The young at foot of red kangaroos and the wallaroo group are weaned at the end of their first year. The weaning time is often given as 365 days, but it may vary considerably. As weaning approaches, the young feeds from its mother less frequently. The young may pester the mother, but she increasingly ignores it and finally she prevents it suckling at all. This period of weaning may take only a couple of days. In some cases, in all species, suckling is extended, especially with a female young which may have long associations with there mothers. In these case suckling may have a social rather than a nutritional purpose.
No marked change in the relationship between and young occurs at weaning. The separation is gradual and, at least in the case of female young, some recognition and association may continue well into adult life. At the beginning of this stage the young is still frequently associated with its mother, following her, lying with her and feeding and drinking with her. This pattern can persist until sexual maturity, with the mother and young still grooming and playfully sparring. At sexual maturity males tend to leave their mothers, but whether they all disperse widely is not clear. Female kangaroos also seem to wander at this stage, but many eventually set up home-ranges and so may still be a part group or mob. With grey kangaroos this association is obvious. Daughters may never disperse far and may well continue to be a part of the basic 'group'. Sons usually disperse from their mothers home range one or two years after weaning.
Differences in the care of female and male young have been suggested. The female kangaroo seems to play an active role in the rearing process and to make different energy investments depending on the sex of the offspring and the environmental conditions. This suggestion of differential investment is related to the notion that, while a daughter will probably produce a few young in her life, a successful male can produce many. It has been observed at Wallaby Creek that the time given to weaning by female eastern grey kangaroos is not generally different for males and females, but if males were weaned early they had a poorer chance of survival. Post-weaning investment was greater for female young, with mother being more active in maintaining their association with their daughters. This was offset by a greater production of sons in good seasons. Males can take advantage of good season since a male's expected lifetime reproductive success is likely to be influenced by rapid early growth and good physical condition. How the mother influence the sex ratios is unclear.
Recently at Fowlers Gap Research Station Debbie Ashworth, a PhD student, found another pattern of differential investment, in euros. Euro females are conservative in their reproductive activities and stop breeding during drought than do red kangaroos. Even so, following a poor rainfall in 1991 only about half the pouch young survived to weaning. The majority of deaths were in the eight month which is just prior to, or at pouch exit. This is the time of maximum growth and highest lactational demand on the mothers on the mothers. In these conditions the mothers put more effort into the raising of the males, perhaps in the 'hope' of producing a large successful male. this differential investment was indicated by the observation that mothers successfully rear a male young are much less likely to successfully rear the next young because of the declining body condition. If the previous young was a male only fifty per cent or so of the next young were successfully reared, as compared with eighty-six percent the previous surviving offspring was a female. The mothers did appear to compensate the female young by letting them associate longer. Males associate with the mothers six or seven months after pouch emergence, compared with about nine months for females; daughters have been seen in the company of their mothers for over 3.5 years.
It has been suggested that females may even terminate the life of a pouch young if it is the 'wrong' sex for the times. Such behaviour has often been suggested as a god reproductive strategy, but it has been difficult to demonstrate. Debbie Ashworth found that in poor times euro mothers reared fewer males. While the sex ratio at birth is 1:1, in drought females formed a higher portion of the pouch inhabitants. this suggestion is that mothers dispose of some male young at a very early age, perhaps within the first couple of weeks.