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| Author |
Berger, J.; Cunningham, C. |
| Title |
Size-Related Effects on Search Times in North American Grassland Female Ungulates |
Type |
Journal Article |
| Year |
1988 |
Publication |
Ecology |
Abbreviated Journal |
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| Volume |
69 |
Issue |
1 |
Pages |
177-183 |
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no keywords available |
| Abstract |
Feeding and searching (= vigilance) rates arise as a result of many interrelated factors including trophic level, diet, reproductive condition, sex, habitat, body mass, and potential predation pressure. Because of unique ecological conditions in which the confounding influences of all but two of these variables could be minimized, we examined the hypothesis that body mass alone accounts for interspecific differences in search times, and tested it with females of four sympatric native North American ungulates (Bison bison, Antilocapra americana, Ovis canadensis, and Odocoileus hemionus). When the effects of group size were controlled, smaller bodied species were more vigilant (per unit body mass) than larger ones. However, search times (ST) also scaled to body mass, and between 81 and 97% of the ST variance was explained by either exponential or power functions. To remove the potential bias that predators exert different influences on species of varying size, search times of bison in areas with and without their major predator, wolves (Canis lupus), were contrasted; search times did not differ between sites. Our results highlight the importance of designing field research that controls for confounding variables prior to attempting to scale behavioral processes to ecological events. See full-text article at JSTOR |
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Ecological Society of America |
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English |
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0012-9658 |
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Equine Behaviour @ team @ |
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2233 |
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| Author |
Berger, J, |
| Title |
Social systems, resources, and phylogenetic inertia: an experimental test and its limitations |
Type |
Book Chapter |
| Year |
1988 |
Publication |
Ecology of Social Behavior |
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157-186 |
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Academic Press |
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San Diego |
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Slobochikoff, C.N. |
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Ecology of Social Behavior |
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Equine Behaviour @ team @ |
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2234 |
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| Author |
Edwards, P. J.; Hollis, S. |
| Title |
The Distribution of Excreta on New Forest Grassland Used by Cattle, Ponies and Deer |
Type |
Journal Article |
| Year |
1982 |
Publication |
The Journal of Applied Ecology |
Abbreviated Journal |
J Appl Ecol |
| Volume |
19 |
Issue |
3 |
Pages |
953-964 |
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| Abstract |
(1) The distribution of excreta on areas of reseeded grassland in the New Forest used by free-ranging cattle, ponies and fallow deer was shown to be non-random. Distinct latrine areas were recognized where the faeces of all three herbivore species were concentrated, and where the majority of urinations occurred. The mosaic of latrine and non-latrine areas can be detected in aerial photographs in which non-latrine areas appear as light-grey patches set in a matrix of the dark grey latrine areas. During the 3 years of the study the position of the mosaic proved to be relatively stable. (2) The latrine areas were characterized by an uneven sward about 50 mm tall with abundant thistles (Cirsium spp.) and ragwort (Senecio jacobaea). Non-latrine areas had an even and very closely cropped sward between 10 and 20 mm tall. Soil chemical analysis of the two kinds of area revealed significantly higher levels of exchangeable potassium in latrine areas, and on one site significantly higher levels of magnesium and organic matter. No significant differences were detected in soil reaction, nor in phosphorus or calcium levels. (3) Observations of grazing animals revealed a tendency, at all times of year, for ponies to avoid grazing in latrine areas. In winter and spring this tendency was very slight, but from midsummer until late autumn a substantial majority of grazing ponies were to be found in non-latrine areas. In contrast, only 2% of the cattle observations made over a period of 20 months were of animals grazing in non-latrine areas. (4) The standing crop of dung and the rate of dung production on the two kinds of area were monitored for 12 months on one lawn. The amount of pony dung produced on non-latrine areas was only 16.5% of that in latrine areas, while for cattle the corresponding value was 28.7%. It is argued that the observed pattern has been created by selective grazing and eliminatory behaviour of the ponies, and that the excreta of cattle and deer are largely confined to pony latrine areas because these animals are unable to graze the very short herbage of non-latrine areas. |
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Equine Behaviour @ team @ |
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2287 |
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Dellert, B.; Ganslosser, U. |
| Title |
Experimental alterations of food distribution in two species of captive equids (Equus burchelli and E. hemionus kulan) |
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Journal Article |
| Year |
1997 |
Publication |
Ethology Ecology & Evolution (EEE) |
Abbreviated Journal |
Ethol Ecol Evol |
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9 |
Issue |
1 |
Pages |
1-17 |
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n one group each of Plains zebra (six mares, one foal, one subadult) and Asiatic wild asses (seven mares, two foals) at Nuremberg Zoo, food distribution was experimentally changed from clumped (all food in one standard hay rack) to dispersed (one heap per animal). Both groups were characterized by different social structures, which basically remained during the experiment. Plains zebras had an individually structured system of social relationships in a dominance order, wild asses a more egalitarian system without clear-cut rank differences and low frequencies of agonistic interactions. Access to food accordingly was individually (but consistently) different for zebra mares, almost equal for wild ass mares. During the dispersed feeding situation frequencies of agonistic interactions in both species decreased (however non-significantly), individual distances increased but mares also frequently ''visited'' each others' heaps. Feeding time increased for all wild ass mares. Some individuals (in both groups) behaved ''against the trend'' in agonistic behaviour. The results are discussed with regard to food distribution for ungulates in general, and equid social systems. |
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Equine Behaviour @ team @ |
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2292 |
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| Author |
Podos, J. |
| Title |
Early perspectives on the evolution of behavior: Charles Otis Whitman and Oskar Heinroth |
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Journal Article |
| Year |
1964 |
Publication |
Ethology Ecology & Evolution (EEE) |
Abbreviated Journal |
Ethol Ecol Evol |
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6 |
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4 |
Pages |
467-480 |
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Equine Behaviour @ team @ |
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2293 |
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| Author |
Garott, R.A. |
| Title |
Sex Ratios and Differential Survival of Feral Hors |
Type |
Journal Article |
| Year |
1991 |
Publication |
Journal of Animal Ecology |
Abbreviated Journal |
J Anim Ecol |
| Volume |
60 |
Issue |
3 |
Pages |
929-936 |
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(1) Sex and age data were collected on 60 111 feral horses (Equus caballus L.) removed from eighty-nine areas in Nevada, Wyoming, and Oregon between 1976 and 1987. (2) Sex ratios of young seldom differed from parity; however, sex ratios of adults were commonly skewed toward females. No evidence of differential capture probability between adult males and females could be detected; therefore, skewed adult sex ratios were attributed to differential survival. (3) Age-specific trends in sex ratios indicated that the proportion of males steadily decreased from near parity in foals, to lows of 0.61-0.77 in the 4-5-year age-classes. The trend then reversed with males becoming predominant (1.08-1.36) in the > 10 years age-class. (4) Population simulations suggest that survival diffentials of 0.05-0.07, favouring females to 4 years of age, and 0.02-0.04 favouring males in older age-classes were required to mimic observed age-specific sex ratio changes. To obtain the high proportion of males in the > 10-years age-class, onset of senescence also had to be earlier for females. (5) Causes for differential survival in the immature age-classes are uncertain, but may relate to behavioural or metabolic differences between the sexes. Differential survival between adult males and females is attributed to differences in the energetic costs of reproduction and disparity in their reproductive life spans. |
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Equine Behaviour @ team @ |
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2294 |
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| Author |
Eisenberg, J.F.; Kleiman, D.G. |
| Title |
Olfactory Communication in Mammals |
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Journal Article |
| Year |
1972 |
Publication |
Annual Review of Ecology and Systematics |
Abbreviated Journal |
Annu Rev Ecol Systemat |
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3 |
Issue |
1 |
Pages |
1-32 |
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Equine Behaviour @ team @ Eisenberg1972 |
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2316 |
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Kirkpatrick, J.F.; Turner, J.W. |
| Title |
Changes in herd stallions among feral horse bands and the absence of forced copulation and induced abortion |
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Journal Article |
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1991 |
Publication |
Behavioral Ecology and Sociobiology |
Abbreviated Journal |
Behav. Ecol. Sociobiol. |
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29 |
Issue |
3 |
Pages |
217-219 |
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Forced copulation and induced abortion were investigated in a herd of feral horses inhabiting a coastal barrier island. Eight mares were diagnosed pregnant in August and October 1989 by means of urinary and fecal steroid metabolites, prior to documented changes in herd stallions. These mares were observed for harassment and forced copulation by the new stallions and for the presence of foals during the spring and summer of 1990. No incidents of harassment or attempts at forced copulation were witnessed and seven of the eight mares produced foals in 1990. These data indicate that forced copulation and induced abortion are not common events among all feral horse herds and suggest reinvestigation of this hypothesized phenomenon. |
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Equine Behaviour @ team @ |
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2327 |
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Mills, M.G.L.; Shenk, M.G.L. |
| Title |
Predator--Prey Relationships: The Impact of Lion Predation on Wildebeest and Zebra Populations |
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Journal Article |
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1992 |
Publication |
The Journal of Animal Ecology |
Abbreviated Journal |
T. J. Anim. Ecol. |
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61 |
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3 |
Pages |
693-702 |
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1. The role of lion Panthera leo predation in the dynamics of blue wildebeest Connochaetes taurinus and zebra Equus burchelli populations was investigated through simulation models. The data used in the models were from intensive observations over 4 years in the south-east of the Kruger National Park. 2. Population estimates of wildebeest and zebra were made from aerial surveys, sex and age ratios from ground counts. Lion numbers were determined from observations of marked and radio-collared animals. Predation was studied by following lions for continuous periods of up to 336 h. 3. Two models were constructed. Model 1 ascertained the number of killing lions (adult females) that could be supported by each prey population while remaining stable. A single model was constructed for the sedentary wildebeest population. A summer and winter model was constructed for the semi-migratory zebra population. The sensitivity of the parameters in the model was tested by changing their value by 10%. In model 2, the kill age structure for each species was changed to determine the number of killing lions the altered prey selection parameters could support. 4. There was no difference in the vulnerability of either species to predation. Zebra foals (<1 year) were killed more frequently than expected. No selection for sex or by season could be found for either species. 5. Model 1 predicted that the wildebeest population stabilizes with 7.7 killing lions, close to the number in the study area. The winter zebra population stabilizes with 6.8 killing lions and the summer zebra population with 19.4. Manipulation of kill rate followed by adult fecundity rate had the greatest effect on population size of both species. In model 2, wildebeest predation was made selective towards calves and zebra predation was made non-selective for sex and age. With these parameters the wildebeest population stabilizes with 10.7 killing lions and the zebra population with 5.4 in winter and 15.1 in summer. 6. The models suggest that lion predation affected wildebeest more severely than zebra during the study. This was through the way in which lions selected their prey, and because of the sedentary behaviour of the wildebeest, as opposed to the semi-migratory behaviour of the zebra. |
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Equine Behaviour @ team @ |
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2376 |
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Monard, A.-M.; Duncan, P.; Fritz, H.; Feh, C. |
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Variations in the birth sex ratio and neonatal mortality in a natural herd of horses |
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Journal Article |
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1997 |
Publication |
Behavioral Ecology and Sociobiology |
Abbreviated Journal |
Behav. Ecol. Sociobiol. |
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41 |
Issue |
4 |
Pages |
243-249 |
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Variations in birth sex ratios and sex differences in juvenile mortality occur in a number of mammalian species, and in many cases have been linked to resource availability. Most of these biases in offspring sex ratios concern polygynous species with pronounced sexual dimorphism, and where females only are philopatric. Data on species with unusual life-history strategies, such as slight sexual dimorphism or dispersal by both sexes, are of particular interest. In this study of a natural herd of horses (Equus caballus) which experienced an eruptive cycle, and therefore a period of nutritional stress, male offspring had higher neonatal mortality rates in nutritionally poor years than in good ones, whereas “year quality” had no effect on the mortality of female offspring; year quality could therefore be used by mares as predictor of sex-specific offspring survival. We show that the environmental conditions that predicted lower survival of males were negatively related to their production: the birth sex ratio the following year was female-biased; and mares were less likely to produce a son when they had produced a son the preceding year. There was no significant effect of mother's parity, age or rank, or the timing of conception or birth on offspring sex ratios. The mechanism leading to biases in the birth sex ratio could have been the loss of male embryos by mares that did not foal. As there was no evidence for selective abortion of male foetuses in females that did foal the next year, it is not necessary to invoke maternal adjustment, though this remains a possibility. Finally, there was a suggestion that male offspring were more costly to raise than females, since mothers that reared a son in poor years tended to experience an increase in the interbirth interval between their two subsequent offspring. |
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Equine Behaviour @ team @ |
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2388 |
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