Chapter 1: Elephants now not fossilized
Why have so many bones and whole skeletons of the woolly mammoth and its companions been preserved in the Far North? Is it normal that so many bones are preserved up there? If so, we must ask ourselves: Have just as many bones of this elephant also been preserved in the earlier times of earth’s past? Why is the surface of the bones not cracked? Why is it not flaking? How much is left now of the elephant in the wilderness, when it dies? Are its bones also preserved, changed into fossils? When will they be preserved and when not? What do we find in Africa today? How many of the 5,900 elephants, which have died during the great drought of 1970-71 in Tsavo East N. Park, in Kenya, have been preserved as fossils? What have scientists found out about this?
Malcolm Coe, University of Oxford, England, reports about his findings in the book Fossils in the Making (1980:59): "Drought conditions have also led to massive mortality of large herbivores in Kenya since 1960. The population of the Nairobi National Park was halved in 1961 due to drought and floods (Foster and Coe 1968). Later in 1973-74 the population of the same area, together with the adjacent Athi Kapiti plains, suffered a 75% reduction in numbers due to drought (Casebeer and Mbai 1974). Under these circumstances of catastrophic death the amount of carrion available completely swamps the scavengers, which in consequence leave a large percentage of the carcasses to be decomposed by invertebrate and microorganisms. At such times a large number of entire skeletons could become fossilized if they were buried. In the instances noted above the carcasses were well distributed over the plains, with large aggregations of material around water holes and other water sources.
"In 1960-61 the drought that affected areas in central Kenya also affected the Tsavo East National Park, where up to 300 rhinoceroses died along the Tsavo River. A later and more severe drought occurred in Tsavo in 1971-72, and on this occasion the main area influenced was quite different. As a result of these conditions up to 7000 elephants died and, as in the Nairobi National Park, the majority of carrion produced was virtually unaffected by scavengers. Corfield (1974) has studied this mortality and has demonstrated that the main area affected coincided with the 10" (25 cm): 10% rainfall probability isohyet." - Coe, M. (1980:59).” [Wo 250 mm Regen im Jahr gefallen ist.]
Aerial photograph of two elephants during the great drought of 1970-71 in Tsavo East National Park, Kenya, East Africa. Most of the trees are now uprooted and smashed. From: N. Meyers (1973:127) Fig. 4. During the great drought, the grasses, shrubs and trees, which are still left, are drying up. This dry, brown grass and browse is too low in protein and too high in fiber. It contains now only about 2% crude protein (dry weight) or more. The elephant is still eating it, because there is nothing else left. But the animal is not able anymore to digest it. Because the micro-flora in its digestive tract has become now too weak or has died off already. The elephant will starve to death after a few dry months with a full stomach, due to lack of digestible protein.
Remains of elephant, head severed, with broken bushes and much devastation to skyline, during the great drought in Tsavo National Park, in Kenya, East Africa, 1970-71. From: N. Meyers (1973126).
Dead Black rhinoceros and elephant in Tsavo East National Park, Kenya, East Africa, during the great drought of 1970-71. After: N. Meyers (1973:128) Fig. 5. Thousands of elephants and hundreds of Black rhinos starved to death with a full stomach, when their food contained only 2 % crude protein (dry weight) or more, because they were not able anymore to digest it anymore.
The Decomposition of Carrion
How much of these carcasses has been preserved as fossils? How many of their bones, skeletons and whole bodies are still there?
Malcolm Coe in the book, Fossils in the Making (1980): "During the course of this (1970-71) drought the author (Coe 1976) located and observed the decomposition of elephant carcasses. Four bodies were located and observed in detail while up to 100 others have been the subject of irregular observation from the time of death to the present (fig. 4.1). It was found that, in the absence of scavengers, a large carcass would pass through all the wet stages of decomposition (that due to the loss of soft tissues) in two weeks, while in the wet season a further 21 days would see the skin and sinews removed by invertebrates (Dermestes beetles) at the astonishing rate of 8 kg per day. During the dry season the skin remains intact for many months since the lack of water acts as a severe limiting factor to the activity of Dermestes beetles.
"The fate of the skeletal remains is of great importance to the paleontologist, and it is surprising that comparatively few detailed studies have been carried out on this important if aesthetically distasteful topic. In open habits in Tsavo where the surface temperatures of bones may be expected to experience a diurnal temperature range of at least 35-40°C, they begin to flake and crack within five weeks of death. These changes may be slightly delayed during the dry season when the skin remains intact for an extended period. It is only, however, for the larger mammals (e.g., elephant, buffalo, rhino, and giraffe) which possess a particularly thick and keratinous skin that this covering will afford such protection, and even then it is unlikely to do so for more than a few months. In addition to the bones, the teeth will also develop vertical cracks and the outer layers will begin to flake within the same time scale." - Coe, M. (1980:60).
"During the observations of the decomposition of elephant carcasses in Tsavo, the majority of the bodies were located in the open on red lateritic soils where exfoliation was apparent within five weeks. A single body was located on porous gravel close to the Aruba Dam where during rain the nitrogenous putrefaction liquids were rapidly leached away. In this situation rhizomatous grasses rapidly recolonized the surface of the ground, and within two months of death the whole skeleton was covered with vegetation except for a small portion of the skull.
"Subconsequent observation of this carcass has demonstrated that even a shallow covering of this type is sufficient to reduce the degree of bone flaking. In addition to the creation of a less extreme microclimate around the skeleton, the accumulation of litter at the soil surface completely buried the smaller vertebrae, ribs, and other small bones within two years (fig. 4.2). In this situation bony material was stained brown by humic materials and was consequently less bleached than that in the open. Such vegetation cover is not permanent, though, and a further severe drought in 1974 once more exposed all the larger skeletal remains." - Coe, M. (1980:60).
"When such large amounts of carrion are produced and initial scavenger attack thus reduced, it might be expected that the skeleton would remain intact. Elephant carcasses observed over five years were scattered up to 50 meters from the site of death by trampling, scavenger attack, and elephants, which have been shown by Douglas-Hamilton (1972) and Trevor (personal communication) to carry tusks and bones for considerable distances.
"The observation of such large-scale mortality poses the interesting problem of how high the chances are of any of this material being fossilized. In the case of the massive elephant mortality in Tsavo it appears unlikely that, except for bodies being buried in gullies by subsequent rainfall or being transported and redeposited in silt by one of the main rivers, much if any of this material will be mineralized. The rapidity with which skeletal remains are fragmented by heating and cooling suggests that fossilized material which is recovered without appreciable signs of weathering must have been rapidly buried after death either as a result of rainfall, eolian (wind drifted) deposits, or other catastrophic phenomena such as volcanic ash." - Coe, M. (1980:61, 62).
"Smaller species and the juveniles of larger species will be broken up and fragmented much faster than the remains of larger species, though it must be admitted that they might at the same time have a greater chance of being interred. The decomposition of an aardwolf (Proteles cristatus) carcass was observed in November 1975 in Tsavo East National Park, and the soft tissue from this body was completely removed by dipterous larvae in 3 days, leaving an intact skeleton and hair remaining on the soil surface. Torrential rain 2 days later partly buried the long bones, while the smaller structures were washed down a gentle slope up to 2 feet (61 cm) from the site of death." (1980:63).
Andrew P. Hill says in the book Fossils in the Making (1980:148) about East African mammals: "As a carcass loses its soft parts, the bones of the skeleton become disarticulated from each other and scattered. Under these conditions being considered here, this occurs fairly rapidly after death. In the case of a medium-sized bovid carcass laying on the land surface, within a day or so most of the flesh usually has disappeared, and the forelimbs have become separated from the rest of the carcass. This is due mainly to any carnivore that might have caused the death, and to the subsequent depredations of vultures and other scavengers. After a few weeks the remains are largely disarticulated, and some elements, especially part of the forelimbs are largely disarticulated, and some elements, especially part of the forelimbs, have been scattered so widely as to remain undiscovered despite extensive searching around the site of death. ... Skin and ligaments remain attached after fifty-three months. The rate and manner of disarticulation seem to be affected by size, anatomy, and the local situation. Small bovids (= cattle) were disarticulated and scattered rapidly." - Hill, A. P. (1980:148,149).
Decomposing Elephant
What happens, when an elephant dies, when it begins to decompose? Malcolm Coe gives us more details in "The decomposition of elephant carcases in the Tsavo (East) National Park, Kenya". He writes: "Low rainfall in 1970 and 1971 led to a serious shortage of food over much of Tsavo (East) and, as a result, up to 5 900 elephants died over a period of about 18 months (Corfield, 1973). Thus, over this period, up to 30 per cent of the recorded elephant population died. Corfield (1973) and Phillipson (1975) have shown that the regions in which maximum mortality occurred coincided with areas where least rain had fallen and, consequently, primary production was particularly low." (1979:71).
Field observations of carcase decomposition
Carcase E 1 (Plate 1): Male elephant located 3.5 km east of Buchama road 5.9 km from Aruba. The animal died on its left side in open grassland with many scattered Commiphora bushes. It is estimated that the body was visited within 12 h of death. The shoulder height gave an estimated age/weight of 1750 kg (Laws, 1966).
Day 1 (17 November) Plate 1a): Rigor mortis had set in and the penis was fully extruded. Several dung boli had been voided from the anus and a small quantity of fluid was present at the mouth and the tip of the trunk. A small number of blow flies but no vultures were seen.
Day 4 (20 November 1971, short rains started): Three white-backed vultures and one Marabou stork sitting on the corpse. Body now fully distended with the upper limbs raised clear of and parallel with the ground. Bloat had extended to include the thorax, head, rump and limbs down to the lower joints. The bloat condition even extended to the feet which were convex in outline. Two large puncture wounds had developed between the fore limbs, and were bubbling gases and a bloody stained putrefaction liquid. ... The measurements around the belly had increased by 30 cm to 222 cm." (1979:71-75).
Day 6 (22 November 1971 Plate 1 b): The whole body was surrounded by a pool of black putrefied liquid. ... The abdomen had completely collapsed through an enlarged hole in the genital region, the liquid was contributing to the large pool of putrefaction liquid.
Day 12 (28 November 1972): All flesh from the head, thorax and spine absent, and the dorsal surface of the body covered with a layer of dried skin. The skin on the upper right fore limb still intact, but the radius and ulna of the left limb completely exposed. Soles of the fore and hind feet removed by spotted hyaenas. Right hind limb still intact, but the material covering the left hind limb had been eaten by hyaenas. Toe bones from this limb were found 25 m from the death site. The tail still intact but the hairs from the tail had been chewed off to the base by a scavenger. No more than two dozen flies present over an area of fatty exudate on the rump.
Day 20 (6 December 1971, Plate 1 c): The whole body covered by large number of newly hatched C. marginalis and C. albiceps. ...
Day 24 (10 December 1971): All soft parts had now been removed except of bunches of ligamentary ‘festoons’ and cartilage attached to long bone epiphysis. The skin and bone remaining on the ground (excluding gut contents which were still unchanged) weighed 382 kg.
Day 35 (21 December 1971): Thorax dragged clear of site of death by spotted hyaenas. Underside of thorax sheltering vast numbers of dermestid larvae. Outer skin still relatively intact but being eroded from below by dermestids.
Day 53 (8 January 1972): Most of the skin over the upper side of the body almost entirely eaten by dermestid beetle larvae. Where skin still persistent, now comprising no more than 1 mm layer of pock-marked skin. Small plates of the thick back skin still lying on the ground clear to the main body and unaffected by the activities of dermestids." - Coe, M. (1979:75, 76).
Day 231 (5 July 1972, Plate 1d): All skin gone from the corpse site. Keratinous stratum corneum from the soles of the feet still visible on the soil surface up to 50 m from the death site, attached to soil by Tianeid moth larval tubes. Gut contents still visible on the soil surface unaffected by either dung beetles or termites. Ground littered with the chitinous remains of dipterous and dermestid larvae. Molar teeth in upper jaw extensively cracked. Bones exfoliating from the outer surface and extensive longitudinal cracks developed in all large bones.
Day 649 (28 August 1973). Condition almost unchanged since 1972. Bones greatly bleached, outer surface almost completely exfoliated and longitudinal cracks now up to 1 mm wide. Ants carrying away bone flakes. Ribs and other small bones now half buried in soil. Outer surfaces of many teeth shattered but still attached to jaw.
Later visits (March 1974 and November 1975): Bones still flaking from the outer surface. Small terminal limb bones nearly completely buried. Epiphyses of several long bones separated from diaphyses. One femur transported 100 m from the death site. Ribs partly buried with upper parts shattered by trampling. Hind molars still in upper jaw but outer surfaces missing. Skull occupied by geckos." – All animals found dead lay on their sides. – Coe, M. (1979:76, 77).
Phase I and II
Phase I – Bloat Phase
a. Primary bloat (1-2 days). Within 24 h of death, autolitic digestive processes produced a pronounced distention of the abdomen with the midline girth increasing up to 15 per cent.
b. Full (tissue) bloat (2-3 days). Following the more local abdominal bloat, swelling then extends to include the head, trunk, thorax and limbs. In the latter phases this swelling even included the thickly keratinous feet which become greatly extended.
Phase II – wet or collapse phase (up to 18 days)
Entry to this phase is determined by the point at which the bloat is determined by the release of accumulated gases and putrefaction fluid. Acceleration of this phase often occurs through the activity of vertebrate scavengers, particularly where young animals (under 4 years) are concerned.
a. Primary collapse or leak stage (4-5 days). The bloat pressure is first released via a series of small punctures through which gas bubbles and liquid are released. These holes most commonly develop either side of the vertebral column, behind the ears and between the ribs where small pockets of gas and liquid under pressure find their way through the epidermis and between the plates of the thickly keratinous stratum corneum
b. Total collapse stage (7 days). Fluid and gas loss increases to include the mouth and other natural openings in the complete deflation of the body cavity. Collapse of the abdomen and anterior thoracic cavity are accompanied by extensive bacterial erosion of the body wall and the accumulation of a large pool of putrefaction fluid around the corpse. – Coe, M. (1979:77).
Phase III – Dry phase (20 years in large bodies)
The putrefaction paste dries to a hard shiny black crust that surrounds the body and supports a rich insect fauna. Except for isolated patches of fatty tissue on limb joints, all soft tissues have now disappeared. The body and limbs are enclosed by a hard envelope of dry skin. Punctures in this layer allow access by large numbers of Dermestes vulpinus whose larvae consume the remaining skin from the inside, where a favourable microclimate exists for their development.
The skin may be consumed in up to 3 weeks on a large corpse during the wet season or in many months in the dry season. Indeed, the persistence of skin and its state of erosion by dermestid beetles are a reliable indicator of the time lapsed since death. Persistent skin on carcases of large mammals indicates that the animals died during the dry season or at the very end of the previous wet season. Thus, in areas affected by drought, this period could sometimes be as much as 2 years. Once the skin has been consumed and the bones are exposed to direct sun and rain, the bones may persist for well over 10 years and, in the case of large animals, this period could well approach 40 years. – Coe, M. (1979:78).
Corfield (1973) has estimated that, during 1970-71, 5 900 elephants (37 per cent juveniles, 13 per cent sub-adults, 50 per cent adults) died in Tsavo. ... It is quite clear from the observations carried out on the accumulated elephant carrion in Tsavo that, within 18 months, virtually none of the large number of bodies observed remained intact. Limb bones were disarticulated and chewed by scavengers and even large skulls were transported up to 100 m from the site of death by other elephants. Under these circumstances one is left to postulate that the fossilized remains of intact large vertebrate skeletons must have been buried at the time of death or very shortly afterwards.
Additionally, in the prevailing climatic conditions in Tsavo, the bones and teeth are cracked by the agency of dehydration and diurnal temperature fluctuations within weeks of death, again suggesting that fossilized skeletal material that lack clear signs of weathering must have been rapidly incorporated into the lithosphere, the agency responsible for such rapid incorporation being by means of water, wind-blown material or volcanic activity. ... Of the total number of animals estimated to have died, only perhaps those few animals that died wholly or partly in contact with water would have stood more than a minor chance of being buried and subsequently fossilised. – Coe, M. (1979:84).
Comment: This will help us later on, to find out, why and how the woolly mammoth of northern Siberia and Yukon/Alaska has perished. It will help us to find out, why its bones have not also fallen up there to dust within a few years.
Elephants in Tsavo East National Park, Kenya, during the great drought of 1970-71. Also this elephant has starved to death with a full stomach, because its food contained too little crude protein (only 2% dry weight) or more, and therefore also too little digestible and metabolizable energy. Top: Elephant corpse three days after death. Bottom: Elephant corpse three weeks after death. After: M. Coe, Fossils in the Making (1980:61) Fig. 4.1a, 4.1b.
Top: Skeletal remains of this elephant carcass one year after death. Bottom: Skeletal bones of this elephant partly buried two years after death. Bones are cracking, are flaking off. After: M. Coe, Fossils in the Making (1980:62) Figure 4.2a, 4.2b.
Head of African elephant (Loxodonta africana) in Rwenzori National Park, 11 months after it died. Bones begin to crack, to flake off. After: A. P. Hill, Fossils in the Making (1980:149).
This drawing is from R. D. Guthrie, Frozen Fauna of the Mammoth Steppe (1990) Fig. 2.21. Professor R. D. Guthrie, University of Alaska, at Fairbanks, says here, after studying the elephant in Africa: Few animals become fossils. This elephant died a natural death away from depositional environments out in the open African savanna. Scavengers have removed most easily edible parts. Only the thick, dried hide and bones remain. The ears, feet, and tip of trunk are thin-skinned and were the first to be eaten. Eventually, what remains will be scattered by hyenas, but it is unlikely that any portion will become fossilized. That is true for most large mammals.