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61.
Among the order of primates, torpor has been described only for the small Malagasy cheirogaleids Microcebus and Cheirogaleus. The nocturnal, gray mouse lemur, Microcebus murinus (approx. 60 g), is capable of entering into and spontaneously arousing from apparently daily torpor during the dry season
in response to reduced temperatures and low food and water sources. Mark–recapture studies indicated that this primate species
might also hibernate for several weeks, although physiological evidence is lacking. In the present study, we investigated
patterns of body temperature in two free-ranging M. murinus during the austral winter using temperature-sensitive data loggers implanted subdermally. One lemur hibernated and remained
inactive for 4 weeks. During this time, body temperature followed the ambient temperature passively with a minimum body temperature
of 11.5°C, interrupted by irregular arousals to normothermic levels. Under the same conditions, the second individual displayed
only short bouts of torpor in the early morning hours but maintained stable normothermic body temperatures throughout its
nocturnal activity. Reduction of body temperature was less pronounced in the mouse lemur that utilized short bouts of torpor
with a minimum value of 27°C. Despite the small sample size, our findings provide the first physiological confirmation that
free-ranging individuals of M. murinus from the humid evergreen littoral rain forest have the option to utilize short torpor bouts or hibernation under the same
conditions as two alternative energy-conserving physiological solutions to environmental constraints. 相似文献
62.
V. Alzaga J. Vicente D. Villanua P. Acevedo F. Casas C. Gortazar 《Behavioral ecology and sociobiology》2008,62(5):769-775
Preys require effective anti-predator traits to escape from predator attacks, whereas predators focus on individuals that
have lower fitness. This fitness reduction is due to the effects of many regulatory forces such as parasites. We directly
observed in the field the escape performance of the Iberian hare (Lepus granatensis) against coursing predators (measured as the time to be taken by greyhounds) and examined the relationships between parasite
loads and duration of escape behaviours to test the hypothesis that predators would more easily catch substandard individuals.
We found a negative relationship between the hare’s escape duration and parasite burdens in various taxa (Taenia pisiformis cisticercus, intestinal Coccidia) as well as with parasite diversity. Moreover, the escape duration of the hares is related
positively to their condition. In the particular case of T. pisiformis cisticercus, we found a negative relationship with body condition, suggesting that its effect on anti-predation ability could
be mediated by direct spoliation of host resources and/or by increasing requirements for anti-parasite defence. As parasite
loads were not directly manipulated, experimental studies are needed to elucidate any causal links between parasite and anti-predatory
capacity in Iberian hares. 相似文献
63.
Javier Balbontín Anders P. Møller Ignacio G. Hermosell Alfonso Marzal Maribel Reviriego Florentino de Lope 《Behavioral ecology and sociobiology》2009,63(8):1197-1205
Dispersal is an important factor that determines the degree of gene flow and, hence, the degree of differentiation among populations.
Using two long-term datasets on natal philopatry and short-distance dispersal in barn swallows Hirundo rustica from Denmark and Spain, we evaluated the fitness costs and benefits and test a number of predictions about the functional
significance of dispersal. The proportion of philopatric individuals was more than six times larger in Spain than in Denmark,
with a higher rate of philopatry in males than in females. Dispersal propensity decreased in both populations during the course
of the study. Males from the more philopatric Spanish population lived longer when philopatric rather than dispersing while
that was not the case for either sex of the less philopatric Danish population. There were large differences in dispersal
propensity among cohorts and breeding sites, suggesting that sites differed in their suitability as sites for immigrants.
We found no evidence consistent with the mate competition hypothesis suggesting that males in better condition or with larger
condition-dependent secondary sexual characters were more likely to be philopatric. These findings suggest that there is a
high degree of intraspecific variation in dispersal propensity between populations, probably relating to local differences
in costs and benefits of philopatry and dispersal. 相似文献
64.
Heavier birds react faster to predators: individual differences in the detection of stalking and ambush predators 总被引:1,自引:1,他引:0
Katherine A. Jones John R. Krebs Mark J. Whittingham 《Behavioral ecology and sociobiology》2009,63(9):1319-1329
The relationship between body mass and reactions speed in response to a predatory threat is poorly understood. Theory predicts
that different vigilance patterns are optimal for the detection of different predator types. We suggest that birds of different
individual state might also differ in their speed of response dependent upon predator type. We used laboratory trials of wild
caught chaffinches (Fringilla coelebs) to determine how between individual differences in chaffinch behaviour and state correlate with latency to react to a ground
predator model (domestic cat), thus providing a comparison with previous work in the same model system using aerial predator
models. In experiment 1, we observed chaffinch responses to a moving cat model, simulating a stalking predator. In experiment
2, we used a camouflaged cat model simulating an ambush predator. Both experiments show evidence suggesting heavier individuals
(which previous literature has linked to impaired flight performance) responded more quickly to the model cat. Heavier individuals
also had shorter interscan intervals. In contrast to a previous study, both experiments found individuals with a higher intake
rate were not faster at responding to the cat model. In addition, individuals in experiment 1 that head turned more while
scanning were slower to respond to the stalking cat model. Our work suggests that although heavier individuals may have impaired escape performance
they appear to show behavioural compensation by allocating more attention to anti-predator behaviour and by modifying their
interscan intervals, resulting in faster response times to a ground predator. We suggest more experiments investigating response
time to different predatory types and explicitly manipulating state to elucidate cause and effect. 相似文献
65.
Social nesting behaviour is commonly associated with high prevalence and intensity of parasites in intraspecific comparisons.
Little is known about the effects of interspecific host breeding density for parasite intensity in generalist host–parasite
systems. Darwin’s small tree finch (Camarhynchus parvulus) on Santa Cruz Island, Galápagos Islands, nests in both heterospecific aggregations and at solitary sites. All Darwin finch
species on Santa Cruz Island are infested with larvae of the invasive blood-sucking fly Philornis downsi. In this study, we test the prediction that total P. downsi intensity (the number of parasites per nest) is higher for nests in heterospecific aggregations than at solitary nests. We
also examine variation in P. downsi intensity in relation to three predictor variables: (1) nest size, (2) nest bottom thickness and (3) host adult body mass,
both within and across finch species. The results show that (1) total P. downsi intensity was significantly higher for small tree finch nests with many close neighbours; (2) finches with increased adult
body mass built larger nests (inter- and intraspecific comparison); (3) parasite intensity increased significantly with nest
size across species and in the small tree finch alone; and (4) nest bottom thickness did not vary with nest size or parasite
intensity. These results provide evidence for an interaction between social nesting behaviour, nest characteristics and host
mass that influences the distribution and potential impact of mobile ectoparasites in birds. 相似文献
66.
束缚装置选型是新版中国标准中增加的一项重要内容,中国标准借鉴了美国标准和欧盟标准,但并未完全采用.因此,进行中国标准、美国标准和欧盟标准的比较研究非常重要.本文从人体坐标系、加速度区域和束缚装置准则三个方面对中国标准、美国标准和欧盟标准中的相关内容进行了全面对比,分析了各自的优缺点.在人体坐标系方面,中国标准定义较为合... 相似文献
67.
We studied geographical and temporal body size trends among 169 adult museum specimens of the Eurasian otter (Lutra lutra) collected in Sweden between 1962 and 2008, whose sex, year of collection, and locality were known. Skull size and body mass
increased significantly in relation to the year of collection, and skull size (but not body mass) was significantly and negatively
related to latitude, contrasting Bergmann’s rule and the trend found for Norwegian otters. Latitudinal differences in body
size between the two countries may be due to differences in food availability. The temporal increase in body size among Swedish
otters resembled that observed for Norway otters, though Swedish otters are smaller with respect to their Norwegian counterparts.
Latitude and year represent a combination of environmental factors, including ambient temperature in the year of collection
as well as the number of days of ice coverage. We replaced the above factors with mean annual temperature or the number of
days of ice coverage, and found that each of these factors explains a similar proportion of the variation in body size as
did latitude and year. We hypothesize that this temporal increase in body size is related to a combination of factors, including
reduced energy expenditure resulting from increasing ambient temperature, and increased food availability from longer ice-free
periods. 相似文献
68.
Tsukimori K Uchi H Mitoma C Yasukawa F Fukushima K Todaka T Kajiwara J Yoshimura T Hirata T Wake N Furue M 《Chemosphere》2011,84(7):928-935
Accumulated maternal dioxins are passed onto the fetus and neonate via the placenta and maternal milk. In Japan in 1968, an accidental human exposure to rice oil contaminated with polychlorinated biphenyls (PCBs) and other dioxin-related compounds, such as polychlorinated dibenzofurans (PCDFs), led to development of Yusho oil disease. We investigated differences in blood dioxin concentrations in mother-children pairs affected by the Yusho incident. From 2002 to 2008, blood samples were collected from 26 pairs of Yusho mothers and their children (19 mothers, 26 children). Specific congeners of seven polychlorinated dibenzo-p-dioxins (PCDDs), ten PCDFs, and four non-ortho PCBs were analyzed. The children had significantly lower TEQ concentrations of PCDDs, PCDFs, and coplanar PCBs compared to their mothers. The mother-child difference in blood concentrations varied with the congeners; the largest for 2,3,4,7,8-pentaCDF and the smallest for 1,2,3,4,6,7,8-heptaCDD. The level for 2,3,4,7,8-pentaCDF, which characterizes Yusho oil disease, was approximately 17-30 times higher in the mothers than in the general population, whereas there were no significant differences between children in the formula-fed group and the general population. In contrast, the mean level for 2,3,4,7,8-pentaCDF in the breast-fed group was approximately 1.5 times, (range 0.5-6.5 times) higher than that in the general population. Over 30 years after the Yusho incident, the mean blood dioxin levels in the offspring were only a fraction of the levels in their mothers. This is more consistent with exposure via breast milk than via transplacental transfer in the Yusho incident. 相似文献
69.
Bird DJ Rotchell JM Hesp SA Newton LC Hall NG Potter IC 《Environmental pollution (Barking, Essex : 1987)》2008,151(3):641-651
We explored how hepatic [metal]s in Anguilla anguilla at a contaminated estuarine site are influenced by body size, age and season, and the extent that [Cu], [Cd] and [Zn]s are reflected in [metallothionein (MT)]s. Although each [metal] and [MT] increased significantly with length, weight and age, those biotic variables explained <10% of the variation in each [metal] and only 11-16% for [MT]. Seasonal changes in [Cu] and [Cd] were paralleled by [MT]. The variation in [MT] explained by Cu (42%) was greater than by Zn (16%) and Cd (13%), and seasonally lay between 43 and 69% for those metals collectively. Thus, hepatic [MT] in eels is closely correlated with hepatic [heavy metal]s. However, the great variability among [MT]s for eels of similar sizes and ages, which reflects marked variability in hepatic [heavy metal]s, means that this variable reflects imprecisely the contamination level at a particular site. 相似文献
70.
Male costs and benefits associated with male display size in field populations of an Australian lekking Drosophila species were examined. Results suggested that male mating success increased with display size, since matings appeared to
be more common in large displays, and since the probability of males encountering a female increased as displays contained
more males. Female encounter probabilities did not increase once about 20 males or more were present on a display. Male size
and fighting costs tended to increase with display size. The distribution of males among displays did not follow the ideal
free distribution in the sense that each male did not have equal mating opportunity per unit time. Deviation from an ideal
free distribution may have been due to female preference for mating in aggregations rather than with solitary males, since
in a field experiment females were more willing for mating in an aggregation of five males than with solitary males.
Received: 22 May 1997 / Accepted after revision: 1 November 1997 相似文献