ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00242.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe Sirenia along with the elephants and hyraxes form the Super‐Order Paenungulata. They are the only fully aquatic mammalian herbivores and are represented by three species of manatees (Trichechidae), the dugong and the now extinct, Steller's sea cow (Dugongidae). Sirenians are non‐ruminant herbivores that have specialized hind‐gut fermentation in a large paired caecum at the juncture of the large and small intestines. The stomach is relatively small and is characterized by a unique cardiac gland which contains most of the digestive‐enzyme secreting cells. Little is known of the digestive physiology of sirenians. The metabolic rate of the manatee is very low in comparison to other mammals and may even represent the lowest weight‐specific metabolic rate for any mammal known. Metabolic rates forDugonghave not yet been determined. Foods and feeding habits of these species are reviewed both qualitatively and quantitatively. Manatees consume approximately 896 of their total body weight in aquatic plants daily, whereas the same value for the dugong is about 14%. Digestibilities of aquatic plants vary from 45 to 70% for manatees and a singlein vitromeasurement forDugongwas 83% for sea‐grass. The chemical composition of various plants consumed by wild and captive sirenians are presented and their value in the nutritional ecoloev of the different species i

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00243.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe reproductive cycles of captive female Northern fur seals (Callorhinus ursinus) were unaffected over two consecutive years by a photoperiod that differed substantially from that of the natural range. Breeding was observed in July and August, or at the same time as in the wild. Growth was comparable in captive and wild fetuses, indicating a similar timing of delayed implantation of the blastocysts.

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00244.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

SummaryAn examination of twenty‐four male babirusa skulls indicates that the long tusks have an important function in intraspecific fighting. The upper tusks have developed a shielding, protective function whilst the lower tusks are offensive and daggerlike. As the upper tusks do not hone the lower canines as in other suids, the babirusa male actively sharpens his lower tusks on trees. Wear patterns on the tusks suggest that mainland babirusa use the upper tusks to interlock and hold their opponents' lower tusks during combat. In the Buru race this hooking function appears to have been lost and the upper tusks have a butting function instea

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00245.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

AbstractThe wheel‐running activity of caged mammals has been misinterpreted for many years as a measure of ‘general activity’. A review of the literature and recent experimental evidence suggests that this behaviour has a far more specific function for the animal, and that its major and invaluable experimental use lies as both a field and laboratory tool for the studies of particular forms of migration. This new interpretation allows a greater understanding of the motivations underlying this widely‐monitored behaviour.SummaryIt is apparent that the nature of the response to an activity‐wheel has been greatly misunderstood for many years. The behaviour appears to be far more specific than previously thought, reflecting a type of inherent response which is not evident when activity is recorded by other methods. This report indicates that the wheel is used by a caged animal when the individual is motivated to reach an unattainable resource. This results in an urge to travel, either to remove itself from the immediate area, or to search for specific resources. It is proposed that when the goal is perceptually not present, the activity wheel is a specific monitor of ‘exploratory migration’, and reflects the urge to collect information about the location of resources. It implies, therefore, that the use of the activity‐wheel as a simple measure of ‘general activity’ should cease; the major future uses of this particular activity recording device should be in the studies of the daily, ontogenetic and seasonal variation in the incidence of exploratory migration, and the influence upon it of other environ‐ mental factors, as well as a method of investigating goal‐orientation, both in the field and the laboratory. This new interpretation provides a more precise explanation of what is being measured in wheel‐running experiments, and should result in a more specific use of wheel‐

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1981.tb00246.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY