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Cameron, E.Z. |
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Title  |
Facultative adjustment of mammalian sex ratios in support of the Trivers-Willard hypothesis: evidence for a mechanism |
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Year |
2004 |
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Proceedings. Biological sciences / The Royal Society |
Abbreviated Journal |
Proc Biol Sci |
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271 |
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1549 |
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1723-1728 |
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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 |
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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. |
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Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa. ezcameron@zoology.up.ac.za |
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0962-8452 |
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PMID:15306293 |
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refbase @ user @ |
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413 |
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Hoskin, S.O.; Gee, E.K. |
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Title |
Feeding value of pastures for horses |
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2004 |
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New Zealand Veterinary Journal |
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N Z Vet J |
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52 |
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6 |
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332-341 |
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The feeding value of fresh pasture grazed in situ is determined by animal performance or productivity and could be relatively easily established for growing and lactating horses. Despite this, there is a lack of published information on the relative feeding value of different pastures and forages grazed by horses in New Zealand and the world. In addition, for adult breeding or non-breeding and young or adult sport or performance horses, the definition of feeding value and its determination remain problematic. Limited information suggests that the feeding value of perennial ryegrass-based pasture in New Zealand for young growing horses is high, and growth rates for Thoroughbred horses fed solely on pasture in New Zealand are similar to those reported from the Northern Hemisphere where grain-based supplements are fed in addition to pasture or other forages. Attempts to assess the ability of fresh pastures to meet the nutrient requirements of horses are hampered by problems associated with determination of feed intake by grazing horses and lack of knowledge of the digestibility and utilisation of digested nutrients, including the relative bioavailability of macro- and micro-minerals in pasture. A further challenge for future research is to determine the effect of herbage allowance and grazing behaviour, including pasture species preferences, on voluntary feed intake by grazing horses. Grazing pasture has benefits for equine health and well-being including reduced risk of some nutrition-related disorders and reduced prevalence of stereotypic behaviour. Pastured horses have greater freedom for expression of natural behaviours including social interaction and exercise. However, grazing pasture is also associated with animal health problems, particularly parasitism and diseases related to pasture-associated toxins. |
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Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand |
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0048-0169 |
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PMID:15768133 |
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1893 |
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Hois, C. |
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Feldstudie zur Gewichtsentwicklung und Gewichtsschätzung beim wachsenden Pferd |
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2004 |
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Ph.D. thesis |
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Tierärztlichen Fakultät der Ludwig-Maximilians-Universität München |
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Equine Behaviour @ team @ |
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5204 |
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Linklater, W.L.; Cameron, E.Z.; Minot, E.O.; Stafford, K.J. |
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Feral horse demography and population growth in the Kaimanawa Ranges, New Zealand |
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Journal Article |
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Year |
2004 |
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Wildl. Res. |
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31 |
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2 |
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119-128 |
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Although feral horses are a common management problem in numerous countries, detailed and long-term demographic studies are rare. We measured the age and sex structure, and pregnancy, birth and death rates in a population of 413 feral horses in New Zealand during 1994–98 and used them to construct a model simulating population growth. Survivorship increased with age (0–1 years old = 86.8%, 1–2 = 92.3%, 2–4 = 92.4%, ≥? 4 years old = females 94%, males 97% per annum). Birth sex ratio parity, a slight female bias in the adult sex ratio (92 males per 100 females) and higher adult male survivorship indicated lower average survivorship for young males than females that was not detectable in mortality statistics. Pregnancy and foaling rates for mares ≥? 2 years old averaged 79 and 49%, respectively. Foaling rates increased as mares matured (2–3-year-old mares = 1.9%, 3–4 = 20.0%, 4–5 = 42.1%, ≥? 5 = 61.5% per annum). Young mares had higher rates of foetal and neonatal mortality (95% of pregnancies failed and/or were lost as neonatal foals in 2–3-year-old mares, 70.6% in 3–4, 43.2% in 4–5, and 31% in mares ≥? 5 years old). Population growth was 9.6% per annum (9.5–9.8, 95% CI) without human-induced mortalities (i.e. r = 0.092). Our model, standardised aerial counts, and historical estimates of annual reproduction suggest that the historical sequence of counts since 1979 has overestimated growth by ~50% probably because of improvements in count effort and technique.</p> |
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Equine Behaviour @ team @ |
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3695 |
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Landman, M.A.A.M.; de Blaauw, J.A.; van Weeren, P.R.; Hofland, L.J. |
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Title |
Field study of the prevalence of lameness in horses with back problems |
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Journal Article |
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2004 |
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The Veterinary Record |
Abbreviated Journal |
Vet. Rec. |
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155 |
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6 |
Pages |
165-168 |
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Animals; Back Pain/epidemiology/*veterinary; Case-Control Studies; Horse Diseases/*epidemiology/etiology; Horses; Lameness, Animal/epidemiology; Netherlands/epidemiology; Osteoarthritis/epidemiology/*veterinary; Prevalence; Records/veterinary; Retrospective Studies |
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A population of 805 horses (70 per cent dressage, 20 per cent show jumpers and 10 per cent trotters) with orthopaedic problems was examined for signs of lameness and back problems, irrespective of their original complaints. In the horses with a back problem the prevalence of lameness was 74 per cent, and back problems were diagnosed in 32 per cent of the lame horses. These percentages were significantly higher than those recorded in a control population of 399 horses, of which 20 per cent were lame and 12 per cent had back problems. In the group of horses with orthopaedic problems there was a strong association between lameness and back problems and, in particular, there was a high prevalence of lameness among the horses with back problems. |
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Bodegraven Equine Clinic, Zuidzijde 63, NL-2411 RT Bodegraven, The Netherlands |
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0042-4900 |
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PMID:15357376 |
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Equine Behaviour @ team @ |
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3717 |
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Friedrich, A.M.; Clement, T.S.; Zentall, T.R. |
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Title |
Functional equivalence in pigeons involving a four-member class |
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Journal Article |
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2004 |
Publication |
Behavioural processes |
Abbreviated Journal |
Behav. Process. |
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67 |
Issue |
3 |
Pages |
395-403 |
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Animals; *Association Learning; *Behavior, Animal; *Cognition; Columbidae; *Concept Formation |
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Research suggests that animals are capable of forming functional equivalence relations or stimulus classes of the kind usually demonstrated by humans (e.g., the class defined by an object and the word for that object). In pigeons, such functional equivalences are typically established using many-to-one matching-to-sample in which two samples are associated with one comparison stimulus and two different samples are associated with the other. Evidence for the establishment of functional equivalences between samples associated with the same comparison comes from transfer tests. In Experiment 1, we found that pigeons can form a single class consisting of four members (many-to-one matching) when the alternative class has only one member (one-to-one matching). In Experiment 2, we ruled out the possibility that the pigeons acquired the hybrid one-to-one/many-to-one task by developing a single-code/default coding strategy as earlier research suggested that it might. Thus, pigeons can develop a functional class consisting of as many as four members, with the alternative class consisting of a single member. |
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Department of Psychology, University of Kentucky, Lexington, KY 40506-0044, USA |
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0376-6357 |
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PMID:15518989 |
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refbase @ user @ |
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228 |
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Author |
Itakura, S. |
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Title |
Gaze Following and Joint Visual Attention in Nonhuman Animals |
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2004 |
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Japanese Psychological Research |
Abbreviated Journal |
Jpn. Psychol. Res. |
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3 |
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216-226 |
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gaze-following; joint visual attention; theory of mind; nonhuman animal |
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n this paper, studies of gaze-following and joint visual attention in nonhuman animals are reviewed from the theoretical perspective of Emery (2000). There are many studies of gaze-following and joint visual attention in nonhuman primates. The reports concern not only adult individuals but also the development of these abilities. Studies to date suggest that monkeys and apes are able to follow the gaze of others, but only apes can understand the seeing-knowing relationship with regards to conspecifics in competitive situations. Also, there have recently been some reports of ability to follow the gaze of humans in domestic animals, such as dogs or horses, interacting with humans. These domestic animals are considered to have acquired this ability during their long history of selective breeding by humans. However, we need to clarify social gaze parameters in various species to improve our knowledge of the evolution of how we process others gazing, attention, and mental states. |
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545 |
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Weber-Mzell, D.; Kotanko, P.; Hauer, A.C.; Goriup, U.; Haas, J.; Lanner, N.; Erwa, W.; Ahmaida, I.A.; Haitchi-Petnehazy, S.; Stenzel, M.; Lanzer, G.; Deutsch, J. |
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Gender, age and seasonal effects on IgA deficiency: a study of 7293 Caucasians |
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Journal Article |
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2004 |
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European Journal of Clinical Investigation |
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34 |
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3 |
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224-228 |
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Age- and gender-related variability; immunoglobulin A; seasonal variability; serum IgA deficiency |
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Background The frequency of serum IgA deficiency (SIgAD) differs between populations. We examined the prevalence of SIgAD in healthy Caucasians. Materials and methods Serum immunoglobulin A (SIgA) was measured in 7293 volunteers (2264 women, 5029 men) aged 30 ± 14·2 years (mean ± SD; range: 12–66). Serum immunoglobulin A and subnormal SIgA levels were defined by a SIgA level < 0·07 g L-1, and between 0·07 and 0·7 g L-1, respectively. Means were compared by analysis of variance (anova) and analysis of covariance (ancova); frequencies by the χ2 test. Results Fifteen subjects (0·21%; one woman, 14 men) had SIgAD. Subnormal SIgA levels were found in 155 persons (2·13%): 21 females (0·93% of the females) and 134 males (2·66% of the males; difference: 1·74%; 95% CI: 1·12–2·33%; P < 0·001). Males were more likely to have subnormal SIgA levels or SIgAD (odds ratio 3·09, 95% CI: 1·97–4·85). The prevalence of SIgAD and subnormal SIgA was lowest in winter (χ2 = 14·8; P = 0·002; 3 d.f.; and χ2 = 43·2; P < 0·001; 3 d.f., respectively). Serum immunoglobulin A concentrations were significantly higher during winter. Serum immunoglobulin A levels increased with age on average by 0·2 ± 0·06 g L-1 per decade of life (P < 0·001). Taking into account the influence of age, SIgA concentration was lower in females as compared with males. Conclusion The prevalence of SIgAD and subnormal SIgA levels is increased in males. There exists a significant influence of gender, age and seasons on SIgA levels. |
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Blackwell Science Ltd |
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1365-2362 |
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Equine Behaviour @ team @ |
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6127 |
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Aberle, K.S.; Hamann, H.; Drögemüller, C.; Distl, O. |
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Genetic diversity in German draught horse breeds compared with a group of primitive, riding and wild horses by means of microsatellite DNA markers |
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2004 |
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Animal Genetics |
Abbreviated Journal |
Anim. Gen. |
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35 |
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4 |
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270-277 |
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diversity; endangered breeds; genetic variation; horse; microsatellite |
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Summary We compared the genetic diversity and distance among six German draught horse breeds to wild (Przewalski's Horse), primitive (Icelandic Horse, Sorraia Horse, Exmoor Pony) or riding horse breeds (Hanoverian Warmblood, Arabian) by means of genotypic information from 30 microsatellite loci. The draught horse breeds included the South German Coldblood, Rhenish German Draught Horse, Mecklenburg Coldblood, Saxon Thuringa Coldblood, Black Forest Horse and Schleswig Draught Horse. Despite large differences in population sizes, the average observed heterozygosity (Ho) differed little among the heavy horse breeds (0.64�0.71), but was considerably lower than in the Hanoverian Warmblood or Icelandic Horse population. The mean number of alleles (NA) decreased more markedly with declining population sizes of German draught horse breeds (5.2�6.3) but did not reach the values of Hanoverian Warmblood (NA = 6.7). The coefficient of differentiation among the heavy horse breeds showed 11.6% of the diversity between the heavy horse breeds, as opposed to 21.2% between the other horse populations. The differentiation test revealed highly significant genetic differences among all draught horse breeds except the Mecklenburg and Saxon Thuringa Coldbloods. The Schleswig Draught Horse was the most distinct draught horse breed. In conclusion, the study demonstrated a clear distinction among the German draught horse breeds and even among breeds with a very short history of divergence like Rhenish German Draught Horse and its East German subpopulations Mecklenburg and Saxon Thuringa Coldblood. |
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Blackwell Science Ltd |
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1365-2052 |
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Equine Behaviour @ team @ |
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5184 |
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James, R.; Bennett, P.G.; Krause, J. |
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Geometry for mutualistic and selfish herds: the limited domain of danger |
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2004 |
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Journal of Theoretical Biology |
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J. Theor. Biol. |
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228 |
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1 |
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107-113 |
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Aggregation; Selfish herd; Limited domains |
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We present a two-dimensional individual-based model of aggregation behaviour in animals by introducing the concept of a “limited domain of danger”, which represents either a limited detection range or a limited attack range of predators. The limited domain of danger provides a suitable framework for the analysis of individual movement rules under real-life conditions because it takes into account the predator's prey detection and capture abilities. For the first time, a single geometrical construct can be used to analyse the predation risk of both peripheral and central individuals in a group. Furthermore, our model provides a conceptual framework that can be equally applied to aggregation behaviour and refuge use and thus presents a conceptual advance on current theory that treats these antipredator behaviours separately. An analysis of individual movement rules using limited domains of danger showed that the time minimization strategy outcompetes the nearest neighbour strategy proposed by Hamilton's (J. Theor. Biol. 31 (1971) 295) selfish herd model, whereas a random strategy confers no benefit and can even be disadvantageous. The superior performance of the time minimization strategy highlights the importance of taking biological constraints, such as an animal's orientation relative to its neighbours, into account when searching for efficient movement rules underlying the aggregation process. |
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refbase @ user @ |
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