Proximate Reason Research Articles

Population dynamics of the White Stork Ciconia ciconia in western France

Population dynamics of the White StorkCiconia ciconiawere studied in Charente‐Maritime, France from 1978 to 1996, during which time the number of breeding pairs increased from one to 44. Modal age at first return and first breeding were 2.4 and 3.4 years, respectively. White Storks produced an average of 3.2 fledglings per nest. The average number of fledglings per nest decreased with increasing nest density, probably because of an increase in the number of interactions between breeding birds. Nests surrounded by marshes had slightly greater productivity than nests on peripheral sites. Individual White Storks followed an annual breeding cycle and attempted to breed in 97% of seasons once mature. Nest‐site and mate fidelity were high (88 and 83%, respectively). Immigration rate was nearly twice that of emigration during the last few years of the study and recruitment was close to 30%, although underestimated. We modelled survival and recapture probabilities using capture‐mark‐recapture methods. Adult survival was found to be dependent on age, but not sex. Survival of younger birds varied greatly over the years, whereas survival of older birds was relatively constant and averaged 78%. Survival rates of young birds wintering in the Sahel zone were positively linked to the amount of rainfall in their wintering area. The proximate reason for the population increase was probably immigration of birds from other European countries, probably encouraged by a high adult survival rate. Ringing recoveries indicate that some birds winter in Spain and the high adult survival rate may reflect a change in migratory pattern in recent years. Finally, reproductive success was relatively high during the study.

Influenza Infection Neutralizes the Attractiveness of Male Odour to Female Mice (Mus musculus)

AbstractThis study aimed to determine if female house mice, Mus musculus domesticus, are able to assess a male's infection status from odour cues. We collected urine from male mice before, during, and after they were experimentally infected with influenza, a respiratory virus. Females spent more time investigating urine collected from males while they were uninfected than when they were infected. Also 70 % of females released into a large enclosure preferred to nest in boxes containing urine collected from uninfected rather than infected males. This is the first evidence that mice can discriminate virally infected individuals through chemical signals and the first evidence that infection causes odour changes in the urine. To determine if the odour of infected males is repulsive, we presented females with urine samples and neutral water blanks. Normal urine collected from uninfected males was more attractive, whereas urine collected during infection was as attractive as water. This indicates that rather than being aversive, influenza infection abolishes the attractiveness of a male's odour. A similar effect also occurs when male mice are infected with coccidian gut parasites (Kavaliers & Colwell 1995, Proc. R. Soc. Lond. 261B, 31–35). One proximate reason for the neutralization of the attractiveness of a male's odour may be a decrease in serum androgen concentrations during infection.

Antimicrobial Functions of Spices: Why Some Like it Hot

Although spices have been important for centuries in food preparation throughout the world, patterns of spice use differ considerably among cultures and countries. What factors underlie these differences? Why are spices used at all? To investigate these questions, we quantified the frequency of use of 43 spices in the meat-based cuisines of the 36 countries for which we could locate traditional cookbooks. A total of 4578 recipes from 93 cookbooks was analysed. We also complied information on the temperature and precipitation in each country, the ranges of spice plants, and the antibacterial properties of each spice. These data were used to investigate the hypothesis that spices inhibit or kill food-spoilage microorganisms. In support of this is the fact that spice plant secondary compounds are powerful antimicrobial (i.e., antibacterial and antifungal) agents. As mean annual temperatures (an indicator of relative spoilage rates of unrefrigerated foods) increased, the proportion of recipes containing spices, number of spices per recipe, total number of spices used, and use of the most potent antibacterial spices all increased, both within and among countries. Likewise, the estimated fraction of bacterial species inhibited per recipe in each country was positively correlated with annual temperature. Several alternative hypotheses were considered--that spices provide macronutrients, disguise the taste and smell of spoiled foods, or increase perspiration and thus evaporative cooling; it also is conceivable that spice use provides no benefits. However, none of these four alternatives was well supported by our data. The proximate reason spices are used obviously is to enhance food palatability. But the ultimate reason is most likely that spices help cleanse foods of pathogens and thereby contribute to the health, longevity and reproductive success of people who find their flavors enjoyable.

Behavioral patterns and proximate reason of young male separation in Misaki feral horses

The present investigation was undertaken to study the proximate reasons why and the behavioral patterns of young male Misaki feral horses when they left their natal band or mothers. We observed a total of ten young males twice a month from January 1988 to December 1995. Almost all young males left their natal band or mothers at between 1 and 4 years of age. We found that, during the separation process, all the young males from first parity dams returned several times after the initial separation, indicating a strong attachment between primiparous mares and their male offspring. The other five separated only once without rejoining. Our observations showed five variable behavior patterns of young males at separation time, depending on the consort relation between their mothers and harem stallion and the reason for separation at that time. Eight young males separated in the non-breeding season at average 2.1 years and the other two separated in the breeding season at average 3 years and the average difference was not significant. These results revealed that 80% of the young males separated voluntarily when the natural resources become poor whereas 20% separated when their siblings were born.

Singer, services and software

It is more than 40 years ago that Hans Singer published his celebrated paper on the “Distribution of Gains between the Investing and Borrowing Countries”. This article reexamines his hypothesis that the gains from foreign investment tend to be distributed heavily in favor of the investing countries in the context of India's fast-growing computer software sector. It identifies the proximate reasons for the birth and growth of a human capital-intensive service sector in a poor country and raises issues concerning its costs and benefits to the economy. It suggests that investments in services, such as software, too can result in export enclaves with very little forward and backward linkages with the rest of the economy in which they are located.

Capital Breeders and Income Breeders among Lepidoptera: Consequences to Population Dynamics

Among Lepidoptera, populations of some species display outbreaks at irregular intervals, some show regular cycles, whereas densities of most species never reach extremely high values. In recent years, researchers have looked for correlations between life-history traits and different types of population dynamics (Nothnagle and Schultz 1987, Hunter 1991, Hunter 1995a) while others have generalized based on relatively few but well-studied cases (Price et al. 1990, Price 1994). The proximate reasons of changes in population density presumably are in the environment (Ruohomiki and Haukioja 1992) but these kinds of observations may have masked the importance of life-history x environment interactions. Here we emphasize the importance of adult feeding, a correlate of eruptive (sensu Price et al. 1990) and cyclic population dynamics among Lepidoptera which has deserved almost no attention until very recently (Miller 1996). Furthermore, we propose ecological and evolutionary explanations for the correlation.

Women, Children and Poverty in Canada

The terms feminization of and juvenization of refer to changes in the distribution of poverty by gender and age. One goal of this paper is to assess whether or not Canadian poverty has been feminized or juvenized since the early 1970s and what are the proximate reasons why such changes have occurred or failed to occur. The proximate reasons are (i) the differences in the poverty rates of women versus men and children versus adults and (ii) the demographic composition of the general population. My second goal is to ask if the anti-poverty impact of transfer and tax policy differs for women versus men (or for children versus adults), and if any such gender or age bias has changed over time.

Prior residency as a key determinant of social dominance in the willow tit (Parus montanus)

We studied how age, body size and prior residency affected social dominance in the willow tit (Parus montanus) groups. The contribution of each variable was experimentally tested in unisexual two-bird trials, in which the birds were matched for all variables except the one studied. Large birds were dominant over smaller ones (Fig. 1). The effect of body size was more prominent in males than in females. Age had no influence on dominance. Residents became dominant more often than newcomers (Fig. 2). Adulthood or larger body size did not override the advantage of prior residency (Fig. 2). Therefore, the proximate reason for the age-dependent dominance seen in natural willow tit flocks is most likely the prior residency advantage of the adults. Factors connected with fighting ability (body size and age) seem to be less important than the time of establishment of rank, which may reflect the importance of resource value differences between residents and newcomers in this context. The advantage of residency might make it advantageous to be a member of a flock even as a subordinate, rather than being solitary.

Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes: an alternative mechanism

The loss of submerged macrophytes during eutrophication of shallow lakes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment.

Nineteenth-century Ireland: the search for stability

Nineteenth-century Ireland began and ended in armed revolt. bloody insurrections of 1798 were the proximate reasons for the passing of the Act of Union two years later. 'long nineteenth century' lasted until 1922, by which time the institutions of modern Ireland were in place against a background of the Great War, the Ulster rebellion and the armed uprising of nationalist Ireland. years between 1800 and 1922 were an attempt to make the union work. In the words of Professor Boyce's subtitle, they represented a search for stability - the hope that, in an imperial structure, the ethnic, religious and national differences of the inhabitants of Ireland could be reconciled and eliminated. search for stability proved elusive. Nationalist Ireland - overwhelmingly Catholic - mobilised a mass democratic movement under O'Connell to secure Catholic Emancipation before seeing its world transformed by the social cataclysm of the Great Famine. At the same time, the Protestant north-east of Ulster was feeling the first benefits of the Industrial Revolution. Although post-Famine Ireland modernised rapidly, only the north-east had a modern economy. mixture of Protestantism and manufacturing industry integrated into the greater United Kingdom and gave a new twist to the traditional Irish Protestant hostility to Catholic political demands. In the home rule period from the 1880s to 1914, the prospect of partition moved from being almost unthinkable to being almost inevitable. Nineteenth-century Ireland collapsed in the various wars and rebellions of 1912-22. Like many other parts of Europe than and since, it had proved that an imperial superstructure can contain domestic ethnic rivalries, but cannot always eliminate them. In Ireland, the malign divisions of history proved too strong. search for stability failed. '...a substantial and thoroughly crafted study of a very complex period...His virtues as a historian predominate - clarity of thought and style, and a mastery of the telling quotation, which penetrates to the heart of the matter.' The Irish Times.

Do common ravens yell because they want to attract others?

The formation of groups at food bonanzas results from a variety of mechanism, which include recruitment by signalling and information parasitism. Recruitment is distinguished from information parasitism on functional grounds: attraction of a crowd is termed recruitment if the signaler's fitness is enhanced by the attraction of others but termed parasitism if the signaler's fitness is reduced by the attraction of others. We here show, however, that in Common Ravens, Corvus corax, the proximate reasons for giving recruitment signals are probably other than for attracting a crowd. In the forests of the northeastern United States, non-breeding, vagrant ravens commonly aggregate in large numbers at carcasses where they neutralize the defense of territorial adults. We attempted to mimic this situation with a captive flock of juveniles and a pair of resident adults in order to determine the proximate factors triggering “yells”, vocalizations which attract nearby ravens to large animal carcasses. Our experiments indicate that yells are given primarily by hungry birds. However, yelling is strongly modified by status. Within the vagrant crowd, status is labile. When successive dominants were removed, replacements immediately took their place. Furthermore, when the dominants were re-introduced to the flock they always suffered significant losses of status and ceased yelling. The territorial male has, and constantly maintains, the highest status within (but not necessarily outside) his territory, and here he rarely yells. In sharp contrast, within the vagrant crowd of unmated birds it is the highest-status birds that are the most likely to yell when approaching food. Furthermore, the dominant vagrants (as well as adults) suppress yelling in subordinates. We conclude that ravens yell proximately to advertise their status at food, and that recruitment is only one of several ultimate advantages of the behavior.

Wage structures and labor turnover in the United States and Japan

The starting point of this study is the proposition that intensive formation of human capital on the job is the basic proximate reason for the strong degree of worker attachment to the firm in Japan. The greater emphasis on training and retraining, much of it specific to the firm, results also in steeper wage trajectories, due to growth of skills in the firm. Several previous studies viewed the differences between Japanese and U.S. labor markets in the light of the same hypothesis. We explore this insight more thoroughly by a detailed use of microdata for the two countries: we measure wage profiles and turnover in age groups and we test the inverse relation between the two on industry sectors within each of the countries. Numerical estimates of this relation permit us to conclude that as much as two-thirds of the differential in turnover between the two countries is explainable by the differences in the steepness of the profiles. The question remains why the emphasis on human capital formation on the job is so much greater in Japan than in the United States. Our answer is that such emphasis is conditioned by rapid economic growth. More specifically, Japanese labor policies in the firm represent adjustments of worker skills and activities to the very rapid technological changes of the past decades. Using productivity growth indexes for industries in the United States and Japan we test the hypothesis that rapid technical change, which induces greater and continuous training, is in part responsible for steeper profiles and for lesser turnover. The hypothesis is confirmed on the sectoral level in both countries. We conclude that differences in productivity growth between the United States and Japan account for up to 80% of the differences in the steepness of wage profiles, and indirectly for the differences in turnover. Finally, we try to standardize for the cultural background of workers, by observing a sample of Japanese plants in the United States which employ American workers and use Japanese labor policies in recruitment and training. We find that the steeper tenure-wage slopes and lower turnover place this sample closer to Japan than to the United States—about two-thirds of the distance.