BUTTERFLIES

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BUTTERFLIES JOHN DAVIS Re-establishments, introductions and other releases of butterflies seem to involve much debate and strongly held opinions for and against.

Perhaps a reason for the matter being so contentious is the strong commitment felt on both sides of the arguments, involving both objectivity and emotion: Some feel affronted with what they see as interference with nature and the butterflies, or dismayed that such ‘quick fixes’ are held to be viable solutions to the huge problems of habitat loss. Their opposites cannot believe that anyone could think that giving butterflies such a ‘helping hand’ is a matter for reproach, and dispute claims of adverse impacts.

Being such an emotive and important issue, Butterfly Conservation published its ‘Policy, Code of Practice and Guidelines for Action’ on Lepidoptera Restoration in 1995. It drew on experience and views of BC members and advisors, the IUCN and JCCBI codes and guidance produced by EN and JNCC. However that endeavour by BC to establish objectivity and agreed standards of practice was not welcomed by all, especially those very keen on releasing or translocating butterflies. The Code and its Guidelines seem to be poorly understood, viewed as restrictive and so often ignored or little used. In an attempt to improve understanding of its basis and purpose, a BC working party has recently produced explanatory notes to those policies.

The conclusion from a thorough review (Oates & Warren, 1990) of reestablishment attempts is that many failed in the long term and did not represent a good use of resources. BC tries to acknowledge differing views and aspirations held within the Society, but does not want to encourage or be drawn into attempts that do not comprise sound, informed practice, or acknowledged priorities for action. Accordingly those keen on reestablishments/releases sometimes perceive the cautious ‘official’ BC line as negative.

There are often sound reasons for not attempting the proposals BC is asked to consider, including the greater priority of other important conservation measures; such as maintaining other key species still in the area before trying to bring back long-gone species. In addition, the basis of many proposals seem to start with a ‘vacant’ site and an assumption that removing individuals from struggling populations of threatened species elsewhere in the country, is in the ‘best interests’ of the species. Few proposals put to BC arise out of objective strategies prepared with the aim of improving the well-being of extant populations in the localities they occur.

BC’s Regional Action Plans have objectively assessed the conservation priorities for butterflies and moths in each region of England, as well as Scotland Wales and Northern Ireland. It is hoped they will inform decisions on the priorities for conservation action.

In being without a strategic basis many proposals simply appear to have the motive of ‘species list embellishment’, of adding a high profile species to the site or county ‘list’. However, there is also the more creditable motive of

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wishing to validate site management undertaken or to make use of seemingly vacant and suitable habitat. Building an expectation that site management measures, or surviving habitat, only have merit if something ‘special’ is put there, denigrates benefits already going to other plants and animals. The message should instead be on the need to appreciate and conserve overall ‘biodiversity’.

Undue haste in wanting to get on with ‘exciting’ releases can mean attempts involve poor planning and insufficiently resourced monitoring or site management measures. Captive populations can be built up before receptor sites are in appropriate condition or even identified. Having ‘stock’ ready to release can also mean receptor sites being chosen without adequate checking that they are actually without the species. All guidelines on re-introduction procedure advocate years of careful checking to verify extinction on receptor sites.

The ‘re-distribution’ or ‘rescue’ of individuals from a struggling, isolated population, so as to “not have all eggs in one basket” might be attempted as a last ditch measure in certain circumstances. Particularly if insurmountable problems have been encountered in trying to secure habitat quality and extent to enable natural persistence or viability of the population. But a species should be in dire circumstances, the last resource of a particular race or other important biodiversity element for such an un-predictable approach to be considered an option. At such a stage, captive breeding to prevent extinction might also be used, such approaches being demonstrated under English Nature’s Species Recovery Programme. Recognising such an eventuality as a possible action should not mean planning for it and perhaps avoiding the (often more difficult) task of in situ conservation measures. Habitat extent and quality are recognised to be key factors in enabling colony survival and simply creating another struggling or doomed colony elsewhere helps nothing.

Re-introduction proposals put to BC create a significant work-load; they can arise from within the Society, the general public, other conservation bodies and at times statutory conservation agency staff. There seems to be a simplistic general public view that the conservation of butterflies entails breeding and releasing. Most enquiries concern popular or desirable species such as the now uncommon fritillaries or White Admiral and Purple Emperor.

But any species ‘absent’ from a site or county is a likely candidate.

Moths We seldom, if ever, receive enquiries with proposals for the (re-)introduction of moths. Even though (as with butterflies) rearing unknown caterpillars, or eggs from trapped moths so as to observe their development and enable identification, can be common practice. At times this can lead to captive breeding and subsequent multiple progeny, but where described under moth recording accounts it is often noted that progeny are returned to site of origin.

Official ‘conservation’ captive breeding and re-establishment projects for moths are those of the EN Species Recovery Programme for highly threatened UK species. They involve species now down to their last few sites in the Britain such as the Reddish Buff and Barberry Carpet and represent attempts to prevent the complete loss of the species as elements of UK biodiversity.

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Adverse impacts Recording distributions: A key impact of releases is the distortion of recording, and surveillance, and thus our understanding of natural distribution patterns and trends. That complaint is often countered with the view that so much has been lost that naturalness is no longer an issue. Our landscape and its habitats may well be heavily altered and at best semi-natural, but the ways in which species manage to survive and occupy what is available is very much down to their ‘natural’ abilities. Appeals by county recorders for details of suspected releases when uncommon or supposedly extinct species are found in the area don’t always get civil responses, but fortunately more responsible individuals undertaking releases do make their actions know.

Diseases and other effects: Attempts at the re-enforcement of existing populations often gives concern for the possible introduction of diseases, bacterial or viral. Advocates of using captive bred insects assure that ‘clean stock’ free from evident disease and parasites can only be a benefit to ailing wild populations. I think that assumption is questionable, given our growing realisation of the important role of exposure to viruses, bacteria, predation and parasitism as natural selection pressures for producing ‘fitness’ in animal populations in the wild. Swamping wild populations with individuals that are somehow ‘unfit’ or contributing ‘deleterious’ characteristics to the genepool, is a standard biological control technique. Pests and diseases evolve at very fast rates and their host populations need to ‘keep up’ in fitness.

Genetics and other natural factors: Increasing the genetic diversity of a wild population is also often advanced as a reason for “re-enforcement”. The notion is based on the deleterious effects of dwindling gene-pool diversity: concerns about inbreeding and increasing genetic homogeneity affecting survival in small isolated populations are wellfounded and subject to research.

But all is not simple and clear-cut in genetics and we should not forget that natural populations will have been subject to such pressures when colonising new areas or even going through the process of speciation or sub-speciation.

Research on population dynamics and ever-improving genetic analysis techniques are revealing a complex picture. Some degrees of inbreeding might be ‘tolerable’ or even adaptive. In that respect environmental, habitat and population genepool factors will all be important determinants, and of course the animals’ own choice of mates. In view of such complexity and factors unknown to us, how can we know what needs to be ‘selected’ for through captive breeding or artificial population mixing? The BC Code recommends avoiding use of stock lineages captive-bred for more than two years.

Other possibly significant natural factors should also be considered: such as the Wolbachia endocytoplasmic bacteria in insects. These intracellular symbionts are ubiquitous in arthropods and are known have a range of astounding and fundamental effects on their hosts. These include causing parthenogensis and disrupting reproduction and sex-ratios through increasing

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male mortality or sex changes. They can also cause outright cytoplasmic incompatibility, by which different, healthy ‘strains’ of the same species cannot produce offspring. The importance of that mechanism as a powerful biological control tool has of course been recognised and is being keenly researched. The relevance of this natural biotic factor to the conservation of butterflies and moths is as yet unknown but could have great significance, as it may already have for natural populations. At the very least it should mean applying great precaution to arbitrary mixing of un-related populations in pursuit of a simple notion of creating ‘hybrid vigour’.

Wildlife as a commodity: There is a genuine worry that unthinkingly promoting re-establishments as a beneficial or successful conservation measure helps undermine the protection and safeguard of habitats and sites threatened by destruction such as development. Translocating vegetation and its inhabitants away from a site is all too often presented as a simple ‘rescue’ solution allowing site destruction.

Such an approach has now been shown to fall very short of its claimed successes in many ways. In recent years BC has been using the evidence of the many failed attempts at re-establishing Marsh Fritillaries, to oppose the loss of sites to development. ‘Can’t we just move them?’ is the standard enquiry from the developers.

Setting the courses of action: historical perspectives: BC’s published Species Action Plans (SAPs) for priority conservation species often mention considering the use of strategic re-introductions.

But whilst the SAPs are meant to be a ‘map’ of the pathways for conservation action, there seems to be a tendency to treat them as just a ‘menu’ from which to pick the ‘re-introduction’ course of action ahead of higher priorities. This is rather like trying to fix the symptoms instead of tackling the causes.

Restoring the species to historical ranges such as the 1950s is often a long term objective in the SAPs. However, that aspiration should be tempered with the appreciation that the landscape and its habitats then, were a product of WWII activities and the agricultural abandonment of the depression, all without the effects of modern chemical farming. Realistically it will be impossible to ‘re-create’ that past landscape from our current starting point. Individual sites might be ‘recreatable’ but we realise that butterflies and other wildlife actually need a landscape with more than the odd habitat refuge. Guided by the past we should be looking to provide what they need in a re-newed landscape Proposed re-establishments should not be simply driven by historical precedent, such as having a past record on a site in the 1950s. Many sites perhaps only held certain species at that time because of larger better habitat nearby, or because of the overall amount of habitat in the locality.

The Large Blue and other formal projects: Strong expectations in and out of our Society mean frequent requests for advice, encouragement or assistance with plans to re-populate vacant sites or

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even undertake introductions. These can understandably be driven by the high profile publicity for projects like the pioneering re-introduction of the Large Blue, a globally threatened species. That research based work will result in benefits for conservation elsewhere and is not simply a template for action for all Lepidoptera conservation efforts.

What the project so strongly demonstrates is the enormous amount of effort and time needed to re-establish locally extinct species with exacting habitat requirements, and the continuing effort that is needed to maintain those results. But, all to often, only the headlines are remembered and thus a simple validation of the breeding and releasing approach.

Some might query the justification for the great effort of the restorationecology approach of the Large Blue project, and cite certain long persisting (re-) introductions to validate the simple ‘have-a-go release’ approach. But, in contrast, attempts over almost a century to re-establish the Large Copper as a resident species have so far failed. The threatened European status of these two species explains the resources being committed to the work on them.

Findings of the research here in Britain may help secure these insects’ future elsewhere in Europe.

Overview of past attempts: There is much confusion and conflicting expectations over the use of reestablishments as a conservation tool for threatened butterflies. But being able to draw the line between what is, and what is not, necessary and warranted is proving very challenging.

Breeding and releasing and translocations have historically been the activities of keen Lepidopterists. With such a long history we have a generally good perspective of successes and failures, though records of actions and subsequent monitoring are far from comprehensive. So-called ‘clandestine’ or simply un-recorded attempts continue to take place.

An overview in 1990 (Oates & Warren, WWF) presented one of the first objective assessments and found a high proportion of early failures and many with simply no known outcome. Records of early attempts can be more inaccessible (e.g. buried in personal diaries), but that alone probably does not explain the observed increase in attempts in the latter part of 20th Century.

Reasons for success or persistence of the butterflies on the receptor site were not found to be due to method of establishment in terms of numbers (as little as 3 mated females had ‘worked’). Instead it seemed to be due to habitat suitability (quality and extent) and its persistence through appropriate management. That said, failure in short or even medium term was usually the outcome. The report concluded re-establishments could be a useful conservation tool but remedying habitat problems affecting the species was the priority.

More thorough survey and monitoring of the UK’s butterfly populations in recent decades and analysis of their changes has greatly improved our understanding of the dynamics of their populations.

Over the last century just over half of our 60 resident species have undergone declines in range and population strength, some very severe, e.g.

Woodland Fritillaries, Chequered Skipper.

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The remainder have been generally stable in range (but more thinly populated therein) or have actually increased in range. In the last few decades, due to climate warming and presumably also habitat factors, several species have shown significant range expansions (e.g. Comma, Speckled Wood, White Admiral, Essex Skipper).

Some new colonisations of the UK by moths and dragonflies (possibly also the Queen of Spain Fritillary here in Suffolk) all attest to the climate effect.

Even amongst the species that have undergone declines there have been some partial recoveries in recent years, most directly in response to management restoring the extent and quality of habitat available to them, but presumably climate was also a factor: e.g. Silver Spotted Skipper on the North Downs.

Meta-populations and mobility: What can explain the current confusing picture in which Silver Studded Blue populations introduced into areas of habitat in North Wales, in which they were previously unknown, persist since the 1940s, whilst so many attempts with Marsh Fritillary into sites previously occupied, and seemingly providing suitable habitat, have failed.

The findings in the Oates and Warren (1990) report outline the influence of habitat related factors such as isolation and fragmentation.

The understanding of butterfly population ecology and dynamics in relation to those habitat factors, as well as the genetic ones, continues to advance and elucidate the effects of habitat fragmentation.

The established view is of butterflies having sedentary, colonial or open populations. Many species currently in difficulty are seen as ‘sedentary’ or ‘colonial’ and our view of them is of discrete colonies in small areas of habitat in which the occupants don’t move very far.

Recently developed theories on ‘meta-populations’ or ‘populations of populations’ are helping to explain how such ‘colonial’ insects occupy discontinuous or fragmented habitat; often become extinct on some patches, and re-colonise them.

Much important research, such as on Glanville Fritillary in Finland, is producing field results demonstrating how closely natural populations function like the theoretical models.

For meta-population butterflies (and other insects), those that leave their ‘patch’ could be as important as those that stay to breed. Future survival of the whole population in that locality might depend on the emigrants finding somewhere from which their progeny can return or spread elsewhere.

Butterflies might leave habitat patches for various reasons such as not finding suitable mates, egg-laying sites, or as the result of population pressure; such as the harassment of mated females trying to egg-lay. It is thought that some individuals might be more prone to dispersal than others; a characteristic that emerges periodically in the population. Having no suitable habitat to get to means a loss of those emigrants and, though probably only a small ‘drain’ on the population in most cases, arguably it is a loss of important elements of the gene-pool: - those with higher mobility characteristics. Our understanding of the colonising abilities of ‘sedentary’ butterflies are changing with current research findings, e.g. mark/release recapture work on Pearl-bordered Fritillary and monitoring colonisation of restored habitats.

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Research by Chris Thomas’ team at Leeds University on the Silver studded Blue (SSB) and Silver spotted Skipper has been producing very interesting results.

In the Dulas Valley in Wales (introduced SSB populations) problems of low genetic diversity through founder ‘bottlenecks’ were seen to be over-come if populations can become big enough - which needs enough accessible habitat. The effects of ‘bottlenecking’ were found to be temporary and affect the rarest alleles: which of course could be a problem if they include important adaptive ones. They found that suitable habitat patches within 1 km of colonies were readily colonised, and yet the SSBs in those colonies are usually said to travel no more than 50 m.

Butterflies, like most insects, have a great capacity for rapid population growth when suitable habitat is available, but maintaining occupation of patchy and temporal habitat requires some population ‘connectivity’. Thus, struggling isolated populations may need an increase in accessible habitat as a conservation measure, rather than attempts at translocations to where the habitat network is already degraded or un-viable.

Other recent papers from Chris Thomas’s team confirm that habitat fragmentation can have evolutionary consequences on flight morphology. The availability of habitat for colonists can select for an ‘emigration’ or stronger flight tendency in the meta-population, as revealed by differences in relative sizes of thorax and abdomen.

This affirms a vital way in which we should ‘help them help themselves’, provide them with what will develop their colonising ability.

Reversing the habitat causes of butterfly declines will not happen overnight. These species disappeared over decades from parts of our countryside. Do not be lured by the illusion of the ‘quick fix’; recovery at a similar rate to their loss should perhaps be the reasonable expectation. It might take 25 years for a butterfly to re-colonise a site in an area 50 miles away from it’s starting point. The negative view that it took so long to reach the ‘end point’ would fail to recognise the great result of all the sites colonised on the way.

Conclusions The conservation of butterflies should be seen as a facet of biodiversity conservation and simply moving around 0.1% of the fauna of a habitat will not necessarily overcome fundamental and widespread problems. It is not going to solve much, except perhaps provide a partial reprieve for very threatened species and satisfy certain human expectations.

All our counties, parishes and sites are empty of species they used to hold.

But if we busy ourselves with trying to artificially re-populate them with ‘favourite’ species, ignoring those struggling to survive, trying to reverse the underlying habitat problems, we will simply lose more biodiversity.

There is no shortage of opportunities for attempting to re-populate vacant sites so do not simply take opportunity as the starting point. Take a strategic look at what the remaining species might need.

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There will be instances in which re-distribution of threatened populations is warranted in an attempt to avoid losing a biodiversity resource. But instead of planning to do it we should be planning to avoid never having to do it.

Artificial re-establishments are likely to have a role in conserving and restoring biodiversity but I believe appropriate usage is far more limited that many people imagine.

Get on with the habitat ‘gardening’ on a big scale and leave the rest to God and nature.

References and excerpts used for ‘over-heads’ Brookes, M. I. et al. (1997). Genetic analysis of founder bottlenecks in the rare British butterfly Plebejus argus. Conservation Biology 11.

Lepidoptera Restoration Butterfly Conservation’s Policy, Code of Practice and Guidelines for Action. 1995.

Oates, M. & Warren, M. (1990). A review of butterfly introductions in Great Britain and Ireland. World Wide Fund for Nature.

Scott L. O’ Neill et al. (eds.) (1997). Influential Passengers, inherited microorganisms and arthropod reproduction. Oxford University Press.

Thomas, C. D., Hill, J. K., Lewis, O. T. (1998). Evolutionary consequences of habitat fragmentation in a localised butterfly. Journal of Animal Ecology.

Thomas, C. D., Hill, J. K., Lewis, O. T. (1999). Flight morphology in fragmented populations of a rare British butterfly, Hesperia comma.

Biological Conservation 87.

Thomas, C. D., Singer, M. C. & Boughton, D. A. (1998). Catastrophic extinction of population sources in a butterfly meta-population. The American Naturalist 148.

Thomas, C. D., Thomas, J. D., & Warren, M. (1992). Distributions of occupied and vacant butterfly habitats in fragmented landscapes.

Oecologia 92.

John Davis Conservation Officer Butterfly Conservation UK Conservation PO Box 444 Wareham Dorset BH20 5YA

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