Click to watch two male Kangaroos "Boxing"

Other Facts
-Kangaroos cool themselves with "saliva baths" which is where they lick their whole body
-Kangaroos also pant to dissipate heat, very similar to dogs
-They will sweat but very rarely, and it will only happen when they are in locomotion
-Kangaroos are one of the only animals that use hopping as their main form of movement
-It takes lots of energy to start hopping, but after it begins they automatically bounce back up like a pogo stick
-The groups they live in are called "mobs"
-Can jump up to 10 ft. high, 25 ft. long, and can hop as fast as 35-40 mph for short bursts
-The reason kangaroos must hop is because their legs cannot move independently of each other

Reproductive System
-Females become reproductively mature at 18-24 months while males don't mature until 36 months
-Males fight to reproduce so they usually don't get to until they are 7-10 years old when they are large enough to compete
-The males fight be leaning back onto their tail and kicking their very strong legs at each other, this is known as "boxing"
-No breeding season, they mate year round
- A baby kangaroo, also known as a joey, is born out of the birth canal, and then climbs up her mothers fur into  her pouch
-The joey will stay in the pouch for about 8 months, drinking from teat inside the pouch
-Mothers can have multiple young at once, for example one could be in the pouch and another still developing in uterus
-Females also have two vaginas and two uteruses so they can have more children
-Because of this, females are in an almost permanent state of pregnancy, but have "embryonic diapause" meaning they can suspend development of next embryo until conditions are favorable

This is a picture of two male kangaroos "boxing"

Circulatory System
-Heart rate is very similar to humans, minimum heart rate of 40 bpm
-Heart rate increases 1.8 times faster than hopping frequency

This is a picture of a red kangaroo heart

Respiratory System
-Connected nose, mouth, and lungs
-Very similar breathing to humans
-Have a diaphragm that expands to bring air into lungs and then contrasts to push air out
-Breathing is related to hopping for the reason that air is pushed out when the kangaroo's feet leave the ground and then the lungs refill as the feet come forward for landing providing extra energy efficiency

Nervous System
-Microcirculation in the brain, network of small vessels to carry blood around the brain
-Has fasciculus aberrans to connect the left and right brain hemispheres compared to corpus callosum, which are found in most other mammals
-Has a spinal cord
-Nerves similar to those found in humans

This is a picture of a scan of a red kangaroo brain

Digestive System
-Herbivore, only eats plants and vegetation
-Digestive system is similar to that of sheep and North American deer
-Have teeth specialized for eating tough plants and grasses
-Front incisors cut food, while back molars grind the food into paste
-Teeth wear down, so they move forward and are shed from mouth
-Eventually left with only back molars
-Food is then carried down esophagus to the gut
-Gains 70% of energy ingested, efficient compared to other herbivores, but not compared to carnivores
-Any extra energy is stored in tissues throughout the body
-Can survive drinking water only twice a week because it utilizes all water found in the foliage it eats everyday