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Proceedings of the First Symposium on Marsupials in New Zealand

General Discussion

General Discussion

WAGSTAFF. Dr Bell, you said that the security of the young depends to a large extent on the female. David Pepper-Edwards of the Auckland Zoo says that female wallabies often eject their joeys when disturbed or handled. Have you noticed this with the possums you've handled? When you weigh possums do the females take back their young or tend to eject them?

B.D. BELL. Most animals we handle are used to being caught and examined in cage traps so are relatively quiet during the handling process. The exceptions are generally new animals or those only caught a few times previously; the occasional individual remains excitable despite being caught many times. Generally we drug the female before examining her pouch and young and any young that are free of the teat are accepted back without difficulty - we have no evidence of pouch young being ejected or affected adversely by the female. Certainly it can be physically a little difficult to return older back young into the pouch, and those that are released riding on the back of the mother are occasionally knocked-off by vegetation, e.g. supplejack, as she runs away. However, the young is generally found again by the female.

COLEMAN. I noticed in 1968 your possums' breeding success and general weights were down. In 1968 in the South Island there was a very rugged winter with very poor success also. Last year there was very heavy snow on the West Coast and very poor survival. There were just no possums around when traps were out and there was no sign of them - they were probably holed up.

B.D. BELL. Dr Crawley was operating in the 1968 autumn of the Wahine storm -from all accounts the rainfall was higher than usual that autumn.

FITZGERALD. With the correlations you have run, have you in fact done anything in relation to the effect of rainfall?

B.D. BELL. There were few significant correlations between various rainfall parameters taking the monthly average. However a closer look at rainfall over the few days prior to capture, for instance, is worth doing. We know heavy rainfall can markedly affect the activities of the possum, so a period of sustained wet weather could be deliterious, especially if cold also.

YOUNG. You demonstrated the range of variation in productivity of your adult age class of possums. There must then be an extraordinary variation in the productivity of one and two year olds.

B.D. BELL. Yes, indeed, there is considerable variation in the first and second year age classes in terms of breeding performance. 1969 and 1971 were the only years in which first years ever attempted to breed and those two were the 'better' years generally.

MEADOWS. Can you give me any figures on the maturity of the males?

B.D. BELL. On external criteria - scrotal development of males and pouch development of females - the two sexes evidently mature about the same time. Most are not sexually mature at the end of their first year in the Orongorongo study but the situation may be different in other areas of New Zealand.

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