On The Subject Of Species & Sub-Species

Ron Thomson

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The Wildlife Game - On The Subject Of Species & Sub-Species

It always amazes me that so many people who state they are nature-lovers, naturalists, hunters and/or “conservationists”, et cetera, appear to have so much difficulty in understanding the differences that exist between what we call “races”, or “subspecies”, and the parent species that spawned them.

This has created particular problems of understanding amongst hunters because, in recent years, certain subspecies of Africa’s wild animals have been allocated separate trophy status in the hunting record books. To understand this phenomenon, however, and to understand why the separate trophy listings are valid, we must perforce delve into some of the realities of biological and ecological science.

A SPECIES (of plant or animal) is the basic taxonomic unit in biological nomenclature. Taxonomy is the practice of assigning scientific names to organisms (living “things” - comprising plants and animals), and of classifying them into ordered groups on the basis of their relationships. Individual organisms in “a species” exhibit permanent common characteristics, and they produce fertile young with the same characteristics.

Similar species, generally, maintain their identities because they are geographically separated. Similar species that share a common environment, however, remain divorced because they have developed physiognomic and/or behavioural differences – which are especially pertinent when associated with each species’ respective breeding cycle. Sometimes relatively minor adaptations by two similar species, relative to the way they occupy and/or use their habitat, or a slight difference in their morphology (that is, in their body structure, size or colour etc.) is enough to maintain distinctions between them. In one way or another, therefore, nature has devised mechanisms that normally prevent successful crossbreeding between species - but when crossbreeding does occur infertile ‘mules’ are, normally, the result.

To properly understand the SUBSPECIES phenomenon one has to understand, also, that a species is comprised of many, many distinct and quite separate populations across the length and breadth of its distribution. A population, in the ecological context, is a discrete group of animals, of the same species, that interacts within the confines of its own group ONLY. This means that breeding – and the transfer of genes from one individual to another at the time of conception – normally occurs ONLY between individuals of the same population group. Thus each population develops its own very specific gene pool.

The more popular usage of the term ‘population’ denotes a collective number of a particular species of animal, hence: “India’s tiger population numbers 4000 animals”. This is not correct in biological terms so the word ‘population’ is NOT used in this article in this context.

Populations of animals live in pockets of the kind of habitat to which their species is adapted – or in regions where this habitat extends over a large area. Obviously the size and extent of the habitat determines the size and the range of each population. The habitat in which a population lives – irrespective of its smallness or great size – provides the individuals comprising that population with all their day-to-day living requirements. They, therefore, have no reason to leave their habitats to seek their living needs elsewhere.

In most cases, individual adults (males and females) comprising an animal population each settle into a specific small section of the habitat in which the population as a whole lives – and they get to know that small section intimately. This provides the animals with many survival advantages. These sections are called “home ranges” – and the adult individuals that live within established home ranges rarely move out of them throughout their entire lives. Most wild animals, therefore, are highly sedentary. They also – as adults – never visit those parts of the rest of the habitat in which the other individuals of their population live. The resources of a home range – water, food and shelter – are shared by several individuals because home ranges, to a great extent, overlap. The occupation of a home range, therefore, is not contested.

“Territories”, on the other hand, are those parts of an individual’s home range that are used for breeding. They are normally occupied by males – but not always; and/or not always just by males. Territories never overlap – and they are defended against other individuals of the same species that pose a challenge to the owner’s occupancy.

There is a very big difference, therefore, between a “home range” and a “territory”.

Animals comprising a population breed, producing young on a regular basis. The young stay with their mother’s throughout their juvenile and adolescent lives. When they reach puberty they leave their maternal home range and they ‘surf’ the entire habitat seeking a home range of their own – sometimes finding one to their liking at the other side of the habitat. This is how the genes from one side of the population reach, and mix with, the genes on the other side of the population.

Sooner or later all the available home ranges and all the available territories in the population’s habitat become occupied. The habitat is then said to be “saturated”.

Although the occupancy of a home range is not seemingly contested, each species has a “comfort zone” factor that is operative all the time. This is based upon the intrinsic need for each animal to have its own minimum “individual space”. This is the factor that determines just how large or how small a home range will be – and it is often very variable. It is also the factor which generates unseen “pressures” - exuded from older, settled animals onto those insecure younger animals that are seeking home ranges of their own - inducing them to “move on”.

The size of an individual’s home range - AND its individual-space-demands – are influenced very greatly by the nature of the habitat. Thus populations living in optimum habitat consistently occur in much denser numbers than do other populations that live is less-suitable habitats.

The most important life-objective of newly independent sub-adult animals is to find a home range of their own – which they, at first, seek within their parental population’s habitat.

When populations are low in number – compared to the sustainable carrying capacity of the habitat – vacant home ranges are readily available. This means few sub-adult animals are lost to the population which thus, each year, gains ever-greater numerical strength. When the habitat is saturated, however, vacant home ranges occur normally ONLY when an older animal dies. In this case only the strongest of the sub-adults find a home range. This strengthens the population’s gene pool. All the other sub-adults are then “pressurised” to leave the population – and they roam the wilderness, in deficient habitats, most of them eventually succumbing to starvation or to some strange predator against which they have no natural defenses.

Some individuals, however, WILL find a suitable habitat elsewhere and, if it is vacant, they will become the spearhead of a new population group. If the habitat is NOT vacant, but NOT saturated, they will find a suitable vacant home range in which to settle down – increasing the numerical strength of the animal’s new population in the process. Thus are genes transferred between populations.

Individuals which do not find a suitable place to live become vagrants, or nomads, wandering the countryside constantly in search of suitable habitats, and of home ranges of their own, where they can settle down. These animals are “surplus” to the populations that produced them and whether they live or die will make no difference at all to the fortunes of the parental population.

Gene transfers between populations – as a result of the vagrancy factor - creates a degree of homogeneity within nearby population groups. This means that the minor physical differences that may exist between adjacent populations – even though they each have a distinct gene pool – is NOT measurable.

Where populations occur discontinuously - and where contact with other populations has ceased - there is often a very abrupt change in the make-up of the population gene pools. This occurs, in steps, along the length and/or the breadth of the range of the contiguous populations. In some cases the differences in the genetic make up of the different populations manifests itself visibly in measurable morphological changes.

The Red-necked Francolin – an African pheasant - was first collected in Angola in West-Central Africa. It is completely absent from most dry inland regions. In Southern and South Central Africa, however, it extends from just east of Cape Town in South Africa in a long narrow strip following the eastern seaboard of Africa to the Zambesi River and beyond – including intrusions into higher elevations in Zimbabwe, Malawi and Zambia.

Throughout its range the species exhibits bright red legs, and a bright red bare face and throat. In the southern part of its range, the overall feathering of the species is dark brown with no white on the face at all. As the species progresses northwards populations show more and more white feathering on the face and neck until, in northeastern Zimbabwe, the large amount of white on the face is the local population’s most distinctive characteristic. This gradual change of a species’ physical features – along the range of its occurrence - is called “a cline”.

The recognisable physical changes in a species cline – especially IF the changes are specific to totally isolated population groups – normally results in each population group being allocated subspecies (or racial) ranking. This is recorded in the scientific names allocated to each distinct population.

A total of seven subspecies are recognised in the Red-necked Francolin.

Very often, however, the physical change between subspecies is abrupt. Perhaps the best example of this occurs between the Bontebok and the Blesbuck in South Africa. There are now no cline-populations between the population groupings of these two subspecies of the same antelope (Damaliscus dorcas). The intermediate population groups – if there ever were any - have long ago passed into oblivion. Put individuals of the two subspecies together, however, and they breed readily, producing fertile young with physical colouring that is intermediate between the two parents.

The generic name for the Bontebok and the Blesbuck - “Damaliscus” – tells us that they are related to the Topi, the Tsessebe, the Korrigum (Senegal Hartebeest), the Tiang and the Hirola (Hunter Hartebeest).

The second name - “dorcas” - identifies the species – and this separates the Bontebok and the Blesbuck from the other five species that make up the generic family. It also tells us that the Bontebok and the Blesbuck are exactly the same species.

The third name is the sub-specific name, or racial name, which tells us that the physical differences (colour, shape and/or size) between the Bontebok and the Blesbuck are consistently so different the two animals can be recognised as being different races. In this case it is their respective colour-markings that make them distinct.

The Bontebok’s full scientific name is Damaliscus dorcas dorcas – which tells us that the Bontebok is the nominate race (the one that was originally described). The Blesbuck’s scientific name is Damaliscus dorcas phillipsi. The rules of scientific nomenclature are that the generic name is always started with a capital letter and both the species and sub-specific names start with a small letter.

When scientists refer specifically to different subspecies they shorten their names to, for example, D.d.dorcas and D.d.phillipi – and the scientific names normally also appear in italics.

So, what does all this mean to hunters and to hunting? It means a great deal.

If one takes the Greater Kudu, for example – one of Africa’s most sought after hunting trophies – The Safari Club International Trophy Record Book recognises five subspecies. Not only are these subspecies very widely separated, geographically, they are also all measurably recognisable by the differences that occur between their respective body sizes, their skin colourations and/or markings, and/or by the differences that occur in their horn lengths and the circumferences of their horns.

If hunters want to compare apples-with-apples, therefore, it is important that they come to understand the differences that exist between the subspecies and that wherever trophy records are kept that they state, in those records, the subspecies category concerned.

If subspecies rankings were not recognised, no trophy hunter seeking to put his name in the record books, would hunt Greater Kudu anywhere else other than in the range where the Southern Greater Kudu subspecies occurs. This would be because Southern Greater Kudu is “the biggest of them all”. More than thirty specimens of the southern subspecies have been taken with one or both horns exceeding 60 inches in length and with circumferences-at-the-base varying between 11 and 13 inches. This is important for the SCI “score” measurement ratings - which adds together both horn lengths and both horn circumferences. The higher the “score” the better the trophy.

The maximum recorded length of the Western Greater Kudu subspecies, to make a comparison, is less than 47 inches and the horn circumference is less than 10 inches. The comparative figures - for the Abyssinian race is less than 60 and c.10 inches; for the East Africa race it is less than 60 and c.11inches; and for the Eastern Cape race, it is less than 54 and c.11 inches.

So, bearing in mind the fact that all these races, or subspecies, of the Greater Kudu are genetically distinct, making them consistently different from each other, the fact that the trophy record books recognise the differences that exist between their trophies is both justifiable AND desirable. And exactly this same criterion applies to a whole range of other huntable trophy animals that have one or more genuine subspecies within their range, too.

The recognition of subspecies is important for another reason. It keeps international trophy hunters visiting Africa every year, and leaving vitally important foreign currency on the continent. Dedicated trophy hunters, for example, now have five legitimate Greater Kudu trophies to pursue – instead of just one – and their attentions are spread over many more countries than would have been the case had only one Greater Kudu trophy been recognised.

In my opinion, the best African game trophy of them all would be a combination of the incomparably beautiful charcoal-and-white head-and-neck skin-cape of the Eastern Cape Greater Kudu and the magnificent horns of the Southern Greater Kudu. This could be easily arranged, of course, but it would not be recognised as a legitimate trophy head.
 

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