Sporocysts of Leuchocloridium paradoxum

John M.C. Hutchinson’s Homepage

I now work in the Malacology Department in the Senckenberg Museum für Naturkunde Görlitz.

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Tel.: (+49) (3581) 47605410
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Privat, Dr J.M.C. Hutchinson, Senckenberg Museum für Naturkunde Görlitz, Am Museum 1, 02826 Görlitz, GERMANY

ORCID number = 0000-0003-3166-3045
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Table of contents

Some past and current research projects

(i) Overview

My research career has three main strands: (1) a long-term interest in diverse facets of snail and slug biology; (2) experience in numerical modelling which I have applied mostly to various optimality models of behaviour, life-history strategies, and morphology; (3) field experience in ornithology. My first degree was in Zoology at Oxford; I did my doctorate on snail shells with John Currey at York; for the next 10 years I was at Bristol, working mostly in behavioural ecology, particularly with John McNamara, Innes Cuthill, and Alasdair Houston.

From September 2000 to December 2006, I held a research-scientist position at Gerd Gigerenzer's Center for Adaptive Behavior and Cognition in the Max Planck Institute for Human Development, Berlin. I tried to make connections between biological research and the focus of the group, which was adaptive decision making in humans using simple heuristics. A paper in Behavioural Processes (Hutchinson & Gigerenzer, 2005) provides a review of the group’s work from a biologist’s (my) perspective.

Since 2007 I have mostly been collaborating with my wife Heike Reise, studying terrestrial slugs, particularly aspects of their reproduction and life history, although we have got sidetracked into issues of taxonomy and systematics. We share a position in the Department of Malacology at the Senckenberg Museum of Natural History Görlitz). Much of our time is now taken up with editing the journal Archiv für Molluskenkunde together with our colleagues in Dresden and Frankfurt, Katrin Schniebs and Julia Sigwart, and our technical editor, Robert Forsyth. We are also involved in a small way in teaching and supervision of students on the masters course "Organismic and Molecular Biodiversity".

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(ii) My former life: mostly behavioural ecology

The starvation/predation trade-off; spreading the risk—with A.I. Houston & J.M. McNamara

Houston et al. (1993) is a general theoretical discussion of when to perform behaviours differing in their consequences for starvation and predation; how optimal routines are altered by stochasticity in the food supply, size-dependent predation, the presence of a refuge, the chance of interruption, etc. The study is relevant equally to how flock size, for instance, should vary through the day, and to when migration or metamorphosis should occur in a life-history. We used both analytic results and solutions obtained by dynamic programming to add to (and sometimes to correct) a disparate collection of earlier work and to put it into a unified conceptual framework. Back to Contents

When should an arthropod moult?—with J.M. McNamara, A.I. Houston & F. Vollrath

If feeding rates depend on size, and growth depends on feeding rate, when is it best to moult to a larger size? Our models (Hutchinson et al., 1997) tend to predict consistent increases and decreases in growth ratio and instar duration (rather than the constant growth ratios of Dyar’s Rule). However when the number of instars was also optimised Dyar’s Rule became a good approximation. We were concerned to show how to test our model, developing and applying a statistical technique for cases where individuals can be followed through successive moults, surveying data in the literature for trends in the population-mean growth ratios, and showing how to predict the consequences of environmental manipulations. Back to Contents

When to sing: optimality models using stochastic dynamic programming—with I.C. Cuthill & J.M. McNamara

Earlier simple models of energy budgets in a stochastic environment could generate the familiar dawn and dusk chorus of bird song (see left-hand figure below). Our innovation in Hutchinson et al., (1993) was to allow males to differ in quality and then to seek female choice rules that best distinguished quality. The best rules involve remembering past song output, or requiring a continuous bout of song (as do animals relying on phonotaxis). Male singing routines accordingly adjust to emphasise and prolong the dawn chorus. The model provides an excellent numerical example of the Handicap Principle in sexual selection.

In his doctoral research Robert Thomas confirmed some predictions of these models experimentally, which inspired us to write a successful NERC grant proposal to refine the methods of testing. Previous tests of SDP models have simply compared predicted and observed routines of a whole population, whereas a much more powerful approach is to study individuals and to test the relationships of behaviour with state (weight) and of behaviour at one time interval with behaviour at a preceding time interval. Also earlier empiricists have mistakenly used short-term manipulations to test published predictions about the consequence of long-term manipulations in which the animal has a chance to adapt to the new environment. Hutchinson & McNamara (2000) is a general paper explaining how to test SDP models; it is aimed at empiricists and uses bird singing routines as a running example.

Another paper (Hutchinson, 2002) concerns the fine structure of the dawn chorus when foraging is gradually affected by changing low light levels during twilight. This also causes a dawn chorus, but also a characteristic pause as light levels plateau (see right-hand figure below). SDP enables two different explanations for the dawn chorus to be incorporated in the same model and their importance compared.

[Theoretical dawn chorus routine] Click for enlargement and caption
[Theoretical dawn chorus routine] Click for enlargement and caption
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Brood survival in plovers—with T. Székely and G. Noszály

Our paper (Noszály et al., 1995) compared brood survival in two habitats. My part was the statistical analysis using maximum-likelihood estimation techniques. Back to Contents

[Photo of blue hole science]

Surface ecology of blue holes—The Andros Project

This was an international scientific expedition researching into the biology, geology and hydrology of these unusual submerged caves of the Bahamas. I spent 5 weeks in the field surveying the biota in the surface waters and immediate vicinity of the cave entrances. The major determinant of diversity was salinity, which was generally too high to grant this region of the caves much special conservation value. My paper (1998) relates our data to the work of hydrologists and geologists on the same expedition. Back to Contents

Site fidelity in West African wintering migrant birds—with J.M.B. King

I have been responsible for the statistics in a paper (2001) that tests whether birds are recaptured at the same site rather than adjacent ones more often than expected according to a null model. It is based on five winters of fieldwork by amateur ringers in the Gambia. Back to Contents

Rules of mate choice in patches—with Konrad Halupka

Males are often distributed patchily, but existing models of mate choice ignore this. Hutchinson & Halupka (2004) develops a series of theoretical models in which females can inspect the quality of each male in turn, but delaying acceptance has a cost. Some versions allow return to males inspected earlier, and in some versions mean male quality varies systematically between patches or seasons and must be estimated from the quality of males already inspected. We derived the optimal female policy, in terms of what quality of male should be acceptable at each stage of search. We also compared the performance of simple rules of thumb, both those suggested in the literature and others derived by simplifying the optimal policy. Download pdf of poster. Back to Contents

Is too much choice aversive?

Classically the provision of choice has been regarded as a motivating influence, and this has driven explanations of why it pays males to form leks, why restaurants cluster together, and why cafeteria diets make rats obese. But recent results in psychology by Iyengar & Lepper establish that humans can find too much choice aversive and are then less likely to pick any item on offer. Hutchinson (2005) reviews evidence for similar phenomena in nature, concentrating on leks, food choice and environmental enrichment. There are three logically distinct issues: do animals prefer choice, do they consume more when offered a choice, and do they choose better options when more choice is available? Back to Contents

Spatial location and the choice of toilet—with Michael Bender

Users of public toilets often endeavour to use a cubicle or urinal that is not next to another occupied one. Do they show apparent foresight by avoiding cubicles next to those likely to be taken by users arriving later? We tested this with observations from two toilets, one men’s and one women’s. We argue that this is a good example of the sort of spatial game that humans play all the time without much conscious thought (which does not imply that the strategies are not adaptive).
[Figure of toilet experiment] Click for enlargement and caption
[Graph of toilet experiment data] Click for enlargement and caption
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Is risk taking used as a cue in mate choice?—with Andreas Wilke, Peter Todd & Dan Kruger

It is often supposed that women are attracted to men who take risks, which might explain the elevated risk-taking and mortality in young men. We (Wilke et al. 2006) tested this by asking both men and women whether they would find it attractive if someone of the opposite sex took each of 40 different risks described in short text vignettes. Both sexes agreed that only social and, to a lesser extent, recreational risk taking was attractive; in ethical, health and gambling domains it was unattractive. Surprisingly, the less risky a behaviour was rated, the more attractive it was judged.

We also assessed risk attitudes within stable couples, because we thought that those who, say, found climbing very risky might have been attracted by, and paired with, those who had no such concerns about heights. Instead we found positive assortment. Perhaps those with similar risk attitudes join the same clubs and/or are more compatible once they have paired. Back to Contents

Making predictions from random walks—with Peter Waser

Waser used analytic formulae to predict how far a group of mangabeys should travel in a month or year if they followed a random walk. Others have reapplied this technique to other mammals. Hutchinson (2000) considers the effect of relaxing assumptions in the random-walk model, and uses Monte-Carlo simulation to derive confidence intervals.

Waser also predicted the number of encounters between mangabey groups under the null assumptions of no attraction or avoidance, using the formula used by physicists to predict collisions between molecules in a gas. Hutchinson & Waser (2007) review the use of this formula in diverse fields of biology, for instance to predict encounters between predators and prey, sperm and eggs, and observers and the birds that they are censusing. We consider how sensitive the predictions are to the assumptions, partly by comparing with simulations of random walks, and we correct various misuses of the model in the literature. Back to Contents

Game theory in car parking—with Peter Todd and Carola Fanselow

What simple rules enable you to select a parking space close to your destination? Our computer simulations of simple decision rules demonstrate that the rules used by drivers affect how parked cars are distributed and thus which rules work best. By analysing the statistical structure of the environment created by good rules, we were able to explain which rules outcompeted others in an evolutionary algorithm. Published as a chapter in a book on Ecological Rationality.
This was linked to a study with Peter Todd and Konstantinos Katsikopoulos using a driving simulator to study parking decisions in this context, but I suspect that that will never see the light of day!
[Figure of model car-parking environment]

Skylark song flights and dynamic games—with I.C. Cuthill & J.M. McNamara

The main question under investigation was to what extent how much one skylark displays affects how much its neighbours display. One can imagine that two birds of equal quality escalate their advertisement more than if they were asymmetric in ability. Catching and colour-ringing two populations proved to be a considerable challenge which delayed progress and restricted the intended experimental manipulations (temporary attachment of weights). I also tried to develop two novel methodologies: (1) an array of 5 microphones feed into a laptop computer to give a real-time readout in the field of the singers’ position and sound intensity; (2) analysis of the song suggests that breathing rate increases when the bird is ascending at the start of its song flight.

To my shame, I don't think the main project will ever get written up! However, in Hutchinson & Griffith (2008) we reported a quite high rate of extra-paternity and a greater rate of cuckoldry in smaller fathers. Long periods high above the ground in a song flight may make males vulnerable to cuckoldry. I have also analysed data on seasonal changes in claw and beak length. Back to Contents

Optimal trajectories and optimal spacing: crickets and frogs, predators and prey

If several male crickets are singing but any of them may suddenly disappear (mated, predated, etc.), I have shown that it is optimal for the females to follow a curved trajectory, bet-hedging by initially heading between two rivals. For the same reason, pairs of males close together may be a more desirable target than one in isolation. Is this a good enough reason for males to aggregate?
[Figure of taxi scenario] Click for enlargement and caption
[Figure of predictions] Click for enlargement and caption
This work is published (Hutchinson, 1999), but I have failed to finish off a follow-up paper in which it is uncertainty in quality that causes similar effects. Back to Contents

[Experimental screen of patch leaving experiment] Click for enlargement and caption

Patch leaving behaviour in humans—with Andreas Wilke, Peter Todd and Uwe Czienskowski

A classic paradigm in behavioural ecology is when to switch from a deteriorating food patch to a fresh one. We examined this decision in humans using a computer game in which subjects earn money by clicking on fish that briefly surface in a pond. Some ponds initially have more fish than others, which can be judged from the rate at which fish appear, but caught fish are not replaced. Optimal behaviour should depend only on the number of fish caught at a pond and the time spent there, with the function depending on the distribution of fish across ponds and travel time; we proposed that humans, being extreme generalists, should alter their switching rules according to whether this distribution was aggregated or even. We found little indication for this. The main influences on when to leave were time since the last capture, the preceding interval between captures and time spent in the patch.

In everyday modern life humans often have to make decisions when to switch from one task to another. As an example we have asked subjects to make words from a sequence of letters, and studied whether the patch-leaving rules from behavioural ecology explain when they ask for a new sequence. Again time since the last capture and the preceding interval are important determinants of when to switch, but also involved are immediate indications of sequence quality, perhaps gauged from the commonness of the constituent letters. Contrary to optimality predictions, switching rules did not seem to depend on the variation in sequence quality. Back to Contents

Better bet-hedging by using past weather to predict states of relatives: when in spring to germinate—with John McNamara

When environmental fluctuations affect all population members, genotypes with the highest long-term reproductive success may bet-hedge, with identical individuals acting differently. Furthermore, it can be advantageous for an individual to base its decisions on the proportion of its relatives in each possible state. Normally direct monitoring of this proportion is not feasible. However, it might estimate proportions indirectly from the history of weather which all have experienced. For illustration we model a seed deciding when during spring to germinate; early germination can lead to more offspring, but at increased risk of a lethal frost. If a frost kills the early germinating members of the genotype, we predict others should be, counterintuitively, more likely to germinate immediately. We examine how the optimal dependence on past weather is affected by perenniality, autocorrelation in weather conditions, and temperature-dependent growth rates. Calculating the optimal strategy in the general case is a formidable computational problem.

In an earlier paper (Hutchinson, 1996), I reviewed some recent developments of the theory of bet-hedging in fluctuating environments. Back to Contents

(iii) Slugs and snails

[Sections of snail shells] Click for enlargement and caption

Design in the shell shape of a terrestrial snail, Trichia hispida—D. Phil., supervisor Prof. J.D. Currey

It is a beauty of the gastropod shell that it can be sectioned to reveal each developmental step in its construction. Previous models have been based on the isometric logarithmic spiral. My models instead followed from the mechanical constraints and cues which are likely to influence the animal’s choice of where to secrete the next length of tube (e.g. Hutchinson, 1989). Calculation of the geometric consequences of these rules enabled me to test these models against patterns of variation in the dimensions of sectioned shells. A conference abstract available here provides a useful summary. For my criticism of an alternative approach see Hutchinson (1990a).

Other aspects of the research included: (1) biomechanics—measuring strength of shells to relate it to their size, thickness, shape and colour; (2) quantitative genetics—a statistical reanalysis of W.F.R. Weldon’s classic 1901 demonstration of stabilising selection on shell shape (Hutchinson, 1990b). Back to Contents

Theoretical models of functional morphology

Hutchinson (2000) widens the application of this work on snail shell shape to birds’ eggs and root branching patterns. The paper was concerned to illustrate how models that simplify a three-dimensional structure to two-dimensions can be conceptually flawed, and I investigated to what extent this led to quantitative inaccuracies. Back to Contents

Selection of shell morphs of a terrestrial snail in feeding trials with captive shrews

My original aim was to test whether snail shells with their periostracal hairs shaved off were more prone to predation. They were not but did appear to be recognised as distinct. Further statistical analysis of the data on choice and handling time quantified the effects of shell size, shape and colour. Back to Contents

Faunistic work on terrestrial slugs and snails—with Heike Reise

Most of the slugs and snails found in synanthropic habitats in North America are from Europe. Because there are relatively few workers on slugs and snails there, we have succeeded in finding several new species there that have not previously been recognised. Our publications of these finds include reviews of each species’ biology and ecology: Boettgerilla pallens (an update reviews further North American records), Aegopinella nitidula and Tandonia budapestensis. The latter species has considerable scope for becoming a pest, as does Derocereas invadens, whose range we have considerably extended into the Eastern USA. Regions where we have searched for synanthropic species include the Pacific Northwest, the Denver region of Colorado and the Salt Lake City region of Utah.
[Photo of Boettgerilla pallens] B. pallens: click to enlarge + caption [Photo of Deroceras invadens] D. invadens: click to enlarge + caption
[Photo of Tandonia budapestensis] T. budapestensis: click to enlarge + caption
[Photos of Aegopinella nitidula] A. nitidula: click to enlarge
In Europe, we have extended the range of the slug Deroceras turcicum, initially to the Czech Republic and Slovakia, and later to Poland. Our paper (Reise & Hutchinson, 2001) also discusses its considerable range of morphological variation so as to facilitate identification. By chance, we were the first to collect the introduced carnivorous slug Selenochlamys ysbryda, from a churchyard in Wales, although we were too slow-witted to appreciate it at the time! A finding of Milax nigricans in northern France prompted us to review other occurrences outside its natural range and to highlight which identification characters are most reliable. A couple of papers examine the synanthropic slug fauna in our own town of Görlitz and over the adjacent border in Polish Silesia. Another discovery was that of Monacha claustralis, found on a field meeting of the Deutsche Malakozoologische Gesellschaft near Jena; this was the first report from Germany, but to be expected given its spread in Poland and the Czech Republic. A collaboration with Turkish colleagues led to a publication on the spread of Arion ater s.l. to Istanbul.More recently we have been collaborating with Ágnes Turóci and Barna Páll-Gergely about the slug fauna of Hungary. Back to Contents

Mating behaviour of Deroceras slugs—with Heike Reise

Following Reise's (2007) review of mating in this genus, she and I are examining the mating behaviour of further species. Partly this is to try to understand the function of various parts of the genital anatomy, on which the taxonomy of this genus is largely based. One such approach is to examine mating behaviour in species in which the genitalia are extreme, and an example is our paper on D. gorgonium from Crete, which has a very large penial gland. More recently we have examined mating behaviour in D. helicoidale from Turkey which has a long spiral penis.
Another reason for examining mating behaviour is to provide extra characters for taxonomy. For example, by studying the mating behaviour of Deroceras collected in the Sächsische Schweiz, we have recognised that D. rodnae needs to be split into at least two species with very different courtship and copulation behaviours (link to paper and videos). Another example is our discovery that the mating behaviour of the widespread pest species formerly known as D. panormitanum does not correspond to that of the species originally described under this name, prompting us to redescribe the pest species as Deroceras invadens (link to videos). Most recently it was the distinctive mating behaviour of Deroceras cecconii that made us realise that this long-ignored species really was valid; it turns out to be rather common and widespread in Italy. Observations of its mating behaviour was valuable also in establishing homologies between the functionally important parts of its penis and those of related species.
Our observations of mating behaviour have been much facilitated by the development of a digital video system based on security systems.
[Mating slugs] Copulation of Deroceras cecconii. The finger-like penial glands are starting to evert over the partner to deposit a secretion:
the sperm masses have already been exchanged reciprocally (one is the off-white blob attached below trunk of gland).
CLICK HERE to see video from which this still came.

The worldwide spread of the slug Deroceras invadens—with Heike Reise, Bettina Schlitt, Tereza Kořinková, David Robinson and Gary Barker

In a thorough review (Hutchinson et al. 2014) we established which countries this species has colonised, when it was first recorded in each, and in which habitats and climates it occurs. Although we trawled the literature carefully, our own collections and those of various museums considerably extended the range, particularly in the Americas. Conversely, some museum specimens and published records turned out to be misidentifications. Subsequently work in our own backyard documented a second colonisation of Poland. Most recently, by sequencing part of the mitochondrial COI gene, we have further investigated the likely origin of this species, its routes of spread, and its genetic diversity (Hutchinson et al. 2020). The much greater diversity of COI, anatomy and mating behaviour in southern Italy and Sicily implies that this is its native range; this is also the only region where there is a correlation between genetic and geographic distances apart. Another important result is that, although D. invadens has colonised both North America and Australia long ago, import controls mean that some very common haplotypes in Europe are absent or very rare in these continents. Our collecting trips in Italy have, as a by-product, established the range of related species such as D. panormitanum.
[Distribution map of Deroceras invadens] Slightly updated from Fig. 4 of Hutchinson et al. 2014
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Allometry of genitalia size in Arion slugs—with Heike Reise

Arion slugs are hermaphrodites with a long courtship finishing with reciprocal exchange of freshly manufactured spermatophores via everted genitalia. Is size of the distal genitalia (parts involved in spermatophore manufacture, exchange and digestion, and sometimes stroking the partner) sexually selected: i.e. do large individuals invest in relatively large genitalia to increase mating success? Alternatively, genitalia much larger than the partner’s could cause incompatibility. For five species collected throughout the year from one site, we weighed each slug, then dissected out the reproductive tract (see project on Arion life cycles). Relative weights of its proximal parts indicated maturity. As slugs mature the distal genitalia grow disproportionately fast, but within adults they scale with slight negative allometry (cf. isometry of the digestive gland and slight positive allometry of the whole reproductive tract). Interspecifically the relationship is isometric. The two almost obligate selfing species have relatively smaller genitalia than similarly sized congeners.

We have since measured allometry of various components of the reproductive system of the terrestrial snail Helix pomatia and the freshwater basommatophorans Stagnicola corvus and Stagnicola turricula. This was in collaboration with Bartek Gołdyn and Tereza Kořínková. Back to Contents

A sinistral slug—with Heike Reise & Mandy Benke

Reise et al. (2001) described a sinistral specimen of Arion lusitanicus; this is only the 5th sinistral individual reported for any slug species. Our attempts to mate our specimen with dextral conspecifics indicated that it was incapable of proceeding far with courtship. We discussed the possible genetic basis of sinistrality in slugs, given the absence of sinistral siblings of three of the sinistral specimens reported.

Species boundaries in Deroceras slugs—with Heike Reise and Stefanie Visser

Deroceras is the most speciose genus of terrestrial slugs; most species are externally indistiguishable but distinctive in their genitalia and mating behaviour. We have been mapping zones of contact between D. praecox and D. rodnae in the mountains of southern Poland and between D. praecox and D. fatrense in the Mala Fatra mountains of Slovakia. The species overlap very little. At one site a narrow mountain stream marks the border, but the genital morphology suggests some hybrids just where bridges cross.

In the Elbsandsteingebirge south of Dresden D. rodnae co-occurs with D. juranum, but they have a very narrow parapatric distribution, seeming not to correspond with any landscape features. These two species are closely related but never hybridise. Back to Contents

Mating of Ariunculus isselii—with Heike Reise

On holiday in Sardinia, we came across several populations of the endemic Ariunculus isselii, a slug that externally one might suppose was a species of Arion. It has indeed often been placed within Arion, but we had a big surprise when we dissected slugs killed during or after mating: unlike Arion, A. isselii does not use a spermatophore to transfer sperm. Our paper reviews the taxonomy of the genus, describes the mating behaviour of A. isselii , redescribes its genital anatomy, and attempts to interpret how the genitalia are used. Back to Contents

Life cycles of five syntopic species of Arion slugs—with Heike Reise & Grita Skuijenė

In Britain, several species of Arion slug may coexist at the same site. These species differ considerably in size, but do different timings of their life cycles also help them to coexist? Between 1998 and 2016, whenever I passed Leigh Delamere M4 Services I tried to sample the adjacent patch of woodland, collecting every individual seen of the five Arion species present. All individuals were preserved, then weighed. A sample were dissected and components of the reproductive tract weighed; the ratios of weights indicate maturity. This estimate was calibrated by rearing eggs to adulthood in captivity or keeping wild-collected individuals until they mated or laid eggs. All species were predominantly annual, with the possibility in some of a minority delaying reproduction until 18 months. Species tended to become mature at different times of year, the ordering matching the ranking of adult size. However, at each time of year species overlapped considerably in body size (except that the two largest species predominated in summer, when the other species were mostly hidden underground). Individuals maturing later were smaller (although individuals of A. intermedius were highly synchronised in when they became adult). Consequently adult size varies considerably within, as well as between, species (the ratios between maximum and minimum adult masses of each species are 5.9–9.5, and between quartiles1.5–2.8; median adult mass varied between the smallest and largest species by a factor of 54). In our paper we have compared this with intraspecific variation in adult size in other pulmonates.
[Diagram of size distributions] Within each lattice square, lengths of the five coloured bars each represent number of individuals of one Arion species of that size range in that month (Fig. 5 of Hutchinson et al. 2017)
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I welcome reprint requests, but you can download most papers from here.
For citations, see my profile in Google Scholar.
Note: for many of these publications I give a brief account of subsequent work on the topic in an “update” section.

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Chew Valley Ringing Station, 2007 [Photo, ringing at Chew]
At my field site, 2016. What was I photographing?
[picture] Feeling bullish with a talk (and auroch) behind me:
Malacological Society meeting, University Museum of Zoology Cambridge, 2007 (© Bill Bailey)

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