摘要:

Predators that hunt by sight should be constrained by light levels. This problem should be especially acute in aerial predators such as common poorwills (Phalaenoptilus nuttallii: Caprimulgidae), which capture small insects at night. The purpose of our study was to test the hypothesis that poorwills are constrained to catching larger insect taxa due to limitations of visual orientation under low light. We assessed diet by analysing poorwill faecal samples collected at nest and roost sites in the Cypress Hills of Saskatchewan where prey density is relatively low. Coleopterans (44% and 39% in 1991 and 1992, respectively) and lepidopterans (46% and 55%) dominated the diet, yet these two insect orders were rare in light‐suction trap (22% lepidopterans and 1% coleopterans) and sticky trap samples (11% lepidopterans and 2% coleopterans). Based on measurements of femur length, all consumed coleopterans were>5 mm long, even though 57% of those available were<5 mm. Our results suggest that poorwills are constrained to taking prey above a certain size, but above this threshold, particular prey types and larger sizes may be selected. Selection for coleopterans may reflect the need to acquire polyunsaturated fat to facilitate the use of torpo

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05123.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Chromosomes from all 17 species of native JamaicanEleutherodactylusas well as introducedE. johnstoneiwere subjected to computer‐assisted analyses. Diploid chromosome numbers of 24, 26, 28, 30 and 32 were found and no two species had identical karyotypes. Karyotypic data were superimposed on a phylogeny derived from allozyme and immunological data in order to assess karyotypic changes that occurred in lineages of JamaicanEleutherodactylus.Chromosome number changes have occurred at least nine times on the island and have involved both fission and fusion mutational events. C‐bands and the sites of secondary constrictions varied and provide very little phylogenetic information. In most instances, karyotypically determined interspecific evolutionary relationships corresponded with the molecular data. The combination of karyological analyses and molecular data clarified lineages which involved convergent chromosome numbers or extremely divergent karyotypes. Karyotypic changes in JamaicanEleutherodactylusare best explained by chromosome fission, fusion, translocations and inversions which arose in isolated demes and have been fixed through inbreeding and genetic drift. Rates of karyotypic evolution among JamaicanEleutherodactylusare much faster than previous published rates for frogs. Karyotypic evolution appears to be dictated by behavioural factors and effective population sizes irrespective of taxonomic groupi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05124.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The crural musculature in 19 species of birds was examined. New data on the mechanical properties of avian tendons showed a mean linear elastic modulus of about 1.3 GPa and failure stress of 74MPa. Physiological cross‐sectional areas were calculated for 12 muscles in each species, together with the cross‐sectional areas of their attached tendons. Investigation into potential various sources of error demonstrate this is a robust method for studying muscle‐tendon units. The mode for calculated peak tendon stresses was 17.5 MPa. The results were compared to those obtained from mammal limbs by Ker, Alexander&Bennett (1988). It appears that the muscle‐tendon units in birds are not as strongly optimized for the minimization of mass as those in the limbs of mammals. This may reflect a compromise between optimization for minimum mass and other functional requi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05125.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The purpose of this study was to see if mouflon (Ovis gmelini) females with lambs have feeding habitats similar to other sex‐age classes in spring, in an area without large natural predators. Parous ewes restricted themselves to rocky and poor nutritive habitats but lambed within their winter home range. Once in matriarchal groups, females with lambs ≥ three days old fed more on rocky areas and stayed closer to safe terrain than did other mouflons which more frequently used slope tops, patches containing herbs, and pastures around a little village. Segregation between the two categories of mouflons was reduced when lambs were several weeks old during the peak growing season. Seclusion of parous females may be explained by potential predation by foxes on neonates, an asocial tendency, the need to form mother‐young bonds and the necessity for the young to develop locomotor skills. Rocky areas may also provide favourable microclimatic conditions. Two non‐exclusive hypotheses may account for the tendency of lactating females to remain near ‘escape’ terrain. First, the anti‐predator strategy could be driven in the absence of predators because of phylogenetic inertia. Secondly, the anti‐predator strategy may be learned during the autumn hunting season and exhibited during the lambing season even wi

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05126.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The use of salmonSalmo salarcarrion by ottersLutra lutraand other scavengers along the River Dee in north‐east Scotland was studied by radio‐tagging and individual marking of fish carcasses. More carcasses were available on the Dee than on tributary streams used for spawning, indicating that salmon returned to the river after spawning and died there. The amount of salmon carrion available to terrestrial and avian scavengers along the Dee varied from 6.7 kg. km‐1on an upstream study area to 36 kg. km‐1downstream. Fish carcasses in the Dee were moved by spates up to 20 km but in streams used for spawning less than 1 km. Of 86 carcasses examined in 1990/91, 64 were available to terrestrial and avian scavengers on the bank or awash and of these 45 had been fed upon by otters and 16 by birds. In 1991/92, 23 of 30 carcasses were available to terrestrial and avian scavengers. All had been fed upon, 19 by otters, four by birds. Other carcasses, in shallow water, were not available to terrestrial and avian scavengers. Subsequent scavenging was mainly by otters and continued for up to three weeks after the carcasses were found. HeronArdea cinerea, great black‐backed gullLarus marinusand crowCorvus coronealso scavenged salmon carcasses along the Dee. Great black‐backed gulls were the most frequent scavengers, but heron (dominant to black‐backed gull) was a major scavenger in 1990/91. Crows, subordinate to other scavengers, waited, often in pairs, upon dominant scavengers. There were more scavenging birds downstream and numbers did not change between years. Of 20 salmon carcasses placed in spawning areas eight were probably, two possibly, removed by otters. Otters continued to scavenge carcasses for up to a month. Scavenging by foxesVulpes vulpesand birds followed the removal of fish carcasses from the water by otters. Radio transmitters were removed by otters and left lying alongs

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05127.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Relationships between baculum length, body weight and copulatory behaviour were examined in 66 species of carnivores and pinnipeds (Grand Order Ferae). Elongated bacula occur in most carnivore species of the families Ursidae, Canidae, Procyonidae and Mustelidae as well as in all pinnipeds studied. By contrast, members of the family Felidae have short bacula in relation to their body weights. Elongate bacula are found in carnivores and pinnipeds with a prolonged single intromission (PI) copulatory pattern. This finding agrees with results of a previous study of baculum length and PI copulatory patterns in primates. The enlarged baculum may serve to strengthen the penis and protect the urethra during prolonged intromissions. The distal pole of the baculum may also assist sperm transport since in some species it projects beyond the tip of the penis and probably contacts the female's os cervix during copulation. It is possible that stimulation of the female's genitalia by the baculum might also be important in mammals which are induced ovulators (e.g. Mustelidae). However, it is notable that elongation of the baculum has also occurred in some groups where females ovulate spontaneously (e.g. Canidae, Primates).

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05128.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

The diet of wood mice on set‐aside consisted of 87% plant material, 65% of which was green leaf materials. This diet contains very much less seed or animal material than does that of wood mice studied in other habitats. The poor diet reflected what was available in the are

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05129.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Female brown long‐eared batsPlecotus auritusnurse their own young selectively. Choice experiments suggested that females recognized infants by using both olfactory and acoustic cues. Infant isolation calls (i‐calls) showed individual variation, and vocal signatures allowed the females to recognize and suckle their own pup. As the pups grew, the i‐calls increased in frequency and decreased in duration, and the i‐calls appeared to change into orientation cries. Mothers were able to recognize recent calls of their own babies in preference to older calls. Echolocation sounds were distinguishable statistically between lactating females, and the behaviour of the babies during choice experiments suggested that in this species a mutual acoustic recognition occurs. The growth and development of wing shape inP. auritusare de

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05130.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

In two experiments, in the growing season March–May, freshly harvested double‐low oilseed rape (Brassica napus) plants were fedad libitumto penned roe deer (Capreolus capreolus) and red deer (Cervus elaphus). In Experiment 1, oilseed rape was fed to five roe and 12 red deer as 60% of their daily dry matter (DM) intake for four weeks, after a two‐week dietary change‐over period. The rest of the diet comprised cattle‐rearing pellets (33%) and freshly cut heather (Calluna vulgaris) plants (7%). In Experiment 2, oilseed rape was fed to seven roe and eight red deer as 100% of the diet for up to six weeks, after a two‐week change‐over period.In both experiments, Heinz bodies were found in roe deer blood 2–3 weeks after the start of the change‐over period, with a fall in mean packed cell volume (PCV) and blood glutathione (GSH) concentration. In Experiment 2, after 5–8 days of feeding on 100% oilseed rape, four roe deer showed signs of inappetance and were changed to a diet of 80% oilseed rape. At the same time, the other three roe deer had very low PCV (<60% of normal values) and oilseed rape feeding was discontinued for those animals. The red deer showed no symptoms of haemolytic damage nor any change in blood GSH concentration in either experiment, but showed a gradual fall in PCV in Experiment 2. No other ill‐effects were observed in any of the animals.Intakes of oilseed rape (gDM/kg0–75/day) were lower for the roe deer than the red deer in both experiments. The severity of haemolytic anaemia in the roe deer was related to the proportion of oilseed rape in the diet, rather than the amount ingested. It was concluded that the health of roe deer ingesting oilseed rape may be affected if other

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05131.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

HatchlingXenopus laevisembryos usually swim when the skin is touched with a fine hair. Less common are small, local V‐flexions and more general C‐flexions. Simple flexions or the initial flexion at the start of swimming occur predominantly on the opposite side to the stimulus to direct the animal away from the stimulus. Strokes to the midline lead to random sidedness of responses.The reliability of the sidedness of flexions and the first flexions of swimming decreases the more rostrally the stimuli are given. The range of directions of swimming paths are larger with more rostral stimuli so responses to head stimuli are unpredictable in direction.In animals immobilized in α‐bungarotoxin, strokes to the skin produce electrically recorded motor output which corresponds to: V‐flexions, C‐flexions and swimming. Fictive activity generally starts on the side opposite to the stimulus. The fictive responses suggest that the three basic behaviour patterns observed can be generated entirely within the central nervous system without any sensory feedback.We discuss possible mechanisms for the generation of ‘protean’ responses to head stimulation which are unpredictabl

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1995.tb05132.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY