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Caspian Monitor Print E-mail

Reptiles of the Kara-Kum Desert - Part 2:

The Caspian Monitor Lizard Varanus griseus caspius

First published in the Aquarist and Pondkeeper, 1991.
 
Varanus griseus is perhaps the most widespread extant monitor lizard. It is found from northwestern Africa through all deserts as far as western India. Within this range three subspecies are recognised; V. griseus griseus from Africa the Middle East and Iraq, V.griseus koniecznyi from eastern Afghanistan through Pakistan to India and V.griseus caspius from eastern Iran, western Afghanistan and the adjacent part of the U.S.S.R. The Caspian monitor is distinctive because it grows to a larger size than its relatives and has a tail which is compressed rather than round in cross section. Compressed tails are found in all monitor lizards that spend long periods of time in the water, enabling them to use the tail as a rudder when swimming. It is of no use to a desert animal, and so presumably it is a relic from long ago when they lived in a wetter environment.

The Caspian monitor is one of the rarest monitor lizards in the world; because it is so rare it is protected in the U.S.S.R. and all trade in this species is banned under international law. Almost all of the information published on its ecology is in Russian, and as a result it is poorly known in the western world. The lack of information combined with its scarcity made it of particular interest to me, and for several years I had been beseiging the Soviet Union with requests for more information about the ecology of this rare and remarkable reptile. In September 1989 I finally came face to face with some of my correspondants from the Moscow Zoo Department of Herpetology and the Soviet Union of Nature Conservation at the First World Congress of Herpetology in Canterbury. They invited me to visit the U.S.S.R. to find out for myself how the Caspian monitor spends its life. My visas and permits were issued promptly and in spring 1990 I found myself in the Repetek Desert Reserve in the state of Turkmenistan to spend five weeks studying this magnificent lizard.

ImageI planned to take measurements and temperatures from as many specimens of the Caspian monitor as possible, and to make observations on their diet, thermoregulatory behaviour and habitat preferences. In addition I hoped to be able to follow the monitors to determine how far they travel in their search for food. My goals were overambitious, however, and in the event I was fortunate to see a specimen at all. Every morning I would walk through the desert looking for footprints and examining burrows. The Caspian monitor can run at up to 12.5 miles (20km) per hour over short distances and wastes no time in its effort to get away from people. In addition its wary disposition and cryptic colouration made it unlikely that I would be able to make any direct observations of the animals. Luckily the frequent rain and soft sand of the Kara-Kum made following spoor very easy, because almost every night the rain would wash away all the old tail and foot prints. Varanus griseus caspius is easy to track in this way because it is by far the largest lizard in this part of Asia. Adults can grow as long as 5 feet (150cm) from the snout to the tip of the tail and weigh over 11lbs. (5kg). The impression left by its feet and tail are very distinctive when it is walking, but when disturbed it runs so quickly that only sporadic depressions in the sand are left behind. In the first two weeks I found evidence of two monitor lizards in the flat areas between the sand dunes. In both cases the marks were at the entrances of burrows. They seemed to indicate that the lizards had come out of the burrows and sprawled on the sand (leaving perfect impressions of claws and belly scales) before retreating underground again. In neither case had they wandered more than 6 feet (2 metres) from the burrows, the larger animal had rested with only its head and the first third of its body outside. I selected one of the burrows and spend the next five days waiting for the lizard to emerge. To my despair it remained underground. The impression of its belly scales appeared just inside the burrow on several occasions, so although it was definitely at home it had no inclination to leave. This was not the sort of behaviour I had expected from a gregarious, carnivorous lizard. However it was very early in the year, temperatures were not very high and there was frequent rainfall. As stated in the previous article, the Kara-Kum desert gets very cold in the winter and extremely hot in the summer. The Caspian monitor does not emerge from hibernation as early as its smaller cousins, because its greater bulk requires more heat to get it started. Perhaps these lizards were only just beginning to emerge from their winter retreats. With this in mind we opened the second burrow. Digging with our hands we were able to reveal a shaft 3 feet (1 metre deep) and at least 6 feet (2 metres) long. The lizard was even further inside so we abandoned the excavation and returned to camp. I wondered whether I would see any monitors on this trip apart from the residents at Moscow Zoo. That evening I was presented with a large cotton sack that hissed and heaved like a soul in torment. I open it with great apprehension, half expecting to find an angry levantine viper inside. To my delight it contained a young adult Caspian monitor, caught while it lay outside its burrow less than a kilometre from where we had been digging. This lizard measured 35.5 inches (90cm) in total, but weighed only 20 ounces (630 grammes). It was healthy but its stomach was clearly empty. I kept it for four days in the hope that it would produce some evidence of its last meal, but to no avail. This monitor was released close to where it had been caught. Because it had been subjected to so much stress I decided it would be pointless to follow it. This was to be the only monitor lizard I saw in Kara-Kum.

I continued to search the desert every day, and travelled over 110 miles (175 km) of asphalt road in the hope of finding a monitor attracted by the hot surface, but with no success. One morning I woke up early and set off through the desert determined to find this elusive animal. I had soon come to feel at home in this beautiful desert and spent several hours wondering happily from one of nature's miracles to another. As the temperature rose I took shade under a large saxaul bush and watched a handsome woodpecker fetching food for its extraordinarily noisy chicks. I wondered why every predator for miles around wasn't attracted by the clamourous chatter and promptly fell asleep. When I woke up the sun was overhead, so I decided to go back for some breakfast. I stood up and looked around to check my bearings, and it was several minutes before I was able to admit to myself that I didn't know what direction to go in. Before we had even arrived in Repetek Victor had expressed surprise that I hadn't brought a compass.

"I don't need one Victor, I'm from the Pennines".

He was not impressed. "If you get lost, when we find you you will be...(consulted the dictionary)...mummified".

I had taken no notice of this warning, and now it was time to regret it. As I walked around in large circles, hoping to pick up my footprints and follow them home, I began to consider seriously the prospect of mummification. Perhaps I would lie undiscovered in the desert for millenia before being unearthed and deposited in a museum. This was quite an amusing thought at first, but after an hour of concentric wandering I was more lost than before, if that is possible, and I began to panic. Two directions seemed likely, but unfortunately they lay opposite to each other. I set off in a straight line, hoping for the best. As I walked I realised why the term "desert" was so apt. If I was walking in the wrong direction I would not meet with humanity for many hundreds of miles. For us the deserts are desolate, inhospitable wastelands; their adeptness at deterring human settlers has resulted in them remaining the most undamaged regions of the earth. Mankind will only venture into such areas if the pickings are very rich indeed. Oil and gold are bait for many, for me it had been an evil-tempered reptile. It was with inexpressible joy that I finally reached the railway track, and followed it for 2 miles (3 km) back to Repetek. I had been lost for less than four hours, but I have never ventured anywhere without a compass since.

The day before we left for Moscow I found the track of a large (over 3 feet (1m)) monitor lizard. It had travelled over the crests of the sand dunes, going directly from one bush to another. After I had followed it for almost a kilometre the trail suddenly stopped. Perhaps the lizard had seen me and decided to make itself scarce. Of course such slight observations as these prove nothing in themselves, but they seem to indicate that the Caspian monitor does not wake up from hibernation and launch itself into a frenzy of feeding and mating. The fact that no fecal remains were found anywhere seems to indicate that the monitors do not begin to feed immediately, probably for the same reason. Speed of digestion is dependant on temperature, so a meal eaten on a warm day would putrefy in the stomach if the following days were cooler. Emergence is perhaps more gradual, and the serious commitment of leaving the safety of a deep, warm burrow is not taken until the spring is well underway.

I am very grateful to Moscow Zoo, Victor Makeyev and Anatoli Bojanski of the Soviet Institute of Nature Conservation, Suchan Veyisov of Repetek Reserve, Ron Marlow of Las Vegas, Nevada and the people of Turkmenistan for making this trip possible and for many acts of kindness.

 
 

 

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