Assessing body condition in the platypus (Ornithorhynchus anatinus): a comparison of new and old methods

Body condition is an important aspect of the health of any animal. The current standard method of body condition assessment in the platypus is the tail volume index (TVI). Although the tail is the largest repository of fat in the platypus, the reliability of TVI has not been adequately demonstrated. The aims of this study were, first to assess performance of the TVI, and second, to develop and evaluate performance of new techniques for routine field assessment of platypus body condition. Morphometric data were collected under anaesthesia from 137 adult wild platypuses (74 males, 63 females) captured in north-west Tasmania; ultrasound images of tail fat were also collected from 100 of these individuals (54 males, 46 females). Three new indices for platypus body condition were identified. An objective tail fat index (Relative Tail Fat Volume: RTFVTBL) was developed, based on cross-sectional area measurements taken from detailed ultrasound images compared with total body length (TBL). Two body condition indices intended for routine field use were developed – one based on body mass (mb) and bill width (BW) (Body Condition Index; BCIBW), and the other based on a single linear ultrasonographic measurement of tail fat depth and BW (Relative Fat Depth; RFDBW). Results indicated that RFDBW outperforms TVI as an index of platypus tail fat. Further work, however, is needed to determine the relationship between tail fat and total body fat in the platypus before conclusions can be drawn about the effectiveness of BCIBW as a body condition index.

Energetics of foraging and locomotion in the platypus Ornithorhynchus anatinus

We measured the energy requirements of platypuses foraging, diving and resting in a swim tank using flow-through respirometry. Also, walking metabolic rates were obtained from platypuses walking on a conventional treadmill. Energy requirements while foraging were found to depend on water temperature, body weight and dive duration and averaged 8.48 W kg(-1). Rates for subsurface swimming averaged 6.71 W kg(-1). Minimal cost of transport for subsurface swimming platypuses was 1.85 J N(-1)m(-1) at a speed of 0.4 m s(-1). Aerobic dive limit of the platypus amounted to 59 s. Metabolic rate of platypuses resting on the water surface was minimal with 3.91 W kg(-1) while minimal RMR on land was 2.08 W kg(-1). The metabolic rate for walking was 8.80 W kg(-1) and 10.56 W kg(-1) at speeds of 0.2 m s(-1) and 0.3 m s(-1), respectively. A formula was derived, which allows prediction of power requirements of platypuses in the wild from measurements of body weight, dive duration and water temperature. Platypuses were found to expend energy at only half the rate of semiaquatic eutherians of comparable body sizes during both walking and diving. However, costs of transport at optimal speed were in line with findings for eutherians. These patterns suggest that underwater locomotion of semiaquatic mammals have converged on very similar efficiencies despite differences in phylogeny and locomotor mode.

Current Research On The Platypus, Ornithorhynchus anatinus In Tasmania: Abstracts From The 1999 'Tasmanian Platypus Workshop'

The platypus is found in a high proportion of the river catchments in Tasmania including King and Bruny Island and possibly Three Hummock Island (Rounsevell et al., 1991, Grant, 1992, Hird and Paterson, 1995, Connolly and Obendorf, 1998). It is found in a wide variety of habitats, including urban streams, farm dams, cave systems, estuaries, pristine rivers and alpine lakes (references in Connolly and Obendorf, 1998). However, despite its widespread occurrence, and apparent differences from its mainland relatives, until recently little detailed research had been carried out on the species in this state. In order to review and discuss the preliminary results of the upsurge in research into platypus in the last six years and to identify management issues and priorities for further work a one day 'Tasmanian Platypus Workshop' was held at the University of Tasmania in May 1999. The workshop aimed to improve co-ordination between researchers studying platypus, to ensure greater opportunities for efficiencies in research which would in turn minimise the impacts of research on platypus populations. These proceedings contain the abstracts of the talks presented at the meeting and the outcomes of the subsequent discussion.

The Breeding biology of Pseudocheirus peregrinus viverrinus on FLinders ISland, Bass Strait

Reproduction in Pseudocheirus peregrinus viverrinus in coastal teatree woodland on Flinders Island was seasonal. The main birth season was from May to August. The mean duration of lactation was 29 weeks. The duration of lactation for multiparous females that bred twice in a year was significantly shorter than that of multiparous single breeders. In general the young left the pouch during early spring and were fully weaned by the early summer months. In contrast to populations of P. peregrinus inhabiting similar woodland in Victoria only a few multiparous females (6-9%) gave birth to a second litter in the springlsummer months on Flinders Island. The mean litter size (1.84) and annual fecundity of the population (1.91 offspring per female) were lower than those reported for three populations of Pseudocheirus peregrinus in Victoria. It is suggested that the low occurrence of spring/summer births and low fecundity of P. p. viverrinus on Flinders Island may be related to the age and nutrient status of their coastal teatree forest habitat. The body mass of P. p. viverrinus was higher than previously recorded for P. peregrinus. The adult body mass of females ranged from 948 to 1082 g. Adults showed seasonal variation in body mass with most females losing weight during the late spring and summer months coincident with late lactation. It is proposed that the larger body size of P. p. viverrinus on Flinders Island is a result of release from predation pressure and/or interspecific competition.

Isolation, partial sequence and asynchronous appearance during lactation of lysozyme and alpha-lactalbumin in the milk of a marsupial, the common ringtail possum (Pseudocheirus peregrinus)

1. Lysozyme and alpha-lactalbumin from the milk of the common ringtail possum have been purified and partially sequenced. 2. The lysozyme had similar enzymic activity to the c-type lysozyme of the domestic hen and 43% homology over the N-terminal 49 residues. 3. alpha-Lactalbumin was present in the milk in two biologically active forms; the more acidic form had 66% sequence homology with the N-terminal 35 residues of red-necked wallaby, 54% with human and 43% with bovine alpha-lactalbumin. 4. SDS polyacrylamide-gel electrophoresis of milk samples showed that alpha-lactalbumin was present in the milk throughout lactation but that lysozyme first appeared only in mid-lactation. The implications of this functional adaptation are discussed.