What we know
Blick Mead, east of Stonehenge, is a chalk spring where Mesolithic people hunted aurochs and came back for a very long time (see Buried Landscapes of the Avon). On the ridge to the west are the big Mesolithic posts found under the old car park. Five radiocarbon dates on their pine charcoal span about 8820–6590 cal BC (Allen & Bayliss 1995, in Bronk Ramsey & Bayliss). Nearby runs the palisade ditch, which is poorly dated. It is put in the Late Neolithic on archaeological grounds, perhaps 2900–2400 BC, and the only date is from an Iron Age burial cut into it, 780–410 cal BC (Lawson 1997; Bronk Ramsey & Bayliss). The posts and the palisade are something like 4,000 to 6,000 years apart. I have suggested that the posts held machans, raised hunting platforms like those E. P. Stebbing drew in India. I have also wondered whether a palisade with gaps worked like a bull-run fence. Both ideas need herds to pass by.
So where would herds actually walk to water? On the chalk, the answer depends on winter. The climate of the period was much like today's, and the Avon gets frosty in a cold spell but doesn't freeze solid (see Britain, 5000–2000 BC: no ice, no catastrophe, a familiar climate). A spring, meanwhile, stays open. So the model below gives open springs an advantage in frost: a herd will walk 0.5, 1 or 2 km further to reach one.
How cattle walk
The rules come from studies of domestic cattle, not aurochs, but they are the best measurements there are.
- Climbing is costly. On a treadmill, cattle used about 26 J per kg for each metre climbed, against 2 J per kg per metre on the flat (Ribeiro et al. 1977). So a metre of climb costs as much as about 13 metres on the level.
- Going down costs too. Steers walking down a 6% grade used about as much energy as walking up it (Di Marco & Aello 1998).
- Steep ground is avoided. Cattle start avoiding slopes of 20% (Ganskopp & Vavra 1987). Land over 60% is treated as ungrazable (Holechek 1988), and the model treats it as impassable.
- Distance from water matters. The rangeland rule of thumb is full use up to 1.6 km from water and half use from 1.6 to 3.2 km (Holechek 1988). GPS-collared cattle often go further than that (Millward et al. 2020).
- Trails find the easy line. Real cattle trails from water were 11% shorter than GIS least-effort paths. They ran on slopes of 5.2% across pastures that averaged 13.5% (Ganskopp et al. 2000).
The model puts these rules on Environment Agency LiDAR at 5 m resolution. It starts 2,145 herds on the high ground, one every 250 m wherever the ground is at least 25 m above a river. Each herd takes the cheapest route to water. The water is the Avon, the Till, Blick Mead, and five springs marked on the 1880s OS six-inch maps: four at Winterbourne Stoke and one at Durrington. Where many routes share a line, that is a busy track.
Results
The posts are not on a track. In every run, no busy route (one used by 25 or more herds) reaches them. In the hardest frost the closest busy route comes within 615–730 m of the posts when Blick Mead is the only spring (Figure 1). With the OS springs added (Figure 2), the closest is about 1.3 km away (1.28–1.39 km).
They sit on the edge of Blick Mead's winter catchment. With no advantage for springs, the ground around the posts drains to the lower Avon. Give the springs the smallest advantage tested, 0.5 km, and the same ground switches to Blick Mead. It stays with Blick Mead at every frost setting, with or without the other springs. The posts look more like a watch point over herds drifting towards the spring in winter than an ambush on a path.
| Figure 1. Cattle walking rules in a hard frost (open springs worth a 2 km detour; Blick Mead the only spring). Purple marks the ground whose herds drink at Blick Mead: 463 of 2,145 herds, from 37.7 km². The busy routes converge on the spring but pass the posts at a distance. |
Blick Mead is not the only draw. In the hardest frost tested, with all six springs, Blick Mead takes 328 herds from 27.9 km², the most for any single spring. The Winterbourne Stoke springs take 268, 261, 52 and 34, so 615 between them, and Durrington takes 182. In milder frost a Winterbourne Stoke spring beats Blick Mead: 142 herds to 90 at 0.5 km, and 185 to 128 at 1 km. Blick Mead is the busiest spring only at the hardest setting. Even so, the posts stay in its catchment.
| Figure 2. The same hard frost with the five springs from the 1880s OS six-inch maps added (green dots; red marks herds going to those springs). The Winterbourne Stoke group takes much of the Till side, but the posts remain in Blick Mead's catchment (purple). |
The palisade is not a funnel. Few routes come near it. Making it a solid barrier changes almost nothing: in any run, at most one of the 2,145 routes changes its water. If it steered animals, it was in a drive, which this model cannot test.
Limits
This is a simple exploratory model, not proof. There are no GPS tracks to test it against. The rules come from cattle, and bison, the nearest wild comparison, avoid slopes more strongly and are less tied to water (Allred et al. 2011). The rivers are today's, from OpenStreetMap. The springs are Victorian map labels placed to within ±40–60 m. The posts and the palisade are thousands of years apart, so the model puts them on one landscape only for comparison. Some settings are my own choices, such as the steepness penalty reaching ×10 at a 60% slope.
GPS tracks of cattle grazing chalk downland for conservation would be the real test.
References
- Allred, B.W., Fuhlendorf, S.D. & Hamilton, R.G. (2011). The role of herbivores in Great Plains conservation: comparative ecology of bison and cattle. Ecosphere 2(3): art26. https://doi.org/10.1890/ES10-00152.1
- Bronk Ramsey, C. & Bayliss, A. Dating Stonehenge. CAA conference proceedings, ch. 5 (reporting Allen, M.J. & Bayliss, A. 1995, Appendix 2: the radiocarbon dating programme, in Cleal, Walker & Montague 1995, Stonehenge in its Landscape, pp. 511–35). https://proceedings.caaconference.org/files/1996/05_Ramsey_Bayliss_CAA_1996.pdf
- Di Marco, O.N. & Aello, M.S. (1998). Energy cost of cattle walking on the level and on a gradient. Journal of Range Management 51: 9–13. https://doi.org/10.2307/4003556
- Ganskopp, D., Cruz, R. & Johnson, D.E. (2000). Least-effort pathways?: a GIS analysis of livestock trails in rugged terrain. Applied Animal Behaviour Science 68: 179–190. https://doi.org/10.1016/S0168-1591(00)00101-5
- Ganskopp, D. & Vavra, M. (1987). Slope use by cattle, feral horses, deer, and bighorn sheep. Northwest Science 61: 74–81. https://hdl.handle.net/2376/1753
- Holechek, J.L. (1988). An approach for setting the stocking rate. Rangelands 10(1): 10–14. http://hdl.handle.net/10150/640265
- Lawson, A.J. (1997). The structural history of Stonehenge. Proceedings of the British Academy 92: 15–37. https://www.thebritishacademy.ac.uk/documents/3913/92p015.pdf
- Millward, M.F., Bailey, D.W., Cibils, A.F. & Holechek, J.L. (2020). A GPS-based evaluation of factors commonly used to adjust cattle stocking rates on both extensive and mountainous rangelands. Rangelands 42: 63–71. https://doi.org/10.1016/j.rala.2020.04.001
- Ribeiro, J.M.deC.R., Brockway, J.M. & Webster, A.J.F. (1977). A note on the energy cost of walking in cattle. Animal Production 25: 107–110. https://doi.org/10.1017/S0003356100039118
Data: EA LiDAR Composite DTM 1 m © Environment Agency (OGL v3). Palisade ditch (HE_UID 219850) and Avenue from Historic England Aerial Investigation & Mapping, © Historic England (OGL v3). Rivers and the Blick Mead point © OpenStreetMap contributors (ODbL). Springs from the OS six-inch maps, reproduced with the permission of the National Library of Scotland, and GB1900 (CC BY-SA). Car-park post positions after Vatcher & Vatcher 1973 and Allen 1995 (HE Monument 219856).