Pouch Exit Research Articles

Maternal resource allocation adjusts to timing of parturition in an asynchronous breeder

Environmental variation affects foraging decisions and resources available for allocation among competing life-history traits. In seasonal environments, variation in breeding phenology leads to differences in relative timing of resource intake and expenditure, which can lead to variation in maternal allocation tactics. Monitoring maternal allocation to fetal growth in wild mammals is challenging, however, and few studies have linked seasonal effects of forage and maternal condition to early offspring development. Asynchronous parturition and short gestation make kangaroos ideal for studying phenological effects on very early growth, since pouch young born in different seasons can be measured during stages equivalent to in utero development for eutherian mammals. Over 4 years, we recaptured 68 eastern grey kangaroo mother-young pairs with parturition dates spanning 5 months to evaluate how birthdate affects maternal allocation to offspring growth before pouch exit. Structural equation modeling revealed that mothers that gave birth in autumn gained mass during lactation, and their young grew faster than young born in early summer. When later lactation coincided with poor winter forage and cold temperatures, mothers prioritized maintenance of their own mass over offspring growth. Differences in maternal mass change and allocation to early and late-born young suggest that seasonal resource availability influenced tactics of resource storage and expenditure. Our results provide a mechanistic link between reproductive phenology, seasonal forage, and allocation trade-offs in wild mammals, and demonstrate a clear effect of maternal mass change on growth of young during a phase that occurs in utero for eutherian mammals. Capital and income breeding are often presented as opposing tactics of resource provisioning. Many species, however, use a combination of stored and concurrent resources to reproduce. In seasonal environments, reproductive phenology should affect the relative timing of resource acquisition and expenditure, which could affect maternal allocation to offspring. We used repeated captures of mother-young kangaroo pairs and path analysis to explain how maternal allocation tactics adjust to season of parturition. Mothers that timed later lactation with cold weather and low winter forage relied more heavily on stored resources for reproduction and allocated less to offspring growth. Flexibility in foraging tactics may explain the variability in kangaroo parturition date by allowing mothers to use stored energy to sustain reproduction during periods of scarce forage.

A bipedal mammalian model for spinal cord injury research: The tammar wallaby

Background: Most animal studies of spinal cord injury are conducted in quadrupeds, usually rodents. It is unclear to what extent functional results from such studies can be translated to bipedal species such as humans because bipedal and quadrupedal locomotion involve very different patterns of spinal control of muscle coordination. Bipedalism requires upright trunk stability and coordinated postural muscle control; it has been suggested that peripheral sensory input is less important in humans than quadrupeds for recovery of locomotion following spinal injury. Methods: We used an Australian macropod marsupial, the tammar wallaby (Macropus eugenii), because tammars exhibit an upright trunk posture, human-like alternating hindlimb movement when swimming and bipedal over-ground locomotion. Regulation of their muscle movements is more similar to humans than quadrupeds. At different postnatal (P) days (P7–60) tammars received a complete mid-thoracic spinal cord transection. Morphological repair, as well as functional use of hind limbs, was studied up to the time of their pouch exit. Results: Growth of axons across the lesion restored supraspinal innervation in animals injured up to 3 weeks of age but not in animals injured after 6 weeks of age. At initial pouch exit (P180), the young injured at P7-21 were able to hop on their hind limbs similar to age-matched controls and to swim albeit with a different stroke. Those animals injured at P40-45 appeared to be incapable of normal use of hind limbs even while still in the pouch. Conclusions: Data indicate that the characteristic over-ground locomotion of tammars provides a model in which regrowth of supraspinal connections across the site of injury can be studied in a bipedal animal. Forelimb weight-bearing motion and peripheral sensory input appear not to compensate for lack of hindlimb control, as occurs in quadrupeds. Tammars may be a more appropriate model for studies of therapeutic interventions relevant to humans.

A bipedal mammalian model for spinal cord injury research: The tammar wallaby.

Background: Most animal studies of spinal cord injury are conducted in quadrupeds, usually rodents. It is unclear to what extent functional results from such studies can be translated to bipedal species such as humans because bipedal and quadrupedal locomotion involve very different patterns of spinal control of muscle coordination. Bipedalism requires upright trunk stability and coordinated postural muscle control; it has been suggested that peripheral sensory input is less important in humans than quadrupeds for recovery of locomotion following spinal injury. Methods: We used an Australian macropod marsupial, the tammar wallaby (Macropuseugenii), because tammars exhibit an upright trunk posture, human-like alternating hindlimb movement when swimming and bipedal over-ground locomotion. Regulation of their muscle movements is more similar to humans than quadrupeds. At different postnatal (P) days (P7-60) tammars received a complete mid-thoracic spinal cord transection. Morphological repair, as well as functional use of hind limbs, was studied up to the time of their pouch exit. Results: Growth of axons across the lesion restored supraspinal innervation in animals injured up to 3 weeks of age but not in animals injured after 6 weeks of age. At initial pouch exit (P180), the young injured at P7-21 were able to hop on their hind limbs similar to age-matched controls and to swim albeit with a different stroke. Those animals injured at P40-45 appeared to be incapable of normal use of hind limbs even while still in the pouch. Conclusions: Data indicate that the characteristic over-ground locomotion of tammars provides a model in which regrowth of supraspinal connections across the site of injury can be studied in a bipedal animal. Forelimb weight-bearing motion and peripheral sensory input appear not to compensate for lack of hindlimb control, as occurs in quadrupeds. Tammars may be a more appropriate model for studies of therapeutic interventions relevant to humans.

Femoral bone perfusion through the nutrient foramen during growth and locomotor development of western grey kangaroos (Macropus fuliginosus).

The nutrient artery passes through the nutrient foramen on the shaft of the femur and supplies more than half of the total blood flow to the bone. Assuming that the size of the nutrient foramen correlates with the size of the nutrient artery, an index of blood flow rate (Qi) can be calculated from nutrient foramen dimensions. Interspecific Qi is proportional to locomotor activity levels in adult mammals, birds and reptiles. However, no studies have yet estimated intraspecific Qi to test for the effects of growth and locomotor development on bone blood flow requirements. In this study, we used micro-CT and medical CT scanning to measure femoral dimensions and foramen radius to calculate femoral Qi during the in-pouch and post-pouch life stages of western grey kangaroos (Macropus fuliginosus) weighing 5.7 g to 70.5 kg and representing a 12,350-fold range in body mass. A biphasic scaling relationship between Qi and body mass was observed (breakpoint at ca. 1-5 kg body mass right before permanent pouch exit), with a steep exponent of 0.96±0.09 (95% CI) during the in-pouch life stage and a statistically independent exponent of -0.59±0.90 during the post-pouch life stage. In-pouch joeys showed Qi values that were 50-100 times higher than those of adult diprotodont marsupials of the same body mass, but gradually converged with them as post-pouch adults. Bone modelling during growth appears to be the main determinant of femoral bone blood flow during in-pouch development, whereas bone remodelling for micro-fracture repair due to locomotion gradually becomes the main determinant when kangaroos leave the pouch and become more active.

Scaling of left ventricle cardiomyocyte ultrastructure across development in the kangaroo Macropus fuliginosus.

The heart and left ventricle of the marsupial western grey kangaroo Macropus fuliginosus exhibit biphasic allometric growth, whereby a negative shift in the trajectory of cardiac growth occurs at pouch exit. In this study, we used transmission electron microscopy to examine the scaling of left ventricle cardiomyocyte ultrastructure across development in the western grey kangaroo over a 190-fold body mass range (0.355-67.5 kg). The volume-density (%) of myofibrils, mitochondria, sarcoplasmic reticuli and T-tubules increase significantly during in-pouch growth, such that the absolute volume (ml) of these organelles scales with body mass (Mb; kg) with steep hyperallometry: 1.41Mb (1.38), 0.64Mb (1.29), 0.066Mb (1.45) and 0.035Mb (1.87), respectively. Maturation of the left ventricle ultrastructure coincides with pouch vacation, as organelle volume-densities scale independent of body mass across post-pouch development, such that absolute organelle volumes scale in parallel and with relatively shallow hypoallometry: 4.65Mb (0.79), 1.75Mb (0.77), 0.21Mb (0.79) and 0.35Mb (0.79), respectively. The steep hyperallometry of organelle volumes and volume-densities across in-pouch growth is consistent with the improved contractile performance of isolated cardiac muscle during fetal development in placental mammals, and is probably critical in augmenting cardiac output to levels necessary for endothermy and independent locomotion in the young kangaroo as it prepares for pouch exit. The shallow hypoallometry of organelle volumes during post-pouch growth suggests a decrease in relative cardiac requirements as body mass increases in free-roaming kangaroos, which is possibly because the energy required for hopping is independent of speed, and the capacity for energy storage during hopping could increase as the kangaroo grows.

Composition of the milk of the quokka (Setonix brachyurus)

We investigated the composition of the milk of the quokka between 70 and 300 days post partum. From 70 to 180 days, the mean concentration of protein in the milk was 63.5 ± 6.50 g L−1. The protein levels then began to increase, peaking at 120 g L−1 towards the end of lactation. The mean lipid and total solids content were 45.0 ± 6.50 and 175.0 ± 11.77 g L−1 from 70–180 days, increasing to 150 and 250 g L−1 after permanent pouch exit. In contrast, the total carbohydrate concentration of the milk decreased from 80 to 20 g L−1 at 150 days. The concentration of lactose started to decrease at 180 days from 30 to 10 g L−1, and galactose and glucose began to rise from 1 to 9 g L−1 and 0.5 to 4.0 g L−1, respectively. The milk lipid consisted mainly of long- and medium-chain fatty acids, with no short-chain fatty acids detected. The major fatty acids present were palmitic and oleic acids, followed by linoleic, trans-vaccenic and stearic acids. The percentage composition of oleic and stearic acids varied significantly during lactation. The composition of the milk of the quokka changed during lactation, coincident with the young reaching critical milestones in its development. This finding supports the hypothesis that the composition of the milk changes to meet the nutritional needs of the developing young.

Developmental changes in ventricular myosin isoenzymes of the tammar wallaby

Ventricular myosin in eutherian mammals undergoes a perinatal change in response to a sharp rise in thyroid hormone levels during development. In this investigation, changes in ventricular myosin heavy chains (MyHCs) of the tammar wallaby (Macropus eugenii) from early pouch life to adulthood were analysed using native gel electrophoresis, SDS-PAGE and western blotting. Adult wallaby ventricle showed three myosin isoenzymes, V(1), V(2) and V(3); western blots using specific anti-alpha-MyHC and anti-beta-MyHC antibodies showed their MyHC compositions to be alphaalpha, alphabeta and betabeta, respectively. Ventricular muscle in early pouch joeys expressed predominantly beta-MyHC. Up to 200 days, the time of initial pouch exit, alpha-MyHC content was around 5%. Thereafter, there was a sharp increase of alpha-MyHC expression to 35% by 242 days of age, eventually falling back to 23% in the adult. These changes correlate with known surges in plasma levels of thyroid hormones around pouch exit. The results suggest that ventricular myosins in a marsupial mammal also undergo a developmental change, and that marsupial ventricular myosins are thyroid responsive as in eutherians. The increased alpha-MyHC expression empowers the heart to meet the enhanced cardiovascular demands of out-of-pouch activity and the thermogenic action of thyroid hormones.

Growth and development of the southern hairy-nosed wombat, Lasiorhinus latifrons (Vombatidae)

There are few published studies on breeding and reproduction in hairy-nosed wombats and little information available on growth and development of pouch young. At a field site near Swan Reach in the Murraylands of South Australia morphometric measurements of 353 young southern hairy-nosed wombats and notes on their development were recorded. These data were combined with growth data collected from repeat measures of 10 mother-reared and 5 hand-reared joeys in order to establish information for aging young of this species and to plot developmental changes. Young weighed ~0.4 g at birth and had a head length (HL) of ~5.2 mm. Head length was the most accurate body parameter from which to assess age. Growth of pouch young was linear between birth and ~Day 310 with head length growing at ~0.4 mm HL per day. After Day 300 growth slowed, represented by a polynomial equation. Eyes were open at 5 months and pouch young started to develop fur at 5–6 months of age. Most young were permanently out of pouch at 9 months of age, and were weaned between 11 and 13 months, when they weighed 6–7 kg. Young remained in the burrow for 1–2 months following pouch exit before venturing above ground at night.

Milk composition and growth in the southern brown bandicoot, Isoodon obesulus (Marsupialia:Peramelidae)

Milk and growth data from six litters of southern brown bandicoots (Isoodon obesulus) from south-eastern Tasmania were analysed. Five of these were born in the wild and one was born in captivity. The quantitative changes in milk composition were examined for total protein, carbohydrates (hexose and lactose), lipid, dissolved solids, and estimated energy content. During ‘early-phase’ lactation (before Day 30) protein levels were 10.5 g (100 mL)–1, hexose 0.34 g (100 mL)–1, lipids 10.4 g (100 mL)–1, and solids 27.3 g (100 mL)–1. ‘Mid-phase’ milk (Days 31–45) showed an increase in all constituents: protein 13.8 g (100 mL)–1, hexose 1.66 g (100 mL)–1, lipid 12.2 g (100 mL)–1, and solids 41.4 g (100 mL)–1. Protein and hexose levels decreased in ‘late-phase’ milk (Day 46–60) to 11.3 g (100 mL)–1, and 1.58 g (100 mL)–1, respectively, and the amount of lipids and dissolved solids increased to 26.4 g (100 mL)–1, and 52.3 g (100 mL)–1, respectively. There was no evidence of lactose in milk from the latter half (final 28 days) of lactation. Total milk energy increased from 6.0kJmL–1 in early-phase milk, to 8.9 kJ mL–1 in mid-phase, and 12.0 kJ ml–1 in late-phase. Changes in body mass, head, tail, and pes lengths were examined for 16 pouch young. Instantaneous relative growth rates were calculated for the final 42 days of lactation, revealing a decrease in overall growth rates from 14.0% increase in bodyweight per day in early-phase, to 7.8% daily during mid-phase, and 3.5% daily increase during late-phase lactation. Analysis of the relationship between milk and growth in I. obesulus demonstrates that morphological and developmental changes, especially the development of endothermy and time of first pouch exit, directly correlate with changes in growth rates, milk energy, and milk composition.

Cross-fostering, growth and reproductive studies in the brush-tailed rock-wallaby, Petrogale penicillata (Marsupialia:Macropodidae): efforts to accelerate breeding in a threatened marsupial species

Pouch-young removal and cross-fostering trials were undertaken in the brush-tailed rock-wallaby, Petrogale penicillata, to assess whether this procedure could be used to accelerate breeding and recruitment in this threatened marsupial species. Basic reproductive data, lacking at the time of the study, were also collected. Eighteen pouch young, weighing 1–106 g, were fostered to either tammar wallaby, Macropus eugenii, or yellow-footed rock-wallaby, Petrogale xanthopus, surrogate mothers. Sixteen P. penicillata pouch young were transferred to surrogate mothers whose own young were greater or equal in size to the P. penicillata young being transferred. Fourteen of these young survived (88%). Two of the P. penicillata pouch young were transferred to surrogate mothers whose own young was smaller in size than the P. penicillata young being transferred. Neither survived. Growth curves for pouch young on mothers and surrogate mothers were estimated. P. penicillata young reared by surrogate mothers grew at a similar rate, and were weaned at a similar age, to the pouch young of the foster species. Like other rock-wallaby species, P. penicillata underwent embryonic diapause and had a gestation period of ~30 days. Permanent pouch exit occurred at ~200 days and young became sexually mature at ~23 months for males and no later than 21 months for females. This study clearly demonstrates that pouch young of P. penicillata, as small as 1 g (~8 days old), can be removed and cross-fostered successfully. These procedures can be used to accelerate breeding and recruitment by up to six times in this threatened species provided an adequate source of surrogate mothers is available.

Energy requirements of the red kangaroo (Macropus rufus): impacts of age, growth and body size in a large desert-dwelling herbivore.

Generally, young growing mammals have resting metabolic rates (RMRs) that are proportionally greater than those of adult animals. This is seen in the red kangaroo ( Macropus rufus), a large (>20 kg) herbivorous marsupial common to arid and semi-arid inland Australia. Juvenile red kangaroos have RMRs 1.5-1.6 times those expected for adult marsupials of an equivalent body mass. When fed high-quality chopped lucerne hay, young-at-foot (YAF) kangaroos, which have permanently left the mother's pouch but are still sucking, and recently weaned red kangaroos had digestible energy intakes of 641+/-27 kJ kg(-0.75) day(-1) and 677+/-26 kJ kg(-0.75) day(-1), respectively, significantly higher than the 385+/-37 kJ kg(-0.75) day(-1) ingested by mature, non-lactating females. However, YAF and weaned red kangaroos had maintenance energy requirements (MERs) that were not significantly higher than those of mature, non-lactating females, the values ranging between 384 kJ kg(-0.75) day(-1) and 390 kJ kg(-0.75) day(-1) digestible energy. Importantly, the MER of mature female red kangaroos was 84% of that previously reported for similarly sized, but still growing, male red kangaroos. Growth was the main factor affecting the proportionally higher energy requirements of the juvenile red kangaroos relative to non-reproductive mature females. On a good quality diet, juvenile red kangaroos from permanent pouch exit until shortly after weaning (ca. 220-400 days) had average growth rates of 55 g body mass day(-1). At this level of growth, juveniles had total daily digestible energy requirements (i.e. MER plus growth energy requirements) that were 1.7-1.8 times the MER of mature, non-reproductive females. Our data suggest that the proportionally higher RMR of juvenile red kangaroos is largely explained by the additional energy needed for growth. Energy contents of the tissue gained by the YAF and weaned red kangaroos during growth were estimated to be 5.3 kJ g(-1), within the range found for most young growing mammals.

Thermoregulation in juvenile red kangaroos (Macropus rufus) after pouch exit: higher metabolism and evaporative water requirements.

The population dynamics of red kangaroos (Macropus rufus) in the Australian arid zone is tightly linked with environmental factors, which partly operate via the survival of juvenile animals. A crucial stage is the young-at-foot (YAF) stage when kangaroos permanently exit the pouch. We have examined the thermal biology of YAF red kangaroos during ages from permanent pouch exit until weaning. Over a wide range of environmental temperatures (ambient temperature [T(a)] -5 degrees to 45 degrees C), YAF red kangaroos had a mass-specific metabolism that was generally twice that of adults, considerably higher than would be expected for an adult marsupial of their body size. The total energy requirements of YAF red kangaroos were 60%-70% of those of adult females, which were three times their size. Over the same range in T(a), YAF red kangaroos also had total evaporative water losses equal to those of adult females. At the highest T(a) (45 degrees C), differences were noted in patterns of dry heat loss (dry conductance) between YAF red kangaroos and adult females, which may partially explain the relatively high levels of evaporative cooling by YAF. By weaning age, young kangaroos showed little change in their basal energy and water requirements (at T(a) 25 degrees C) but did show reduced mass-specific costs in terms of energy and water use at extremes of T(a) (-5 degrees and 45 degrees C, respectively). In their arid environment, typified by unpredictable rainfall and extremes of T(a), young red kangaroos may need to remain close to water points, which, in turn, may restrict their ability to find the high-quality forage needed to meet their high energy demands.

Breeding biology of captive, reintroduced and wild greater bilbies, Macrotis lagotis (Marsupialia : Peramelidae)

The breeding biology and growth of Macrotis lagotis was investigated using captive stock in Alice Springs and Dubbo and a reintroduced population at Watarrka National Park. Individuals of M. lagotis reached sexual maturity at about six months of age and continued growing until about 18 months old. Pouch life and weaning took approximately 90 days and females produced up to four litters per year. Litters comprised 1–3 young. Average litter size at pouch exit ranged from 1.0 to 1.88, depending on whether animals were studied in captivity or under reintroduced free-range conditions. Females commonly continued breeding past the age of four years and longevity extended to 10 years in captivity. In comparison, the most animals caught in the wild were estimated to be less than 12 months old. Animals in the reintroduced population exhibited a greater reproductive output than the captive populations examined. However, survivorship was far greater for animals in captivity. An intensively managed captive population may achieve a three-fold increase in size in a 12-month period.

Production of milk and nutrition of the dependent young of free-ranging koalas (Phascolarctos cinereus).

The production of milk by lactating females, and energy expenditure and foliage intake of their dependent young, were investigated in free-ranging koalas. Koalas had the lowest mass-specific daily milk-energy production at peak lactation so far recorded in a mammal, but the duration of reproduction was 58% longer than the combined marsupial and eutherian average. As a consequence, the total energy input to reproduction in koalas was similar to that in other mammals. We propose that the prolonged lactation and low daily rate of energy transfer to the young by female koalas is an adaptation to the low energy availability from their diet of Eucalyptus foliage. Energy requirements (field metabolic rates) of young koalas were lower than those expected for typical marsupials (only 60% at permanent pouch exit), which may be a necessary preadaptation that allows the low rate of maternal energy transfer. However, the energy requirements of the adult females were no lower than expected for marsupials. This pattern of energy requirements and age resulted in a linear relationship between field metabolic rate and mass for the koalas in this population. Differences in milk production between the years of the study coincided with fluctuations in the availability of preferred young foliage, which suggests that lactational output by koalas may be flexible and affected by diet quality. Despite the interannual differences in milk production, growth of the young was similar in the two years.

Composition of the Milk of the Koala, Phascolarctos cinereus, an Arboreal Folivore

The composition of milk from free-ranging koalas was examined as part of a study of the energetics of reproduction in the koala, an arboreal folivorous marsupial that displays a number of energetically conservative characteristics often associated with arboreality and folivory. Koala milk composition showed a number of deviations from the general marsupial pattern that suggest koalas have adopted a lactational strategy different from that of most other marsupials previously studied. Milk solids decreased at the time of exit of the young from the pouch, in contrast with the solids content of the milk of most marsupials, which rises at that time. Lipids provided the major source of milk energy even in early to midlactation and did not rise at pouch exit, unlike lipid levels in other marsupials, which are low in early to midlactation and rise sharply at pouch exit to high levels in late lactation. The carbohydrates of late-lactation koala milk contained mainly lactose and some oligosaccharides, but little or none of the monosaccharide found in the milk of many other marsupials. Koalas share most of these features with the common brushtail possum (Trichosurus vulpecula) and common ringtail possum (Pseudocheirus peregrinus), the only two other marsupial arboreal folivores in which milk composition has been studied. This suggests that the koala'spattern of changes in milk composition may be common to marsupial arboreal folivores and may be associated with energetic limitations imposed directly by their folivorous diet or indirectly via selection for their long period of lactation and slow weaning. However, koalas' milk was more concentrated than that of the other two marsupial folivores, the importance of which, to the lactational strategy of the koala, can be resolved only by further study of milk production.

Optimal litter size: Does it cost more to raise a large litter in Caluromys philander?

Food intake of lactating Caluromys philander, a didelphid marsupial, was recorded from parturition until weaning of the pouch young. Variation in the average caloric value of daily food intake throughout lactation, in relation to litter size, showed no significant differences, but females increased food intake during late lactation, prior to weaning. Food intake was positively correlated with total litter mass at weaning. Moreover, there were significant differences in body mass and body length of offspring at first pouch exit (3 months) and at weaning (4 months): young born in small litters (1–3) were bigger than those born in large litters (6–7). Reproductive success is discussed on the assumption that pouch-young survival depends on food resources.

Development of mammalian endothermic metabolism: quantitative changes in tissue mitochondria

The development of energy metabolism of mammalian tissues was assessed in the tammar wallaby Macropus eugenii by the measurement of mitochondrial parameters in the liver, heart, kidney, and brain. Tissues taken from wallabies (n = 27) ranging from 10-day-old pouch young (weighing approximately 4 g) to adults (averaging 6.2 kg) were weighed and fixed, and mitochondrial volume and mitochondrial membrane surface area (MMSA) were determined by quantitative electron microscopy techniques. Developmental changes in these parameters were analyzed chronologically and allometrically. Relative growth rates of all four tissues decreased during development. Liver and heart showed constant allometric growth throughout development, whereas kidney and brain showed biphasic allometric growth. Tissue metabolic intensity assessed by MMSA (m2/cm3 tissue) was constant in liver, showed a threefold increase in brain during pouch life, showed a fourfold increase in the heart between 100 and 200 days of age, and showed a twofold increase in the kidney at the end of pouch life. In all tissues, adult levels of tissue metabolic capacity were present at pouch exit. In all four tissues, total MMSAs were at "reptilian" levels at birth and gradually increased to "mammalian" levels. Each tissue exhibited a different developmental timetable. When the total MMSAs for all four tissues were summed there was a similar pattern of allometric development between summed MMSA and whole animal metabolic rate.

Reproduction in Peradorcas-Concinna (Marsupialia, Macropodidae)

The length of the oestrous cycle in captive Peradorcas concinna was 33.73 � 1.65 days (n = 52). Females which were dominant over other females or were alone with their young had a cycle length of about 32 days and subordinate females had a cycle length of about 35 days. Some observations on the growth of the young are presented. Weaning is very abrupt; final pouch exit occurs about 2 weeks after the first pouch exit, and is caused by the female's aggressiveness towards its young.

Patterns of parental care and parental investment in marsupials.

Patterns of parental care and parental investment in marsupials.

Sweating in the kangaroo: a cooling mechanism during exercise, but not in the heat.

ARTICLESSweating in the kangaroo: a cooling mechanism during exercise, but not in the heatTJ Dawson, D Robertshaw, and CR TaylorTJ Dawson, D Robertshaw, and CR TaylorPublished Online:01 Aug 1974https://doi.org/10.1152/ajplegacy.1974.227.2.494MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByComparing walking and running in persistence huntingJournal of Human Evolution, Vol. 172Contributions from a Land Down Under: The Arid Continent23 September 2022Urohidrosis as an overlooked cooling mechanism in long-legged birds8 October 2021 | Scientific Reports, Vol. 11, No. 1Cats use hollow papillae to wick saliva into fur19 November 2018 | Proceedings of the National Academy of Sciences, Vol. 115, No. 49The anterior nasal region in the Red Kangaroo (Macropus rufus) suggests adaptation for thermoregulation and water conservation14 July 2017 | Journal of Zoology, Vol. 303, No. 4Thermal implications of interactions between insulation, solar reflectance, and fur structure in the summer coats of diverse species of kangaroo1 November 2016 | Journal of Comparative Physiology B, Vol. 187, No. 3Human Locomotion and Heat Loss: An Evolutionary Perspective23 December 2014Aridity, faunal adaptations and Australian Late Pleistocene extinctionsWorld Archaeology, Vol. 44, No. 1Brains, Brawn, and the Evolution of Human Endurance Running CapabilitiesDehydration, with and without heat, in kangaroos from mesic and arid habitats: different thermal responses including varying patterns in heterothermy in the field and laboratory29 June 2007 | Journal of Comparative Physiology B, Vol. 177, No. 7Ventilation patterns in red kangaroos (Macropus rufus Desmarest): juveniles work harder than adults at thermal extremes, but extract more oxygen per breath at thermoneutralityJournal of Experimental Biology, Vol. 210, No. 15Mechanisms for the control of respiratory evaporative heat loss in panting animalsDavid Robertshaw1 August 2006 | Journal of Applied Physiology, Vol. 101, No. 2Anticipatory regulation and avoidance of catastrophe during exercise-induced hyperthermiaComparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, Vol. 139, No. 4Hiperhidrosis primariaMedicina Clínica, Vol. 119, No. 17Thermoregulation in Juvenile Red Kangaroos ( Macropus rufus ) after Pouch Exit: Higher Metabolism and Evaporative Water RequirementsPhysiological and Biochemical Zoology, Vol. 74, No. 6Thermoregulation by Kangaroos from Mesic and Arid Habitats: Influence of Temperature on Routes of Heat Loss in Eastern Grey Kangaroos ( Macropus giganteus ) and Red Kangaroos ( Macropus rufus )Physiological and Biochemical Zoology, Vol. 73, No. 3Ventilatory Accommodation of Oxygen Demand and Respiratory Water Loss in Kangaroos from Mesic and Arid Environments, the Eastern Grey Kangaroo ( Macropus giganteus ) and the Red Kangaroo ( Macropus rufus )Physiological and Biochemical Zoology, Vol. 73, No. 3Energetics and biomechanics of locomotion by red kangaroos (Macropus rufus)Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology, Vol. 120, No. 1Thermogenic capabilities of the opossum Monodelphis domestica when warm and cold acclimated: Similarities between american and australian marsupialsComparative Biochemistry and Physiology Part A: Physiology, Vol. 89, No. 1Thermoregulatory responses during exercise and a hot water immersion and the affective responses to peripheral thermal stimuliInternational Journal of Biometeorology, Vol. 30, No. 1Sweat and heat exchange in man and otherJournal of Human Evolution, Vol. 14, No. 1Effect of ambient temperature on autonomic thermoregulation and activity patterns in the rufous rat-kangaroo (Aepyprymnus rufescens: Marsupialia)Journal of Comparative Physiology ? B, Vol. 153, No. 2Metabolic scope and conductance in response to cold of some dasyurid marsupials and Australian rodentsComparative Biochemistry and Physiology Part A: Physiology, Vol. 71, No. 1A Possible Contribution to Heat Transfer Through the Human Skin by the Eccrine (Atrichial) Sweat GlandEffects of Adrenergic Activators and Inhibitors on the Sweat GlandsNEUROENDOCRINE CONTROL OF SWEAT GLANDSJournal of Investigative Dermatology, Vol. 69, No. 1Electron microscopy of the sweat glands from the hairy skin of the beagleBritish Journal of Dermatology, Vol. 93, No. 3 More from this issue > Volume 227Issue 2August 1974Pages 494-498 Copyright & PermissionsCopyright © 1974 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1974.227.2.494PubMed4854555History Published online 1 August 1974 Published in print 1 August 1974 Metrics