Competition among mammalian siblings for scarce resources can be severe. Whereas research to date has focused on competition
for the mother’s milk, the young of many (particularly altricial) species might also be expected to compete for thermally
favorable positions within the nest, den, or litter huddle. We investigated this in newborn pups of the European rabbit Oryctolagus cuniculus, a species in which the altricial young are not brooded by the mother, and in which competition for milk is severe. In eight
unculled litters (N = 86 pups) of a domestic chinchilla strain, we calculated huddling indexes for individual pups on postnatal days 2–5 as a
measure of the degree of insulation they received from littermates. Pups maintained almost constant physical contact with
the litter huddle. They performed brief but frequent rooting and climbing behaviors, which usually improved their huddling
index, interspersed with longer periods of quiescence during which their huddling index declined. As expected, we found a
significant positive relation between pups’ mean huddling index and body temperature. Unexpectedly, however, we did not find
a relation between huddling index and pups’ birth weight, survival, milk intake, or efficiency of converting milk to body
mass. We conclude that rather than competing for thermally advantageous positions within the huddle newborn rabbits share
out thermally advantageous positions as they move in a continual dynamic flow through it. Thus, in newborn rabbits, competition
for the mother’s milk exists alongside mutual “cooperative” benefits of littermate presence.
This contribution is part of the special issue “Sibling competition and cooperation in mammals” (guest editors: Robyn Hudson
and Fritz Trillmich). 相似文献
Theory predicts that frequent dyadic association should promote cooperation through kin selection or social tolerance. Here
we test the hypothesis that sex differences in the strength and stability of association preferences among free-ranging chimpanzees
conform to sex differences in cooperative behavior. Using long-term data from the Kanyawara chimpanzee (Pan troglodytes schweinfurthii) community (Kibale National Park, Uganda), we calculated indices of intra-sexual dyadic association over a 10-year period.
We found that (1) male–male dyads had significantly stronger association indices than female–female dyads, (2) the pattern
of association preferences in both sexes changed little over the entire study period, and (3) when comparing periods with
different alpha males, changes in association strength were more frequent among males. These results demonstrate that both
the strength and stability of association patterns are important components of social relationships. Male chimpanzees, which
are characterized by frequent cooperation, had association preferences that were both strong and stable, suggesting that forming
long-term bonds is an important dominance strategy. However, the fact that male association patterns were sensitive to upheaval
in the male dominance hierarchy suggests that males also take advantage of a changing social climate when choosing association
partners. By contrast, the overall strength of female associations was relatively weak. Female association preferences were
equally stable as males’; however, this reflected a dyad’s tendency to be found in the same party rather than to associate
closely within that party. Therefore, in this community, female association patterns appear to be more a consequence of individual
ranging behavior rather than a correlate of cooperation. 相似文献
Objective: To examine crash rates over time among 16–17-year-old drivers compared to older drivers. Methods: Data were from a random sample of 854 of the 3,500 study participants in SHRP 2, a U.S. national, naturalistic driving (instrumented vehicle) study. Crashes/10,000 miles by driver age group, 3-month period, and sex were examined within generalized linear mixed models. Results: Analyses of individual differences between age cohorts indicated higher incidence rates in the 16–17-year old cohort relative to older age groups each of the first four quarters (except the first quarter compared to 18–20 year old drivers) with incident rate ratios (IRR) ranging from 1.98 to 18.90, and for the full study period compared with drivers 18–20 (IRR = 1.69, CI = 1.00, 2.86), 21 to 25 (IRR = 2.27, CI = 1.31, 3.91), and 35 to 55 (IRR = 4.00, CI = 2.28, 7.03). Within the 16–17-year old cohort no differences were found in rates among males and females and the decline in rates over the 24-month study period was not significant. Conclusions: The prolonged period of elevated crash rates suggests the need to enhance novice young driver prevention approaches such as Graduated Driver’s Licensing limits, parent restrictions, and post-licensure supervision and monitoring. Practical Applications: Increases are needed in Graduated Driver’s Licensing limits, parent restrictions, and postlicensure supervision and monitoring. 相似文献
Objectives: Every year, about 1.24 million people are killed in traffic crashes worldwide and more than 22% of these deaths are pedestrians. Therefore, pedestrian safety has become a significant traffic safety issue worldwide. In order to develop effective and targeted safety programs, the location- and time-specific influences on vehicle–pedestrian crashes must be assessed. The main purpose of this research is to explore the influence of pedestrian age and gender on the temporal and spatial distribution of vehicle–pedestrian crashes to identify the hotspots and hot times.
Methods: Data for all vehicle–pedestrian crashes on public roadways in the Melbourne metropolitan area from 2004 to 2013 are used in this research. Spatial autocorrelation is applied in examining the vehicle–pedestrian crashes in geographic information systems (GIS) to identify any dependency between time and location of these crashes. Spider plots and kernel density estimation (KDE) are then used to determine the temporal and spatial patterns of vehicle–pedestrian crashes for different age groups and genders.
Results: Temporal analysis shows that pedestrian age has a significant influence on the temporal distribution of vehicle–pedestrian crashes. Furthermore, men and women have different crash patterns. In addition, results of the spatial analysis shows that areas with high risk of vehicle–pedestrian crashes can vary during different times of the day for different age groups and genders. For example, for those between ages 18 and 65, most vehicle–pedestrian crashes occur in the central business district (CBD) during the day, but between 7:00 p.m. and 6:00 a.m., crashes among this age group occur mostly around hotels, clubs, and bars.
Conclusions: This research reveals that temporal and spatial distributions of vehicle–pedestrian crashes vary for different pedestrian age groups and genders. Therefore, specific safety measures should be in place during high crash times at different locations for different age groups and genders to increase the effectiveness of the countermeasures in preventing and reducing vehicle–pedestrian crashes. 相似文献
Heavy metal concentrations in urban soils are likely to increase over time because of continuous urbanization and heavy metal emissions. To estimate the accumulation rates of heavy metals in urban soils, we collected soil samples from residential areas with different building ages in the metropolitan cities of Shanghai, Shenzhen, and Beijing, China. Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogen... 相似文献
Functional-ontogenetic determination of age-dependent dental changes (ADCs) in voles has been demonstrated. The relationship between ADCs and the functional state of animals has been analyzed. A scheme and a table for determining individual chronological and biological ages in the bank vole (Clethrionomys glareolus Sch.) are proposed, which markedly improve the accuracy of results. Cases of rodent maturation and breeding in winter are considered. 相似文献