This species is a very large kangaroo with long, pointed ears and a squared-off muzzle. Males have short, red-brown fur, fading to pale buff below and on the limbs. Females are smaller than males and are blue-grey with a brown tinge, pale gray below, although arid zone females are colored more like males. It has two forelimbs with small claws, two muscular hind-limbs, which are used for jumping, and a strong tail which is often used to create a tripod when standing upright. The red kangaroo’s legs work much like a rubber band, with the Achilles tendon stretching as the animal comes down, then releasing its energy to propel the animal up and forward, enabling the characteristic bouncing locomotion. The males can cover 8–9 m (26.2–29.5 ft) in one leap while reaching heights of 1.8–3 m (5.9–9.8 ft), though the average is 1.2–1.9 m (3.9–6.2 ft)
Males grow up to a head-and-body length of 1.3–1.6 m (4.3–5.2 ft) with a tail that adds a further 1–1.2 m (3.3–3.9 ft) to the total length. Females are considerably smaller, with a head-and-body length of 85–105 cm (33–41 in) and tail length of 65–85 cm (26–33 in). Females can weigh from 18 to 40 kg (40 to 88 lb), while males typically weigh around twice as much at 55 to 90 kg (121 to 198 lb). The average red kangaroo stands approximately 1.5 m (4.9 ft) tall to the top of the head in upright posture. Large mature males can stand more than 1.8 m (5.9 ft) tall, with the largest confirmed one having been around 2.1 m (6.9 ft) tall and weighed 91 kg (201 lb).
The red kangaroo maintains its internal temperature at a point of homeostasis about 36 °C (97 °F) using a variety of physical, physiological, and behavioral adaptations. These include having an insulating layer of fur, being less active and staying in the shade when temperatures are high, panting, sweating, and licking its forelimbs.
The red kangaroo’s range of vision is approximately 300° (324° with about 25° overlap), due to the position of its eyes.
Red kangaroos live in groups of 2–4 members. The most common groups are females and their young. Larger groups can be found in densely populated areas and females are usually with a male. Membership of these groups is very flexible, and males (boomers) are not territorial, fighting only over females (flyers) that come into heat. Males develop proportionately much larger shoulders and arms than females. Most agonistic interactions occur between young males, which engage in ritualised fighting known as boxing. They usually stand up on their hind limbs and attempt to push their opponent off balance by jabbing him or locking forearms. If the fight escalates, they will begin to kick each other. Using their tail to support their weight, they deliver kicks with their powerful hind legs. Compared to other kangaroo species, fights between red kangaroo males tend to involve more wrestling. Fights establish dominance relationships among males, and determine who gets access to estrous females.]Alpha males make agonistic behaviours and more sexual behaviours until they are overthrown. Displaced males live alone and avoid close contact with others.
The red kangaroo breeds all year round. The females have the unusual ability to delay birth of their baby until their previous Joey has left the pouch. This is called embryonic diapause. Copulation may last 25 minutes. The red kangaroo has the typical reproductive system of a kangaroo. The neonate emerges after only 33 days. Usually only one young is born at a time. It is blind, hairless, and only a few centimetres long. Its hind legs are mere stumps; it instead uses its more developed forelegs to climb its way through the thick fur on its mother’s abdomen into the pouch, which takes about three to five minutes. Once in the pouch, it fastens onto one of the two teats and starts to feed. Almost immediately, the mother’s sexual cycle starts again. Another egg descends into the uterus and she becomes sexually receptive. Then, if she mates and a second egg is fertilised, its development is temporarily halted. Meanwhile, the neonate in the pouch grows rapidly. After approximately 190 days, the baby (called a joey) is sufficiently large and developed to make its full emergence out of the pouch, after sticking its head out for a few weeks until it eventually feels safe enough to fully emerge. From then on, it spends increasing time in the outside world and eventually, after around 235 days, it leaves the pouch for the last time. While the young joey will permanently leave the pouch at around 235 days old, it will continue to suckle until it reaches about 12 months of age. A doe may first reproduce as early as 18 months of age and as late as five years during drought, but normally she is two and a half years old before she begins to breed.
The female kangaroo is usually permanently pregnant, except on the day she gives birth; however, she has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch. This is known as diapause, and will occur in times of drought and in areas with poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, red kangaroo mothers may “have up to three generations of offspring simultaneously; a young-at-foot suckling from an elongated teat, a young in the pouch attached to a second teat and a blastula in arrested development in the uterus”.
The kangaroo has also been observed to engage in alloparental care, a behavior in which a female may adopt another female’s joey. This is a common parenting behavior seen in many other animal species like wolves, elephants and fathead minnows
by simon schofield