CHARACTERISTICS OF
MAMMALS
Die V oelbekdier (P latypus) is behaard, leef in riviere van Tasmanie en A u stra lii, is ongeveer 2 voet lank, sw em m et gewebde pote, besit aan die agterpote van m annetjies skerp spore wat m et gifkliere verbind is en leef hoofsaaklik van m os- sels en klein waterdiertjies. Die wyfie le haar twee eiers in 'n gat in 'n rivierwal.
Die mieregel (Echidna) is ’n landdier, het n huidbedekking van hare en stekels, 'n punlige snuit, sterk kloue en le e f van miere wat m et die pote oopgegrawe en m et behulp van die lang snuit en tong gevang word. D ie w yfie le slegs een eier wat in ’n buidelsak uitgebroei word.
T he group of m am m als ranges from the pigmy shrew w ith a mass of 2,5g to the blue whale with a mass of 128 m etric ton. M am mals m ay be terrestrial, aquatic (porpoises) or aerial (bats). M an is also a m am m al and is dependent (directly or indirectly) on m am mals for his food, clothing and many other services from chem icals to com panionship. It is therefore of interest to know w hat a m am m al is.
It is im portant to use all the characterstics listed below and not just one when deter mining w hether an anim al is a m am m al or not. F o r exam ple, it would be quite wrong to say that the duck-billed platypus (which is a m am m al) is a bird just because it lays eggs and has a duck-like bill. F o r apart from these peculiarities it possesses all other qualities o f a mam m al.
1. M am m als are the verteberate anim als which produce milk to feed their young. All m am m als suckle their young by m eans of m am m ary (milk) glands, the ducts of these are united to open on nippels. T he exception being the M o- notrem es viz. the duck-billed platypus and spiny ant-eater w hich produce m ilk from specialized sw eat glands. T he ducts o f these are united to open on nipples. T he milk seeps fro m pore-like holes on the abdom en and is lapped up by the young.
2. All mam m als have hair. T he degree of coverage varies e.g. in som e whales, hair is nearly absent in the adult, except for a few about the m outh; in other it is lacking entirely in the adult, although it m ay have appeared briefly at some stage of prenatal developm ent. F u rth erm o re hair can be of variable thickness and length. F o r exam ple the “ w hiskers” of a cat are vibrissae which arise from follicles which contain erec tile tissue; while body hairs arise from follicles w ithout erectile tissue. Exam ples of the latter are the spines of a porcupine, the bristles of a horse’s m ane, awns of a m an’s beard, wool of a sheep, fur of a chinchilla, and the velli of an em bryo or newly born mam m al.
3. M am m als have sweat glands. E xcep tions are the w hale and pangolin. Sweat glands are distributed in varying density e.g. the N egroids in the tropics have m ore sweat glands th an the Caucasoid hum ans. In cats and mice the sweat glands are situated under the soles of the feet, in the bats they are on the side of the head, in deer at the base o f the tail etc. Coloured sweat occurs in some mam m als, e.g. hippos and kangaroos have a reddish sweat, w hile vervet m o n keys’ sweat is blueish.
4. T he young of m am m als are born alive. T he M onotrem es however, are egg-lay ing mammals. T he spiny ant-eater trans fers its eggs to a m arsupial-like pouch, these eggs develop at the breeding sea
son. T he platypus m akes a nest in a burrow fo r her two o r three eggs and rem ains w ith them continuously until after hatching.
5. T he m ature red blood corpuscles of m am m als do not have a nucleus and are round. However, in camels and llamas the corpuscles are oval.
6. M am m als have a m uscular diaphragm which separates the chest cavity from the abdom inal cavity. T his diaphragm is im portant fo r respiration. Birds also
have a diaphragm but this is not m us cular.
7. T he cerebral hem ispheres of a m am m al’s brain are highly developed in com parison to other vertebrates. 8. In mam m als each half of the lower jaw
consists of a single bone called the den- tary.
9. T he jaw articulation of a m am m al is between the squam osal and the dentary. 10. M am m als have three ossicles (bones) in the middle ear viz. ham m er, anvil and the stirrup.
Die geelvrugtevlerm uis is een van die soogdiere wat kan vlieg. D it het ’n vlerkspan van
70 cm. en verkies ’n meer gem atigde klim aat as dig van die Vrystaat. Sporadies w ord
enkeles wel hier aangetref en verwek dan groot opspraak aangesien hulle vir vampiere, dit wil se bloedsuiers aangesien word. Vam piere kom egter slegs in Suid-A m erika voor en nie op die Afrikaanse Vasteland nie.
