Tag Archives: Bureau of Animal Population

Was the Chitty Hypothesis of Population Regulation a ‘Big Idea’ in Ecology and was it successful?

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Jeremy Fox in his ‘Dynamic Ecology’ Blog has raised the eternal question of what have been the big ideas in ecology and were they successful, and this has stimulated me to write about the Chitty Hypothesis and its history since 1952. I will write this from my personal observations which can be faulty, and I will not bother to put in many references since this is a blog and not a formal paper.

In 1952 when Dennis Chitty at Oxford finished his thesis on vole cycles in Wales, he was considered a relatively young heretic because he did not see any evidence in favour of the two dominant paradigms of population dynamics – that populations rose and fell because of food shortage or predation. David Lack vetoed the publication of his Ph.D. paper because he did not agree with Chitty’s findings (Lack believed that food supplies explained all population changes). His 1952 thesis paper was published only because of the intervention of Peter Medawar. Chitty could see no evidence of these two factors in his vole populations and he began to suspect that social factors were involved in population cycles. He tested Jack Christian’s ideas that social stress was a possible cause, since it was well known that some rodents were territorial and highly aggressive, but stress as measured by adrenal gland size did not fit the population trends very well. He then began to suspect that there might be genetic changes in fluctuating vole populations, and that population processes that occurred in voles and lemmings may occur in a wide variety of species, not just in the relatively small group of rodent species, which everyone could ignore as a special case of no generality. This culminated in his 1960 paper in the Canadian Journal of Zoology. This paper stimulated many field ecologists to begin experiments on population regulation in small mammals.

Chitty’s early work contained a ‘big idea’ that population dynamics and population genetics might have something to contribute to each other, and that one could not assume that every individual had equal properties. These ideas of course were not just his, and Bill Wellington had many of the same ideas in studying tent caterpillar population fluctuations. When Chitty suggested these ideas during the late 1950s he was told by several eminent geneticists who must remain nameless that his ideas were impossible, and that ecologists should stay out of genetics because the speed of natural selection was so slow that nothing could be achieved in ecological time. Clearly thinking has now changed on this general idea.

So if one could recognize these early beginnings as a ‘big idea’ it might be stated simply as ‘study individual behaviour, physiology, and genetics to understand population changes’, and it was instrumental in adding another page to the many discussions of population changes that had previously mostly included only predators, food supplies, and potentially disease. All this happened before the rise of behavioural ecology in the 1970s.

I leave others to judge the longer term effects of Chitty’s early suggestions. At present the evidence is largely against any rapid genetic changes in fluctuating populations of mammals and birds, and maternal effects now seem a strong candidate for non-genetic inheritance of traits that affect fitness in a variety of vertebrate species. And in a turn of fate, stress seems to be a strong candidate for at least some maternal effects, and we are back to the early ideas of Jack Christian and Hans Selye of the 1940s, but with greatly improved techniques of measurement of stress in field populations.

Dennis Chitty was a stickler for field experiments in ecology, a trend now long established, and he made many predictions from his ideas, often rejected later but always leading to more insights of what might be happening in field populations. He was a champion of discussing mechanisms of population change, and found little use for the dominant paradigm of the density dependent regulation of populations. Was he successful? I think so, from my biased viewpoint. I note he had less recognition in his lifetime than he deserved because he offended the powers that be. For example, he was never elected to the Royal Society, a victim of the insularity and politics of British science. But that is another story.

Chitty, D. (1952) Mortality among voles (Microtus agrestis) at Lake Vyrnwy, Montgomeryshire in 1936-9. Philosophical Transactions of the Royal Society of London, 236, 505-552.

Chitty, D. (1960) Population processes in the vole and their relevance to general theory. Canadian Journal of Zoology, 38, 99-113.

Some Reflections on Evo-Eco

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Some ecologists study evolutionary processes and we call them evolutionary ecologists. They have their own journals and are a thriving field of science. Other ecologists study populations, communities, and ecosystems in ecological time and do not in general concern themselves with evolutionary changes.The question is should they? Evo-Eco is a search for evolutionary changes that have a decisive impact on observable ecological changes like that of a collapsing bird population.

There are two schools of thought. The first is that evo-eco is very important and the changes that ecologists are trying to understand are partly caused by ecological mechanisms like predation and competition but are also associated with genetic changes that affect survival and reproduction. Consequently an ecologist studying the declining bird population should study both genetics and ecology. The second school of thought is that evo-eco is rarely of any importance in causing ecological changes, so that we can more or less ignore genetics if we wish to understand why this bird population is disappearing.

A practical problem immediately rears its head. To be safe we should all follow evo-eco in case genetics is involved in dynamics. But given the number of problems that ecologists face, the number of scientists available to analyse them, and the research dollars available it is rare to have the time, energy or money to take the comprehensive route. Conservation ecologists are perhaps the most tightly squeezed of all ecologists because they have no time to spare. Environmental managers request answers about what to do, and the immediate causes of conservation problems are (as everyone knows) habitat loss, introduced pests and diseases, and pollution.

The consequence of all this is that the two schools of thought drift apart. I cannot foresee any easy way to solve this issue. Progress in evolutionary ecology is often very slow and knowing the past rarely gives us much insight into predicting the human-affected future. Progress in conventional ecology is faster but our understanding is based on short-term studies of unknown generality for future events. Both schools of thought race along with mathematical models that may or may not tell us anything about the real world, but are conceptually elegant and in a pinch might be called progress if we had time to test them adequately.

The most useful evo-eco approach has been to look at human-caused selection via fishing for large sized fish or hunting for Dall sheep with the largest horns. The overuse of antibiotics for human sickness and as prophylactics for our farm animals is another classic case in which to understand the ecological dynamics we need to know the evolutionary changes that we humans have caused. These are clear cases in which genetic insights can teach us very much.

I end with a story from my past. In the 1950s, nearly 70 years ago now, Dennis Chitty working at Oxford on population fluctuations in small grassland rodents considered that he could reject most of the conventional explanations for animal population changes, and he suggested that individuals might change in quality with population density. This change he thought might involve genetic selection for traits that were favourable only in high density populations that reappeared every 3-4 years. So in some strange sense he was one of the earliest evo-eco ecologists. The result was that he was nearly laughed out of Oxford by the geneticists in control. The great evolutionary geneticist E.B. Ford told Chitty he was completely mad to think that short term selection was possible on a scale to impact population dynamics. Genetic changes took dozens to hundreds of years at the best of time. There were of course in the 1950s only the most primitive of genetic methods available for mammals that all look the same in their coat colour, and the idea that changes in animal behaviour involving territoriality might cause genetic shifts on a short-term period gradually lost favour. Few now think that Chitty was right in being evo-eco, but in some sense he was ahead of his time in thinking that natural selection might operate quickly in field populations. Given the many physiological and behavioural changes that can occur phenotypically in mammals, most subsequent work on grassland rodents has become buried in mechanisms that do not change because of genetic selection.

When we try to sort out whether to be concerned about evo-eco, we must strike a compromise between what the exact question is that we are trying to investigate, and how we can best construct a decision tree that can operate in real time with results that are useful for the research question. Not every ecological problem can be solved by sequencing the study organism.

Chitty, D. 1960. Population processes in the vole and their relevance to general theory. Canadian Journal of Zoology 38:99-113.

On Charles Elton

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Charles Elton was the Father of Animal Ecology and many young ecologists do not learn very much about him. He founded the Bureau of Animal Population at Oxford in 1932, and much of the history of his research group is captured in Peter Crowcroft’s book “Elton’s Ecologists” (1991). I was fortunate to spend the winter of 1960-61 at the Bureau while I was completing my Ph.D. at UBC with Dennis Chitty. It was Dennis’ last year at the Bureau, having gone there in 1935 when he had just finished his undergraduate work at the University of Toronto.

The Bureau of Animal Population or BAP, as all connected with it came to call it, had been born in January 1932 and by 1934 Oxford University had guaranteed funds for its core costs for five years with 3-4 scientific staff and a very few assistants. Survival as a unit depended on working on numerous applied projects, and the species receiving attention included Canadian snowshoe hares, Canadian lynx, muskrat, beaver, lemmings, European rabbits, squirrels, voles and the wood mouse. The Bureau was the home of the newly created Journal of Animal Ecology, of which Charles Elton was the first editor.

Charles Elton was a proper English gentleman, a gentle soul who had a coterie of first class ecologists in the BAP. The BAP was very nearly the world centre for ecology from the 1930s to the 1960s when ecology began its great growth around the world, so everyone who was interested in population ecology considered it equivalent to Mecca for science. Every day there was tea in the BAP in 1960, when we all took time to interact with the other postdocs and graduate students in the BAP, a total group of perhaps 15-20. Once a week Mr. Elton (as he never did a Ph.D.) would preside over tea around a table in the BAP Library and give out any news of the week to the staff and students. On most days he wore a tie and a sport coat in the best English tradition, and signed his letters as “Elton”. In 1960 he was compiling a species list for Wytham Woods, a 390 ha forest reserve belonging to the University. He felt strongly that one had to know all the species in a community before you could understand how it operated. So one could see him day after day pinning insects in trays. He was always very serious, and the only joke I ever heard him tell was about how he could never understand Americans. He had gone to the New World after the War, perhaps 1947 or 1948 and was visiting a famous American scientist. They had to get up at 0700 in the morning and rush to work without a proper English breakfast, and so at 0800 they arrived in the professor’s office, and then Elton said he was told ‘now you can relax’. It was not the proper English way to start the day and he could never understand the rush-rush style of the New World.

Charles Elton founded the Journal of Animal Ecology in 1931, now one of our leading journals. In the early days he did much of the reviewing and accepting of papers for the Journal. He had an amusing tale of the classic papers of A.J. Nicholson (1933) on the balance of animal populations. He received this very long paper and he could not find anyone who would agree to review it so he did it himself. He confessed to us one day at tea that he found he could not understand anything in the paper, so he decided it must be very brilliant so he published it immediately. Alas those days are gone.

There were of course no electronic machines even in 1960 and Elton did all his writing by pen and paper. He had just finished the now famous book “The Ecology of Invasions” and his secretary who typed all his work pointed out to me that he never changed a word from what he first wrote. No need for revisions and revisions. He was of course like a god to all of us young ecologists, and so we were very fortunate that this was the year in which he was teaching his Animal Ecology course to Oxford undergraduates. All of us graduate students and postdocs went along, as it was only a series of 14 lectures in the best Oxford tradition. The classroom was full in the first lecture, which was one of the worst lectures I have ever attended. We were rather stunned that such a great man could lecture so hopelessly, mumbling in a monotone, showing slides but almost never referring to them, every mistake in the book. We realized then that greatness could occur in many dimensions and his skill was as a writer. Classroom attendance fell like an exponential and by the fifth lecture no one was left in the classroom but we of the BAP.

Elton organized the BAP as a small research unit and did not believe that any research unit should exceed more than a handful of scientists who interacted all the time over a small subset of problems. In the early days much of the research was on cyclic populations of rodents and fur bearers in Europe and North America, but it moved to insects and broader problems after the War.

Oxford was a strange place to a North American in 1960. Too many of the professors were at odds with one another, jostling for fame we all presumed. It was impossible not to have many enemies within and outside the walls of Oxford, and we as students never quite knew why some were praised and others reviled. Perhaps ideas were confounded with personalities, and no one thought that you could respect a scientist but disagree with his or her view of science. But much was at stake then, and when you were King of Oxford you were king of the hill. Now 50 years later we have many kings of science all around the world, and I hope that Oxford has changed.

 

Crowcroft, P. 1991. Elton’s Ecologists: A History of the Bureau of Animal Population. University of Chicago Press, Chicago. 177 pp.

Elton, C. S. 1958. The Ecology of Invasions by Animals and Plants. Methuen, London. 181 pp.

Nicholson, A. J. 1933. The balance of animal populations. Journal of Animal Ecology 2:132-178.