DIEL VARIATION IN ECHOLOCATION BEHAVIOR OF WILD HARBOR PORPOISES

The echolocation rate and behavior of wild harbor porpoises were studied using a harbor porpoise click detector (POD) deployed close to the bottom at 40 m depth in Scottish waters, UK, April—June 2001. Echolocation variables were compared among four diel phases; morning, day, evening, and night. The echolocation encounter rate, the minimum interclick interval per train, and the proportion of echolocation click trains with a minimum interclick interval below 10 msec were all significantly higher at night than during the day. The variation in echolocation rate implies that porpoises increased their echolocation rate and/or visited the depth of the POD more often at night than during the day. Further, the changes in minimum interclick interval per train suggest that they used their echolocation for foraging or investigating objects at a close range to a higher extent, and acoustically explored the environment at greater distances at night than during the day.     

四川南充市夜鹭的巢址选择

2006年3~6月,在四川省南充市太和保护区对夜鹭的巢址选择进行了研究。野外调查了夜鹭巢47个,对照样方26个,通过主成分分析和对比分析,表明影响夜鹭巢址选择的主要因子依次为:营巢树高度、植被平均高度、巢高、竹平均直径、隐蔽度、巢上方盖度、距水(西河)距离、距白鹭巢距离、植被盖度、巢下盖度。     

Red deer <Emphasis Type="Italic">Cervus elaphus</Emphasis> resting place characteristics obtained from differential GPS data in a forest habitat

We recorded 30 24-h monitoring periods with 10-min sampling intervals on seven (three female; four male) Global-Positioning-System-collared adult free-ranging red deer (Cervus elaphus), from June 1999 to December 2000, in the Parc National des Cévennes, France. We observed the duration of resting bouts (n = 385) and then microhabitat variables (aspect, slope, presence of edge and litter, visibility, abundance of vegetation consumed or not) at 178 resting places. Resting bouts were shorter during the night than during the day from June to October but did not vary between sexes. Resting place visibility was lower during the day, especially in August. Daytime resting places generally offered more litter. Females used steeper slopes than males. We found higher variability in visibility and slope during the night. Aspect used did not vary from month to month or between day and night. Observed differences between day and night resting place characteristics suggest that red deer were probably facing a tradeoff between feeding and cover. Use of cover prevailed during the daytime whereas night resting place characteristics were more variable, indicating less constrained behaviour. Thus, cover (as a protection from disturbance), as well as food, is an important factor in red deer habitat use (at least during the day in disturbed areas) and should not be neglected in forest carrying capacity management.     

Herders' Perceptions, Practice, and Problems of Night Grazing in the Sahel: Case Studies from Niger

A survey was conducted from February to June of 1997 among livestock herders in two villages of Niger, Kodey and Toukounous, on their perceptions, practice, and problems of night grazing. Cattle and sheep were the species that were taken out for night grazing by the herders. Small herd size and labor constraints were mentioned as the principal reasons for not practicing night grazing. Major benefits of night grazing included good body condition, herd growth, increased milk production, prevention of diseases, and reduction in herd mortality. Insecurity, difficulty in staying awake at night, labor constraints, and damage to crops by animals were given as problems of night grazing. According to the herders, grazing time (duration) during the day and night was shorter in the wet season than in the dry season. In the wet season animals were herded (followed and closely supervised by herders), whereas in the dry season, animals were mostly left to range freely in both villages. In general, children herded the animals during the day, while adults were responsible for night-time herding. Herders' perceptions on night grazing as regards animal production parameters such as weight development, water consumption, fecal output and feeding behavior are consistent with available experimental results. Therefore, future technical research needs to recognize the constraints faced by herders and determine how to overcome them to improve technical and economic efficiency.     

Nocturnal activity in the cathemeral red-fronted lemur (Eulemur fulvus rufus), with observations during a lunar eclipse

Several ecological and physiological factors have been suggested to structure circadian activity in cathemeral primates, i.e., those that are regularly active both day and night, but their relative importance remains controversial. We studied the nocturnal activity of a group of cathemeral redfronted lemurs (Eulemur fulvus rufus) in Kirindy Forest in Western Madagascar to examine its relationship with one environmental factor, ambient light levels, in detail. To this end, nightly travel distances and moon luminosity were determined between March and June 1996. During this transitional period between the wet and dry seasons these red-fronted lemurs were regularly active at night, and traveled significantly larger distances during full-moon nights compared to new-moon nights. The importance of ambient luminosity for nocturnal activity was highlighted by observations during a total lunar eclipse (i.e., during a full-moon night), which caused abrupt cessation of the animal's activity. Our results support the hypothesis that nocturnal activity of these cathemeral lemurs is regulated also by changes in ambient light levels.     

Dive types and circadian behaviour patterns of Saimaa ringed seals<Emphasis Type="Italic">Phoca hispida saimensis</Emphasis> during the open-water season

Diving and circadian behaviour patterns of 7 free-ranging Saimaa ringed sealsPhoca hispida saimensis Nordquist, 1899 were examined by VHF-radiotelemetry during open-water seasons between May and November in Lake Saimaa, eastern Finland. The mean recorded dive duration ranged from 2.8 to 6.5 min, with a maximum of 21 min. The mean dive depth ranged from 9.8 to 15.7 m, with maximum of 39.6 m. The maximum dive depth of each seal was limited by water depth in the study area. The dive depths were positively correlated with dive duration and body mass of the seal. Five different dive types were defined, as based on their depth-time characteristics, each falling into one of the three functional categories: travelling, feeding, and resting. Long duration diving bouts occurred mostly at night and were presumed to be resting dives. Saimaa ringed seals exhibited a circadian pattern of haul-out behaviour that shifted seasonally. During molting (May–June) the seals hauled-out both day and night, but later in summer haul-out was more frequent at night.     

Activity cycles in the brown trout (Salmo trutta Lin.)

Summary The annual and diurnal activity cycle for four naturally feeding brown trout separately confined in netting cages on the bed of Windermere is described. All the fish showed a similar annual cycle of maximum activity during May and June, one fish showing a second activity peak during the autumn. The fish also showed a similar diurnal activity rhythm of low activity during the night and increased activity during the day with a pronounced increase at dawn.The possible influence of light and temperature on the fishes activity is briefly discussed.     

Diel variations in Acartia tonsa feeding, respiration and egg production in a Mediterranean coastal lagoon

Short-term changes in abundance, feeding, respiration and spawningby the copepod Acartia tonsa were studied during four 24 h periodsat two stations in a Mediterranean lagoon in May and June of1989 and 1990. Nightly increases of abundance in the upper layer,attributed to nocturnal upward migration, were observed in threeout of the four time series. Nevertheless, occasional dailyincreases were observed too, so that no clear diel patternsin abundance could be defined. Contrarily, diel patterns seemedto appear: (i) for feeding (higher at the beginning of the night),based on gut fluorescence and clearance and ingestion rate measurements;(ii) for respiration (lower at night and based on 8 h incubationperiods); and (iii) for spawning (higher at the end of the night,based on experimental data). The origin of these patterns, aswell as their relationships to environmental data and theirpossible association, are discussed with regard to the availableliterature.     

Circadian and Ultradian Variations in the Plasma Level of Maturational Gonadotropin (GTH II) in the Indian Catfish, Clarias batrachus

Analysis of changes in the plasma levels of GTH II over a 24-h day/night cycle revealed statistically significant circadian or ultradian variation or both in its circulating level during the gonadally active months of the reproductive cycle. The 24-h average and amplitude of circadian or ultradian rhythm in GTH II increased with the advancement of ovarian development and maturation. In April, a single peak in GTH II level was noticed in the night at 20.6 h. In contrast, in May, June and July a biphasic pattern (ultradian rhythm) was noticed with two characteristic peaks, one in the photophase and the other in the scotophase. In addition, in May a statistically significant circadian rhythm in plasma GTH II was validated with a peak located at 20.1 h. These rhythms seem to have physiological significance. The ultradian rhythm with two peaks during the reproductively active phase appears to provide a suitable physiological milieu for the temporally different yet synchronous population of oocytes for the secretion of steroids. Thus, the observed temporal organization in GTH II may have physiological consequences leading to accomplishment of reproductive process at appropriate time of the year.     

Circadian and Ultradian Variations in the Plasma Level of Maturational Gonadotropin (GTH II) in the Indian Catfish,Clarias batrachus

Analysis of changes in the plasma levels of GTH II over a 24-h day/night cycle revealed statistically significant circadian or ultradian variation or both in its circulating level during the gonadally active months of the reproductive cycle. The 24-h average and amplitude of circadian or ultradian rhythm in GTH II increased with the advancement of ovarian development and maturation. In April, a single peak in GTH II level was noticed in the night at 20.6 h. In contrast, in May, June and July a biphasic pattern (ultradian rhythm) was noticed with two characteristic peaks, one in the photophase and the other in the scotophase. In addition, in May a statistically significant circadian rhythm in plasma GTH II was validated with a peak located at 20.1 h. These rhythms seem to have physiological significance. The ultradian rhythm with two peaks during the reproductively active phase appears to provide a suitable physiological milieu for the temporally different yet synchronous population of oocytes for the secretion of steroids. Thus, the observed temporal organization in GTH II may have physiological consequences leading to accomplishment of reproductive process at appropriate time of the year.     

Diel and seasonal habitat and food segregation of three sympatric Coregonus lavaretus forms in a subarctic lake

Habitat use of three sympatric whitefish Coregonus lavaretus forms was determined using hydroacoustics, pelagic trawling and epibenthic gillnetting in the subarctic Lake Muddusjärvi during the day and night in June, August and September. Whitefish constituted 97% of the numerical catches and whitefish with high number of gill rakers (DR) were the most abundant whitefish form. Forms with low numbers of gill rakers used only epibenthic habitats during both the day and night in all study periods: large whitefish with low numbers of gill rakers (LSR) dwelled mainly at depths 0–10 m, whereas small whitefish with low numbers of gill rakers (SSR) used deeper (>10 m) habitats. LSR and SSR whitefish consumed mainly benthic macroinvertebrates during all study occasions. The planktivorous DR whitefish used both epibenthic and pelagic habitats, but vertical habitat selection varied both over time of day and season. In June, when light intensity was continuously high, DR whitefish did not perform diel vertical migrations. In August and September, when dark nights were distinguishable, DR whitefish ascended from the bottom to the pelagic at dusk to feed on zooplankton, and descended at dawn. DR whitefish used pelagic habitats only at the lowest light intensities during the night, which was probably related to the high predation risk from brown trout Salmo trutta .     

Effects of Alternating Night Temperature and Cytokinin Application on the Activity of Enzymes of Sucrose Metabolism in Leaves, Young Shoots and Petals of Roses

Different aspects of growth and development of rose plants grownat constant high or low night temperatures in association withthe activity of enzymes of sucrose metabolism and effects ofcytokinin application were previously described (Khayat andZieslin 1987a). It has also been shown that growth and floweringwere affected when rose plants were grown at night temperaturesof 18?C alternating every 2 h with 12?C. Data on the effectsof alternating night-temperature and application of cytokininon the activity of those enzymes in various tissues of roseplants, in comparison to average activity at constant high andlow temperatures are described in the present report. The resultsshowed that the activities of acid invertase in leaves and youngshoots and of sucrose synthase in petals of rose plants grownat alternating night temperatures were similar to the averageactivity. The alternating temperatures reduced the activityof acid invertase in petals, slightly promoted the activityof sucrose-phosphate synthase in the leaves and enhanced theactivity of sucrose synthase in young shoots. Application ofbenzyl adenine to an axillary bud in plants grown at alternatingtemperature caused a 2-fold increase in the activity of sucrosesynthase and reduced the activity of acid invertase in youngshoots and promoted the activity of sucrose-phosphate synthaseand acidic invertase in leaves as compared with the averageactivity in plants treated with benzyladenine and grown at constanthigh and low temperatures. The relevance of these phenomena to flower formation in rosesis discussed. (Received November 6, 1989; Accepted June 16, 1990)     

北京山区元宝枫夜间液流活动特征及影响因素

树木夜间会维持部分气孔开放,从而能够在一定环境驱动因子的情况下进行夜间蒸腾。夜间液流作为储存水的重要来源,能够补充植物白天的水分亏缺,使其恢复水分储备,对植物生长发育有重要意义。采用TDP热探针法测定了位于八达岭林场的元宝枫树干液流密度,同步监测了主要环境因子,以深入揭示树木夜间蒸腾耗水规律和植被应对环境胁迫的调控机制,为山区植被建设、森林健康经营和挑选节水树种提供理论依据。结果表明:以0:00为界区分前半夜和后半夜,元宝枫夜间液流速率前半夜较后半夜活跃,且前半夜夜间累积液流量占夜间累积液流量的53.85%—64.10%,而后半夜夜间累积液流量占夜间累积液流量的35.9%—46.15%。5月的夜间累积液流量最大,平均夜间液流通量为5月6月8月9月7月。存在水分胁迫的条件下降雨之后夜间液流会增大,而当土壤水分条件较好,土壤水分不再是夜间液流的限制因子时,夜间液流通量并不高。不同树木形态的夜间液流通量有显著差异,在一定范围内,胸径树高冠幅越大的样木,夜间液流通量越大。用于夜间蒸腾的夜间液流通量与饱和水汽压差、温度、空气相对湿度、风速相关,其中夜间蒸腾存在于前半夜,表现为前半夜夜间液流通量与环境因子的相关性相较后半夜相关性较为显著,后半夜则以补水为主,补水量取决于土壤含水量和日蒸腾强度。存在干旱胁迫的条件下,夜间液流既用于夜间蒸腾,又有一部分用来补水;而土壤水分条件好时夜间液流则主要用于补水,此时夜间树干液流与环境因子相关性不高。元宝枫夜间液流通量的日蒸腾贡献率5、6月份大于7、8月份,即干季比湿季贡献率更高。夜间液流通量的日蒸腾贡献率与白天总蒸腾量相关性较高,并与累积太阳辐射成负相关。     

Distribution and onshore migration behaviour of burbot larvae in Lake Constance, Germany

Larval abundance of burbot Lota lota in the pelagic zone of Lake Constance, Germany, peaked during April and remained at a constant but lower level until mid‐June. From the end of May onwards a significant diel vertical migration pattern was observed: while burbot larvae were distributed above as well as below the thermocline in the daytime with the highest percentages of abundance at water depths of 30 and 50 m (below the thermocline) on 5 and 25 June, they were concentrated from 2 to 15 m (above the thermocline) during the night. This migration pattern coincided with a significant decline in the food items preferred by burbot at this life stage, cyclopoid copepods. This phase of diel vertical migration lasted for c . 4 weeks until the burbot larvae suddenly disappeared from the pelagic zone. This indicated a short phase, lasting only a few days, of larval settlement into profundal benthic habitats. This was supported by a significant, abrupt decrease in the absolute growth rates of the larvae at day 56 after hatching. The day–night pattern of vertical migration observed could be assumed to be a transition phase from a pelagic to a benthic lifestyle, as reported for juveniles of several other, marine gadoid species.     

Diel variability in catch rate of juvenile flatfish on two small nursery grounds (Port Erin Bay, Isle of Man and Porto Pirn Bay, Faial, Azores)

Variation in beach seine catches was examined in two juvenile flatfish populations (Port Erin, Isle of Man and Porto Pirn, Azores) to determine the importance of diel cycles while controlling for tidal rhythmicity. At Port Erin sampling was undertaken at each low water on consecutive days over a 2-week period in May/June and September 1991. There was no periodicity in the catches of plaice ( Pleuronectes platessa ) in May/June, but in September catches were higher at night. Other flatfish species ( Limanda limanda, Pleuronectes flesus, Scophthalmus maximus and S. rhombus ) sampled at Port Erin were nocturnal. At Porto Pirn, Azores, fish were sampled over 24 h each month from July 1989 to June 1990 and at each low water over a 2-week period in July 1991. The only flatfish species present was Bothuspodas , which had a diurnal pattern in catches over a 1-year period. Sampling at low water in July gave high catches at both midnight and midday.     

Diurnal shifts in use of summer habitat by age-0 brown trout in a regulated mountain stream

Diurnal shifts in habitat use by age-0 (< 50 mm total length) brown trout (Salmo trutta) were observed from June to July 1989 and 1990 in low-gradient (< 1% channel slope) reaches of Douglas Creek, Medicine Bow National Forest, Wyoming. Fish were visually located during day and night, and water depth, water velocity, distance from the stream edge, substrate, habitat type, and cover were determined at each location. The fish were found predominantly in locations with slow water velocities in stream-margin and backwater-pool habitats. They were observed in slower water, closer to the stream edge at night than during the day.     

Daily feeding rhythm and rations of Pacific salmon of the genus Oncorhynchus in the period of marine prespawning migrations

The daily feeding rhythm and rations of the humpback salmon Oncorhynchus gorbuscha, the sockeyed salmon O. nerka, and the chum salmon O. keta during marine prespawning migrations is investigated with consideration of materials collected at daily stations in waters off eastern Kamchatka in June–July 1999 and 2001 (from catches of drift nets). The bulk of humpback salmon and sockeyed salmon food consists of euphausiids, hyperiids, large copepods, pteropods, and fish juveniles. In the food of chum salmon, pteropods dominated. In a 24-h period, salmon manifest a pronounced evening peak of stomach fullness, while at night feeding discontinues. Samples collected in the morning consisted of fish who had just started feeding after the night pause. In addition to nightly period of rest, all species manifested a daytime decrease in foraging activity, though less pronounced than in the night. The daily rhythm of Pacific salmons’s feeding depends on the vertical migrations of their food items (representatives of sound-scattering layers). During the marine feeding period, the most intensive feeding is recorded in the humpback salmon and chum salmon. The daily ration of the humpback salmon is lower than that of the chum salmon but includes animals of higher food value. Due to a high digestion rate in combination with a large stomach volume, the chum salmon can consume a large quantity of low-calorific food in a short time. The daily ration of the sockeyed salmon is considerably lower than that of other salmon species.     

Autecology of the cryptic mysid crustacean,Heteromysis formosa S.I. Smith 1873, in a temperate estuary

The life history pattern, behavior, and distribution of the mysid crustacean,Heteromysis formosa, was studied in a temperate salt marsh. This mysid occurred in epibenthic sled collections every month, but was most abundant from June through November. Marsh creeks with irregular bottoms supported the largest populations, although some individuals occurred in other estuarine habitats and shallow ocean areas.Heteromysis formosa remains hidden on the bottom during the day and swims over open bottom at night. Many young fishes feed onH. formosa, especially at night. Seasonal changes in mysid abundance were related to the life history pattern. Reproduction was continuous from April through October. Overwintering populations of immature mysids were small. FemaleH. formosa were capable of reproducing more than one time. The number of young per brood ranged from 7 to 32 and was related to total adult body length.     

Diet changes in vertical distributions of larval fishes in unstratified coastal waters off southeastern Australia

Larval fishes were sampled at four depth strata during the dayand night at two locations in unstratified (winter) inner continentalshelf waters off Sydney, Australia, in May and June 1993. Assemblagesat both locations and in both sampling periods were stronglydepth stratified during the day; however, this structure weakenedat night with most taxa being found throughout the entire watercolumn. Two daytime patterns of larval fish vertical distribution(surface and deep dwellers) were evident, and taxon-specificdaytime vertical distributions were strong and not dependenton thermal stratification of the water column. Most larvae caughtwere preflexion and there was little evidence of ontogeneticdifferences in vertical distributions. For most taxa, the patternsof diel change in vertical distribution were similar at bothlocations and in both sampling periods.     

2008年桂北地区稻飞虱特大迁入事件分析

2008年5月下旬—6月中旬,桂北地区出现了褐飞虱Nilaparvata lugens（Stl）和白背飞虱Sogatella furcifera（Horváth）特大迁入峰,单晚单灯虫量超百万。如此大量的迁入虫源究竟来自何方？利用HYSPLIT轨迹分析平台、地理信息系统ArcGIS和气象图形软件GrADS,对稻飞虱的特大迁入峰及其大气背景场的个例分析表明：（1）西南方向的低空急流为广西稻飞虱大规模迁入提供了运载气流,降雨是迫使稻飞虱集中降落的主要原因;（2）5月下旬,虫源地主要分布在越南北部地区（20°～22°N）,6月上旬,虫源地主要分布在越南东北部地区（21°～23°N）,6月中旬桂西北地区大规模迁入的虫源地位于越南东北部、广西西南部,桂东北虫源地分布在广西东南部;（3）虫源地的空间分布和虫源基数的差异直接导致了6月中旬桂东北和桂西北地区降虫量的巨大差异。