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Using a preference test and operant conditioning in a Y-maze, this experiment examined the ability of heifers to discriminate between their own familiar herdmates and member(s) of an unfamiliar group. Sixteen Danish Friesian heifers, eight older animals (360.6 ± 24.2 days of age) and eight younger ones (190.1 ± 14.1 days of age) were used. Each age group was further divided into two experimental groups. Members of each of these groups were housed together in small pens before the experiments began. In experiment 1, each of the 16 animals was allowed to approach either a familiar or an unfamiliar individual in the Y-maze. The test was repeated 12 times, with a different unfamiliar subject for each test. In experiment 2, eight heifers were individually tested in a conditioning experiment to examine whether they could learn to discriminate between a group of their three herdmates and a group of three unfamiliar heifers. Test animals were rewarded when they chose their own group. In experiment 1, heifers did not show a preference between familiar and unfamiliar individuals. Interestingly the younger stimulus heifers but not the test animals showed an ability to discriminate between unfamiliar animals by vocalizing. In experiment 2, four of the eight test animals achieved the criterion for successful discrimination between the familiar and unfamiliar group ( P < 0.003: binomial law). There was no age group difference in the ability to discriminate between familiar and unfamiliar animals. In conclusion, heifers did not show a preference toward familiar or unfamiliar individuals; but after conditioning, some heifers could learn to discriminate between familiar and unfamiliar groups. 相似文献
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CEDAR M. CHITTENDEN BJØRN ÅDLANDSVIK OLE‐PETTER PEDERSEN DAVID RIGHTON AUDUN H. RIKARDSEN 《Fisheries Oceanography》2013,22(1):1-13
The use of pop‐up archival satellite tags (PSATs) to geolocate marine fishes in polar regions is challenging due to the brevity of periods during which there is a defined sunrise and sunset. Models using other environmental parameters are thus required to supplement geolocation data in the estimation of marine migratory routes. The objective of this work was to create a simple method that would estimate the migratory pathways of Atlantic salmon (Salmo salar) in polar regions using temperature and depth recordings. Validated geolocations from PSATs were used to test and constrict the model. The model’s predicted migratory routes were within 100 km of the light‐based geolocations calculated by the tags. By constraining the trajectories through the geolocations, bias was reduced. Sensitivity analyses demonstrated that slight alterations of the location and timing of the start and end points did not affect the mean migratory route estimates. This method is a management tool that can determine the primary habitat areas for any surface‐ or bottom‐dwelling marine species – especially in polar regions, where other methods may be impossible. 相似文献
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Dispersal of conidia of Ascochyta fabae f. sp. lentis from infected lentil plants by simulated wind and rain 总被引：1，自引：0，他引：1
Splash was shown to be an effective mechanism for short-range dispersal of conidia of Ascochyta fabae f. sp. lentis , the cause of ascochyta blight of lentil. The dispersal gradients were well described by the power law model in its linear form, In y = In a-b In x. In still air the slope of the linearized dispersal gradient, b , ranged from 2.83 to 4.07 and was steeper for 4.9 mm than for 3.9 mm incident drops. Nevertheless, for all drop sizes tested, fewer than 50% of the conidia were splashed more than 15 cm from the source. The pattern of conidium dispersal was similar for both drop sizes when horizontal windspeeds were 2.5 or 5 m/s. Wind significantly decreased the value of b (range 2.35-2.43 at 2.5 m/s, 1.71–1.91 at 5 m/s) and increased by about 2 m the maximum distance that conidia in ballistic droplets were deposited. In addition, the experiments suggested two other potentially important mechanisms for dispersal of the pathogen over longer distances, namely conidia in small air-borne droplets and windblown leaflets. 相似文献
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Six rats, working in a 2 degrees C ambient temperature, were trained to depress a lever to receive a brief period of heat. Four rats were then moved into the 2 degrees C environment to live, while the others continued to live at room temperature. Living at a temperature of 2 degrees C increased the number of heat presentations the animals delivered to themselves. 相似文献
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Influence of long photoperiods on the growth of timothy (Phleum pratense L.) varieties from different latitudes in northern Europe 总被引：1，自引：0，他引：1
Plants of three varieties of Phleum pratense L. from different latitudes (cv. Engmo, 69°N; cv. S48, 52°N; cv. Motim, 52°N) were grown from the five-leaf stage at 12°C under continuous illumination or 8-h days at essentially identical daily inputs of radiant energy. The responses to daylength extension (increase in plant dry weight, plant height and leaf dimensions and reduction in the number of tillers per plant and in tissue dry matter content) were common to all three varieties and although the enhancement in plant dry weight and in leaf size was greater in the Engmo plants, this was principally the result of poorer growth and smaller leaf size in 8-h days. Marked differences between Engmo and the other varieties in the partitioning of dry matter within the plant were the consequence of differences in the rate of reproductive development. For example, compared with S48 and Motim, first spike emergence and 50% anthesis in the Engmo plants were delayed by 22 and 14 days, respectively, and 40% of the Engmo plants did not become reproductive even after 110 days of long-day treatment. Furthermore, by the time that 50% anthesis of the mainstem spike had been reached by the long-day plants of each variety, significant differences in tiller numbers and tiller fertility had developed between the varieties from high and lower latitudes. These findings and the results of previous studies of Poa pratensis, Dactylis glomerata and Bromus inermis are discussed in relation to the adaptation of high-latitude grasses to the Scandinavian environment. 相似文献
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MAGNUS AUNE WIEDMANN OLE‐PETTER PEDERSEN EINAR MAGNUS NILSSEN 《Fisheries Oceanography》2012,21(6):379-392
Oceanographic and predation processes are important modulators of fish larvae survival and mortality. This study addresses the hypothesis that immature Norwegian spring‐spawning herring (Clupea harengus), when abundant in the Barents Sea, determine the capelin reproduction success through consumption of Barents Sea capelin (Mallotus villosus) larvae. Combining a hydrodynamic model and particle‐tracking individual‐based model, a realistic spatio‐temporal overlap between capelin larvae and predatory immature herring was modelled for the summer seasons of 2001–2003. Capelin larvae originating from western spawning grounds became widely dispersed during the summer season, whereas those originating from eastern spawning grounds experienced a rapid drift into the southeastern Barents Sea. Herring caused a 3% mortality of the capelin larvae population in 2001 and a 16% mortality in 2003, but the effect of predation from herring on capelin larvae was negligible in 2002. Despite a strong capelin larvae cohort and a virtual absence of predatory herring, the recruitment from the capelin 2002 year class was relatively poor from a long‐term perspective. We show that the choice of capelin spawning grounds has a major impact on the subsequent capelin larvae drift patterns, constituting an important modulator of the capelin larvae survival. Variation in drift patterns during the summer season is likely to expose the capelin larvae to a wide range of hazards, including predation from young cod, sandeel and other predators. Such alternative predators might thus have contributed to the poor capelin recruitment during 2001–2003, leading to the collapse of the capelin stock in the subsequent years. 相似文献
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S. PEDERSEN G. RASMUSSEN & E. E. NIELSEN L. KARLSSON & P. NYBERG 《Fisheries Management and Ecology》2007,14(1):21-32
Abstract Atlantic salmon, Salmo salar L., reared from two Baltic strains were released around the islands Bornholm and Møn in the Baltic Sea between 1995 and 1999. A total 600 000 reared salmon were released from net pens using the delayed release technique, keeping the salmon in net pens for approximately 3 months after smolting, and 208 000 were released directly from the hatchery. Of these, 15 958 were tagged with Carlin tags. Additionally, 65 300 coded wire tagged salmon were released as delayed release salmon close to Bornholm in 2000. Recaptures from the five years of Carlin tagged releases varied between 2.8% and 21.2% (average 13.1%). Most recaptures were from within the Baltic Sea (average 98%), but some were recaptured outside the Baltic Sea, either in the sea (1%) or in fresh water (1%). Recaptures outside the Baltic Sea and in fresh water were higher for releases at Møn in the western part of the Baltic, than releases at Bornholm. Straying rates from the releases into six rivers on the Swedish west coast were estimated using information from capture in traps and sport and broodstock fisheries. The proportion of straying salmon in rivers on the Swedish west coast was about 3.8% of the salmon run, but with large variations between rivers. Releases were discontinued because of possible deleterious effect on the local wild salmon populations. 相似文献
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Thomas J. DELIBERTO Seth R. SWAFFORD Dale L. NOLTE Kerri PEDERSEN Mark W. LUTMAN Brandon B. SCHMIT John A. BAROCH Dennis J. KOHLER Alan FRANKLIN 《Integrative zoology》2009,4(4):426-439
As part of the USA's National Strategy for Pandemic Influenza, an Interagency Strategic Plan for the Early Detection of Highly Pathogenic H5N1 Avian Influenza in Wild Migratory Birds was developed and implemented. From 1 April 2006 through 31 March 2009, 261 946 samples from wild birds and 101 457 wild bird fecal samples were collected in the USA; no highly pathogenic avian influenza was detected. The United States Department of Agriculture, and state and tribal cooperators accounted for 213 115 (81%) of the wild bird samples collected; 31, 27, 21 and 21% of the samples were collected from the Atlantic, Pacific, Central and Mississippi flyways, respectively. More than 250 species of wild birds in all 50 states were sampled. The majority of wild birds (86%) were dabbling ducks, geese, swans and shorebirds. The apparent prevalence of low pathogenic avian influenza viruses during biological years 2007 and 2008 was 9.7 and 11.0%, respectively. The apparent prevalence of H5 and H7 subtypes across all species sampled were 0.5 and 0.06%, respectively. The pooled fecal samples (n= 101 539) positive for low pathogenic avian influenza were 4.0, 6.7 and 4.7% for biological years 2006, 2007 and 2008, respectively. The highly pathogenic early detection system for wild birds developed and implemented in the USA represents the largest coordinated wildlife disease surveillance system ever conducted. This effort provided evidence that wild birds in the USA were free of highly pathogenic avian influenza virus (given the expected minimum prevalence of 0.001%) at the 99.9% confidence level during the surveillance period. 相似文献