摘要:

ABSTRACTKangaroo is taken as a general term embracing all members of the marsupial family Macropodidae, although special reference is made to the larger speciesMegaleia rufa, Macropus robustus, M. giganteus and M. fuliginosus.The origin and evolution of the Metatheria is traced from their divergence from the Eutheria during the early Cretaceous. The entry of Metatheria into Australia probably took place during the Eocene via Antarctica. During the Pliocene there was a marked radiation, within this stock, of forms adapted for grazing. The biology of modem species is considered in relation to their distribution in and adaptation for hot, arid areas with seasonally poor quality food.Kangaroos are efficient homeotherms and their main avenue of heat loss at high temperatures is by panting, with sweating and saliva‐spreading in extreme conditions. Their low level of oxygen metabolism is of advantage in hot arid conditions. post‐partum fertilization is maintained in the uterus during pouch‐suckling of another young, may be an adaptation to allow replacement of young lost by accident or drought, but it may also be 3 general reproductive adaptation of marsupials.The water relations of kangaroos demonstrate a high degree of adaptation to an arid environment. The marsupial characteristic of low body water turnover is combined with high total body water and the capacity to survive weight loss during dehydration typical of ruminant and ruminant‐like animals. In addition, desert kangaroos exhibit the ability of many other desert‐adapted mammals to reduce water loss by evaporation and from urine and faeces during dehydration, and to recycle urea when nitrogen and water are in short supply.The large kangaroos are well adapted to the utilization of poor quality food, with ruminant‐type digestion and nitrogen and water conservation by urea recycling. The diet of large kangaroos includes a large proportion of grass, and does not generally overlap greatly with that of sheep. In kangaroos of arid and semi‐arid areas, food, water and shelter are important factors controlling distribution, with food the most important.Reproduction in kangaroos is greatly affected by the severe environmental conditions imposed by drought. The onset of sexual maturity in females is delayed, there is increased mortality of pouch‐young due to failure of lactation, and if drought continues, females enter anoestrus and breeding ceases. Embryonic diapause, whereby a dormant embryo from aThe family Macropodidae includes some of the most social marsupials. The large, partly diurnal grazing animals of open habitat generally exhibit some form of group cohesion, with a low level of social organization.In the natural regulation of numbers, predators and disease appear relatively unimportant. Rainfall via its effect on food supply is a most important factor controlling numbers. Other such factors are habitat destruction, which is most significant for small species, and commercial exploitation by shooting, which is most significant for large species. However, regulations arein force to control shooting of the large species and there is little likelihood of their extinction from t

ISSN:0305-1838    

DOI:10.1111/j.1365-2907.1974.tb00347.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY