Ronald Henry Maxwell Savage’s book, The Ecology and Life History of the Common Frog (Rana temporaria temporaria) was published in London by Pitman (1961) and in the USA by Hafner, New York in 1962. An online version of the USA edition can be found here; this version is also offered for sale as a ‘print’ version of bound photocopied pages with the claim that the work is in the public domain. With Savage having died in 1985, i.e. 36 years ago, the work is still, as I understand the law, under copyright in the UK and also I suspect in the USA.
Dr. Savage has concentrated most of his research effort for more than 30 years on the ecology in the British Isles of this one species of frog. This book is in large part a compilation of the results of research reported in a series of papers that commenced in 1935. although new data are presented and old data are in some instances re-examined and reinterpreted. It is most worth while to have this published material and new information assembled in one narrative.
The author's concept of ecology cuts across a broad spectrum of scientific disciplines and he is ready to delve into any subject that may illuminate some phase of the life of his chosen animal. Thus, illustrating his approach. we find material on the biochemistry of the jelly of the frog's egg, experiments on the behavior of young tadpoles in relation to water deficient in oxygen, observations on the relationship of gut contents to growth rate in tadpoles (how much of what a tadpole consumes is really food?), statistical investigation of density of internal parasites as a measure of mortality (from causes other than parasites) in tadpoles, and an analysis of the relationship of direction of wind to the number of frogs migrating to the breeding ponds, to mention just a few of many topics lucidly presented.
The book is arranged in ten chapters, nine of which treat various aspects of the ecology and life-history of the frog, beginning with eggs and young tadpoles and going lull cycle to breeding behavior. The tenth chapter discusses statistical and other methods of study. An appendix treats in detail statistical aspects of problems dealt with in earlier chapters and a second appendix consists of a glossary.
The longest chapter of the book is devoted to investigation of the influence on the date of spawning of variables in the external environment. Voluminous data on spawn ing dates (collected by volunteer observers cooperating with the Royal Meteorological Society) were available to Savage, who examined the data statistically for possible correlations of weather with variation in spawning dates at different localities and in different years. The weather data used are those recorded at Government weather stations, but Savage is well aware that his animals do not live in weather instrument shelters. He points out that as long as there is reasonably good correlation between variation at the instrument site and in the animal's habitat he can make statistically valid use of the available data. Erroneous interpretations are not likely to result, and only low correlations of weather and behavior will be obscured. Nevertheless, when Savage can cite temperatures of spawn as different as 15° and 2I.5°C on the same day in the same area (but in different ponds) one cannot help but wish that data had been gathered somewhat closer to the microhabitat of the animals.
The analysis of single elements of weather in relation to spawning offered little enlightenment, for Savage observed in the field and confirmed over the calculator that neither rainfall nor temperature alone correlated closely with date of spawning. When he studied the effects of climatic variables acting together, however, he uncovered significant correlations. The data were analyzed by means of "Joint functional regression diagrams,” three-dimensional graphs in which isophenes representing spawning dates meander across a grid with two weather variables (chosen in various combinations from monthly mean temperature, monthly mean rainfall and percentages of possible sunshine) on the axes. These laboriously constructed diagrams illustrate well the complex inter actions of the various environmental influences and make it apparent why analysis of single factors gave meager results.
Another chapter deals with food, hibernation. and migration. Little space is devoted to food. Savage tabulates the stomach contents of 17 frogs and provides additional data from the literature to contrast the food of Bufo and Rana. The conclusion that differences in food habits between the species are related in part to habitat differences between frogs and toads—“they eat what happens to be there”—is certainly sound, although the suggestion that “Anura in general are not indiscriminate feeders" may raise some questions, depending upon how broadly one interprets “indiscriminate." There is certainly little evidence for taxonomic discrimination. For example, a recent paper by Inger and Marx (Exploration du Parc National de l’Upemba, fasc. 64, 1961) shows that a majority of the African species they studied had eaten representatives of three or four phyla. Referring to Bombina variegata in captivity, Savage states “They reject mealworms." citing this as an instance of animals being most ready to feed on prey they are most likely to find in their natural habitats. But the Bombina I have kept for several years, orientalis and bombina as well as variegata, would long ago have starved had they rejected mealworms.
Savage presents some information on hibernation sites, hut devotes the bulk of the chapter to a discussion of migration to the breeding ponds and the hypothesis that the characteristic odor given a pond by its algal flora is detected at a distance and guides the frogs to the proper pond. No effective challenge to this hypothesis has been made since it was first presented many years ago, and the evidence for similar phenomena in anadromous fish returning to the stream in which they hatched and for homing in newts adds credibility to the hypothesis.
This is a stimulating book and the reader will find himself comparing the behavior of Rana temporaria with that of the frogs he knows, mentally testing Savage's explanation against the actions of other species. Parallels between the European species and its North American relative Rana sylvatica are particularly striking. The paragraphs describing the relatively brief appearance of adult frogs at the breeding ponds very early in the year, the concentration of egg masses in a shallow, restricted part of the pond, the swarming of newly hatched tadpoles atop the disintegrating masses of jelly all could have been written about sylvatica. It is only when Savage tells us that temporaria avoids wooded areas that we note a marked difference from the habits of the wood frog.
A facet of the work disappointing to me is the slight use made of the marking-recapture technique of study. Savage makes his feelings plain: "I believe that the animals being studied should receive as little interference as possible, for as soon as one does anything to them, they are no longer ‘at home.' By all means use any laboratory methods to study the environment, but leave the animals themselves alone." One can deduce growth rates, movements and survivorship bv a variety of ingenious methods, but the concrete evidence provided by marked animals is often best. Savage did utilise paper tags for temporary marking of some animals, and some of the data most interesting to me were derived from these animals. One frog tagged in its hibernating pond was recaptured in a breeding pond and thus verified (as no other data could have) one source of the breeding population of this particular pond.
The records of 52 tagged frogs in one local population prevent a fascinating picture of the fluctuating composition of that population during the breeding season. On any night the tagged males outnumbered the tagged females, sometimes by as much as six to one, and among tagged individuals there were almost twice as many males as females. Males tended to remain at the bleeding pond for several days in succession, or return after disappearing for one or more days, whereas females in this instance were not in attendance for more than one night. Savage tells us that the number of the sexes are about equal, so the unbalanced sex ratio probably merely reflects the male habit of spending several nights in the pond. (Tenacity can have its rewards: male No. A18 mated with different females three nights in succession.)
Savage concentrated his study at the breeding ponds, and consequently offers very little concerning the life of the frogs during the period when they are neither breeding nor hibernating. A chapter only two pages in length covers the life of the juvenile frog. Estimates given of three to six breeding frogs per acre are based on the number of egg masses counted in the ponds, but we are not told how the author knew the extent of the area served by each pond. Surveys of a large number of ponds showed that no pond served as a breeding site every year. What happens to the frogs when a pond is deserted? An intensive marking program might provide an answer.
The author makes broad hut somewhat spotty use of the literature. Thus, as an example of geographic variation in embryonic temperature tolerance, he cites the work by Volpe on Bufo americanus but not the work of Moore on Rana pipiens. Again, he cites without critical comment a report that the eggs of a species of Rana have a thermal death point of 45°C. a figure far higher than reported for any anuran whose eggs have been adequately studied. A purely personal feeling, but one that I expect is shared by many readers, is a dislike for the abbreviated style of literature citation used (probably favored by publishers because of saving in type setting) and for grouping of citations at the close of each chapter. I much prefer to see titles cited in full and to have the references in one place.
A brief review cannot do justice to the years of effort and enlightened inquiry that went into the research, nor can it touch on more than a few of the subjects explored in the book. Anyone interested in the ecology of amphibians will profit from reading it; I recommend it highly.
The following was written for Journal of Animal Ecology by Thomas Townley MACAN (1910-1985) while at the Freshwater Biological Association:
It is a commonplace idea that a distribution map should not be studied unless something is known about the distribution of the collectors from whose data it is compiled. More novel perhaps is the suggestion that a general ecological work should not be studied without some knowledge of the author. Dr Savage writes in the foreword that he has been working on frogs for 30
years, his degrees and where he took them are set out on the page before, and that is all the information there is about him. What sort of job has he held during the 30 years? What facilities in the way of collaborators and apparatus did it provide? How much time was he able to devote to frogs? What influenced him to follow certain lines in preference to others? These are some of the questions that readers may ask. As this is a pioneer work of its kind, and ecologists may learn from what Dr Savage did not achieve as well as from what he did, answers would have been useful.
The author has been chiefly concerned with the factors that affect the date and place of oviposition and the behaviour before and during the process, but in the course of the 30 years he has investigated many other aspects of the biology of the common frog. These observations, together with those, often few and unimportant, of other workers are the subject of the first eight chapters. How much remains to be found out is striking; that is not a disparagement of Dr Savage's achievement but a demonstration of the length of time that work of this kind takes. The distribution of the species is established, but no explanation of the limiting factors is yet available. It is known what tadpoles eat, but not from what they derive nourishment, which makes a gap in any discussion about the factors limiting sizes of populations. The sizes of adult populations and the factors that limit them are also in need of further study.
Not until about the middle of the book does Dr Savage reach the work which has been his main interest. Fig. 20 is a map of the British Isles covered with ‘isophenes', lines drawn through places where the spawning date is the same. In a small area of South Wales and of North Devon, and in the south of Ireland, spawning is in January; to be exact, before 30 January which is day 30. Spawning between days 31 and 40 is also confined to the south and west. Late spawning, between days 71 and 80, is a phenomenon of the east side of England and the midlands. The latest spawning, after day 100 (10 March), is in the Pennine area. Incidentally this map is not accompanied by any information about how the data was gathered, nor on how many observations each isophene is based.
In general the earliest breeding is found in places with the highest rainfall. Temperatures near freezing-point a month before spawning are associated with early spawning at a lower rainfall than at higher temperatures. When the weather two months before spawning is examined, early spawning is found to be associated with temperature above 6°C and is not greatly affected by rainfall. Light also plays a part. It is surmised that these climatic factors react on the frog through one or several species of algae, an outburst of which stimulates spawning. Some readers will be disappointed to find that there is still this big gap to be bridged by theory only, but the author argues cogently in support of the line he has chosen to pursue.
I am not competent to pass an opinion on the joint functional regression diagrams and the statistical methods on which these conclusions are based, but my colleague, Miss C. Kipling, praises them. Anyone interested in the factors governing any regular event such as oviposition or emergence is likely to find Dr Savage's method worth study.
There is a danger that some readers, put off by the incompleteness of the earlier chapters, will lay the book aside before they reach the author’s main work. On the other hand it is valuable to have this scattered information brought together in one place. Many will be grateful to Dr Savage for bringing it together, and he is to be congratulated on the amount that his own researches have contributed and on the fair way in which he has written about what is known and what is not known.
The following review for The Naturalist appeared over the initials E.B. Since the journal was based in the University of Leeds I soon found that the reviewer was Edward BROADHEAD, then senior lecturer in zoology and an expert on psocids, insects on which my ignorance is total:
This book is an account of the research, carried out by the author as a recreation, on the ecology of the common frog. It covers all stages of the life history egg, tadpole, juvenile and adult frogs and much information is brought together on parasites, distribution and breeding behaviour. The section on the relation between spawning dates and weather in chapter 8 is new and of great interest, and a full account of the method used and of other statistical methods in chapter 10 adds considerably to the value of the book.
The book is written in a chatty and enthusiastic style. The author's work is recorded in great detail and with a wealth of comment and discussion, but the book would have been improved by a better balance. The work of others is mentioned but never in the detail accorded to the author’s own papers, and very often the comment and discussion on some of the factual material presented is excessive, much space being given in some places to pure conjecture as, for instance, on pp. 79 et seq. where density dependence is discussed.
Finally, my old friend ‘Amo’, Emmanuel Ciprian AMOROSO FRS (1901-1982), wrote the following for New Scientist. He, I think, had met Savage at Zoological Society of London meetings. Amo had recently worked on the ‘marsupial frog’ Gastrotheca marsupiata while professor at physiology at the Royal Veterinary College.
Maxwell Savage has been interested in the Common Frog and its tadpoles for a long time and he has courageously undertaken to write this account of their lives. Nor does he speak only as a compiler; his 30 years of research on the amphibia qualify him unusually well for the undertaking. The material is organized in 10 chapters and in these the student of behaviour should find as much of interest as the ecologist, for examples of observed behaviour under a wide range of circumstances are given liberally. The general biologist should appreciate the information presented on reproduction, growth, morphology and like topics, while students of population may note outstanding factual contributions and unanswered questions alike.
The author is at his best when he is talking about the riddle of migration and his claims for his algal hypothesis are modest. The book not only solves many of the mysteries surrounding the movement of the frogs to the ponds but is also replete with facts about their life history and behaviour. It is unfortunate, however, that only a small group of specialists will be able to profit properly from this work, as several defects reduce its value for a wider audience. The organization is loose and the more outstanding highlights of the researches are swamped in the telling by redundant detail; it is thus difficult to use the volume for reference. Furthermore, each section seems to be addressed to those who already know that field and its history rather thoroughly. Perhaps the author will reply that he intended his book for just such an audience. If so, it is a very limited one; and it may be questioned whether anyone with so great a grasp of the subject will not have made a similar synthesis for himself already.
Altogether, while one familiar with Savage's work will find here little that is wholly new, there is a vigour and a modicum of fresh thought that is stimulating and as a summary of Savage's thinking the book is valuable.
I can add very little to those reviews other than to point out that while some of the discussions are to modern eyes completely beyond their sell-by-date (matters physiological for example) and, as I remarked in the first article of this series, errors were made in drawing the statistical material together, the whole approach that Savage took (‘he is ready to delve into any subject that may illuminate some phase of the life of his chosen animal’, as Zweifel put it) shines through.
Savage did himself a disservice by not adding some biographical information and the circumstances under which he operated as a part-time herpetologist. While the research, like any other, has to be judged on its merits regardless of the circumstances of the person doing it, I do think some information would have added greatly to the interest in his work and to a much deeper appreciation of his devotion to his pursuit. I also think Amo hit the nail on the head by recognising the difficulty the average reader would have in reading the book and in implying that hard editing would have been of great benefit; there the publishers were amiss in not insisting on it. Savage, though, answered the question of who the book was intended for in the first paragraph of the Preface: ‘I wrote the book for myself’.
In the next article I discuss Savage’s big idea and the evidence he gathered.
Amoroso. EC. 1961. Book Review. The Ecology and Life History of the Common Frog by R. Maxwell Savage. New Scientist 12 (23 November 1961), 511-512.
EB. 1961. Book Review. The Ecology and Life History of the Common Frog by R. Maxwell Savage. The Naturalist 1961, 35.
Macan TT. 1962. Book Review. The Ecology and Life History of the Common Frog by R. Maxwell Savage. Journal of Animal Ecology 31, 398-399.
Zweifel RG 1962. Book Review. The Ecology and Life History of the Common Frog (Rana temporaria temporaria) by R. Maxwell Savage. Copeia 1962, 667-669.
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