Giraffes

The giraffe, Giraffa camelopardalis, is the tallest animal in the world.  Currently, it is classified as one species with nine subspecies, although taxonomists do not all agree on this.  A group is properly called a “tower” of giraffes unless they are observed in motion, in which case we refer to them as a “journey” of giraffes.  Giraffes have several interesting characteristics that we will explore.

Giraffes have a black prehensile tongue about 18″ long.   The upper lip, also prehensile, in combination with the tongue, is used for grasping, holding, and pulling whole branches through their mouths to strip off all of the leaves and thorns.  Their preferred food includes leaves, fruits, and flowers of woody species.  The thorny acacia tree is a special favorite.  Giraffes are ruminants, using strong stomach muscles to bring food back up to their mouths for chewing multiple times. For complete digestion, food makes its way through a giraffe’s four stomachs. 

Adult giraffes may reach heights of 14′ to 19′ and weigh from 1800 pounds to 2600 pounds.  Their necks, up to eight feet long, have the same number of vertebrae as other mammals.  As calves grow, cervical vertebrae grow longer.  The neck is very long, yet too short to reach the ground, so a giraffe must spread and bend its front legs in order to drink.  Giraffes do not need to drink more than once every few days, though, getting most of their water from their food.

A giraffe’s circulatory system includes several adaptations to accommodate its height.  The heart is one of the largest muscles in the body at two feet long and weighing 25 pounds.  It must generate almost twice the blood pressure of a human.  With a resting heartbeat of 150 beats per minute, it pumps sixteen gallons of blood each  minute.  To prevent fainting, a network of veins and muscles along with several one-way valves, regulate blood flow, keeping it from rushing to or away from the head when it is lowered or raised.  Giraffes have smaller red blood cells and many capillaries making oxygen absorption quicker to supply the energy needs of the muscles.

Giraffes sleep less than an hour each day, taking several short naps while standing.  They give birth while standing and calves can stand and walk within an hour of being born.  Their hooves, up to twelve inches in diameter, are made for comfortable walking and running.  Adults can sprint short distances at 40 miles per hour or sustain a loping speed for several miles at 20-30 miles per hour.  Their speed and size keeps adults safe from most predators, although calves are susceptible to lions, hyenas, leopards and wild dogs.  Their  normal life span is 25 years in the wild, but almost 50% of all calves are lost to predation before reaching adulthood.

Giraffes are listed as vulnerable on the IUCN Red List, with 90,000 individuals living in central and southern Africa, down from a population of 150,000 thirty years ago.  The main threats are habitat loss and killing for the bushmeat market.  As human populations expand, the need for firewood and livestock grazing areas results in shrinking forests and savannas.  Another factor negatively impacting populations is climate change, including a severe drought across much of the central plains in 2017.  Private game reserves and national parks offer protection, but they are limited in size and are being used by many species.  Giraffes are vital to keeping ecosystems in balance, eating browse unreachable by other species, opening new areas, and promoting growth of grasses and brush for food for many smaller species.