«On the distribution, ecology and management of non-native reptiles and amphibians in the London Area. Part 1. Distribution and predator/prey impacts ...»
The London Naturalist, No. 90, 2011 83
On the distribution, ecology and management
of non-native reptiles and amphibians in the
Part 1. Distribution and predator/prey
TOM E. S. LANGTON
Triton House, Bramfield, Halesworth, Suffolk IP19 9AE
LEHART, c/o 5 Roughdown Villas Road, Hemel Hempstead, Hertfordshire HP3 0AX
CLIVE HERBERT67a Ridgeway Avenue, East Barnet, Hertfordshire EN4 8TL Abstract
Past interest and research
History of recorded introductions
Development of London’s pet trade
Archaeological and taxonomic considerations
Climatic and zoogeographic considerations
Species accounts — reptiles
European lizards and snakes
Non-European lizards and snakes
Terrapins and freshwater turtles
Basic freshwater terrapin and turtle indentification in the London Area................ 109 Species accounts — amphibians
Other European amphibians
Exotic species imported accidentally
Non-native amphibian and reptile hotspots in and around the London Area............. 134 Problematic aspects of the chelonian pet trade
Ecological impacts and implications
Nature conservation concerns
Impacts of exotic herpetofauna in the wild
Trends in London’s wild terrapin numbers
Abstract This is a review of fifty-one non-native species, subspecies, intergrades or hybrids of amphibians and reptiles recorded as living wild in the London Area. Of these fifty-one taxa, referred to here as ‘types’, around twenty-one are amphibians of which fourteen have bred successfully and thirty are reptiles of which just two have been proven to breed. Other types may have bred unrecorded. A rapid increase in the number of types of terrapin in the wild has been observed since trade restrictions on red-eared terrapin importation in 1997. Many new species, mostly North American, but including those from Africa and Australia, can 84 The London Naturalist, No. 90, 2011 now be found in the wild. The traditional split of Water Frogs into two species and a hybrid has now diversified to include many more types that may interbreed when mixed. The distribution and spread of Water Frogs over the last two hundred years in this part of southeast England is described for the first time. Brief descriptions and identification notes are provided and zoogeographic and historical aspects of colonization are considered. Part 1 refers to distribution and aspects of impacts from the species’ role in the food chain of the communities where they have colonized. The trade in herpetofauna and nature conservation and welfare issues are considered. Aspects of disease impacts and philosophical considerations are described in Part 2.
Introduction There are at least fifty-one species, subspecies, intergrades or hybrids (referred to here as ‘types’) of amphibian and reptile recorded as living in the wild in the London Area. It includes those that are or have been self-maintaining through breeding for at least one generation (sixteen types). It also includes three types that are being recorded in the wild on a more frequent basis, that are tropical species often released in summer and are unlikely to survive a winter period. There are in addition to the fifty-one types, a larger number of species recorded once or twice that have escaped, often for a few days or weeks, to be recaught or to die outdoors, for which records have not been particularly sought as they are so numerous, although some examples are given. Of the fifty-one types, around twenty-one are amphibians, of which fourteen have bred successfully, and thirty are of reptiles of which just two have been proven to breed. At least four of the types (and possibly up to a further four suspected but not recorded) are native to the UK but have originated from mainland Europe.
The ‘London Area’ is the centre of abandonment of non-native herpetofauna in the United Kingdom. The London Area as described here includes the London Natural History Society recording area and a hinterland representing an edgearea outside of up to ten kilometres or so. In recent decades the number of such species seen has overtaken the twelve species that are considered unequivocally to be, native to the British Isles (not counting marine turtles) and the London Area in recent times (Langton 1991). We also refer to the smaller Greater London area that represents the more urban land, almost all of which falls inside the M25 motorway (Figure 1).
Of the fifty-one types of herpetofauna (shortened here to herp or herps), relatively few have become established or have spread to any degree, although some have been subject to removal activities. Removal has been either to prevent breeding and the potential of further spread and harm to other wild species (nature conservation), or potential damage to economic interest (e.g., fishery), or to reduce perceived harm to the animal in an unsuitable location for its well-being and survival (welfare).
Records have been received by the current recorder (TESL) from our Society’s members since the mid 1980s. Until that period the number of records of introduced species reported in The London Naturalist from time to time has been relatively few, generally increasing through the twentieth century after about 1935 and with the greater increase in importation of animals from Continental Europe as pets in the 1950s. In addition to a recent appeal to members for records we have included those made available by the London, Essex and Hertfordshire Amphibian and Reptile Trust (LEHART) and those of the County Amphibian and Reptile Groups (ARGs), many of which to some extent gather records as a part of their established function to carry out conservation work. Several ARGs were established and coordinated with help from the Fauna and Flora Preservation Society (now Fauna and Flora International) in the 1980s and steadily built up via the Herpetofauna Groups of Britain and Ireland (HGBI) in the 1990s and early 2000s by the UK herpetofauna conservation charity Froglife.
In addition, some of the county or area-based biological record centres were able to provide some records. A large volume of information was provided by Herpetofauna Consultants International (HCI Ltd) from its library and archives.
Langton et al. — Non-native herpetofauna in London. Part 1 85 FIGURE 1. Study area 80 80 km showing the outer edge of Greater London boroughs (solid regular line), the London Natural History Society recording boundary (Solid circle), the M25 motorway (dashed line), with many of the locations that are cited within the text.
The bold line running west to east is the River Thames.
Many published research papers, reports and university student studies were also consulted and searched for records. In total, around 1,200 records have been collated of which about 200 have been generated by our members and 620 by your LNHS recorder from various sources. Around eighty additional records have been provided by LEHART and 280 from six county record centres and from local ARG records. With the species accounts, the number of records inside and outside the LNHS area within the London Area are stated when the number of records exceed a total of around ten records.
With regard to taxonomic nomenclature, there has been substantial disruption to scientific naming in recent years which is unhelpful with respect to continuity of general reference for non-specialists, and with reference to published legal documents including international law. This is particularly the case when names change more than once over a short period, for example with alpine newt.
Although some names are widely accepted, we have kept with previously familiar scientific names but also given new names that have become more generally accepted in recent years or partially accepted by taxonomic convention.
86 The London Naturalist, No. 90, 2011 Past interest and research In the past, Fitter (1949, 1959, 1960) and Yalden (1965, 1967) in particular made initial efforts to document non-native amphibian and reptile reports for the LNHS area, before but mostly between 1940 and the 1970. The first local atlas of distribution that included non-native herpetofauna covering at least a part of the LNHS recording area was for Essex (Plant 1983) and there have been more recent contributions, for Kent (Philp 1998), for Surrey (Wycherley and Anstis
2001) and for Hertfordshire (Clark 2001). Trevor Weeks conducted a survey of feral terrapins for his National Terrapin Survey in the mid 1990s (Weeks 1995,
1997) and a final checklist in 1999, covering the whole of the UK. This showed just how extensive the abandonment of terrapins was becoming. The report identified over 200 UK sightings of which around fifty (twenty-five per cent) were from the London Area, making London the densest area for terrapin abandonment in the UK.
With Water Frogs, Surrey ARG members, and particularly Julia Wycherley, can be singled out for contributing significantly by collating reports by local recorders from the south-central and south-west of the study area in Surrey. In Middlesex and elsewhere Doug Napier has carried out extensive fieldwork to recheck sites for continued Water Frog occupancy. Apart from this there have been only a few volunteer and university student studies nationally. This is possibly a reflection of a perception, that existed until fairly recently, that the release of amphibians and reptiles could not potentially impact significantly on agriculture or human health to any great extent, or cause harm to native wildlife and so it has not been a priority area. Other workers have studied individual sites and those persons are listed in the acknowledgements. It is not exactly clear how comprehensive our coverage has been; however it is likely that most individuals or populations persisting for any duration would have been noticed over the years, at least post 1900. However, those species not breeding or present only for a few years (such as populations centred on a single pond) may have been overlooked.
History of recorded introductions The Changing Wild Life of Britain (Edlin 1952)appears to be the earliest review of non-native fauna in Britain and followed Malcolm Smith’s (1951) New Naturalist series volume The British Amphibians and Reptiles that included nonnatives. Previously, Cooke (1893) had summarized the stories, snippets and other evidence pertaining to Water Frogs from journals such as the Zoologist and other published texts. The first full attempt at documenting all introduced animal species in the British Isles was The Ark in our midst (Fitter 1959). This was extended by The Naturalised Animals of the British Isles (Lever 1977) that has been recently updated (Lever 2009) and with a world-wide review (Lever 2003). Frazer (1964) and the New Naturalist series subsequent updates have provided further information on non-natives but were not comprehensive reviews. In a European context, Langton and Burton (1997) listed over thirteen species of amphibians and reptiles introduced outside their range in Europe. The first extensive European herpetofauna distribution atlas was produced by the European Herpetological Society (Gasc et al. 1997) but in many countries national atlases now provide additional information. Other information collated for this study relates to the London Area (Figure 2) and south-east England in general. This
• Reports published within The London Naturalist over the last hundred years or so
• A range of articles published in Victorian/nineteenth-century journals
• County reports for Essex, Kent, Surrey, Buckinghamshire and Hertfordshire
• A monograph on Water Frog dispersal in Kent (Philp 1998) Langton et al. — Non-native herpetofauna in London. Part 1 87
• Student dissertations on aspects of Water Frogs, terrapins and palaeoarchaeology
• Reports on activities of biological supply companies at Newdigate and South Nutfield in Surrey
• Technical reports prepared by a range of national charities, voluntary bodies and individuals
• Papers published in British Wildlife magazine
• Government-funded research reports
• Publications in scientific journals.
Historically, it is thought that fish breeding and fish transport in Asia began around 5,000 years ago in China and that more recently the Romans and others imported wild and domesticated animals to England, to establish them for human food and/or for in rituals/entertainment. It is almost impossible to think that children did not carry small animals as pets on such journeys during Iron and Bronze Age travel too. Whether they survived, or were released or escaped in sufficient numbers to colonize is not known. What is known from archaeological investigation so far is that all of the generally accepted UK native herpetofauna FIGURE 2. One-kilometre distribution records for all non-native reptile and amphibian records in the London Area over the period 1830 to 2011.
88 The London Naturalist, No. 90, 2011 species in modern times are represented in the fossil/sub-fossil UK fauna after the last Ice Age, when they might be expected to have colonized naturally. They recolonized the land mass that is now Britain across areas that would then become eroded and flooded by sea level rise.