Parent–offspring and sibling conflict in Galápagos fur seals and sea lions

Parent–offspring conflict theory is well supported by theoretical arguments. However, empirical observations are often difficult to interpret and have contradicted one of its most appealing predictions that parent and offspring should disagree over killing of nest or littermates. We present the first examples of deadly conflict between siblings of different cohorts. In Galápagos fur seals (Arctocephalus galapagoensis) and sea lions (Zalophus wollebaeki), mothers often wean their single offspring at 2 years. This leads to a situation where up to 23% of all pups are born while the older sibling is still being nursed. Younger siblings are disadvantaged by being born lighter than neonates without older still dependent siblings. Pups born while an older sib is still dependent grow less in early life (fur seal) and suffer increased early mortality (both species) through direct aggression or scramble competition with the older sibling. This effect is much stronger in years of high sea surface temperature (El Niño) indicating low marine productivity and if the older offspring is a male. In both species, mothers interfere aggressively in this conflict by defending the younger offspring. In years of El Niño, intense resistance to maternal aggression by the older offspring happens frequently in the fur seal. Such resistance against weaning can induce maternal neglect of the newborn. Given substantial year to year variation in offspring growth, maternal aggression forces weaning in the older sibling only if it has reached sufficient size to support itself by foraging. In Galápagos fur seals, pups with older siblings can either represent insurance against loss of older offspring or extra reproductive value.     

Cooperative signaling as a potential mechanism for cohesion in a gregarious sawfly larva, <Emphasis Type="Italic">Perga affinis</Emphasis>

During periods of travel or dispersive activities (e.g., foraging), group-living animals face the common challenge of maintaining a cohesive unit. At the basic level, this challenge is no different for vertebrates than it is for arthropods and is solved through communication. Gregarious larvae of the Australian sawfly, Perga affinis, communicate via vibrational signals. The most common signal, tapping, involves striking the substrate with the sclerotized tip of the abdomen. This study investigates the role of tapping as a mechanism of cohesion, specifically in situations between a separated larva and a group. As nomadic foragers that move daily to new feeding locations and readily coalesce with other colonies, the possibility of separation and potential re-aggregation arises regularly. Experiments demonstrated that tapping facilitates cohesion as groups responded to the tapping of lone larvae and did so preferentially over other larval behaviors. Additionally, separated larvae respond to tapping by the group through increased walking activity. It is also possible that they receive directional information from the group's vibratory signals, although visual cues may influence orientation as well. Tapping represents a cooperative signal and, as such, I investigated the level of investment of both parties in the communicative exchange. While individual larvae invested more in the exchange than the group, the exchange is analogous to the Raise-the-Stakes model of cooperation in that groups gradually increased their investment according to the cumulative time spent tapping by the lone larva. The mutual but asymmetrical benefits received through cooperation are discussed and compared with similar situations between parents and offspring. Not all larvae in the group participated equally, suggesting individual differences in signaling propensity or strategy.     

可持续发展能力建设与人力资本投资

本文在分析阐述可持续发展能力建设的内涵及可持续发展能力建设与人力资本投资关系的基础上 ,得到以下几个结论 :①可持续发展能力建设包含人类发展能力和自然支撑能力。②人力资本投资不仅可以提高人类发展能力 ,也能提高自然支撑能力。③人力资本投资能能为可持续发展提供一个良好的外部运行环境。因此 ,在实施可持续发展战略过程中 ,加强人力资本投资是至关重要的。     

Infant handling and mortality in yellow baboons (<Emphasis Type="Italic">Papio cynocephalus</Emphasis>): evidence for female reproductive competition?

This study examines negative and positive infant handling behavior in 24 free-ranging yellow baboon infants (Papio cynocephalus) studied over a 5-year period in Mikumi National Park, Tanzania. We test predictions of the female reproductive competition hypothesis to explain patterns of infant handling behavior by adult females (excluding the infants mother) in relation to observed cases of infant mortality by age 3 months (25% of infants in this study). Results show that: (1) low-ranking infants received more negative infant handling than high-ranking infants; conversely high-ranking infants received more positive infant handling; (2) female kin engaged in higher levels of positive infant handling than did non-kin, whereas non-kin showed higher levels of negative infant handling; (3) rates of negative infant handling varied by season, with high levels at the onset of the rainy season; and (4) high level of negative infant handling was a significant predictor of infant mortality by age 3 months (infant rank and sex did not predict survival). We discuss how the occurrence and interpretation of infant handling behavior in the literature has likely been confused by different definitions of this behavior, as well as differences in the socio-ecological context in which this behavior occurs.Communicated by C. Nunn     

Female control of reproductive skew in cooperatively breeding brown jays (<Emphasis Type="Italic">Cyanocorax morio</Emphasis>)

Brown jays (Cyanocorax morio) are long-lived, social corvids that live in large, stable, territorial groups (mean = 10 individuals). In this study, I determined the distribution of reproductive success within groups using multi-locus DNA fingerprinting. Breeding females produced virtually all (99%) of the young within their own nests. Reproduction within groups was highly skewed towards a single primary female, although long term data indicate that secondary females (female breeders that were usually younger and subordinate to the primary female) were sometimes successful. The high reproductive skew observed for females was associated with primary female aggression. Successful reproduction by secondary females may have been due to parental facilitation or the inability of primary females to completely suppress secondary females. Multiple paternity occurred in 31–43% of broods and extra-group paternity occurred in a minimum of 22% of broods. Patterns of paternity also varied between years, since females often switched or included new genetic mates. Although male consorts of nesting females fathered relatively few offspring (20%), they still had a higher chance of fathering offspring than any other single group male. Reproduction was less skewed for males than females as a result of female mating patterns. Female reproductive patterns are consistent with some of the predictions and assumptions from optimal skew models, while male reproductive patterns are not. The factors affecting skew in species with complex social systems such as incomplete control by breeders over subordinate reproduction, female control of paternity, and resource inheritance have not been well incorporated into reproductive skew models.Communicated by: J. Dickinson     

Maternal investment, sex-differential prospects, and the sex ratio in wild house mice

In a population of first-generation offspring from wild-caught house mice (Mus musculus domesticus), previous evidence suggested that male fitness is more strongly affected by an increase in body weight than female fitness. This paper shows that in these mice the young are weaned at heavier weights the smaller the litter and the better the maternal body condition. These effects persisted into adulthood and were less pronounced in female young. However, contrary to expectation from conventional sex ratio theory, maternal condition and litter size had no detectable effect on sex ratios. Also, litter size did not affect sex ratios in two populations of laboratory-kept, wild-caught western (M. m. domesticus) and eastern house mice (M. m. musculus). Wild house mice, therefore, appear not to adaptively manipulate the sex ratio of offspring. It is argued that this absence of sex ratio trends might not be maladaptive, but rather that models currently used to predict sex ratio trends in rodents may not be valid. Received: 13 March 1997 / Accepted after revision: 9 August 1997     

环保融投资须与资本市场发展相适应——关于环保融投资体制问题调查和发展对策思考

本文针对在建立和完善环保资本市场中环保融投资出现的一系列矛盾和问题，从环保投资的机构形式、资金来源、经营方略和发展方向等方面提出相应可操作性对策。     

中国沿海开放地区工业污染控制的探讨

在环境保护工作由污染问题治现向清洁生产转变过程中，中国沿海开放地区、外资，合资、集体和个体企业在其工业结构中所占比重较大，且要求有良好投资环境，当前控制工业污染，须按社会主义市场经济规律征收资源费和排污费，同时要加强环境规划，建立环境管理系统，有效调工业污原杂源，为保证受损环境得以恢复，须加强环境建设和环境投资。     

Evidence of equal maternal investment in the sexes in the polygynous and sexually dimorphic grey seal (Halichoerus grypus)

In polygynous and sexually dimorphic mammals, parents may be expected to bias their investment towards sons because variation in reproductive success is usually higher among males than among females. Moreover, male reproductive success often depends on adult body size, which, in turn, may depend on the level of parental investment. We therefore predicted that in the grey seal (Halichoerus grypus), a polygynous and sexually dimorphic phocid seal, females should invest more in individual sons than in individual daughters. We found that male pups were born heavier than female pups, but that the growth rates and suckling behaviour were similar for the two sexes. The growth rates and the birth weights were not correlated for the pups of either sex. Mothers did not behave differentially towards offspring of the two sexes, except that mothers of male pups spent more time in visual contact with their pups. Male and female pups had similar activity levels and begged at similar rates. We argue that reports of equal expenditure on the two sexes can be accepted as evidence of equal investment, provided that three assumptions are fulfilled. First, parental care must be costly to the parent. Second, energy expenditure must be the most important component of parental investment. Third, there must be no negative correlation between maternal body condition and the ratio of sons to daughters produced. We argue that these assumptions are met in our study, and that our results provide evidence of equal maternal investment in the sexes in grey seals.     

关于安全投入的探讨

根据安全系统工程及安全经济学原理，对安全投入的广泛性、必要性、难点及解决途径进行了系统的探讨，供决策人员及安全管理人员参考。