Form Follows Function – Mammals
on Oct 30, 2023In a previous blog we touched base on the ‘Form follows Function’ principle exhibited in birds and discussed the reasoning behind the design of certain features. In this blog, I am going to elaborate on this topic through the use of examples from the mammal class. In doing so I hope to influence the way one observes living organisms as there is so much more than what meets the eye.
Mammals differ from other living organisms in that they possess mammary glands. These are the glands that produce milk for young to consume during the early stages of their life. Now, ever wondered why dogs and cats have many mammary glands running along the belly on each side, whilst those of antelope or deer are situated between the back legs and are fewer in amount? The answer can be found in the amount of young sired. Dogs and cats give birth to litters of multiple young, thus the placement of the mammary glands allows for easy access to milk for all young at once. Antelope or deer most often give birth to only one young at a time, they also possess rather flexible necks allowing them to reach in between mom’s belly and hind legs. The case with elephants, however, is very different. In elephants, a pair of mammary glands is situated between the front legs with nipples angled horizontally and outwards. This unusual placement of the mammary glands is the result of two influences, the first of which originated from the shape of the stomach. When comparing the side profile of hoofed mammals such as antelope and zebras to that of an elephant, one would notice that the belly of hoofed mammals extends backwards and upwards whereas the belly of an elephant extends backwards and downwards accompanied by big forward-facing hind knees. The shape of the belly in conjunction with the relatively immobile necks of elephants and the fact that they have to nurse using their mouths resulted in the mammary glands’ anterior placement.
The next couple of examples come from the Canidae (dog) and Felidae (cat) families. The first difference that often comes to mind is the ability to protract their claws – yes, protract not retract. When the foot of a cat is in a position of rest the claws are concealed and it takes physical action to project them outwards, making the claws protractible and not retractable. The ability to protract claws is due to a difference in the metatarsal foot bone structure, where those of felids allow for movement whilst those of canids don’t. The reason for this difference originates from when Felidae and Canidae first separated from their common ancestor, the Miacidae which were partly arboreal carnivores, similar to Civets, inhabiting forests of the northern hemisphere. Felids continued to use their sharp claws as weapons and climbing tools in an arboreal lifestyle, whilst Canids adopted a terrestrial life as the Earth became less humid and forests opened into grasslands. Their terrestrial lifestyle led to the development of long legs for running long distances and claws were better fit as gripping aids while running rather than as weapons. It is also due to the use of claws as weapons in felids that they have adapted the ability to protract their claws, keeping them safe.
The differentiation in lifestyle chosen by felids and canids is also represented in their dentition. Both families possess carnassial shears - specialised molars for the slicing of meat - along with incisors, canines, and premolars. In terms of the number of molars and premolars, felids have fewer teeth than canids, however, the reduction is a sacrifice for specialization. Their diet of mainly meat and very little bone allowed a mandible action to develop that is in line with the intersection between the carnassials for the most effective slicing abilities. Canids on the other hand have more and bulkier molars and premolars due to the change to a more generalist diet, including bones which also resulted in the carnassials being less significant but able to crush bone. In the Spotted Hyena, the molars and premolars have almost adapted completely to bone-crushing molars instead of meat-slicing shears.
Some other examples one might be lucky enough to see whilst staying at Sabi Sabi - the differences in between Black and White Rhino are fantastic illustrations of how form follows function. White rhinos are grazers feeding almost exclusively on short grass, with the whole head and neck extending downwards to ease grazing on grass. Their square-shaped lip is designed to crop short grasses in a relatively wide area allowing effective feeding. In contrast, Black rhinos are exclusively browsers, feeding on the foliage of trees. Their comparatively upwards-facing neck and head aids in reaching the foliage, but the prehensile triangular-shaped lip allows them to grab foliage and chop twigs effectively. White rhinos also inhabit considerably more open habitats compared to the Black rhino which sticks to dense thickets. Due to the nature of their habitat, Black rhinos developed a smaller stature allowing them to navigate the thickets more effectively. On the other hand, with no need to be small and due to the exposure to predators that comes along with living in open spaces the White rhino adapted a bigger and stronger body as a measure of protection.
The natural shape and volume of the eyelashes of giraffes as well as the length of elephant eyelashes often amaze guests, and sometimes evoke some envy under the ladies. These eyelashes are not only beautiful but vitally important to the protection of the animal’s eyes. The way in which both giraffe and elephant feed, puts their eyes in direct danger of injury by branches, thorns, insects etc. The almost unproportionate length paired with the rigidness of the eyelashes give an early warning to danger to the eye, thus adjustments to feeding position can be made.
The whiskers of predators work in a similar fashion as they also provide an early alert to objects in the immediate region of the face. These rigid sensory hairs are extremely sensitive to touch and have been developed as a navigational aid to maximise stealth. Stalking prey requires all the predator’s attention. It cannot afford to look around for obstacles or obstructions in their path, nor can it afford to make noise when moving through brush, especially when it gets within striking distance. The whiskers, when flared act as a measurement tool, allowing the predator to judge whether it will fit through a gap in the brush, thus reducing chances of making any noise and increasing chances of stalking prey successfully.
The safari experience is all about exposure to, immersion into and education on the vast expanse of unspoiled African wilderness. By just changing the way one looks at objects and organisms in our surroundings a whole different world is unlocked. This counts not only first-time safari-goers, but also veteran safari-goers, guides, and trackers. If it’s a life-long dream, a once-in-a-lifetime experience, it would only make sense to absorb all that there is to gain. Enjoy the big picture, but as Einstein said: “Look deep into nature, and then you will understand everything better.” It’s the intricacies that keep us as guides and trackers fascinated, and it is these same intricacies that allow us to immerse guests into the lives of those we share Sabi Sabi.
Blog by JP van Rooyen (Bush Lodge Ranger)
