northwestardly until it reached the North Sea. Colonisation continued sideways and continues to do so today (3). It has been calculated that the expansion velocity of this colonisation is 43.7 km per year (1). A now common sight in many Irish gardens where it will often come to food, S. decaocto was unknown in this country until 1958 (4).

Expansion of the Collared Dove (Streptopelia decaocto) in Europe from 1900 to 1970 (after Hengeveld, 1988)

S. decaocto have a very long reproductive period, lasting from May til October. Female sexual maturity sets in after four months, so individuals born at the start of the reproductive season can breed by the end of it (1). While this goes some way to explain the speed of colonisation, it also begs the question why did it take until the 20th century to happen? A variety of reasons have been put forward, none of which are currently fully accepted. Change in nesting habits from using building to using trees may have opened new niches for the bird to exploit, fueling expansion (5). However it has been shown that S. decaocto nests in trees in other areas of its distribution, somewhat pouring cold water over this hypothesis. Climate change at the start of the 20th century resulting in milder winters and greater rainfall in the European continent may have given the bird the impetus to cross the barrier that the northern Balkans posed, opening the door to European colonisation (5). Changes in agricultural practices in Europe in the 20th century has also been suggested as a reason for expansion (5). This supplied S. decaocto with far more overwintering sites where food isn't a limiting factor. While all these hypothesies are valid, it is quite likely that a combination of these and other, as yet unforeseen factors facilitated the spread of S. decaocto.

References:

1. Hengeveld and van der Bosch, 1991. Ardea 79 pp. 67-72
2. Hengeveld, 1988. Journal of Biogeography 15 pp. 819-828.
3. Hengeveld, 1989. Dynamics of Biological Invasions pp. 92-115
4. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 70
5. Rocha-Camarero and de Trucios, 2002. Bird Study 491 pp. 11-16

Anthocerotophyta, the Hornworts

Of the three extant divisions of bryophytes, the hornworts (Anthocerotophyta) are thought to be the closest relative to vascular plants. Like the other two bryphyte divisions (the mosses and liverworts), the gametophyte is the dominant generation in hornworts. However, the protonema formed from the germinated spore resemble those of ferns and the locations of the anteridia (in groups in a chamber) and the archegonia (embedded inthe thallus) resemble those of the clubmosses (1).

Phaeoceros laevis

Hornworts consist of a gametophyte thallus and a sporophyte thallus. The thallus differs from many other bryophytes in having only one chloroplast per cell, not possessing oil bodies and possessing a pyrenoid (1). This is a body that serves as a nucleus for starch storage. The thallus often has a bluish tinge to it due to the presence of the cyanobacteria Nostoc embedded within the tissues which serves to fix atmospheric nitrogen which can be transferred to the sporophyte (2). This can in turn transfer fixed carbon to the thallus. Its is from the large, elongated sporophyte that hornworts get their common name. Its size is due to the fact that it will continue to grow throughout its life. Growth is from a near basal meristem, unlike most other plants which grow from the top, a feature that is unique to hornworts.

Phaeoceros laevis

Only three species of hornwort occur in Ireland (3) a number that is not all that surprising when one considers that there are only c. 300 species present worldwide (4). These are the Field Hornwort (Anthoceros agrestis), the Dotted Hornwort (Anthoceros punctatus) and the Smooth Hornwort (Phaeoceros laevis).

References:

1. Glime, 2007.  Bryophyte Ecology.  Volume 1.  pp. 57-62  (online at http://www.bryoecol.mtu.edu/)
2. Villarreal and Renzaglia, 2006. American Journal of Botany 93 pp. 693-705
3. http://www.botanicgardens.ie/herb/census/lists.htm
4. Taylor et al., 2009. Paleobotany (Second Edition) pp. 161-177

The 4,500 Year Old Lichen

Lichens aren't the fastest of growers. Then again, they don't need to be, more often than not being the primary colonisers of many substrates where they are unlikely to face much competition such as bare rock and tree bark. Exposed rocky substrates will not tend to accumulate organic or mineral material needed for plant growth so lichens that can withstand the exposure by staying as close to the surface as possible such as crustose species will face very little competition and often uninterrupted growth. Since lichens tend to radial growth they can be used as an indicator or substrate age in areas where they form the dominant vegetation cover. Lichen growth rates vary from one region to another and may decline after initial colonisation to an almost constant value (1). The us of lichens to determine substrate age is known as lichenometry and and has a useful range of up to about 500 years. Some species may be used for up to 4,500 years or more under dry continental conditions.

Map Lichen, Rhizocarpon geographicum

One of these species, and the most commonly used in lichenometry, is the Map Lichen (Rhizocarpon geographicum). Some examples of R. geographicum have been dated to be c. 4,500 years old (2). Its common name is well earned, as cracks in the yellow-green thallus show the underlying black prothallus, giving the lichen a map like appearance (3). A slow growing species, it can be found on hard siliceous on exposed uplands and mountains (4). It also can be seen on rocky seashores, as the example illustrated was, growing on red sandstone.

References:

1. Haeberli et al., 2003. Permafrost (Eds. Phillips, Springman & Arenson) pp. 343-347
2. Beschel, 1958. Arctic 11 p. 254.
3. Phillips, 1980. Grasses,Ferns, Mosses and Lichens of Great Britain and Ireland and p. 165
4. Whelan, 2011. Lichens of Ireland p. 139

Snakelocks' Symbiosis

Snakelocks Anemone, Anemonia viridis

The Snakelocks Anemone (Anemonia viridis) is one of the more common anemone species to be found on the Irish shore line, and also one of the more conspicuous due to its inability, unlike some other anemone species, to withdraw its tentacles (1). These are the same colour as the animals body, which varies from a dull brown to a vibrant green, with purple tips. Brighter, greener coloured animals are found in shallower waters than the duller ones due to the presence in the endodermal layer of the anemone of the unicellular dinoflagellate, Symbiodinium sp., commonly known as zooxanthellae, that forms a symbiotic relationship with A. viridis (2). To provide its symbiont partner with CO₂ for photosynthesis, A. viridis absorbs inorganic carbon from seawater (3). Algal-animal associations such as this are common among cnidarians in the tropics, but less so at higher latitudes. Of the c. 80 species of anemones reported in Irish waters, only three, including A. viridis, form such relationships (4).

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 174
2. Richier et al., 2006. FEBS Journal 273 pp. 4186-4198
3. Furla and Allemand, 2000. Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology 126 Supplement 1 p. 53
4. Bythell et al., 1997. Proceedings of the Royal Society of London B: Biol Sciences 264 pp. 1277-1282

The Unexpected Threat of the Canada Goose

Canada Goose, Branta canadensis

Although native to North America, escaped captives from estates both in Ireland and England means that the Canada Goose (Branta canadensis) is now established in Counties Antrim, Armagh, Cork, Cavan, Derry, Fermanagh, Monaghan and Tyrone as a breeding bird (1). It is an attractive species, its white cheeks contrasting with its black neck, and can be seen this time of year feeding in flocks on grasslands (2). As an introduced alien, its impact has been seemingly low, with problems of aggressive nesting habits, fouling of parks by droppings and damage by large flocks to grasslands being reported (1). However such anecdotal evidence does not tell the whole story. To do this, a system must be used to compare the impact of not only different alien species but also species from different taxonomic groups (eg., birds vs. mammals). This is just what has been achieved by Nentwig et al.: a generic scoring system that they applied to alien mammal species in Europe (3). The system divides impact into subcategories of either environmental or economic. Scoring these gives a potential impact which is converted to an actual impact by taking into account the distribution of the species. Using this system to assess the impact of B. canadensis reveals that it has the highest economic and environmental impact of the 26 most common alien birds in Europe. While all of this indicates control of B. canadensis as a priority, its large distribution, especially in norther counties, means this would be a labour and resource intensive step.

References:

1. Browne et al., 1999. Irish Birds 6 pp. 233-236.
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 38
3. Nentwig et al., 2009. Conservation Biology 24 pp. 302-311
4. Kumschick and Nentwig, 2010. Biological Conservation 143 pp. 2757-2762

A Seal in the River Lee

Grey Seal (Halichoerus grypus) at Union Quay, Cork City

The River Lee extends some 65 km from the Shehy Mountains to the sea at Cork Harbour (1). It starts becoming estuarine at Cork city: indeed the city was once a series of marshy islands surrounded by brackish water, a fact remembered in the names of parts of the city (The Marsh, Morrisson's Island, etc.) and the name of Cork itself, from the Irish “corcach” meaning bog (1). This estuarine habitat often brings large sea mammals right into the centre of the city, much to bemusement and delight of its residents. While Killer Whales (Orcinus orca) and dolphin species have been recorded in the past (2), the most common large mammals to be seen in the city area of the Lee are seals, both Grey (Halichoerus grypus) and Common (Phoca vitulina). The accompanying picture was taken on Christmas eve, at about 9.30 in the morning of a Grey Seal basking in the river around the Union Quay area of the city. Grey Seals are distinguished from Common Seals by their larger, almost dog-like, snout (4). Males are darker in colour than females and may also be noticeably larger (up to 0.5 m). Indeed, some males can grow quite large, reaching 3 m in length.

References:

1. Crowley et al. (Eds.), 2005. Atlas of Cork City pp. 7-16
2. Ryan and Wilson, 2003. The Irish Naturalists' Journal 27 pp. 187-191
3. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 28