The China Productivity Project: Results and conclusions

Experiments were conducted to determine what factors cause variation in individual work output (economic productivity). Forty-five young male Chinese cycle haulers from Beijing were assessed for physiological work capacity, size and body composition, health, nutritional status, cold resistance, household social environment, and motivation. Experiments were conducted in the laboratory as well as under actual working conditions; ethnographic observations were made in the household and on the job during the Beijing winter of 1992. Overall work motivation correlated to actual monthly distance/load measures of productivity the most strongly (r = 0.518), followed by physiological capacity estimated by heart rate:speed ratio during field experiments (r = −0.473). Alcohol consumption (a negative factor), household health, and carbohydrate intake were all moderate predictors. Maximum oxygen uptake showed lower correlation (r = 0.261), and among anthropometric values only relatively long lower legs were predictive (r = 0.298). Since many of these variable categories were relatively independent of each other, multiple regression analysis showed that together they explained 61.6% of the work output variance. Simultaneous prediction by FASEM (LISREL) is also very strong. Am J Phys Anthropol 103:295–313, 1997. © 1997 Wiley-Liss, Inc.     

Heart rate and burrowing behavior in the mussel Anodontites trapesialis (Bivalvia: Mycetopodidae) from lotic and lentic sites

Burrowing rate index, diurnal variations in heart rate and heart rate alterations associated with behavioral patterns were studied in Anodontites trapesialis from the Pardo River (PR) and the Galo Bravo Dam (GBD). In both populations the pattern immobile/buried was associated with the lowest (basal) values of heart rate, which increase significantly during burrowing remaining steady in its phases I and II and at the first 10 min of phase III. A decrease in the frequency of digging cycles was significantly correlated with the gradual decrease in heart rate during the phase III of burrowing. Nevertheless, mussels from PR burrow faster than those of GBD and possess higher values of basal heart rate which present a diurnal variation with the higher values occurring during the light phase. Yet, the basal heart rate in mussels from GBD remained stable over the course of 24 h. Also, the increase in heart rate associated with burrowing was higher in mussels from PR and compatible with the highest burrowing index previously detected. Since mussels possess a plastic phenotype it is probable that the cited functional differences are phenotypic adaptations, but we cannot exclude the possibility of these adaptations being genotypic in nature.     

A study on optimum load for physical work.

Five healthy men were chosen as experimental subjects and were divided into groups at random. The subjects walked with a load in a shoulder-waist-back manner on the treadmill at the speed of 5, 7 and 9 km h-1. The parameters measured were as follows: oxygen expenditure, energy consumption, heart rate and self appraisal. Based on the experimental results and analysis of multiple regression, the authors suggested that physical loading should not exceed 25 kg (i.e. roughly equal to 39% of average body weight of male Chinese), when the walking speed was at 5 km h-1. The suitable loading at physical work would be 20 kg (i.e. equal to 31% of the average body weight of male Chinese).     

Speed and Cardiac Recovery Variables Predict the Probability of Elimination in Equine Endurance Events

Nearly 50% of the horses participating in endurance events are eliminated at a veterinary examination (a vet gate). Detecting unfit horses before a health problem occurs and treatment is required is a challenge for veterinarians but is essential for improving equine welfare. We hypothesized that it would be possible to detect unfit horses earlier in the event by measuring heart rate recovery variables. Hence, the objective of the present study was to compute logistic regressions of heart rate, cardiac recovery time and average speed data recorded at the previous vet gate (n-1) and thus predict the probability of elimination during successive phases (n and following) in endurance events. Speed and heart rate data were extracted from an electronic database of endurance events (80–160 km in length) organized in four countries. Overall, 39% of the horses that started an event were eliminated—mostly due to lameness (64%) or metabolic disorders (15%). For each vet gate, logistic regressions of explanatory variables (average speed, cardiac recovery time and heart rate measured at the previous vet gate) and categorical variables (age and/or event distance) were computed to estimate the probability of elimination. The predictive logistic regressions for vet gates 2 to 5 correctly classified between 62% and 86% of the eliminated horses. The robustness of these results was confirmed by high areas under the receiving operating characteristic curves (0.68–0.84). Overall, a horse has a 70% chance of being eliminated at the next gate if its cardiac recovery time is longer than 11 min at vet gate 1 or 2, or longer than 13 min at vet gates 3 or 4. Heart rate recovery and average speed variables measured at the previous vet gate(s) enabled us to predict elimination at the following vet gate. These variables should be checked at each veterinary examination, in order to detect unfit horses as early as possible. Our predictive method may help to improve equine welfare and ethical considerations in endurance events.     

High-precision satellite positioning system as a new tool to study the biomechanics of human locomotion

New Global Positioning System (GPS) receivers allow now to measure a location on earth at high frequency (5 Hz) with a centimetric precision using phase differential positioning method. We studied whether such technique was accurate enough to retrieve basic parameters of human locomotion. Eight subjects walked on an athletics track at four different imposed step frequencies (70–130 steps/min) plus a run at free pace. Differential carrier phase localization between a fixed base station and the mobile antenna mounted on the walking person was calculated. In parallel, a triaxial accelerometer, attached to the low back, recorded body accelerations. The different parameters were averaged for 150 consecutive steps of each run for each subject (total of 6000 steps analyzed). We observed a perfect correlation between average step duration measured by accelerometer and by GPS (r=0.9998, N=40). Two important parameters for the calculation of the external work of walking were also analyzed, namely the vertical lift of the trunk and the velocity variation per step. For an average walking speed of 4.0 km/h, average vertical lift and velocity variation were, respectively, 4.8 cm and 0.60 km/h. The average intra-individual step-to-step variability at a constant speed, which includes GPS errors and the biological gait style variation, were found to be 24.5% (coefficient of variation) for vertical lift and 44.5% for velocity variation. It is concluded that GPS technique can provide useful biomechanical parameters for the analysis of an unlimited number of strides in an unconstrained free-living environment.     

Individual behavioral variation in predator–prey models

The role of individual behavioral variation in community dynamics was studied. Behavioral variation in this study does not refer to differences in average responses (e.g., average response between presence and absence of antipredator behavior). Rather it refers to the variation around the average response that is not explained by trivial experimental treatments. First, the effect of behavioral variation was examined based on Jensen’s inequality. In cases of commonly used modeling framework with type II functional response, neglecting behavioral variation (a component of encounter rate) causes overestimation of predation effects. The effect of this bias on community processes was examined by incorporating the behavioral variation in a commonly used consumer-resource model (Rosenzweig–MacArthur model). How such a consideration affects a model prediction (paradox of enrichment) was examined. The inclusion of behavioral variation can both quantitatively and qualitatively alter the model characteristics. Behavioral variation can substantially increase the stability of the community with respect to enrichment.     

Individual differences in the perception of probability

In recent studies of humans estimating non-stationary probabilities, estimates appear to be unbiased on average, across the full range of probability values to be estimated. This finding is surprising given that experiments measuring probability estimation in other contexts have often identified conservatism: individuals tend to overestimate low probability events and underestimate high probability events. In other contexts, repulsive biases have also been documented, with individuals producing judgments that tend toward extreme values instead. Using extensive data from a probability estimation task that produces unbiased performance on average, we find substantial biases at the individual level; we document the coexistence of both conservative and repulsive biases in the same experimental context. Individual biases persist despite extensive experience with the task, and are also correlated with other behavioral differences, such as individual variation in response speed and adjustment rates. We conclude that the rich computational demands of our task give rise to a variety of behavioral patterns, and that the apparent unbiasedness of the pooled data is an artifact of the aggregation of heterogeneous biases.     

Mate Preference for Novel Phenotypes: A Fresh Face Matters

Conspicuous polymorphism in sexually selected traits is usually attributed to processes such as frequency‐dependent selection that can maintain genetic variation. Recent evidence indicates that dramatic variation of male coloration in guppies (Poecilia reticulata) is promoted by a form of frequency‐dependent selection in which males bearing rare or novel color patterns achieve higher mating success than males bearing common patterns. Active female preference for unfamiliar or rare color patterns has been implicated in generating this rare‐phenotype advantage, but the behavioral processes responsible for the preference remain unclear. To determine whether familiarity that is developed over a very short timescale can lead to a rare‐male mating advantage, we measured female response to courtship by males with color patterns that were the same as or different from that of the previous male to court. Females showed two types of short‐term preference variation in this experiment. On the first trial day, females shifted their preferences on a timescale of minutes, showing strong preference for males bearing a color pattern different from that of the immediately previous male to court. Twenty‐four hours later, females were less responsive to male courtship overall, and there was no difference in females’ response to different‐ and same‐morph males. Females also preferred males with more orange coloration on both trial days, but this color preference was independent of the preference for ‘different’ color patterns. These data suggest that the behavioral process underlying rare‐male advantage in guppies is that females prefer males bearing unfamiliar color patterns and that familiarity is determined over a very short timescale.     

Changes in antepartum heart rate patterns with progressive deterioration of the fetal condition

In this paper changes in antepartum fetal heart rate (FHR) patterns are described, that occur with progressive deterioration of the fetal condition. The data on the relationship between heart rate patterns and fetal blood gas and pH values are reviewed. A possible rank ordering is presented in which changes in FHR pattern, body movements and blood flow velocity wave form patterns occur with progressive deterioration of the fetal condition.It is concluded that in small-for-date fetuses changes in heart rate and movement patterns are rather late signs of impairment, coinciding with fetal hypoxaemia. In general, heart rate variation falls below the norm at the same time as decelerations occur; there are, however, large inter-fetal differences. In general, abnormal Doppler velocity wave form patterns precede the occurrence of heart rate decelerations. Their impact on the timing of delivery is, however, still uncertain. The advantages of a numerical analysis of FHR patterns include identification of fetuses with low FHR variation, precision of the actual fetal condition and (at early gestation) longitudinal follow-up of fetuses with abnormal heart rate patterns.     

Length of activity season drives geographic variation in body size of a widely distributed lizard

Understanding the factors that drive geographic variation in life history is an important challenge in evolutionary ecology. Here, we analyze what predicts geographic variation in life‐history traits of the common lizard, Zootoca vivipara, which has the globally largest distribution range of all terrestrial reptile species. Variation in body size was predicted by differences in the length of activity season, while we found no effects of environmental temperature per se. Females experiencing relatively short activity season mature at a larger size and remain larger on average than females in populations with relatively long activity seasons. Interpopulation variation in fecundity was largely explained by mean body size of females and reproductive mode, with viviparous populations having larger clutch size than oviparous populations. Finally, body size‐fecundity relationship differs between viviparous and oviparous populations, with relatively lower reproductive investment for a given body size in oviparous populations. While the phylogenetic signal was weak overall, the patterns of variation showed spatial effects, perhaps reflecting genetic divergence or geographic variation in additional biotic and abiotic factors. Our findings emphasize that time constraints imposed by the environment rather than ambient temperature play a major role in shaping life histories in the common lizard. This might be attributed to the fact that lizards can attain their preferred body temperature via behavioral thermoregulation across different thermal environments. Length of activity season, defining the maximum time available for lizards to maintain optimal performance, is thus the main environmental factor constraining growth rate and annual rates of mortality. Our results suggest that this factor may partly explain variation in the extent to which different taxa follow ecogeographic rules.     

Visual bottle inspection performance in highly paced belt-conveyor systems

The relation between visual work performance and a few variables with immediate effects, i.e, lighting, work speed, work spell, etc. was studied. At the same time, some physiological and behavioral variations obtained in the study were also discussed. Through experiments and surveys, the optimum conditions were found for each variable. Work performance, however, is affected in such a subtle, interactive and dynamic manner that the working conditions are to be adjusted by taking into account not only these variables having immediate effects but also those indirectly relating ones meeting real needs in the practical working fields. Improvement of some physical working conditions, such as lighting, produces only a transitory increase of performance which is very unstable unless other determinants of performance are simultaneously managed in a proper manner. The same applied to arrangement of the optimum work speed and work spell for highly paced visual inspection, variations in rejection rate and in physiological functions interacting with individual and other determinants. In order to maximize understanding of the integrated and synthesized manner of determinants, it is emphasized that work performance must be pursued in a considerably comprehensive framework from a long-term perspective.     

Study of the hunting behavior of windhounds by means of GPS tracking: Quantitative characteristics of prey search and coursing

The use of GPS tracking (update rate 1 s) in a natural experiment has made it possible to analyze for the first time the behavior of windhounds dogs in searching and coursing a brown hare as a model of predator-prey interaction. The time course of changes in the coordinates, speed, and direction of movement have been described to characterize quantitatively the hunting behavior of windhounds. Ordered chains of events have been revealed in the seemingly stochastic pattern of field observations. Windhounds speed ranges during prey search and coursing under natural conditions have been determined after preliminary assessment of their dependence on training, breed, and sex-related and individual characteristics of the dogs. The results show that the effectiveness of coursing is not directly related to the speed of windhounds and provide evidence for the existence of differences in behavioral strategies between breeds, i.e., for the influence of genetic features on the patterns of movement, search, and prey coursing. Similarities and differences in the hunting behavior of windhounds and wild predators of the genus Canis are discussed.     

The physiological cost of carrying light and heavy loads

Nine subjects walked on a treadmill with load weights equal to 10% and 40% of body weight carried on the back. Although the speed of the treadmill was selected so that the measured oxygen consumption (VO2) was the same for both load conditions, the heavier load placed an extra strain on the cardiopulmonary system and was perceived by all subjects as harder work than the lighter load. When the subjects worked at their own pace, walking on a level road or climbing stairs with load weights equal to 10% and 40% of body weight, they compensated for the heavier load by decreasing walking speed or climbing rate. Although the energy costs calculated from walking speed, body and load weight for self-paced walking and the external work of stair climbing were the same for both load conditions, the heavier load was again perceived as harder work. These findings are discussed as they relate to the definition of acceptable load weights.     

Chronophysiology of the cardiovascular system

The development of ambulatory blood pressure monitoring devices and the beat-by-beat measurement of heart rate have enabled it to be established that there are circadian rhythms in heart rate and blood pressure in subjects living normally. Investigations of these variables have led to quantification of their fall at night, and rapid rise on awakening and becoming active in the morning. These changes are of particular interest insofar as abnormalities in them are associated with cardiovascular problems and morbidity in patients and also act as risk factors in otherwise healthy individuals. It has also been shown that there are many other variables of the cardiovascular system. The causes of the circadian rhythms in heart rate and blood pressure are outlined, with particular stress upon the role of the autonomic nervous system, as assessed from low- and high-frequency components of the variation in heart rate measured beat-by-beat. Activity increases blood pressure, but there is evidence that this “reactivity” varies with time of day, and this also might be related to cardiovascular morbidity. Based upon data from several sources, including night work, resting subjects and bed-ridden patients, it is concluded that the contribution of the “body clock” to producing the circadian rhythm in heart rate and blood pressure is relatively small. A bias towards an exogenous cause applies also to most other circadian rhythms in the cardiovascular system. Knowledge of circadian rhythmicity in cardiovascular system, together with an understanding of its causes, provides a rationale for advice to reduce cardiovascular risk and to assess the efficacy of therapies.     

Pace and shape of senescence in three species of duckweed

Senescence is progressive bodily deterioration associated with declines in survival and fecundity in older age classes. There is great diversity in patterns of senescence across species, but these patterns can be difficult to compare formally due to variation in the absolute time scales in which species live and die: members of some species live for a matter of days, others for millennia. To address this issue, the “pace‐shape” approach was developed to decouple absolute time from analyses and instead standardize life history traits in terms of average life expectancy, facilitating intra‐ and interspecific comparisons. Here, we use this approach to distinguish the generic form of demographic trajectories (shape) from the time scale on which the trajectories occurred (pace) in three species of tiny, free‐floating aquatic plants known as duckweeds (Lemna gibba L., L. minor L., and L. turionifera Landolt), which have mean lifespans of less than a month under typical lab conditions, and exhibit age‐related declines in survivorship and reproduction. Using a randomized block design in which we tracked a final total of 430 individuals, we report differences in pace and shape among the three species. Specifically, the largest, least‐fecund, and typically longest‐lived species, L. gibba, tended to exhibit more rapid decreases in time‐standardized survivorship and fecundity compared with the other two species. This study emphasizes variation in aging patterns that can be found among plant species, including those in the same genus, and provides further validation for the utility of applying the pace and shape approach in interspecific comparisons.     

Behaviour in a standardized assay,but not metabolic or growth rate,predicts behavioural variation in an adult aquatic top predator Esox lucius in the wild

This study tested for links among behaviour, state and life‐history variables as predicted by the pace‐of‐life hypothesis in adult pike Esox lucius. First, a standardized open‐field behavioural assay was developed to assess individual behaviour of wild‐captured adult E. lucius. Behaviour within the standardized assay predicted swimming behaviour in the lake, providing an ecological validation of the assay. There was no relationship between standardized behaviour and any of the life‐history and state variables, including metabolism, body condition, juvenile growth rate and adult growth rate in contrast to predictions from the pace‐of‐life hypothesis. This study demonstrates that it is possible to assess ecologically relevant behavioural variation in a large‐bodied top predator using a standard open‐field assay, but it is noteworthy that this standardized behaviour is not systematically related to standard metabolism or growth.     

Elevational trends in life histories: revising the pace‐of‐life framework

Life‐history traits in birds, such as lifespan, age at maturity, and rate of reproduction, vary across environments and in combinations imposed by trade‐offs and limitations of physiological mechanisms. A plethora of studies have described the diversity of traits and hypothesized selection pressures shaping components of the survival–reproduction trade‐off. Life‐history variation appears to fall along a slow–fast continuum, with slow pace characterized by higher investment in survival over reproduction and fast pace characterized by higher investment in reproduction over survival. The Pace‐of‐Life Syndrome (POLS) is a framework to describe the slow–fast axis of variation in life‐history traits and physiological traits. The POLS corresponds to latitudinal gradients, with tropical birds exhibiting a slow pace of life. We examined four possible ways that the traits of high‐elevation birds might correspond to the POLS continuum: (i) rapid pace, (ii) tropical slow pace, (iii) novel elevational pace, or (iv) constrained pace. Recent studies reveal that birds breeding at high elevations in temperate zones exhibit a combination of traits creating a unique elevational pace of life with a central trade‐off similar to a slow pace but physiological trade‐offs more similar to a fast pace. A paucity of studies prevents consideration of the possibility of a constrained pace of life. We propose extending the POLS framework to include trait variation of elevational clines to help to investigate complexity in global geographic patterns.     

Maternal diet affects juvenile Carpetan rock lizard performance and personality

Differences in both stable and labile state variables are known to affect the emergence and maintenance of consistent interindividual behavioral variation (animal personality or behavioral syndrome), especially when experienced early in life. Variation in environmental conditions experienced by gestating mothers (viz. nongenetic maternal effects) is known to have significant impact on offspring condition and behavior; yet, their effect on behavioral consistency is not clear. Here, by applying an orthogonal experimental design, we aimed to study whether increased vitamin D₃ content in maternal diet during gestation (vitamin‐supplemented vs. vitamin control treatments) combined with corticosterone treatment (corticosterone‐treated vs. corticosterone control treatments) applied on freshly hatched juveniles had an effect on individual state and behavioral consistency of juvenile Carpetan rock lizards (Iberolacerta cyreni). We tested the effect of our treatments on (a) climbing speed and the following levels of behavioral variation, (b) strength of animal personality (behavioral repeatability), (c) behavioral type (individual mean behavior), and (d) behavioral predictability (within‐individual behavioral variation unrelated to environmental change). We found higher locomotor performance of juveniles from the vitamin‐supplemented group (42.4% increase), irrespective of corticosterone treatment. While activity personality was present in all treatments, shelter use personality was present only in the vitamin‐supplemented × corticosterone‐treated treatment and risk‐taking personality was present in corticosterone control treatments. Contrary to our expectations, behavioral type was not affected by our treatments, indicating that individual quality can affect behavioral strategies without affecting group‐level mean behavior. Behavioral predictability decreased in individuals with low climbing speed, which could be interpreted as a form of antipredator strategy. Our results clearly demonstrate that maternal diet and corticosterone treatment have the potential to induce or hamper between‐individual variation in different components of boldness, often in interactions.     

中国橡胶树气候适宜度分布特征研究

选取气温、降水、光照、风速四个气象要素,应用气候适宜度方法对中国橡胶树的气候适宜性进行定量评价.结果表明:中国橡胶树的气候适宜度指数均低于0.8,平均值为0.43,变化趋势普遍在±0.05(10a)-1之间,海南岛的大部分地区为橡胶树气候适宜区,广东,广西和福建南部以及云南南部的部分地区为较适宜区;降水适宜度均值为0....