摘要:

The pattern and characteristics of diving of two male blue‐eyed shagsPhalacrocorax atricepswere studied, using continuous‐recording time‐depth recorders, for a total of 15 consecutive days during which the depth, duration, bottom time, ascent and descent rates and surface intervals of 674 dives were recorded. Deep dives (>35 m, averages80–90 m, max. 116 m) were twice as common (64% versus 34%) as shallow dives (<21 m and 90%<10 m). Deep dives were long (averages 2.7‐4.1 min, max. 5.2 min) with half the time spent near maximum depth and fast travel speeds (averages 1.0‐2.4 m s−1). Shallow dives were short (average 0.5 min, max. 1.3 min), without bottom time and with slow travel speeds (0.1–0.6 m s−1). The time spent at depth and the diet (mainly benthic fish and octopus) is consistent with benthic foraging; the function of shallow dives is uncertain. Male shags forage mainly in the afternoon in3–5 distinct bouts of diving. Within bouts (and shorter homogeneous sequences of diving) surface intervals are consistently2–3 times the preceding dive duration; in other shags the reverse is the case. Blue‐eyed shag diving depth, duration and pattern is extreme amongst shags; and the relationship between dives and surface intervals suggests that they may regularly exceed t

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03810.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Two independent studies of adult common toad,Bufo bufo, movements between different spawning ponds/populations both within and between years were made in England and Sweden during the spring breeding periods of1987–1990. The results of the two studies were subsequently combined since they were found to be complementary. In addition, in England during 1984 and 1985, large numbers of ‘toadlets’ were marked so that they could be identified if recaptured as breeding adults.The degree of relocation between ponds was negatively correlated to the distance between ponds. The proportion of both males and females that moved between ponds within a particular year was significantly less than the proportion relocating between years. In any year, between 79% and 96% of adults that survived to breed the following year, returned to the original pond. Similarly, of the toadlets marked during1984–85, 81% of the males that subsequently returned as breeding adults were captured in their pond of origin.Isolation, in relation to both population dynamics and population genetics, is defined and its implications for the management of common toad populatins di

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03811.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Shell spectral reflectance, activity and weight loss in the land snailCepaea nemoraliswere examined to test whether solar radiation has different effects on the behavioural and physiological responses of different morphs. A uniform area from the empty shells of different morphs was cut and a spectrophotometer was used to measure the spectral reflectance at wavelengths from 220 nm to 800 nm. Snails were put into cages made of mesh hardware cloth, and their activities were observed from dawn onwards on two hot, dry days. Weight loss of snails under shade and under direct sunlight was also measured.The results show that unbanded morphs reflect more light than five‐banded ones, but the yellow morphs reflect only a little more than pink morphs. Five‐banded morphs became inactive more quickly than unbanded ones from dawn onwards, but the differences in activity patterns were not significant between pink and yellow morphs. There are significant differences in percent weight loss between snails placed under direct sunlight and under shade. The weight loss of different morphs under shade was not statistically different. But when exposed to sunlight, five‐banded morphs lost more weight than pink and yellow unbanded morphs.Because of their lower reflectance of solar radiation, the five‐banded morphs are, in a hot, arid climate, at a selective disadvantage compared to unbanded morphs. However, they can avoid such selective disadvantage by actively seeking a shaded area, as all other morphs do in the field. Such behavioural habitat selection could help the maintenance of genetic polymorphisms in natural popu

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03812.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

This study describes seasonal changes in the diet of a population of wood mice inhabiting a maritime sand dune system. Invertebrates, particularly coleopterans, formed the bulk of the diet throughout the year. This is in sharp contrast to previous studies of mice living in woodlands which eat mainly seeds and other plant matter.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03813.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Digestibility trials using common ringtail possums (Pseudocheirus peregrinus), small folivorous marsupials, were used to determine effects of tannins on a herbivore which has a specialized hind gut and which normally consumes tannin‐rich eucalypt leaves. In one group, untreated leaves were fed to possums, and in a second group polyethylene glycol (PEG) was added to the eucalypt leaves to inactivate tannins. Animals maintained weight, and intakes were not different between the two dietary groups. Digestibility was determined chemically. Digesta were examined histologically. The presence of bacterial rafts in the stomachs of possums fed either diet indicated that PEG did not alter the coprophagic behaviour of possums. Cell wall digestion did not appear to be inhibited by tannins. Tanning of cell contents was predominant, rather than tanning of cell walls. PEG increased faecal excretion of tannins, suggesting that some tannins from normal leaves were digested during gut passage. Dry matter digestibility was higher when animals were fed normal tannin‐rich leaves than when they were fed leaves in which tannins were inactivated. The difference could be explained in part by the high digestibility of tannins. The presence of tannin did not reduce nitrogen digestion. We suggest that dissociation of tannin‐protein complexes may take place in the specialized caecum. We propose that some other folivorous marsupials may have a similar capacity to overcome tannins. This capacity may allow them to consume a tannin‐ri

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03814.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Olfactory bulb size was measured in 146 species of Carnivora in order to examine whether recently observed functional patterns for overall brain size were similar for component parts of the brain. Comparative measures were analysed in relation to various allometric characters (body, brain and skull size), phylogeny, behaviour and ecology. Olfactory bulbs are significantly and positively correlated with all allometric variables, but indices of skull size correlate slightly more closely than other variables. This probably relates to functional aspects of skull size, facial proportions, and anterior elements of the brain. Phylogenetic associations were examined by two comparative methods: the method of independent contrasts and phylogenetic autoregression. Both revealed similar phylogenetic correlation at generic and familial levels. Using calculated values from either method, relative olfactory bulb size only correlates with zonation among seven behavioural and ecological variables; aquatic otters have smaller bulb sizes than carnivores of other zonal types. This agrees with discussion about the diminution of olfactory communication in aquatic environments. Also, olfactory bulb size correlates with home range size, which is consistent with a recent model on the use of olfaction for foraging in designated home ranges. Generally, comparative differences in olfactory bulb size in carnivores do not associate with functional variables found in other comparative studies. Nevertheless, future analyses of specific brain components in mammals may be more useful than overall brain size for testing evolutionary hypotheses of mammalian brain size.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03815.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The haeniatological and rheological characteristics of blood from seven marine mammal species have been examined to determine the relationship between increased haematocrit. which is correlated with the ability to increase aerobic dive limits. and blood viscosity. The species examined reflect adaptations to a variety of marine niches ranging from coastal to pelagic to iceedge environments. and exhibit a wide range of diving behaviours. Average haematocrits ranged from43–45% in bottlenose dolphins. killer whales and California sea lions to more than 60% in the deeper diving species (beluga whales and northern elephant seals). Whole blood viscosity () increased exponentially with haematocrit (= 0.96*e0‐0335*Hct). representin a two‐fold increase from 4.1 cP for killer whale blood to 8.9 cP for northern elephant seal. There was no apparent compensatory mechanism to reduce viscosity at any shear rate. The optimal haematocrit for oxygen transport was calculated to be40–50% for all species tested. The species with lower haematocrits were within optimal values for oxygen transport. while the two species with the highest haematocrits (beluga whales and northern elephant seals) were above predicted optimal oxygen transport values. On the basis of comparisons of the diving behaviour of these seven species, we suggest that marine mammal species with the greatest adaptation for increased oxygen stores via increased haematocrit have the capacity for deep, long‐duration dives, but a limited oxygen transport capacity. We predict that this compromise precludes fast sustainable swimming behaviour in thes

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03816.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The common spiny mouse,Acomys cahirinus(body mass=47 g), is widely distributed in Israeli deserts where it inhabits natural crevices on rocky slopes. This omnivorous rodent consumes a varied diet, and in particular snails. We determined diet selection and energy and water balances of spiny mice when they were offered snails and seeds. The spiny mice maintained steady state body mass. Dry matter consumption of snails was 0.014 g* g−1.‐d−1and of seeds was 0.049g*.g−1d−1for a total of 0.063 g*g−1*d−1. Total water intake was 0.101ml‐g−1.d−1and metabolizable energy intakewas 0.990 kJ. gxs‐1.d−1for a ratio (ml: kJ) of 0.102. This ratio was similar to that reported in a previously published study on free‐living spiny mice. We concluded that snails and seeds allowed spiny mice to fulfil their energy and water requirements with minimal dry matter and fresh matter intakes. Furthermore, spiny mice selected a diet that provided them with a water (ml) to energy (kJ) ratio of approximately 0.1, although it appeared that they are able to sur

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03817.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Lower jaws and measurements were obtained from 473 mountain reedbuckRedunca fulvorufulaculled on two reserves in the north‐eastern karoo of South Africa. All mandibles were allocated to subjective age classes that were based on tooth‐eruption and tooth‐wear. In a sample of 69 jaws. the molar and premolar cementum annuli were counted by examining bisected whole teeth under reflected light. One light line appeared to have been deposited per year, and a usable relationship between tooth‐wear category and cementum line count was obtained. although indistinct and paired lines often confused the picture. Good correlations were also obtained between the number of cementum lines and the crown height of the first molar (r2= 0.68) and the second molar (r2= 0.77). Actual ages of immatures were estimated by comparing peaks in the distribution in the different age classes with the age since expected mean birth date in different culls. The age of transition to adult dentition (pL 30 months) was determined from two females that were earmarked when young and shot two years later. Von Bertalanffy (1957) growth curves were fitted to measurements of body mass, jaw length and horn length in males to aid field identification of immatures. Asymptotic body mass was reached at 30 months in females and 40 months in males, and asymptotic jaw length was reached at 30 months in both sexes. Horns in males only reached full length at about fiv

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03818.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Skull characters of wild boars (Sus scrofaL.) from four regions of Bulgaria were compared using stepwise discriminant, cluster of cases and principal component analyses (PCA). Classification functions were derived for discriminating individuals from different areas. Specimens from the north‐eastern part of the country (Dobrudja and the Balkan Range) were found well separated from those from the south (Rila‐Rhodopes&Strandja Mountains). PCA showed the differences being mostly related to the size rather than to the shape of both the cranium and the mandible. Natural migrations, intergradation areas between different subspecies, as well as restocking and hybridization with semi‐domestic pigs are discussed as possible factors influencing the solution of the problem of the intraspecific systematics of the wild boar in Bul

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1991.tb03819.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY