14 Oct 2015

Desert Monitor - Ash Shargiyah Development Company Farm

Whilst birding Ash Shargiyah Development Company Farm, near Jubail on 11 September 2015 we came across a Desert Monitor sitting on a track around the edge of one of the large pivot irrigation fields. Neither Phil nor I had seen this sepces previously and do not know of any other records for the Eastern Province so was a surprising and very welcome sighting. The maps of the range of Grey Monitor show it stopping northwest of the area we saw it and the location is at the southern limit of the species range. The one we saw was not a particularly large example but was probably a metre long. The Desert Monitor Varanus griseus, is a species of monitor lizard with three subspecies, the one occurring in Saudi Arabia being Varanus griseus griseus also called the Grey Monitor. This subspecies is found from Northern Africa throughout the Sahara, Arabian Peninsula and south-western Asia eastwards to north-western India. It has 5-8 narrow grey bands on the back as well as 19-28 bands on the tail, the highest number of bands of any subspecies. Its tail is more rounded that those of the other subspecies and the final size of the adults average around one to 1.3 mtres in length (approximately 55–65 cm excluding their tail) with their overall body size dependent on the available food supply, the time of year, environmental climate, and reproductive state, with males generally larger than females. The body is long and robust, with sturdy limbs, and a long, powerful tail which can be used liked a whip in defence as they are aggressive reptiles. The nostrils of this species are particularly distinctive, comprising diagonal slits much closer to the eye than the tip of the snout. Their coloration can be a simple grey if living in desert-like ecosystems, to more brilliantly colored if living in areas with large amounts of plant growth. It is a carnivorous lizard that feeds on a wide range of vertebrates and invertebrates with the most common prey consisting of lizards and snakes, but can also include ground-nesting birds and other small mammals. They hibernate from September to April becoming most active between the months of May and July. They are active during the day, emerging from their burrows in the early morning, and basking in the sun at the entrance in order to raise their body temperature often staying in their burrows during the heat of the day. During a single day, Desert Monitors range over large distances, usually between five and six kilometres, returning to their burrow before sunset. They are predominantly desert-dwelling, although can occupy a variety of arid and semi-arid habitats with a specific habitat requirement being the presence of sand or soft soil in which tracks can be made for communication and orientation. Their skin is adapted to the desert environment in which they live, and they are excellent swimmers sometimes entering water to hunt for food and have a lifespan of approximately eight years. The below photo is the very poor one I took of the one we saw and below that is a much better one taken by Viv Wilson near Tabuk in the northwest of the Kingdom.
Desert Monitor

Desert Monitor

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