RED KANGAROO: CHARACTERISTICS, FEEDING, REPRODUCTION, BEHAVIOR - BIOLOGY - 2025

The red kangaroo (Macropus rufus) is a marsupial belonging to the Macropodidae family of the order Marsupialia. It is currently the largest marsupial in the world and the largest indigenous mammal in Australia.

The abundance of this species in its range is closely linked to environmental conditions, the influence of precipitation events, the dependence on population density and the availability of resources.

Red kangaroo (Macropus rufus)

Photo by David J. Stang / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

These animals are capable of moving over great distances following localized precipitation events, when resources are scarce. Because of this, the red kangaroo (Macropus rufus) is often considered a nomadic species compared to other species of the genus that are more sedentary.

Despite this, recent evidence shows that only a few populations of this species exhibit nomadic behavior. The population densities of these large marsupials tend to increase during the rainy season and decrease rapidly in the dry season.

General characteristics

Head

The head of the red kangaroos is small in relation to the size of the body. They have a pair of prominent ears that they keep erect and directed forward as a warning sign. The face is slightly elongated and has wide nostrils.

Size and weight

A fully grown male red kangaroo can be between 1.6m and 1.8m tall in an upright position, while females are smaller at 80cm to 1m.

Adult males reach a weight of 89 kg or even exceed 90 kg. The females are one third the size of the males, and can reach up to 36 kg.

Tail

The tail is quite long and can reach about 1.3 meters in length in males. This constitutes a third point of support when the kangaroo is in a state of rest and functions as a rudder when they are moving rapidly. The musculature of the tail is strong enough to support the weight of the kangaroo.

Extremities

The hind limbs are long and strong. The second and third toes of the hind legs are fused, adapting to jumping as a means of locomotion.

The forelimbs are short, with muscular forearms in males and they have claws that they use for grooming and fighting in courtship activities. The body of males is more robust than that of females in general features.

Females have a pouch or pouch that is absent in males and functions as a brood bag once a young is born.

Locomotion and posture

Red kangaroos like other macropod species move rapidly through hopping on their hind legs. Quadruped locomotion as seen in most mammals is not possible for them due to their adaptations for jumping.

This mechanism is a cheap form of locomotion, the energy consumption being relatively constant when moving at high speed due to the recycling of elastic energy in the tendons of the hind legs.

If there were no elastic energy recycling, the rate of energy consumption during travel would be almost twice as high. Kangaroos can travel at about 14 m / s, jump up to three meters high, and extend for 10 meters horizontally. Despite this, they generally travel at slower jump speeds.

When a kangaroo is in a resting state it generally perches on its hind legs almost fully erect, using its long tail as a third point of support as a tripod. When they are foraging they can use their forelimbs as a foothold while moving their hindlimbs at the same time.

Coloration

Males usually have a reddish-brown coloration in the dorsal region and a cream to grayish coloration in the ventral region. Because of this, they are called red kangaroos. The females on the other hand, have a grayish coloration and less conspicuous than that of the males, very similar to that of the young and juveniles.

In the more arid regions of its range, females may have a more reddish coloration.

Populations

It is one of the most abundant species of kangaroos in Australia. They form small groups compared to other species of kangaroos that consist of approximately a dozen individuals maximum. Despite forming groups, they show few attributes of sociability present in most gregarious mammals.

Each group consists of at least one dominant male with several females with whom he exclusively mates. Group size is determined by little-studied random processes.

Individuals leave and enter the group constantly so it is always constantly changing. In addition to this, no close relationships are established within the group, the only strong relationships being those between the females and their young.

When the dominant male is challenged by a male from outside the group for the right to mate, a confrontation usually occurs between the two males.

Taxonomy

Animalia Kingdom

Phylum: Chordata

Subfilum: Vertebrata

Class: Mammalia

Subclass: Theria

Infraclass: Marsupialia

Order: Diprodontia

Family: Macropodidae

Genus: Macropus

Species: Macropus rufus

Feeding

These large marsupials are specialist herbivores with a dietary preference for younger, softer green plants with higher nutritional content.

They generally consume large amounts of fragments of these plants. Digestion occurs through microbial fermentation in the anterior stomach.

Male red kangaroo in feeding activities

Ltshears / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

During the dry season, due to insufficient resources to sustain a high kangaroo population, the mortality rate increases due to inadequate nutrition. The most affected individuals are juveniles, because the quality of the grass is low, and the larger males, because the vegetation is not enough to cover their energy requirements.

Both lactating females and males who are involved in courtship and mating activities are the most affected by the lack of quality food. These groups of kangaroos also choose the vegetation that has the highest nutritional quality.

Some diet analyzes point to the Enneapogon avenaceus plant along with other grasses as one of the most important in the diet of red kangaroos. Pastures occupy between 67 and 95% of the diet, depending on their availability in the grazing area.

Reproduction

Courtship activities (Macropus rufus)

Rufus46 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Red kangaroos reproduce throughout the year continuously and asynchronously if the conditions in which they are found are favorable.

This occurs as an adaptation to unpredictable and erratic rainfall that produces extremes in the quantity and quality of vegetation consumed by kangaroos. Females mature between 15 and 20 months of age, while males mature around 2 years.

Male red kangaroo maintain a polygynous mating system, that is, they maintain a group of females with whom they mate when conditions are right. Once the rainy season begins and the females regain their body condition to a certain threshold, they begin to go into heat quickly.

Like a large part of macropodoid marsupials, heat and mating after parturition constitute a normal pattern in the reproductive events of the species. In this video you can see the mating between two specimens:

Embryonic diapause

In the red kangaroo, successive calves result from postpartum estrus followed by embryonic diapause and reactivation of the embryo in mid-lactation when the previous calf permanently emerges from the pouch.

Usually the second embryo stops at the blastocyst stage and continues its development when conditions are ideal.

This phenomenon is known as facultative embryonic diapause, which allows fertilization to be uncoupled from birth, ensuring that postnatal development occurs under the most favorable conditions for the survival of the offspring.

The second embryo that is formed after the birth of a baby, resumes its development once the first baby is independent of the mother.

Phases of lactation in the red kangaroo

Lactation in these kangaroos has been subdivided into several phases:

-Phase 1

It constitutes a preparatory phase during gestation before milk is produced.

-Phase 2

It is equivalent to lactation in eutherian mammals and comprises two stages, an early initial phase (phase 2a) when the offspring is permanently attached to the teat and a second phase (phase 2b) in which the offspring begins a stage of physiological maturation ranging from 70 to 200 days.

-Phase 3

It begins when the individual is fully developed and begins with the intake of foods other than breast milk. At this point the milk produced by the mother is rich in lipids (200 to 235 days of calf age).

Female red kangaroo suckling her calf

Rufus46 / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Similarly, in the transition from phase 2 to phase 3, the development of embryonic diapause pregnancy is reactivated. Once the new calf is born, the female maintains a calf outside the bag until it is definitively weaned, a calf in the bag and also a calf that enters the diapause state.

The female produces milk for the offspring in phase 3 from one mammary gland and milk for phase 2b from the second mammary gland for the offspring found in the pouch. This very particular phenomenon is known as asynchronous simultaneous lactation or dual lactation.

Behavior

Young male red kangaroos are the most mobile age and sex class. The dispersal distances of the original group often vary depending on environmental conditions, particularly the pressure exerted by drought.

Because red kangaroos inhabit open areas with little shelter availability, they tend to aggregate as a strategy to avoid, locate and reduce the risk of predation. In this way the red kangaroos treat their congeners at a distance of 50 meters as part of the group, investing time in surveillance and foraging.

Despite this type of behavior, the aggregation or formation of large groups has the consequence of accentuating intraspecific competition for resources. The competition occurs despite the fact that the groups formed by red kangaroos are smaller than those of other species such as eastern and western gray kangaroos.

Mating

Olfactory stimuli are an essential part in the detection of the reproductive status of females by males. They generally inspect the female's urogenital opening and frequently sniff her urine to determine her sexual status.

Once the male detects a receptive female he follows her for about 2 hours before mating and stops to groom and lick her limbs. In addition to this, the male holds the female's tail with her forelimbs.

During courtship the males make a series of clicking noises with their mouths and the female may make a shrill sound if cornered.

Once the female accesses the mating, she bends down placing her front legs on the ground and the male positions himself by holding the female by the neck with his strong forearms and placing his legs one on each side of the female's tail to initiate copulation. which has duration intervals of up to 20 minutes.

Fighting activities between males

When confrontations occur between males, they generally assume an upright position with the hind limbs stretched and rigid and using the tail as a point of support.

The forearms open and close continuously for display. When the displays are more aggressive, the males violently shake their heads and legs.

If the conflict persists, the males conflict by holding each other with their strong forearms and using their legs to kick hard at the opposing male's abdominal area while holding onto the tail.

They can also struggle and hit each other with their arms and even bite. After defining a winner the losing male retires.

This aggressive behavior against rival males can also be used to defend against some predators such as dingoes. On the other hand, males can assume these aggressive postures with man and even with pets such as dogs when they are perceived as a threat.

Daily activity

During the hottest hours, red kangaroos are often seen in the shade preening and licking their forearms to lose heat. Because they inhabit arid areas, their activity pattern is limited to the early hours of the morning and during twilight and night when the temperature conditions are less harsh.

Red kangaroo

calf with its mother Sb616 / Public domain

During this time the red kangaroos carry out their foraging activities in all the plant formations. In addition, they spend time searching for water, although they generally extract it from the plants they consume. These animals need less amounts of water compared to other species that inhabit areas with higher rainfall.

At night they can cover uncovered areas of tall shrubs where they are generally not seen during the day.

Habitat and distribution

The red kangaroo is an endemic species to Australia. It occurs in much of the Australian territory, concentrating its populations mainly in arid and semi-arid areas whose precipitation is maintained between 250 and 500 mm per year.

They can occupy areas with trees and scattered shrub vegetation, prairie areas, savannas and even intervened environments.

Distribution of the red kangaroo in Australia

IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Within a population of red kangaroos, there is usually a differential distribution of individuals according to the availability of resources and the reproductive or developmental status. Adult males and lactating females occupy the areas with the best resources.

The natural systems they occupy are dominated by trees such as the thorny wattle (Acacia victoriae). The shrub layer is characterized by perennial plants resistant to long periods of drought and several that evade drought (Atriplex vesicaria and various species of the genus Sclerolaena).

At ground level, the vegetation consists of a mixture of perennial and ephemeral forbes (Helipterum and Helichrysum spp.), Herbs (Astrebla, Enneapogon, Eragrostis and Chloris spp.) And copper strawberries (Sclerolaena spp.)

State of conservation

Currently it is a species that is subject to commercial exploitation for the use of its meat and the manufacture of its skins. Despite this, the species maintains a stable population trend and is classified according to the IUCN in the category of least concern.

Competition with livestock such as sheep in arid and semi-arid areas does not appear to have a negative effect. These interactions tend to increase in the dry season, when the kangaroos displace the sheep, which is why they are often eliminated by farmers as pests.

Their populations are often controlled because high population sizes often cause degradation of the environment due to overexploitation of resources.

These kangaroos have greatly benefited from the infrastructure for raising sheep and other animals, using artificial sources of water and the pastures developed for breeding animals.

Predators

Red kangaroos tend to be more abundant outside the range of dingoes, canids introduced in Australia. Dingoes are usually very effective hunters of red kangaroos, especially those animals that are young, old or those that are injured.

In some parts of Australia, the rate of killing of red kangaroos by dingoes, as well as the selection of juvenile specimens, suggests that dingo activity appears to play a regulatory role in the abundance of natural populations.

References

1. Blumstein, DT, & Daniel, JC (2003). Red kangaroos (Macropus rufus) receive an antipredator benefit from aggregation. Acta Ethologica, 5 (2), 95-99.
2. Caughley, G. (1964). Social organization and daily activity of the red kangaroo and the gray kangaroo. Journal of Mammalogy, 45 (3), 429-436.
3. Croft, DB (1991). Home range of the red kangaroo Macropus rufus. Journal of Arid Environments, 20 (1), 83-98.
4. Dawson, TJ, & Ellis, BA (1996). Diets of mammalian herbivores in Australian arid, hilly shrublands: seasonal effects on overlap between euros (hill kangaroos), sheep and feral goats, and on dietary niche breadths and electivities. Journal of Arid Environments, 34 (4), 491-506.
5. Edwards, GP, Croft, DB, & Dawson, TJ (1996). Competition between red kangaroos (Macropus rufu s) and sheep (Ovis aries) in the arid rangelands of Australia. Australian Journal of Ecology, 21 (2), 165-172.
6. Ellis, M., van Weenen, J., Copley, P., Dickman, C., Mawson, P. & Woinarski, J. 2016. Macropus rufus. The IUCN Red List of Threatened Species 2016: e.T40567A21953534. https://dx.doi.org/10.2305/IUCN.UK.2016-2.RLTS.T40567A21953534.en. Downloaded on 25 February 2020.
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9. Moss, GL, & Croft, DB (1999). Body condition of the red kangaroo (Macropus rufus) in arid Australia: the effect of environmental condition, sex and reproduction. Australian Journal of Ecology, 24 (2), 97-109.
10. Muths, E., & Hinds, LA (1996). Circulating levels of prolactin and progesterone in a wild population of red kangaroos (Macropus rufus) Marsupialia: Macropodidae. General and comparative endocrinology, 101 (3), 317-322.
11. Sharman, GB, & Calaby, JH (1964). Reproductive behavior in the red kangaroo, Megaleia rufa, in captivity. CSIRO Wildlife Research, 9 (1), 58-85.
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13. Smith, MJ (1996). Duration of embryonic diapause in the brush-tailed bettong, Bettongia penicillata (Potoroidae): effect of age of quiescent corpus luteum. Reproduction, Fertility and Development, 8 (4), 807-810.