Northern Fur Seal Behavior and EcologyBehavior and Ecology of the Northern fur Seal by Roger L. GentryReview by: Daryl J. BonessEcology, Vol. 79, No. 8 (Dec., 1998), pp. 2972-2973Published by: Ecological Society of AmericaStable URL: http://www.jstor.org/stable/176533 .

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2972 BOOK REVIEWS Ecology, Vol. 79, No. 8

Ecology, 79(8), 1998, pp. 2972-2973 ? 1998 by the Ecological Society of America

NORTHERN FUR SEAL BEHAVIOR AND ECOLOGY

Gentry, Roger L. 1998. Behavior and ecology of the north- ern fur seal. Princeton University Press, Princeton, New Jer- sey. xiii + 392 p. $69.50, ISBN: 0-691-03345-5 (acid-free paper).

In the last decade a number of books have been published on pinniped behavior and ecology but none has been a de- tailed single-species account nor as focused as this book. In his position as a research biologist with the National Marine Fisheries Service, Gentry has had the opportunity and re- sources to accumulate the kind of data sets that most aca- demics can only dream about. In this book he describes a 19- year study of the northern fur seal, a heavily managed species, that was aimed at addressing very specific behavioral ques- tions about a nearly 40-year decline in fur seal pup produc- tion.

The book is more heavily weighted to the reproductive behavior of northern fur seals than to its ecology. The pre- dominant coverage of fur seal ecology is in examining the influence of climatic regime shifts (e.g., the Aleutian Low and El Niho-Southern Oscillations) and width of the conti- nental shelf around breeding islands on breeding success and population trends. The book consists of 15 chapters that are organized into five parts. The first part sets the scene for the rest of the book. It provides a short introduction to the natural history of the northern fur seal and of pinnipeds in general. It also describes population changes in this species over the past 40 years, emphasizing the period from 1974-1986 in more detail. The last chapter in this section highlights the importance of various temporal scales in the behavior and ecology of northern fur seals (e.g., several-day foraging cy- cles, annual breeding cycles, decadal climatic cycles). The next two parts deal with the mating system and male and female reproductive behavior. Part two presents the details of male competition (e.g., establishment and maintenance of territories, energetics of male reproductive effort, and lifetime copulation rates), addresses the question of female mate choice, and examines the use of space and grouping behavior of females. Part three deals in more detail with three aspects of behavior that Gentry feels are especially important to un- derstanding the fur seal mating system: site fidelity and phil- opatry, estrus behavior, and ontogeny of male territorial be- havior. Part four describes maternal behavior, its conse- quences in terms of pup growth, and variation resulting from environmental factors and individual tendencies. The last part summarizes the findings in relation to some of the initial management questions that drove the research, provides some comparisons with other otariids, and raises further questions to be addressed with future research.

Gentry started out with a particularly difficult challenge because he not only wanted to address the questions raised about this species by wildlife managers, he wanted to make the book useful to academics with general theoretical interests and to provide enough detail for comparative purposes for other seal researchers. These somewhat divergent goals have

led to compromises in style and content that make the book harder to use for some readers than for others. For example, a deliberate decision to exclude a general theoretical frame- work in which to interpret the data will mean that an academic (behavioral ecologists, ethologists, comparative psycholo- gists, etc.) who wishes to understand the northern fur seal mating system in a broader context will get minimal help from the book. A specialist interested in evaluating and using the extensive empirical results for their own synthesis, may become frustrated by the constant need to turn to the "notes" at the end of the book to obtain details about methodology or statistical analysis. This style is similar to the reference notes in a Science paper, which on a small scale is not so bad. Here, the problem is you end up with over 30 pages of pertinent information for which you have to jump between your place in the book and the notes at the back. The book seems best suited for what is perhaps its primary purpose, an account of the role reproductive behavior and ecology has played in the fur seal population in light of the numerous years of planned annual kills of juvenile males.

Having noted these relatively minor difficulties, I am mere- ly giving you forewarning, not suggesting you avoid the book if your interest is for one of the first two reasons. One strong aspect of the studies reported in this book is a mix of ob- servational and experimental approaches to investigate spe- cific questions. Experimental approaches are almost non-ex- istent in research on mating systems in marine mammals, or for that matter, in most large mammals. The most elegant and enlightening experiments described are those associated with estrus behavior. By controlling access of females to males and by using what amounted to a "chastity belt" to prevent copulation, Gentry investigated questions about stimuli suf- ficient or necessary to trigger or terminate estrus. Other ex- perimental studies involved removing males from their ter- ritories and observing resettlement on territories, withholding pups from sucking for periods of time or artificially feeding them to change their level of demand for milk in order to examine the consequent effects on attendance periods, and moving females and pups of different ages to determine the potential for changing breeding sites.

If you have read Gentry's previous book with Gerald Kooy- man on maternal strategies in pinnipeds you will find the section on maternal strategy in this book updates the original ideas. The notion of a latitudinal dine and overall species- specific strategies are discounted here and greater importance is given to local ecological conditions, particularly with re- spect to maternal attendance and foraging patterns. In the case of the northern fur seal, excellent data are presented on attendance-foraging cycles at several colonies in which the marine environments are very different. Likewise, the mul- tiple years of study at the same environments produced vari- ation in cycles resulting from climatic changes.

One disappointment in the book, to which I alluded above, is the limited extent to which the fur seal data are integrated into broader contexts of reproductive behavior and behavioral ecology, and even into marine mammalogy. The references

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December 1998 BOOK REVIEWS 2973

to other pinniped literature are fairly selective and references to more general literature are minimal. On a more mundane note, the final proofreading of the manuscript could have been better. Clearly there was a problem with certain character recognition in the software used to set the book text since all degree symbols for temperatures show up as blanks, and "X's used in dimensions show up as infinity symbols.

In short, this book has something for a wide range of read- ers but its efforts to reach such a wide audience will result in some grumbling by each type of reader. You have heard a bit of mine (a behavioral ecologist specializing in pinniped reproductive strategies) but I would have purchased the book for its detailed analysis of reproductive behavior of male and female fur seals. It is an excellent case study for wildlife managers and conservation biologists, illustrating the need for long-term studies of managed species and of the value of studying behavior in various ecological contexts, not just monitoring population trends. For the theoretically oriented academic who is not a marine mammal specialist, the species

is particularly interesting as a highly polygynous one in which opportunities for female choice appear to be very limited. The nature of interactions between males and females before females become receptive can be extremely aggressive on the part of males and lead to the injury or even death of females. The ontogeny of territorial behavior, philopatry, and site fi- delity in combination provide for the potential for cooperative behavior in male territory turnovers that would not be readily apparent without detailed studies of the nature of those de- scribed in this book. Lastly, the data presented in this book will lead to many interesting ideas that will hopefully stim- ulate students to pursue them either in this species or others that are appropriate.

DARYL J. BONESS

National Zoological Park Department of Zoological Research Smithsonian Institution Washington, D.C. 20008

Ecology, 79(8), 1998, pp. 2973-2974 (C 1998 by the Ecological Society of America

To BE, OR NOT To BE SPATIAL-THAT Is THE QUESTION

Tilman, David, and Peter Kareiva, editors. 1997. Spatial ecology: the role of space in population dynamics and interspecific interactions. Monographs in Population Biol- ogy, 30. Princeton University Press, New Jersey. xiii + 365 p. $85.00, ?59.50 (cloth), ISBN: 0-691-01653-4 (alk. paper); $35.00, ?25.00 (paper), ISBN: 0-691-01652-6 (alk. paper).

The concept of space in ecological studies has been ne- glected for many years although the spatial component pres- ent in nature can be regarded as a functional property of ecosystems processes. David Tilman and Peter Kareiva have collected in this monograph a remarkably wide range of con- cepts and ideas that have been developed in recent years concerning the role of space in ecology.

Part I, "Single species dynamics in spatial habitats," ex- amines the concept of space in relation to the dynamics of a single species. Beginning with Levins's model, the text moves on to more complex dynamics in metapopulation models in- cluding the incidence function model (IF) and the implication of space and stochastic processes in population dispersal. Part II, "Parasites, pathogens, and predators in a spatially complex world," is more specific to host-parasitoid systems, intro- ducing the concept of heterogeneity in relation to spatial pat- terns of parasitism. Basic epidemiological concepts are pre- sented in a spatial context examining different aspects of epidemics. The dynamics of measles and the role of dynam- ical synchronicity in epidemics patterns is discussed in re- lation to SEIR models. The genetics and the spatial ecology of species interactions is described by using the Silene-Us- tilago system and three experiments illustrate the impact of genetics on metapopulation dynamics. Competition among species is described in Part III, "Competition in a spatial world." Implicit and explicit spatial structure are explored to

describe the dynamics of competition across spatial habitats at different temporal and spatial scales. Extinction dynamics and habitat destruction are discussed in relation to metapo- pulation-like models. Local versus regional processes as con- trols of species richness point out the importance of making specific predictions about species richness across different spatial scales and the need to integrate and further understand processes acting at different ecological scales. The final anal- ysis of the concepts explored in this monograph are presented in Part IV, "The final analysis: does space matter or not? and how will we test our ideas?" Pattern formation and different approaches to describe scaling laws in ecology using spatial stochastic models are described, including nonlinear systems. Spatially implicit models using production functions are pre- sented for a variety of organisms from terrestrial to aquatic environments. The empirical assessment of spatial theory is still an open challenge and different experimental approaches aimed at determining the effects of space on species coex- istence and the maintenance of biodiversity are proposed in the closing chapter of this book.

From mechanistic to phenomenological models the intro- duction of space can give novel information on the com- plexities underlying biotic and abiotic processes. The major difficulties are how one should account for space in ecological studies and transfer this information into sampling strategies and data modeling. The ideas presented and discussed in this monograph suggest that this goal can not be achieved by generality, but rather by using different models describing specific processes at different spatial scales. Spatial autocor- relation should be taken into account in ecological studies, since it can generate spurious or inflated results on how well a model fits the data. The role of transient dynamics seems to be a key point for a better understanding of nonequilibrium behavior in communities dynamic. In dissipative, nonlinear,

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