The order Dasyuromorphia includes 23 genera and 71 species of carnivorous marsupials in three families: Dasyuridae (dasyurids), Myrmecobiidae (numbats), and Thylacinidae (thylacinids). Both Myrmecobiidae and Thylacinidae contain a single recent species, while Dasyuridae contains many species. The single species within Thylacinidae (Tasmanian wolf) is likely extinct. Dasyurids and thylacinids are more related to each other than they are to numbats.

Dasyuromorphs are nocturnal or crepuscular but occasionally forage or bask during the daytime. They exhibit long-range movements and often shift home ranges. Most species of dasyuromorphs are solitary and typically only form small groups while mating or rearing young. They build burrows and nests, which they add to during pregnancy and as young develop. Some species groom themselves, especially after feeding, which involves washing the face, snout, nape of the neck, throat and chin with licked forepaws. Dasyurids (Dasyuridae) use their forepaws not only to catch and eat prey but also in tactile social interactions where they grasp and pull one another.

To cope with unpredictably fluctuating food supplies, dasyuromorphs utilize a variety of strategies to conserve body heat and reduce energy expenditures. One strategy involves lowering metabolic rates when resources are particularly scarce. Because dasyuromorphs cannot sweat, they lick and pant to keep cool. Because of the diverse habitats in which they live, strategies to conserve body heat and reduce energy loss vary greatly. Strategies include having a spherical body shape to maximize heat conservation, increasing fur thickness in the winter, living in protected hollows during the day to avoid the heat, lining nests with leaves, and huddling in groups.

Reproduction

Both male and female dasyuromorphs practice promiscuous mating during a relatively short but intense breeding season. Larger males are more successful at attracting females and fighting off competing males. During courtship, males display antagonistic behavior in which they chase the female. During copulation, the male grips the female’s neck with his teeth and clasps her body with his forepaws to facilitate mounting. This continues throughout copulation, which lasts several hours. While copulating, males in the genus Antechinus can turn their bodies 180 degrees to ward off other males. After mating, males may guard a female for up to 12 hours to prevent other males from mating with her. Male Tasmanian devils are particularly aggressive during mate guarding and do not allow the female to leave her den for food or water for days. Occasionally females are able to escape these aggressive males but usually not without injury.

Females release pheromones to signal their receptivity to mate. They solicit males they find attractive and ward off other males. Females have long periods of behavioral estrous which allow them to mate with several males unless particularly aggressive males prohibit their ability to do so. Thus, multiple paternity as a result of sperm competition is often observed. For example, it is not uncommon for a litter of four Tasmanian devils to have four different fathers. Dasyurids (Dasyuridae) exhibit a unique form of sperm competition, and, other than bats, they are the only mammals in which females can store competing sperm within their reproductive tracts prior to ovulation.

asyuromorphs are either semelparous or iteroparous. Semelparity is very rare in mammals, having arisen only in dasyurids and didelphids. Semelparous dasyuromorphs, such as antechinuses, generally live in environments with predictable seasonal patterns of food abundance. It is thus advantageous to align reproductive patterns with seasonal variation in resource abundance. The mating season occurs in the winter when resources are scarce, and consequently young are born when resources are most abundant. Because seasonal patterns are so predictable, it not risky to dedicate all of their reproductive efforts into one brief mating season.

Males devote most of their energy to one big reproductive effort, and as a result have high concentrations of stress hormones in their blood. This inhibits inflammatory and immune responses and eventually kills the exhausted males. Females may survive for a second breeding season but almost never survive for a third. Semelparous dasyuromorphs are characterized by prolonged copulation, large testes size, male sexual dimorphism, mate guarding, long behavioral estrous of females, sperm storage in female reproductive tracts, high population densities, and sperm competition.

Iteroparous dasyuromorphs, on the other hand, reside in less restricted, less predictable environments. Therefore, it is risky to invest all of their energy into one reproductive effort when resource levels are so unpredictable. During the breeding season, Northern quolls exhibit normal levels of stress hormones and have larger body sizes and tail fat stores that help them survive to the next breeding season. Iteroparous dasyuromorphs do not display any of the identifying characteristics of semelparous dasyuromorphs. Additional reasons for semelparity in some species and iteroparity in others are not well understood.

After the brief mating season, male dasyuromorphs leave females with all parental responsibilities. In semelparous species, such as antechinuses, males die before their offspring are born.

Gestation time varies greatly with body size, as does time spent in the mother’s pouch. After leaving the pouch permanently, young are carried into well-hidden dens. Dens are lined with vegetation for protection and warmth and are located in underground burrows, caves or hollow logs. As young near weaning, mothers take more frequent trips outside of the den. When mothers begin to sleep away from their young, male offspring disperse from the den. Males move away from their mother’s home range while females remain in their mother’s home range for life.

During lactation, many dasyuromorph mothers are biased towards their male offspring and provide them with more nutrient-rich milk. Because larger males are more successful in attracting mates and reproducing, it is advantageous for mothers produce larger males that have a better chances of passing on her genes.

Lifespan/Longevity

The lifespan of dasyuromorphs varies greatly among the three families. Male numbats live up to 5 or 6 years in captivity, while females generally live longer. Little is known about Tasmanian wolves in the wild, and no information about their lifespan was recorded while they were still abundant. In captivity, however, they lived up to 12 years.

The lifespan of dasyurids is related to the amount of energy invested in early reproduction. Semelparous species, such as those in the genera Antechinus and Sminthopsis, invest heavily in one reproductive event and usually only live 1 to 2 years. Iteroparous species of dasyurids do not invest as much in early reproduction and live longer lives. For example, Tasmanian devils (iteroparous dasyurids) live an average of 8 years in the wild.

Although small dasyurids appear short lived, they actually have long lifespans compared to similarly sized eutherians. Whereas small dasyurids live 1 to 2 years, mice live only 4 to 6 months. The reasons behind these differences are still unknown but appear to be related to differences in metatherian and eutherian physiology.

Communication and Perception

Due to their nocturnal habits, dasyuromorphs have reduced their dependence on sight for communication and perception and have adapted olfactory and auditory mechanisms to compensate. Dasyuromorphs utilize chemical signals such as scent markers as a primary mode of communication. Commonly used chemical signals include urine dribble, cloacal drag, chin rub, and sternal rub. These are used to mark territory or as a status signal during breeding. Other social behaviors, such as mouth sniffing, naso-nasal sniffing, touching, and cloacal sniffing have been observed. Cloacal sniffing is especially important in male-female interactions.

Auditory communication is also common in dasyuromorphs. Vocalizations are mostly associated with defensive situations, such as nest defense, food defense, and threats but are also used in parent-offspring interactions as well as courtship and mating. Dasyuromorphs emit a chatter, tail rattle, foot tap, huff, or bark as an alarm mechanism when they feel threatened or in danger. Defensive vocalizations include hisses, huffs, grunts, growls and screams. When separated from their mother, young dasyuromorphs produce vocalizations that trigger mother retrieval behavior.

Dasyuromorphs also possess vibrissae that orient their attacks during predation. Males use tactile communication during mounting and copulation by grasping the neck and abdomen of the female.

Food Habits

Dasyuomorphs are generalized predators that eat a wide range of invertebrate and vertebrate prey. Numbats are insectivorous, and one individual can consume 10,000 to 20,000 termites each day. Other families within Dasyuromorphia are carnivorous. They catch and eat both terrestrial and arboreal insects, including moths, beetles, and mosquitoes. Large species are also known to eat juvenile mice.

Vision and olfaction play key roles in hunting. Most dasyuromorph species possess vibrissae that help orient their attack toward prey; however, visual and tactile methods are also employed. Carnivorous marsupials bite or pin their prey with their forepaws. Bites are directed toward the anterior part of the body (head or neck) in order to assure capture. They are also known to shake and toss prey if they show resistance.

Predation

Dasyuromorph are vulnerable to reptilian, avian, and mammalian predators. They do not have any physical adaptations to deter predators and thus tend to minimize predation by foraging at night and under protective covering. Small dasyuromorphs are particularly vulnerable to introduced European red foxes. Domestic dogs, dingos, and domestic cats also prey upon dasyuromorphs.

The order Peramelemorphia includes the bandicoots and bilbies, consists of 22 species that are divided among 7 genera and 2 families. They have a rodent-like appearance with short legs, a stocky body, a short neck, and a long, pointy nose. They are largely nocturnal, and possess a well-developed sense of smell and eyes that are well adapted for night vision. Most peramelemorphs have brownish-red or tan fur and are sometimes marked with stripes. Long, rabbit-like ears also characterize some species. They range in size from less than 100 g to over 5 kg, though most are about the size of a rabbit or smaller. Peramelemorphs are omnivores that eat mainly insects, but also consume a variety of vegetable material and some vertebrates as well. They occupy a wide range of habitats throughout Australia, New Guinea, Tasmania and the surrounding islands.

Peramelemorphs occupy a wide range of habitats, with altitude and climatic differences heavily influencing the distribution of species. Members of the family Peramelidae inhabit a variety of ecosystems, ranging from deserts to subalpine grasslands to tropical lowland rainforests, while thylacomyids primarily live in arid areas. Eastern barred bandicoots and the now extinct pig-footed bandicoot prefer grassland habitats, golden bandicoots inhabit the Top End and Kimberly tropics of Australia, brown bandicoots live in more secluded forests and the only living species of bilby, the greater bilby, is a desert-dweller. By occupying a wide variety of habitats and vegetation types, bandicoots and bilbies largely avoid competition. In New Guinea, peramelemorphs (Peroryctinae) are distributed throughout a wide range of altitudes. However, several species may occur sympatrically at moderate altitudes. The northern brown bandicoot, giant bandicoot and most species of spiny bandicoots prefer lowland areas, though some may live as high as 2000 m. Mouse bandicoots, striped bandicoots and Raffray’s bandicoots are upland species and typically live at elevations above 1000 m. There is one known high altitude species, Seram bandicoots, that are only found at altitudes of around 1800 m.

Physical Description

Members of the order Peramelemorphia are terrestrial, ground-dwelling mammals. They range from 15 cm in length (excluding tail) and 100 g in weight to 60 cm in length and 5 kg in weight. Their bodies are compact in size with relatively short tails compared to the length of their bodies, except in the case of the greater bilby, which possesses a long, brush-like tail. Peramelemorphs have short necks, elongate skulls, and long, tapered snouts. Their ears are upright and can range from being small and rounded to fairly large and pointy. Males are usually larger than females and are socially dominant.

The hind limbs of peramelemorphs are relatively long and exceptionally powerful. On the hind feet, the forth toe is the largest, while the bones of the second and third toes are fused, but still maintain separate claws (i.e., syndactyly). The front limbs are very short and well-adapted for ground foraging and digging. The first and fifth toes on the forefeet are either absent or lack claws if present. The second, third, and fourth toes have strong, flat claws for digging. They typically use their strong hind limbs to leap and hop through brushy habitats; however, when escaping danger they are able to run at a fast gallop. Their front and back legs work alternately. Characteristically, they land on hind and forefeet, and then take off with a push of their large hindfeet.

Members of the order Peramelemorphia can be most noticeably recognized by their unique marsupium, the pouch located on the venter used to carry immature young. Unlike teh marsupium of kangaroos and wallabies, the marsupium of peramelemorphs opens to the rear. Although this condition is present in some diprotodonts (e.g., wombats), it is probably uniquely derived in each lineage.

Peramelemorphs are omnivorous and their dentition is well-suited to a diet consisting of plants and insects. Unlike diprotodonts, which have only 2 lower incisors, peramelemorphs are polyprotodonts, having multiple lower incisors and anywhere from 4 to 5 upper incisors. Their incisors are flattened at the tips with the crown of the last lower incisor having two lobes. The canines are present and well-developed and they also have 3 premolars, which are narrow and pointed (plagialacoid) and 4 molars, which are tribosphenic or quadrate, in the upper and lower sets. This gives them the dental formula of 4-5/3, 1/1, 3/3, 4/4 = 46 or 48.

Reproduction

Direct observations of mating in peramelemorphs are rare, however, based on behavioral data they are probably either polygynous or promiscuous, and females are polyestrous. Although peramelemorphs are solitary, male territories overlap with those of several females, and during mating season males spend a majority of their time searching for receptive females. Once they find an estrus female, they follow the potential mate until she is ready to be mounted. Females may mate with more than one male if the opportunity presents itself.

Peramelemorphs are known for their accelerated breeding process, which enables a single female to give birth to as many as 16 young per year. Unlike all other marsupials, members of Peramelemorphia have a chorioallantoic placenta, which replaces the more typical yolk sac placenta a few days into gestation. Unlike the placenta found in ‘true mammals’, the placenta of peramelemorphs lacks villi, resulting in relatively shorter gestation when compared to ‘true mammals’, which developed the chorioallantoic placenta independently. Breeding can take place year-round for some genera, while others breed in the spring only. Day length, food availability, and weather conditions appear to have a significant impact on the timing of breeding in seasonal breeders. Year-round breeders occasionally show a decline in birthrate during times of food scarcity or drought. Gestation time is variable, from as little as 12.5 days in long-nosed bandicoots (among the shortest in any mammal) to about 14 days in several other species. Litters range in size from 2 to 5 offspring, but usually no more than 4 survive. Like other marsupials, young are altricial, weighing about 0.2 grams at birth. Immediately after birth, they crawl into their mother’s pouch and attach to a nipple. They leave the pouch after about 60 days, and are weaned in about 70 days. Females generally mate at about the time their previous litter leaves the pouch, so the weaning of one litter coincides with the birth of the next.

While the ranges of male and female peramelemorphs extensively overlap, females likely dictate distribution as they select and defend high-quality habitats for nesting and foraging. Many species have scent glands just posterior to the ears. Present in both genders, it is thought that these glands are used to mark territorial boundaries or during male-male competition for mates. While some species, such as northern brown bandicoots create terrestrial nests with an internal chamber, others, such as eastern barred bandicoots make several different kinds of nests, including subterranean chambers that are used during parturition.

The accelerated reproductive cycle of Peramelemorphia results in minimal parental care to young. The unique placenta of peramelemorphs lacks villi, which reduces direct contact between mother and fetus. However, the umbilical cord remains attached for a few hours afterbirth to serve as a safety rope while young leave the uterus and crawl into the rear-opening marsupium. Juveniles may continue to live in the mother’s nest for some time after leaving the pouch, but it is not known if they remain in their mother’s nest after weaning. There is no contact between mother and offspring after young leave the nest. Young peramelemorphs can reach reproductive maturity in as little as four months, however, only 11.5% of young survive to adulthood.

Bandicoots and bilbies live, on average, 1 to 2 years in the wild. While only 1 in 10 offspring usually survive, once they reach maturity life expectancy ranges from 2.5 to 3 years. In captivity, mean longevity for peramelemorphs is 2 to 4 years.

Behavior

All members of Peramelemorphia are solitary, coming together only to breed. Both males and females select territories, although male territories are larger and generally overlap with those of several different females. Most bandicoots are hostile toward one another, defending their territory with fighting, chasing, and scratching. Many species possess a scent gland just posterior to the ear, which is present in both genders in some species (e.g., northern brown bandicoot) and only present in males in others. These glands are used for marking territorial boundaries, and during male-male competition for mates or territory. Males are extremely territorial and during an encounter, they often mark the ground and surrounding plants with scents from the posterior ear gland. Males often warn each other with puffing sounds and may attempt to chase each other. Smaller males usually do not defend themselves against larger individuals when attacked. The only time peramelemorphs do not exhibit intraspecific aggression is when an estrus female encounters a male. All extant members of Peramelemorphia are nocturnal.

While bilbies are somewhat less aggressive than their close relatives, like the rest of Peramelemorphia, they are solitary and defend their territory when necessary. Bilbies are fossorial and are the only peramelemorphs to construct their own burrows; however, some species of bandicoot are known to burrow into the sand to escape hot weather. While most bandicoots live in burrows that are constructed from piles of vegetation covering small ground depressions, some species are known to occupy tree hollows or abandoned rabbit burrows. All extant peramelomorphs are nocturnal or crepuscular, although the recently-extinct pig-footed bandicoot was diurnal. While adapted for insect-eating, bandicoots and bilbies are often omnivorous, eating insects, grubs, plant material, and sometimes small vertebrates. Food is obtained by digging or rooting through plant litter on the ground.

Communication and Perception

Like other nocturnal mammals, peramelemorphs depend greatly on their senses of touch, smell, and hearing while hunting. Little is known about communication in Peramelemorphia. Many species possess a scent glands just posterior to the ears, which are present in both genders of some species (e.g., northern brown bandicoot) and only present in the males of others. These glands are used for marking territorial boundaries and during male-male competition for mates or territory. Males warn potential rivals with by making puffing sounds and exhibit aggression with open-mouthed fighting and chasing. Captive peramelemorphs have been observed to make “soft spitting noises” when threatened. A few species have calls, which can ranged from shrill alarm calls to low, huffing noises accompanied by barred teeth.

Food Habits

Peramelemorphs are omnivorous and eat a wide variety of invertebrates including ants, termites, insect larvae, earthworms, spiders and centipedes as well as plant matter such as bulbs, grasses and seeds. Some species supplement their diet with fungi, bird eggs and small vertebrates such as lizards and mice. Peramelemorphs forage by digging with their strong front claws and then using their long snout and tongue grab ahold of food items. While they can eat many different foods, each colony tends to show preference for one or two particular food types. This is most likely due to regional availability of each food type and helps reduce intraspecific competition for resources. Many members of the family Peramelidae are not obligate drinkers, as they acquire much of their hydration needs through their diet. Their front limbs are short and well-adapted for ground foraging and digging, and their dentition is ideally suited to a diet of plants and insects.

Predation

Peramelemorphs have few native predators. The only significant natural predators to bandicoots and bilbies are owls, quolls, and dingos. However, feral and domestic cats, dogs, foxes and other introduced animals have come to pose a considerable threat to the persistence of many local populations. In the past, bandicoots could often be found in Australian suburbs, however, domestic animals have significantly reduced their population. To protect themselves from predators, bandicoots and bilbies make nests in shallow holes in the ground, which they line with leaf litter. Leaf litter helps hide them from predators and protects them from inclement weather.

Marsupial moles specialized marsupial mammals that are found in the Australian interior.

The cone shaped head merges directly with the body, and there is no obvious neck region. The limbs are short and powerful, and digits III and IV of the manus have large spade-like claws. The dentition varies with individuals and, because the molars have a root of only one third of the length, it has been assumed that moles cannot deal with hard food substances. The dorsal surface of the rostrum and the back of the tail have no fur and the skin is heavily keratinized. There is no external evidence of the eyes, and the optic nerve is absent. It does, however, have a pigment layer where the eyes should be, probably a vestige of the retina. Both lachrymal glands and Jacobson’s organ are well developed, and it has been suggested that the former plays a role in lubricating the nasal passages and Jacobson’s organ.

The external ear openings are covered with fur and do not have pinnae. The nostrils are small vertical slits right below the shield-like rostrum. Although the brain has been regarded as very primitive and represents the “lowliest marsupial brain”, the olfactory bulbs and the tubercula olfactoria are very well developed. This seems to suggest that the olfactory sense plays an important role in the marsupial mole’s life, as it would be expected for a creature living in an environment lacking visual stimuli. The middle ear seems to be adapted for the reception of low-frequency sounds.

In an example of convergent evolution, the marsupial mole resembles the Namib Desert golden mole (Eremitalpa granti namibensis) and other specialised fossorial animals in having a low and unstable body temperature, ranging between 15–30 °C. It does not have an unusually low resting metabolic rate, and the metabolic rate of burrowing is 60 times higher than that of walking or running. Because it lives underground, where the temperature is considerably lower than at the surface, the marsupial mole does not seem to have any special adaptations to desert life. It is not known whether it drinks water or not, but due to the irregularity of rainfall it is assumed that it does not.

Surface behavior

It sometimes wanders above the surface where traces of several animals have been found. While most evidence indicates that it does this seldom and moves just a few meters before burrowing back underground, on some occasions multiple tracks were found suggesting that one or more animals have moved above ground for several hours. According to Aboriginal sources, marsupial moles may surface at any time of day, but seem to prefer to do so after rain and in the cooler season.

Captive animals have been observed to feed above ground and then return underground to sleep. Occasionally it has been recorded to suddenly “faint” on the surface without waking up for several hours until disturbed.

Above the ground it moves in a sinuous fashion, using its powerful forelimbs to haul the body over the surface and its hind limbs to push forward. The forelimbs are extended forward in unison with the opposite hind limb. Moles move about the surface with frantic haste but little speed.

Burrowing behavior

While burrowing, the southern marsupial mole does not make permanent tunnels, but the sand caves in and tunnels back-fill as the animal moves along. For this reason its burrowing style has been compared to “swimming through the sand””. The only way its tunnels can be identified is as a small oval shape of loose sand. Although it spends most of its active time 20-100 cm below the surface, tunneling horizontally or at shallow angles, it sometimes for no apparent reason turns suddenly and burrows vertically to depths of up to 2.5 meters.

Although most food sources are likely to occur at depths of approximately 50 cm from the surface, the temperature of these environments varies greatly from less than 15°C during winter to over 35°C during summer. While one of the captive moles was observed shivering when the temperature dropped under 16°C, it seems probable that moles can select the temperature of their environment by burrowing at different depths.

Diet

Little is known about the southern marsupial mole’s diet, and all information is based on the gut content of preserved animals and on observations made on captive specimens. All evidence seems to suggest that the mole is mainly insectivorous, preferring insect eggs, larvae and pupae to the adults. Based on observations made on captive animals, it seems that one of the favorite food choices was beetle larvae, especially Scarabaeidae. Because burrowing requires high energy expenditure it seems unlikely that the mole searches for its food in this prey impoverished environment, and suggests that it probably feeds within nests. It has been also recorded to eat adult insects, seeds and lizards. Below the desert sands of Australia, the marsupial mole searches for burrowing insects and small reptiles. Instead of building a tunnel, it “swims” through the ground, allowing the sand to collapse behind it.

Social behavior

There is little known about the social and reproductive behavior of these animals, but all evidence seems to suggest that it leads a solitary life. There are no traces of large burrows where more than one individual might meet and communicate. Although it is not known how the male locates the female, it is assumed that they do so using their highly developed olfactory sense.

The fact that the middle ear seems to be morphologically suited for capturing low frequency sounds, and that moles produce high pitched vocalizations when handled, indicates that this kind of sound that propagates more easily underground may be used as a form of communication.

The order Paucituberculata contains the seven surviving species of shrew opossum: small, shrew-like marsupials that are confined to the Andes mountains of South America. The order is thought to have diverged from the ancestral marsupial line very early. They were once included in the superorder but it is now known that Ameridelphia is paraphyletic, having given rise to Australidelphia, and thus could be considered an evolutionary grade. Genetic studies indicate that they are the second most basal order of marsupials, after the didelphimorphs. As recently as 20 million years ago, at least seven genera were in South America. Today, just three genera remain. They live in inaccessible forest and grassland regions of the High Andes.

Shrews were entirely absent from South America until the Great American Interchange three million years ago, and are currently present only in the northwestern part of the continent. Traditionally, it was thought that shrew opossums lost ground to these and other placental invaders that fill the same ecological niches. Evidence suggests, however, that both groups not only overlap, but do not seem to be in direct competition, and the marsupials’ larger size seems to imply that they prey on shrews and rodents. Several opossums, such as Monodelphis, also occupy small insectivore niches.

Shrew opossums (also known as rat opossums or caenolestids) are about the size of a small rat (9–14 cm long), with thin limbs, a long, pointed snout and a slender, hairy tail. They are largely carnivorous, being active hunters of insects, earthworms, and small vertebrates. They have small eyes and poor sight, and hunt in the early evening and at night, using their hearing and long, sensitive whiskers to locate prey. They seem to spend much of their lives in burrows and on surface runways. Like several other marsupials, they do not have a pouch, and it appears that females do not carry the young constantly, possibly leaving them in the burrow.

Largely because of their rugged, inaccessible habitat, they are very poorly known and have traditionally been considered rare. Several ecological factors, including density of forest, contribute to the part of the forests the shrew opossums occupy.

This is a genus of marsupial native only to south-western South America (Argentina and Chile). Microbiotheres are nocturnal and arboreal, and lives in thickets of South American mountain bamboo in the Valdivian temperate forests of the southern Andes, aided by its partially prehensile tail. They consume an omnivorous diet based on insects and fruit.

Monitos del monte live in the dense forests of highland Argentina and Chile, mainly in trees, where they construct spherical nests of water-resistant colihue leaves. These leaves are then lined with moss or grass, and placed in well-protected areas of the tree, such as underbrush, tree cavities, or fallen timber. The nests are sometimes covered with gray moss as a form of camouflage. These nests provide the monito del monte with some protection from cold, both when it is active and when it hibernates.

Sexual dimorphism

At the end of the summer, female monitos del monte tend to be larger and heavier than males. The tails of the sexes also vary in size during this time; females have a thicker tail, which is where they store fat; the difference suggests that females need more energy than males during hibernation. The sexual dimorphism is only seen during this time and not year-round.

Reproduction

Monitos del monte have a monogamous mating system. The females have well-formed, fur-lined pouch containing four teats. They normally reproduce in the spring once a year and can have a litter size varying from one to five. They can feed a maximum of four offspring, so if there are five young, one will not survive. When the young are mature enough to leave the pouch, approximately five months, they are nursed in a distinctive nest. They are then carried on the mother’s back. The young remain in association with the mother after weaning. Males and females both reach sexual maturity after two years.

Habits

The monito del monte is adapted to arboreal life; its tail and paws are prehensile. It is largely nocturnal and, depending on the ambient and internal temperature, and on the availability of food, it spends much of the day in a state of torpor. Such behavior enables it to survive periods of extreme weather and food shortage, conserving energy instead of foraging to no effect.

The animal covers its nest with moss for concealment, and for insulation and protection from bad weather.

Diet

The monito del monte depends on consuming both insects and fruit, with either component individually being nutritionally unbalanced. Fruit consumed comes from 16 species of plant, with the mistletoe species Tristerix corymbosus being a preferred source of fruit. A study performed in the temperate forests of southern Argentina showed a mutualistic seed dispersal relationship between D. gliroides and Tristerix corymbosus. The monito del monte is the sole dispersal agent for this plant, and without it the plant would likely become extinct. The monito del monte eats the fruit of T. corymbosus, and germination takes place in the gut.

Opossums are members of the marsupial order Didelphimorphia endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North America in the Great American Interchange following the connection of North and South America in the late Cenozoic.

As marsupials, female opossums have a reproductive system that includes a bifurcated vagina and a divided uterus; many have a pouch. The average estrous cycle of the Virginia opossum is about 28 days. Opossums do possess a placenta, but it is short-lived, simple in structure, and, unlike that of placental mammals, not fully functional. The young are therefore born at a very early stage, although the gestation period is similar to that of many other small marsupials, at only 12 to 14 days. They give birth to litters of up to 20 young. Once born, the offspring must find their way into the marsupium, if present, to hold on to and nurse from a teat. Baby opossums, like their Australian cousins, are called joeys. Female opossums often give birth to very large numbers of young, most of which fail to attach to a teat, although as many as 13 young can attach, and therefore survive, depending on species. The young are weaned between 70 and 125 days, when they detach from the teat and leave the pouch. The opossum lifespan is unusually short for a mammal of its size, usually only one to two years in the wild and as long as four or more years in captivity. Senescence is rapid. Opossums are moderately sexually dimorphic with males usually being larger, heavier, and having larger canines than females. The largest difference between the opossum and non-marsupial mammals is the bifurcated penis of the male and bifurcated vagina of the female. Opossum spermatozoa exhibit sperm-pairing, forming conjugate pairs in the epididymis. This may ensure that flagella movement can be accurately coordinated for maximal motility. Conjugate pairs dissociate into separate spermatozoa before fertilization.

Behavior

Opossums are usually solitary and nomadic, staying in one area as long as food and water are easily available. Some families will group together in ready-made burrows or even under houses. Though they will temporarily occupy abandoned burrows, they do not dig or put much effort into building their own. As nocturnal animals, they favor dark, secure areas. These areas may be below ground or above.

When threatened or harmed, they will “play possum”, mimicking the appearance and smell of a sick or dead animal. This physiological response is involuntary (like fainting), rather than a conscious act. In the case of baby opossums, however, the brain does not always react this way at the appropriate moment, and therefore they often fail to “play dead” when threatened. When an opossum is “playing possum”, the animal’s lips are drawn back, the teeth are bared, saliva foams around the mouth, the eyes close or half-close, and a foul-smelling fluid is secreted from the anal glands. The stiff, curled form can be prodded, turned over, and even carried away without reaction. The animal will typically regain consciousness after a period of a few minutes to four hours, a process that begins with a slight twitching of the ears.

Some species of opossums have prehensile tails, although dangling by the tail is more common among juveniles. An opossum may also use its tail as a brace and a fifth limb when climbing. The tail is occasionally used as a grip to carry bunches of leaves or bedding materials to the nest. A mother will sometimes carry her young upon her back, where they will cling tightly even when she is climbing or running.

Threatened opossums (especially males) will growl deeply, raising their pitch as the threat becomes more urgent. Males make a clicking “smack” noise out of the side of their mouths as they wander in search of a mate, and females will sometimes repeat the sound in return. When separated or distressed, baby opossums will make a sneezing noise to signal their mother. The mother in return makes a clicking sound and waits for the baby to find her. If threatened, the baby will open its mouth and quietly hiss until the threat is gone.

Diet

Opossums eat insects, rodents, birds, eggs, frogs, plants, fruits and grain. Some species may eat the skeletal remains of rodents and roadkill animals to fulfill their calcium requirements. In captivity, opossums will eat practically anything including dog and cat food, livestock fodder and discarded human food scraps and waste.

Many large opossums (Didelphini) are immune to the venom of rattlesnakes and pit vipers (Crotalinae) and regularly prey upon these snakes. This adaptation seems to be unique to the Didelphini, as their closest relative, the brown four-eyed opossum, is not immune to snake venom. Similar adaptations are seen in other small predatory mammals such as mongooses and hedgehogs.

Habitat

Opossums are found in North, Central, and South America. The Virginia opossum lives in regions as far north as Canada and as far south as Central America, while other types of opossums only inhabit countries south of the United States. The Virginia opossum can often be found in wooded areas, though its habitat may vary widely. Opossums are generally found in areas like forests, shrubland, mangrove swamps, rainforests and eucalyptus forests. Opossums have been found moving northward.

Monotremes are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. Although they are different from almost all mammals in that they lay eggs, like all mammals, the female monotremes nurse their young with milk.

Like other mammals, monotremes are endothermic with a high metabolic rate; have hair on their bodies; produce milk through mammary glands to feed their young; have a single bone in their lower jaw; and have three middle ear bones.

In common with marsupials, monotremes lack the connective structure (corpus callosum) which in placentals is the primary communication route between the right and left brain hemispheres. The anterior commissure does provide an alternate communication route between the two hemispheres, though, and in monotremes and marsupials it carries all the commissural fibers arising from the neocortex, whereas in placental mammals the anterior commissure carries only some of these fibers.

Extant monotremes lack teeth as adults. Fossil forms and modern platypus young have a “tribosphenic” form of molars (with the occlusal surface formed by three cusps arranged in a triangle), which is one of the hallmarks of extant mammals.

Monotreme jaws are constructed somewhat differently from those of other mammals, and the jaw opening muscle is different. As in all true mammals, the tiny bones that conduct sound to the inner ear are fully incorporated into the skull, rather than lying in the jaw as in non-mammalian cynodonts and other pre-mammalian synapsids; this feature, too, is now claimed to have evolved independently in monotremes and therians, although, as with the analogous evolution of the tribosphenic molar, this hypothesis is disputed.Nonetheless, findings on the extinct species Teinolophos confirm that suspended ear bones evolved independently among monotremes and therians. The external opening of the ear still lies at the base of the jaw.

The monotremes also have extra bones in the shoulder girdle, including an interclavicle and coracoid, which are not found in other mammals. Monotremes retain a reptile-like gait, with legs on the sides of, rather than underneath, their bodies. The monotreme leg bears a spur in the ankle region; the spur is not functional in echidnas, but contains a powerful venom in the male platypus. This venom is derived from β-defensins, proteins that are present in mammals that create holes in viral and bacterial pathogens. Some reptile venom is also composed of different types of β-defensins, another trait shared with reptiles. It is thought to be an ancient mammalian characteristic, as many non-monotreme archaic mammal groups also possess venomous spurs.

Platypus

In captivity, platypuses have survived to 30 years of age, and wild specimens have been recaptured when 24 years old. Mortality rates for adults in the wild appear to be low. Natural predators include snakes, water rats, goannas, hawks, owls, and eagles.

The platypus is an excellent swimmer and spends much of its time in the water foraging for food. It has a swimming style unique among mammals, propelling itself by alternate strokes of the front feet, while the webbed hind feet are held against the body and only used for steering, along with the tail. It can maintain its relatively low body temperature of about 32 °C  while foraging for hours in water below 5 °C. Dives normally last around 30 seconds, with an estimated aerobic limit of 40 seconds, with 10 to 20 seconds at the surface between dives.

The platypus rests in a short, straight burrow in the riverbank about 30 cm above water level, its oval entrance-hole often hidden under a tangle of roots. It may sleep up to 14 hours per day, after half a day of diving.

The platypus is a carnivore, feeding on annelid worms, insect larvae, freshwater shrimp, and yabby (crayfish) that it digs out of the riverbed with its snout or catches while swimming. It carries prey to the surface in cheek-pouches before eating it. It eats about 20% of its own weight each day, which requires it to spend an average of 12 hours daily looking for food.

The species has a single breeding season between June and October, with some local variation. Investigations have found both resident and transient platypuses, and suggest a polygynous mating system.[80] Females are believed to become sexually mature in their second year, with breeding observed in animals over nine years old. During copulation, the male grasps the female’s tail with his bill, wraps his tail around her, then grips her neck or shoulder, everts his penis through his cloaca, and inserts it into her urogenital sinus. He takes no part in nesting, living in his year-long resting burrow. After mating, the female constructs a deep, elaborate nesting burrow up to 20 m long. She tucks fallen leaves and reeds underneath her curled tail, dragging them to the burrow to soften the tunnel floor with folded wet leaves, and to line the nest at the end with bedding.

Young platypus are called “puggles”. Newly hatched platypuses are vulnerable, blind, and hairless, and are fed by the mother’s milk, that provides all the requirements for growth and development. After they hatch, the offspring are milk-fed for three to four months.

During incubation and weaning, the mother initially leaves the burrow only for short periods to forage. She leaves behind her a number of thin soil plugs along the length of the burrow, possibly to protect the young from predators; pushing past these on her return squeezes water from her fur and allows the burrow to remain dry. After about five weeks, the mother begins to spend more time away from her young, and at around four months, the young emerge from the burrow. A platypus is born with teeth, but these drop out at a very early age, leaving the horny plates it uses to grind food.

Echidna

Echidnas do not tolerate extreme temperatures; they shelter from harsh weather in caves and rock crevices. Echidnas are found in forests and woodlands, hiding under vegetation, roots or piles of debris. They sometimes use the burrows (both abandoned and in use) of animals such as rabbits and wombats. Individual echidnas have large, mutually overlapping territories.

The short-beaked echidna’s diet consists mostly of ants and termites, while the Zaglossus (long-beaked) species typically eat worms and insect larvae. The tongues of long-beaked echidnas have sharp, tiny spines that help them capture their prey. They have no teeth, so they break down their food by grinding it between the bottoms of their mouths and their tongues.

The female lays a single soft-shelled, leathery egg 22 days after mating, and deposits it directly into her pouch. An egg weighs 1.5 to 2 g and is about 1.4 cm long. While hatching, the baby echidna opens the leather shell with a reptile-like egg tooth. Hatching takes place after 10 days of gestation; the young echidna, called a puggle, born larval and fetus-like, then sucks milk from the pores of the two milk patches (monotremes have no teats) and remains in the pouch for 45 to 55 days, at which time it starts to develop spines. The mother digs a nursery burrow and deposits the young, returning every five days to suckle it until it is weaned at seven months. Puggles will stay within their mother’s den for up to a year before leaving.

Breeding season begins in late June and extends through September. During mating season, a female may be followed by a line or “train” of up to ten males, the youngest trailing last, and some males switching between lines.