摘要:

Hoarding behavious, seed species hoarded and hoarding intensity by red squirrels (Sclurus vulgarisL.) are described for two population; one in a coniferous woodland with few deciduous trees, the other in a mixed deciduous woodland with some conifers. Seasonal variation in the recovery of hoards and the importance of hoarded food with regard to a squirrel's annual energy demands are discussed. The importance of having hoards is compared among tree squirrel species.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05389.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A unique form of behaviour,‘ploughing behaviour’, was studied in experiments carried out on 13 babirusa, three adult males, two sub‐adult males, five adult females and three sub‐adult females. Ploughing behaviour was observed when individual animals were introduced singly into empty sand‐filled enclosures at Antwerp Zoo. The animal put its snout into the sand to such a depth that the sand was just in front of its eyes, whereupon it knelt and slid forward on to its chest. The head and chest of the animal were thereby pushed forward through the sand and canted left and right alternately. Ploughing behaviour was almost exclusively performed by adult males, the periods of longest duration being seen either in the enclosure of another male or in a freshly cleaned enclosure. The copious amounts of saliva which were produced as foam at the sides of the mouth prior to ploughing had disappeared by the end of this activity. This supports the idea that ploughing by the babirusa has a scent‐marking function. The adult female did not show ploughin

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05390.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Two forms of a large and flightless rail (takahe) belonging to the genusPorphyrioand endemic to New Zealand have been described, although their taxonomy has been repeatedly questioned. Analyses of osteometric data from modern and Quaternary fossil material show such a degree of allometric distinctiveness that it is considered that the two forms are, indeed, different species as originally described,Porphyrio mantelli(Owen),Porphyrio hochstetteri(Meyer). It is suggested that this degree and type of difference could have resulted from the two species arising independently from similar volant ancestors.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05391.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Water potential and temperature were monitored in 20 natural nests of tuatara,Sphenodon punctatus, through 12 months of incubation on Stephens Island, New Zealand. Tuatara nest in rookeries in open pasture, in sites that often are more than 100m from residential burrows located beneath the closed canopy of native bush. Nest tunnels are approximately 197 mm long, 73mm wide, and 45mm high, and have a slightly expanded chamber at the end. Eggs are generally deposited in 1‐3 layers in the terminal chamber. The top eggs are 30‐155mm below the soil surface, and an air space of as much as 20 mm may exist between the uppermost egg and the top of the chamber. Each nest receives an average of 8.6 eggs that imbibe water and swell during incubation. Only 48% of eggs have hatched or are still alive 12 months after oviposition. Survival by embryos is higher in moist nests than in dry ones. Variation in temperature in nests has only a small influence on survival, and this influence may be mediated indirectly by effects of temperature on the water exchanges experienced by incubating eggs. Water potentials in the soil of closed canopy forest on Stephens Island are high enough to support embryogenesis, but temperatures are too low. Thus, females leave the forest to nest in areas where soil temperatures are suitable for incubat

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05392.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The speciesOtotyphlonemertes correaesp. nov.andO. duplexBürger, 1895 (Ototyphlonemertidae) are described. The new species possesses a smooth stylet, oligogranular statolith and nephridia. Phylogenetic relationships are reconstructed for 21Ototyphlonemertesspecies, based on an analysis of 18 morphological characters, totalling 43 character states. The most informative characters are stylet structure, basis shape, statolith shape and nephridia. Based on the phylogeny, the subgenusOtohelicophora(Greek,helicophorameaning the spiral carriers) is separated, which is defined with reference to the synapomorphy ‘spiral style

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05393.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Canonical discriminant analyses were used to assess whether four populations of Cape sparrows varied in body size and shape according to predictions from Bergmann's Rule. In accordance with Bergmann's Rule, birds from two hot, arid Namib desert sites (Namib 1 and Namib 2) were smaller than birds from two cool, mesic Transvaal sites. If heat dissipation through extremities (tarsi) is important to reduce water lost from evaporative cooling, birds under hot conditions in dry environments (Namib 2) should have longer tarsi than those in more humid hot environments (Namib 1). Contrary to this, males at Namib 2 had relatively longer wings hut shorter tarsi than at Namib 1, and female relative tarsus length did not vary between desert sites

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05394.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Phally, a genital polymorphism found in some species of self‐compatible pulmonates (Mollusca: Gastropoda), presents an opportunity to examine factors maintaining outcrossing within an animal species in the presence of recombination. Euphallics, aphallics, and hemiphallics can selffertilize but only euphallics develop a functional penis and prostate allowing them to donate sperm. Taxa containing aphallics and/or hemiphallics are rare within pulmonates (occurring in about 0.3% of species and genera) and are found near the tips of the phylogenetic tree at the species and genus level, suggesting that the loss of male outcrossing ability is unstable and has limited evolutionary potential. Phylogenetic analysis based on parsimony reveals that male outcrossing ability has been lost a minimum of 13 times. We find no unambiguous evidence of reversions from aphally and/or hemiphally back to pure euphally. In plants, self‐fertilization is often associated with habitat and geographic range, and these variables, together with body size, have been hypothesized as factors facilitating the evolution of aphally. When we control for phylogeny using comparisons of sister taxa, loss of male outcrossing ability is associated with geographic range but not body size or habitat. Furthermore, polyploidy is not associated with the loss of male outcrossing ability, contrary to predictions that low levels of inbreeding depression in polyploids will facilitate the evolution of aphally and/or hemiph

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05395.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Althoug frequency of occurrence (either as percentage or relative frequency) is the most common method of expressing the content of otterLutra lutrafaeces (spraints), the accuracy of the method, and the effects of varying sampling procedures (e.g. inter‐collection interval) and sample sizes, have not been quantified. The validity of the technique was assessed in the present study by feeding trials involving captive, tame otters and computer simulation of various spraint sub‐sampling regimes. Four animals were fed known quantities (numbers and biomass) of a total of nine fish species, two bird species and one mammal over a 28‐day period. Most prey remains were passed in spraints within 24 h, although perchPerca fluviatilisscales appeared up to 10d after consumption. Remains from single meals of perch were recorded in 60 subsequent spraints from two otters, and remains of individual eelsAnguillu anguillawere recorded in up to 11 spraints. Some single spraints contained the remains of up to seven individual salmonids,Salmo spp.MinnowsPhoxinus phoxinusplaced within the body cavities of larger rainbow troutOnrorhynchus mykisswere easily identified in spraints, as were the remains ofDytiscusspp. beetles which were not included in trial meals. The latter confirms that otters actively consumed large free‐swimming insects. Spraint analysis accurately determined the rank order of prey groups for individual otters and for all four combined. However, few of the true proportions consumed fell within the 95% confidence limits calculated from spraints. Over the month‐long trial, the overall picture of otter diet was altered little by increased inter‐sampling period for spraints. But as samples were reduced, coefficients of variation for the mean estimates of each prey group increased and were often too large for estimates to be meaningful. It is not possible to quantify otter diet accurately by frequency of occurrence methods, and the results of previous studies attempting to quantify the amount of a specific prey item consumed by otters using this method must be treated with caution. Diet could be estimated more accurately from spraint analysis by concentrating on the main prey species and using keybones, which are resistant to digestion, to determine relative size‐frequency

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05396.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

New methods of estimating the size of salmonidsSalmospp. and eelsAnguilla anguillaconsumed by ottersLutra lutraare presented, based on feeding trials involving captive, tame otters. These methods involve modelling the size‐related differential recovery of key fish bones recovered in faeces (spraints) and avoid two sources of errors that may have occurred using previous techniques which relied solely on a series of correlations between fish length and the length of individual vertebrae. Sources of errors avoided are: (a) that vertebrae recovered in spraints could not always be assigned to the correct correlation equation for mean, maximum, or minimumsized bones; and (b) that the number of fish represented in a spraint was assumed to be one, in the case of similarly‐sized vertebrae, and two in the case of bones varying considerably in size. We tested the use of salmonid atlas vertebrae to determine the largest minimal numbers estimate, the length frequency distribution of salmonids consumed, and to estimate the proportions of trout and salmon in the diet. Eels do not contain an atlas which is resistant to digestion and so equivalent estimates of the minimum numbers of fish represented in spraints are not possible. A model was therefore developed to estimate the distribution of lengths of fish consumed from the lengths of thoracic vertebrae recovered in the spraints using a series of equations. For each type of prey (salmonids or eels), the proportions of identifiable bones recorded in spraints were related to the original size of ingested fish. Such models greatly enhance the value of otter spraint analyses, particularly for size‐selection st

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05397.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The brain of Antarctic fish of the perciform suborder Notothenioidea was analysed with lightand electronmicroscopical methods. The overall organization and ultrastructure of the optic tectum is very similar to that of fish from temperate climates. However, unusual structures were observed in neurons and glial cells, sometimes in high frequencies. The structures are ovoid or elongated, about 200‐600 nm in diameter and surrounded by two layers of membranes in a uniform distance of about 30 nm. The enclosed inter‐membrane space is similar to extracellular space, both in size and in cytochemical calcium precipitation, while the interior of the structures resembles cytoplasm. These structures are sometimes connected to neuronal processes, so that they seem to originate by a sort of budding process, but most of them are isolated as can be concluded from thick sections of up to 800 nm thickness, analysed with energy‐filtering transmission electron microscopy (EFTEM). These unusual objects are present in high abundance in members of the white‐blooded Antarctic fish family Channichthyidae. These so‐called icefish lack haemoglobin and exhibit the highest degree of cold adaptation. The red‐blooded notothenoid fish had smaller amounts of these structures and they were observed even in fish from temperate climates (trout, carp, cichlid fish). In fish from temperate climates the unusual substructures were more abundant during adaptation to cold water temperatures (winter) than to warm conditions (summer). Therefore, the findings may indicate a general phenomenon of cold adaptation with unusual interactions of neurons and glial cells, but the precise function is not yet

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1996.tb05398.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY