扁颅蝠与褐扁颅蝠的集群结构

2001—2002年在广西宁明县和龙州县利用直接观察、捕捉测量(共捕到197群蝙蝠,全捕180群)和标记重捕法(标记了31群的101只扁颅蝠,重捕到36只)比较研究了扁颅蝠(tylonycteris pachypusa)与褐扁颅蝠(T．robustula)的集群结构。结果发现：扁颅蝠与褐扁颅蝠主要栖宿在刺竹(Bambusa stenostachya)的竹筒内,通过竹筒上的裂缝进出。扁颅蝠栖宿的竹筒长平均为27．7cm,外围直径平均为23．6cm;褐扁颅蝠的分别为28．3cm和23．8cm。扁颅蝠栖宿群大小为1—24只,褐扁颅蝠栖宿群大小为1—13只;2种蝙蝠的栖宿群中皆为独居所占比例最大(扁颅蝠为22．30％,褐扁颅蝠为40．63％),2只所占比例次之(分别为14．87％和18．75％),其它大小类型呈不规则变化。扁颅蝠栖宿群的性别组成,以雌雄混居最常见(占54．72％),其次为独居雄性(占20．95％),而褐扁颅蝠栖宿群雌雄混居群与独居雄性所占比例相当(均为40．63％)。2种蝙蝠的雄性趋向于独居,而雌性趋向于群居。扁颅蝠与褐扁颅蝠可以栖宿在同一片竹林内,并且可以在不同时间轮流使用同一个栖宿竹筒,但2种蝙蝠从未共栖于同一个竹筒内。另外,标记重捕扁颅蝠发现：扁颅蝠经常变换栖宿竹筒(栖宿竹筒不固定);同时栖宿群之间经常发生个体交换[动物学报50(3)：326—333．2004]。     

扁颅蝠和褐扁颅蝠体表寄生革螨的宿主选择

该文通过野外调查和室内行为实验,研究了扁颅蝠(Tylonycteris pachypus)和褐扁颅蝠(T.robustula)与其体表寄生革螨(雷氏巨刺螨(Macronyssus radovskyi)及拟雷氏巨刺螨(M.pararadovskyi))之间的关系.在野外自然条件下,雌性扁颅蝠的体表寄生革螨负荷量与宿主健康指数呈正相关(Spearman:rs=0.55,P＜0.01,n=24),而在雄性扁颅蝠以及雌、雄褐扁颅蝠中则无相关性(P＞0.05).室内原宿主感染实验发现,扁颅蝠和褐扁颅蝠体表寄生革螨均明显倾向于选择各自的雄性宿主,扁颅蝠雌、雄性感染率分别为(42±12)％和(58±12)％(t=-3.6,df=31,P＜0.01);褐扁颅蝠雌、雄性感染率分别为(37±11)％和(63±11)％(t=-6.1,df=26,P＜0.001).用扁颅蝠体表寄生革螨(拟雷氏巨刺螨)对扁颅蝠与褐扁颅蝠交叉感染后发现,寄生革螨明显选择其原宿主扁颅蝠,扁颅蝠与褐扁颅蝠感染率分别为(71±13)％和(29±13)％(t=9.1,df=29,P＜0.001).以上结果表明,扁颅蝠和褐扁颅蝠的体表寄生革螨负荷量与宿主身体状态无明显相关性,而对宿主性别表现不同偏好;扁颅蝠的体表寄生革螨对宿主表现明显的专一性.     

繁殖期高原鼠兔的行为时间分配与后代存活率的关系

2002年4-8月份,在中国科学院海北高寒草甸生态系统定位站附近,采用标志流放、直接观察法和解剖法对青藏高原特有的植食性小哺乳动物———高原鼠兔(Ochotonacurzoniae)的行为时间分配、繁殖特征和后代存活率等方面进行了研究。结果表明,雌、雄成体平均地面活动时间占总时间的比例分别为88.67%和89.88%,在不同的繁殖时段,成体的各种行为时间分配存在显著的变化,并影响后代的存活率。幼体从出生到15d的存活率和雌、雄性成体的每次移动距离以及雌性成体的地面活动强度都显著的正相关;从15d到45d的存活率和雄性成体的地面活动强度、观望强度显著的正相关。在相同的观察时期,高原鼠兔雌、雄成体的一些行为时间分配存在显著差异,如雄性成体地面移动距离、频次在繁殖前期显著的高于雌性成体;雄性成体的观望强度在6、7月份显著高于雌性成体。说明雄性成体在领域防卫中较雌性成体承担更多的责任,雌、雄成体在育幼活动中的繁殖投入存在互补性。     

圈养大熊猫体重的变化规律

对中国大熊猫保护研究中心219只圈养大熊猫的体重进行分析,发现圈养大熊猫初生幼仔的体重为(0.16±0.04)kg,其与母兽的体重相关性不显著;幼仔期平均体重为(13.74±10.64)kg;亚成体期平均体重为(78.30±27.05)kg;成年个体平均体重为(112.25±12.04)kg;老年个体平均体重为(100.75±15.79)kg。初生幼仔体重雌、雄间无显著差异(P0.05);幼仔、亚成体、成年及老年个体的大熊猫,雌性个体体重均小于雄性个体(P0.05)。雌、雄大熊猫幼仔生长曲线均接近幂函数(Power),雌性亚成体大熊猫体重增长曲线接近三次方(Cubic)函数,雄性亚成体大熊猫体重增长曲线则呈S型;无论雌性和雄性,幼仔和亚成体期间均保持线性增长(P0.05)。成年大熊猫体重的年度和季节间无显著差异(P0.05),但进入成年后期时体重会下降。进入老年期后,雄性大熊猫的体重在后期有显著性下降(P0.001)。本研究补充完善了大熊猫整个生活史的体重增长规律,为大熊猫迁地保护中饲养管理措施的制定提供了参考依据。     

不同性别和年龄的大仓鼠对黄鼬气味的反应

将雌性成体和雌雄亚成体大仓鼠 (Cricetulustriton)长期 (4周 )暴露给过量的黄鼬 (Mustelasibirica)肛腺分泌物 ,观察其行为和生理状态的变化 ,并通过与我们以前有关黄鼬气味对成年雄鼠影响的研究结果进行比较 ,表明黄鼬气味对不同性别和不同年龄大仓鼠的胁迫效应和生殖抑制存在差异。发现黄鼬气味对雌性大仓鼠的影响较雄性小 ,对亚成体的影响较成体小 ,这与雌性和未成年动物对各种胁迫因素的反应更敏感的普遍现象相反。在成年鼠中 ,雌雄鼠的攻击行为都受到黄鼬气味的抑制 ;但天敌气味使雌性的胁腺膨大 ,对胁腺标记和肾上腺大小无影响 ;成年雄鼠的肾上腺膨大 ,胁腺萎缩 ,标记减少。在亚成体中 ,除了雄性胁腺受到抑制(与成年雄鼠相同 )外 ,雌雄鼠的肾上腺和雌性的胁腺未受影响。亚成体实验鼠的体重都比对照组低 ,但成年鼠的体重未受影响。另外 ,与以往对其它鼠类的研究结果一致 ,天敌气味并不影响成年鼠的生殖器官 ,却抑制了未成年雄鼠的附睾和未成年雌鼠的子宫。这些差异可能和生理基础的性二态以及可能面临的被捕食风险大小有关     

蝘蜓头、体大小的两性异形和雌体繁殖

报道了蜓 (Sphenomorphusindicus)头、体大小的两性异形和雌性繁殖。性成熟雌体大于雄体。雄性成体头长大于雌性成体 ,但头宽与雌性成体无显著差异。初生幼仔的头长和头宽无两性差异。雄性幼体头长和头宽大于雌性幼体。设置SVL恒定时 ,雄性幼体和雄性成体的头长和头宽无显著差异 ,雌性幼体的头长和头宽大于雌性成体。初生幼仔具有相对较大的头部。产仔雌体的最小SVL为 6 7 7mm ,大于此SVL的雌体均年产单窝仔。平均窝仔数、窝仔重和幼仔重分别为 7 2 ( 3～ 11)、 3 34( 1 30～ 5 19)和 0 48( 0 36～ 0 5 8)g。用卵黄沉积卵巢卵和输卵管计数的窝仔数比用幼仔计数的窝仔数多约 1 0个后代。幼仔体重与雌体SVL无关。相对窝仔重与雌体SVL边缘性地呈正相关。窝仔数、窝仔重与雌体SVL呈正相关 ,幼仔体重与窝仔数呈负相关。窝仔数与雌体状态无关。     

可可西里地区藏羚的社群特征

藏羚(Pantholopshodgsoni)的集群类型有雌性群、雄性群、母仔群、雌雄混群和独羚5种形式。2002年7月～2003年12月,在可可西里地区沿青藏公路设立试验区,直接观察到936群次,计13795只次藏羚。藏羚的集群类型受到生育周期的影响,季节间差异显著。春季以雌性群(60.49%)和雄性群(30.86%)为主;夏季和秋季主要为雌性群(41.65%,49.66%)和母仔群(49.36%,33.67%);雌雄混群(58.14%)主要出现在冬季。雄性群在1年中很少见,尤其是夏秋两季,冬季较为常见,多由亚成体雄性组成。独羚是一种特殊的集群类型,占11.32%。常见的集群大小为2～20只,占71.90%,其次是21～200只的群,占16.35%;>200只的集群极少,仅占0.43%,且仅出现于夏季产羔往返迁徙途中。藏羚的集群大小受竞争、捕食风险以及迁徙繁殖的共同影响。藏羚的集群极不稳定,交配期雌雄混合群受雄性亚成体的干扰经常改变,而在迁徙季节大群和小群之间的转换也很频繁。大型集群为雌性群或母仔群,其最适集群大小为2～20只。     

yan蜓头、体大小的两性异形和雌体繁殖

报道了yan蜓(Sphenomorphus indicus)头、体大小的两性异形和雌性繁殖。性成熟雌体大于雄体。雄性成体头长大于雌性成体，但头宽与雌性成体无显著差异。初生幼仔的头长和头宽无两性差异。雄性幼体头长和头宽大于雌性幼体。设置SVL恒定时，雄性幼体和雄性成 体的头长和头宽无显著差异，雌性幼体的头长和头宽大于雌性成体。初生幼仔具有相对较大的头部。产仔雌体的最小SVL为67.7 mm，大于此SVL的雌体均年产单窝仔。平均窝仔数、窝仔重和幼仔重分别为7.2(3-11)、3.34(1.30-5.19)和0.48(0.36-0.58)g。用卵黄沉积卵巢卵和输卵管计数的窝仔数比用幼仔计数的窝仔数多约1.0个后代。幼仔体重与雌体SVL无关。相对窝仔重与雌体SVL边缘性地呈正相关。窝仔数、窝仔重与雌体SVL呈正相关，幼仔体重与窝仔数呈负相关。窝仔数与雌体状态无关。     

五种蝙蝠形态与回声定位叫声的性别差异

为研究角菊头蝠(Rhinolophus cornutus)、三叶蹄蝠(Aselliscus uheeleri)、大蹄蝠(Hipposideros armiger)、大鼠耳蝠(Myotis myotis)和大足鼠耳蝠(M．riketti)的形态和回声定位叫声的性别差异性,明确同种蝙蝠雌雄个体对食物、栖息地等资源利用的细微差异,我们利用超声波探测仪、Batsound分析软件及SPSS11．0统计软件对5种95只蝙蝠进行了录音、声波分析和统计分析。5种蝙蝠形态性别差异性不显著,角菊头蝠、三叶蹄蝠、大蹄蝠和大足鼠耳蝠叫声频率性别差异性显著,大鼠耳蝠叫声频率性别差异性不显著。角菊头蝠雌性叫声的基频、分音、主频率高于雄性,声脉冲时间、间隔时间大于雄性,调频(FM)带宽小于雄性;三叶蹄蝠、大蹄蝠叫声的基频、主频率雄性高于雌性,调频带宽雌性小于雄性;大足鼠耳蝠叫声的主频率雄性高于雌性,FM带宽雌性大于雄性[动物学报49(6)：742～747,2003]。     

广州市犬蝠对栖息地的选择

2006年9月-2007年3月,在广州市区对犬蝠(Cynopterus sphinx angulatus)的分布和栖息地的选择进行了研究.结果表明:共发现犬蝠栖巢45个,有犬蝠栖息的26个;犬蝠对栖息植物的选择具有专一性,主要利用景观树蒲葵(Livistona chinensis)的叶片建造栖巢,其栖息地跟人类活动区域高度重合.捕获的18个栖群中5个栖群为全捕,13个栖群有部分个体未捕获;其中17个栖群中包括有雄性个体,占群体总数的94%;5个全捕栖群中,2个为一雄多雌,一个为一雄一雌群体,一个为独栖雄性,另一个为多个雄性的"单身汉群体".     

Genetic population structure of the white sifaka (Propithecus verreauxi verreauxi) at Beza Mahafaly Special Reserve,southwest Madagascar (1992-2001)

Gene flow within and between social groups is contingent on behaviourally mediated patterns of mating and dispersal. To understand how these patterns affect the genetic structure of primate populations, long-term data are required. In this study, we analyse 10 years of demographic and genetic data from a wild lemur population (Propithecus verreauxi verreauxi) at Beza Mahafaly Special Reserve, southwest Madagascar. Our goal is to specify how patterns of mating and dispersal determine kinship and genetic diversity among animals in the population. Specifically, we use microsatellite, parentage, and census data to obtain estimates of genetic subdivision (FST), within group homozygosity (FIS), and relatedness (r) within and among social groups in the population. We analyse different classes of individuals (i.e. adults, offspring, males, females) separately in order to discern which classes most strongly influence aspects of population structure. Microsatellite data reveal that, across years, offspring are consistently more heterozygous than expected within social groups (FIS mean = -0.068) while adults show both positive and negative deviations from expected genotypic frequencies within groups (FIS mean = 0.003). Offspring cohorts are more genetically subdivided than adults (FST mean = 0.108 vs. 0.052) and adult females are more genetically subdivided than adult males (FST mean = 0.098 vs. 0.046). As the proportion of females in social groups increases, the proportion of offspring sired by resident males decreases. Offspring are characterized by a heterozygote excess as resident males (vs. nonresident males) sire the majority of offspring within groups. We link these genetic data to patterns of female philopatry, male dispersal, exogamy, and offspring sex-ratio. Overall, these data reveal how mating and dispersal tactics influence the genetic population structure in this species.     

Social organization of the Asian elephant (Elephas maximus) in southern India inferred from microsatellite DNA

Social organization of the Asian elephant (Elephas maximus) is not well understood in the absence of long-term studies of identified individuals. Adult Asian elephant females and their young offspring of both sexes form matriarchal groups, with pubertal males dispersing from natal groups, but whether these social groups represent families and whether males show locational or social dispersal were unknown. Using nuclear microsatellite loci amplified from dung-extracted DNA of free-ranging elephants in a large southern Indian population, we demonstrate that female-led herds comprise closely related individuals that are indeed families, and that males exhibit non-random locational dispersal.     

Proximate and ultimate causes of natal dispersal in the great bustard Otis tarda

Between 1991 and 1997 we studied the offspring independenceand juvenile dispersal in a wild population of great bustards(Otis tarda). Young males were independent and began their juveniledispersal at an earlier age (6–11 months) than young females(8–15 months). The juvenile dispersal period was longerand the distances reached farther in males than in females.Natal dispersal distances were also longer in males, all ofwhich dispersed from their natal areas and established as adultsat 5–65 km from their natal nests. In contrast, most femaleswere strongly philopatric, settling at 0.5–5 km from theirnatal nests. These marked sex differences in offspring independenceand dispersal may have evolved originally to maintain geneticdiversity and are probably reinforced through male competitionfor mates. Young males that had fed at higher rates and receivedmore feedings from their mothers during the early maternal dependenceperiod became indepthdent and tended to disperse earlier. Theyalso integrated earlier into adult male flocks and settled earlierat their definitive leks, which were closer to their natal sites,in areas of higher adult male density. None of these correlationswas found among young females. These results suggest that enhancedfood intake and maternal care of male offspring are vitallyimportant in increasing their competitive ability during theimmature period and probably also in their fitness as breedingadults. These results are in accordance with the selective valueof large size in males and suggest how this species might havereached such a marked sexual dimorphism in size.     

Parentage analysis detects cryptic precapture dispersal in a philopatric rodent

Locating birthplaces using genetic parentage determination can increase the precision and accuracy with which animal dispersal patterns are established. We re-analyse patterns of movement away from the birthplace as a function of time, sex and population density for a sample of 303 banner-tailed kangaroo rats, Dipodomys spectabilis. We located birth sites using a combination of likelihood-based parentage analysis with live-trapping of mothers during the breeding season. The results demonstrate that natal-breeding site distances are density dependent in this species; in particular, both sexes emigrate earlier in the year, and females disperse farther than males, at low population densities. Banner-tailed kangaroo rats were chosen as a study system because live-trapping easily detects maternal and offspring locations; nevertheless, parentage analysis reveals that some offspring evade early detection and move substantial distances before their first capture. In a few cases, the approach even detects dispersal out of the natal 'deme' prior to first capture. Parentage analysis confirms the extreme philopatry of both sexes but indicates that prior estimates of median dispersal distance were too low. For D. spectabilis, more accurate location of individual birthplaces clarifies patterns of sex bias and density dependence in dispersal, and may resolve apparent discrepancies between direct and indirect estimates of dispersal distance. For species in which mothers can be more reliably trapped than juveniles, using offspring genotypes to locate parents is a novel way that genetic techniques can contribute to the analysis of animal dispersal.     

No evidence for female kin association,indications for extragroup paternity,and sex‐biased dispersal patterns in wild western gorillas

Characterizing animal dispersal patterns and the rational behind individuals’ transfer choices is a long‐standing question of interest in evolutionary biology. In wild western gorillas (Gorilla gorilla), a one‐male polygynous species, previous genetic findings suggested that, when dispersing, females might favor groups with female kin to promote cooperation, resulting in higher‐than‐expected within‐group female relatedness. The extent of male dispersal remains unclear with studies showing conflicting results. To investigate male and female dispersal patterns and extragroup paternity, we analyzed long‐term field observations, including female spatial proximity data, together with genetic data (10 autosomal microsatellites) on individuals from a unique set of four habituated western gorilla groups, and four additional extragroup males (49 individuals in total). The majority of offspring (25 of 27) were sired by the group male. For two offspring, evidence for extragroup paternity was found. Contrarily to previous findings, adult females were not significantly more related within groups than across groups. Consistently, adult female relatedness within groups did not correlate with their spatial proximity inferred from behavioral data. Adult females were similarly related to adult males from their group than from other groups. Using R _ST statistics, we found significant genetic structure and a pattern of isolation by distance, indicating limited dispersal in this species. Comparing relatedness among females and among males revealed that males disperse farer than females, as expected in a polygamous species. Our study on habituated western gorillas shed light on the dispersal dynamics and reproductive behavior of this polygynous species and challenge some of the previous results based on unhabituated groups.     

The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal

Dispersal is nearly universal; yet, which sex tends to disperse more and their success thereafter depends on the fitness consequences of dispersal. We asked if lifetime fitness differed between residents and immigrants (successful between‐population dispersers) and their offspring using 29 years of monitoring from North American red squirrels (Tamiasciurus hudsonicus) in Canada. Compared to residents, immigrant females had 23% lower lifetime breeding success (LBS), while immigrant males had 29% higher LBS. Male immigration and female residency were favoured. Offspring born to immigrants had 15–43% lower LBS than offspring born to residents. We conclude that immigration benefitted males, but not females, which appeared to be making the best of a bad lot. Our results are in line with male‐biased dispersal being driven by local mate competition and local resource enhancement, while the intergenerational cost to immigration is a new complication in explaining the drivers of sex‐biased dispersal.     

Social and ecological influences on dispersal and philopatry in the plateau pika (Ochotona curzoniae)

Benefits and costs of dispersal and philopatry of the socialplateau pika (Ochotona curzoniae) were studied on the Tibetanplateau for 3 years. Although short-lived, plateau pikas livein cohesive family groups that occupy burrow systems in sedgemeadow habitat Most (57.8%) plateau pikas were philopatric,and dispersal movements were extremely restricted. No juvenilefemales or adult pikas moved more than two family ranges betweenyears; the greatest observed dispersal distances were by twojuvenile males that moved five family ranges from the familyof their birth. Traversing unfamiliar habitat was not a costof pika dispersal because most dispersers settled in familiesthat they could easily visit before dispersal. Dispersal movementsappeared to result in equalization of density among pika families,an expected result if competition for environmental resourcesinfluenced dispersal. Males did not disperse to gain advantagesin competition for mates, as evidenced by their moving to familieswith significantly fewer females. Females, however, moved tofamilies with significantly more males. Males provide abundantpaternal care, and significantly more offspring per female survivedto become adults from families with more adult males per adultfemale. Evidence concerning the influence of inbreeding avoidanceon natal dispersal was indirect. Some males exhibited natalphilopatry; thus some families had opportunity for dose inbreeding.Males and females that dispersed had no opposite-sex relativesin their new families. Philopatric pikas may have benefitedby remaining in families that exhibited low local densities,and philopatric females might have benefited from social cooperationwith relatives.     

Mother-offspring interactions affect natal dispersal in a lizard

Interactions between relatives operate strong selective pressures on dispersal. Recently, a correlative study in the common lizard (Lacerta vivipara) suggested that natal dispersal might respond plastically to mother-offspring interactions. Here, we describe a factorial experiment supporting this observation. Two crossed treatments were applied to experimental patches of the common lizard: (i) presence versus absence of the mother, inducing a difference of kinship in offspring neighbourhoods; and (ii) high versus low patch density, resulting in two levels of conspecific abundance and modulating the effect of mother presence on the average kinship within a patch. Dispersal of the same cohort of offspring was observed at the juvenile and yearling stages. We found a sex-dependent response of offspring dispersal to the removal of the mother at the two stages. During the juvenile stage, higher dispersal was found in females in the presence of the mother, with males unaffected. During the yearling stage, the responses of both sexes to the presence of the mother opposed each other. In addition, we found a negative relationship between dispersal and patch density at the juvenile stage. No interaction between density and the presence of the mother was detected, which suggests that behavioural responses to kinship and density are disconnected and that kinship is assessed at a small social scale. We discuss the role of competition and inbreeding avoidance to explain the observed pattern.     

Socioecological factors of male chimpanzee migration at Bossou, Guinea

For more than 21 years a small semi-isolated group of wild chimpanzees have been studied at Bossou, Guinea, west Africa. All individuals have been identified since the beginning of the study. Remaining rates of infants (0–3 yr) and juveniles (4–7 yr) in the group were 64–80% for both sexes, however, those of adolescents (8–11 yr) dropped drastically, particularly for males (14%). As a result, most natal males as well as females disappeared before fully maturing. Two male visitors and an immigrant were observed in the group. More adult males than females disappeared from Bossou. Group males could be excluded as the genetic father of an offspring born in the group. From these demographic trends it is highly likely that some of these males emigrated rather than succumbed to sickness and death. It seems likely that they left on their own by choice. The reason for male dispersal is hypothesized to be influenced by intra-group male-male competition and the habitat ecology and structure of Bossou. There are no competitive adjacent groups or predators to prevent males from living alone and males can sire offspring out of their natal group.     

Microhabitat heterogeneity influences offspring sex allocation and spatial kin structure in possums

1. Sex allocation theory predicts that where dispersal is sex biased, the fitness consequences of producing male or female offspring are mediated by resource availability and maternal competitive ability. Females in poorer condition are expected to favour dispersing offspring to minimize resource competition with kin. Environmental heterogeneity may drive spatial variation in sex allocation through resource competition-related benefits to females and territory quality benefits to dispersing or philopatric offspring. 2. Here, we demonstrate that microhabitat heterogeneity can drive extremely fine-scale spatial heterogeneity in offspring sex allocation. Female bobucks (Trichosurus cunninghami) in temperate rainforest were more likely to produce male offspring than those in surrounding Eucalyptus forest. 3. A maternal physiological effect was identified, in that females of lower body mass were more likely to produce male offspring. This finding is consistent with resource competition predictions, in that smaller females are expected to have poorer competitive ability. 4. Genetic spatial autocorrelation analysis identified males as the more dispersing sex. Furthermore, overproduction of males by mothers in the rainforest habitat was geographically concordant with reduced philopatry, as inferred from spatial genetic analysis. This provides empirical validation of dispersal-related explanations of offspring sex allocation: that production of offspring of the dispersing sex minimizes the potential for resource competition with kin. 5. Spatial variation in dispersal via sex allocation responses to environmental heterogeneity can potentially contribute to spatial patterns in population dynamics.