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101.
Artificial manipulations of habitat, such as those that incorporate adding nesting boxes or platforms for birds, often enhance the breeding success of threatened animals. However, such alterations are likely to have unintended behavioral and ecological effects that might negatively impact the target species or others in its community. We conducted a controlled study to investigate the effect of artificial nesting platforms on aggressive behavior and reproductive success of male common loons (Gavia immer). Males residing on territories to which platforms were added produced longer territorial "yodels" (reflecting willingness to escalate a contest), experienced increased levels of confrontation and aggression with territorial intruders, and experienced increased rates of territorial displacement by intruders. Surprisingly, males of treatment territories also experienced lower productivity. Therefore, in addition to providing novel empirical support of sequential assessment models of animal contests that predict contest escalation with increasing resource quality, this study is one of a few to show that tools used to mitigate habitat loss can negatively impact reproductive fitness in a threatened species. 相似文献
102.
Albrecht?I.?Schulte-HosteddeEmail author John?S.?Millar 《Behavioral ecology and sociobiology》2004,55(3):272-277
Comparative analyses have found that relative testis size is a strong predictor of the prevalence of sperm competition for many taxa, including mammals, yet underlying this pattern is the assumption that intraspecific variation in testis size is related to individual fitness. Because intraspecific variation in ejaculate investment underlies interspecific patterns, it is critical to understand the causes and consequences of intraspecific variation in ejaculate investment. We examined relationships between ejaculate investment (testis size and sperm length) and reproductive success, body size and condition in the yellow-pine chipmunk (Tamias amoenus), a small ground squirrel in which sperm competition occurs. We examined genetic estimates of male reproductive success from a wild population of yellow-pine chipmunks and determined that males with large testes had higher annual reproductive success than males with small testes. This result provides empirical support for the numerous comparative studies that indicate testis size is associated with the intensity of sperm competition. In addition, males in good condition had relatively larger testes than males in poor condition, but there was no evidence of sperm length being dependent on condition. Finally, contrary to many predictions, males that invested more in sperm production (relatively heavy testes) produced shorter sperm, not longer sperm, than males that invested less.Communicated by P.M. Kappeler 相似文献
103.
Relatively high strontium concentrations and their isotopic composition in Roman glass of the Imperial period indicate the
general use of shells as carbonate raw material. Lead, iron, and barium concentrations and lead isotopes of glass of the late
fourth century from Hambach and Gellep (western Germany) are conformable with the use of glass sand from Eifel rivers. Each
of three pairs of six simultaneously operating Roman glasshouses in the Hambach area made its own raw glass from different
quartz sands.
Received: 2 July 1999 / Accepted in revised form: 13 December 1999 相似文献
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Professor A. Kohlschütter R. Rauskolb H. H. Goebel I. Anton-Lamprecht R. Albrecht H. Klein 《黑龙江环境通报》1989,9(4):289-292
In a family with two children affected by juvenile neuronal ceroid lipofuscinosis (JNCL) an attempt was made at the prenatal diagnosis of the disorder. The following tissues from the fetus at risk were investigated by electron microscopy and were found to be free of fingerprint profiles and curvilinear bodies, typical for JNCL: uncultivated amniotic fluid cells, lymphocytes isolated from fetal blood, and fetal skin biopsy specimens. The child was born at the 34th week of gestation and was clinically normal at the age of 15 months. Postnatally, lymphocytes (isolated at the age of 6 and 15 months) and skin tissue (taken at the age of 15 months) were found to be morphologically normal. It is highly unlikely that the child is affected but definite proof of the absence of JNCL remains difficult at this age. 相似文献
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