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Island Survivors: The ecology of the soay sheep of St. Kilda
238
BOOK REVIEWS
Biological Management and Conservation. By M. B. Usher. Chapman and Hall, London. 1973. 394 + xiii pp. 19 plates. 16 X 24 cm. Price: £6.40. In this well-produced and attractively presented book Dr Usher attempts to give an account of the management of species-populations and ecosystems for conservation. The attempt is a failure because the author tries to cover too wide a field, because he is unable to distinguish the relevant from the merely interesting, and because his arrangement of the book is confused and irrational. Conservation management is an applied science. It starts with certain aims, which can be achieved only within a framework constrained by ecological parameters. Instead of first considering the aims of management and the methods of achieving them, Dr Usher has preferred to devote the first half of his book to a long account of ecological concepts and facts which is neither comprehensive enough to serve as a sound elementary textbook of ecology, nor sufficientlyconcise and selective to fulfil the purpose for which he has intended it. In partial consequence of this, Part II, Application--which should have contained the most important and original material in the book--is sadly incomplete. Moreover, it is considerably diluted by chapters on Conservation and Education and Conservation and Recreation. These topics are, of course, highly relevant to conservation as a whole, but could have been profitably separated from purely biological aspects of management, which the book should have covered more thoroughly. Part III of Biological Management and Conservation, Planning, is devoted entirely to the Management Plan, that overvalued document which has given so much cosy confidence to inactive conservationists. When shall we see the apotheosis of the management plan? Revised, rewritten, altered, expanded, changed and refined, it will stand in tattered triumph in the archives of that reserve in which the aims of management are actually being achieved by management--as dynamic as the ecosystem it has sought to describe. The book contains two appendices. Appendix I, Matrix Operations, may be treated with affectionate indulgence; no more, and no less, useful than countless other mathematical techniques used by ecologists, matrix algebra has become a sort of trade mark by which biologists of the York school may be instantly recognised. Appendix II, Some Commonly Used Statistics, gives a few values of Student's 't', X2, and the correlation coefficient. The book is well illustrated with good photographs and clear text figures and diagrams. M. G. MORRIS
Island Survivors: The Ecology of the Soay Sheep of St. Kilda. Edited by P. A. Jewell, C. Milner & J. Morton Boyd. Athlone Press, London. 1974. Price: £8.00. This book is correctly described on its dust jacket and in the Introduction, as primarily a record of studies carried out in the St. Kilda Archipelago on the feral
BOOK REVIEWS
239
Soay Sheep, from 1959 to 1969. A large number of people were involved at one time or another, including the editors and the other 13 contributors, and chapters tend to deal with their special interests, rounded offby a 'Synthesis' chapter by Morton, Boyd and Jewell. The volume is well produced and contains some very good illustrations, including maps, sketches of sheep behaviour, colour photographs of the sheep and some black-and-white photographs that clearly convey the remoteness of these islands--considered to be the windiest place in the British Isles. The Soay is among the most primitive of the domesticated breeds of sheep in existence and has been feral on the main island (Hirta) since 1932. The book describes the studies of population dynamics, social organisation, breeding cycles, behaviour, pasture utilisation and quality, pathology and parasites of the Soays, which are regarded as central to the St. Kilda ecosystem because of the effect of sheep grazing on the quality of the vegetation and fauna. A comparison of the grasslands on opposite sides of the chasm separating Dun from Hirta shows this effect, since Dun is ungrazed but similarly exposed to sea-birds and spray. The vegetation of Dun is described as rank Festucetum, poorer in species than the grazed Armeria and Plantago swards on Hirta. However, although in much of Britain grazing is essential to the maintenance of grassland, this is not so here: there are no trees or scrub anyway, just grassland and heather. The risks of damage, due to overgrazing of steep slopes in a high wind and rainfall area, are recognised but the overall effect of sheep grazing is clearly regarded as in the interests of conservation in general, quite apart from the intrinsic interest of the sheep themselves. The main aim of these studies has been to describe a natural process of regulation of numbers of a large herbivore in the absence of predators. The latter may appear surprising since there must be a great deal of opportunity for predation, especially when mortality is high and weak animals numerous. Carrion is disposed of by birds, which will also attack and kill weak animals, and some insects. It is also worth noting that another major sheep pest, Lucilia (the 'greenbottle' responsible for 'fly strike') has never been recorded in any of the islands. This may be one of the few advantages of the high winds that otherwise appear to have an adverse effect on mortality. Such studies are clearly essential if conservation management is to be based on an understanding of the mechanisms whereby numbers are currently regulated in the island environment. The efforts of all those involved in obtaining information in such a difficult environment deserves applause and it would really be churlish in the extreme to appear at all critical. Nevertheless, the hopes of those who contributed that their results would also be of use in the management of wildlife in general, deserve critical examination. Furthermore, it is pertinent to ask whether such studies can contribute to our understanding of the general principles underlying applied ecology and, in parenthesis, if they cannot, what sort of studies can do so. In the absence of predators, a sheep population is likely to increase in size until it
240
BOOK REVIEWS
runs short of food, unless disease supervenes. On Hirta, starvation appears to be reached when stocking rates become too high, although deaths appear to involve concomitant heavy infestations with internal parasites (although not liver flukes). It would be interesting to know whether the sheep distribute their faeces in a highly non-uniform manner, due, for example, to the frequency with which they take shelter from the wind, and whether heavily dunged areas are included in the grazing only when stocking rates are high. Since herbage production varies from year to year, a 'crash' situation is likely as stocking rate increases, when a high sheep population coincides with a low herbage yield. This is inevitable if there are insufficient 'feed-back' mechanisms to regulate population increase in relation to food supply. In most sheep populations, the first line of such regulation occurs at mating. Fat ewes have more lambs and thin ewes have, on average, a lower litter size. This does not appear to be of major significance on Hirta, where the mean litter size is only c. 1.13 in mature ewes and 0.39 in yearlings, although it is not possible to tell whether groups of ewes on the better home ranges have a higher reproductive rate than those on the poorer areas. Mortality rates, however, are high and life expectancy is only about 3 years for ewes and 1.3 years for males. The ratio of males to females (about 1:5 between 1959 and 1972) is, by agricultural standards, very high and should ensure efficient mating, especially when combined with behavioural patterns (e.g. 'tending' by dominant rams, for 24 h or so) that minimise pestering of the ewes during oestrus. Barrenness should be minimal in these circumstances but at a very high cost of maintaining more males than are strictly necessary. From an evolutionary point of view, of course, it is not easy to define what is strictly necessary. A very competitive situation is created, in which rams expend a lot of energy and reduce their grazing time in the autumn, thus greatly exacerbating their problems in surviving the winter. This appears very wasteful in the ram lambs, who do not appear to achieve any breeding success but still waste their substance in rutting. However, one way or another the number of males has to be reduced and, from the point of view of the population as a whole, the sooner the better. One notable feature of ram behaviour is that the fighting is done well before mating. Good agricultural practice also would put rams together to sort out their ranking order well before they were to be used. Males thus enter the winter less equipped with fat reserves (kidney fat mainly?) than do females and the major period of mortality virtually coincides with lambing, in the late winter and early spring. At this time, animals that are very thin must be extremely susceptible to the combined effects of wind and rain and the presence of hundreds of dry-stone shelters ('cleits') must be of considerable significance. Winter survival is negatively related to population density and low availability of nutrients in late winter appears to be the major determinant of mortality. It is interesting that although mineral status is generally good (as shown by radiography of skeletons), there is a possibility of phosphorus deficiency being a major factor controlling population size. Any mineral could play
BOOK REVIEWS
24l
such a part if it was in very short supply, but the role of nematode parasites might repay investigation in this particular case. The general picture, then, is of a population of herbivores that increases until it runs out of food, whereupon numbers die, but chiefly of males. This latter point makes sense if population increase is desired but not once the population has reached its optimum size. The female component of the population retains its capacity to increase population size after a 'crash' but there seems to be no mechanism for relating the rate of increase to food supply. Overgrazing in early spring will reduce pasture production and thus exacerbate the situation already arrived at, but it is possible that predation might allow a larger population to be sustained by removing weak animals earlier than is the case with starvation. Would that be desirable, however? The main conclusion reached by the authors, in relation to Hirta, is that interference should be minimal, and probably confined to a consideration of culling, as is done with the red deer on Rhum, if this appears necessary to prevent serious damage due to overgrazing. It is implied that even this might take the form of a simulated 'crash', followed by a long period of population build-up, rather than by frequent adjustments. In a brief Appendix, Milner describes the use of a simulation model and argues, rightly in my view, that the Soays on Hirta are ideally suited to this approach. In an area where ~nformation is difficult and costly to acquire, this is surely the way to state what is known, as a means of deciding what additional data are needed. Milner also stresses the value of experimenting on a model in building the confidence of those who have to take difficult decisions about nature reserves and how they should be managed. The value of the model in combining in a communicable form the wide range of information described in this book, should be very great and its use for predictive purposes will increase with time and further data. It would have been interesting to have included more discussion about the objectives of conservation in general and in St. Kilda in particular. Understanding is most profitably sought when it is related to specified purposes, although exploratory fact-finding must usually precede decisions about purpose. To an agriculturalist, the sheep population must appear to involve much unnecessary starvation and perhaps man can usefully be integrated into ecosystems, just as the 'cleits' he built have been incorporated: but the diversity of carrion-eaters is probably at its maximum as things are and diversity of species seems to be a major aim of conservation. Biologically speaking, it would be interesting to know more of the role of sea-bird droppings in maintaining the herbage production on which the sheep population is fed. The input of minerals from spray and these bird droppings are features unique to small islands and their significance could best be disentangled in an uninhabited, grassy isle. There is a great deal of interesting information in this book and it is clearly and attractively presented. It can be recommended to all who are interested in a careful
242
BOOK REVIEWS
record of most, if not all, of the important aspects of a fascinating ecosystem. Furthermore, as Sir Frank Fraser Darling says in his Preface, the Soay sheep is a precious possession from the past, which the authors have treated with respect and affection. C. R. W. SPEDDING Institute of Terrestrial Ecology. Research in Scotland. Report for 1971. Natural Environment Research Council, Banchory Research Station, Banchory, Kincardineshire, Scotland. 1974. 85 pp., 15 cm X 24 cm. Price: 50p. Caerlaverock. A Conservation Publication of the Wildfowlers Association of Great Britain and Ireland, 104 Watergate St., Chester. 1974. 84 pp., illust.
Loch Leven. Wildfowlers Association of Great Britain and Ireland. 1974. 124 pp., illust. The demise of the Nature Conservancy (UK) and its replacement, in so far as aquisition and management are concerned, by the Nature Conservancy Council (Department of the Environment) and, as relating to research, by contracts mainly with the Institute of Terrestrial Ecology of the Natural Environment Research Council (Department of Education and Science) has been notified already by Professor J. B. Cragg in his review of the Merlewood Research Station, 1970-1972 (Biol. Conserv., 6, 317-8). The present review deals with research in Scotland in 1971-73 and it is worth noting at the outset that both this and the Merlewood Report were published by the Natural Environment Research Council and that, although the Scottish Report also bears the imprint of the Institute of Terrestrial Ecology, the actual transfer of research responsibility to the Institute did not have effect until November 1973. The research reported upon is therefore almost entirely that carried out by the old Nature Conservancy (UK) and it remains to be seen what effect the change of responsibility has and whether--as some fear--there will be a tendency for management-directed ecological research to become side-tracked in favour of socalled fundamental research. We can but wait and hope; meantime, it is good to know that during 1971 -1973 research in Scotland remained management-directed and that a Wetlands (including Peatlands) Group is included in the staff of the Institute. The present Report chronicles the establishment, late in 1972, of the Banchory Research Station, at Hill of Brathens near Banchory on Deeside, incorporating in part the old Banchory Research Station at Blackhall, Banchory, at which the work on red grouse (Lapogus lapogus) continues. Research dealing with open freshwater
BOOK REVIEWS
Biological Management and Conservation. By M. B. Usher. Chapman and Hall, London. 1973. 394 + xiii pp. 19 plates. 16 X 24 cm. Price: £6.40. In this well-produced and attractively presented book Dr Usher attempts to give an account of the management of species-populations and ecosystems for conservation. The attempt is a failure because the author tries to cover too wide a field, because he is unable to distinguish the relevant from the merely interesting, and because his arrangement of the book is confused and irrational. Conservation management is an applied science. It starts with certain aims, which can be achieved only within a framework constrained by ecological parameters. Instead of first considering the aims of management and the methods of achieving them, Dr Usher has preferred to devote the first half of his book to a long account of ecological concepts and facts which is neither comprehensive enough to serve as a sound elementary textbook of ecology, nor sufficientlyconcise and selective to fulfil the purpose for which he has intended it. In partial consequence of this, Part II, Application--which should have contained the most important and original material in the book--is sadly incomplete. Moreover, it is considerably diluted by chapters on Conservation and Education and Conservation and Recreation. These topics are, of course, highly relevant to conservation as a whole, but could have been profitably separated from purely biological aspects of management, which the book should have covered more thoroughly. Part III of Biological Management and Conservation, Planning, is devoted entirely to the Management Plan, that overvalued document which has given so much cosy confidence to inactive conservationists. When shall we see the apotheosis of the management plan? Revised, rewritten, altered, expanded, changed and refined, it will stand in tattered triumph in the archives of that reserve in which the aims of management are actually being achieved by management--as dynamic as the ecosystem it has sought to describe. The book contains two appendices. Appendix I, Matrix Operations, may be treated with affectionate indulgence; no more, and no less, useful than countless other mathematical techniques used by ecologists, matrix algebra has become a sort of trade mark by which biologists of the York school may be instantly recognised. Appendix II, Some Commonly Used Statistics, gives a few values of Student's 't', X2, and the correlation coefficient. The book is well illustrated with good photographs and clear text figures and diagrams. M. G. MORRIS
Island Survivors: The Ecology of the Soay Sheep of St. Kilda. Edited by P. A. Jewell, C. Milner & J. Morton Boyd. Athlone Press, London. 1974. Price: £8.00. This book is correctly described on its dust jacket and in the Introduction, as primarily a record of studies carried out in the St. Kilda Archipelago on the feral
BOOK REVIEWS
239
Soay Sheep, from 1959 to 1969. A large number of people were involved at one time or another, including the editors and the other 13 contributors, and chapters tend to deal with their special interests, rounded offby a 'Synthesis' chapter by Morton, Boyd and Jewell. The volume is well produced and contains some very good illustrations, including maps, sketches of sheep behaviour, colour photographs of the sheep and some black-and-white photographs that clearly convey the remoteness of these islands--considered to be the windiest place in the British Isles. The Soay is among the most primitive of the domesticated breeds of sheep in existence and has been feral on the main island (Hirta) since 1932. The book describes the studies of population dynamics, social organisation, breeding cycles, behaviour, pasture utilisation and quality, pathology and parasites of the Soays, which are regarded as central to the St. Kilda ecosystem because of the effect of sheep grazing on the quality of the vegetation and fauna. A comparison of the grasslands on opposite sides of the chasm separating Dun from Hirta shows this effect, since Dun is ungrazed but similarly exposed to sea-birds and spray. The vegetation of Dun is described as rank Festucetum, poorer in species than the grazed Armeria and Plantago swards on Hirta. However, although in much of Britain grazing is essential to the maintenance of grassland, this is not so here: there are no trees or scrub anyway, just grassland and heather. The risks of damage, due to overgrazing of steep slopes in a high wind and rainfall area, are recognised but the overall effect of sheep grazing is clearly regarded as in the interests of conservation in general, quite apart from the intrinsic interest of the sheep themselves. The main aim of these studies has been to describe a natural process of regulation of numbers of a large herbivore in the absence of predators. The latter may appear surprising since there must be a great deal of opportunity for predation, especially when mortality is high and weak animals numerous. Carrion is disposed of by birds, which will also attack and kill weak animals, and some insects. It is also worth noting that another major sheep pest, Lucilia (the 'greenbottle' responsible for 'fly strike') has never been recorded in any of the islands. This may be one of the few advantages of the high winds that otherwise appear to have an adverse effect on mortality. Such studies are clearly essential if conservation management is to be based on an understanding of the mechanisms whereby numbers are currently regulated in the island environment. The efforts of all those involved in obtaining information in such a difficult environment deserves applause and it would really be churlish in the extreme to appear at all critical. Nevertheless, the hopes of those who contributed that their results would also be of use in the management of wildlife in general, deserve critical examination. Furthermore, it is pertinent to ask whether such studies can contribute to our understanding of the general principles underlying applied ecology and, in parenthesis, if they cannot, what sort of studies can do so. In the absence of predators, a sheep population is likely to increase in size until it
240
BOOK REVIEWS
runs short of food, unless disease supervenes. On Hirta, starvation appears to be reached when stocking rates become too high, although deaths appear to involve concomitant heavy infestations with internal parasites (although not liver flukes). It would be interesting to know whether the sheep distribute their faeces in a highly non-uniform manner, due, for example, to the frequency with which they take shelter from the wind, and whether heavily dunged areas are included in the grazing only when stocking rates are high. Since herbage production varies from year to year, a 'crash' situation is likely as stocking rate increases, when a high sheep population coincides with a low herbage yield. This is inevitable if there are insufficient 'feed-back' mechanisms to regulate population increase in relation to food supply. In most sheep populations, the first line of such regulation occurs at mating. Fat ewes have more lambs and thin ewes have, on average, a lower litter size. This does not appear to be of major significance on Hirta, where the mean litter size is only c. 1.13 in mature ewes and 0.39 in yearlings, although it is not possible to tell whether groups of ewes on the better home ranges have a higher reproductive rate than those on the poorer areas. Mortality rates, however, are high and life expectancy is only about 3 years for ewes and 1.3 years for males. The ratio of males to females (about 1:5 between 1959 and 1972) is, by agricultural standards, very high and should ensure efficient mating, especially when combined with behavioural patterns (e.g. 'tending' by dominant rams, for 24 h or so) that minimise pestering of the ewes during oestrus. Barrenness should be minimal in these circumstances but at a very high cost of maintaining more males than are strictly necessary. From an evolutionary point of view, of course, it is not easy to define what is strictly necessary. A very competitive situation is created, in which rams expend a lot of energy and reduce their grazing time in the autumn, thus greatly exacerbating their problems in surviving the winter. This appears very wasteful in the ram lambs, who do not appear to achieve any breeding success but still waste their substance in rutting. However, one way or another the number of males has to be reduced and, from the point of view of the population as a whole, the sooner the better. One notable feature of ram behaviour is that the fighting is done well before mating. Good agricultural practice also would put rams together to sort out their ranking order well before they were to be used. Males thus enter the winter less equipped with fat reserves (kidney fat mainly?) than do females and the major period of mortality virtually coincides with lambing, in the late winter and early spring. At this time, animals that are very thin must be extremely susceptible to the combined effects of wind and rain and the presence of hundreds of dry-stone shelters ('cleits') must be of considerable significance. Winter survival is negatively related to population density and low availability of nutrients in late winter appears to be the major determinant of mortality. It is interesting that although mineral status is generally good (as shown by radiography of skeletons), there is a possibility of phosphorus deficiency being a major factor controlling population size. Any mineral could play
BOOK REVIEWS
24l
such a part if it was in very short supply, but the role of nematode parasites might repay investigation in this particular case. The general picture, then, is of a population of herbivores that increases until it runs out of food, whereupon numbers die, but chiefly of males. This latter point makes sense if population increase is desired but not once the population has reached its optimum size. The female component of the population retains its capacity to increase population size after a 'crash' but there seems to be no mechanism for relating the rate of increase to food supply. Overgrazing in early spring will reduce pasture production and thus exacerbate the situation already arrived at, but it is possible that predation might allow a larger population to be sustained by removing weak animals earlier than is the case with starvation. Would that be desirable, however? The main conclusion reached by the authors, in relation to Hirta, is that interference should be minimal, and probably confined to a consideration of culling, as is done with the red deer on Rhum, if this appears necessary to prevent serious damage due to overgrazing. It is implied that even this might take the form of a simulated 'crash', followed by a long period of population build-up, rather than by frequent adjustments. In a brief Appendix, Milner describes the use of a simulation model and argues, rightly in my view, that the Soays on Hirta are ideally suited to this approach. In an area where ~nformation is difficult and costly to acquire, this is surely the way to state what is known, as a means of deciding what additional data are needed. Milner also stresses the value of experimenting on a model in building the confidence of those who have to take difficult decisions about nature reserves and how they should be managed. The value of the model in combining in a communicable form the wide range of information described in this book, should be very great and its use for predictive purposes will increase with time and further data. It would have been interesting to have included more discussion about the objectives of conservation in general and in St. Kilda in particular. Understanding is most profitably sought when it is related to specified purposes, although exploratory fact-finding must usually precede decisions about purpose. To an agriculturalist, the sheep population must appear to involve much unnecessary starvation and perhaps man can usefully be integrated into ecosystems, just as the 'cleits' he built have been incorporated: but the diversity of carrion-eaters is probably at its maximum as things are and diversity of species seems to be a major aim of conservation. Biologically speaking, it would be interesting to know more of the role of sea-bird droppings in maintaining the herbage production on which the sheep population is fed. The input of minerals from spray and these bird droppings are features unique to small islands and their significance could best be disentangled in an uninhabited, grassy isle. There is a great deal of interesting information in this book and it is clearly and attractively presented. It can be recommended to all who are interested in a careful
242
BOOK REVIEWS
record of most, if not all, of the important aspects of a fascinating ecosystem. Furthermore, as Sir Frank Fraser Darling says in his Preface, the Soay sheep is a precious possession from the past, which the authors have treated with respect and affection. C. R. W. SPEDDING Institute of Terrestrial Ecology. Research in Scotland. Report for 1971. Natural Environment Research Council, Banchory Research Station, Banchory, Kincardineshire, Scotland. 1974. 85 pp., 15 cm X 24 cm. Price: 50p. Caerlaverock. A Conservation Publication of the Wildfowlers Association of Great Britain and Ireland, 104 Watergate St., Chester. 1974. 84 pp., illust.
Loch Leven. Wildfowlers Association of Great Britain and Ireland. 1974. 124 pp., illust. The demise of the Nature Conservancy (UK) and its replacement, in so far as aquisition and management are concerned, by the Nature Conservancy Council (Department of the Environment) and, as relating to research, by contracts mainly with the Institute of Terrestrial Ecology of the Natural Environment Research Council (Department of Education and Science) has been notified already by Professor J. B. Cragg in his review of the Merlewood Research Station, 1970-1972 (Biol. Conserv., 6, 317-8). The present review deals with research in Scotland in 1971-73 and it is worth noting at the outset that both this and the Merlewood Report were published by the Natural Environment Research Council and that, although the Scottish Report also bears the imprint of the Institute of Terrestrial Ecology, the actual transfer of research responsibility to the Institute did not have effect until November 1973. The research reported upon is therefore almost entirely that carried out by the old Nature Conservancy (UK) and it remains to be seen what effect the change of responsibility has and whether--as some fear--there will be a tendency for management-directed ecological research to become side-tracked in favour of socalled fundamental research. We can but wait and hope; meantime, it is good to know that during 1971 -1973 research in Scotland remained management-directed and that a Wetlands (including Peatlands) Group is included in the staff of the Institute. The present Report chronicles the establishment, late in 1972, of the Banchory Research Station, at Hill of Brathens near Banchory on Deeside, incorporating in part the old Banchory Research Station at Blackhall, Banchory, at which the work on red grouse (Lapogus lapogus) continues. Research dealing with open freshwater