BENEFICIOS DE LA IMPLEMENTACIÓN DE BPM PARA LA PLANTA PROCESADORA DE PULPA DE FRUTAS

A great advantage of studies on palaeoecology of Pleistocene species is that many are still extant or have extant closely related species. Ecology of modem species can be used to suggest the ecology of extinct species, particularly when associated vegetation is known from palynological evidence. Stuart (1982) notes that there is little reason to suppose that the ecology of modem species is different from their Pleistocene

representatives; however, in the case of elephants, this view needs to be modified. The two extant elephant species and subspecies have undergone major changes in their ecology in recent times due to the activities of man on them directly and on their environment (Spinage 1994). This is particularly tme for the “savannah” species of the African elephant (Loxodonta africana) which is now restricted to the savannah plains of sub-Saharan Africa. This is mainly due to contraction of its range through the increase in human habitation and the actions of logging and forest clearance for agricultural land. However, useful comparisons can still be drawn from modem elephants to understand and explain the ecology of fossil species as long as it is recognised that modem ecology

Below is a review of the ecology of modem elephants that forms the basis on which the palaeoecology o f Palaeoloxodon can be reconstructed. The lives of modem elephants are highly complex and only the most important behaviours are addressed here.

3.2.1. Feeding behaviour

The diet of modem elephants tends to be nutrient-poor with a large proportion of stemmy and woody material being taken (Spinage 1994). Digestion in elephants is by caecal fermentation - in this system food is mainly stored in the stomach where little digestion takes place, the food then passes into the small intestine where some digestion occurs, with the break down of cellulose through the action of gut bacteria. However, most digestion occurs in the large intestines which are filled with gut bacteria that slowly break down cellulose and sugars from the plant material. This type of digestion is very inefficient; experiments on the digestion of hay in elephants have shown that only 40% of the hay is effectively broken down, 'with most passing out as faeces. The figure of 40% is very low compared to other herbivorous mammals such as cows where the figure is 60% while in horse it is almost 70% (Schimdt-Nielsen 1988).

Elephants are very large mammals and have a high energy demand. Compensation for poor digestion is met by a vast throughput of food. Schimdt-Nielsen estimated that an adult Afiican elephant bull weighing 5 tonnes would require between 150-200 kg of fresh forage a day in order to maintain its weight. Although not linear, extrapolation of this gives a figure of about 350 kg per day of fresh forage for a 10 tonne Palaeoloxodon

elephant. Experiments on zoo animals by Benedict (1936) showed that the passage of food through the alimentary canal of an Asian elephant was between 10-46 hours

depending upon the food concerned. This rapid throughput means that elephants have to forage for long periods of the day. Observations of African elephants have shown they feed for between 12-14 hours per day (Guy 1974). Thus, over half the day is spent searching for food to meet the high energy demand.

Elephant feeding strategies are varied, ranging from reaching up to the tops of trees by standing on their hind legs and extending their trunk (Sikes 1971), to removing lumps of grass and earth with their trunk and tusks (Moss 1988). Wild elephants have been

fhlit and pushing trees over in order to get at new leaves and shoots in the top canopy (Moss 1988). It is this behaviour in particular which has drastically altered the habitat in which modem Afiican elephant live (Spinage 1994). Until their range was restricted by humans Afiican elephants were able to travel across huge distances in search of trees to feed firom, with those they knocked down being replaced by the time they returned to previous feeding areas. However, now the home ranges are so small that deforestation is a great problem and the remaining populations are forced to have a higher intake of grass in their diet (Sikes 1971; Moss 1988).

There is, however disagreement as to the preferred diet of modem elephants. This is probably a result of the habitat change blurring the original feeding strategies. Some authors (for example see: Sikes 1971 and Laws ef al 1975) state that Afiican elephants are browse-adapted and only feed on grass when forced due to overcrowding or

environmental stress, such as drought. Buss (1961) and Oliver (1982), on the other hand, conclude that grass is the preferred diet with browse only being taken during the diy season. This seems unlikely, however, because diet analysis of Afiican elephants shows throughout the year a great amount of browse although grass is well represented (Spinage 1994).

The food preference of Asian elephants has also been the subject of discussion. Oliver (1982) observed that even in forest environments Asian elephants tend to eat mostly grass, only taking woody material when necessary. However, Mckay (1973) suggests that in fact they show no food preference and that they eat a large range of vegetation. Sukumar (1989) has shown that equal amounts of graze and browse are taken. These discrepancies are particularly important to understand with regard to the present study. The teeth of Afiican elephants are less hypsodont and with a lower lamellar fi’equency (see Chapter 4) than those of Asian elephants, which would imply they eat more browse compared to grass than Asian elephants. However, there may not be such a simple correlation between tooth stmcture and preferred diet. Where only a restricted food type is available, such as in the steppe-tundra environment of the woolly mammoth,

Mammuthus primigenius, it is reasonable to conclude that more grass was eaten since browse was very limited (this is confirmed by the analysis of the stomach contents of the Beresovka fi*ozen mammoth carcass: Sutcliffe 1985). The teeth of M primigenius,

in silica which correlates well with the known diet. The Shandrin mammoth carcass, however, shows a diet with large amounts of browse and fruits (Haynes 1991). This suggests that the mammoths were taking the most plentiful food available at the time. Where elephants exist in a vegetation mosaic, such as Palaeoloxodon antiquus in northern Europe during interglacials where both grass and browse were available, the correlation between tooth structure and preferred diet is even less clear. This problem is further discussed in Chapters 5 and 9.

Whatever the preferred diet of modem elephants it is clear that they eat a large variety of different foods, in order to take in enough food per day. Sikes (1971) provides a detailed list of the common food groups that wild African elephants have been observing feeding upon. She documents the feeding of: browse, bark, grass, fruits, shoots, herbs, shrubs, aquatics, roots and reeds. Similar observations have been made in Asian elephants although fewer roots tend to be eaten (Sukamar 1989).

Elephants will travel large distances in order to find food: Sikes (1971) reports that African elephants move to gallery forest after the rainy season when the trees are fruiting and then migrate to flood plain grassland when the rivers have subsided and fresh grass is available. Haynes (1991) concluded that elephants tend to be motivated to travel long distances with seasonal food changes. Elephants are thus essentially mixed feeders. Like other species, it is highly likely that Palaeoloxodon fed upon a large variety of vegetation ranging from browse and g r^ s to fruits and roots, often depending upon which food was most plentifiil at the time. However, the preferred food was probably browse as opposed to grass. This is suggested by its usual occurrence with mixed woodland as discussed above.

Modem elephants drink large volumes of water a day. Spinage (1994) reports that African elephants drink up to 200 litres per day but can take over 300 litres in one drinking episode. Elephants cannot stray far from water and is likely that Palaeoloxodon

was restricted to habitats near to freshwater sources, either rivers or lakes/ponds. During drought conditions African elephants have been shown to survive for up to 15 days (Spinage 1994) although in the wetter environment which Palaeoloxodon antiquus

3.2.2. Reproductive behaviour

Reproductive rate in elephants is low, with gestation of both Asian and Afiican elephants lasting approximately 656 days with only one calf being bom at each pregnancy (Sikes 1971). Calves are heavily dependant upon their mothers and other members of the herd for a long time, suckling continues for at least two years and the calf becomes fully independent at about the age of 12-15 years. Although females are fertile from about 12 years old until they are about 50 years old elephant populations can quickly drop if there are several years of environmental stress such as drought or

diseased crops (Spinage 1994). It likely that, being of a larger size than either modem elephant species many Palaeoloxodon species had an even longer gestation. According to the equations of Martin (1990) gestation time in a 10 tonne P. antiquus would be approximately 850 days. This type of low reproductive rate makes elephants vulnerable to population crashes.

3.2.3. Social behaviour

Like many large herbivores, elephants tend to herd in stable family units (Eltringham 1997). These groups can range in size from 3-25 individuals, consisting of a matriarch female, older cows, calves, siblings and juvenile males and females. African savannah elephants tend to have larger groups with a mean of 12 individuals (Spinage 1994) while Asian elephants tend to form smaller herds of about 7-8 individuals. This group size difference is probably related to ecology. It is interesting that the African elephant species Loxodonta cyclotis herds in small numbers of 3-4 individuals. This species is confined to the densely forest areas of Central Afiica where large group size may not be advantageous because there is reduced predation (Eltiingham, pers. comm.).

Conversely, on the savannah, large group size may be an advantage since predation is increased. Asian elephants tend to live in more forested environments than the savannah Afiican elephant and they also form smaller herds (Sukamar 1989) which, as with L. cyclotis, may relate to the ecological difference. Being mainly confined to forested environments, or at least showing a preference for wooded areas, it can be inferred that

Palaeoloxodon antiquus probably lived in small herds of 3-4 individuals; consisting of a mother and her sub-adult calves. Small groups of sub-adult males were probably also

for example during Stage 7 (see Chapter 2), may, like other large mammals, have formed larger groups.

Wild elephants have a life span of 60-70 years with death finally occurring due to the complete wearing out of the last molar (M3), see Chapter 4. Since Palaeoloxodon had a larger body size than the two extant elephant species it almost certainly had a longer life-span of possibly 90-100 years. Obviously many animals die before they reach the final stages of dental wear due to predation and illness or disease. This is clear from the fossil assemblages that often contain a large number of molars from calves and juveniles (see section 3.3).

Summary

Using modem elephant species as analogues the following conclusions can be drawn about the ecology of Palaeoloxodon antiquus:

• A wide range of foods was eaten including: browse, grass, fiiiits, shoots, aquatics and roots. The diet was probably dominated by browse although significant amounts of grass would also have been eaten

• Populations could not travel far from a source of freshwater

• Reproductive behaviour was probably very like modem elephants although gestation time was longer than extant elephants

• All species probably lived in small groups consisting of a mother with her offspring of varying ages. Group size was probably small, made up of probably 3-4 individuals • Life span was probably longer than living elephants (c.90-100 years).