Variation in Reproductive Success Across Captive Populations: Methodological Differences, Potential Biases and Opportunities

Our understanding of fundamental organismal biology has been disproportionately influenced by studies of a relatively small number of model\u27 species extensively studied in captivity. Laboratory populations of model species are commonly subject to a number of forms of past and current selection that may affect experimental outcomes. Here, we examine these processes and their outcomes in one of the most widely used vertebrate species in the laboratory - the zebra finch (Taeniopygia guttata). This important model species is used for research across a broad range of fields, partly due to the ease with which it can be bred in captivity. However despite this perceived amenability, we demonstrate extensive variation in the success with which different laboratories and studies bred their subjects, and overall only 64% of all females that were given the opportunity, bred successfully in the laboratory. We identify and review several environmental, husbandry, life-history and behavioural factors that potentially contribute to this variation. The variation in reproductive success across individuals could lead to biases in experimental outcomes and drive some of the heterogeneity in research outcomes across studies. The zebra finch remains an excellent captive animal system and our aim is to sharpen the insight that future studies of this species can provide, both to our understanding of this species and also with respect to the reproduction of captive animals more widely. We hope to improve systematic reporting methods and that further investigation of the issues we raise will lead both to advances in our fundamental understanding of avian reproduction as well as to improvements in future welfare and experimental efficiency

Experimental Investigation on Characteristics of High-Speed Milling of 6061 Aluminum Alloy

高速切削是一種利用淺切深、高速進給和高切削速度的方式進行加工，不但可以大幅降低加工成本與時間外，並有熱變形小與切削力低的優點。本文首先針對文獻不足處進行刀刃運動路徑分析，並推導出切屑形狀、切削力和側銑表面粗糙度之理論模式；另外以輕合金加工所常用之6061-T651鋁合金進行實驗，文中以田口實驗設計法規劃面銑、槽銑和側銑三種銑削方式進行實驗驗證與製程最佳化參數之探討，除了將所獲取的銑削力和銑削動力以及表面粗糙度進行探討外，並根據表面粗糙度與銑削力的品質特性，提供最佳的製程參數組合。 本研究透過MAKINO-A55工具機進行實驗，實驗結果發現，表面粗糙度實驗值與理論值有所差異，面銑為1.2-3倍，槽銑為10-12倍，而側銑則為20倍左右；同時亦發現高速切削的確可得到相當優異的表面，如面銑Ra <0.5m，槽銑Ra <2m，而側銑Ra <0.4m。又經田口法分析後，當面銑之刀具直徑愈大時，則表面品質下降；而表面品質最佳的製程參數組合是每刃進給0.06mm/tooth、切削速度850m/min、切削深度0.2mm、刀具直徑50mm、切削寬度與刀具直徑比為70%；而在銑削深度0.2mm時銑削力最小，此與表面粗糙度的最佳參數表現不謀而合。另槽銑實驗則發現每刃進給影響最大，較小的進給量可以獲得較佳的表面；至於最佳表面粗糙度的製程參數組合為每刃進給0.035mm/tooth、切削速度410m/min、切削深度0.1mm和刀具直徑16mm。側銑表面粗糙度最佳參數組合則為每刃進給0.035mm/tooth、切削速度360m/min、切削深度8mm、切削寬度0.3mm和刀具直徑20mm，其中影響最大的因子亦為每刃進給。 再者，當切深愈大時，除了銑削力相對增大外，刃口積屑緣的情形也會相對增加。另以頻譜分析亦發現表面粗糙度與銑削力之頻譜相當契合，此現象應值得再深入探討。High-speed cutting (HSC) is a machining method with low cutting depth, high feed rate and high cutting speed. It takes the advantages of lower machining time and cost as well as low thermal deformation and low cutting force. This thesis first analyzes the trajectory of a cutting edge and then drives the shape of chips, cutting force and surface roughness base on the trajectory. Experiments using the commonly used aluminum alloy 6061-T651 on a MAKINO-A55 machine tool is then designed and conducted to verity the surface roughness and to find the process parameters for best surface roughness. Experiments are designed by the Taguchi method in order to minimize the number of experiments. The result shows the real surface roughness is higher than the ideal one from 1.2 to 3 times for face milling; 10 to 12 times for slot milling and about 20 times worse for side milling. It also shows good surface finish can be easily achieved by HSC, for example, Ra<0.5m for face milling; Ra<2m for slot milling, and Ra<0.4m for side milling. Process parameters for best surface roughness are allocated based on the ANOVA (ANalysis Of VAriance) and the S/N (Signal to Noise) ratio. It is found that the tool diameter plays as the most important factor in face milling. The surface quality become worse as it increases. Minimum cutting force is obtained at depth of cut being 0.2mm which is consistent with the best surface finish. The feed per cutting edge, on the other hand, has been found as the most affective factor in slot milling and in side milling. Better surface finish can be achieved by reducing feed per cutting edge. Analysis of experimental data further finds that cutting forces and built-up edges increase as the depth of cut increases. Moreover, it is also found strong co-relation between the surface roughness and cutting force from frequency spectrum. This phenomenon is worthy of further investigation.第一章 緒論 1.1 緣起 1.2 文獻回顧 1.3 研究方法 1.4 本文大綱 第二章 切削分析 2.1 銑削刀刃運動分析 2.2 銑削力分析 2.3 銑削動力分析 2.4 表面粗度分析 2.5 移除率與加工時間計算 2.6 理論式在高速銑削之適用性探討 第三章 高速銑削實驗設計與架設 3.1 田口實驗設計法簡介 3.1.1 高速銑削實驗規劃程序 3.2 實驗系統架設 3.3 實驗量測設備 第四章 實驗結果與分析 4.1 高速面銑削 4.1.1 表面粗度量測結果與分析 4.1.2 表面粗度變異數分析 4.1.3 面銑表面粗度驗證實驗 4.1.4 銑削力量測結果與分析 4.1.5 銑削力變異數分析 4.1.6 高速面銑之銑削行為分析與探討 4.2 高速端銑削-槽銑 4.2.1 表面粗度量測結果與分析 4.2.2 表面粗度變異數分析 4.2.3 端槽銑表面粗度驗證實驗 4.2.4 銑削力量測結果與分析 4.2.5 銑削力變異數分析 4.2.6 高速端-槽銑之銑削行為分析與探討 4.3 高速端銑削-側銑 4.3.1 表面粗度量測結果與分析 4.3.2 表面粗度變異數分析 4.3.3 端側銑表面粗度驗證實驗 4.3.4 銑削力量測結果與分析 4.3.5 銑削力變異數分析 4.3.6 高速端-側銑之銑削行為分析與探討 4.4 實驗觀察建議 第五章 結論與未來展望 5.1 結論 5.2 未來展望 參考文獻 附錄A 表面粗度相關理論推導 附錄B 銑削模擬系統建構 附錄C 刀具條件參考值 附錄D 實驗系統設備規格 附錄E 實驗量測設備規格 附錄F 表面粗度之量測準則 附錄G 銑削實驗之數控程式碼 附錄H 實驗條件與平均銑削力週期分佈關係圖 作者簡

Vocal negotiation over parental care? Acoustic communication at the nest predicts partners' incubation share

International audienceIn species with biparental care, individuals adjust their workload to that of their partner to either compensate or match its investment. Communication within a pair might be crucial for achieving this adjustment. Zebra finches, Taeniopygia guttata, form life-long monogamous pair bonds, in which partners are highly coordinated and both incubate the eggs. When relieving each other during incubation, partners perform a structured call duet at the nest. If this duet functions to coordinate incubation workload, disrupting the pair's usual nest-relief pattern by delaying the male's return to the nest should affect the structure of the duet. Using domesticated birds breeding in a large aviary, we found that delaying the male's return induced shorter duets with higher call rates. In addition, we tracked the location of individuals with a transponder at the nest and the feeder, and showed that these accelerated duets were associated with an increased haste of the partners to take turns incubating and foraging. Females also spent less time incubating during their subsequent shift, and females' time off-nest was best predicted by their mate's calling behaviour in the previous duet. Taken together, these results suggest that duets may function as ‘vocal negotiation’ over parental care

Incubating females signal their need during intrapair vocal communication at the nest : a feeding experiment in great tits

International audienceParental care is a key factor of breeding success and parents face evolutionary trade-offs between investment in current offspring and future reproduction and survival. Incubation in birds is energetically costly and the balance between parental and offspring's energetic needs is especially challenging when only one sex incubates, generally the female. In that case, males can contribute indirectly to incubation effort by feeding their mate and females may use begging behaviours to signal their needs to their visiting partner. The great tit, Parus major, is a good model species to test whether females use acoustic communication from the nest to signal their needs to their mate outside because females interact vocally with their mate during incubation. To test whether females use these vocal exchanges to communicate how hungry they are, great tit pairs were recorded on 2 days during incubation: 1 day with a feeder of mealworms in the nestbox and 1 day with an empty feeder. First, food supplementation increased females' nest attentiveness, revealing a decrease in foraging activity and consequently in females' needs. Second, females signalled their need for food both during their male's visits inside the nest but also during the vocal exchange immediately preceding the male's entrance by calling more and by modifying the frequency spectrum of their calls. So females' calling behaviour is an honest signal of need not only during their male's visits, but also before his entrance in the nest

Acoustic communication in zebra finches signals when mates will take turns with parental duties

International audienceBi-parental care may involve both cooperation and conflict between parents. Parents adjust their workload to that of their partner and this ability is likely to affect reproductive success. Whether mates communicate, either to resolve the sexual conflict or to coordinate their joint investment in parental care is a largely unaddressed question which we examined by recording wild zebra finches at the nest during incubation. Zebra finch (Taeniopygia guttata) partners produce vocal exchanges at the nest that can be characterized as duets. Some duets end in nest-relief (when birds take turns incubating and foraging) but some do not (when the foraging mate vocally interacts with its incubating partner by coming inside or in the vicinity of the nest). Our data indicate that the structure of the duet predicted its outcome (relief or not), with a parent calling differently before leaving or staying in the nest by modifying its vocal repertoire as well as the acoustic structure of one particular call type which is typically used inside the nest. Zebra finch partners may thus exchange on the time to take turns with parental duties. Our results show that acoustic communication between partners might be of importance in the organization of parental care and could help in understanding sexual conflict resolution or cooperation phenomena in future studies

Physiological resonance between mates through calls as possible evidence of empathic processes in songbirds

International audiencePhysiological resonance –where the physiological state of a subject generates the same state in a perceiver – hasbeen proposed as a proximate mechanism facilitating pro-social behaviours. While mainly described in mammals,state matching in physiology and behaviour could be a phylogenetically shared trait among social vertebrates.Birds show complex social lives and cognitive abilities, and their monogamous pair-bond is a highlycoordinated partnership, therefore we hypothesised that birds express state matching between mates. Weshow that calls of male zebra finches Taeniopygia guttata produced during corticosterone treatment (after oraladministration of exogenous corticosterone and during visual separation from the partner) provoke both an increasein corticosterone concentrations and behavioural changes in their female partner compared to controlcalls (regular calls emitted by the same male during visual separation from the partner only), whereas calls producedduring corticosterone treatment by unfamiliar males have no such effect. Irrespective of the caller status(mate/non-mate), calls' acoustic properties were predictive of female corticosterone concentration after playback,but the identity of mate calls was necessary to fully explain female responses. Female responses were unlikelydue to a failure of the call-based mate recognition system: in a discrimination task, females perceive callsproduced during corticosterone treatment as being more similar to the control calls of the samemale than to controlcalls of other males, even after taking acoustical differences into account. These results constitute the first evidenceof physiological resonance solely on acoustic cues in birds, and support the presence of empathicprocesses

Interactive vocal communication at the nest by parent Great Tits Parus major

International audienceAlthough most bird species show monogamous pair bonds and bi-parental care, little is known of how mated birds coordinate their activities. Whether or not partners communicate with each other to adjust their behaviour remains an open question. During incubation and the first days after hatching, one parent – generally the female – stays in the nest for extended periods, and might depend on acoustic communication to exchange information with its mate outside. The Great Tit Parus major is an interesting study system to investigate intra-pair communication at the nest because males address songs to their mate while she is in the nest cavity, and females answer the male from the cavity with calls. However, the function of this communication remains unknown. In this study, we recorded the vocalizations and observed the resulting behaviour of Great Tit pairs around the nest at different breeding stages (laying, incubation and chick-rearing). We observed vocal exchanges (vocalization bouts, alternated on the same tempo, between the female inside the nest and her male outside) in three contexts with different outcomes: (1) the female left the nest, (2) the male entered the box with food, and the female then used specific call types, (3) mates stopped calling but did not leave or enter the nest. The structure of vocal exchanges was globally stable between contexts, but females used calls with an up-shifted spectrum during exchanges, at the end of which they left the nest or the male entered the nest. Birds vocalized more and at higher tempo during exchanges that ended up in feeding inside the nest. Birds also vocalized more during exchanges taking place during laying – a period of active mate guarding – than during incubation. We conclude that vocal exchanges could signal the females’ need for food and the males’ mate guarding behaviour, and discuss other possible functions of this communication

Variation in reproductive success across captive populations: methodological differences, potential biases and opportunities

Our understanding of fundamental organismal biology has been disproportionately influenced by studies of a relatively small number of ‘model’ species extensively studied in captivity. Laboratory populations of model species are commonly subject to a number of forms of past and current selection that may affect experimental outcomes. Here, we examine these processes and their outcomes in one of the most widely used vertebrate species in the laboratory – the zebra finch (Taeniopygia guttata). This important model species is used for research across a broad range of fields, partly due to the ease with which it can be bred in captivity. However despite this perceived amenability, we demonstrate extensive variation in the success with which different laboratories and studies bred their subjects, and overall only 64% of all females that were given the opportunity, bred successfully in the laboratory. We identify and review several environmental, husbandry, life-history and behavioural factors that potentially contribute to this variation. The variation in reproductive success across individuals could lead to biases in experimental outcomes and drive some of the heterogeneity in research outcomes across studies. The zebra finch remains an excellent captive animal system and our aim is to sharpen the insight that future studies of this species can provide, both to our understanding of this species and also with respect to the reproduction of captive animals more widely. We hope to improve systematic reporting methods and that further investigation of the issues we raise will lead both to advances in our fundamental understanding of avian reproduction as well as to improvements in future welfare and experimental efficiency