Notes on Red Ochre Experiments - 2000

1. End of 1999 Experiment - Monday 01 May 00 @ 13.00

The grave of the ochred lamb was excavated by Alf Webb and Ian McFarlane. It contained a skeleton which appeared to be entire. Felicity Taylor subsequently examined the bones and confirmed that there were no obvious parts of the lambís anatomy missing.

The bones were stained reddish brown but it was impossible to conclude that this was due to the ochre covering because the soil was itself reddish brown in colour (the site is on the old red sandstone). The soil adhering to the bones seemed redder in colour than both the bones themselves and loose soil, indicating the beginning of a staining process.

2. 2000 Experiment

2.1 Description of lambs and burial

On Monday 1 May 2000, between about 13.15 and 13.45, we buried 5 lambs as described below (graves numbered from North - see diagram). It was a warm sunny day. The lambs had been taken from freezer at ~8pm on Saturday 29 April so were well de-frosted (~40 hrs. before interment). The wife wanted her freezer back - 5 dead lambs take up quite a lot of space. It had been hoped that the burial would be earlier in that week-end but there were logistical problems involving Doug Gentles’ car and obtaining the red ochre. The graves were eventually dug by Robert McFarlane with help from Alf Webb and IDMcF.

  1. Large male lamb with bleeding mouth. (Died and collected from Kevin Rhees-Davies 28.2.00. Frozen next day at 12.00 noon).

    No Ochre applied. Blue string marker on fence. Photo.

  2. Medium sized lamb with bleeding mouth. (Received from Owen Harris 4.3.00 and frozen that day. No indication of how long it had been dead before receipt).

    Thinly ochred (mainly brown). Orange string on fence. Photo.

  3. Small lamb with crossed black legs. (Received from Owen Harris 4.3.00 and frozen that day No indication of how long it had been dead before receipt).

    No Ochre. Blue string on fence. Photo.

    (Grave of 1999 ochred lamb - was re-covered. There were small black beetles in the hole)

  4. Medium sized lamb with small black feet. (Received from Owen Harris 4.3.00 and frozen that day. No indication of how long it had been dead before receipt).

    Thinly ochred (mainly brown). Orange string on fence. Photo.

  5. Small lamb which was smelly. (Received from Owen Harris 4.3.00 and frozen that day. No indication of how long it had been dead before receipt).

    No Ochre. Blue string on fence. Photo.

2.2 Results

2.2.1 Friday 19 May ~10.00 am

#4 grave (Ochred) had been robbed. NB the site had not been inspected since Monday 15 May due to my absence. Lamb completely gone. A large piece of turf had been pulled away (see photo). Mike Gambold (local countryman) suggested that this must mean a large scavenger, possibly a badger or large dog. There was a small piece of faeces on top of the grave which looked like dog rather than fox. MG took to pass on to Mike Sayce (Gwent Wild Life Trust) for analysis - MG later reported that it was from a dog or possibly a fox, certainly not a badger. Photos were taken. Grave was not re-covered.

Given the 4 day period when no inspection had been made, the grave may have been visited on up to 4 occasions (or possibly more) by one or more different scavengers.

2.2.2 Sunday 21 May ~10.00 am

#3 grave (not ochred) had been attacked. The almost entire body of the lamb was on the surface, adjacent to grave #2. The gut had been attacked (possibly the liver). Photo taken. The tail was separated from the corpse, near to the grave. The lamb was re-interred, first the corpse with the tail on top.

2.2.3 Monday 22 May ~08.00 am

#3 grave (not ochred)had been attacked a second time. The tail had been exposed but not the corpse. Photos were taken. The grave was covered up again.

2.2.4 Tuesday 23 May 00 @8.00am

#3 grave (not ochred)had been attacked for the third time. The corpse was on the surface, near the grave. It did not appear to have been further eaten. The body was not re-interred because it was pouring with rain. Photos were taken.

#1 grave (not ochred) had also been robbed and the corpse taken. Alongside the grave was a piece of brown faeces, about 4" to 5" long. Photos were taken. The faeces were transferred to a plastic bag. Later inspection by MG confirmed that they were from a fox.

2.2.5 Wednesday 24 May 00 ~9.00am

#3 grave - the lamb corpse had gone. A pathway could be seen from grave#1 north through the gate into the "horses’" field. At the start of this path, adjacent to and E. of grave#1, was a large piece of brown faeces, about 7" to 9" long. The faeces were transferred to a plastic bag. Later inspection by MG confirmed that they were from a fox. A lambís corpse was in the lane about 400 yards south of grave#3, with the head separated from the remains of the body. Photos taken of grave#3, the faeces and the corpse.

#1 grave (robbed 23 May) apparently untouched.

2.2.6 Thursday 25 May 00 ~9.00am

No apparent grave visits but corpse in lane had disappeared.

2.2.7 Friday 26 May 00 ~10.00am

No apparent grave visits.

2.2.8 Saturday 27 May 00 ~10.00am

#5 grave (not ochred) had been robbed. There were several bones and a small piece of corpse on the surface adjacent to the hole. Photos were taken.

2.2.9 Sunday 28 May 00 ~10.00am

The small piece of corpse adjacent to grave #5 had gone. The bones were still there.

Photos were taken. MG inspected the site. The fact that bones had been left tended to rule out a dog as the scavenger and suggested a fox (which according to MG will not normally eat bones other than very small ones).

2.2.10 Monday 29 May 00 ~10.00am

No apparent grave visits. Grave#2 (ochred) is now the only intact grave.

2.2.11 Tuesday 30 May

Grave 2 had been robbed. Some intestines and bones visible. Very smelly. Thought that the corpse had gone (an assumption subsequently shown to be wrong).

2.2.12 Wednesday 31 May

Grave 2 had been visited a second time. Part of the spinal cord was on the surface together with some bones which seemed to be stained red. Very very smelly.

2.2.13 Friday 2 June

There were faeces by grave 2. Three pictures were taken. The grave seemed now to be empty. MG later confirmed that the faeces belonged to a fox.

The old grave (from the 1999 experiment) showed some indication of digging though nothing seemed to have been found or taken. (This was the ochred grave that had been excavated by Alf Webb and myself on 1 May 2000 to reveal an entire lamb skeleton which was then removed for examination by Felicity Taylor).

3. Discussion of Results

3.1

This second experiment suggests no deterrent effect of ochre to scavengers. The sequence of graves robbed was: Ochred - Control - Control - Control - Ochred. In terms of recorded grave visits, there seemed to be 7 visits to the 3 control graves (ie 2.3 visits per grave) against 4 visits to the 2 ochred graves (ie 2.0 visits per grave). This small difference is insignificant, especially given the incomplete record, especially in relation to Grave #4.

3.2

It is useful to look at the differences between the 1999 experiment (which suggested an effect) and the 2000 version which showed no effect at all. The following factors might have had some impact:

3.2.1

The photographs suggest that the five 2000 graves might have been shallower than the two in 1999.

3.2.2

Less ochre was used on each of the two 2000 corpses than on the single 1999 corpse

3.2.3

The ochre used in 2000 was mainly brown as opposed to red

3.2.4

The five 2000 corpses had been some 40 hours out of the freezer, had completely de-frosted and at least one of these was "high". In contrast, the two 1999 corpses had been out of the freezer for less than five hours and were still partly frozen when they were buried.

3.2.5

In 1999 there was a six week gap between the interment of the two corpses and the first sign of a scavenger raid on either of the graves. In 2000, only between two and three weeks elapsed after interment before the raids began.

3.2.6

In 1999 the raids on the control corpse lasted for a two weeks; thus there was a supply of food in the area until eight weeks after the interment. In the ninth week, the ochred grave was attacked but (as we found out some 11 months later) the corpse was left entire.

By contrast, in 2000 all graves had been attacked within less than five weeks of intermentment.

3.2.6

In 1999 the first grave robbing was detected within 12 hours of the raid and what remained of the corpse was re-buried before nightfall. In 2000 up to 4 days might have elapsed during which the first robbed grave might have been revisited by the scavenger without signs of human interference.

3.2.6

In 2000 there was evidence that a dog might have been involved in the robbing of the first grave to be attacked. Thereafter there was plenty of evidence of fox involvement. The only evidence of scavenger identity in 1999 was fox, no sign of dog.

3.3

Taking the two experiments together, all seven corpses were raided at least once and in six cases the lamb was, eventually, completely consumed or removed from the grave. One fact stands out: the seventh corpse was ochred and remained entire in the ground for almost a year after the first raid.

3.4

A number of suggestions have been made about a possible causal link between (red) ochre and deterrence of scavengers. Certainly Red Ochre was (and still is) used by hunter gatherers for a variety of purposes; as Kevin L Callahan, an email correspondent from the University of Minnesota put it, red ochre "was considered powerful medicine in the Upper Midwest".

There is little doubt that it was and still is used for decorative purposes. Perhaps of relevance to the hypothesis that we are pursuing, it is said to be used as a skin covering by present day hunter-gatherers as an insecticide and as an anti-bacterial agent (BBC Radio4 "Origins" Part III, Feb? 2000). If ochre slows down the decomposition process or if, by selective inhibition of different types of bacteria, it alters that process, this may well explain the causal link we are looking for.

3.5

Looking back, it is easy to identify shortcomings with the experiments:

3.5.1

There was insufficient control over the specification of the corpses used. In particular, the age of the corpses before freezing was generally not known. This is probably of crucial importance if the causal link between red ochre and deterrence is that red ochre inhibits or in some other way changes the decomposition of the corpse.

In addition, the corpses were not of uniform size and no attempt was made to measure them, eg by weighing them.

If this experiment is to be repeated in future, a better source of corpses should be obtained. Lambs were used because they were readily available. They differ from humans in that they are covered with fairly dense wool. It is suggested that piglets might be more similar to humans and so a good source would be a large farrowing unit where there would be a ready supply of fresh piglet corpses. Dead piglets are more likely to be discovered quickly than is the case with dead lambs. Further more, sows farrow all the year round so it should be possible, with a large enough pig farm it should be possible to use fresh corpses as opposed to frozen ones.

3.5.2

The quantity of ochre used is probably important. We did not measure this and have no really reliable record. For the first experiment, Alf thinks we used one 250g jar of red ochre for the single corpse, but Doug Gentles thinks we might have used twice this amount. For the second experiment, both Alf and IMcF recall that there was a 250g jar of brown ochre together with a smaller 75g jar of red ochre. This was used to cover both corpse and so was either a little more than a half or a little more than a quarter of the quantity used per corpse in the first experiment.

The photographs taken after the corpses had been ochred clearly show the different degree of cover. Future experiments should record the amount used relative to the weight and or surface area of each corpse.

It is unlikely that there is any difference in effect between brown and red ochre but, to keep things simple, only red ochre should be used in future experiments.

3.5.3

The depth of the grave is probably important. We have photographic evidence which suggests that the corpse were at least 6 inches below the surface in the first experiment but less deep in the second experiment.

3.5.4

The time of year, weather conditions etc. will also be important. In any future experiment a log should be kept of the weather, especially temperature, which would affect decomposition. The weather would also have an impact on scavenger activity.

Clearly the availability of foxes at this location was not a problem in May (2000) or June (1999). Late April seems as good a burial time as any.

3.5.5

It is important to monitor the graves at least daily. This was neglected in the second experiment, partly because, based on the 1999 experience, we did not anticipate that a grave would be raided so soon after interment.

It would be an added bonus if the area could be monitored by infra red video so that the behaviour of the scavenger(s) towards the graves could be observed!

4. Hypotheses

Before concluding that there is no effect, it is worth exploring any hypothesis which might fit the facts as so far determined.

4.1

A possible hypothesis goes something like this:

Red ochre (or any colour ochre) has some effect on the bacteria or other biological or chemical processes which cause the decomposition process. Provided that decomposition is not already too far advanced, the ochre either masks the smell of decomposition or, more likely, makes it unattractive to foxes or similar scavengers. There is a critical quantity of ochre needed to accomplish this effect (ie grams per gram of corpse or per square cm of corpse surface. There are important time factors and windows involved; a maximum time before the ochre is applied, a minimum time before it acts as a deterrent, and so on.

4.2

There are many other alternative hypotheses that fit the facts, for example:

4.2.1

In 1999 there was only one scavenger involved. Whilst attacking the second, ochred grave it was disturbed and could not return the next day for a number of possible reasons, eg it had been shot or had found a better food source. Thus it was just coincidence that the second, ochred grave was not robbed. In 2000 there were many, hungrier scavengers so all graves were robbed in a random fashion.

4.2.2

In 2000, the first (ochred) grave was robbed by a dog and was left undisturbed for a few days. This attracted many other scavengers to the site and subsequently to the other graves.

4.2.3

Only some scavengers are deterred by the effect of ochre. In 1999 there was one such scavenger but in 2000 there were many, at least one of which was not deterred by the ochre effect.

4.2.4

The robbing of the graves is completely random - red ochre has no effect.

5. Suggestions for further work

The following research should be carried out:

5.1

Confirm that red ochre has anti-bacterial properties, both following up the anecdotal evidence from the BBC Radio 4 source and determining an experimental scientific basis. If this can be confirmed:

5.2

Demonstrate the biological and bio-chemical effect of ochre on corpses in the laboratory

5.3

Repeat the experiment using mainly ochred corpses but is a more controlled fashion as indicated in section 3.5 above.