Specific changes in milk composition during lactation in the tammar wallaby (Macropus eugenii) were correlated with the ages of the developing pouch young (PY). The present experiment was designed to test the hypothesis that the sucking pattern of the PY determines the course of mammary development in the tammar wallaby. To test this hypothesis, groups of 60-day-old PY were fostered repeatedly onto one group of host mothers so that a constant sucking stimulus on the mammary gland was maintained for 56 days to allow the lactational stage to progress 42 days ahead of the age of the young. Analysis of the milk in fostered and control groups showed the timing of changes in the concentration of protein and carbohydrate were essentially unaffected by altering the sucking regime. The only change in milk protein secretion was a small delay in the timing of down-regulation of the secretion of whey acidic protein and early lactation protein in the host tammars. In addition, the rates of growth and development of the foster PY were significantly increased relative to those of the control PY because of ingesting more milk with a higher energy content and different composition than normal for their age. The present study demonstrates that the lactating tammar wallaby regulates both milk composition and the rate of milk production and that these determine the rates of PY growth and development, irrespective of the age of the PY.
The swamp wallaby (Wallabia bicolor) is a common, medium-sized, browsing macropodid marsupial that is unique in many ways. Relatively little is known about the reproductive biology of this species. Previous studies have proposed that the swamp wallaby has a pre-partum oestrus because the gestation period (x = 35.5 days, n = 4) is on average longer than the oestrus period (x = 31.0 days, n = 5) and the period from the removal of pouch young (RPY) to mating (x = 26.0 days, n = 3). In the current study, the period from RPY to birth was confirmed at x = 31.25 days (n = 4) in captive animals, consistent with a pre-partum oestrus. A growth curve for swamp wallaby pouch young was constructed from the progeny of captive animals to estimate the age and date of birth of young in a wild, culled population in South Gippsland, Victoria, and the reproduction of females in the wild throughout the year was examined. Young were born in every month of the year, with no statistically significant variation in the number of young born in each month. Females did not have a period of seasonal anoestrus and conceived throughout the year. Female swamp wallabies in South Gippsland bred continuously throughout the period of this study.
This study describes pubertal changes in testes and epididymides and seasonal changes in the adult male reproductive organs and plasma androgen concentrations of the swamp wallaby ( Wallabia bicolor ). Pre-pubescent males had testes with solid seminiferous cords and spermatogenesis only to the stage of gonocytes. Their epididymides had empty lumina along their entire length. The testes of three males undergoing puberty had some lumen formation and mitotic activity. Their epididymides were similar in appearance to those of adult males but were entirely devoid of any cells within the lumen of the duct. Three other pubescent males showed full lumen formation in the testes and spermatogenesis up to the elongating spermatid stage. Their epididymides were similar in appearance to those of adult males but with no spermatozoa in the duct. However, cells of testicular origin were found in the lumen of the duct in all regions suggesting that testicular fluids and immature germ cells shed into the rete testes flow through the seminiferous tubules into the epididymis before the release of mature testicular spermatozoa. The weights of testes and epididymides of adult males showed no change throughout the year but prostate weight and plasma androgen concentrations varied significantly with season, with maximums in spring and summer and minimums in winter. The volume fraction of Leydig cells and seminiferous tubules was significantly lower in winter than in summer; but, despite this, maturing spermatozoa were found in the testes throughout the year. Females in the area conceived year-round, suggesting that seasonal changes in the male reproductive tract did not prevent at least some males from breeding throughout the year.
The swamp wallaby (Wallabia bicolor) is a common though unique macropodid marsupial, but much of its basic biology is unstudied. In Victorian populations, seasonal breeding was inferred from pouch young measurements of a small number of animals (1,2). The only other published information about seasonality is for two NSW populations, only one of which appeared to breed seasonally(3). In this study, data was obtained from 253 adult swamp wallabies collected from culled animals throughout the year in southeastern Victoria from 2000 to 2003. The sex ratio was 1 female:1.84 males, which is comparable to the NSW populations. Both studies are based on shot specimens so it is uncertain whether the sex ratio bias reflects true population trends or a shooting bias. 75.3% of females were pregnant (66.3% blastocysts in diapause, 8.5% early embryos and 3.9% were near-term fetuses). Pregnancies other than blastocysts in diapause were found only in spring or summer. 86.5% of adult females had pouch young. Date of birth was interpolated from pouch young head length. The number of pouch young born in summer (n = 23), as well as the number of pouch young born in spring (n = 23) was significantly higher than the number born in winter (n = 11) (P<0.05 for both). Correspondingly, males had relatively larger testes and prostates in summer than winter (P<0.05). These results indicate that swamp wallabies in southeastern Victoria have a seasonal pattern of reproduction.
SINCE the development of soft-walled traps suitable for the capture of small to medium-sized macropodids (Kinnear et al. 1988; Pollock and Montague 1991), traps of similar design have been used to capture swamp wallabies (Wallabia bicolor) by a number of workers (Wood 2002; Ben-Ami 2005; Paplinska 2005; B Parker, pers. comm.). Although immobilising drugs delivered by syringe darts have also been used to capture W. bicolor successfully (Troy et al. 1992), this species is difficult to dart relative to other similar sized wallabies (Wood 2002), and once darted can be hard to find within its often densely vegetated habitat (Pollock and Montague 1991). The difficulty of locating drugged animals in dense vegetation or steep terrain also makes the use of bait laced with diazepam or alpha chloralose (e.g., Norbury et al. 1994) impractical. Other capture techniques, such as stunning and netting (e.g., Taggart et al. 2003) are also rendered ineffective due to the habitat selected by this species.
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