摘要:

The possibility of different refuge strategies resulting in habitat segregation in two sympatric rodents, the bush Karoo rat,O. unisulcatusand the whistling rat,P. brantsiiwas investigated. The rodents' habitats were characterized by using the multivariate analysis procedures: ordination diagrams and hierarchical classification. The most important environmental variables were identified.Otomys unisulcatuswas restricted to areas with high percentage plant cover (60.6%) and dense foliage compared toP. brantsiihabitat (plant cover=34.8%). The high percentage plant cover is necessary for nest construction.Parotomys brantsiihabitat was characterized by deep Soil (76.9+15cm) with larger soil particles (0.31+0.2mm) compared to 47.5+30.3 cm soil depth and 0.15+0.1 mm soil particles inO. unisulcatushabitat. A suitable substratum therefore determines distribution ofP. brantsii.The different refuge strategies result in habitat segregation and may be an important means of partitioning resources between these two sympatric rodents which have comparable body sizes, adtivitym dietary and thermoregulatory patterns.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04784.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Six species ofBrookesiadwarf chameleons were recorded during two rainforest expeditions in Madagascar. One of these is described as a new speciesBrookesia valerieaebased on the arrangement of the nine pairs of dorso‐lateral spines, the lack of a pelvic shield, and dorsal chevron markings. Observations were made on the defence and roosting behaviours shown by these six species. Aspects concerning the evolution and conservation in Madagascar are discussed for this poorly studied group of endemic Malagasy reptile

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04785.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

JuvenileOctopus vulgarisforaged by chemotactile exploration, mainly in crevices and under rocks. They caught small crustaceans and molluscs, includingLimabivalves, and preferred crabs andLimain a simple laboratory choice test. Octopuses consumed 30% of their prey away from home, and small remains of prey deposited in the midden were selectively removed by waves and currents resulting in an underestimate of the octopus' intake and diet.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04786.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The dispersion of ottersLutra lutrawas studied along the coasts of an area of Shetland. The population was relatively stable, with about one adult otter per kilometre of coast. They fished diurnally in a strip of water usually within 100 m of the shore. Females lived in exclusive group ranges, occupied by up to four females, with well‐defined boundaries which were respected by successive occupants. For two groups, where relatively complete information was available, range size was 4.7 and 6.4 km, occupied by two and four females, respectively; a third range was about 14 km, with possibly 4–5 females. Within the group ranges individual females moved on their own or with their cubs. Each had a core area, where they were observed>50% of the time; these core areas were separate from each other, although each individual used the entire group range. Several or all females in each range bred in any one summer. Male ranges were larger than those of females, and overlapped with two or more female group ranges; there were several resident males along each section of coast, but the information on males was incomplete. The habitats of the sexes were different; males spent more time on exposed coasts than did females. There were frequent visits to all coasts from non‐resident otters of both sexes.Behavioural interactions related to territoriality are described; otters showed little overt aggression, except between adult males, but there was some individual avoidance. It is argued that the survival value of this spatial organization can be understood in terms of resource dispersion, but several types of resources have to be considered (including prey and fresh water), and detailed predictions of spatial organization from resource dispersion are unwarr

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04787.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Tardigrades were sampled from diverse biotypes and classified according to four xeric variables to assess susceptibility to desiccation: exposure to insolation, elevation, and standardized desiccation rate and hydration capacity of the habitat plant. Fifteen tardigrade species were recorded includingHypsibius cataphractusMaucci, a new addition to the British fauna.Xeric associations with seven tardigrade species were analysed by multiple regression, using incidence and population density as independent abundance estimates. Species show considerable variation in ecotype. The hygrophilicMacrobiotus hufelandiandHypsibius dujar diniare excluded from rapidly desiccating habitats. Xerophiles,Milnesium tardigradumandH. oberhaeuseri, do not favour high insolation or high desiccation rate but apparently shun poorly drained sites and/ or prolonged hydration. Significant interspecific associations are identified betweenMilnesium tardigradumand twoHypsibiusspecies which it may exploit for food. Negative associations between three other species—M. hufelandi, M. richtersiandH. prosostomus—suggest competitive exclusion.The interstitial meiofauna of a dehydrating moss cushion migrates vertically to the proximal C‐zone, although this behaviour is not observed inEchiniscus testudo;implications of this for the species' ecotype are disc

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04788.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Maculinea rebelicaterpillars spend their final instar as specific parasites of colonies of the antMyrmica schencki. This paper describes 14 experiments in which 604 caterpillars were reared with six species ofMyrmica. About 40% of caterpillars died during an initial period of integration: survival was significantly greater among the larger caterpillars, inM. schenckinests, and in nests that had ant‐brood present. The growth of the survivors was extremely variable. After three weeks they had gained 2–18 times their initial body weight and appeared to belong to two distinct types: fast and slow developers. Only 11% of caterpillars died during the next 37 days of growth, before a fall in temperature to below c. 14 d̀C caused them to overwinter. By then, the caterpillars weighed from 5–90 mg (mean 22 mg).Caterpillars of all weights lost 33% of their mass during winter, and 8% died, before rising temperatures caused growth to resume in spring. Ofthe 363 that survived winter, 44% died during a period of spring growth and 12% pupated after about seven weeks. The latter came mainly from the largest caterpillars before winter and pupal size (mean weight 81 mg) was also related to prewinter caterpillar size. The remaining 44% of post‐winter caterpillars continued to grow slowly and then entered another quiescent phase and were still alive after one year in the nest. A small number of these pupated in the second year, an average of 404 days after adoption.It is calculated that an average‐sizedMyrmica schenckicolony of 350 workers can produce 4–5 adult butterflies; this laboratory result agrees well with field observations. The results are discussed in the light of a previous behav

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04789.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The weights of testes, prostate gland and baculum of ringed seal males were related to age, season and differences in body size. There was a significant seasonal variation in testes and prostate gland size of sexually mature males, with a maximum occurring in early April. There were no seasonal changes in prostate weight of immature males, but some of the older immatures had elevated testes weights in April. Testes weight was significantly correlated with lean body mass. The increase in testes size with increasing body weight was greater for seals six years of age or older than for younger males. We suggest that some testicular growth and a seasonal cycle in testes growth occur before the testes become functional endocrinologically. We also believe that the primary event leading to puberty in ringed seals is an age‐dependent shift in metabolic processes, directing a larger percentage of available energy towards the reproductive organ

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04790.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Hepatozooninfections ofSciurus carolinensiswere investigated by a 30‐month capture/recapture trapping programme. Details of trapping methods, squirrel husbandry and blood sampling techniques are discussed.Hepatozoongametocytes infected blood monocytes and could be detected in blood smears or by concentration of leucocytes. From blood smears, 71% (154/218) of the squirrels were infected. Prevalence appeared to be influenced by host hormonal and breeding patterns. Significantly more adult males than adult females were infected (P<0.025). Infections were significantly more prevalent in adults overall and in adult males than in juvenile males (P0.05). Prevalence rates were generally higher: (i) in summer and winter, when animals mate, compared to spring and autumn; and (ii) in 1984 than in 1983, possibly relating to differences of squirrel breeding success and juvenile recruitment in the two years. Parasitaemias were overdispersed in the sampled host population and significantly lower in females (38%) than in males (48%) (P<0.05), although there was no significant difference between the age classes. Animals, either recaptured or laboratory‐maintained, showed chronic fluctuating parasitaemias with no obvious pattern. Squirrels with overt parasitaemias showed trophozoites and schizogonic stages ofHepatozoonin the lung and rarely in liver and spleen. Three out of 16 animals with no obvious parasitaemias had lung tissue stages of the parasite. Results suggest thatHepatozoonis more prevalent in grey squirrel populations than blood smears sugg

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04791.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The lungs of five female domestic Muscovy ducks, mean body weight 1.627 kg, total lung volume 48.07 cm3, were analysed by standard morphometric methods. Principal results obtained are: lung volume per unit body weight, 30.17 cm3/g; volume densities of exchange tissue relative to lung volume, 49.24%, blood capillaries relative to exchange tissue, 29.63%, tissue of the blood gas (tissue) barrier relative to exchange tissue, 5.88%; surface area of the blood‐gas (tissue) barrier per unit body weight, 30.04 cm2/g; ratios of the surface area of the blood‐gas (tissue) barrier per unit volume of the lung and per unit volume of exchange area, 979 cm2/cm3and 200.06 mm2/mm3, respectively; harmonic and arithmetic mean thicknesses of the tissue barrier, 0.199 μm and 0.303 μm, respectively. The anatomical diffusing capacity of the tissue barrier for oxygen (DtO2) and the total pulmonary diffusing capacity (DLO2), 49.58 ml O2/min/mmHg/kg and 4.55 ml O2/min/mm Hg/kg, respectively. The lungs of the domestic Muscovy duck appear to be about as well adapted anatomically for gas exchange as the lungs of wild anatid species, and there is no clear evidence that domestication has been associated with any deterioration in the anatomical capacity for oxygen uptake. The weight‐specific anatomical diffusing capacity of the lung for oxygen (DLO2/W) was about 3.6 times greater than the weight‐specific physiological value, a factor which falls within the expec

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04792.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Cheiroseiulus reniformisn.gen., n. sp., a platyseiine mite from water pools on epiphytes in Jamaica, is described. The species is characterized by having a markedly hypotrichous opisthonotal chaetotaxy. A key is given to the genera of the Platyseiinae.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb04793.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY