摘要:

The home ranges, space‐use patterns, seasonal distribution, long‐distance movements, water‐related movements and movement patterns of elephants (Loxodonta africana) residing in the northern Namib Desert region of the Kaokoveld, South West Africa/Namibia, are discussed. All movements of the desert‐dwelling elephants, including occasional wanderings up to 195 km, were confined to the northern Namib Desert and no evidence could be found of any movements including migrations to and from the Etosha National Park. Home range size varied from 1763 to 2944 km2and the main feature of the spatial distribution of these elephants is the marked fidelity to individual home ranges. Seasonal distribution and space‐use patterns within individual home ranges coincide with seasonal climatic changes and the corresponding changes in food and water availability. The elephant's normal movements and migrations were confined to individual home ranges and no mass population migrations took place. Their mobility and their ability to go up to four days without drinking water enabled them to utilize food sources up to 70 km away from waterholes and, together with their intimate knowledge about resource distribution within their home ranges, are regarded as key factors in their survival in the desert. The elephants' spatial distribution and movement patterns indicate a natural population segregation from other elephant populations in the Kaokoveld, clearly demarcating the desert‐dwelling elephants as a distinct population with their own movement patterns and geogr

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02561.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The histology and the protein, carbohydrate, lipid and enzyme histochemistry of the dermis of the chequered water snake,Natrix piscator, have been examined throughout the sloughing cycle.The structural organization and staining properties of the dermis do not show any changes in different stages of the cycle.The dermis is divided into the stratum laxum and the stratum compactum. Acid mucopolysaccharide deposits in the stratum laxum, which possibly bind water, may be involved in prevention of desiccation.The numerous elastin fibres in the hinge regions are related to the greater elasticity of the skin in these sites.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02562.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The activities and food selection of four hand‐reared kudus were recorded in a large fenced enclosure containing natural savanna vegetation in the Nylsvley Nature Reserve, South Africa. Leaves of selected species were analysed chemically for crude protein, fibre constituents, phosphorus, condensed tannin and total polyphenols. Available protein and metabolizable energy were estimated allowing for potential antinutritional effects of tannins.Leaves of palatable deciduous woody plants and herbaceous forbs formed the main dietary constituents during the late wet season. Foliage from palatable evergreens and robust forbs were added to the diet during the dry season. Towards the end of the dry season unpalatable species of evergreens were eaten. At the start of the growing season new leaves of otherwise unpalatable woody species formed the staple food source, together with fruits ofStrychnosspp. Correspondingly, protein and digestible dry matter concentrations in the diet declined to reach a low at the end of the dry season.Total daily food intake increased to compensate for reduced dietary quality during the dry season, until little edible foliage remained. While the estimated daily intake of protein remained well above maintenance requirements, the estimated metabolizable energy intake fell below requirements during the late dry season. Phosphorus intake may have been submaintenance in the dry season. Nutritional balance was dependent on the availability of particular vegetation components to serve as nutritional stepping stones during crucial times of the year. These included forbs during the late wet season, palatable evergreens in the dry season, andStrychnosfruits plus early‐flushing woody plants during the dry season‐wet season trans

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02563.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Cryptomys h. hottentotusoccurs in mesic and semi‐arid regions of South Africa. It lives in colonies ofup to 14 individuals, in which reproduction is limited to one ofthe largest males and the largest female in the colony.Reproduction and details of colony size and the number of breeding animals in a colony are described for one complete and two incomplete field‐captured colonies. One incomplete colony was kept in captivity for more than 3 years, whereas the complete colony was autopsied.The social hierarchy of the common mole‐rat is almost linear and has a value of 0.7 1 calculated from Landau's linearity index. Subordinate mole‐rats weighed less than dominant mole‐rats. The reproductive mole‐rats are the dominant animals within the colony. The non‐reproductive females rank lowest in the hierarchy.Mating was not confined to a particular season, but occurred more frequently during the summer months. The alpha male initiated pre‐copulatory behaviour. The gestation length is 55 to 66 days (n = 2). Two litters each of three pups were born to the colony during captivity. The pups were relatively altricial. They wandered out of the nest 5 days after birth, began to eat solids when 10 days old, and were fully weaned at 4 weeks. When 2 weeks old the pups began to spar with each other and with some of the adult colony members, but levels of aggression were never high. The pups did not disperse but were incorporated into the colony, this suggesting thatC. h. hottentotuscolonies are largely composed of rela

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02564.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Conventional aerodynamic arguments suggest that possession of high aspect ratio wings will always improve the flight performance of glides. Drag and power will be minimized at intermediate flight speeds. It is shown, however, that as the aspect ratio increases, these minimum drag speeds are reduced, and will fall below the stall speed of the glider. This will happen at lower aspect ratios in small gliders, which operate at higher profile drag coefficients. Increasing the aspect ratio further will improve performance less than this analysis suggests.A detailed analysis is developed to calculate the optimum shape of small gliders. Profile drag increases with aspect ratio, owing to the fall in the Reynolds number, while induced drag falls with increasing aspect ratio. Minimum drag will be encountered and hence the glide angle will be minimized at intermediate values of aspect ratio. Best glide angles are achieved at low speeds (high lift coefficients) and the optimum aspect ratio increases with the mass of the glider.Small natural gliders possess large, low aspect ratio wings. The aspect ratios are generally somewhat below those which would produce the best glide angle at stall speed, but should give a reasonable performance over a range of speeds.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02565.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Green turtles nest all year round on Aldabra, but nesting activity was found to be concentrated during the monsoon season (late November‐April) rather than the dry season as previously reported. More trial nests and emergences were made during the dry season. This was considered to be the result of difficulties in nesting during this time of the year rather than to more females attempting to nest, because fewer nests were dug during this season. The number of beaches being used by the turtles has apparently increased but no clear reason could be provided for the varying levels of use of different beache

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02566.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In many parts of the world feral animals have been reported to have severe effects on marine turtle hatchling production. In this study, green turtle (Chelonia mydas) hatchlings were shown to be an important component of the diet of the feral cat (Felis catus) on Aldabra Atoll, Seychelles, and feral cat activity in the coastal areas was found to be concentrated on the beaches used most intensively by turtles for nesting. The impact of the feral cat's predation on green turtle recruitment could not be determined. However, despite cat predation, the size of the Aldabran green turtle nesting population has increased considerably since human exploitation ceased.

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02567.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Measurement of urinary pregnanediol‐3‐glucuronide (PdG) provides a practical, non‐invasive method for monitoring ovarian function and pregnancy in diverse mammalian species. To date, however, methods of laboratory analysis have relied on radio‐immunoassay procedures which, because of their cost and the problems associated with the use and disposal of radioactive substances, have limited potential for routine application in zoos and other animal collections with limited laboratory facilities. The present paper reports the development of a non‐isotopic enzyme‐immunoassay for the measurement of urinary PdG in a wide range of exotic mammals and describes its application to reproductive assessment in the gorilla and rhinoceros.The assay is based on an homologous competitive binding system and utilizes antiserum raised against PdG‐bovine serum albumen and alkaline phosphatase‐PdG, prepared by the active ester technique, as conjugate. Sensitivity of the assay is between 12.5 and 25 pg/well and precision, expressed as the intra‐ and inter‐assay coefficients of variation, is between 5.3 and 7.8% and 9.2 and 16.1%, respectively. Serial dilutions of human, gorilla, orang‐utan, mangabey, blackbuck, okapi, gaur, giant panda and Indian, black and white rhinoceros urine gave displacement curves parallel to that of the PdG standard, indicating the potential of the assay for multi‐species application.The pattern of excretion of immunoreactive PdG during successive menstrual cycles and two complete pregnancies in a gorilla is described. Follicular phase levels of PdG were low (0.07–0.13 μg/mg creatinine (Cr)), in contrast to the high levels of excretion during the luteal phase (maximum values 1.5–2.1 μg/mg Cr). Mean cycle length was 29.6±1.5 days with a range of 26–34 (n = 5). The pattern of PdG excretion during pregnancy showed a slow increase during the first 60 days and a more rapid rise to values of 8–12 μg/mg Cr after 120 days, with no further consistent increase during the remaining period of pregnancy. Estimated gestation lengths were 280 and 256 days.The levels of immunoreactive PdG excreted during mid‐to‐late pregnancy varied considerably between the three species of rhinoceros, maximum values ranging from up to 10 μg/mg Cr in the Indian to 0.08 μg/mg Cr in the white rhinoceros. Despite this variation pregnancy was associated with elevated PdG excretion in all three species and each profile showed a marked fall in levels at the end of the gestation period. The results suggest potential for urinary PdG determination as a practical method of pregnancy detection in both Indian and African rhinoceros, although species differences in the relative importance of PdG as

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02568.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Six harbour seals, ages 4–8 years, were held as pairs in a 10 times 20 times 2 m tank filled with sea water, and on 60 occasions were fed a meal of a specific species of fish or cephalopod of known size. The tank was drained periodically, and harbour seal faeces were collected on a 0.5 mm sieve. Number and size of otoliths and beaks found in faeces were determined. Fifty‐eight percent of 670 fish and 37% of 36 cephalopods fed to harbour seals were represented by their otoliths or beaks in faeces. Estimated number of prey consumed was determined from the greatest number of left or right otoliths or upper or lower beaks collected in faeces. Estimated length ofprey was determined from measurements of otoliths and beaks recovered in the tank and relationships of otolith and beak measurements to prey length. Estimated number of fish eaten was not significantly different among pairs of harbour seals, but was different among species of fishes. Only 24–35% of fish species with small otoliths were represented in faeces, whereas more robust otoliths from other species were less apt to be completely dissolved. Estimated length of fishes was significantly less than lengths of fishes fed to harbour seals in 39 (76.5%) of 51 trials. Cephalopod beaks were not affected by passage through the harbour seal digestive tract. Amount of otolith dissolution was not related to species of fish; estimated fish length was underestimated by an average 27.5%. Although some (7.4%) of the otoliths were collected within 100 h after the fish were ingested, more than 90% were recovered within 24 h after the fish was eaten. Correction factors were developed which will allow researchers to estimate more reliably number and size of fish and cephalopod prey eaten by harbour

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02569.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A method is described in which a single bone, the first vertebra, is used to distinguish bone remains of juvenile salmon (Salmo salar) and trout (Salmo trutta) with 90% certainty. A single regression of salmon and trout first vertebra‐width versus fish‐length of fish predicted the latter with an accuracy of ±<10 mm (95% confidence limits) for salmonids of 45–150 mm fish‐length. First vertebrae were assigned to salmon or trout based on three visual characters with 89%,–90% certainty. Salmon are more variable than trout for the three characters. Of first vertebrae, 6.5% were not readily identifiable as either salmon or trout, and a further 3.0%) were misclassified using ou

ISSN:0952-8369    

DOI:10.1111/j.1469-7998.1989.tb02570.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY