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	Author	Scheffer, M.; van Nes, E.H.
	Title	Self-organized similarity, the evolutionary emergence of groups of similar species			Type	Journal Article
	Year	2006	Publication	Proceedings of the National Academy of Sciences of the United States of America	Abbreviated Journal	Proc. Natl. Acad. Sci. U.S.A.
	Volume	103	Issue	16	Pages	6230-6235
	Keywords	Animals; Competitive Behavior; Ecosystem; Evolution; Models, Biological
	Abstract	Ecologists have long been puzzled by the fact that there are so many similar species in nature. Here we show that self-organized clusters of look-a-likes may emerge spontaneously from coevolution of competitors. The explanation is that there are two alternative ways to survive together: being sufficiently different or being sufficiently similar. Using a model based on classical competition theory, we demonstrate a tendency for evolutionary emergence of regularly spaced lumps of similar species along a niche axis. Indeed, such lumpy patterns are commonly observed in size distributions of organisms ranging from algae, zooplankton, and beetles to birds and mammals, and could not be well explained by earlier theory. Our results suggest that these patterns may represent self-constructed niches emerging from competitive interactions. A corollary of our findings is that, whereas in species-poor communities sympatric speciation and invasion of open niches is possible, species-saturated communities may be characterized by convergent evolution and invasion by look-a-likes.
	Address	Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 8080, 6700 DD, Wageningen, The Netherlands. marten.scheffer@wur.nl
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0027-8424	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:16585519			Approved	no
	Call Number	refbase @ user @			Serial	510
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	Author	Mettke-Hofmann, C.; Gwinner, E.
	Title	Long-term memory for a life on the move			Type	Journal Article
	Year	2003	Publication	Proceedings of the National Academy of Sciences of the United States of America	Abbreviated Journal	Proc. Natl. Acad. Sci. U.S.A.
	Volume	100	Issue	10	Pages	5863-5866
	Keywords	Animals; Germany; Israel; Memory/physiology; Models, Biological; Periodicity; Songbirds/physiology
	Abstract	Evidence is accumulating that cognitive abilities are shaped by the specific ecological conditions to which animals are exposed. Long-distance migratory birds may provide a striking example of this. Field observations have shown that, at least in some species, a substantial proportion of individuals return to the same breeding, wintering, and stopover sites in successive years. This observation suggests that migrants have evolved special cognitive abilities that enable them to accomplish these feats. Here we show that memory of a particular feeding site persisted for at least 12 months in a long-distance migrant, whereas a closely related nonmigrant could remember such a site for only 2 weeks. Thus, it seems that the migratory lifestyle has influenced the learning and memorizing capacities of migratory birds. These results build a bridge between field observations suggesting special memorization feats of migratory birds and previous neuroanatomical results from the same two species indicating an increase in relative hippocampal size from the first to the second year of life in the migrant but not in the nonmigrant.
	Address	Max Planck Research Centre for Ornithology, Department of Biological Rhythms and Behaviour, Von-der-Tann-Strasse 7, 82346 Andechs, Germany. mettke-hofmann@erl.ornithol.mpg.de
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0027-8424	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:12719527			Approved	no
	Call Number	refbase @ user @			Serial	511
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	Author	Bergstrom, C.T.; Lachmann, M.
	Title	Signaling among relatives. III. Talk is cheap			Type	Journal Article
	Year	1998	Publication	Proceedings of the National Academy of Sciences of the United States of America	Abbreviated Journal	Proc. Natl. Acad. Sci. U.S.A.
	Volume	95	Issue	9	Pages	5100-5105
	Keywords	Animal Communication; Animals; Costs and Cost Analysis; *Evolution; Interpersonal Relations; Models, Biological
	Abstract	The Sir Philip Sidney game has been used by numerous authors to show how signal cost can facilitate honest signaling among relatives. Here, we demonstrate that, in this game, honest cost-free signals are possible as well, under very general conditions. Moreover, these cost-free signals are better for all participants than the previously explored alternatives. Recent empirical evidence suggests that begging is energetically inexpensive for nestling birds; this finding led some researchers to question the applicability of the costly signaling framework to nestling begging. Our results show that cost-free or inexpensive signals, as observed empirically, fall within the framework of signaling theory.
	Address	Department of Biological Sciences, Stanford University, Stanford, CA 94305, USA. carl@charles.stanford.edu
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0027-8424	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:9560235			Approved	no
	Call Number	refbase @ user @			Serial	561
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	Author	Biro, D.; Sumpter, D.J.T.; Meade, J.; Guilford, T.
	Title	From Compromise to Leadership in Pigeon Homing			Type	Journal Article
	Year	2006	Publication	Current Biology	Abbreviated Journal	Curr Biol
	Volume	16	Issue	21	Pages	2123-2128
	Keywords	Animal Migration; Animals; Columbidae/physiology; Decision Making; Flight, Animal; Homing Behavior; Models, Biological; Orientation; Social Behavior; *Social Dominance
	Abstract	Summary A central problem faced by animals traveling in groups is how navigational decisions by group members are integrated, especially when members cannot assess which individuals are best informed or have conflicting information or interests , , , and . Pigeons are now known to recapitulate faithfully their individually distinct habitual routes home , and , and this provides a novel paradigm for investigating collective decisions during flight under varying levels of interindividual conflict. Using high-precision GPS tracking of pairs of pigeons, we found that if conflict between two birds' directional preferences was small, individuals averaged their routes, whereas if conflict rose over a critical threshold, either the pair split or one of the birds became the leader. Modeling such paired decision-making showed that both outcomes--compromise and leadership--could emerge from the same set of simple behavioral rules. Pairs also navigated more efficiently than did the individuals of which they were composed, even though leadership was not necessarily assumed by the more efficient bird. In the context of mass migration of birds and other animals, our results imply that simple self-organizing rules can produce behaviors that improve accuracy in decision-making and thus benefit individuals traveling in groups , and .
	Address	Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom. daro.biro@zoo.ox.ac.uk
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	Englisch	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0960-9822	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:17084696			Approved	no
	Call Number				Serial	2026
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	Author	Cameron, E.Z.
	Title	Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism			Type	Journal Article
	Year	2004	Publication	Proceedings. Biological sciences / The Royal Society	Abbreviated Journal	Proc Biol Sci
	Volume	271	Issue	1549	Pages	1723-1728
	Keywords	Age Factors; Animals; Body Constitution; Evolution; Female; Glucose/metabolism/physiology; Litter Size; Male; Mammals/physiology; Models, Biological; Reproduction/physiology; Seasons; Sex Factors; Sex Ratio; Time Factors
	Abstract	Evolutionary theory predicts that mothers of different condition should adjust the birth sex ratio of their offspring in relation to future reproductive benefits. Published studies addressing variation in mammalian sex ratios have produced surprisingly contradictory results. Explaining the source of such variation has been a challenge for sex-ratio theory, not least because no mechanism for sex-ratio adjustment is known. I conducted a meta-analysis of previous mammalian sex-ratio studies to determine if there are any overall patterns in sex-ratio variation. The contradictory nature of previous results was confirmed. However, studies that investigated indices of condition around conception show almost unanimous support for the prediction that mothers in good condition bias their litters towards sons. Recent research on the role of glucose in reproductive functioning have shown that excess glucose favours the development of male blastocysts, providing a potential mechanism for sex-ratio variation in relation to maternal condition around conception. Furthermore, many of the conflicting results from studies on sex-ratio adjustment would be explained if glucose levels in utero during early cell division contributed to the determination of offspring sex ratios.
	Address	Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0962-8452	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:15306293			Approved	no
	Call Number	refbase @ user @			Serial	413
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	Author	Brilot, B.O.; Johnstone, R.A.
	Title	The limits to cost-free signalling of need between relatives			Type	Journal Article
	Year	2003	Publication	Proceedings. Biological sciences / The Royal Society	Abbreviated Journal	Proc Biol Sci
	Volume	270	Issue	1519	Pages	1055-1060
	Keywords	Animal Communication; Animals; Birds/physiology; Models, Biological; Social Behavior
	Abstract	Theoretical models have demonstrated the possibility of stable cost-free signalling of need between relatives. The stability of these cost-free equilibria depends on the indirect fitness cost of cheating and deceiving a donor into giving away resources. We show that this stability is highly sensitive to the distribution of need among signallers and receivers. In particular, cost-free signalling is likely to prove stable only if there is very large variation in need (such that the least-needy individuals stand to gain much less than the most-needy individuals from additional resources). We discuss whether these conditions are likely to be found in altricial avian breeding systems--the most intensively studied instance of signalling of need between relatives. We suggest that cost-free signalling is more likely to prove stable and will provide parents with more information during the earlier phases of chick growth, when parents can more easily meet the demands of a brood (and chicks are more likely to reach satiation). Later, informative yet cost-free signalling is unlikely to persist.
	Address	Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK. bob21@cam.ac.uk
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0962-8452	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:12803895			Approved	no
	Call Number	refbase @ user @			Serial	558
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	Author	Santamaria, S.; Bobbert, M.E.; Back, W.; Barneveld, A.; van Weeren, P.R.
	Title	Variation in free jumping technique within and among horses with little experience in show jumping			Type	Journal Article
	Year	2004	Publication	American Journal of Veterinary Research	Abbreviated Journal	Am J Vet Res
	Volume	65	Issue	7	Pages	938-944
	Keywords	Acceleration; Analysis of Variance; Animals; Biomechanics; Forelimb/physiology; Gait/physiology; Hindlimb/physiology; Horses/physiology; Locomotion/physiology; Models, Biological; Video Recording
	Abstract	OBJECTIVE: To quantify variation in the jumping technique within and among young horses with little jumping experience, establish relationships between kinetic and kinematic variables, and identify a limited set of variables characteristic for detecting differences in jumping performance among horses. ANIMALS: Fifteen 4-year-old Dutch Warmblood horses. PROCEDURE: The horses were raised under standardized conditions and trained in accordance with a fixed protocol for a short period. Subsequently, horses were analyzed kinematically during free jumping over a fence with a height of 1.05 m. RESULTS: Within-horse variation in all variables that quantified jumping technique was smaller than variation among horses. However, some horses had less variation than others. Height of the center of gravity (CG) at the apex of the jump ranged from 1.80 to 2.01 m among horses; this variation could be explained by the variation in vertical velocity of the CG at takeoff (r, 0.78). Horses that had higher vertical velocity at takeoff left the ground and landed again farther from the fence, had shorter push-off phases for the forelimbs and hind limbs, and generated greater vertical acceleration of the CG primarily during the hind limb push-off. However, all horses cleared the fence successfully, independent of jumping technique. CONCLUSIONS AND CLINICAL RELEVANCE: Each horse had its own jumping technique. Differences among techniques were characterized by variations in the vertical velocity of the CG at takeoff. It must be determined whether jumping performance later in life can be predicted from observing free jumps of young horses.
	Address	Department of Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 12, NL-3584 CM Utrecht, The Netherlands
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0002-9645	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:15281652			Approved	no
	Call Number	Equine Behaviour @ team @			Serial	3772
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	Author	Johnson, D.D.P.; Stopka, P.; Knights, S.
	Title	Sociology: The puzzle of human cooperation			Type	Journal Article
	Year	2003	Publication	Nature	Abbreviated Journal	Nature
	Volume	421	Issue	6926	Pages	911-2; discussion 912
	Keywords	Altruism; Cooperative Behavior; Evolution; Humans; Models, Biological; Punishment; Reward; Risk
	Abstract
	Address	Olin Institute for Strategic Studies, Harvard University, Cambridge, Massachusetts 02138, USA. dominic@post.harvard.edu
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0028-0836	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:12606989			Approved	no
	Call Number	refbase @ user @			Serial	467
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	Author	Wilson, A.M.; McGuigan, M.P.; Su, A.; van Den Bogert, A.J.
	Title	Horses damp the spring in their step			Type	Journal Article
	Year	2001	Publication	Nature	Abbreviated Journal	Nature
	Volume	414	Issue	6866	Pages	895-899
	Keywords	Animals; Biomechanics; Elasticity; Forelimb; Gait; Horses/anatomy & histology/physiology; Leg Bones/physiology; Locomotion; Models, Biological; Muscle Fibers/physiology; Muscle, Skeletal/anatomy & histology/physiology; Tendons/anatomy & histology/physiology; Vibration
	Abstract	The muscular work of galloping in horses is halved by storing and returning elastic strain energy in spring-like muscle-tendon units.These make the legs act like a child's pogo stick that is tuned to stretch and recoil at 2.5 strides per second. This mechanism is optimized by unique musculoskeletal adaptations: the digital flexor muscles have extremely short fibres and significant passive properties, whereas the tendons are very long and span several joints. Length change occurs by a stretching of the spring-like digital flexor tendons rather than through energetically expensive length changes in the muscle. Despite being apparently redundant for such a mechanism, the muscle fibres in the digital flexors are well developed. Here we show that the mechanical arrangement of the elastic leg permits it to vibrate at a higher frequency of 30-40 Hz that could cause fatigue damage to tendon and bone. Furthermore, we show that the digital flexor muscles have minimal ability to contribute to or regulate significantly the 2.5-Hz cycle of movement, but are ideally arranged to damp these high-frequency oscillations in the limb.
	Address	Department of Veterinary Basic Sciences, The Royal Veterinary College, Hatfield, Herts AL9 7TA, UK. awilson@rvc.ac.uk
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0028-0836	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:11780059			Approved	no
	Call Number	Equine Behaviour @ team @			Serial	2300
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	Author	Dubois, F.; Giraldeau, L.-A.
	Title	The forager's dilemma: food sharing and food defense as risk-sensitive foraging options			Type	Journal Article
	Year	2003	Publication	The American Naturalist	Abbreviated Journal	Am Nat
	Volume	162	Issue	6	Pages	768-779
	Keywords	Animals; Competitive Behavior/physiology; Environment; Feeding Behavior/physiology; Game Theory; *Models, Biological; Population Density; Population Dynamics
	Abstract	Although many variants of the hawk-dove game predict the frequency at which group foraging animals should compete aggressively, none of them can explain why a large number of group foraging animals share food clumps without any overt aggression. One reason for this shortcoming is that hawk-dove games typically consider only a single contest, while most group foraging situations involve opponents that interact repeatedly over discovered food clumps. The present iterated hawk-dove game predicts that in situations that are analogous to a prisoner's dilemma, animals should share the resources without aggression, provided that the number of simultaneously available food clumps is sufficiently large and the number of competitors is relatively small. However, given that the expected gain of an aggressive animal is more variable than the gain expected by nonaggressive individuals, the predicted effect of the number of food items in a clump-clump richness-depends on whether only the mean or both the mean and variability associated with payoffs are considered. More precisely, the deterministic game predicts that aggression should increase with clump richness, whereas the stochastic risk-sensitive game predicts that the frequency of encounters resulting in aggression should peak at intermediate clump richnesses or decrease with increasing clump richness if animals show sensitivity to the variance or coefficient of variation, respectively.
	Address	Departement des Sciences Biologiques, Universite du Quebec a Montreal, Case postale 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada. fdubois@u-bourgogne.fr
	Corporate Author				Thesis
	Publisher		Place of Publication		Editor
	Language	English	Summary Language		Original Title
	Series Editor		Series Title		Abbreviated Series Title
	Series Volume		Series Issue		Edition
	ISSN	0003-0147	ISBN		Medium
	Area		Expedition		Conference
	Notes	PMID:14737714			Approved	no
	Call Number				Serial	2132
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