Rodent bones tell the story of a blooming desert

nature, evolution, wildlife, desert, Israel

Researchers have uncovered a large quantity of bones belonging to Tristram’s jird, a common rodent in Israel whose body length does not exceed 15 cm, providing the first biological evidence of the agriculture that flourished in the northern Negev region some 1,500 years ago. The bones were found near ancient fields tended by Byzantine farmers in the region, in an era when large parts of the Negev were colored green.

“Today, Tristram’s jird is common in the Mediterranean areas of Israel. In recent years, with the expansion of agriculture in the Negev, its habitat has expanded to the south. Now we have found bones of this rodent dating back to the Byzantine period in areas that are currently arid and do not offer the habitat it requires. The findings show that Byzantine agriculture was so well-developed that it had an impact on species diversity in the Negev,” explained Prof. Gur Bar-Oz of the University of Haifa, who is heading a project that is researching the collapse of Byzantine cities of the Negev.

During the Byzantine period, which extended from the third to the seventh centuries CE, settlements were established throughout the Negev. The settlements were abandoned suddenly in the seventh century with the beginning of the Islamic period. Archeological evidence from the Negev, together with ancient historical texts, indicates the presence of extensive agriculture in the region during this period. Until now, however, no biological evidence had been found corroborating this rich agricultural past.

The current archeozoological study is being conducted by research student Tal Fried, together with Dr. Lior Weissbrod, Dr. Yotam Tepper, and Prof. Guy Bar-Oz from the Institute of Archaeology at the University of Haifa. The researchers have managed to uncover such evidence, in the form of rodent bones found in pigeon nesting compartments adjacent to agricultural fields. Their research findings have now been published in the Journal of the Royal Society of the British Academy of Sciences.

Based on modern data, the researchers know that the two commonest species of rodents in the Negev – the gerbil and Tristram’s jird – live in distinct areas according to climactic and topographical features. The gerbil is found in arid areas with less than 200 mm of precipitation a year that are dominated by sandy soil without cover of vegetation. Tristram’s jird, by contrast, is found in areas with more than 200 mm of precipitation a year where the soil is moist and covered with greenery. Naturally, agriculture is also concentrated mainly in the latter area.

As mentioned above, the rodent remains were found in excavations of several pigeon nest compartments in agricultural fields close to the rural settlements of Shivta and Saadon. The location of the compartments underscores the importance of pigeons to Byzantine agriculture in the region. The pigeons were raised so that their droppings could be used to fertilize the loess soil of the Negev, which has a low mineral content. However, the current important findings were not left by the pigeons themselves, but by the subsequent occupants of the nest compartments after the pigeons had gone.

“In some of the pigeon nest compartments we excavated, we identified the layer dating back to the time when the compartments were destroyed and abandoned. Immediately above this layer, we began to find a large quantity of rodent bones,” recalls Dr. Yotam Tepper, who directed the excavation. “Since most of the bones bore signs of digestion, we immediately understood that these were remnants of food eaten by birds of prey – barn owls or other species – that took the place of the pigeons after the compartments were destroyed,” concluded Dr. Weissbrod and Tal Fried.

The inspection of the rodent bones revealed numerous gerbil bones, but also bones of Tristram’s jird. As noted above, the sites where the researchers found the bones are all in areas that now have an average of less than 200 mm precipitation a year; indeed, the average precipitation in Shivta is less than 100 mm a year. The soil in all these areas is dry and wind-blown, and accordingly the presence of Tristram’s jird is surprising. “Our finding shows that the Byzantine agriculture in the area was so well-developed that it completely changed the pattern of species distribution in the region,” the researchers explained.

“During the period in question, areas that are arid today were greener and more fertile. The fact that we find the Tristram’s jird bones from the period after the fields were abandoned shows that the environmental change was so profound that even after the area was abandoned, it took some time for the environment to become arid once again. This is testimony to the impact of Byzantine agriculture, which continued to influence nature in the area long after it was abandoned.”

The researchers add that it is possible that the climate in these areas was wetter during this period than it is today, encouraging the development of impressive agriculture. Despite this, the farmers needed to use specialized technological means in order to store water, improve the fields, and create an agricultural habitat in the region.

“This was the last period of agriculture in the Negev until the emergence of Zionism and the settlement of the Negev in accordance with Ben-Gurion’s vision. We are continuing to explore the remnants from this period, and we are curious and excited to understand the processes that led to the collapse of Byzantine society in the Negev. We still do not understand why the agricultural system they established ultimately failed. This subject is very relevant today, particularly in an era of climate change in which we need to adapt to changing environmental conditions that are leading to the expansion of deserts around the world,” Prof. Bar-Oz concluded.

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