摘要:

ABSTRACTWe analyzed 4 meristic and 32 morphometric cranial traits of 612 adult specimens of spotted dolphins (Stenella attenuata) from the eastern tropical Pacific Ocean for sexual dimorphism. Eleven 5″ latitude/longitude blocks with five or more of each sex were assessed with a two‐way ANOVA for sex and geographic differences. Interaction between these two factors was found for six measurements, suggesting that the degree of sexual dimorphism varies geographically for a few characters (although in no discernible geographic pattern). Sexual dimorphism was demonstrated for 23 of the 36 characters, with differences ranging from 0.00 to 5.88 percent. Females characteristically had a longer rostrum, while males generally had larger skulls overall. In terms of number of characters, the extent of sexual dimorphism demonstrated for skulls of spotted dolphins goes considerably beyond that shown for any other small delphine. A discriminant function involving a combination of 10 characters enabled us to identify correctly the sex of more than 75 percent of the specimens. A procedure for correcting specimen measurements is outlined that would enable an investigator to combine male and female specimens in geographic variation studies. A term (zwitter) is proposed for use when referring to specimens where measurements have been corrected to take into account differences between the se

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00529.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTA 30‐year renaissance in research on fossil marine mammals has brought advances on several fronts and suggests potential directions for future study. Gingerich and Russell have describedPakicetus, the most primitive archaeocete cetacean. Mchedlidze has described a diverse assemblage of late Oligocene/early Miocene cetaceans from the Caucasus and Georgia, S.S.R. Barnes and Fordyce, respectively, have outlined sequences of fossil cetacean assemblages in the northeast and southwest Pacific. Much remains to be done on origin and definition of cetacean suborders, diversification and systematics of families, and relationships among infra‐familial taxa.New material has been recovered of the most primitive desmostylians, and other new specimens, especially ones from Japan studied by Inuzuka and others, give a relatively complete picture of their anatomy. Material now exists for phylogenetic analysis.Domning has proposed a phyletic lineage of the sirenian subfamily Hydro‐damalinae and has outlined patterns of Late Cenozoic manatee evolution. With Morgan and Ray he reviewed Eocene sirenians in the northwest Atlantic. Numerous new specimens are being actively studied in attempts to reassess relationships within the Sirenia.Mitchell and Tedford described the most primitive otariid,Enaliarctos.Repenning and Tedford reviewed the otarioids. The primitive taxa and their origin near or in the amphicynodontine ursids have been identified.The zoogeography of true seals, the phocids, has been analyzed recently by Repenning, Ray and Grigorescu, and by de Muizon. Most taxa are based on a few fragmentary specimens, and much work needs to be done on basic descriptions, interspecific comparisons and phyletic analysis. However, major progress has been made in the southern hemisphere through description of extensive new materials from Peru and South Africa.Many important phylogenetic gaps in the fossil record of marine mammals have been filled recently, and further advances continue at a rapid rate. Studies of zoogeography, functional anatomy and paleoecology, in addition to phylogeny, are coming into their own and promise an exciting series of discoveries in the coming

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00530.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

AbstractThis review focuses on population ecology, with critical accounts of past work and future possibilities in age determination, body growth and condition, estimating abundances, mortality rates and lifespans, reproduction, comparative life histories, population dynamics, population modelling and seals in ecosystems. We suggest ways to reduce errors in age determination and to improve methods of obtaining and presenting growth data. Generalized von Bertalanffy growth equations are promoted as a basis for analysing species differences and intra‐population variation in body lengths. Indices other than blubber thickness may be better for following body condition. Catch‐effort and survival‐index methods of estimating abundances have limited applicability, total counts are only locally useful, and sample counts may only be accurate for scattered, ice‐breeding species. Some new techniques for population indices are promising. Pre‐adult mortality remains difficult to assess. Although not always recognized, adult mortality rates do increase with age, as well described by Gompertz functions. Existing estimates of lifespans are unreliable, and a new approach is outlined. There are methodological problems in estimating ages of maturity.Corpora albicantiashould not be used for back‐extrapolation, and more study is needed of use of teeth annuli as indicators of maturity. Age‐specific proportions of females parous based on reproductive tracts may disagree with proportions recruited in breeding groups, suggesting that the former may often be in error. Allometric relationships among body sizes and life‐history variables need more reliable data, especially since the residuals of such relationships are of greatest interest. Brain size may be a better scalar. Direct evidence of density dependence in population growth of seals is sparse. Early survival has been more widely shown to be density‐dependent, but only among polygynous species where crowding on land may be a byproduct of sexual selection; there is as yet no good evidence of trophic restraints. Evidence of density dependence of ages of maturity is generally unconvincing. Predation, especially by sharks, may be critical in some species. Characteristics of equilibrium populations might profitably be sought in mass remains in middens and historic kill sites. More attention should be paid to the search for density‐independent influences. Supposed impacts of fisheries and pollutions are not wholly convincing. Natural epidemics may keep some populations below resource or space saturation, and some high‐latitude species may show large year‐to‐year variations in recruitment and abundances. Evidence for such density‐independent effects should be sought in residuals of growth curves and in teeth layers. Although surplus yield and production/biomass models have been tried, realistic pinniped models must be completely age‐structured and time‐dependent. Simple models have questionably assumed stationarity to derive life‐history parameters. The best available estimates of density dependence of such parameters give no resolution when extrapolated toward equilibrium, and only limited efforts have been made to introduce stochasticity. Better data, not improved model structures, are needed for better understanding. Recent work has contradicted the assumed voraciousness of seals, but their system impacts and dependencies are not well understood. Extended Lotka‐Volterra equations used to model Antarctic food webs, including seals, are merely heuristic. Fixed seal biomasses enter as top‐down, driving functions in a Bering Sea model, which accordingly cannot be used to analyse or manage their populations. Some Soviet models are tantalizing but ill‐specified. The introduction of harbor seals in well‐chosen lakes might give mote insights into system roles than would more elaborate modelling. We wonder if pinniped ecology is well served by too many enthus

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Book reviewed in this article:GeneralFeaturesof the PaleobiologicalEvolutionof Cetacea, Guram Andreevich Mchedlidze.How TO WRITE and PUBLISH A SCIENTIFIC PAPER. R. A. Day.Reproductionin Whales, Dolphins, and Porpoises. W. F. Perrin, R. L. Brownell, Jr., and D. P. DeMaster (Eds.).Communicationand Behaviorof Whales. R. Payne (Ed.).Echolocationin Whalesand Dolphins. P. E. Purves and G. E. Pilleri.

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0824-0469    

DOI:10.1111/j.1748-7692.1985.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY