A TROPHY QUALITY MONITORING PROGRAMME IN BOTSWANA
AUGUST, 2005

Collection of data commenced in 1997, although on a somewhat limited basis as indicated by the numbers on the graphs. The amount of data collected since 1997 has been increased and represents approximately 80 – 85% of the total number of trophies taken by safari operators in northern Botswana. It is an accumulation of measurements depicted on a frequency distribution chart and will be subject to statistical analysis at the end of year 5, i.e: 2001.

Trophy quality data assessed over the last five years has shown that adequate land tenure conditions and/or ownership of wildlife supports long term commitment to sound wildlife management practices. Trophy hunting is a legitimate form of land use and furthermore, is recognized as being an integral component of wildlife management, as long as it continues to be conducted along the principles of sustainable use.
The quality of trophy hunting is assessed by two principle methods:
• General, qualitative assessments (i.e: not based on measurements). Examples are the size and colour of the mane of a lion or the shape of an elephant tusk. Since these assessments are largely subjective, they are not generally used in formal comparisons and assessments of trophy quality;
• A series of methods for measuring animals taken, so that trophies may be compared according to a set of objective standards taken over time.

Trophy quality may be affected by a variety of factors, that may not be exclusively attributable to safari hunting – factors could be loss of habitat due to drought or human encroachment, disease, over-hunting from subsistence hunters, and disturbance/distractions in breeding patterns due to excessive tourism activities.

THE LOGIC
The logic of using trophy measurements as an index of population status is that the compilation and comparison of systematic measurements of trophy quality give us information that would indicate whether or not the populations are in good condition and that the offtake quotas may be kept the same or even increased; equally, if the populations are in poor condition the offtake quotas may be reduced.
• The monitoring system allows identification of the main genetic sub-populations in terms of trophy quality in which one could compare different areas age for age;

The measurement of trophy quality originates from the fact that sport hunting or fishing are intensely competitive activities. Nearly every hunter strives to take animals which are somehow “bigger” or “better” than his or her colleagues.
• In order to make these comparisons, some system of standardized trophy quality measurement/assessment is required. Usually, these measurements relate directly to the “trophy”aspect of the animal, ie: the horns, antlers or tusks etc. This is appropriate since such trophies are hard, durable objects which do not change much in dimensions over long periods of time, although tusk weights vary due to drying out. In a few cases, however, notably the carnivores, the “trophy” is the skin, or with lion, the mane is an important aspect. After much debate, it has been agreed that it is too difficult to make standard measurements of a skin or mane, so that for these species, trophy quality is based on the length and width of the skull.

• The first step in understanding what kind of information trophy quality figures reveal is to realize that, because of the way that the trophy quality measurement is carried out for each species, trophy quality varies with the age of the animal. This is an aspect of trophy quality monitoring on which very little research has been done and on which very little hard information is available, but some generalizations can be made. With horned animals, trophy quality probably reaches a maximum in early middle age, say about four or five years old for a lechwe (kobus leche), then declines as the horns are worn down with age. This is easily seen with black lechwe (kobus leche smithemani) from Bangweulu in Zambia, for example. In this species, the males get blacker with age: only the very old males get a noticeably blacker skin. Trophy hunters find it impossible to obtain a good horn trophy from a lechwe with a black skin. With SCI measurements, which include the circumference at the base of the horn, the age at which trophy quality reaches its maximum may be a little older, as the loss of the horn tips is to some extent compensated by thickening of the horn base. It is well known, however, that the SCI measurement for buffalo gives high scores for relatively younger animals, since it includes the curling of the tips of the horns which are worn away in older age classes. The Rowland Ward measurement for buffalo, which is based on the greatest width of the outer curve of the horns, reaches its maximum in older animals. In elephant, the tusks continue to grow throughout life, so that in theory, the highest trophy qualities (ie: tusks weights) should come from the oldest animals. The complicating factor here, however, is tusk breakage. In Botswana, where ivory appears to be particularly brittle, many of the older elephants have thick tusks broken off short, giving poor trophies and lower weights. In carnivores, where trophy quality is based on the length and width of the skull, the scores reach a maximum in early middle age, then plateau off. As has been mentioned earlier, carnivore trophies are not usually selected on the basis of skull size, which in any case is very hard to estimate from a living animal, but on the basis of mane size for lion, and overall body size and skin pattern for leopard. In any one population, the average trophy quality of each age class follows a curve that reaches a maximum at a certain age class, then falls away in older animals.

• Within genetic sub-populations, any changes over time may be due to genetic differences: it is well known that certain areas regularly produce a higher proportion of larger trophies than others. This means that for age, animals from one population have larger trophies than those from other populations, irrespective of nutritional conditions. A good example for this point is that of impala: trophies taken in East Africa are much larger than trophies taken in southern Africa. Another example is lechwe, where the Kafue Lechwe produces the largest trophies by a wide margin, followed by the Red Lechwe from the Okavango Delta, followed by the much smaller Black Lechwe from Bangweulu, Zambia. The SCI trophy record register sub-divides many species into regional groupings in an attempt to distinguish between the principal regional variations in genetic differences in trophy quality.

• Habitat and nutritional conditions affecting trophy growth rates. This is a set of factors that means, age for age, animals within the same population and genetic type, may produce larger or smaller trophies at certain periods than at other periods. Or, the differences may be between populations of the same genetic type in areas with differing habitats and nutritional conditions. This situation is particularly well documented for deer species from the northern hemisphere, where the males shed and re-grow their antlers annually. The re-growth of antler within the same individual may differ markedly from year to year, depending on the weather, the status of food availability and the population density affecting the food supply. The effect of nutrition in trophy quality has yet to be demonstrated in any species of African game, but there seems to be little reason to doubt that the effect is present. It seems likely, however, that the effect would be relatively slow in appearing in trophy quality monitoring, since trophy growth in African game species, unlike that in deer, is continuous through the first several years of life at least. One possibility is that one or two years of severe drought could cause the deaths of most of the calves born in those years. When the survivors reach the age at which trophy quality reaches its maximum say five to ten years later, that age class would be under-represented and trophy quality would show a dip for a number of years corresponding to the drought period. Most populations in Botswana are below carrying capacity, with the exception of elephant, and do not show signs of nutritional stress, the effects of which would not cause abrupt changes in trophy quality, and would generally only be detected after several years.

It follows, therefore, that in any one population, two key factors in determining the availability of high quality trophies are the overall numbers of animals in the population (or at least of the males), and the age distribution of the population; that is, the relative numbers of animals of different ages in the population. If the number of animals , or males, is small then there will be few animals in that age class that carries large trophies. Equally, if the majority of the population is very young or very old, there will be relatively few animals in the age class that carries large trophies. These are the factors that allow us to use trophy quality as an indicator of the status of a population.

• The principal factors affecting population numbers and age distributions are likely to be amongst the following:
a) Rainfall, (ie: drought) and flooding levels
b) Availability of surface water
c) Fencing, (ie: veterinary cordon fences)
d) Disease
e) Hunting, illegal resource use, citizen hunting and problem animal control
f) Competition for food resources with cattle or other wildlife

• The final factor that can have a major effect on trophy quality is the selectivity of the trophy hunting community. This in turn depends to a large extent on the skill of the professional hunter, or sports hunter, in identifying large trophies in the field. (As will be shown later in this report, there are indications from the form of the trophy quality results that many hunters or PHs are less skilled in selecting large trophies than we would like to believe). Trophy selection also depends on the time availability on the part of the sports hunter for the hunt. It is also well known that certain groups of sports hunters have special preferences in terms of trophy selectivity. American hunters, for example, tend to hunt “by the book”, preferring to take trophies especially in the case of buffalo, that score highly under the SCI system. European hunters, especially Germans, tend to prefer old and unusual trophies, again, with buffalo. Such trophies usually do not score highly under either SCI or Rowland Ward. When carrying out detailed trophy quality monitoring, it is important to take into account the nationality of clients as well as the number of days taken for the hunt.

Having explored the logic of measuring trophy quality, it is important to define the objectives for this programme. They are defined as follows:

Objective I: to create a database of trophy measurements collected from sport hunted trophies from the Controlled Hunting Areas (CHAs), Wildlife Management Areas (WMAs) and game farms in northern Botswana and to investigate any variation over time.

Objective II: analyse data and demonstrate trends over time through the provision of an unbiased appraisal of trophy quality trends which can serve as a management tool for quota setting purposes, amongst other management functions. The data base could provide an ongoing decision support system to stakeholders, ie: safari operators, community based organizations (CBOs) and government management agencies.

Objective III: where possible, link trophy quality to age through tooth and skull anaylsis.
Objective IV: to provide safari operators with an accurate portfolio of trophy quality taken from their respective CHAs which may be used to justify offtake and serve as a useful means in selling their hunts.